LMS Virtual.Lab Durability

Transcription

1 LMS Virtual.Lab Durability Durability Step by Step Training Handouts Rev 9-SL1

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3 LMS Virtual.Lab Durability Contents Contents... 3 Introduction... 4 Start LMS Virtual.Lab for the first time... 6 Exercise 1A: Run Analysis and Display Results...9 Exercise 1B: Postprocessing Durability Results Exercise 1C: Linear Superposition Exercise 2A: Set up a Durability Analysis from scratch Exercise 2B: Grouping Exercise 2C: Combine Events Exercise 3: Creating Unit Load Cases Exercise 4: Transient Results Exercise 5: System Level Fatigue Exercise 6: Seam Welds Exercise 7: Spot Welds Exercise 8: Harmonic Fatigue Load Attachment Advanced Features Mode Name Generation Image Generation February 23, 2010

4 LMS Virtual.Lab Durability Introduction LMS Virtual.Lab Durability provides all necessary tools for pre- and post-processing durability results for component and system level fatigue. Component Fatigue The "Component Fatigue" analysis performs a durability analysis on a component for known forces and moments acting on this component. The forces and moments are collected in one or multiple Load Function Sets. For each of the applied loads a unit load case has to be prepared. Therefore, we load a FE Model and prepare the FE solver. The results are loaded back into Mode Sets. The combination between the loads and the unit load cases is done in the Load - FE assignment. To set up a durability analysis you select the analysis type (e.g. stress-life, strain-life). Furthermore, the parts of the component (or the entire component) for which an analysis should be performed have to be defined and some durability specific material and fatigue properties that are read from a database have to be assigned. The LMS FALANCS solver then generates results for the complete analysis case and dedicated postprocessing options

5 Introduction System Level Fatigue If the loads acting on the component are not known, they may be simulated by a multi body simulation (MBS) using the Mechanism Design modules of Virtual.Lab Motion. The recommended way of simulation would be to calculate the component(s) of interest for durability as flexible components. When the MBS solution has finished the command "Transfer Modal Participation Factors" is used to generate a Load - FE assignment directly in the flexible component document. To set up a durability analysis you select the analysis type (e.g. stress-life, strain-life). Furthermore, the parts of the component (or the entire component) for which an analysis should be performed have to be defined and some durability specific material and fatigue properties that are read from a database have to be assigned. The LMS FALANCS solver then generates results for the complete analysis case and dedicated postprocessing options

6 LMS Virtual.Lab Durability Start LMS Virtual.Lab for the first time When starting LMS Virtual.Lab for the first time, every user has to perform a few one-time steps in order to get the software ready to work. Confirm the following messages by pressing the "OK" button. Press "Select Configurations" in the window "LMS Virtual.Lab License Administration": First, activate the configuration "Premium Desktop (VL-HEV.22.1)". Then, activate "Vibration Fatigue (VL-DUR.23.2)" and "System Level Fatigue (VL-DUR.25.2)". -6-

7 Start LMS Virtual.Lab for the first time Note: Depending on the active license file, there may be additional configurations like "Body Fatigue", "Component Fatigue", or other (not durability related) configurations. They may be activated as well, but are not required for this collection of exercises. Close the window "Configurations Selection" by pressing the "OK" button. Back in "LMS Virtual.Lab License Administration", press the all available options permanently. Change the selection "Current Product Configurations" to "System Level Fatigue (VL-DUR.25.2)", and press the button again. Close the remaining windows by pressing "OK", and finally close the main application window "LMS Virtual.Lab 9-SL1". button to select When restarting LMS Virtual.Lab, everything necessary should be configured and the application window should look as shown in the following screenshot. -7-

8 LMS Virtual.Lab Durability Note: If desired change the GUI language via Tools Customize Options User Interface Language We recommend using the English GUI in order to run the following examples most easily. -8-

9 Exercise 1A: Run Analysis and Display Results Exercise 1A: Run Analysis and Display Results In this part we start with existing analysis files, set up a durability analysis, run it and use the postprocessing facilities. The definition of the loads and the import of FE-results will be discussed in a different tutorial. Open the Plate_Load-FE-Assignment.CATAnalysis (File Open), which is located on the directory "plate" of the training data. A new window opens, showing the mesh of the plate. The object tree on the left hand side has entries for "Unit Load Case Results", "Dynamic Loading", and the "Load - FE-Assignment". This includes all the FE results, the load time histories and the connection between the load and the FE results. This is a load template. We could have loaded it into a new document by choosing "File New From" instead of "File Open". -9-

10 LMS Virtual.Lab Durability Suggestion: Make yourself familiar with the viewing features like pan, rotate, and zoom. Explore the possibilities of the "compass". Since the analysis document contains a prepared setup, we can directly define a durability analysis for this problem: Insert Finite Life Durability Cases Strain Life Analysis Case. The "Create Durability Analysis Case" window opens: Click the "Load - FE Assignment" feature in the tree in order to use this existing assignment. Change the name to "Plate Analysis" as shown in the screen shot. After pressing "OK", you will find the new analysis feature in the tree: Now, we add material and fatigue parameters from the LMS FALANCS (i.e. the durability solver) database: Double-click on Material

11 Exercise 1A: Run Analysis and Display Results The selection window for material data sets opens. Select the database "Examples", select the entry "30_CrMo_2", and press "OK". Proceed accordingly for the "Fatigue Parameter", and select the "Default" parameter set from the "Examples" database. Now, everything is set up for the durability analysis of the plate. Right-click on the "Plate Analysis Solution" and select "Compute"

12 LMS Virtual.Lab Durability The computation window appears: Press "OK" to start the calculation. The computation preparation window shows up for a short time. Then the window "Computing" shows the progress. Note: While the solver is running, you can go on working with LMS Virtual.Lab. The system automatically recognizes when the solution is ready, and the "Not up to date" indicator disappears from the solution:

13 Exercise 1A: Run Analysis and Display Results We can now close the "Computing" window and create some result displays. Select the "Generate Image" feature within the context menu of the Solution: In the "Image Generation" window, select "Fatigue Damage (Discontinuous)", and press "OK". Note: Make sure that the mesh is visualized with the option "Material": View Render Style Customize View: Right-click on "Nodes and Elements" and select "Hide/Show"

14 LMS Virtual.Lab Durability In the default solution image shown now, the damage values are different on both sides of the shell elements. The model must be turned over in order to see the maximum damage. An easier visualization of results on shells can be achieved by changing the image criterion. Double-click the image (or the entry "Fatigue Damage (Discontinuous)" in the specification tree). Select "Scalar max" in the criteria list: Suggestion: Make yourself familiar with the available image types. See the different options for averaging the values. In order to obtain a better distinction within the damaged region, we trim the color map manually. Double-click on the color map on the right hand side of the workspace, and expand the "Color Map Edition" window by pressing "More>>". Impose a minimum value of "1e-007", and change the color distribution mode to "Logarithmic":

15 Exercise 1A: Run Analysis and Display Results However, LMS Virtual.Lab Durability provides a more convenient way to obtain the color scaling for the regions of interest. Select the "Failure Mode Group" feature from the context menu on the "Plate Analysis Solution": Right-click on "Maximum Fatigue Damage (Discontinuous)" and select "Hide/Show". LMS Virtual.Lab Durability automatically creates groups of the elements depending on their type of damage (i.e. none, cyclic, or static). The green elements are not damaged at all, the yellow ones are showing cyclic failure and the red area is failing due to a static overload. For this model, no static failure occurs. You can also check this by right-clicking on "Failure Mode" and selecting the "Group Selection Dialog" entry. Now, we can use these groups for confining the display

16 LMS Virtual.Lab Durability Hide the colors of the groups, by right-clicking on "Failure Mode" and selecting "Hide/Show". Right-click on "Maximum Fatigue Damage (Discontinuous)" and select "Hide/Show" to display the result image again. Double-click the image. In the Image Edition dialog, change to the "Selections" tab, and move the group "Cyclic Failure (Plate Analysis)" to the list of "Activated Groups": For discontinuous results, there are typically some elements with "No Damage" nodes as well as "Cyclic Failure" nodes. A logarithmic color distribution is only possible if all values of an image are greater than zero. We use an additional option of the image feature to mask out the nodes with zero values. Open the Image Edition (unless it is still open), and press the "More >>" button. In the "Limits" area, activate the option "Keep only", and (unless the "Interval" window does not open immediately) press the " " button next to the option. In the "Interval" window, specify to keep only values greater than zero: Close the windows "Interval" and " Image Edition" by pressing "OK". Double-click the color map and de-select the "Imposed min" option again

17 Exercise 1A: Run Analysis and Display Results Now, the image shows the cyclic failing elements only: There are more result images to display. You can find a list at the end of this tutorial (see page 120). Since the next exercise is based on the current one, it is advisable to save it now: Save the current analysis by selecting "File Save As" (using a new file name)

18 LMS Virtual.Lab Durability Exercise 1B: Postprocessing Durability Results Hot Spot Detection Post-processing functional performance values is usually done by analyzing contour plots of the result value only. E.g., the main result of a durability analysis is the damage or the fatigue life of the nodes/elements of the structure. Displaying a contour plot of the damage is thus the first analysis of the durability results. However, it is often difficult to identify the critical locations (hot spots). Finding the element with the worst performance (i.e. largest damage) leads to the number one hot spot, but the other hot spots may be hard to find. Just to look up a list of the 10 or 50 elements with the worst performance does not help, since many of them will be at the same region. That is why an algorithm has been implemented to identify the hot spots and build groups out of them for further analysis, e.g. Local Stress History export. Although this algorithm had been developed for durability results, it can and should be applied to all scalar contour plots of the structure, e.g. equivalent stress plots. Hot spots are areas of locally bad (or good) performing result values. One value is assigned to each element by searching the maximum of its nodal values. Each hot spot is characterized by one 'center element', which has the highest value in a certain neighborhood. If such an element has been found, the neighborhood of this element is analyzed. If the elements in this neighborhood have a value that is close enough to the damage of the center element, they are added to the hot spot. Right-click on the durability image and select "Compute Hot Spots": In the following window, change the name to "Damaged Regions". The default parameters are suitable for current durability result. So, just press "OK". The algorithm generates both a group set and an IO-set with the most damaged nodes in each group. A list of hot spots can also be displayed based on the Hot Spot feature "Damaged Regions"

19 Exercise 1B: Postprocessing Durability Results Right-click the new "Damaged Regions" entry in the tree and select "List Hot Spots": Note: You can use the hot spot groups e.g. as input for another durability analysis or in the selection entry of result images. However, never use a "Hot Spot" mesh group on the "Selections" tab of the image that has been used as input for the hot spot detection

20 LMS Virtual.Lab Durability Generate Local Tensor Histories The hot spots ("Damaged Regions_Critical Points") may be used to calculate local stresses or other local histories. Select Insert Local History /PSD Cases Local Tensor History / PSD Case Click "Load - FE Assignment" in the specification tree, and create the analysis case by pressing "OK". Expand the tree of the "Local Tensor History Case", right-click on the "Group Set", and select "Mesh Grouping Auto-update Group" from the context menu. Select "Group from Feature" and press "OK"

21 Exercise 1B: Postprocessing Durability Results Click on "Hot Spot 1" in the sub tree "Damaged Regions_Critical Points", and change the name of the group to "Hot Spot 1". (To do so, you have to deactivate the option "Update Group Name Automatically".) Start the computation of the "Local Tensor History Solution":

22 LMS Virtual.Lab Durability Note: The user can control the types of calculated histories by double-clicking the "Local Tensor History Solution" feature: After the calculation is finished, there are several possibilities of result visualization. Generate a "New Function Display" via the context menu of the "Local Tensor History Solution": Select "Stress Tensor2d" and press "Finish". In the new window, select an arbitrary entry in the list of available data, and press "Add to Display"

23 Exercise 1B: Postprocessing Durability Results In the 2D display, you can analyze the tensor component values over time:

24 LMS Virtual.Lab Durability Hint: If desired the unit of the stresses (or any other physical magnitude) can be changed. Open "Tools Options Parameters and Measure", and change to the "Units" tab: Export Local Tensor Histories Another feature of the Local Tensor History Case is the export of the generated load histories. That way, it is possible to perform further analyzes e.g. in third party software. Right-click on "Local Tensor History Solution", and select "Export Local History Case". Within the export GUI, select the desired results to be exported. Specify the target directory and file name as well as the file format:

25 Exercise 1B: Postprocessing Durability Results The software creates time history files using the following naming conventions: File names (for each node group and node ID): <User_defined_name>_<node_group_name>_<node_ID>.<extension> Channel names (for each element the current node belongs to): <element_id>_<face_of_solid>_<side_of_shell>_<tensor_component> In our example, we get the file "C:\temp\stress_Hot Spot 1_154.asc". It contains the channels: 129_0_0_S_XX, 129_0_0_S_YY, 129_0_0_S_ZZ, 129_0_0_S_YZ, 129_0_0_S_XZ, 129_0_0_S_XY 129_0_1_S_XX, 129_0_1_S_YY, 129_0_1_S_ZZ, 129_0_1_S_YZ, 129_0_1_S_XZ, 129_0_1_S_XY 130_0_0_S_XX, 130_0_0_S_YY, 130_0_0_S_ZZ, 130_0_0_S_YZ, 130_0_0_S_XZ, 130_0_0_S_XY 130_0_1_S_XX, 130_0_1_S_YY, 130_0_1_S_ZZ, 130_0_1_S_YZ, 130_0_1_S_XZ, 130_0_1_S_XY

26 LMS Virtual.Lab Durability Exercise 1C: Linear Superposition The Linear Superposition Feature is used to animate a linear combination of mode and load data, and to find its extreme values. Specifically, the results are produced by linearly superimposing loads defined in a Load Function Set (modal participation factors, forces, moments, etc.) with modal data (deformation, stress, etc.) defined in a Mode Set. The mapping of the load and mode data is accomplished by using a Load FE Assignment. Calculate Linear Superposition To keep the workbench clearly arranged, start with a new analysis document: Close all analysis documents, and do not overwrite the file "Plate_Load-FEAssignment.CATAnalysis" (File Close). (Re-)Open the Plate_Load-FE-Assignment.CATAnalysis (File Open) Insert Linear Superposition Feature Linear Superposition Feature Activate the option "Use existing Load - FE Assignment" and select the "Load FE Assignment" in the specification tree. Right-click on the "Solution for Linear Superposition Set" and select "Compute". The calculation of the "Linear Superposition Solution" requires only a few seconds. Therefore, it is possible to create an image of the results right away. Right-click on the "Solution for Linear Superposition Set" and select "Stress Image". Hide the "Nodes and Elements" Double-click the newly generated image

27 Exercise 1C: Linear Superposition On the "Visu" tab, select the criterion "Von Mises". Change to the "Occurrences" tab. Here, you can select the desired "Time Step" and "Time". Note: If the deformation of the plate is too large, modify the "Amplification Magnitude" in the "Tools 2D/3D Images" menu. Animate Linear Superposition Instead of manually switching from time step to time step, it is possible to animate the "Linear Superposition Solution":

28 LMS Virtual.Lab Durability Right-click on the image "Stress Von Mises (nodal values)", and select "Animate Linear Superposition Solution" from the context menu. In the "Player" window, change the loop mode to an endless loop by clicking on the arrow. Open the "Player Parameters" (rightmost button) and set the "Sampling Step" (can be selected from the list). Use the different buttons in the "Player" window to control the animation. To close the animation mode, press the button "Animate Linear Superposition Solution" in the toolbar (it stays orange while the "Player" window is opened)

29 Exercise 1C: Linear Superposition Find Extreme Values of Linear Superposition To find the extreme values (for deformation, stress or strain) of the Linear Superposition Solution, use the "Create Time-Series Extrema" command. Right-click on the "Solution for Linear Superposition Set" and select "TimeSeries Extrema". Click on the stress image to select the input item for the calculation of extreme values. Double-click the new "Time-Series Extrema" entry and enter the following parameters. In this example, only the first 3 seconds are taken into account. (The used load history file has a sampling rate of 50 Hz.) Right-click on the "Time-Series Extrema" entry and select "Compute". Close the "Locating extrema" window after the calculation has finished

30 LMS Virtual.Lab Durability Right-click on the "Time-Series Extrema" entry and select "Report Time-Series Extrema". In this example, the minimum value occurs in time step 2, the maximum value occurs in time step 87. To find the location of the maximum value, an image of the calculated time step must be created. Double-click the "Stress Von Mises" image, and switch to time step 87. Select Tools 2D/3D Images Image Extrema, and enter the following parameters for this feature:

31 Exercise 1C: Linear Superposition The node with the maximum Von Mises stress is labeled with a marker and a flag

32 LMS Virtual.Lab Durability Exercise 2A: Set up a Durability Analysis from scratch In this part, we concentrate on the methods to apply loads to a component. Scenario We want to analyze a component (knuckle) where we have performed a multi body simulation (MBS) with an external tool, so we have the component forces available in files. We assume that we calculated two events, i.e. we have two sets of load data: MBS_loads.asc other_loads.asc Import mesh data and FE results Open the Virtual.Lab Start menu and select Durability Durability Analysis A new analysis document with a basic specification tree opens. Hint: For quick access to the most frequently used workbench, open "Tools Customize" and select your favorites on the "Start Menu" tab. The favorite workbenches appear at the top of the "Start" menu. Loading mesh data and FE results works the same within all different LMS Virtual.Lab applications (i.e. workbenches)

33 Exercise 2A: Set up a Durability Analysis from scratch Right-click on the "Links Manager" and select "Import", or use the menu item "File Import". A file selection box opens. Set the file type to "NASTRAN Result File (*.op2,*.pch)" Change to the "Knuckle" sub-directory of the training data and select the file "knuckle.op2". Deactivate the options of the section "Analysis Case Import", set the unit system as shown in the following picture, and press "OK". The mesh is loaded, and a Mode Set with the results of the unit load cases is generated. Double-click on "Mode Set" and enter a new name: Generate a stress plot:

34 LMS Virtual.Lab Durability Right-click on the mode set "Unit Load Case Results", and select "Generate Image" In the window "Image Generation", select the entry "Stress Von Mises (Fringe)", and press "OK". The result looks like in the following picture. The software simultaneously displays the mesh and the stress results of the first unit load case, which will cause an overlay of the images:

35 Exercise 2A: Set up a Durability Analysis from scratch To avoid this effect: Right-click on "Nodes and Elements" and select "Hide/Show" Now, the stress results are clearly visible. By double-clicking on the image or the entry "Stress Von Mises (Fringe)", the "Image Edition" dialog is opened. Here you can select which load case to view, or what entity of the stress results to display. Before going on with the durability analysis definition, we hide the stress image and show the "Nodes and Elements" again:

36 LMS Virtual.Lab Durability Right-click on the image or on "Stress Von Mises (Fringe)" and select "Hide/Show" Right-click on "Nodes and Elements" and select "Hide/Show". Simple load application First, we create a Load Function Set for the multi-body loads. Create a new Load Function Set by selecting "Time-History Load Function Set" from the "Insert" menu. Change the name of the Load Function Set to "MBS Loads" and press "OK". Right-click on "Data Sources" (a child of the new tree entry "MBS Loads") and select "Add a Data File"

37 Exercise 2A: Set up a Durability Analysis from scratch Make sure that the file type is set to "Generic Time History Interface (*.*)" and select the file "MBS_loads.asc" Make sure that the option "Create Input Points" in the "File Data Source" window is activated, and press "OK". Have a look at the functions that are now available with the Load Function Set: Right-click on "MBS Loads" and select "List Functions"

38 LMS Virtual.Lab Durability Note: Since the input points have been created automatically, the listed functions are the same as the input locations: Right-click on "MBS Loads" and select "Check Load Function Set Status". Everything has been assigned automatically, that is why the global status should be okay. This check will be more important in a later exercise. Note: In this case, there is no real link to the FE mesh. This method can be used if the user exactly knows that the names of the loads match the names of the load cases in his op2-file. Plot the time histories in a 2D display Right-click on "MBS Loads" and select "New Function Display"

39 Exercise 2A: Set up a Durability Analysis from scratch Just press "Finish" in the new window, where "2D Display" is pre-selected. A new window with the 2D display opens, and the data selection window is opened automatically. Select the channels you want to display in the left list box ("Node Names") and select the "Default" data case in the right list box. Press "Display". Close the "Select Data" window in order to see the complete plot area

40 LMS Virtual.Lab Durability Note: The data selection can be opened again by pressing the "Select Data" button in the tool bar, or choosing "Select Data" from the context menu. The display has many options to be explored by right-clicking on the different objects like curve, plot area, x-axis, y-axis, legend, Exemplarily, we will try some features: Right-click in the white plot area and select "Double X" from the "Cursor" menu. A pair of cursors is created in the plot area: You can move the cursors by dragging the left one, and you can change the distance by dragging the right one

41 Exercise 2A: Set up a Durability Analysis from scratch Double-click one of the cursors (i.e. a cursor line) to open the "Edit Cursor" window. Here you can specify the cursors positions explicitly, snap the cursors to extreme values or zoom the time axis. Close the window "2D Display XY Plot". Note: An important feature of the 2D display is that after closing the window all settings are kept in the analysis. By re-selecting the image in the tree, you get exactly the same view as before

42 LMS Virtual.Lab Durability The Load FE Assignment Background The "Load - FE Assignment" feature is based on the observation, that a local durability analysis and several other basic analysis cases for Motion and Durability need the local stress time histories as input. To get these local stress time histories, a linear superposition of the stress modes (static, normal or mixed) has to be done. In case of the static superposition, static unit load cases describe the stress distribution on the structure when one of the loads is excited and all others are zero. When multiplying the unit load cases with the corresponding loading history, a stress history is induced on the structure. If several loads are acting, all their contributions are linearly superimposed to get the total stress history on the structure. In case of modal superposition, the static unit load cases are replaced by the normal modes (usually also stress modes) and the loading histories are replaced by the modal contribution factors, which typically should be calculated with the LMS Virtual.Lab Motion application. In the mixed approach (Craig Bampton), both static and normal modes are used and thus also loading histories and modal participation factors at the same time. For both static and modal superposition, the local stresses are given by e i, j ( x, t ) ci, j (k ) ( x) Lk (t ) k Here ci, j (k ) ( x) denotes the k-th mode (static or normal) at local position x and Lk (t ) denotes the k- th load at time t. If the stress modes are normal modes, the loads are represented by the modal participation factors (which can be calculated within LMS Virtual.Lab Motion or an externally called FE package). The formula shows, that the combination of the loads and modes must be given correctly in order to compute the local stress time histories. Creating a Load - FE Assignment You create a Load - FE Assignment after the creation of Load Function Sets (LFS) and Mode Sets (MS) to combine load histories and FE results. Insert a new Load - FE Assignment by selecting the command "Load - FE Assignment" from the "Insert" menu. In the window "Insert Load - FE Assignment", select for both the Load Function Sets and the Mode Sets the "Reference" option instead of the default option ("New"). Click on the Load Function Set "MBS Loads" and the Mode Set "Unit Load Case Results" in the specification tree and press "OK"

43 Exercise 2A: Set up a Durability Analysis from scratch Double-click the "Assignment" feature of the new tree element: In the upper two list boxes, the loads and FE results are shown. In the left one, the load points of the selected load function sets (LFS) are listed. In the right list box, the result cases from the selected mode sets (MS) are shown. Using the sorting buttons, the order in the list boxes may be changed manually. The mode names are generated according to specific rules. You will find a list of these rules at the end of this tutorial (see page 118)

44 LMS Virtual.Lab Durability How to define combinations The simplest way to define the combination is to select the matching pairs in the upper list boxes and press the (Match by) "Order" button in the middle button bar: If the loads and modes are in the correct order, pressing the order button after selecting all loads and FE results combines all pairs at the same time. Note: To make the usage convenient, selecting no load and no FE result is handled as if all loads and FE results were selected, so you do not need to press the two Select All buttons in the case you want to work with the full set. A special feature of the Load - FE assignment is the "Match by Name" mode, where the loads and FE results are automatically matched by their names. Please note that the "Match by Name" option uses the load point names (not the original channel names) and therefore completely complies with the living template concept of LMS Virtual.Lab. Since the names of FE results have to accomplish several rules according to the FE system used, LMS Virtual.Lab uses a multi-step matching algorithm to try to assign the loads and FE results automatically. This algorithm applies in our case so we can use this feature. (Note that we could have done this already in the Load FE Assignment creation window.) Press the (Match by) "Name" button, and the assignment is done automatically:

45 Exercise 2A: Set up a Durability Analysis from scratch Press "OK". Note: This is a good time to save the document as a template for the Load Application

46 LMS Virtual.Lab Durability Advanced Features of the Load Application In this section, we apply loads having different names and use some advanced features of the Load Function Set and the Load - FE Assignment. Select "Insert Time-History Load Function Set", change the name to "Other Loads", and set the "Physical Data Type" to "Force". Often the load application points are well known in advance, and model guidelines are often used to have a strict Node-ID for load application point assignment. Therefore, it is easy to use IO set definition files. Add a prepared IO point definition to the Load Function Set: Right-click on "Input locations [Force]" (entity of the new Load Function Set "Other Loads") and select "Import IOFeatures Definitions". Open the file "knuckle.iop" from the training directory

47 Exercise 2A: Set up a Durability Analysis from scratch Note: Also in the model view, the IO points are created and attached to the correct positions. You may double-click on the IO points to show the degrees of freedom that are transferred at this point. Besides defining the IO points by node ID, the IO point definition file may contain coordinate positions ("hard-points"). While loading such a file, these IO points are automatically attached to the nearest node in the FE model. The IOPoint file is an ASCII file that may be generated automatically by external programs. Of course, one can do the combinations in the 3D view once and export the IO set. Right-click on "Data Sources" (below "Other Loads") and select "Add a Data file". Set the file type to "Generic Time History Interface (*.*)" and select the file "other_loads.asc". Make sure the options "Remove Existing Points" and "Create Input Points" are not active! Note: The default settings for these options can be changed within the options: Tools Options General Data Source

48 LMS Virtual.Lab Durability The Load Attachment In this example, we have to assign the loading channels (load IDs) to the IO points by the load ID name. An automatic attachment is done whenever the channels are named like the IO point "Node ID". Double-click on the "Load Attachments" feature of the Load Function Set "Other Loads". Activate the option "Select Load Id" for the load attachment type, and select in the drop down box the matching load id name. (For the first node ID this is "UPP"). Now, select in the upper box ("Defined Locations") the next line (Location Name "WHEEL") and select the load id "WHL"

49 Exercise 2A: Set up a Durability Analysis from scratch Do the same for LCA (load id "LWR") and STEER (load id "TIR"). Finally, press the "Close" button. Note: Since the load channels and the input location names are known in advance, it is possible to define the full load attachment in a specific XML file. If desired, you can import such an attachment definition using the "Import Load Attachments". (An example can by found in the file "other_loads.xml" among the training data.) In order to see whether the Load Function Set has a correct attachment, rightclick in the Load Function Set "Other Loads" and select the command "Check Load Function Set Status"

50 LMS Virtual.Lab Durability Insert a new Load - FE assignment using the Load Function Set "Other Loads", the Mode Set "Unit Load Case Results", and activate the option "Match by Name". On order to distinguish easily between the two Load FE assignments, we rename them. Double-click and rename both of the Load FE assignments according to the following screen shot: Save the analysis document, but do not close it. The next exercise will continue based on the actual state

51 Exercise 2B: Grouping Exercise 2B: Grouping The grouping can be used to cut down an analysis to parts of the structure, or to apply different material or fatigue parameters. In many cases, the selection is already done by property and/or material ID. In these cases, we would simply do the following: Open the "Insert" menu and select "Mesh Grouping Auto-update Group Set". Create a "Property ID" group set. Activate the option "Show Groups in Tree", and press "OK"

52 LMS Virtual.Lab Durability Right-click on "Property ID Group Set", and open the "Group Selection Dialog". This was just an introducing example to demonstrate an auto-update group set. The "Property ID Group Set" will not be used in the further steps and may be deleted from the specification tree again (by using the <Del> key). In this example, we want to use some of the interactive facilities of the LMS Virtual.Lab mesh grouping interface. Open the "Insert" menu and select "Mesh Grouping Group Set" In the new window, enter a name for the Group set: "Arm", and press "OK"

53 Exercise 2B: Grouping We want to select the steering arm. To do so we will use a rectangular trap selection. First, we switch to a defined view of our component: Open "View Named Views", select the view "* back" and press "OK". Now, it is easier to define the desired group. Right-click on the group set "Arm", and select "Auto-update Group" from the sub-menu "Mesh Grouping". In the new window, select "Trap" and press "OK". Enter the name "Elements of Arm" on the "Common" tab

54 LMS Virtual.Lab Durability Change to the 2nd tab ("Type Specific"), and select the following area by drawing a corresponding trap: Hint: To draw the trap, specify two opposite corners of the desired rectangle by single mouse clicks, i.e. do not keep the mouse button pressed while drawing. After pressing "Apply" in the window "Trap Selection Group" the elements are selected and highlighted by a different color: Leave the "Trap Selection Group" window by pressing "OK". For the analysis, we will split this group into the part of the connection and the remaining part

55 Exercise 2B: Grouping Open "View Named Views" select the view "* left" and press "OK". Add a new auto-update group to the group set "Arm", select again trap selection group. Enter the name "Connection", and select the "Elements of Arm" group as input group. Change to the tab "Type Specific" and select the connection part only: Press "Apply" and leave the "Trap Selection Group" window by pressing "OK". Define a third auto-update group using the type "Difference": Enter the name "Arm without Connection", and select "Elements of Arm" as the Base Group. Select the group "Connection" as the group to subtract

56 LMS Virtual.Lab Durability Press "OK" to complete the group definition. Note: LMS Virtual.Lab offers further Boolean operations for mesh groups as well, such as union and intersection groups. Now, we will define two durability analysis cases. Rather than using the entire model, these analyses will be restricted to the element groups defined before. Define a strain life analysis case: - enter the name "MBS Loads Analysis Case", - reference the first Load FE Assignment (MBS Loads), - reference the element group "Arm without Connection" Right-click on "Element Sets", select the "Add Element Sets" command, and add the "Connection" group

57 Exercise 2B: Grouping Select the material and the fatigue parameters from the "Default" databases:

58 LMS Virtual.Lab Durability It is also possible to assign different parameter sets (material and/or fatigue parameters) for every element set separately. To demonstrate this feature we will assign a specific material for the connection part. Right-click on "Element Set.2" (the one with the mesh group "Connection"), and select "Material Parameter". Select the material parameter set "42_CrMo_4" from the "Default" database. Solve the case. Create another strain life analysis case: - enter the name "Other Loads Analysis Case", - reference the second Load FE Assignment (Other Loads), - reference the task definition of the first solution case

59 Exercise 2B: Grouping Note: It is mandatory to refer to the task definition of the first case. Otherwise, it will not be possible to combine the analysis cases later (next part of this exercise). Solve the second durability analysis case

60 LMS Virtual.Lab Durability Exercise 2C: Combine Events In the final part of this exercise, we will calculate the results for a combination of two cases from the previous part. Create a "Combine Events Case" by selecting the corresponding entry in the "Insert" menu. Double-click on "Events to Combine" in the specification tree. Click on "MBS Loads Analysis Solution" and then on "Other Loads Analysis Solution" in the specification tree. Note: It is also sufficient to click on both of the strain life analysis cases in the tree, i.e. it is not required to expand the tree, but the software automatically adds the corresponding solution when clicking on an analysis case. In the "Events to Combine" window, select the first event, enter a "Repetition Factor" of 50 and press "Apply". Select the second event, enter a "Repetition Factor" of 20 and press "Apply"

61 Exercise 2C: Combine Events Press "OK", and then compute the "Combine Event Solution". View the desired results. Note: A special case of the combined events case may be used if only one event is calculated, but the user has a given target of e.g. 100 repetitions of this event to fulfill the requirements. Then this case can be used to view the results directly for this target

62 LMS Virtual.Lab Durability Exercise 3: Creating Unit Load Cases Open a new Durability Analysis document before proceeding with this example. Import the mesh (NASTRAN Bulk File) of the Knuckle ("knuckle.dat"). Do not forget to adapt the unit system (Meter, Kilogram). Create the same Load Function Set "Other Loads" as in the previous example. Just to sum up the most important steps: set the physical data type to "Force", add the data file "other_loads.asc", import the IO point definition "knuckle.iop", and the load attachments file "other_loads.xml" (see page 46 for the detailed description)

63 Exercise 3: Creating Unit Load Cases Create a "Unit-Load Case Assignment with NASTRAN" (Insert Unit-Load Case Assignment). Select the Load Function Set "Other Loads". This feature creates a "Nastran Static Unit Load Case" and a "Load - FE Assignment": The Load FE Assignment references the Load Function Set and includes a new Mode Set referring to the result of the Nastran solution. Once the Nastran case is solved, everything is prepared for a durability solution

64 LMS Virtual.Lab Durability Double-click the "Nastran Static Unit Load Solution". On the second tab ("Inertia Relief"), activate "Inertia Relief", and select the option "Automatic support (Center of Gravity)" (requires at least Nastran 2001). Note: If you choose the option "On Support Set", an "Inertia Relief Support Set" appears in the tree, where you have to add the degrees of freedom correctly. On the tab "Subcases", the created subcases can be checked: The node IDs with their degrees of freedom correspond to the "Input points" in the tree. Change to the tab "Parameters", and open the "Parameters List"

65 Exercise 3: Creating Unit Load Cases Press the "New" button, and add a new parameter "BAILOUT -1": Press "OK" to close the window "Nastran Case Solution". Double-click the output feature "Vector Output Requests", and deactivate the output of the nodal forces:

66 LMS Virtual.Lab Durability Note: Additional output settings can be configured here. To open additional parameter windows double-click the entries in the "Format", "Extra", and "Group Set" column, respectively. Now, you could run the Nastran case, i.e. right-click on the solution and select "Compute". This requires a Nastran installation and access to a proper license. The parameters of the Nastran solver can be set in "Tools Options Durability NASTRAN " In this tutorial however, we skip the computation and attach a prepared result file instead. Right-click on the solution and select "Attach Result File". Select the result file "nastran_static_unit_load_solution_1.op2" from the sub directory "WorkingDir". Complete the Load FE Assignment by double-clicking "Assignment", and pressing (Match by) "Name"

67 Exercise 3: Creating Unit Load Cases Now, you could go on and define a durability analysis case as explained before

68 LMS Virtual.Lab Durability Exercise 4: Transient Results In all important FE-packages, it is possible to perform a transient analysis, meaning that loads are defined as functions of time and series of (stress-) modes are calculated one for each time step. Depending on the FE-format (Nastran op2, ABAQUS odb, ANSYS rst, etc.), there are different notions for grouping the transient results. In Nastran, there are the transient subcases. Each subcase consists of a sequence of vectors. Each of these vectors corresponds to a time sample. Thus, each subcase may be interpreted as a time history, which may be subject to a durability analysis. Different subcases define different time histories, which for instance will be analyzed in separate durability analysis cases. Combining the results for different subcases can then be done using the combined durability case (TSD). In ABAQUS, there are the steps and increments. In this terminology a step may represent a time history if the loading of this step has been defined accordingly (using the command AMPLITUDE in tabular form). Here, the ABAQUS user has to define the output in a way such that at least the results at the input time samples are listed in the output. In this case, the increments represent the time samples. In ANSYS, the input load time samples are defined in different load cases. In this case, there is no structure like subcases and time samples in Nastran or steps and increments in ABAQUS. It is also possible to use the array parameter method (see ANSYS documentation, Basic Analysis Procedures Guide, Section ) to define a time varying load. The Transient Result Series feature is based on the observation that a local durability analysis and several other basic analysis cases for Motion and Durability require the local stress time histories as input. In the Load - FE-Assignment feature the stress histories are defined as a superposition of load time histories and static modes or modal participation factors and normal modes. In the transient result series, the stress history is explicitly defined as a series of stress plots. In analogy to FE notation (e.g. ABAQUS) the results are grouped in steps (subcases). Each step may contain several increments (time samples). Although the stress results often will be computed using a transient FE-analysis, you can also insert static modes into the transient result series. They are then re-interpreted as a time series of stress plots. This may be used e.g. for rotating components like rims, where each load step may correspond to the rotation of the component by 360 /n degrees. A full rotation then corresponds to the (pseudo-) transient series of these rotational steps. The latter approach is often used for rotating machinery and this will be illustrated in the following example in this tutorial. The transient result series Import the mesh of the rim: Select the NASTRAN bulk deck file "rim.dat" from the directory "Rim". Deactivate all options in the section "Analysis Case Import", and adapt the unit system according to the following screenshot:

69 Exercise 4: Transient Results Select "Transient Result Series" from the "Insert" menu. In the specification tree, you will get the following: Select "Add a Data File" in the context menu of "Data Sources". Insert the file "rim.op2"

70 LMS Virtual.Lab Durability In the window "File Data Source", leave all subcases selected. Double click the "Transient Result Editor": Now, you can see all subcases. For each subsequent analysis, it is possible to de-activate individual steps. For FE analysis results from a non-linear transient analysis, each sub step may show different time steps (increments). By selecting the subcase and pressing the "Select Time Steps" button, you can select the time steps to use. The selected subcases can be scaled by "Modify Subcases". In this example, nothing needs to be changed in the "Transient Results Editor" window

71 Exercise 4: Transient Results Animation On the transient result series, you can generate images of all available results and animate them through the time series: Right-click on the "Transient Result Series" and select "Generate Image". Generate an image of the principal tensor component values ("Average iso"): You can create images on the data source in the same way (context menu) as for data sources of a mode set. Additionally the transient series may be animated. Select "Animate" from the context menu of the image or from "Tools 2D/3D Images". For the animation of transient result series, it is best to choose special Animation options: Press the "More>>" button in the "Animation" window. Then select "All occurrences" and activate the option "Memorize frames"

72 LMS Virtual.Lab Durability Note: After activating the "Memorize frames" option, it will take some time before it is possible to proceed. This delay is caused by reading many data into the main memory. The advantage of using this option is a much smoother animation. Feel free to try some features of the animation feature. Then close the "Animation" window. Analysis Since we have a full transient input, we can directly define the Durability analysis case. Create a new Strain Life Analysis Case: Assign the Material "Ck_45" from the default database. Assign Fatigue Parameter "Pseudo stress, critical plane, open mode (I), P_SWT" from the default database. Compute

73 Exercise 4: Transient Results Visualize the results

74 LMS Virtual.Lab Durability Exercise 5: System Level Fatigue This exercise shows how to create the load information from a multi-body model using the LMS Virtual.Lab Motion workbench and how to proceed performing a durability analysis. A flexible body is used as well in the Motion model (to calculate the modal participation factors) as in the durability calculation (to calculate fatigue damage based on the modal participation factors). Note: It would also be possible to use a rigid body (FE mesh) within the Motion simulation and to export the rigid body loads for the durability calculation. However, that approach would only be advisable if the deformation of the body does not influence the Motion results too much. If the flexibility of the body only leads to very small additional displacements (or rather forces) in the Motion simulation, it could be useful to consider the body as rigid. However, if the displacements are not negligible, this approach may lead to erroneous results. The benefit of using flexible bodies is that the deformation of the body of interest is automatically taken into account. On the other hand, the computation time for the Motion simulation will be longer and a "Craig Bampton" solution of the FE results must be available. A simple Motion model of a single-cylinder engine is available in the training data. Since we do not want to change the original CATAnalysis file, we use it as a template. Use "File New from" and select the file "Engine.CATAnalysis" from the "SystemLevel" directory. Add "Product1_ROOT" to the lower list box, and press OK to close the "New From" dialog. Note: This selection makes sure that we use copies of the source files rather than modifying the original ones. The remaining files (CATPart) are only used as references

75 Exercise 5: System Level Fatigue Use "File Save" to store the new files. Confirm the question about activating other document save operations. Select "conrod" from the "Bodies" sub tree: In the "Bodies" toolbar (or in the context menu), select "Make Flexible with Existing Data": or

76 LMS Virtual.Lab Durability As "Flex Document" select the Nastran bulk file "conrod.bdf" from the "SystemLevel" directory. Confirm the unit system settings. Close the "Log report" windows. Now, a finite element mesh of the connection rod is added to the Motion model. The coordinates of the finite element mesh match the global coordinates of the motion model, and the software finds the connection points in the mesh automatically. It is convenient to visualize only the mesh and not the original geometry anymore

77 Exercise 5: System Level Fatigue Expand the next levels of the specification tree below the "Links Manager", and hide the "conrod" part which is a subentry of "Product1": For the finite element analysis (and the subsequent durability calculation as well), we open the conrod analysis document within a new window. Continue expanding the specification tree below "Product1" until you see " Product1 Flexible Analysis Analysis Manager". Right-click on the "Analysis Manager" and select "Open in New Window" from the submenu "Analysis Manager object". In a new window, a CATAnalysis document is opened. It does not only contain the finite element mesh of the connection rod, but also the interface points ("MotionInterfaceSets") with the Motion model and a predefined "Nastran Craig-Bampton Case". In the "SystemLevel" directory of the training material, you will also find a complete Nastran input file (conrod.dat). If desired you can check in that file the settings and parameters used for the calculation of the training example

78 LMS Virtual.Lab Durability With a proper Nastran installation, we could now compute the Craig-Bampton case. In this tutorial however, we just attach a prepared result file instead. Right-click on the solution and select "Attach Result File". Select the result file "conrod.op2" from the "SystemLevel" directory. Now, the Motion model including the flexible connection rod can be calculated. Switch back to the "Engine_1.CATAnalysis" document. Right-click on the "Solution Set" of the "Analysis Case", and select "Set Working Folder to Model Folder" from the context menu. Right-click on the "Solution Set", and select "Compute". After the solution has been calculated, the modal participation factors can be exported in order to make them available for a durability analysis. Select the "Solution Set" of the current "AnalysisCase"

79 Exercise 5: System Level Fatigue Press the button "Export Modal Participation Factors" (available in the "Analysis Case Operations" toolbar), or select the corresponding feature from the menu "Tools Export Data": Switch back to the "conrod_flex2.catanalysis" document. Note: It is also possible to let LMS Virtual.Lab export the MPFs automatically. To make use of this automatism, open "Tools Options" and activate the corresponding option as indicated below: After performing the feature "Export Modal Participation Factors", several entries have been created automatically. Amongst other things, a fully defined "Load FE Assignment" is available for further analyses. In order to have access to the Durability features we have to switch from the "Flexible Body Design" workbench to the "Durability Analysis": Open the Virtual.Lab Start menu and select Durability Durability Analysis

80 LMS Virtual.Lab Durability Create a new Strain Life Analysis Case referring to the existing Load FE Assignment "Load - FE Assignment.1(/AnalysisCase.1, conrod)". For this example, we do not have a suitable material data set available. Nevertheless, we can take advantage of the "Uniform Material Law" (UML), which estimates the fatigue properties based on extensive statistical studies. Right-click on the "Material" entry within the "Strain Life Task Definition", and select "Material Created By". Select the option "UML (Steel)", and press "OK". Double-click the entry "UML (Steel)" within the "Strain Life Task Definition", and enter the following parameters: Name ConRod Tensile Strength 980 MPa Elastic Modulus MPa

81 Exercise 5: System Level Fatigue Assign Fatigue Parameter "Pseudo stress, critical plane, open mode (I), P_SWT" from the default database. If we ran the durability calculation right now, it would result in static failure all along the connection rod, because the maximum stresses are far above the tensile strength: This comes from unrealistic loadings during the run-up period. As explained in previous exercises, we can create a 2D display of the MPF histories attached to "Load Function Set.1". Looking for instance at "MPF:8", makes it clear that the results from the run-up will influence the fatigue results significantly

82 LMS Virtual.Lab Durability Since we are interested in the fatigue damage of one rotation (after the run-up), we have to limit the time range for the durability calculation accordingly. Because the Motion analysis represents two rotations, the second half of the time range is a reasonable segment for our durability analysis. Double-click the "Load Function Set.1". Press the button "Time Series Options", and enter the following time range:

83 Exercise 5: System Level Fatigue Run the durability analysis and generate the desired result image(s). Note: If the color map is not visible, you can access its definition GUI via the context menu:

84 LMS Virtual.Lab Durability Exercise 6: Seam Welds This is a well-known example of two welded tubes. It is a simple geometry, but many important aspects of a seam-weld analysis can be explored. For example, the type of welding is changing along the seam from 90 T-joint to 135 Y-joint. In contrast to the durability calculations performed before, additional input namely the definition of seam welds is required to set up a seam weld analysis. Therefore, this example also shows how to identify the seam welds within a structure, define the seam welds properties, and perform a seam weld analysis. Finally, there are specific post-processing features for seam weld results. Open a new Durability Analysis document. Import the Nastran result file "tubes_quad.op2" available in the "SeamWelds" sub-directory of the training data. Use the following settings: Note: The setting "Create Mesh Groups below the Mesh Parts" leads to separate groups for each of the tubes. These groups are required for the seam weld definition; they could also be created later, but using the import option is more convenient

85 Exercise 6: Seam Welds Define the Seam Welds In the next step, we have to find the elements that are used for the seam weld definition: Select the "Find Seam Welds" command: Insert Durability for Welding Cases Find Seam Welds Select the mesh groups "PSHELL 1" and "PSHELL 2": Make sure that the "Use Changing Angle" option is enabled, and press "OK" to let the software generate the seam weld: Note: The software detects all direct connections by common nodes between two element groups. If intermediate rigid elements or intermediate shells connected the tubes, the software would also detect these as a seam weld. The software detected at each connection point the local geometry, and assigned the correct seam weld model automatically:

86 LMS Virtual.Lab Durability Double-click the seam weld "PSHELL 1 -> PSHELL 2" (either in the tree or in the 3D view). Note: In the "Edit Seam Weld" dialog, you see that "Weld Type" and "Thickness" are assigned automatically. You can double check the sheet thickness, the weld type, and further parameters of the weld. Since the durability results depend on the throat geometry and penetration grade, you should compare the geometry of the model with the geometry of the "real" weld. The "Notch Model" selected here, needs to match the SN curve selected in the Seam Weld case later. Press the "Show Details" button to display further information about the notch models: Close the weld details and the "Edit Seam Weld" window without any changes. Apply the Loads First, we create a Load Function Set for the loads

87 Exercise 6: Seam Welds Create a new Load Function Set by selecting "Time-History Load Function Set" from the "Insert" menu. Press "OK" in the window "Load Function Set" without changing any settings. Right-click on "Data Sources" (a child of the new tree entry " Load Function Set") and select "Add a Data File". Make sure that the file type is set to "Generic Time History Interface (*.*)" and select the file "Tubes_Load.asc" Make sure that the option "Create Input Points" in the "File Data Source" window is activated, and press "OK". Create a Load FE Assignment In the next step, we create a Load - FE Assignment. The Load - FE Assignment is created after the creation of Load Function Sets (LFS) and Mode Sets (MS) to combine load histories and FE results. Insert a new Load - FE Assignment by selecting the command "Load - FE Assignment" from the "Insert" menu

88 LMS Virtual.Lab Durability In the window "Insert Load - FE Assignment", select the options "Reference Load Function Set", "Reference Mode Set", and "Match by Name". Click on the existing Load Function Set and Mode Set in the specification tree, and press "OK" Set up a Seam Weld Analysis Create a seam weld analysis case (Insert Durability for Welding Cases Seam Weld Analysis Case) referring to the Load FE Assignment from the previous step and the seam weld defined before. Select the SN curve "R005MS Steel (R=-1)" from the database "Weld connections Virtual.Lab". Select the fatigue parameter "RxMS: mean stress correction, normal stress" from the database "Weld connections Virtual.Lab"

89 Exercise 6: Seam Welds Note: These data sets have been adapted to the special LMS seam weld feature, based on experience gained with this approach. The sets may be revised in future versions. Ensure in any case that the SN curve approach RxMS, where x is 005, 03 or 1 corresponds to the notch model selected in the seam weld definition. The software also executes some plausibility checks, and gives a corresponding warning if there are any inconsistencies. Start the calculation. Create an image of the fatigue damage as described before. For a clear visualization of the results on the seam welds, apply the following: Hide the tree entries "Nodes and Elements" and "Seam Welds". Double-click the damage result image, press "Options", and activate "Display elements without value"

90 LMS Virtual.Lab Durability Optional Exercises Next to the file "tubes_quad.op2", there are additional versions of the same model of welded tubes: tubes_quad_fine.op2 tubes_tria.op2 tubes_tria_fine.op2 These variants use different element types and mesh sizes, respectively. Set up seam weld analyses like before, but based on the different FE result files. This will show a big advantage of the seam weld approach of LMS Virtual.Lab, namely a small influence of the meshing on the durability results

91 Exercise 7: Spot Welds Exercise 7: Spot Welds The Spot Welds module provides a number of features for fatigue life analysis of spot welds. It detects spot welds automatically and reads the necessary parameters like sheet thickness from the FE model. For structures with many spot welds, an efficient two-step approach is state of the art. First, identify the most critical spot welds in a force-based approach (LBF or SAE method). In a second step, the critical joints are replaced automatically by local spot weld fine models improving the accuracy for these critical spot welds. With the efficient LMS algorithms for spot weld replacement it is also possible to replace all spot welds with fine models. This approach is the safer approach as it does not include a selection step, but it is also leading to longer finite element solving times. Force Based Approach (using LBF method by Rupp) Open a new document by Start Durability Durability Analysis. Import "spotwelds.op2" Insert Time-History Load Function Set Press "OK" in the window "Load Function Set" without any changes. Right-click the "Data Sources" of the Load Function Set, and select "Add a Data File". Select the file "spotweld.dmd", activate the option "Create Input Points". Insert Load FE Assignment Refer to the Load Function Set and the Mode Set, and activate the option "Match by Name". Press "OK"

92 LMS Virtual.Lab Durability Double-click the "Assignment" feature of the Load FE Assignment. Change the parameter "Load applied" for both entries to 1 Nm (1Nxm) Insert Durability for Welding Cases Spot Weld Analysis Case Refer to the Load FE Assignment in the tree, and press "OK". Complete the Spot Weld Task Definition using parameters from the database "Weld connections Virtual.Lab": Double-click on SN Curve. From the database Weld connections Virtual.Lab select the SN curve Spot Weld: Force Based Rupp st14 : Double-click on Fatigue Parameter. From the database Weld connections Virtual.Lab select the fatigue parameter Spot Weld: Force Based LBF method (Rupp). Now, everything is set up for the durability analysis of the spot welds

93 Exercise 7: Spot Welds Right click on the Durability Spot Weld Analysis Solution and select Compute. Close the Computing window after the computation has finished. Right click on the Durability Spot Weld Analysis Solution and select Generate Image. In the Image Generation window, select Fatigue Damage Spot Weld (Discontinuous), and press OK. For a clear visualization of the results on the spot welds, apply the following: Hide Nodes and Elements. Double-click the damage result image, press Options, and activate Display elements without value

94 LMS Virtual.Lab Durability Stress Based Approach (using fine models for spot welds) Open a new document by Start Structures Finite Element Analysis Pre/Post Nodes & Elements. Import "spotwelds.bdf" Import Properties Tools Properties List/Modify Properties Select the three lines with type "Shell" from the Property List, and press "Insert"

95 Exercise 7: Spot Welds Confirm the following warning. Close the "List Properties" window. Detect Spot Welds Insert Connectors New Connection Set

96 LMS Virtual.Lab Durability Tools Connectors Weld Detection Tools Spot Welds Detection Pick "Analysis Connections.1" and "Nodes and Elements" in the specification tree, and press "OK" to finish the spot weld detection. This results in a new mesh part "Bar with Rigid Spiders Connection Mesh Part.1" and a new property "Bar with Rigid Spiders Connection Property.1" in the tree

97 Exercise 7: Spot Welds Replace Spot Welds by Fine Models Insert Connectors Spot Welds Connectors Fine Durability Spot Weld Mesh Operator Select all entries in the "Spot Weld Connection List", and activate them by pressing the green checkmark

98 LMS Virtual.Lab Durability Change the parameters as follows: Number of Quads per Ring 16 Width of Ring No 1 2 mm Width of Ring No mm Note: Double click the entry you want to change in the "Spot Welds Ring Width List". Press "Apply", then close the window "Fine Durability Spot Weld Mesh Operator". At the spot weld initially modeled by bars with rigid spiders the regular mesh has been replaced by fine spot weld meshes. Run the FE Calculation After the FE mesh has been changed, the Nastran case needs to be re-run

99 Exercise 7: Spot Welds Right-click on the Nastran Static Solution and select "Compute". Note: If no Nastran installation is available, just open the prepared document "FineSpotWelds.CATAnalysis" and continue with that one. Create a Mode Set Use Start Durability Durability Analysis to activate the Durability workbench. Insert Mode Set Right-click the "Data Sources" of the Mode Set, and select "Add Solution Set or Data Feature". Pick the "Nastran Static Solution", and press "OK" to complete the Feature Selection

100 LMS Virtual.Lab Durability Create Load Function Set Insert Time-History Load Function Set Press "OK" in the window "Load Function Set" without any changes Right-click the "Data Sources" of the Load Function Set, and select "Add a Data File"

101 Exercise 7: Spot Welds Select the file "spotweld.dmd", activate the option "Create Input Points". Create Load FE Assignment Insert Load FE Assignment Refer to the Load Function Set and the Mode Set, and activate the option "Match by Name". Press "OK". Double-click the "Assignment" feature of the Load FE Assignment. Change the parameter "Load applied" for both entries to 1 Nm (1Nxm)

102 LMS Virtual.Lab Durability The Durability Spot Weld Analysis Case Insert Durability for Welding Cases Spot Weld Analysis Case Refer to the Load FE Assignment in the tree, and press "OK". Complete the Spot Weld Task Definition using the following parameters from the database "Weld connections Virtual.Lab": SN Curve Spot Weld: Stress Based Fatigue Parameter Spot Weld: Stress Based Solve the Durability Case and generate the desired result image, e.g. Select "Fatigue Damage Spot Weld (Discontinuous)" in the "Image Generation" window. Hide the mesh ("Nodes and Elements"). Hide the Generic Spot Weld Connections ("Analysis Connection Manager")

103 Exercise 7: Spot Welds Double-click the damage result image, press "Options", and activate "Display elements without value"

104 LMS Virtual.Lab Durability Exercise 8A: Vibration Fatigue Harmonic Loads This example shows a simulation of a shaker table test of a bracket. A sine sweep will be applied. It illustrates the enormous time gain in using a frequency-based approach for this analysis. An analysis in time domain leading to the same results needs approximately 1 day, whereas it is possible to perform the complete solution here in this exercise. Apply the loads The load application is done via a standard LMS modal-based forced response analysis. In this step, we define the load application point and the shape (i.e. load amplitude vs. frequency) of the load. Open the Virtual.Lab Start menu and select "Durability Durability Analysis" to open a new analysis document. Import the file "bracket_modal_analysis.op2" from the directory "Bracket" of the training data. Use the following settings: Open the "Modal Editing" by double-click, and add a viscous damping of 5% to all modes:

105 Exercise 8A: Vibration Fatigue Harmonic Loads Insert a "Modal-Based Forced Response Case" and reference the "Mode Set": Right-click on "Data Sources" (sub tree "Load Function Set" of the "ModelBased Forced Response Case"), and select "Add a Data File"

106 LMS Virtual.Lab Durability Set the file type to "Excel/Worksheet", and select the file "LoadAmpl.xls" from the directory of the "Bracket" example. Ensure that "Create Input Points" is activated: Optionally, you can create a 2D display and show the amplitude

107 Exercise 8A: Vibration Fatigue Harmonic Loads Double-click the "Forced Response Function Solution" feature to open the solution parameters. Set the "Argument Axis Definition Parameters" to "User Defined Values". Mark the "Line Step: " entry, press the "Edit " button, and enter the following frequency parameters:

108 LMS Virtual.Lab Durability Note: The frequency increment should be set depending on the resonance frequencies of the model. You can run the Modal-based Forced Response Case, and display the MPF histories in order to check for a sufficient resolution. Define the sine sweep. The sine sweep itself (frequency range and duration) is defined using a Harmonic Vibration Loads set. Here you could also add sine waves, and partial sweeps. Insert a "Harmonic Vibration" feature: Select the "Modal-based Forced Response Case" as input:

109 Exercise 8A: Vibration Fatigue Harmonic Loads Add a "Harmonic Vibration Load" to the new "Harmonic Vibration List" feature: Define the sweep parameters as follows: Setup and perform the Durability analysis Insert a Durability Strain Life Analysis Case and refer to the "Harmonic Vibration" feature

110 LMS Virtual.Lab Durability In this exercise, the Uniform Material Law (UML) will be used rather than selecting a predefined data set from material databases. The UML is an well accepted approach to estimate fatigue properties based on statistical studies. Right-click on "Material", and select "Material Created By " Activate the option "UML (Steel)", and press "Define". Enter the following material properties, and close the windows "UML (Steel)" and "Create Material" by pressing the "OK"

111 Exercise 8A: Vibration Fatigue Harmonic Loads From the "Default" database, select the fatigue parameter set "Pseudo stress, critical plane, open mode (I), no mean stress influence". Start the computation. Generate an image, and visualize the "Maximum Fatigue Damage" results as explained in the previous examples

112 LMS Virtual.Lab Durability

113 Exercise 8B: Vibration Fatigue Random Loads Exercise 8B: Vibration Fatigue Random Loads As the previous exercise, this example shows a simulation of a shaker table test of a bracket. In contrast to the calculation before, a random vibration load will be applied. Import the FE data Start with the same steps like in the previous exercise (see page 104): Open a new "Durability Analysis" document. Import the file "bracket_modal_analysis.op2". Open the "Modal Editing", and add a viscous damping of 5% to all modes. Apply the loads The load application is done via a cross power set. In this step, we define the load application point and the shape of the load (as PSD). Insert a "Crosspower Set" using the corresponding entry in the "Insert" menu or the button from the Durability Load Preparation toolbar. Make sure that the option "Same IO Points for References and Responses" is activated, and add "Acceleration" to the list of "User Defined" physical types: Right-click on the new "Crosspower Set", and select "Add Edited Crosspower Function"

114 LMS Virtual.Lab Durability Modify the window "Attributes" tab as follows: Enter "30465" as Response ID and Reference ID. Set both of the DOF options to "+Z". Select "Accelaration" as physical type for both the response and the reference. Activate "PSD Mode". Activate "Create Reference Points". Change to the "Values" tab, and enter the values as displayed in the following screenshot:

115 Exercise 8B: Vibration Fatigue Random Loads Define the Vibration Loads Insert a "Random Vibration Load Case" using the corresponding entry in the "Insert" menu or the button from the Durability Load Preparation toolbar. Refer to the existing Mode Set and Cross Power Set Select "Update" from the context menu of the "Random Vibration Response Solution Set": After the solution is completed, you may generate function displays based on the "Modal Participation Factor Power Set". The features and usage of 2D displays have been explained several times in the previous exercises. Setup and perform the Durability analysis Insert a Durability Strain Life Analysis Case and refer to the "Random Vibration Load Case" feature. Set the "Duration of Load Application" to "60s"

116 LMS Virtual.Lab Durability Right-click on "Material", and select "Material Created By " Activate the option "UML (Steel)", and press "Define". Enter the following material properties, and close the windows "UML (Steel)" and "Create Material" by pressing the "OK". Double-click the "Fatigue Parameter" entry. Select from the database "Vibration Fatigue" the parameter set "Dirlik, Pseudo stress, critical plane, open mode (I), no mean stress influence":

117 Exercise 8B: Vibration Fatigue Random Loads Start the computation. Generate an image, and visualize the "Maximum Fatigue Damage" results as explained in the previous examples

118 LMS Virtual.Lab Durability Load Attachment Advanced Features The "Manual Assignment" In cases where the naming of the channels and the IO-points are completely different the manual attachment can be used as in the following picture: For each degree of freedom, you can select a load function from the list of all load functions available. To attach a load function to a degree of freedom, press the "Assign DOF" button. Features of the "Manual Assignment" Allow all physical types: This check box allows you to enable all loads from the data sources for the attachment, regardless of their physical types. If the input load has a physical type other than the IOPoint to which it is attached, then the physical type is converted to the physical type of the IOPoint; in this case often a calibration is needed (see below). This setting affects the whole load function set, not only for a certain assignment. Calibration factor and offset The calibration factor and offset allow you to adjust the data in case you need it. Calibration is mostly needed in case you want to change the physical type of an attached load. However, you can also scale the loads without changing the physical type. When you click the "Apply" button, the calibration information is applied to the selected DOFs in the "Attached functions" list box. If there is no DOF selected when you apply the information, it is applied to all DOFs. You are only able to set calibration information to loads that are attached to a certain DOF. If you have attached a load to more than one DOF, they will always have the same calibration information

119 Mode Name Generation Mode Name Generation LMS Virtual.Lab generates mode names according to the following rules: MSC.Nastran OP2/Punch/Bulk files: static modes: "LABEL / SUBTITLE / TITLE" normal modes: "Mode: mode number, frequency / LABEL / SUBTITLE / TITLE" ANSYS RST files: static modes: "3rd Title / Subtitle / Title / 4th Title / 5th Title" normal modes: "Mode: mode number, frequency / 3rd Title / Subtitle / Title / 4th Title / 5th Title" for I-DEAS Universal Files static modes: "ID Line 3 / ID Line 2 / ID Line 1 / ID Line 4 / ID Line 5" normal modes: "Mode: mode number, frequency / ID Line 3 / ID Line 2 / ID Line 1 / ID Line 4 / ID Line 5"

120 LMS Virtual.Lab Durability Image Generation The following list gives an overview of the images available for results of LMS Virtual.Lab Durability. Damage Location For critical plane based stress and strain life analyses, this image gives angle (in degrees) to the critical plane. You can use the information if you analyze the local stress tensor histories. For seam weld results, this gives the critical notch. Design Life Factor The ratio of the design life value and the computed life is displayed. The design life can be defined in the fatigue parameter set ("General" settings). (Not available for random fatigue results.) Design Load Factor This value estimates the factor by which the load has to be changed to reach the design life, given in the parameter set ("General" settings). The value is estimated by the following process: From the computed life, a corresponding stress value S can be re-calculated using the SN curve. This stress represents the amplitude for a constant amplitude loading, which leads to the same damage. The design load factor is the ratio of this value (S) and the design stress (SD), which is calculated from the design life again using the SN curve. In case of strain life approach, the SN curve is synthetically calculated. (Not available for random fatigue results.)