The objective of the study was to evaluate the quasi-static and fatigue
performance of automotive anti-roll bars (ARBs) under extreme environmental
conditions. Flexural quasi-static and fatigue tests of SAE 1040 steel were
conducted above and below the ductile-to-brittle transition temperature (DBTT)
in flexure and compared with their room temperature performance. The flexural
strength increased by decreasing the temperature to −40°C. The fatigue lives are
determined for stress levels of 87%, 60%, and 30% of their flexural strength
under displacement mode in constant amplitude loading. Experimental stress
versus the number of cycles (S-N) curves of SAE 1040 steel state that all tube
specimens have fatigue limits that were more than 100,000 cycles at −40°C. The
fatigue life of the SAE 1040 tube exhibited infinite life below the
ductile-to-brittle transition (DBT). The finite element (FE) model of ARB was
used to determine the quasi-static strength, as well as in the calculation of
fatigue analysis. The FE fatigue life predictions of all stress levels match the
experimental results. Fractography of failed specimens revealed cleavage
fractures resembling river patterns at −40°C, followed by the fine steps feather
marking, tear ridges, decohesion, transgranular fractures, etc. in subsequent
DBTTs, i.e., −30°C to +10°C of quasi-static testing. The flexural fatigue
fracture surface analysis showed that the mechanisms at −40°C were quite
distinct, involving transgranular cracks with dislocation strengthening.
