The influence of inclusion factors on ultra-high cyclic deformation of a dual phase steel

Abstract

The ultra-high cycle fatigue test of a dual phase steel was carried out using ultrasonic fatigue vibration system, and the fatigue fracture surface was observed by SEM to reveal crack origin sites that indicated the presence of inclusions. Second, the influence of inclusions on the ultra-high cycle fatigue behavior was studied by considering characteristic parameters of inclusions. Experimental results showed that the tensile strength (Rm) and fatigue limit strength after 109 cycles (σw9) and in the non-failure condition of the dual phase steel were 1603 MPa and 600 MPa, respectively. The position of inclusion in the steel had the greatest influence on the ultra-high cycle fatigue life, and the inclusion size had secondary influence on fatigue property. However, the curvature of inclusion had the least influence on the fatigue behavior. Among all the inclusion parameters, the size and position of inclusion was positively correlated with the fatigue life, but the curvature of inclusion was negatively correlated with fatigue life. Based on the study of inclusion factors, a prediction model of ultra-high cycle fatigue life using the above-mentioned inclusion parameters for the steel is proposed. The significance of the study is that the ultra-high cycle fatigue life can be easily predicted by analyzing inclusion factors.