3D Beam Large Deflection Analysis ME 501 Tim Allred Jon Bell June 20, 2001

Overview Objective Problem Definition Analysis Results What we learned Conclusion

Project Objective Model this mechanism in 3D Compare deflection and stress results using large deflection analysis to: –Approximate 2D pseudo rigid body model –2D beam model –3D beam model using small deflection analysis

Problem Definition Original SuspensionCompliant Suspension lbs. Designed for 8 inches of vertical motion for 500 lb force input. Cross-Sectional Shape 2.0 X in. Material: Carbon/Epoxy Composite S UT : 330 ksi E: 20.6 Mpsi

Analysis Models 2D beam large deflection 3D beam small deflection 3D beam large deflection

Results 3D w/ large displacements 3D w/ small displacements 2D modelPsuedo-rigid body results Displacement at node inches7.4 inches8.6 inches8 inches Maximum Stress 182 ksi171 ksi177 ksiN/A

Displacements 3D large displacement model 3D small displacement model 2D model 9.7 “ 7.4 “ 8.6 “

Stresses 3D large displacement model 3D small displacement model 2D model Stress distributions change Stress max =182 ksi Stress max =171 ksi Stress max =177 ksi

What we learned about ANSYS! 2 Plane Bending 3D beam Torsional Moment of Inertia –With no input, ANSYS automatically inserts polar moment of inertia or Ixx +Iyy Maximum Stress includes only Bending + Axial Stresses –Shear Stress due to Torsion not included –For correct failure analysis, user would need to calculate shear stress by hand MRMR

Conclusions 3D modeling with large displacement is necessary for accurate results on this particular problem due to the torsion introduced on the compliant member ANSYS is very useful in predicting results and learning about the important parameters of the problem Prototype would need to be built for accurate verification of results