Fatigue analysis of an automotive steering link

Fatigue analysis was performed in order to prevent fatigue failures and estimate the fatigue life of an automotive steering link, which is very critical for vehicle safety. Uniaxial specimens taken from the link tube were used for the monotonic tensile test and strain-controlled low-cycle fatigue test, which resulted in the monotonic and cyclic properties of the link material. Finite element method was employed to determine local stress and strain distributions of the link. The experimental strains at the critical locations were measured by using strain-gages in order to verify the accuracy of the finite element analysis results. Calculated local strains at the curved region of the link were close to the experimental strains within a difference of 8%. A carbon tube steel of STKM12C for the steering link exhibited cyclic softening behavior. Cyclic yield strength was about 25% lower than the monotonic yield strength. As expected by the finite element stress analysis, cracking occurred at the curved region of the tubular steering link rod and propagated circumferentially to the opposite side of the link rod, resulting in the final fracture.