Characterization of the Low Cycle Fatigue Properties of Hot Rolled Sheet Steels

With the increased emphasis on fuel economy coupled with more stringent safety and crash worthiness requirements, the automotive designer is faced with evaluating new designs and new sheet steels to achieve weight savings in applications which are potentially fatigue critical. Strain-based cumulative damage techniques are becoming available for handling these types of fatigue problems. An important input to the analysis is the low cycle fatigue (LCF) behavior of the material in the critical location of the component. The purpose of this paper is to summarize LCF properties of HRLC and HSLA automotive sheet steels over a range in strength of 30 to 90 ksi and a range in hot-rolled thickness of 0.070 to 0.180in in the as-received condition prior to fabrication. Trends in average LCF properties with increasing strength level are described along with an evaluation of material variability. Examples of how this information might be used are given.