Experimental stress analysis of a shock absorber's helicoidal spring
Physical experimentation included cleansing and polishing of metallic surfaces for adhesion of Omega strain gauges, as well as electrical setup for data acquistion of strain and then calculation of stress of the spring in compression.
Afterwards, I compared and verified the experimental results with FEA simulations with the same load, and to hand calculations done using the energy theory developed by Castigliano.
Shock absorbing spring
Cold Drawn High Carbon Steel ASTM A227
Loading scenarios for the spring include 200lb (1/5 of 1000 estimate for a Nissan vehicle) in torsion and bending. Even though helicoidal springs are designed to withstand high shear stresses, the axial stress due to compression won't be ignored.
Theoretical analysis
Bending moment and torsion formula development
P is the 200lb load, and R corresponds to the radius of every ring of the spring
FEA Simulation
- Model
- Deformation
- Principal stress
- Shear stress
Comparing hand calculations to FEA simulation results:
Experimentation
Placed strain gauges to measure torsion, placed at an angle of 45 degrees, and bending, placed at 0 degrees
Comparing analytical results to experimental reading
Experimental loading was reduced to 115.5 lb due to testing constraints
