Abaqus CAE (ver. 6.12) Impact tutorial

Transcription

1 Abaqus CAE (ver. 6.12) Impact tutorial Problem Description An aluminum part is dropped onto a rigid surface. The objective is to investigate the stress and deformations during the impact Hormoz Zareh 1 Portland State University, Mechanical Engineering

2 Analysis Steps 1. Start Abaqus and choose to create a new model database 2. In the model tree double click on the Parts node (or right click on parts and select Create) 3. In the Create Part dialog box (shown above) name the part Bracket a. Select 3D b. Select Deformable c. Select Solid d. Set approximate size = 200 e. Click Continue 4. Create the geometry shown below (not discussed here). Dimensions are in millimeters. a. Extrude the shape to a depth of Hormoz Zareh 2 Portland State University, Mechanical Engineering

3 5. In the Create Part dialog box (shown above) name the part Rigid a. Select 3D b. Select Analytical rigid c. Set approximate size = 200 d. Click Continue 6. Create the geometry shown below (not discussed here). Dimensions are in millimeters. a. Set the extrusion depth to 200 mm. 7. Create a datum point at the center of the plate (midway between diagonal points). 8. From the menu bar select Tools Reference Point 2013 Hormoz Zareh 3 Portland State University, Mechanical Engineering

4 a. Select the datum point just created. b. The reference point will be created as shown. 9. Create a surface on the rigid plate. a. Click on the Tools Surface Create b. Select the rigid plate. c. You will be prompted to pick a side for internal faces. Pick the color that is likely candidate as the impact surface. In this example, Brown has been selected. 10. Double click on the Materials node in the model tree a. Name the new material Aluminum and give it a description b. Click on the Mechanical tab Elasticity Elastic c. Define Young s Modulus and the Poisson s Ratio (use SI (mm) units) i. Young s modulus = 70e3, Poisson s ratio = 0.33 d. Since this is an explicit model, material density must also be defined e. Click on the General tab Density i. Density = 2.6 e 6 f. Click OK 2013 Hormoz Zareh 4 Portland State University, Mechanical Engineering

5 11. Double click on the Sections node in the model tree a. Name the section bracket_sec and select Solid for the category and Homogeneous for the type b. Click Continue c. Select the material created above (Aluminum) and Click OK 12. Expand the Parts node in the model tree, expand the node of the part Bracket, and double click on Section Assignments a. Select the entire geometry in the viewport and press Done in the prompt area b. Select the section created above (bracket_sec) c. Click OK 2013 Hormoz Zareh 5 Portland State University, Mechanical Engineering

6 13. Expand the Assembly node in the model tree and then double click on Instances a. Select Dependent for the instance type b. Select the parts: Bracket and rigid c. Select Auto offset from other instances d. Click OK 14. Now, rotate the bracket so that the impact will occur at the lower right corner. This will ba accomplished by rotating the object first with respect to the z axis followed by rotation about x axis. a. Select Rotate Instance icon. b. Select the Bracket c. Accept the default values of starting point (0,0,0) by pressing Enter d. Enter (0,0,1) for the end point of rotation axis. e. Enter 15 (degrees) for Angle of Rotation. The assembly should look similar to the screen shot below. Be sure to confirm the final rotated position by clicking on OK at the prompt region! 15. Now, rotate the bracket about the x axis. a. Select Rotate Instance icon. b. Select the Bracket c. Accept the default values of starting point (0,0,0) by pressing Enter d. Enter (1,0,0) for the end point of rotation axis. e. Enter 15 (degrees) for Angle of Rotation. Be sure to confirm the final rotated position by clicking on OK at the prompt region! 2013 Hormoz Zareh 6 Portland State University, Mechanical Engineering

7 The assembly should look similar to the screen shot below. 16. In the toolbox area click on the Translate Instance icon a. Select the Bracket geometry, click Done b. Select the bottom corner of the bracket as shown. c. Select the reference point on the Rigid member as the end point. d. Click Ok e. The completed assembly should now look like is shown below Hormoz Zareh 7 Portland State University, Mechanical Engineering

8 17. Double click on the Steps node in the model tree a. Name the step, set the procedure to General, select Dynamic, Explicit, and click Continue b. On the Edit Step page under the Basic tab, set the time period to 0.02 seconds. 18. Double click on the BCs node in the model tree a. Name the boundary condition fix_rigid_plate and select Symmetry/Antisymmetry/Encastre for the type. b. Select the reference point on the bracket geometry and click Done c. Select ENCASTRE for the boundary condition and click OK 19. Open Field Output Requests node in the model tree a. Double click on the F Output 1. b. Change the value of Interval to 100. This allows for capturing of more output increments so that impact can be better visualized. c. You may wish to also change the History output Requests to allow for better resolution of history output plots Hormoz Zareh 8 Portland State University, Mechanical Engineering

9 20. Select the Create Predefined Field icon under the Load module. a. Name the predefined field. b. Pulll down Initial step under the Step selection (see figure). c. Set the Category to Mechanical and be sure Velocity is selected. d. Note the prompt region asks you to select the regions. e. Rotate the image on the screen so that the bracket can be highlighted. Be sure the rigid plate is not selected! f. Click Done in the prompt region. g. When prompted, Enter 500 [mm/s] in the V2 field of the Edit Predefined Field window. The velocity vectors should now be displayed on the screen Hormoz Zareh 9 Portland State University, Mechanical Engineering

10 21. Double click on the Interaction Properties node in the model tree a. Name the interaction properties and select Contact for the type, click Continue b. On the Mechanical tab Select Tangential Behavior i. Set the friction formulation to Penalty ii. Set Friction Coefficient to 0.5 c. On the Mechanical tab Select Normal Behavior d. Accept defaults, Click OK 22. Double click on the Interactions node in the model tree a. Name the interaction, select General Contact (Explicit) (Explicit) and click Continue b. Select All* with self on the Edit Interactions Window. c. Be sure to assign the appropriate interaction property under Global Property assignment in the Contact Properties tab of the window. d. Change the contact interaction properties to the one created above (if not already done) e. Click OK 2013 Hormoz Zareh 10 Portland State University, Mechanical Engineering

11 23. Open the Field Ouput 1 and change the Interval for the output request to In the model tree double click on Mesh for the Bracket part, or use the Module section of the icon panel as shown. a. Select Explicit for element type b. Select Quadratic for geometric order c. Select 3D Stress for family d. Select Tet tab and be sure the element is C3D10M e. Select OK You may check the Mesh Control to be sure only TET elements are being used in meshing. 25. In the toolbox area click on the Seed Part icon a. Under Sizing Controls set Approximate global size to 2, Click OK 26. In the toolbox area click on the Mesh Part icon 2013 Hormoz Zareh 11 Portland State University, Mechanical Engineering

12 a. Click Yes Caution: The mesh will exceed the ability of student version of the software to solve. You need to use either Academic version or the Research version to be able to run the job. 27. In the model tree double click on the Job node a. Name the job b. Give the job a description, click Continue c. Accept defaults, click OK 28. In the model tree right click on the job just created and select Submit a. While Abaqus is solving the problem right click on the job submitted, and select Monitor b. In the Monitor window check that there are no errors or warnings i. If there are errors, investigate the cause(s) before resolving ii. If there are warnings, determine if the warnings are relevant, some warnings can be safely ignored. An example is information warning message below: The option *boundary,type=displacement has been used; check status file between steps for warnings on any jumps prescribed across the steps in displacement values of translational dof. For rotational dof make sure that there are no such jumps. All jumps in displacements across steps are ignored 2013 Hormoz Zareh 12 Portland State University, Mechanical Engineering

13 29. In the model tree right click on the submitted and successfully completed job, and select Results To see the effect of impact, you can either animate the deformed shape, or step through each time step of the solution. Here the step by step method is discussed. a. In the toolbox area click on the following icons i. Plot Contours on Deformed Shape ii. Switch to the First step of the solution. iii. Click on the Next step. iv. Repeat a few times and observe the change in the stress contours, and also be sure the contact does not extend into the rigid surface. You all also notice that the Bracket will start to separate from the rigid plate! 2013 Hormoz Zareh 13 Portland State University, Mechanical Engineering

14 32. You may also wish to see the behavior of the system energy, specifically making sure the artificial strain energy is not a substantial percentage of the overall (Internal) energy of the system. a. Click on the Create XY Data icon. b. Be sure the Source is ODB History output then click Continue c. Hold the CTRL key and select the energy terms you wish to plot. IN the example below Internal and Artifical energy terms have been selected. You ll note that Artificial Energy is a very small portion of the overall Internal Energy, thus the model seems to be valid, at least from the standpoint of element behavior and possibility of errors due to meshing Hormoz Zareh 14 Portland State University, Mechanical Engineering