WS16-1 WORKSHOP 16 MODAL FREQUENCY ANALYSIS OF A CAR CHASSIS NAS122, Workshop 16, August 2005 Copyright 2005 MSC.Software Corporation

WS16-2 NAS122, Workshop 16, August 2005 Copyright 2005 MSC.Software Corporation

WS16-3 NAS122, Workshop 16, August 2005 Copyright 2005 MSC.Software Corporation MODAL FREQUENCY ANALYSIS OF A CAR CHASSIS n Problem Description u For this problem, a unit force is applied to an engine mount on the car. The model is submitted to MSC.Nastran for a modal frequency response analysis with a modal damping of 1%. After the analysis is completed, the user will be asked to plot a XY Plot of displacement vs. frequency at various locations to view the effect of the load on the car over range of frequencies.

WS16-4 NAS122, Workshop 16, August 2005 Copyright 2005 MSC.Software Corporation MODAL FREQUENCY ANALYSIS OF A CAR CHASSIS n Suggested Exercise Steps 1. Import the car geometry from a Nastran Input File. 2. Create a set of RBE2 to represent the engine mount. 3. Set up a Time Dependent Load Case. 4. Create a frequency dependent field. 5. Assign a unit force load to the independent node of the RBE2 created for the engine mount. 6. Submit the model for a Normal Modes analysis. 7. Attach the XDB result file after the analysis is completed. 8. Create a graph of frequency vs. displacement of three locations on the car.

WS16-5 NAS122, Workshop 16, August 2005 Copyright 2005 MSC.Software Corporation CREATE NEW DATABASE Create a new database called car.db. a.File / New. b.Enter car_frequency_response as the file name. c.Click OK. d.Choose Default Tolerance. e.Select MSC.Nastran as the Analysis Code. f.Select Structural as the Analysis Type. g.Click OK. a b c d e f g

WS16-6 NAS122, Workshop 16, August 2005 Copyright 2005 MSC.Software Corporation Step 1. File / Import Import the model from a Nastran Input File. a.File / Import. b.Select MSC.Nastran Input as the Source. c.Select car.bdf and click Apply. d.Click OK when the Nastran Input File Import Summary appears. b c a c d

WS16-7 NAS122, Workshop 16, August 2005 Copyright 2005 MSC.Software Corporation Step 2. Elements: Transform / Node / Translate Create a node that will be used as the independent node of the RBE2. a.Elements: Transform / Node / Translate. b.Change the Starting ID to c.Enter Director Vector of. d.Select Node Please see the Figure for the Location of Node e.Click Apply. a b c d g h i Node 5691 e

WS16-8 NAS122, Workshop 16, August 2005 Copyright 2005 MSC.Software Corporation Step 2. Elements: Create / MPC / RBE2 Create a set of RBE2 to represent the engine mount. a.Elements: Create / MPC / RBE2. b.Click on Define Terms. c.Check the Create Independent option. d.Enter node in the Node List box. e.Click Apply. a b c e d

WS16-9 NAS122, Workshop 16, August 2005 Copyright 2005 MSC.Software Corporation Step 2. Elements: Create / MPC / RBE2 (Cont.) Create a set of RBE2 to represent the engine mount (cont.). a.Make sure Auto Execute is unchecked b.Select the 5 nodes nearest Node Please see the figure for the locations of the nodes. c.Select all 6 DOFs. d.Click Apply. e.Click Cancel. f.Click Apply. f b d c 5 nodes to be selected e

WS16-10 NAS122, Workshop 16, August 2005 Copyright 2005 MSC.Software Corporation Step 2. Elements: Create / MPC / RBE2 (Cont.)

WS16-11 NAS122, Workshop 16, August 2005 Copyright 2005 MSC.Software Corporation Step 3. Load Cases: Create Create a Time Dependent load case called frequency_response. a.Load Cases: Create. b.Enter frequency_response for the Load Case Name. c.Change the Load Case Type to Time Dependent. d.Click Apply. a b c d

WS16-12 NAS122, Workshop 16, August 2005 Copyright 2005 MSC.Software Corporation Step 4. Fields: Create / Non Spatial / Tabular Input Create a frequency dependent non- spatial field. a.Fields: Create / Non Spatial / Tabular Input b.Enter unit_load for the Field Name. c.Select Frequency (f) as the Active Independent Variables. d.Click on Input Data button. e.Enter the values shown in the figure. f.Click OK. g.Click Apply. a b c e f g d

WS16-13 NAS122, Workshop 16, August 2005 Copyright 2005 MSC.Software Corporation Step 5. Loads/BCs: Create / Force / Nodal Apply a unit force load on the RBE2. a.Loads/BCs: Create / Force / Nodal. b.Enter unit force for the New Set Name. c.Click on Input Data button. d.Enter for the Force vector, and select unit_load field in the Time/Freq. Dependence box. e.Click OK. f.Click Select Application Region. g.Change the Geometry Filter to FEM. h.Enter node in the Select Nodes field. i.Click Add and Click OK. j.Click Apply. a b c d e g h i i j f

WS16-14 NAS122, Workshop 16, August 2005 Copyright 2005 MSC.Software Corporation Step 5. Loads/BCs: Create / Force / Nodal (Cont.)

WS16-15 NAS122, Workshop 16, August 2005 Copyright 2005 MSC.Software Corporation Step 6. Analysis: Analyze / Entire Model / Full Run Submit the model for analysis. a.Analysis: Analyze / Entire Model / Full Run. b.Enter car_frequency_response for the Job Name. c.Click on Solution Type. d.Select FREQUENCY RESPONSE. e.Make sure the Formulation is Modal. f.Click on Solution Parameters. g.Click on Eigenvalue Extraction. h.Enter 1 for the Lower Frequency Range of Interest. i.Click OK on all three sub- forms to return to the main analysis menu. a b c d e f g h i i i

WS16-16 NAS122, Workshop 16, August 2005 Copyright 2005 MSC.Software Corporation Step 6. Analysis: Analyze / Entire Model / Full Run (Cont.) Submit the model for analysis (cont.). a.Click on Subcases. b.Select frequency_response from the Available Subcases box. c.Click on Subcase Parameters. d.Click on DEFINE FREUQENCIES. e.Enter the value and setting as shown in the table. f.Click OK. a b c d f e

WS16-17 NAS122, Workshop 16, August 2005 Copyright 2005 MSC.Software Corporation Step 6. Analysis: Analyze / Entire Model / Full Run (Cont.) Submit the model for analysis (cont.). a.Select Struct. Damp. (G) from the pull down menu. b.Click on DEFINE MODAL DAMPING. c.Click Add Row. d.Enter the values shown in the table. e.Click OK on both forms. f.Click Apply on the Subcases form. g.Click on Cancel. a b c d f e e g

WS16-18 NAS122, Workshop 16, August 2005 Copyright 2005 MSC.Software Corporation Step 6. Analysis: Analyze / Entire Model / Full Run (Cont.) Submit the model for analysis (cont.). a.Click on Subcase Select. b.Click on Default in the Subcase Select box to unselect the Default subcase. c.Click on frequency_response in the Subcases For Solution Sequence box. d.Click OK. e.Click Apply to submit the modal to Nastran for analysis. a c d e

WS16-19 NAS122, Workshop 16, August 2005 Copyright 2005 MSC.Software Corporation Step 7. Analysis: Access Results / Attach XDB / Result Entities Attach the XDB result file. a.Analysis: Access Results / Attach XDB / Result Entities. b.Click on Select Result File. c.Select car_frequency_response.xdb. d.Click OK. e.Click Apply. a b c d e

WS16-20 NAS122, Workshop 16, August 2005 Copyright 2005 MSC.Software Corporation Step 8. Results: Create / Graph / Y vs X Create a graph of displacement versus frequency. a.Results: Create / Graph / Y vs X. b.Click on frequency_response result case. c.Click on Filter. d.Click Apply. e.Click on Close. a b c d e

WS16-21 NAS122, Workshop 16, August 2005 Copyright 2005 MSC.Software Corporation Step 8. Results: Create / Graph / Y vs X (Cont.) Create a graph of displacement versus frequency (cont.). a.Select Displacement, Translational. b.Click on Target Entities Icon. c.Enter Node Please see the figure on the next page for the location of these nodes. d.Click on Display Attribute icon. e.Change the Y Axis Scale to Log. f.Click Apply. a b c d e

WS16-22 NAS122, Workshop 16, August 2005 Copyright 2005 MSC.Software Corporation Step 8. Results: Create / Graph / Y vs X (Cont.) Node 8640 Node 7858 Node 8798

WS16-23 NAS122, Workshop 16, August 2005 Copyright 2005 MSC.Software Corporation Step 8. Results: Create / Graph / Y vs X (Cont.)

WS16-24 NAS122, Workshop 16, August 2005 Copyright 2005 MSC.Software Corporation