adams其他教程adams接触

1、Contact Modeling in ADAMSTodd McDevitt, Ph.D., P.E.,July 25, 2000,Problem Description,EOM,Rigid Body 2,Rigid Body 1,Plus unilateral contact conditions,Contact Kinematics,Gap function,Rigid Body 2,Rigid Body 1,R3,O,Contact basis,Unilateral Normal Contact Constraints,Kuhn-Tucker complimentary conditio

2、ns,no penetration,compressive normal contact force,no penetration, no force,persistency condition,Unilateral Normal Contact Constraints,IDEA: variational inequality variational equality CHOICES: Lagrange Multipliers enforces the contact constraints exactly difficult to implement Penalty Regularizati

3、on introduces errors into contact constraints easy to implement has physical interpretation,Penalty Regularization,Introduce the scalar quantity kn . As , the constraint error .,constraint error,IMPACT Function,IMPACT=,viscous damping contribution,Rigid Body 2,Rigid Body 1,IMPACT Function,IMPACT=,wo

4、rking range,unfriendly derivative,n 1,n = 1,n 1,Normal Contact Parameters,For true rigid body contact k = as large as possible with out introducing ill-conditioning n = 1 cmax = 0,Normal Contact Parameters,The IMPACT function allows the analyst to introduce a local, 1D deformable continuum model at

5、the contact interface. Consider the Hertzian solution for two contacting spheres:,Rigid Body 2,Rigid Body 1,Normal Contact Parameters,A contact force model with hysteresis damping can also be considered.,Rigid Body 2,Rigid Body 1,Reference: H.M. Lankarani and P.E. Nikravesh, “Continuous Contact Forc

6、e Models for Impact Analysis in Multibody Systems”, Nonlinear Dynamics, 5: 193-207, 1994.,Outline,Introduction then click OK. From the File Import dialog box, enter ppm.cmd in the File to Read field check the Update Screen box uncheck the Display Model Upon Completion box,Workshop: Pawl to Gear Toot

7、h Contact,You are viewing the gear tooth - parking pawl interface The model is complete except for a curve-to-curve unilateral contact constraint between the RED gear tooth and the parking pawl. YOUR TASK: create this missing contact constraint.,3 Steps to Automatic Contact Constraints,Define geomet

8、ry. points, curves, circles, planes, spheres Define contact force element. Select type of contact manifold, i.e, plane, curve, etc. Identify contact manifolds. Verify outward normals. Define contact force parameters. Define normal and frictional force parameters.,Workshop: Pawl to Gear Tooth Contact

9、,Create surrogate spline Access Geometric Modeling panel. Build - Bodies/Geometries Select the Spline tool . Add a closed spline to an existing part. Pick the body: gear. Pick 8 arbitrary points with the left mouse button. Create (end) with right mouse button.,Workshop: Pawl to Gear Tooth Contact,Ed

10、it spline Access Modify Geometric Spline panel. Right click on surrogate spline. Select Bspline: GCURVE_27471 - Modify from the cascading menus.,Workshop: Pawl to Gear Tooth Contact,Edit spline control points Click on to access point Location Table. Click on and select file bspline_t8.dat. Click on

11、OK in the Location Table panel.,Before,After,Remark: Curve data must be in x-y plane relative to reference marker.,Workshop: Pawl to Gear Tooth Contact,Edit spline Click on to recalculate segments. Change reference marker to .park.gear.MAR4197223. Click on OK in the Modify Geometric Spline panel.,Wo

12、rkshop: Pawl to Gear Tooth Contact,Modify spline tension Build - Data Elements - Curve - Modify. Select CURVE_3 from the Database Navigator. Change the Tension field from 0.05 to 7. Click on OK.,3 Steps to Automatic Contact Constraints,Define geometry. points, curves, circles, planes, spheres Define

13、 contact force element. Select type of contact manifold, i.e, plane, curve, etc. Identify contact manifolds. Verify outward normals. Define contact force parameters. Define normal and frictional force parameters.,Workshop: Pawl to Gear Tooth Contact,Access the “Create Contact Force” panel Zoom in/ou

14、t until red tooth and pawl are visible. From the Main Toolbox, from the Create Forces tool stack, select the Contact force tool .,Workshop: Pawl to Gear Tooth Contact,Create Contact Force panel Select type Curve to Curve. Right click in the First Curve field, select Bspline-Guesses-GCURVE_27471 from

15、 the cascading menus. Right click in the Second Curve field, select Bspline-Pick. Then right click near the Pawl. From the pop-up Select panel, choose Pawl.GCU14496.,Workshop: Pawl to Gear Tooth Contact,Examine outward normals on Bsplines Zoom in on tooth. Note that the white outward normal on park.

16、gear.GCURVE_27471 is in opposite direction. Negate it with the outward normal direction switch tool Zoom in on pawl. Note that outward normal is correct.,3 Steps to Automatic Contact Constraints,Define geometry. points, curves, circles, planes, spheres Define contact force element. Select type of co

17、ntact manifold, i.e, plane, curve, etc. Identify contact manifolds. Verify outward normals. Define contact force parameters. Define normal and frictional force parameters.,Workshop: Pawl to Gear Tooth Contact,Create Contact Array Right mouse click the Contact Array field; select contact_array-Create

18、. Fill out the Create Contact Array panel as shown. Click OK on Create Contact Array panel. Click OK on Create Contact Force panel.,Workshop: Pawl to Gear Tooth Contact,Simulate model From the main menu; select Simulate-Scripted Controls. Verify that the Simulation Script Name field reads park.SIM_S

19、CRIPT_1. Click on the Start simulation button . When the analysis is complete, review the animation. Click on the animation tool . Click on the “animation: forward” button .,Outline,Introduction increase until insignificant deviation in results or specific stiffness values are met.,Numerical Issues

20、& Debugging,Time integration Use small time steps, decrease HMAX. improves contact detection algorithms improves predictor and convergence behavior Use SI2. SI2 employs velocity error checking SI2 is generally more expensive,Outline,Introduction & Motivation Theoretical Background Contact Modeling in ADAMS/VIEW Workshop: Pawl to Gear Tooth Contact Friction Numerical Issues & Debugging Contact Models Concluding Remarks,ADAMS Contact Elements Achievements/Shortcomings,Achievements robust 2D contact capabili