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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 DefinitionOriginal Suspension Compliant Suspension
14.6
16
6.5
500 lbs.
Designed for 8 inches of vertical motion for 500 lb force input.
Cross-Sectional Shape
2.0 X 0.215 in.
Material: Carbon/Epoxy Composite
SUT: 330 ksi
E: 20.6 Mpsi
1
5
2
76
4
3
Analysis Models
• 2D beam large deflection
• 3D beam small deflection• 3D beam large deflection
9
8
76
5 4
321
Results 3D w/ large
displacements3D w/ small
displacements2D model Psuedo-rigid body
results
Displacement at node 7
9.7 inches 7.4 inches 8.6 inches 8 inches
Maximum Stress
182 ksi 171 ksi 177 ksi N/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
Stressmax=182 ksi Stressmax=171 ksi Stressmax=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
MR
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