The effects of strain amplitude and low cycle fatigue (LCF) behavior on nodular cast iron with two-step austempering (TSA) process

Abstract

The strain amplitude analysis of low cycle fatigue (LCF) on nodular cast iron processed with TSA aimed to observe the fatigue behavior and fatigue cracking phenomenon until the failure. The LCF test followed the ASTM A606 standard and it was performed at room temperature with strain ratio = −0.1, strain rate 2.5 × 10–3s−1, various strain amplitudes of 0.002, 0.0025, 0.00275 and 0.003 mm mm−1, and TSA holding time of 5, 10, and 15 min. LCF test results were shown in the hysteresis loops curve (s versus e) and peak stress versus number of cycle curve. LCF test showed that the 0.0025 mm mm−1 strain amplitude at 5- and 10-minutes TSA generated the highest cycles compared to 0.002, 0.00275 and 0.003 strain amplitudes. The 0.0025 strain amplitude and 5 min TSA had 10845 cycles and 10 min TSA had 7414 cycles. Therefore, 0.002, 0.00275 and 0.003 strain amplitudes had total cycles which were below the above cycles.