Welcome to ViDa, the Fatigue Damage Calculator.

Fatigue and Fracture Mechanics calculations can be a very laborious task without a powerful software like ViDa, mainly when we need to calculate the accumulated damage or the remaining life of a structure or equipment which work under complex loading. In these cases, all we really wish is just specify the material, the applied stresses or strains and the appropriate stress concentration factor, and let the computer do (fast and accurately!) the dog work.

However, most powerful computational tools are written by software-oriented people: their terminology is normally so strange, not to mention how non-intuitive most of the user interfaces are, that you first have to learn how they internally work before being able to reliably perform even the most simple calculation. But ViDa is different. It has been developed by fatigue engineers to satisfy our design needs. Having a basic fatigue training, anyone can learn how to use its basic features in a glance. Take the one minute challenge! See how fast you can make a full calculation of fatigue damage with ViDa!

ViDa Main Features

ViDa at a Glance

ViDa is a powerful software for calculating the fatigue damage caused by complex loading. It includes all the traditional fatigue design methods, and introduces a series of improvements to enhance the speed and the accuracy of the numerical results, e.g.:

- Calculates the Fatigue Damage by the SN, eN and the da/dN Methods

- Plots the Correct Elastoplastic Hysteresis Loops calculated by the eN Method

- Solves the Neuber System for Stress Concentration

- Rainflow Counts and Racetrack Filters Complex Loading Histories

- Predicts the Uni and Bidimensional Growth of Fatigue Cracks, Including Retardation Effects

- Calculates Kt, q, KI and Other Constants Required by the Various Design Methods

- Automatically Adjusts Experimental Curves

- Has Friendly and Expandable Data Banks of Materials Properties, Stress Intensity Factors, and More!

This is a quick step-by-step tutorial that'll show you how to work with ViDa. Even if you're not a fast typist you'll take close to the minute to make your first calculation.

You’ve applied 100,000 cycles at 10 Hz of a pulsating 200 MPa stress on a specimen. We want to calculate the damage done to the specimen (0 being no damage and 1 being failure) and its remaining life in days (considering that the same rate of loading will be applied).

Are you ready? Check your clock, off we go!

1. In the Main Window, click on the cell right below ‘Alternate’ in the Loading Window. Type ‘100’. Press the right arrow key (‘->’) and type ‘100’ below the ‘Mean’ heading (the load is pulsating, therefore it has equal alternate and mean components). Now press the right arrow key (‘->’) and type ‘200000’ (meaning 200000 ½ cycles, equal to 100000 cycles). We are on the first of three steps.

2. Click on the box next to ‘Loading Time’ and type ‘10000’ (which is the duration in seconds of your loading history). Also check if the ‘Table’ option (above the Loading Window) is set for Stress(MPa).

3. Select Life | SN Method… from the menu. The SN Method window will appear. Check if the stress concentration factor Kt (on the bottom of the window) is set to 1. Click on the OK Button.

You’re done ! The damage and remaining life time are almost instantly displayed on the 2 bottom rows of the Loading Window as predicted by the Soderberg, the Goodman, the Gerber and even by a custom model!

How long did that take you? Even if you didn't break the one minute barrier first time around, consider this: you have just completed a full SN Method fatigue life calculation, all in about a minute! Now that wasn't hard was it?

In addition to typing the loading history, with ViDa you can import files from other software. It is possible to load comma separated value files (e.g. generated from the Instron’s Wavemaker software), previously saved Alternate/Mean or Peak/Valley files or even experimentally generated files by the Kyowa RHS-500A histogrammer.

1. On the Main Window, choose the File | Open command. A standard load file window will appear.

2. Click on the complex.alt file and press OK.

Done ! The Datasheet is now loaded with Alternate and Mean components of your loading history. These values represent stresses since the Table Option is set to ‘Stress’ (refer to the Tools | Options command to define if these stress values are in MPa or ksi). Now you can proceed to calculate life in the same way you did on the previous example.

Note also that you can view these Alternate/Mean components as a sequence of Peaks and Valleys by clicking on Peak/Valley in the Sequencing Option. You can also add or delete rows by using the Edit menu. Refer to the Edit menu for more information on data handling in the Loading Window.

ViDa has a complete Materials Database with stress-strain curves, SN, eN and da/dN data and many other properties of over 1500 materials. This database can be expanded by the user with no storage limits and all the materials can be searched by user defined criteria (e.g. searching for Alumina with Su between 400 and 500 MPa and sorting by their price). The next example will show you how to choose the material you’re working with.

1. From the Main Window, choose the Data | Material command. The Material Window will appear with the properties of the current material.

2. Choose the File | Open command. A list with all the materials in the database will appear.

3. Click on the name of the desired material.

It’s done. All the stored properties for that material will appear in the Material Window. Even experimentally measured points for this material (if any) will be loaded and available through the Experimental Points tab.

If you want you can change some of the properties, but you’ll need to use the File | Save command in order to be able to use these changes in the calculations. Note that some values are written in red in the Material Window. The red color denotes properties that were calculated/estimated from others, without having been directly measured. This color can be toggled by pressing the space bar on the desired value.

When you return to the Main Window by using the File | Exit command the name of the selected material will be displayed in the Material field and any further calculations will use its properties.

ViDa calculates the damage associated to the loading history for welded structures. This calculation is independent of the current Material since it depends only on the Weld Joint class.

1. From the Main Window, click on the Life | Welded Structures command. The Calculate Life of Welded Structures window will appear.

2. Click on the drawing of the desired weld joint. Its class and description will be shown on the bottom of the window, and press OK.

The damage and remaining life time are almost instantly displayed on the 2 bottom rows of the Loading Window. Also, Damage x Event and Accumulated Damage x Event graphs are plotted to better display the results.

To achieve reliable results when calculating fatigue damage under complex loading by the eN strain-life method, it is necessary to draw the correct elastoplastic hysteresis loops which act at the critical notch root.

1. In the Main Window, make sure that the Extended Modeling option is chosen using the Tools | Options command. This option is required to let ViDa calculate and plot hysteresis loops.

2. Choose the Life | eN Method command, and the Calculate Life (eN) window will appear.

3. Turn on the Calculate Hysteresis Loops option and check if the Loop Corrections option is checked as well.

4. Press the OK button.

The hysteresis loops for the loading history are calculated and plotted. The damage and remaining life time are almost instantly displayed on the 2 bottom rows of the Loading Window. Also, Damage x Event and Accumulated Damage x Event graphs are plotted to better display the results

To quantify fatigue damage in cracked structures, ViDa calculates crack growth using any da/dN equation specified by the user, recognizing retardation and even crack arrest effects.

1. From the Main Window choose the Life | Crack Growth command, and the Crack Growth (da/dN) window will appear.

2. Type the initial crack size and the specimen width.

3. Choose which da/dN equations you want to use in the calculations and press the OK button.

The total and average crack growth are almost instantly displayed on the 2 bottom rows of the Loading Window.

Surface cracks grow bidimensionally, i.e, both sideways and in depth. Certainly we cannot rely in pure unidimensional crack growth calculations. ViDa handles these bidimensional cracks and calculates crack growth in both directions, considering the changes in crack shape and retardation and crack arrest effects.

1. In the Main Window, make sure that the Extended Modeling option is chosen using the Tools | Options command. This option is required to let ViDa calculate bidimensional crack growth.

2. From the Main Window choose the Life | Bidimensional Crack Growth command, and the Bidimensional Crack Growth (da/dN and dc/dN) window will appear.

3. Choose the type of the crack in your specimen among (Semi-)Elliptic, Corner, Internal crack or even surface cracks on a cylinder wall under pressure.

4. Type the initial crack size dimensions a and c and the specimen width and its other dimensions.

5. Choose which da/dN equations you want to use in the calculations and press the OK button.

The total and average crack growth in both directions are almost instantly displayed on the 2 bottom rows of the Loading Window.

ViDa still has many other features: Rainflow counters, Tridimensional Stress handling, Rosettes, Stress Concentration Factor tables, and much more! To know more about ViDa, refer to ‘Working with ViDa Windows’ (see the Contents).

It is quick and easy to install ViDa in your computer. The ViDa CD-ROM features autorun and a setup wizard, making the installation process easier than ever.

Before You Begin

Running ViDa Setup

Installing ViDa

Viewing the Book "Fatigue Design under Complex Loading"

Registering ViDa

ViDa must be registered to become fully functional. If not registered, ViDa expires after 21 days.

Read the REGISTER.TXT file for more information on registering.

It is fast and easy to make calculations of fatigue damage with ViDa. ViDa has been developed by fatigue engineers to satisfy our design needs. Having a basic fatigue training, anyone can learn how to use its basic features in a glance.

Main Window

Handling all ViDa Graphs

Standard Open/Save File Window

Open CSV/Excel File Window

Material Window

Equations Database Window

Calculate Life (SN) Extended Window

Calculate Life of Welded Structures Window

Calculate Life (eN) Extended Window

Crack Growth (da/dN) Extended Window

Bidimensional Crack Growth (da/dN and dc/dN) Window

Calculation Logbook Window

Calculate Equivalent Stress Window

Smart Calculator Window

Options Window

Multimedia Window

Tip of the Day Window

The ViDa Main Window is where the user inputs the loading history (in the Loading Windows) and where the calculation results and plots are shown.

Main Toolbar of the ViDa Main Window, with buttons for the most common commands. To see the ToolTip of each button, just point at it with the mouse and wait for 2 seconds.

Toolbar with buttons for editing the current Loading Window. You can, for instance, Add or Delete one or more rows from the Loading Window. This Toolbar has essentially the same functionality as the Edit menu. To see the ToolTip of each button, just point at it with the mouse and wait for 2 seconds. You can hide this toolbar using the View menu.

Toolbar with shortcuts for the Material Window, Equation Window, and the Find Material and Browse Material Windows. This toolbar also contains a list with all available Materials (see below). To see the ToolTip of each button, just point at it with the mouse and wait for 2 seconds. You can hide this toolbar using the View menu.

Name of the material that will be used in the calculations (except for welded structures, which depend only on the IIW weld class). To change the material, use the Data | Material command or just click on the list box to change it.

Shows a Progress bar on how long it takes to perform a calculation. To stop a calculation in progress just press ESC.

One of the windows from the Main Window containing the loadings for each event, which can be either typed or loaded from a file. The first column shows the number of the event (each event can consist of many cycles). When the Alternate/Mean option is chosen at the Sequencing Option, the next 3 columns show the alternate and mean components of the loading and the number of ½ cycles that it is applied. If the Peak/Valley option is chosen at the Sequencing Option then these 3 columns are replaced by a single one containing the peaks and valleys of the loading.

After the calculations, the table also shows the damage (or crack growth) associated with each model. The 2 bottom rows contain the total damage and the residual life of the specimen (considering that the loading history continues to be applied on the specimen at the same rate defined in ‘Loading Time’). For crack growth calculations, the 2 bottom rows show instead the average da/dN and the total crack growth.

In order to edit the datasheet, just click on the desired cell and start typing. Other keyboard commands are:

[Enter - move down one cell] [Arrows - move along cells] [Ctrl+Arrows - jumps to the beginning or end of table] [Shift+Arrows - selects group of cells, for copying, etc.] [Ctrl+dragging the mouse - copies current cell value to all your selection] [Shift+Delete - deletes the selected rows] [Shift+Ins - inserts rows].

Option that defines if the values from the Loading Window represent stresses (in MPa or ksi) or strains (in microstrains).

Defines the data format from the Loading Window: either alternate/mean components or peak/valley counts. The loadings in the Loading Window are automatically converted from one to the other format.

Duration in seconds of ALL events in the Loading Window. It is used in the residual life estimate calculation.

Amplitude filter that can be automatically used when calculating Rainflow or Sequential Rainflow of a Peak/Valley history. Note that you need to enter its value prior to the Rainflow calculation. You can also Filter the history by using the Edit | Filter command. Set the Filter to zero in order not to filter the loading datasheet.

Plots the loading history from the datasheet. To redraw it, right-click with the mouse and select Redraw. You can also paste almost any previous data copied in Windows. For instance, you can select a group of cells in Excel, copy them, right-click on this graph and select Paste. You can also copy the contents of the graph in order to paste in almost any other application. To expand or shrink the graph, just double-click on it. This graph is shown only if the Show Loading Graph option is checked on the Options window.

Plots a 3D bar-chart of a loaded bidimensional histogram. Bidimensional histograms are loaded by opening a CSV (*.csv) or Excel (*.xls) file and turning on both the Histogram and the Mean Interval options. To expand or shrink the graph, just double-click on it. This graph is shown only if the Show Loading Histogram Graph option is checked on the Options window.

For the SN, IIW and eN Methods shows the damage, and for the da/dN Method the crack growth associated with each event. To expand or shrink the graph, just double-click on it.

For the SN, IIW and eN Methods shows the accumulated damage, whereas for the da/dN shows the total crack growth (since the first event) after each event. For Bidimensional Crack Growth calculations, this graph shows one of the several plots that can be chosen by the user. To expand or shrink the graph, just double-click on it.

Shows the elastoplastic hysteresis loops calculated by the eN Method, or one of the several plots that can be chosen by the user in the Bidimensional Crack Growth window. To expand or shrink the graph, just double-click on it. This graph is shown only if the Show Hysteresis Loops Graph option is checked on the Options window.

Creates a new Loading Window for entering a new loading history.

Opens a loading file. It can be:

Closes the current window. It is the same as clicking on the close button on the title bar of each window (the ‘X’ mark on the top right of any window).

Saves the loading history (*.alt or *.pic) to a file.

Saves the loading history (*.alt or *.pic) as a new file.

Saves ALL open windows to their respective files.

Prints the current Loading Window Datasheet.

Prints the current Loading Window Datasheet.

Saves the loading history (*.alt or *.pic) as a CSV (Comma Separated Values, *.csv) file.

Opens one of the 4 most recent loading files that you’ve been working on. A list of these 4 files are shown on the menu, will their full path.

Asks if you want to save your changes from all modified Loading Windows and exits ViDa.

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Copies to the Clipboard and clears the values of a group of cells from the Loading Window. The cells to be cut are defined by the highlighted cells in the table. To highlight them, just drag the mouse while pressing the left button, or press the SHIFT key while using the keyboard arrows. You can Paste these values, for instance, on an Excel worksheet.

Copies to the Clipboard the values of a group of cells from the Loading Window. The cells to be copied are defined by the highlighted cells in the table. To highlight them, just drag the mouse while pressing the left button, or press the SHIFT key while using the keyboard arrows. You can Paste these values, for instance, on an Excel worksheet.

Pastes the contents of the Clipboard on a group of cells of the Loading Window. The cells where the values will be pasted are defined by the highlighted cells in the table. To highlight them, just drag the mouse while pressing the left button, or press the SHIFT key while using the keyboard arrows. If the size of the copied selection was greater than the current selected cells, than only some of the Clipboard data is pasted. On the other hand, if only one cell is selected, then ALL Clipboard values are pasted, filling this cell and the ones to the right and below it. In this case, if the pasted values reach the bottom of the table, new rows are added accordingly to fit ALL the Clipboard data. These pasted values can be, for instance, cells copied from an Excel worksheet.

Inserts new rows on the Loading Window and pastes the contents of the Clipboard on them. The rows are inserted above the first selected cell on the table. These pasted values can be, for instance, cells copied from an Excel worksheet.

Deletes one or more rows from the Loading Window. The rows to be deleted are defined by the highlighted cells in the table. To highlight them, just drag the mouse while pressing the left button.

Inserts one or more rows to the Loading Window. The number of rows to be added is defined by the highlighted cells in the table. To highlight them, just drag the mouse while pressing the left button.

Copies a group of rows of the Loading Window as many times as desired. Use this command to enter repetitive blocks in your history. First select the rows you want to copy by dragging the mouse on them while clicking the left button. Then click on this command and enter the number of times you want to copy this block. The copied blocks will be inserted below the last selected row.

Sets the value of a group of cells of the Loading Window. First select the rows you want to set by dragging the mouse on them while clicking the left button. Then click on this command and enter the value you want to set for them.

Deletes all rows and data from the current Loading Window.

Asks the user to enter the number of rows of the current Loading Window. If the users enter a smaller number of rows than the current one, the corresponding rows are deleted. If it’s greater, the extra rows are added on the bottom of the table.

Filters a peak/valley or alternate/mean history from the Loading Window within a fixed amplitude, previously defined in the Filter text box on the Loading Window.

Checks the coherence of a peak/valley history from the Loading Window, eliminating the incoherent events.

Converts ALL the values of the Alternate and Mean (or Peak/Valley) columns of the Loading Window from MPa (mega Pascals) to kpsi (kilo pounds per square inch) by multiplying them by 0.145. Note that this command only changes numerically the values of the Loading Window. To use English instead of SI units for the whole program, use the Tools | Options command.

Converts ALL the values of the Alternate and Mean (or Peak/Valley) columns of the Loading Window from kpsi (kilo pounds per square inch) to MPa (mega Pascals) by dividing them by 0.145. Note that this command only changes numerically the values of the Loading Window. To use SI instead of English units for the whole program, use the Tools | Options command.

Converts ALL the values of the Alternate and Mean columns of the Loading Window to a sequence of Maximum and Minimum values, where Alternate=(Maximum-Minimum)/2 and Mean=(Maximum+Minimum)/2.

Converts ALL the values of a Maximum and Minimum history of the Loading Window to a sequence of Alternate and Mean components, where Alternate=(Maximum-Minimum)/2 and Mean=(Maximum+Minimum)/2.

Multiplies ALL the values of the Alternate and Mean (or Peak/Valley) columns of the Loading Window by a constant value. An input window will ask the user to enter this constant value.

Adds a constant value to ALL the values of the Alternate and Mean (or Peak/Valley) columns of the Loading Window. An input window will ask the user to enter this constant value.

Shows/hides the Standard toolbar.

Shows/hides the Edit toolbar.

Shows/hides the Material toolbar.

Shows/hides the Status Bar.

Refreshes the active window, redrawing its graphs, tables, and other components.

Shows the Calculation Logbook window, which keeps track of all previous calculations storing the total damage and residual life of the specimen for each SN, IIW and eN calculation, or the average da/dN and the total crack growth for each crack growth calculation. By filling out the ‘Calculation Title‘ field in the calculation windows it is possible to easily compare the results of different calculations in the Calculation Logbook window. This command has the same functionality as the Life | Logbook command.

Shows the Options window, where the user can set the ViDa general options regarding Editing of the Loading histories, the Modeling option used for all calculations (Extended or Simplified), the Units used (SI or English) and the idiom used on the user interface (among English, Portuguese, French, German, Italian, Spanish, and more). This command has the same functionality as the Tools | Options command.

Goes to the Material window to select a different material for the calculations.

Goes to the Equation Database window, where you can work with:

Goes to the Find Material window, where the user can search for materials by their type (steels, alumina, etc.) or by any property ranges (e.g. materials with Su between 600 and 800 MPa) or combinations of them. You can also sort the matching materials by any property.

Goes to the Browse Material window, where the user can browse all materials from the database, showing all their properties. You can rearrange the columns by dragging the column title with the mouse and dropping it over the desired position. ViDa automatically sorts the table by the first column, so if you want to order the materials e.g. by their Su, just drag and drop it on the first column. You can also resize the columns, and all your layout changes are saved. So, just customize your table, start browsing, and double-click on the Materials table on the name of the material you want to load to the Material window.

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Calculates the Alternate and Mean components of a Peak/Valley history using a Rainflow counter and the amplitude Filter value.

Calculates the Alternate and Mean components of a Peak/Valley history using a Sequential Rainflow counter and the amplitude Filter value. The Sequential Rainflow is a variation of the Rainflow that preserves as much as possible the loading order, which is very useful with the eN method and crack growth calculations.

Goes to the Calculate Life (SN) window for damage calculation using the current material and Loading Window load values.

Goes to the IIW window for damage calculation of welded structures using the current Loading Window values. Note that the material properties will not be used in this calculation since it is sufficient to know the class of the weld.

Goes to the Calculate Life (eN) window for damage calculation using the current material and Loading Window load values.

Goes to the da/dN Method window for unidimensional crack growth calculation using the current material and Loading Window values.

Goes to the Bidimensional Crack Growth window for (elliptical) crack growth calculation using the current material and Loading Window values.

Shows the Calculation Logbook window, which keeps track of all previous calculations storing the total damage and residual life of the specimen for each SN, IIW and eN calculation, or the average da/dN and the total crack growth for each crack growth calculation. By filling out the ‘Calculation Title‘ field in the calculation windows it is possible to easily compare the results of different calculations in the Calculation Logbook window.

Goes to the Rosette and 3D Equivalent Stress window for converting 3D loadings or Rosette measurements into 1D components using Mises or Tresca criteria.

Goes to the Calculate Stress Concentration Factor (Kt) window, where Kt and also the notch sensitivity q (for steels or alumina) can be calculated for typical notched and filleted bars and shafts, given its dimensions.

Goes to the Calculate Notch Sensitivity (q) for Steels and Alumina window, where the notch sensitivity can be calculated for steels or alumina given Su and the notch radius.

Shows the Smart Calculator window, where the user can use an alphanumeric calculator to compute any formula using the material properties and user-defined variables. Some basic Mechanics of Solids equations are also embedded in the calculator and computed results can be used to multiply the loadings in the Loading Window.

Shows the Options window, where the user can set the ViDa general options regarding Editing of the Loading histories, the Modeling option used for all calculations (Extended or Simplified), the Units used (SI or English) and the idiom used on the user interface (among English, Portuguese, French, German, Italian, Spanish, and more).

Loads the ViDa Help file and shows its Contents.

Loads the ViDa Help file and shows its Search engine.

Loads the Multimedia window, with links to the Textbook "Fatigue Design under Complex Loading", Published Papers, and video/animations.

Loads the ViDa Registration window. This window shows the Software Code associated to your computer, which you’ll need to inform in order to receive the Liberation Key. After receiving your key, you should type in the Liberation Key, your Name, and click ‘Register’. ViDa becomes fully functional after registering.

Loads the Tip of the Day window, which shows tips on working with ViDa. This window is loaded every time you run ViDa if the Show Tips at Startup option is selected in the Options window.

Shows the About window with the credits and version of the program.

Zoom

Log-Log

Thin Lines

Engineering

Define Life

Define R

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Copy

Paste

Redraw

Save

Print

Lets the user set the minimum and maximum values of the y-axis of the graph or a range of points to be plotted. After setting the Zoom, a check mark is placed on the Pop-Up menu. To return the Zoom settings to the original values, just click again on this command to uncheck it.

If this option is checked, the graph is plotted in Log-Log format. Uncheck it to plot in Linear-Linear format.

Toggles the line thickness of the Hysteresis Loops / Elliptic Cracks graph between thick and thin. Setting thin lines is especially useful when too many hysteresis loops are plotted in the same graph.

Plots the Engineering (instead of True) stress-strain curves in the Hardening Curve Graph of the Material window. If you uncheck this option, the True stress-strain curve is plotted instead.

Redraws the SaSm diagram of the SN Method window for a user defined life (in number of cycles) for reference purpose. The default life for plotting the SaSm diagram is 1,000,000 cycles.

Plots the da/dN equation shown in the da/dN Formula field for different values of R=Kmin/Kmax. The user is asked to input the range of R values to be considered and the number of curves to be plotted. This command is useful to visualize the influence of R (and Kmin and Kmax) in the da/dN equations that include these variables.

Copies ALL points from the graph to the Clipboard. You can then paste it to another graph, paste into any other application, or even paste it directly to an Excel worksheet. If you paste it to an imaging software (like Paint), you’ll be get the picture image of the graph.

Pastes the data from the Clipboard into the current graph. You can paste a group of cells copied from any ViDa Loading window or from an Excel worksheet. If more than 1 column was copied, then the graph pairs consecutive columns to plot one against another. So, if you paste 5 columns into the graph, columns 1 and 2 will determine a set of points (coordinates X and Y respectively), 3 and 4 will form another, and column 5 will be ignored (since it can’t be paired). If you paste only 1 column, its values are plotted in the Y axis (and the X axis will contain the row number of each point).

Redraws the graph updating any changes from the user. Tip: for the da/dN graph in the Crack Growth window, you can easily tune in the coefficients of the da/dN Formula by interactively editing the Variables Table and using this Redraw command until the curve is visually compatible with the Paris and Elber curves in the da/dN graph.

Saves the graph data as a Comma Separated Value (CSV). The first row contains the legend titles of each set in the graph and the following rows contain the respective data for each curve.

Prints the graph.

This is the standard interface window for all Open and Save File commands from ViDa.

Name of the file to be read.

Files found in the current directory (defined in ‘Folders’) of the extension chosen in ‘List files of type’. Just double-click on the desired file to choose it.

List with the desired file extensions.

Shows the current directory.

Confirms loading/saving the file.

Cancels loading/saving and returns to the previous window.

This window shows the fields from the chosen comma separated value (CSV) file or from an Excel file (*.xls), chosen from a Standard Load File window. The user is then asked to choose which field he wants to load to the Loading Window and allows him to enter an optional conversion factor to multiply these values. You can also Amplitude-Filter these converted values, and even choose to load just a histogram of the file, useful for very large loading histories.

Fields from the chosen comma separated value (CSV) or Excel (*.xls) file. Just click on the desired field and press OK to load it in the Loading Window.

Optional conversion factor to multiply the loaded values. For instance if your CSV field contains forces and you know the cross sectional area, you can type its inverse value in the Conversion Factor and then obtain stresses in your Loading Window (be careful with the units!).

Optional amplitude filter that can be used to filter the loading history. Useful for files with long histories.

Discretization interval used on the Histogram of the Alternate components of the loading history being read.

Discretization interval used on the Histogram of the Mean components of the loading history being read. If this option is checked, a bidimensional histogram counting is performed on the Alternate and Mean components. If not checked, all Mean components are set to zero, and only the Alternate components are evaluated.

Reads the selected field on the Fields list and returns to the Main Window.

Cancels the loading of the file and returns to the Main Window.

In the Material window it is possible to manipulate the Materials database, adding, deleting, changing or just selecting a specific material. You can alter the material properties by clicking on the respective field and entering the new data. Note that this new value will only be effective after you save it using the Material | Save command.

You can also store experimental points for the currently selected material. SN, eN and da/dN (Paris or Elber) curves can be automatically fitted to the experimental points, and the calculated properties data can be used in future life calculations.

Values in black represent measured properties, while the values in red reflect estimated properties (which are less reliable). To toggle the black/red colors, press the space bar while typing on the desired field (don’t forget to save the changes after).

Name and comments to tell apart similar materials (each material name+comment must be unique).

Material type (steel, aluminum, etc.).

Sequencing code for the material (automatically administered by ViDa).

Reference source for this material data.

Chemical composition of the material.

Consists of 2 fields: (i) the mechanical treatment applied to the material and (ii) the grain direction resulting from the rolling direction (L = longitudinal, T = transversal, W = width).

Minimum and maximum market prices for this material.

Operating Temperature, in which the properties were measured.

Melting Temperature of the material.

Thermal Expansion Coefficient of the material.

Specific weight of the material.

Amount of energy absorbed by the Charpy specimen.

Poisson coefficient.

Young modulus (be careful with the units!).

Brinnell Hardness.

Ultimate Strength.

Yielding Strength.

Cyclical Yielding Strength (used in hysteresis loops).

True Ultimate Strength.

True Ultimate Elongation.

Reduction in cross sectional area after failure (in %).

Hardening exponents of the monotonic and cyclic curves (using Ramberg-Osgood equation).

Hardening coefficient of the monotonic curve (using Ramberg-Osgood equation).

Hardening coefficient of the cyclical curve (using Ramberg-Osgood equation).

Additional information about the material.

Shows (just for reference) a window with all the equations used by the Calculate | Estimate using Nominal Values command to estimate properties from Nominal Values. These estimates are used by the ViDa program to try to fill out all the material properties that have not been measured or are not available.

Shows the monotonic (tension test) and cyclic true hardening curves of the material. Note the change in color marking on the graph the values of Sy and Sy’. The graph is only updated after the property changes are saved. To expand or shrink the graph, just double-click on it.

Shows the estimated SN curve of the material (this plot ignores the values of the endurance limit modifiers ka, kb, kc, kd and ke). The graph is only updated after the property changes are saved. To expand or shrink the graph, just double-click on it.

Uncorrected Endurance Limit (set it to zero if you don’t want any elbow in the SN Curve).

Exponent of the SN Curve (N*S^b = c).

Coefficient of the SN Curve (N*S^b = c).

Location of the SN curve elbow.

Value of the b exponent of the SN Curve after the elbow (set belb=0 to ignore this option).

Loads the values of the parameters b and c of the SN curve N*S^b=c from the Experimental Points Window directly into the current window.

Calculates the constants of the SN Curve (N*S^b = c) by making it coincident with the elastic part of the eN Curve (defined by the eN Curve parameters Sigmaf’ and b). This estimate is based on the principle that both SN and eN methods should predict the same damage for high cycle calculations. After the calculation the estimated b and c values are color coded in red.

Activates the Calculate b and c for SN window that lets the user calculate the constants of the SN curve (N*S^b = c) from the material properties Su and Sf’. After the calculation the estimated b and c values are color coded in red.

Shows the eN curve of the material and also its elastic and plastic components separately. The SN curve is also plotted in order to make a comparison with the elastic component of the eN curve. The graph is only updated after the property changes are saved. To expand or shrink the graph, just double-click on it.

Elastic coefficient used in Coffin-Manson’s eN Curve equation (de/2 = Sigmaf’/E*(2N)^b+epsilonf’*(2N)^c).

Plastic coefficient used in Coffin-Manson’s eN Curve equation (de/2 = Sigmaf’/E*(2N)^b+epsilonf’*(2N)^c).

Elastic exponent used in Coffin-Manson’s eN Curve equation (de/2 = Sigmaf’/E*(2N)^b+epsilonf’*(2N)^c).

Plastic exponent used in Coffin-Manson’s eN Curve equation (de/2 = Sigmaf’/E*(2N)^b+epsilonf’*(2N)^c).

Loads the values of the parameters b, c, Sigmaf’ and epsilonf’ of the eN curve de/2 = Sigmaf’/E*(2N)^b+epsilonf’*(2N)^c from the Experimental Points tab directly into the current tab.

Shows the da/dN curves of the material using Paris and Elber laws. Note that the value of deltaKth substantially affects the Elber law curve. The graph is only updated after the property changes are saved. To expand or shrink the graph, just double-click on it.

Critical Stress Intensity Factor (fracture toughness).

Threshold Stress Intensity Factor (if deltaK < deltaKth the crack does not propagate).

Coefficient A used in Paris law (da/dN = A*deltaK^m).

Exponent m used in Paris law (da/dN = A*deltaK^m).

Coefficient A used in Elber law (da/dN = A*(deltaK-deltaKth)^m).

Exponent m used in Elber law (da/dN = A*(deltaK-deltaKth)^m).

Exponent p used in Walker law da/dN = A*(deltaK)^m / (1-R)^p and also in the Modified Walker law da/dN = A*(deltaK-deltaKth)^m / (1-R)^p.

Value of the critical CTOD (Crack Tip Opening Displacement).

Loads the values of the A and m coefficients of the Paris da/dN equation da/dN=A*deltaK^m from the Experimental Points tab in the Materials Database directly into the current window.

Calculates the constants of the Paris law (da/dN = A*dK^m) from the eN Curve parameters by using the assumption that crack growth is caused by the successive breaking of tiny eN specimens (see the Textbook "Fatigue Design under Complex Loading"). After the calculation the estimated A and m values are color coded in red.

Sets the constants of the Paris law (da/dN = A*dK^m) depending on the microstructure of the material. These values are tabulated referencing Rolfe-Barson rough estimates. After the calculation the estimated A and m values are color coded in red.

Loads the values of the A and m coefficients of the Elber da/dN equation da/dN=A*(deltaK-deltaKth)^m from the Experimental Points tab in the Materials Database directly into the current window.

Tables where the user can input experimental points.

Switches tab to the SN, eN or da/dN curve experimental points table.

Switches tab to the hardening curves experimental points table.

Log(S) x Log(N) curve graph, plotting the experimental points and/or the fitted curves from the calculated properties data. Note that the graph is only updated after you save the data using the File | Save command.

Log(e) x Log(N) curve graph, plotting the experimental points and/or the fitted curves from the calculated properties data. Note that the graph is only updated after you save the data using the File | Save command.

Log(da/dN) x Log(deltaK) curve graph, plotting the experimental points and/or the fitted curves from the calculated properties data. Note that the graph is only updated after you save the data using the File | Save command.

Stress-strain curve graph, plotting the experimental points and/or the fitted curves from the calculated properties data. Note that the graph is only updated after you save the data using the File | Save command.

Properties calculated from the curve fittings from the experimental points.

Fits the SN experimental data points (using a least squares method) for a Wohler equation (N*S^b = c). The b and c constants are calculated and the fitted curve is plotted on the SN graph. To use these calculated b and c in life calculations, you need to copy them to their respective field in the Fatigue and Fracture tab and use File | Save.

Fits the eN experimental data points (using a least squares method) for a Coffin-Manson equation. The 4 eN curve constants are calculated and the fitted curve is plotted on the eN graph (the Young modulus E comes from the monotonic data). Note that since there are 4 constants in the eN curve (instead of only 2) you need data with not only the number of reversions (2N) and the strain variation (de/2) but also with the corresponding stress variation dS/2. To use these calculated constants in life calculations, you need to copy them to their respective field in the Fatigue and Fracture tab and use the File | Save command.

Fits the da/dN experimental data points (using a least squares method) for the Elber law (da/dN = A*(deltaK-deltaKth)^m). The user then inputs the value of deltaKth that will be used in the curve fitting (the default value is the one from the Material window). The A and m constants are calculated and the fitted curve is plotted on the da/dN graph. To use these calculated A and m in life calculations, you need to copy them to their respective field in the Fatigue and Fracture tab and use the File | Save command.

Fits the hardening experimental data points (using a least squares method) for a Ramberg-Osgood equation. To use these calculated n, n', k and k' in life calculations, you need to copy them to their respective field in the General tab and use the File | Save command.

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Goes to the Open Material window, which shows a list of all available materials. Just click on the name of the desired material to load it.

Saves all the material properties to the database and updates all 7 graphs in the Material window. The black-red (measured-estimated properties) color coding is also saved in the database. It also saves the experimental points and calculated properties data for this material in the database. Note that you need to save the changed properties for them to become effective and available for further calculations.

Creates a new material in the database with all the current properties and experimental data, and updates the 7 graphs in the Material window. Note that each material must have an unique name, so you must change the Name field before saving as new.

Goes to the Find Material window, where the user can search for materials by their type (steels, alumina, etc.) or by any property ranges (e.g. materials with Su between 600 and 800 MPa) or combinations of them. You can also sort the matching materials by any property.

Goes to the Browse Material window, where the user can browse all materials from the database, showing all their properties. You can rearrange the columns by dragging the column title with the mouse and dropping it over the desired position. ViDa automatically sorts the table by the first column, so if you want to order the materials e.g. by their Su, just drag and drop it on the first column. You can also resize the columns, and all your layout changes are saved. So, just customize your table, start browsing, and double-click on the Materials table on the name of the material you want to load to the Material window.

Deletes the current material permanently from the database. The default material is then automatically loaded.

Exits the Material Window and returns to the Main Window. Note that you need to save the changed properties for them to become effective for further calculations.

Sets ALL the material properties to zero. Note that the changes are only effective after you click on File | Save or File | Save as New commands. Use the Edit | Clear All Properties command and then File | Save As New to create a new material from scratch.

Sets the estimated (color coded in red) material properties to zero. Note that the changes are only effective after you click on File | Save or File | Save as New commands. Use this command to discard the estimated (non reliable) properties, either to estimate them again by using the Edit | Estimate using Nominal Values command or to replace them with measured properties. Note that to change the color coding (black-red) you need to press the space bar on the desired property field.

Estimates the currently null material properties. To see the estimating formulas that ViDa uses click on the Estimates button. All estimated properties are color coded in red.

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Asks the user to enter the number of rows of the selected experimental data table (SN, eN or da/dN). If the users enter a smaller number of rows than the current one, the corresponding rows are deleted. If it’s greater, the extra rows are added on the bottom of the table.

Saves the selected experimental data table (SN, eN or da/dN) as a CSV (Comma Separated Values, *.csv) file.

Loads a Comma Separated Values (CSV) file into the selected experimental data table (SN, eN or da/dN). Note that ViDa ignores the first row of the CSV file (since it assumes that the first row contains the column titles) and the number and order of the columns in the file must be compatible with the respective table (2 columns for the SN or the da/dN tables and 3 columns for the eN table).

Converts the numerical values of all the 3 Experimental Points Tables from SI to English units (MPa -> ksi, MPa\/m -> ksi\/in, mm/cycle -> in/cycle). Note however that only the numerical values are changed, so if you want to perform calculations in English units you need to select the Tools | Options command from the Main Window, and choose English Units from the Units tab.

Converts the numerical values of all the 3 Experimental Points Tables from English to SI units (ksi -> MPa, ksi\/in -> MPa\/m, in/cycle -> mm/cycle). Note however that only the numerical values are changed, so if you want to perform calculations in SI units you need to select the Tools | Options command from the Main Window, and choose SI Units from the Units tab.

Shows a list of all materials in the database (or the ones that matched a query from the Find Material window). Just click on the desired material to load the data.

List of all materials in the database (or the ones that matched a query from the Find Material window). Just click on the desired material to load the data.

Total number of materials found in the materials database (or the ones that matched a query).

Cancels the material selection and returns to the Material window.

Lets the user search for materials by their type (steels, alumina, etc.) or by any property ranges (e.g. materials with Su between 600 and 800 MPa) or combinations of them. You can also sort the matching materials by any property. The results of your query are shown in the Open Material window.

Type of material to be searched (steels, alumina, etc.).

Choose here the properties that you want to set ranges in your query.

Set the minimum and maximum value of the corresponding material property to be used in your query.

Choose here the properties that you want to use to sort the results from your query.

Choose the sorting order (descending or ascending) of the results from your query.

Evaluates your query and show the results in the Open Material window.

Cancels your query and returns to the Material window.

Lets the user browse all materials from the database, showing all their properties. You can rearrange the columns by dragging the column title with the mouse and dropping it over the desired position. ViDa automatically sorts the table by the first column, so if you want to order the materials e.g. by their Su, just drag and drop it on the first column. You can also resize the columns, and all your layout changes are saved. So, just customize your table, start browsing, and double-click on the material you want to load.

Shows all available materials in the database. You can customize the table layout by dragging and dropping the columns, as well as resizing them. ViDa automatically sorts the table by its first column, and all your layout changes are automatically saved. To load a material to the Material window, just double-click on its name, or select it and press the OK button.

Shows more information on this window.

Updates the table to reflect your most recent changes in the Material database. You only need to use this button if you have made changes to the Material database in this session of ViDa.

Sets the column order and column widths of all properties to the default value used in ViDa. You can use this button if you made too many changes in the table layout and want to revert it back.

Changes the display mode so to group equal values into one larger cell.

Loads the selected material and returns to the Material window . Alternatively, you can just double-click on the Materials table on the name of the material you want to load.

Cancels the material selection and returns to the Material window.

Calculates the b and c constants of the SN curve (N*S^b = c) using the user data and returns to the Material window.

Values of 2 points of the SN curve to be interpolated. The default values are 1000 cycles for 0.9*Su and 1,000,000 cycles for Sf, but the user can change any of these values before pressing OK.

Calculates the b and c constants of the SN curve (N*S^b = c) using the user data and returns to the Material Window or to the SN Method Window.

Cancels the calculation and returns to the Material Window or to the SN Method Window.

Database of Kt, KI or da/dN equations that can be used in calculations. In this window you can add, delete or change data of a specific equation. You can alter the equations by clicking on the desired field and entering the new data. Note that this new data will only be effective after you save it.

Name of the equation (each equation name must be unique).

Sequencing code for the equations (automatically administered by ViDa).

Reference source for this equation.

Contains the equation itself. Click on the Equation Interpreter Help button to get more information about the equations syntax.

Shows (just for reference) a window with the equations syntax and all the material properties that can be literally used.

Additional information about the equation.

Name of the graphic file containing the selected equation (located in the directory Vida2002\Figures).

Deletes the selected equation permanently from the database.

Updates all the equation data from the current Tab to the database. Note that you need to use this command for the changes to become effective for further calculations.

Returns all unsaved equation data to its original values.

Edits the selected figure using the graphical software defined in the File Locations tab of the Options window.

Exits the Equations Database window and returns to the Main Window. Note that you need to update the changed equations for them to become effective for further calculations.

Calculates the damage and remaining life using the SN Method and the loading history from the Main Window. (The SN method is recommended only if the stress/strain history at the critical point – normally a notch root – is elastic). The user can input the specimen characteristics to determine the values of ka, kb, kc, kd and ke, the fatigue strength modifiers due to surface finish, size, loading, temperature and other effects, alter the material SN curve equation, calculate and input stress concentration factors, define user SaSm diagrams and many other options.

Some of the default data in this window comes from the Materials database and the rest is maintained from your last calculation. A simplified Calculate Life (SN) window (recommended for beginners) is also available by using the Tools | Options | Simplified command in the Main Window prior to calculating life.

After tuning the desired properties, just click on the OK button to return to the Main Window and perform the calculations.

Title of the calculation that is about to be performed. This is an optional field, useful to identify and compare results from different calculations in the Calculation Logbook Window.

ViDa considers 3 ways of obtaining the SN curve N*S^b=c:

(i) Automatic: calculates b and c from the pair of points (N,S) = (1000cycles, 0.9*Su) and (1,000,000cycles, Sf=ka*kb*kc*kd*ke*Sf’) for steels (for alumina the 1,000,000 cycles is switched to 500,000,000). For steels an elbow is placed in the SN curve at N=1,000,000.

(ii) b-Sf-Nf: determines the SN curve using the point (N,S) = (Nf, Sf=ka*kb*kc*kd*ke*Sf’) and the exponent b.

(iii) b-c-Nf: the SN curve is determined from the user supplied values of b, c and the elbow location Nf. Note that only in this option the Calculate b, c Button is enabled.

Exponent of the SN Curve (N*S^b = c).

Coefficient of the SN Curve (N*S^b = c).

Location of the elbow in the SN curve (there is no fatigue damage for N > Nf).

Goes to the Calculate b and c for SN Window, where the user can calculate the parameters b and c of the SN curve N*S^b=c.

Loads the values of the parameters b and c of the SN curve N*S^b=c from the Materials Database directly into the current window.

Loads the values of the parameters b and c of the SN curve N*S^b=c from the Experimental Points Window directly into the current window.

Option to consider the elbow in the SN curve, which defines no fatigue damage for stresses smaller than Sf=ka*kb*kc*kd*ke*Sf’ (or number of cycles greater than Nf). If this option is off then the elbow is ignored.

Value of the b exponent of the SN Curve after the elbow (set belb = 0 to ignore this option).

Surface finish of the specimen, used to automatically calculate the endurance limit modifying factor ka.

Main type of loading applied to the specimen, used to automatically calculate the endurance limit modifying factor kc.

Specimen cross-section diameter (or equivalent diameter), used to automatically calculate the endurance limit modifying factor kb.

Goes to the Calculate Effective Diameter Window, where the user can calculate the effective diameter of various cross section profiles under bending. This diameter is used to calculate the size factor kb (used to correct the fatigue endurance limit Sf’).

Ultimate strength of the current material, used to automatically calculate the endurance limit modifying factor ka. The default value of Su is loaded from the Materials Database, but it can be changed by the user.

Specimen operating temperature, used to automatically calculate the endurance limit modifying factor kd.

Uncorrected endurance limit of the material (alternate stress below which there is no fatigue damage).

Surface finish factor that modifies the endurance limit (a better surface finish increases the endurance limit).

Size factor that modifies the endurance limit (smaller specimens have greater endurance limit than larger ones).

Loading factor that modifies the endurance limit (depends on the main type of loading applied to the specimen).

Temperature factor that modifies the endurance limit (greater temperatures bring down Sf).

Miscellaneous factors that modify the endurance limit (e.g. corrosion). Be careful not to include the stress concentration factor Kt or Kf in the value of ke, since Kt and Kf are already taken care of in the stress calculation.

SN curve of the material, considering the endurance limit modifiers ka, kb, kc, kd and ke. The graph is updated after changes in its parameters only when the Graph | Redraw command is used. To expand or shrink the graph, just double-click on it.

Curve relating combinations of alternate (Sa) and mean stresses (Sm) that lead to a same life. This equation has the form (Sa/Sf)^m+(Sm/Sref)^n=1, Sf being the corrected endurance limit (Sf=ka*kb*kc*kd*ke*Sf’), and the user can define any values for m, n and Sref. In the Goodman curve for instance the values are m=n=1 and Sref is the ultimate strength Su.

Name of the user defined SaSm damage curve.

Alternate stress exponent m of the user defined SaSm damage curve (Sa/Sf)^m+(Sm/Sref)^n=1.

Mean stress exponent n of the user defined SaSm damage curve (Sa/Sf)^m+(Sm/Sref)^n=1.

Reference mean strength Sref of the user defined SaSm damage curve (Sa/Sf)^m+(Sm/Sref)^n=1. In general its value is chosen as Su or Sy.

Slope of the SaSm curve when the mean stress is negative. This slope is measured as a percentage of the Goodman curve slope. If 0% is chosen then the SaSm curve is flat for negative mean stresses. When this percentage is increased the user is valorizing the beneficial influence of compressive mean stresses (which can extend life).

Shows a help window with some basic explanations about the User Damage Curve.

Graph showing the damage curve relating alternate and mean stresses (Sa and Sm pairs that cause the same damage) for different models: Goodman, Gerber, Soderberg and the user defined damage curve. Since these curves can be plotted for any reference life in cycles, ViDa by default plot them for a life associated with the elbow of the SN curve (1,000,000 cycles for most steels). By clicking on the menu command Graph | Define Life for SaSm the user can change this default plotting value to see the damage curves for any desired life.

Option to apply the stress concentration factor on the mean stress (not only on the alternate component). Some theories suggest that the Kt value should only be applied to the alternate stress and ignored for the mean, so in this case just turn this option off.

Option to plot or not to plot the data calculated using the Soderberg damage curve. Since Soderberg is very conservative it calculates damages much greater than the other curves would predict, which makes difficult the visualization in the graphs. In this case just turn this option off and only the Goodman, Gerber and user damage curve results are plotted.

Initial damage value, before the loading history, using the Palmgreen-Miner rule.

Total damage value that characterizes failure of the specimen. The Palmgreen-Miner rule suggests a total damage value of 1 for the end of life, but other values can be chosen by the user.

Option that considers residual stresses in the SN life calculation. The program needs to draw hysteresis loops in order to consider residual stresses accurately, which increases the complexity of the calculations. The user can also enter an initial residual stress value.

Initial value of the residual stress on the specimen (use negative values for compressive residual stresses). Residual stresses are only considered in the life calculation if the Consider Residual Stresses Option is on.

Range of hysteresis loops that the user wants to plot for visualization purposes. This range doesn’t affect the calculations (the program needs to calculate ALL the hysteresis loops in order to consider residual stresses accurately). Note that residual stresses are only considered in the life calculation if the Consider Residual Stresses Option is on.

Resolution in number of points of each hysteresis loop, for calculation accuracy and plotting purposes. For calculation, 40 points is in general a good choice. If you’re plotting too many hysteresis loops you might have to reduce the number of plotting points for each loop.

Strain concentration theory used when considering stress concentration factors on hysteresis loops. Linear theory considers Ke=Kt (strain concentration Ke is equal to Kt), while Neuber theory uses Ke*Ks=Kt^2.

Stress concentration factor of the specimen (relating the nominal loading to the stresses at the notch root). Its value can also be calculated using the Calculate | Kt | Typical or Calculate | Kt | Stored commands.

Notch sensitivity factor, which is used to calculate the fatigue or effective stress concentration factor Kf=1+q*(Kt-1).

Goes to the Calculate Typical Stress Concentration Factor (Kt) Window, where the user can calculate the value of Kt for Notched/Filleted Bars or Shafts of any dimensions.

Goes to the Smart Calculator window, where the user can calculate the value of Kt using the equations from the Kt Equations Database (or any other equation defined by the user).

Goes to the Calculate Notch Sensitivity (q) for Steels and Alumina Window, where the user can calculate q for steels or alumina given the notch radius and Su.

Calculates the damage using the SN Method for the Loading Window loadings using the material properties and the chosen options, and goes back to the Main Window.

Cancels the SN Method calculation and goes back to the Main Window.

Calculates the damage and remaining life using the SN Method and the loading history from the Main Window. (The SN method is recommended only if the stress/strain history at the critical point – normally a notch root – is elastic). The user can input the specimen characteristics (such as surface finish or equivalent diameter to determine the values of ka, kb, kc, kd and ke), alter the material SN curve equation, calculate and input stress concentration factors and some other options.

Some of the default data in this window comes from the Materials database and the rest is maintained from your last calculation. Many more options are available in the extended Calculate Life (SN) window, which is available by using the Tools | Options command in the Main Window and choosing Extended in the Modeling tab, prior to calculating life.

After tuning the desired properties, just click on the OK button to return to the Main Window and perform the calculations.

To check information on the available commands, please refer to the correspondent extended window.

Calculates the effective diameter of different cross sectional profiles for bending. This diameter is used in the Calculate Life window for SN or eN methods to calculate the size factor kb (used to correct the fatigue endurance limit Sf’).

Click on the corresponding button and enter the profile dimensions to calculate the effective diameter and press the OK button to return to the previous window with the calculated value.

Drawings of the cross section profiles of the available bending effective diameter equations.

Calculated effective diameter under bending on each axis of the chosen cross section. To copy any of these values to the Effective Diameter field, click on the desired Axis field.

Shows the calculated effective diameter for the chosen cross section profile.

Returns to the previous window and copies the Calculated Diameter value to the Equivalent Diameter field in the previous window.

Returns to the previous window without carrying the Calculated Diameter value.

Calculates the stress concentration factor (Kt) for typical specimens. Clicking on the desired specimen category, 3 or 4 figures will appear on the screen. Enter the values of w (or D), d and r and click on the figure with the desired specimen type. ViDa will then calculate the value of Kt and plot the Kt equation that originated this calculation. The values of the notch sensitivity (q) and the effective stress concentration factor Kf=1+q*(Kt-1) are also displayed considering that the current material is a steel or an aluminum.

Press the OK button to go back to the previous window bringing and updating the calculated values of Kt and q (or Cancel to return without carrying these values).

Drawing of the available specimen types for that chosen specimen group. Just click on the desired drawing to see its Kt graph and calculate the values of Kt, q and Kf.

Graph showing the Kt values for a specific specimen type as a function of its dimensions.

Values of the dimensions of the specimen drawings, used to calculate Kt.

Value of r on the specimen drawings, used to calculate Kt, q and Kf.

Ultimate strength of the material, used to calculate q. The default value is loaded from the Materials Database, but it can be changed by the user.

Calculated values of Kt (stress concentration factor), q (notch sensitivity) and Kf (fatigue or effective stress concentration factor, Kf=1+q*(Kt-1)). These values are automatically calculated for the chosen specimen drawing using the variables values, r and Su. The value of q is calculated from r and Su and taking into account if the current material is a steel or an aluminum (for other types of material the steel values are used).

Returns to the previous window and copies the Calculated Kt value to the Kt field in the previous window. If the previous window is the Calculate Life (SN) window, then the value of q is also carried.

Returns to the previous window without carrying the Calculated Kt value.

You can calculate the stress concentration factor (Kt) from stored Kt equations in the database, just choose the desired equation name from a list. You can also set the variable values in the Variables Table by clicking on the desired cell, or edit the equation in the Formula box. ViDa automatically calculates the value of Kt for the chosen equation.

List of names of the available Kt equations from the Equations Database. Just click on the desired name to load its Formula.

Formula of the Kt equation loaded from the Equations Database through the Name list. The formula can also be edited by the user.

Adds the Kt equation present in the Kt Formula field to the Equations Database. The user will be asked to enter a name for this new equation.

Table containing variables that can be set by the user. To set a variable, just click on it and type its new value. If these variables are present in the Kt Formula then their values are used in the calculations.

Loads a previously saved Variables Table file (*.var) containing the values of all variables from the Variables Table.

Saves the values of the variables from the Variables Table to a Variables Table file (*.var).

Calculated value of Kt (stress concentration factor). This value is automatically calculated for the chosen equation using the Variables Table values.

Returns to the previous window and copies the Calculated Kt value to the Kt field in the previous window.

Returns to the previous window without carrying the Calculated Kt value.

Calculates the notch sensitivity (q). Type the value of the notch radius and ViDa will automatically calculate the value of q depending on your choice of material type in the Material option.

Press the OK button to go back to the previous window bringing and updating the calculated value of q (or Cancel to return without carrying this value).

Shows the notch sensitivity values as a function of the Notch Radius and Su.

Ultimate strength of the material, used to calculate q. The default value is loaded from the Materials Database, but it can be changed by the user.

Radius of the notch on the specimen, used to calculate q.

Option of material type for calculating q. Note that q doesn’t depend on Su for Alumina.

Calculated value of the Notch Sensitivity for steels or alumina given the Notch Radius and Su.

Returns to the Calculate Life (SN) window carrying the Calculated q value.

Returns to the previous window without carrying the Calculated q value.

Calculates the damage and remaining life of welded structures using the IIW (International Institute of Welding) Method and the loading history from the Main Window. The user can input the weld joint class (which is the stress range in MPa that leads to a 2,000,000 cycle life to that specific weld type), the exponent m from the IIW equation N(cycles)=2,000,000*([weld class]/[applied stress])^m, the number of cycles above which there is no fatigue damage, and even a reliability factor for the calculations.

This window also contains the weld joint class values for many typical weld joints. Just click on the drawing of the desired weld joint to load its class and description.

After tuning the desired properties, just click on the OK button to return to the Main Window and perform the calculations.

Title of the calculation that is about to be performed. This is an optional field, useful to identify and compare results from different calculations in the Calculation Logbook Window.

Exponent m from the International Institute of Welding (IIW) equation N(cycles)=2,000,000*([weld class]/[applied stress])^m. The default value of m is 3.0.

Number of cycles above which there is no fatigue damage for the Weld Joint. The default value of N is 5,000,000.

Initial damage value, before the loading history, using the Palmgreen-Miner rule.

Total damage value that characterizes failure of the weld. The Palmgreen-Miner rule suggests a total damage value of 1 for the end of life, but other values can be chosen by the user.

Class of the Weld Joint to be used in the life calculation according to the International Institute of Welding (IIW) data. The class is defined as the alternated stress applied to the specimen associated to a 2,000,000 cycles life for the weld. Click on the Weld Joint buttons to retrieve the class values of common Weld Joints.

Description of the chosen Weld Joint.

Buttons showing typical weld joints. Just click on each Weld Joint Button to load its class and description.

Calculates life for the chosen specimen and weld joint using the IIW Method for the Loading Window loadings and the chosen options, and goes back to the Main Window.

Calculates the damage and remaining life using the eN Method (recommended in the presence of plastic deformations at the critical point, normally a notch root) and the loading history from the Main Window. The user can input specimen characteristics (such as surface finish or equivalent diameter to determine the values of ka, kb, kc, kd and ke to alter the elastic component of the eN curve), alter the material eN curve equation, calculate and input stress concentration factors, choose to or not to calculate by following and plotting the hysteresis loops and many other options.

Some of the default data in this window comes from the Materials database and the rest is maintained from your last calculation. A simplified Calculate Life (eN) window (recommended for beginners) is also available by using the Tools | Options command in the Main Window and selecting Simplified in the Modeling tab, prior to calculating life.

After tuning the desired properties, just click on the OK button to return to the Main Window and perform the calculations.

Title of the calculation that is about to be performed. This is an optional field, useful to identify and compare results from different calculations in the Calculation Logbook Window.

Elastic coefficient from Coffin-Manson’s equation (de/2 = Sigmaf’/E*(2N)^b+epsilonf’*(2N)^c).

Plastic coefficient from Coffin-Manson’s equation (de/2 = Sigmaf’/E*(2N)^b+epsilonf’*(2N)^c).

Elastic exponent from Coffin-Manson’s equation (de/2 = Sigmaf’/E*(2N)^b+epsilonf’*(2N)^c).

Plastic exponent from Coffin-Manson’s equation (de/2 = Sigmaf’/E*(2N)^b+epsilonf’*(2N)^c).

Calculates the values of the parameters b, c, Sigmaf’ and epsilonf’ of the eN curve de/2 = Sigmaf’/E*(2N)^b+epsilonf’*(2N)^c by loading them from the Materials Database and also correcting the elastic exponent b using the value of Sf=ka*kb*kc*kd*ke*Sf’ (the same approach used in the SN Curve).

Loads the values of the parameters b, c, Sigmaf’ and epsilonf’ of the eN curve de/2 = Sigmaf’/E*(2N)^b+epsilonf’*(2N)^c from the Materials Database directly into the current window.

Loads the values of the parameters b, c, Sigmaf’ and epsilonf’ of the eN curve de/2 = Sigmaf’/E*(2N)^b+epsilonf’*(2N)^c from the Experimental Points tab directly into the current tab.

Option to consider the elbow of the SN curve (which defines no fatigue damage for stresses smaller than the corrected endurance limit Sf=ka*kb*kc*kd*ke*Sf’) in the elastic portion of the eN curve. If this option is off then the elbow is ignored.

Value of the b exponent of the SN Curve after the elbow (set belb = 0 to ignore this option).

Initial damage value, before the loading history, using the Palmgreen-Miner rule.

Total damage value that characterizes failure of the specimen. The Palmgreen-Miner rule suggests a total damage value of 1 for the end of life, but other values can be chosen by the user.

Surface finish of the specimen, used to automatically calculate the endurance limit modifying factor ka (the endurance limit from the SN method is used to correct the elastic component of the eN curve).

Main type of loading applied to the specimen, used to automatically calculate the endurance limit modifying factor kc (the endurance limit from the SN method is used to correct the elastic component of the eN curve).

Specimen cross-section diameter (or effective diameter), used to automatically calculate the endurance limit modifying factor kb (the endurance limit from the SN method is used to correct the elastic component of the eN curve).

Goes to the Calculate Effective Diameter Window, where the user can calculate the effective diameter of various cross section profiles under bending. This diameter is used to calculate the size factor kb (used to correct the fatigue endurance limit Sf’, affecting the elastic component of the eN curve).

Ultimate strength of the current material, used to automatically calculate the endurance limit modifying factor ka (the endurance limit from the SN method is used to correct the elastic component of the eN curve). The default value of Su is loaded from the Materials Database, but it can be changed by the user.

Specimen operating temperature, used to automatically calculate the endurance limit modifying factor kd (the endurance limit from the SN method is used to correct the elastic component of the eN curve).

Uncorrected endurance limit of the material (alternate stress below which there is no fatigue damage). Note that the endurance limit is a concept normally used in the SN method, but in ViDa it can also be used to correct the elastic component of the eN curve.

Surface finish factor that modifies the endurance limit (a better surface finish increases the endurance limit). Note that the endurance limit and its modifying factors are originally from the SN method, but in ViDa they can also be used to correct the elastic component of the eN curve.

Size factor that modifies the endurance limit (smaller specimens have greater endurance limit than larger ones). Note that the endurance limit and its modifying factors are originally from the SN method, but in ViDa they can also be used to correct the elastic component of the eN curve.

Loading factor that modifies the endurance limit (depends on the main type of loading applied to the specimen). Note that the endurance limit and its modifying factors are originally from the SN method, but in ViDa they can also be used to correct the elastic component of the eN curve.

Temperature factor that modifies the endurance limit (greater temperatures tend to bring down the endurance limit). Note that the endurance limit and its modifying factors are originally from the SN method, but in ViDa they can also be used to correct the elastic component of the eN curve.

Miscellaneous factors that modify the endurance limit (e.g. corrosion). Be careful not to include the stress concentration factor Kt or Kf in the value of ke, since Kt and Kf are already taken care of in the stress calculation. Note that the endurance limit and its modifying factors are originally from the SN method, but in ViDa they can also be used to correct the elastic component of the eN curve.

eN curve of the material and also its elastic and plastic components. The SN curve is also plotted in order to make a comparison with the elastic component of the eN curve. The graph is updated after changes in its parameters only when the Graph | Redraw command is used. To expand or shrink the graph, just double-click on it.

Strain concentration theory used when considering stress concentration factors on the hysteresis loops. Linear theory considers Ke=Kt (strain concentration Ke is equal to Kt), while Neuber theory uses Ke*Ks=Kt^2.

Solves the Neuber system considering that the nominal stress is elastoplastic. This option gives more accurate results if the nominal stress is higher than Sy, but increases the computation time.

Option to or not to calculate the hysteresis loops. This option is a critical one in eN life calculations. If the option is off then the calculations are made without calculating and constructing the hysteresis loops, just directly applying the traditional eN equations (which can result in significant and probably non-conservative calculation errors). Especially if you have a complex loading history, then it is strongly recommended to set this option on in addition to the Loop Corrections Option, in order to obtain an accurate result.

Option to or not to correct the hysteresis loops using some experimentally proven criteria. It is highly recommended to set this option on because uncorrected hysteresis loops (taken directly from the hysteresis loops equations) can lead to unrealistic and probably non-conservative stress-strain predictions (see the Textbook "Fatigue Design under Complex Loading" for more information).

Option to or not to plot the stress-strain cyclic curve together with the hysteresis loops, just for visualization purposes. This curve is useful to visually compare the corrected and uncorrected hysteresis loops (set in the Loop Corrections Option).

Option to rainflow count the calculated strains. After the strains are calculated and the correct hysteresis loops are plotted, this option counts the peaks and valleys of the strain history using the rainflow method prior to the eN curve life calculation. The user can also input a strain amplitude filter (in microstrains), to discard the small events that cause no damage.

Option to define a range of hysteresis loops that the user wants to plot for visualization purposes. This range doesn’t affect the calculations (the program needs to calculate ALL the hysteresis loops in any circumstances).

Resolution in number of points of each hysteresis loop for calculation accuracy purposes. In general 40 points is a good choice.

Resolution in number of points of each hysteresis loop for plotting purposes. If you’re plotting too many hysteresis loops, you might have to reduce the number of plotting points for each loop. This number does not affect the calculation accuracy.

Shows a window with some useful information about hysteresis loops calculations.

Stress concentration factor of the specimen (relating the nominal loading history and the most stressed point). Its value can also be calculated using the Calculate Kt Button | Typical or the Calculate Kt Button | Stored commands.

Goes to the Calculate Typical Stress Concentration Factor (Kt) Window, where the user can calculate the value of Kt for Notched/Filleted Bars or Shafts of any dimensions.

Goes to the Smart Calculator window, where the user can calculate the value of Kt using the equations from the Kt Equations Database (or any other equation defined by the user).

Calculates damage by the eN Method, using the Loading Window loadings, the material properties and the chosen options, and goes back to the Main Window.

Cancels the eN Method calculation and goes back to the Main Window.

Calculates the damage and remaining life using the eN Method (recommended in the presence of plastic deformations at the critical point, normally a notch root) and the loading history from the Main Window. The user can alter the material eN curve equation and calculate and input stress concentration factors. The default eN curve data in this window comes from the Materials database and the Kt value is maintained from your last calculation. Many more options are available in the extended Calculate Life (eN) window, using the Tools | Options command in the Main Window and the Extended option in the Modeling tab, prior to calculating life.

After tuning the desired properties, just click on the OK button to return to the Main Window and perform the calculations.

To check information on the available commands, please refer to the correspondent extended window.

Calculates unidimensional crack growth using the da/dN Method and the loading history from the Main Window. The user can input specimen characteristics (such as its total width and crack initial size), alter the material Paris or Elber law constants or include a new da/dN or stress intensity factor equation (which can be stored in the da/dN or KI Equations Database), input crack growth retard effects, choose to use the RMS approach in the calculation and many other options.

Some of the default data in this window comes from the Materials database and the rest is maintained from your last calculation. A simplified Crack Growth (da/dN) window (recommended for beginners) is also available by using the Tools | Options command in the Main Window and choosing the Simplified option in the Modeling tab, prior to calculating the crack growth. After tuning the desired properties, just click on the OK button to return to the Main Window and perform the calculations.

Title of the calculation that is about to be performed. This is an optional field, useful to identify and compare results from different calculations in the Calculation Logbook Window.

Threshold Stress Intensity Factor of the material (value of deltaK below which the crack does not propagate). The default value of deltaKth is loaded from the Materials Database, but it can be changed by the user (be careful with the Elber da/dN equation since it’s very sensitive to deltaKth).

Critical (Rupture) Stress Intensity Factor of the material. The default value of KIc is loaded from the Materials Database, but it can be changed by the user.

Option that let the user choose the Paris equation (da/dN = A*deltaK^m) among the da/dN equations he wants to use in the crack growth calculation. Checking all options makes the program calculate crack growth independently using all da/dN equations, but the calculation takes longer.

Coefficient A from the Paris equation (da/dN = A*deltaK^m). The default value of A is loaded from the Materials Database, but it can be changed by the user.

Exponent m from the Paris equation (da/dN = A*deltaK^m). The default value of m is loaded from the Materials Database, but it can be changed by the user.

Loads the values of the A and m coefficients of the Paris da/dN equation da/dN=A*deltaK^m from the Materials Database directly into the current window.

Loads the values of the A and m coefficients of the Paris da/dN equation da/dN=A*deltaK^m from the Experimental Points tab in the Materials Database directly into the current window.

Calculates the A and m coefficients of the Paris da/dN equation da/dN=A*deltaK^m from Rolfe-Barson’s estimates that depend only on the steel microstructure.

Option that let the user choose the Elber equation (da/dN = A*(deltaK-deltaKth)^m) among the da/dN equations he wants to use in the crack growth calculation. Checking all options makes the program calculate crack growth independently using all da/dN equations, but the calculation takes longer.

Coefficient A from the Elber equation (da/dN = A*(deltaK-deltaKth)^m). The default value of A is loaded from the Materials Database, but it can be changed by the user.

Exponent m from the Elber equation (da/dN = A*(deltaK-deltaKth)^m). The default value of m is loaded from the Materials Database, but it can be changed by the user.

Loads the values of the A and m coefficients of the Elber da/dN equation da/dN=A*(deltaK-deltaKth)^m from the Materials Database directly into the current window.

Loads the values of the A and m coefficients of the Elber da/dN equation da/dN=A*(deltaK-deltaKth)^m from the Experimental Points tab in the Materials Database directly into the current window.

Option that let the user choose the Walker equation (da/dN = A*deltaK^m / (1-R)^p) among the da/dN equations he wants to use in the crack growth calculation. Checking all options makes the program calculate crack growth independently using all da/dN equations, but the calculation takes longer.

Option that let the user choose the Modified Walker equation (da/dN = A*(deltaK-deltaKth)^m / (1-R)^p) among the da/dN equations he wants to use in the crack growth calculation. Checking all options makes the program calculate crack growth independently using all da/dN equations, but the calculation takes longer.

Exponent p from the Walker (da/dN = A*deltaK^m / (1-R)^p) and Modified Walker (da/dN = A*(deltaK-deltaKth)^m / (1-R)^p) equations. The default value of p is loaded from the Materials Database, but it can be changed by the user.

Option that let the user choose the da/dN equation shown in the da/dN Formula field among the da/dN equations he wants to use in the crack growth calculation. Checking all options makes the program calculate crack growth independently using all da/dN equations, but the calculation takes longer.

Option to use typical da/dN equations (faster computation time) or equations retrieved from the Equations Database.

Shows the typical da/dN equation window, where the user can choose from different equations.

Automatically adjusts the constants of the Typical da/dN equation to the database values of Paris and Elber of the current material.

List of names of the available da/dN equations from the Equations Database. Just click on the desired name to load its Formula.

Formula of the da/dN equation loaded from the Equations Database through the da/dN Equation Names list. The formula can also be edited by the user and even added to the Equations Database (by using the Add button). You can also easily tune in the coefficients of the da/dN Formula by interactively editing the Variables Table and using the Graph | Redraw command until the curve is visually compatible with the Paris and Elber curves in the da/dN graph.

Calculates the value of da/dN for the current Formula and Variables Table values. The user is asked to input the stress intensity factor range deltaK and the ratio R=Kmin/Kmax for which he wants to calculate the da/dN value.

Adds the da/dN equation present in the da/dN Formula field to the Equations Database. The user will be asked to enter a name for this new equation.

Shows (just for reference) a window with the equations syntax and all the material properties that can be literally used in the equations.

Table containing variables that can be set by the user. To set a variable, just click on it and type its new value. If these variables are present in the da/dN (or KI) Formula then their values are used in the calculations.

Loads a previously saved Variables Table file (*.var) containing the values of all variables from the Variables Table.

Saves the values of the variables from the Variables Table to a Variables Table file (*.var).

da/dN curves of the material using Paris and Elber laws (and a third da/dN equation chosen by the user when using the Extended Modeling option). Note that the value of deltaKth substantially affects the Elber law curve. The graph is updated after changes in its parameters only after the Graph | Redraw command is used. To expand or shrink the graph, just double-click on it.

Initial size of the crack length a.

Size of the crack length a above which the calculation stops. This is one of the criteria to stop the calculations, and it can be used for instance to calculate the number of cycles that it takes to reach a certain crack size. If you don’t want to use this criterion, just set it to a very high value (for unidimensional crack growth, set it to greater than the specimen width w value).

Width of the considered specimen (specimen dimension in the crack growth direction for unidimensional crack growth), used in the calculation of the stress intensity factor.

Option to use typical KI, KII or KIII equations (faster computation time), equations retrieved from the Equations Database, or values interpolated using a chart containing the geometry factor beta for each crack size.

Shows the typical KI equation window, where the user can choose from different KI equations.

Shows the typical KII and KIII equation window, where the user can choose from different equations.

List of names of the available KI (stress intensity factor) equations from the Equations Database. Just click on the desired name to load its Formula.

Formula of the KI (stress intensity factor) equation loaded from the Equations Database through the KI Equation Names list. The formula can also be edited by the user and even added to the Equations Database (using the Save As New button).

Calculates the value of KI (stress intensity factor) for the current Formula and Variables Table values. The user is asked to input the stress variation deltaSigma (S) for which he wants to calculate the KI value.

Adds the KI (stress intensity factor) equation present in the KI Formula field to the Equations Database. The user will be asked to enter a name for this new equation.

Chart containing the geometry factor beta for each crack size, which will be interpolated to calculate KI.

Commands to create a new, open, save or define the number of rows of the charted KI table. The KI charts can be loaded from *.ki files or from files generated by the Quebra Finite Element software.

Views the drawing of the specimen generated by the Quebra Finite Element software.

Option of retardation effects due to overloads.

Shows a window with some information about the Retardation Effect models used by ViDa.

Option not to consider crack retardation effects.

Option to use the Wheeler retard effect correction. Here da/dN is multiplied by the factor (PZi/(PZol+aol-ai))^wh, where wh is the Wheeler exponent. PZol and aol are the plastic zone and crack sizes on the overload, and PZi and ai are the current plastic zone and crack sizes.

Option to use the Modified Wheeler retard effect correction. Here deltaK is multiplied by the factor (PZi/(PZol+aol-ai))^whm, where whm is the Modified Wheeler exponent. PZol and aol are the plastic zone and crack sizes on the overload, and PZi and ai are the current plastic zone and crack sizes.

Generalization of the Wheeler Option, where da/dN is multiplied by an arbitrary equation defined by the user. To choose from some pre-defined equations, press the Open button next to this option.

Generalization of the Modified Wheeler Option, where deltaK is multiplied by an arbitrary equation defined by the user. To choose from some pre-defined equations, press the Open button next to this option.

Option to model crack retardation effects by changing the value of the load ratio R (=Kmn/Kmx) to an effective value. To choose from some pre-defined equations (including the Willemborg model), press the Open button next to this option.

Percentage of (PZol-PZi) on the crack growth for which the retardation factor is recalculated (PZol is the plastic zone on the overload and PZi is the current plastic zone). In order to speed up the calculations, the program only recalculates the retardation factor when the crack has grown more than this percentage of the distance between the overload and current plastic zones.

Graphs of the retardation equations. The top graph plots the Wheeler, Modified Wheeler, da/dN Factor and deltaK Factor, while the bottom graph plots the Effective R for different load ratios R.

Equation used to calculate the size of the plastic zone ahead of the crack tip (for retardation calculations). The user can choose among plane stress, plane strain, or define a different factor for the equation of the plastic zone size.

Option for sequential crack growth calculations. Click on this option to let ViDa calculate crack growth sequentially from the loading history (instead of using the Root Mean Square approach).

Option for crack growth calculations using the Root Mean Square approach. Click on this option to let ViDa calculate a RMS stress value of all the loading history and then integrate the da/dN equation to calculate the crack growth (instead of sequentially calculating the crack growth for each loading). Note that this option cannot consider retardation effects.

For the Sequential option, this is the increase percentage of the square root of the crack size for which the Stress Intensity Factor KI is recalculated. In order to speed up the calculations, the program only recalculates KI when the square root of the crack size has grown more than this percentage. Typical values are in the 0.1 – 1.0% range. For the Krms option, this resolution is the integration step of Simpson's integral rule.

Shows a window with some information about the square root of the crack size criterion.

Calculates crack growth using the da/dN Method for the Loading Window loadings using the material properties and the chosen options, and goes back to the Main Window.

Cancels the crack growth calculation and goes back to the Main Window.

Calculates unidimensional crack growth using the da/dN Method and the loading history from the Main Window. The user can input specimen characteristics (such as its total width and crack initial size), alter the material Paris or Elber law constants and choose a stress intensity factor equation (loaded from the KI Equations Database).

Some of the default data in this window comes from the Materials database and the rest is maintained from your last calculation. Many more options are available in the extended Crack Growth (da/dN) window, which is available by using the Tools | Options | Simplified command in the Main Window prior to calculating the crack growth.

After tuning the desired properties, just click on the OK button to return to the Main Window and perform the calculations.

To check information on the available commands, please refer to the correspondent extended window.

Calculates bidimensional crack growth using the da/dN Method (combined with elliptical cracks stress intensity factor equations) and the loading history from the Main Window. The cracks are assumed elliptical in shape, with semi-axis a and c. The corner crack is assumed to be a quart ellipsis, the surface crack a semi ellipsis and the internal crack a full ellipsis. The cracks can change the a/c ratio during their propagation, but remain elliptical.

The user can input specimen dimensions and 2D-crack characteristics (such as its initial type and dimensions), alter the material Paris or Elber law constants or include a new da/dN equation (which is stored in the da/dN Equations Database), input crack growth retard effects, choose to use the RMS approach in the calculation, define desired output graphs to be plotted after the calculation and many other options.

Some of the default data in this window comes from the Materials database and the rest is maintained from your last calculation. This window is only available with the Extended Modeling option from the Options Window. After tuning the desired properties, just click on the OK button to return to the Main Window and perform the calculations.

Title of the calculation that is about to be performed. This is an optional field, useful to identify and compare results from different calculations in the Calculation Logbook Window.

Threshold Stress Intensity Factor of the material (value of deltaK below which the crack does not propagate). The default value of deltaKth is loaded from the Materials Database, but it can be changed by the user (be careful with the Elber da/dN equation since it’s very sensitive to deltaKth).

Critical (Rupture) Stress Intensity Factor of the material. The default value of KIc is loaded from the Materials Database, but it can be changed by the user.

Option that let the user choose the Elber equation (da/dN = A*(deltaK-deltaKth)^m) among the da/dN equations he wants to use in the crack growth calculation. Checking all options makes the program calculate crack growth independently using all da/dN equations, but the calculation takes longer.

Coefficient A from the Elber equation (da/dN = A*(deltaK-deltaKth)^m). The default value of A is loaded from the Materials Database, but it can be changed by the user.

Exponent m from the Elber equation (da/dN = A*(deltaK-deltaKth)^m). The default value of m is loaded from the Materials Database, but it can be changed by the user.

Loads the values of the A and m coefficients of the Elber da/dN equation da/dN=A*(deltaK-deltaKth)^m from the Materials Database directly into the current window.

Loads the values of the A and m coefficients of the Elber da/dN equation da/dN=A*(deltaK-deltaKth)^m from the Experimental Points tab in the Materials Database directly into the current window.

Option that let the user choose the Modified Walker equation (da/dN = A*(deltaK-deltaKth)^m / (1-R)^p) among the da/dN equations he wants to use in the crack growth calculation. Checking all options makes the program calculate crack growth independently using all da/dN equations, but the calculation takes longer.

Exponent p from the Modified Walker (da/dN = A*(deltaK-deltaKth)^m / (1-R)^p) equations. The default value of p is loaded from the Materials Database, but it can be changed by the user.

Option that let the user choose the da/dN equation shown in the da/dN Formula field among the da/dN equations he wants to use in the crack growth calculation. Checking all options makes the program calculate crack growth independently using all da/dN equations, but the calculation takes longer.

Option to use typical da/dN equations (faster computation time) or equations retrieved from the Equations Database.

Shows the typical da/dN equation window, where the user can choose from different equations.

Automatically adjusts the constants of the Typical da/dN equation to the database values of Paris and Elber of the current material.

List of names of the available da/dN equations from the Equations Database. Just click on the desired name to load its Formula.

Formula of the da/dN equation loaded from the Equations Database through the da/dN Equation Names list. The formula can also be edited by the user and even added to the Equations Database (by using the Add button). You can also easily tune in the coefficients of the da/dN Formula by interactively editing the Variables Table and using the Graph | Redraw command until the curve is visually compatible with the Paris and Elber curves in the da/dN graph.

Calculates the value of da/dN for the current Formula and Variables Table values. The user is asked to input the stress intensity factor range deltaK and the ratio R=Kmin/Kmax for which he wants to calculate the da/dN value.

Adds the da/dN equation present in the da/dN Formula field to the Equations Database. The user will be asked to enter a name for this new equation.

Shows (just for reference) a window with the equations syntax and all the material properties that can be literally used in the equations.

Table containing variables that can be set by the user. To set a variable, just click on it and type its new value. If these variables are present in the da/dN (or KI) Formula then their values are used in the calculations.

Loads a previously saved Variables Table file (*.var) containing the values of all variables from the Variables Table.

Saves the values of the variables from the Variables Table to a Variables Table file (*.var).

da/dN curves of the material using Paris and Elber laws (and a third da/dN equation chosen by the user when using the Extended Modeling option). Note that the value of deltaKth substantially affects the Elber law curve. The graph is updated after changes in its parameters only after the Graph | Redraw command is used. To expand or shrink the graph, just double-click on it.

Initial size of the crack length a.

Size of the crack length a above which the calculation stops. This is one of the criteria to stop the calculations, and it can be used for instance to calculate the number of cycles that it takes to reach a certain crack size. If you don’t want to use this criterion, just set it to a very high value.

Initial size of the crack length c (see the Crack Type Drawings).

Size of the crack length c above which the calculation stops. This is one of the criteria to stop the calculations, and it can be used for instance to calculate the number of cycles that it takes to reach a certain crack size. If you don’t want to use this criterion, just set it to a very high value (e.g. greater than the specimen width w value).

Option to use typical KI 2D equations (faster computation time) or equations retrieved from the Equations Database.

Shows the typical KI 2D equation window, where the user can choose from different KI equations.

List of names of the available KI 2D (stress intensity factor) equations from the Equations Database. Just click on the desired name to load its Formula.

Formulas of the KI 2D (stress intensity factor) equation in a and c loaded from the Equations Database through the KI Equation Names list. The formula can also be edited by the user and even added to the Equations Database (using the Save As New button).

Calculates the value of KI 2D (stress intensity factor) in a and c for the current Formula and Variables Table values. The user is asked to input the stress variation deltaSigma (S) for which he wants to calculate the KI value.

Adds the KI 2D (stress intensity factor) equation present in the KI Formula fields to the Equations Database. The user will be asked to enter a name for this new equation.

Factor by which the loadings of the Loading Window are multiplied and considered as Tension / Bending / Pressure Stresses applied to the specimen (see the red arrows in the Crack Type Drawings). If this factor is 1 then the loading history is used as these stresses, if it’s zero then these stresses are not considered. Use these values to combine Tension / Bending and Pressure loadings.

Option of retardation effects due to overloads.

Shows a window with some information about the Retardation Effect models used by ViDa.

Option not to consider crack retardation effects.

Option to use the Wheeler retard effect correction. Here da/dN is multiplied by the factor (PZi/(PZol+aol-ai))^wh, where wh is the Wheeler exponent. PZol and aol are the plastic zone and crack sizes on the overload, and PZi and ai are the current plastic zone and crack sizes.

Option to use the Modified Wheeler retard effect correction. Here deltaK is multiplied by the factor (PZi/(PZol+aol-ai))^whm, where whm is the Modified Wheeler exponent. PZol and aol are the plastic zone and crack sizes on the overload, and PZi and ai are the current plastic zone and crack sizes.

Generalization of the Wheeler Option, where da/dN is multiplied by an arbitrary equation defined by the user. To choose from some pre-defined equations, press the Open button next to this option.

Generalization of the Modified Wheeler Option, where deltaK is multiplied by an arbitrary equation defined by the user. To choose from some pre-defined equations, press the Open button next to this option.

Option to model crack retardation effects by changing the value of the load ratio R (=Kmn/Kmx) to an effective value. To choose from some pre-defined equations (including the Willemborg model), press the Open button next to this option.

Minimum overload percentage that activates the calculation with retardation effects. If the overload percentage is smaller than this value, the retardation effects are neglected. Use the value 0% to always consider the retardation effects.

Percentage of (PZol-PZi) on the crack growth for which the retardation factor is recalculated (PZol is the plastic zone on the overload and PZi is the current plastic zone). In order to speed up the calculations, the program only recalculates the retardation factor when the crack has grown more than this percentage of the distance between the overload and current plastic zones.

Graphs of the retardation equations. The top graph plots the Wheeler, Modified Wheeler, da/dN Factor and deltaK Factor, while the bottom graph plots the Effective R for different load ratios R.

Equation used to calculate the size of the plastic zone ahead of the crack tip (for retardation calculations). The user can choose among plane stress, plane strain, or define a different factor for the equation of the plastic zone size.

Option for sequential crack growth calculations. Click on this option to let ViDa calculate crack growth sequentially from the loading history (instead of using the Root Mean Square approach).

Option for crack growth calculations using the Root Mean Square approach. Click on this option to let ViDa calculate a RMS stress value of all the loading history and then integrate the da/dN equation to calculate the crack growth (instead of sequentially calculating the crack growth for each loading). Note that this option cannot consider retardation effects.

For the Sequential option, this is the increase percentage of the square root of the crack size for which the Stress Intensity Factor KI is recalculated. In order to speed up the calculations, the program only recalculates KI when the square root of the crack size has grown more than this percentage. Typical values are in the 0.1 – 1.0% range. For the Krms option, this resolution is the integration step of Simpson's integral rule.

Shows a window with some information about the square root of the crack size criterion.

Option to plot or not the Damage Curve / 2D Crack Graph in the Main Window.

List of the fields that can be plotted in the Damage Curve / 2D Crack Graph in the Main Window after the bidimensional crack growth calculations.

Sampling rate of the events (or ½ cycles) to be plotted in the Damage Curve / 2D Crack Graph in the Main Window after the bidimensional crack growth calculations.

Option to plot or not the Elliptic Cracks Graph in the Main Window.

List of the fields that can be plotted in the Hysteresis Loops / Elliptic Cracks Graph in the Main Window after the bidimensional crack growth calculations. If the ‘Cracks’ value is chosen from the list, then the semi-elliptical crack fronts are plotted.

Sampling rate of the events (or ½ cycles) to be plotted in the Hysteresis Loops / Elliptic Cracks Graph in the Main Window after the bidimensional crack growth calculations.

Calculates bidimensional crack growth using the da/dN Method for the Loading Window loadings using the material properties and the chosen options, and goes back to the Main Window.

Cancels the bidimensional crack growth calculation and goes back to the Main Window.

Stores the total damage and the residual life of the specimen (or the average da/dN and the total crack growth for crack growth calculations) for all the calculations performed by ViDa in the current session. The Calculation Title field in the calculation windows such as the Calculate Life (SN) window is also stored in order to easily compare the results of different calculations. Note that if the Loading Time is not set in the Main Window then the residual life is not added to the Calculation Logbook (since it cannot be calculated).

This window is a very useful tool to compare similar calculations with different option settings from the life/crack growth calculation windows. The tables can also be saved or loaded from a file (as a *.log file) or printed by the user, using the menu commands of the Main Window when the Logbook window is focused.