Moonbuggy Rear Suspension Analysis ME450: Computer-Aided Engineering Analysis Department of Mechanical Engineering, IUPUI Instructor: Dr. Koshrow Nematollahi May 1, 2006 John Fearncombe Brandin Ray Amber Russell

Objectives Perform finite element analysis of moon buggy suspension using ANSYS Workbench Evaluate stress and deformation resulting from applied load Perform iterations as needed until a satisfactory design is realized

Introduction Moon buggy originally designed in Spring 2005 by ME 462 design team Lower a-arms on original suspension failed Normal loading conditions were determined to be approximately 200 pounds-force The initial design was modeled to determine if it could be modified and safely used

Theoretical Background Utilized ten-node SOLID92 tetrahedral elements Ideal for complicated solids with curved boundaries

Model Details for Existing Design Originally modeled in Pro/Engineer (IGES), then imported into ANSYS Workbench Static analysis only Aluminum alloy construction 200 pounds-force load applied at shock mount Fixed supports at axes of rotation Displacement constrained in transverse direction

ANSYS Workbench Model of Existing Design

Deformed Geometry for Existing Design Maximum Deflection of 2.78×10 -3 inches Maximum deformation occurs near shock absorber mount

Principal Stresses for Existing Design Maximum principal stress of ksi Yield stress for 6061 aluminum alloy is 35 ksi Maximum stresses occur where the part failed

Shear Stress for Existing Design Maximum shear stress of ksi Deemed insignificant Failure due to fatigue in aluminum

Model Details for First Iteration Modeled and constrained as before Aluminum alloy construction 200 pound-force load again applied at shock mount Modeled as one-piece construction with no welds

Results - ANSYS Model of First Iteration

Deformed Geometry for First Iteration Maximum Deflection of 5.42×10 -3 inches Occurs below shock absorber mounting bolt

Principal Stresses for First Iteration Maximum principal stress of psi Yield stress for 6061 aluminum alloy is 35 ksi Maximum stresses occur near the shock absorber mounting bolt

Shear Stress for First Iteration Maximum shear stress of psi Shear stress concentrated near welds Quality of welds had been an issue

Model Details for Final Iteration Modeled and constrained as before Aluminum alloy construction with steel reinforcement plates at shock absorber mount Two points of attachment to wheel hub housing to relieve stress on aluminum members

ANSYS Workbench Model of Final Iteration

Deformed Geometry for Final Iteration Maximum Deflection of.114×10 -3 inches Located at mid- section of shock absorber bolt

Principal Stresses for Final Iteration Maximum principal stress of ksi Yield stress: –6061 aluminum alloy is 35 ksi –4140 steel is 45 ksi Maximum stresses occur in the steel reinforcing plates

Shear Stress for Final Iteration Maximum shear stress of ksi Located in steel reinforcing plates Achieved objective of localizing stresses within steel elements

Impact Statement Through the use of finite element analysis on the rear suspension of the moon buggy the vehicle has become more safe, stable, and easier to maintain. By optimizing the design before production, we have alleviated costly and potentially dangerous failures.

Conclusion - Advantages of Final Iteration Maximum stress is distributed on steel reinforcing plates Ability to quickly and inexpensively replace the parts most likely to fail Easier fabrication No reliance on welds for structural stability

Suspension Test

Bibliography ME 450 Course Text ANSYS Website Car Suspension and Handling. Bastow, Donald. London : Pentech Press ; Warrendale, Penn. : Society of Automotive Engineers, Chassis design : principles and analysis Milliken, William F., – Material Propertieswww.engineersedge.com