1. Finite Element Analysis of the Steel Horse Rear Suspension Presented by: Erika Ramirez April 29, 2003

2. Problem Statement The rear suspension of any mini baja car must be able to withstand the rough terrains associated with the competitions motor cross track. The rear suspension of any mini baja car must be able to withstand the rough terrains associated with the competitions motor cross track. The objective of this project is to successfully analyze the rear suspension with an impact load at the rear of the tire. The objective of this project is to successfully analyze the rear suspension with an impact load at the rear of the tire.

3. Problem Formulation The rear suspension to be analyzed is a single a-arm. It is made out of 4130 Chromoly tubing with an outer diameter of 1 and thickness of.058. The rear suspension to be analyzed is a single a-arm. It is made out of 4130 Chromoly tubing with an outer diameter of 1 and thickness of.058.

4. Impact Force Another car traveling at 30 mph hits our car and comes to rest at one second or the car hits an object traveling at 30MPH form the side: Vi=30 MPH Vf=0 MPH t=1s m=600lb Vf=Vi+ata(impact)=Vf-Vi/tF=m*a(imp) F = 820 lbf

5. Worst Case Scenario The car lands in one tire. The car lands in one tire. Weight of the vehicle (600 lbs) Weight of the vehicle (600 lbs) The tire hits a rock, bump, etc. The tire hits a rock, bump, etc. Use the 820 lbf load Use the 820 lbf load Use an Actuator to model the motor – cross track Use an Actuator to model the motor – cross track

6. Material Properties Density Density.284 lb/in^3.284 lb/in^3 Modulus of Elasticity Modulus of Elasticity 205 GPa 205 GPa Yield Stress Yield Stress 8e8 Pa 8e8 Pa UTS UTS 9.65e9 Pa 9.65e9 Pa

7. Pro-E Model REVOLUTE JOINTS ACTUATOR IMPACT FORCE = 820 lb SPRING/DAMPER (SHOCK) – 175 lb/in and C=10.2

8. Finite Element Modeling (Stresses) Concentration of Stresses located at the revolute joints. Concentration of Stresses located at the revolute joints.

9. Displacements Max Displacement occurs at the Hub tabs near the tire – also at one of the revolute joints.

10. Factor of Safety

11. Making the ends.01 thicker Von Misses Stresses

12. Modified Displacements

13. Modified Factor of Safety

14. Comparing Stresses The Maximum Principle Stresses are greatly reduced by making the revolute joints.01 thicker.

15. Comparing Displacements Displacements were increased a little from.75891 to.82149 in.

16. Von Misses Stresses Von Misses stresses were also reduced.

17. Comparing Factor of Safety Minimum Factor of Safety was increased – and there are less areas of concern.

18. Comments / Summary H-Adaptivity was not used because of the complexity of the part. H-Adaptivity was not used because of the complexity of the part. The Mesh size used was.02 Feet, this was done after converging on the same maximum value of stresses (no significant change for a smaller mesh size). The Mesh size used was.02 Feet, this was done after converging on the same maximum value of stresses (no significant change for a smaller mesh size). A simple way to reduce the stress concentrations would be to introduce more material on the revolute ends. A simple way to reduce the stress concentrations would be to introduce more material on the revolute ends.

19. Questions?