Moonbuggy Rear Suspension Analysis

ME450: Computer-Aided Engineering Analysis

Department of Mechanical Engineering, IUPUI

Instructor: Dr. Koshrow NematollahiMay 1, 2006

John FearncombeBrandin RayAmber 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 1.791 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 1.421 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 221.267 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 20.917 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 1.875 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 1.170 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 www.ansys.com• Car Suspension and Handling. Bastow,

Donald. London : Pentech Press ; Warrendale, Penn. : Society of Automotive Engineers, 1993.

• Chassis design : principles and analysis Milliken, William F., 1911-

• www.engineersedge.com – Material Properties