Low Cycle Fatigue Characteristics of SPHC Hot-rolled Steel Sheet for Automobile

Low cycle cyclic strain fatigue test was carried out on 2.0 mm thick SPHC hot-rolled steel sheet for automobile, and the stress-strain curve, strain-life curve, strain hysteresis loop curve and related fatigue constant indicators were obtained. The fatigue fracture morphology was observed. The results show that the SPHC steel had a non-Masing effect within the test range. The fitted cyclic strength coefficient of SPHC steel was 284, and cyclic strain-hardening exponent was 0.128. The fatigue strength coefficient was 467 MPa, the fatigue strength index was -0.078, the fatigue ductility coefficient was 0.323, and the fatigue ductility index was -0.609 fitted by Manson-Coffin equation. The fatigue fracture included crack source area, crack propagation area, and transient fracture area. The crack propagation area was composed of a large number of fatigue striation, and the transient fracture area consisted of a large number of dimples. SPHC steel had good ductility.