Normal Modes Analysis of a Splash Shield - RD-1020
In this tutorial, an existing finite element model of an automotive splash shield will be used to demonstrate how to set up and perform a normal modes analysis. HyperMesh post-processing tools are used to determine mode shapes of the model.
The following exercises are included:
•••••
Retrieving the RADIOSS input fileSetting up the model in HyperMesh
Applying Loads and Boundary Conditions to the ModelSubmitting the jobViewing the results
Step 1: Launch HyperMesh and set the RADIOSS (Bulk Data) User Profile
1.Launch HyperMesh.
A User Profiles… Graphic User Interface (GUI) will appear. If it does not appear, go to Preferences ► User Profiles … from the menu on the top. 2.Select RADIOSS in the User Profile dialog.3.From the extended list, select Bulk Data.4.Click OK.
This loads the User Profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models in Bulk Data Format for RADIOSS and OptiStruct.
Step 2: Import a Finite Element Model File in HyperMesh
1.From the File pull-down menu on the toolbar, select Import….
An Import… tab is added to your tab menu. 2.Click
to import an FE model.
3.For the File type:, select RADIOSS (Bulk Data).4.Select the Files icon button.
A Select RADIOSS (Bulk Data) file browser will pop up.
5.Browse for sshield.fem file located in the HyperWorks installation directory under
7.Click Close to close the Import tab menu. Step 3: Review Rigid Elements Notice there are two rigid \"spiders\" in the model. They are placed at locations where the shield is bolted down. This is a simplified representation of the interaction between the bolts and the shield. It is assumed that the bolts are significantly more rigid in comparison to the shield. The dependent nodes of the rigid elements have all six degrees of freedom constrained. Therefore, each \"spider\" connects nodes of the shell mesh together in such a way that they do not move with respect to one another. file://C:\\Altair\\hw10.0\\help\\hwsolvers\\rd1020.htm2013-3-28 RADIOSS, MotionSolve, and OptiStruct Tutorials > RADIOSS > Basic Small Displa...Page 2of 6 The following steps show how to review the properties of the rigid elements. 1.From the 1D page, select the rigids.2.Click review. 3.Select one of the rigid elements in the graphics region. In the graphics window, HyperMesh displays the IDs of the rigid element and the two end nodes and indicates the independent node with an 'I' and the dependent node with a 'D'. HyperMesh also indicates the constrained degrees of freedom for the selected element, through the dof checkboxes in the rigids panel. All rigid elements in this model should have all dofs constrained. 4.Click return to go to the main menu. Step 4: Setting up the Material and Geometric Properties The imported model has three component collectors with no materials. A material collector needs to be created and assigned to the shell component collectors. The rigid elements do not need to be assigned a material. Shell thickness values also need to be corrected. 1.Select the Material Collectors toolbar button 3.Click mat name = and enter steel. 4.Select the desired color for the material steel by clicking on 5.Click card image = and select MAT1 from the pop-up menu.6.Click create/edit. The MAT1 card image pops up. 7.For E, enter the value 2.0E5.8.For NU, enter the value 0.3.9.For RHO, enter the value 7.85E-9. If a quantity in brackets does not have a value below it, it is off. To change this, click the quantity in brackets and an entry field will appear below it. Click in the entry field, and a value can be entered. 10.Click return. A new material, steel, has now been created. The material uses RADIOSS linear isotropic material model, MAT1. This material has a Young's Modulus of 2E+05, a Poisson's Ratio of 0.3 and a material density of 7.85E-09. A material density is required for the normal modes solution sequence. At any time the card image for this collector can be modified using Card Editor. 11.Click return to exit the Material Createpanel.12.Select the Card Editor toolbar button . . . 2.Select the create subpanel using the radio buttons on the left-hand side of the panel. 13.Click the down arrow on the right of the entity shown in the yellow box, select props from the extended entity list.14.Click the yellow props button and then check the box next to design and nondesign.15.Click select. 16.Make sure card image=is set to PSHELL.17.Click edit. The PSHELL card image for the design component collector pops up. 18.Replace 0.300 in the T field with 0.25. 19.Click return to save the changes to the card image.20.Click return to go to the main menu. file://C:\\Altair\\hw10.0\\help\\hwsolvers\\rd1020.htm2013-3-28 RADIOSS, MotionSolve, and OptiStruct Tutorials > RADIOSS > Basic Small Displa...Page 3of 6 Applying Loads and Boundary Conditions to the Model (Steps 5 - 7) The model is to be constrained using SPCs at the bolt locations, as shown in the following figure. The constraints will be organized into the load collector 'constraints'. To perform a normal modes analysis, a real eigenvalue extraction (EIGRL) card needs to be referenced in the subcase. The real eigenvalue extraction card is defined in HyperMesh as a load collector with an EIGRL card image. This load collector should not contain any other loads. Step 5: Create EIGRL card (to request the number of modes) 1.Click the Load Collectors toolbar button 3.Click loadcol name = and enter EIGRL. 4.Click card image= and select EIGRL from the pop-up menu.5.Click create/edit. 6.For V2, enter the value 200.000.7.For ND, enter the value 6. If a quantity in brackets does not have a value below it, it is off. To change this, click on the quantity in brackets and an entry field will appear below it. Click on the entry field, and a value can be entered. 8.Click return to save changes to the card image. . 2.Select the create subpanel, using the radio buttons on the left-hand side of the panel. Step 6: Create Constraints at Bolt Locations 1.Click loadcol name = and enter constraints. 2.Click the switch next to card image and select no card image.3.Click create > return. 4.From Analysis page, click the constraintspanel and make sure that the create subpanel is active. Selecting nodes for constraining the bolt locations 5.Select the two nodes, shown in the figure above, at the center of the rigid spiders, by clicking on them in the graphics window.6.Constrain all dofs with a value of 0.0.7.Click Load Type= and select SPC.8.Click create file://C:\\Altair\\hw10.0\\help\\hwsolvers\\rd1020.htm2013-3-28 RADIOSS, MotionSolve, and OptiStruct Tutorials > RADIOSS > Basic Small Displa...Page 4of 6 Two constraints are created. Constraint symbols (triangles) appear in the graphics window at the selected nodes. The number 123456 is written beside the constraint symbol, if the label constraints is checked ‘ON’, indicating that all dofs are constrained. 9.Click return to go the main menu. Step 7: Create a Load Step to perform Normal Modes Analysis 1.From the Analysis page, enter the loadstepspanel.2.Click name = and enter bolted. 3.Click the type: switch and select normal modesfrom the pop-up menu.4.Check the box preceding SPC. An entry field appears to the right of SPC. 5.Click on the entry field and select constraintsfrom the list of load collectors.6.Check the box preceding METHOD(STRUCT). An entry field appears to the right of METHOD. 7.Click on the entry field and select EIGRLfrom the list of load collectors.8.Click create. A RADIOSS subcase has been created which references the constraints in the load collector constraintsand the real eigenvalue extraction data in the load collector EIGRL. 9.Click return to go to the main menu. Submitting the Job Step 8: Running Normal Modes Analysis 1.From the Analysis page, enter the RADIOSSpanel.2.Click save as… following the input file:field. A Save file… browser window pops up. 3.Select the directory where you would like to write the file and, in File name:, enter sshield_complete.fem.4.Click Save. Note that the name and location of the sshield_complete.fem file shows in the input file: field. 5.Set the export options:toggle to all. 6.Click the run options: switch and select analysis.7.Set the memory options: toggle to memory default.8.Click Radioss. This launches the RADIOSS job. If the job was successful, new results files can be seen in the directory where the RADIOSS model file was written. The sshield_complete.out file is a good place to look for error messages that will help to debug the input deck if any errors are present. The default files written to your directory are: sshield_complete.html sshield_complete.out HTML report of the analysis, giving a summary of the problem formulation and the analysis results. RADIOSS output file containing specific information on the file set up, the set up of your optimization problem, estimates for the amount of RAM and disk space required for the run, information for each optimization iteration, and compute time information. Review this file file://C:\\Altair\\hw10.0\\help\\hwsolvers\\rd1020.htm2013-3-28 RADIOSS, MotionSolve, and OptiStruct Tutorials > RADIOSS > Basic Small Displa...Page 5of 6 for warnings and errors. sshield_complete.h3d sshield_complete.stat Hyper 3D binary results file. Summary of analysis process, providing CPU information for each step during analysis process. Review the Results using HyperView Eigenvector results are output by default, from RADIOSS for a normal modes analysis. This section describes how to view the results in HyperView. Step 9: Load the Model and Result Files into the Animation Window In this section, you will load a HyperView .h3d file into the HyperView animation window. 1.Click the HyperView button in the RADIOSSpanel. HyperView is launched and the sshield_complete.h3d file is loaded. 2.Click Close to exit the Message Log menu that appears. Step 10: View Eigen Vectors It is helpful to view the deformed shape of a model to determine if the boundary conditions have been defined correctly and also to check if the model is deforming as expected. In this section, use the Deformed panel to review the deformed shape for last Mode. 1.Click on the switch next to the traffic light signal2.Select the Deformed toolbar button 4.Set Scale: to Model units. 5.Set Type: to Uniform and enter in a scale factor of 10 for Value:. This means that the maximum displacement will be 10 modal units and all other displacements will be proportional. Using a scale factor higher than 1.0 amplifies the deformations while a scale factor smaller than 1.0 would reduce them. In this case, we are accentuating displacements in all directions. . and select Modal . 3.Leave Result type: set to Eigen Mode (v). 6.Click Apply. 7.Under Undeformed shape:, set Show: to Wireframe. A deformed plot of the model overlaid on the original undeformed mesh is displayed in the graphics window. 8.From the Graphics pull-down menu, select Select Load Case to activate the Load Case and Simulation Selection dialog, as shown below. file://C:\\Altair\\hw10.0\\help\\hwsolvers\\rd1020.htm2013-3-28 RADIOSS, MotionSolve, and OptiStruct Tutorials > RADIOSS > Basic Small Displa...Page 6of 6 9.Select Mode 6 - F=1.496557E+02 from the list and click OKto view Mode 6.10.To animate the mode shape, click the animation mode: modal . 11.To control the animation speed, use the Animation Controls accessed with the director’s chair toolbar button . 12.You could also review the rest of the mode shapes. Step 11: A few points to be noted In this analysis, it was assumed that the bolts were significantly stiffer than the shield. If the bolts needed to be made of aluminum and the shield was still made of steel, would the model need to be modified, and the analysis run again? It is necessary to push the natural frequencies of the splash shield above 50 Hz. With the current model, there should be one mode that violates this constraint: Mode 1. Design specifications allow the inner disjointed circular rib to be modified such that no significant mass is added to the part. Is there a configuration for this rib within the above stated constraints that will push the first mode above 50 Hz? See tutorial OS-2020 to optimize rib locations for this part. Go To RADIOSS, MotionSolve, and OptiStruct Tutorials file://C:\\Altair\\hw10.0\\help\\hwsolvers\\rd1020.htm2013-3-28
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