Self‐heating measurements under cyclic loading to identify history effects on HCF properties of high‐strength low‐alloy steel: Part I—Experimental investigations

Abstract

High cycle fatigue properties of steels are usually characterized in the as‐delivered state of the material. However, forming process, variable amplitude and accidental loading, called load history, could affect HCF properties. Given that investigating those history effect of fatigue properties by means of regular fatigue test would be very time consuming, self‐heating measurements under cyclic loading were considered. Two load history effects were studied, a macroscopic plastic pre‐strain and a cyclic pre‐loading, by means of self‐heating measurements under cyclic loading. All of the findings were used to propose a modification of a probabilistic two‐scale model, which links self‐heating measurements to HCF properties, given in the accompanying paper.

Self‐heating measurements under cyclic loading to identify history effects on HCF properties of high‐strength low‐alloy steel: Part II—Modeling

“…Therefore, throughout the rest of the study, the experimental and numerical results will only be related to the secondary self-heating regime. To analyze the experimental evolution of this secondary regime, an indicator has been introduced in the accompanying paper, 7 such as…”

“…[1][2][3][4][5][6] Studying these load history effects on HCF properties considering regular fatigue tests would be very time consuming; therefore, it was proposed to investigate those effects by means of self-heating measurements under cyclic loading, given in the accompanying paper. 7 In order to predict S-N-P curves (i.e., amplitude stress, number of cycles to failure, and probability of failure) from self-heating measurements, a probabilistic two-scale model was developed, 8,9 assuming that fatigue initiation is caused by localized microplasticity that induces dissipated energy. The Representative Elementary Volume (REV) of this model is composed of a population of elastoplastic sites randomly distributed within an elastic matrix.…”

“…The description of the studied material and the experimental results used to propose the extended approach of the model are given in the accompanying paper. 7…”

“…However, load history, such as forming process or accidental loading, for example, can have an effect on the HCF properties 1–6 . Studying these load history effects on HCF properties considering regular fatigue tests would be very time consuming; therefore, it was proposed to investigate those effects by means of self‐heating measurements under cyclic loading, given in the accompanying paper 7 …”

“…Finally, the validation of this extended approach is performed by comparing the predicted S‐N curves from the model and the experimental fatigue results considering a cyclic pre‐loading as load history. The description of the studied material and the experimental results used to propose the extended approach of the model are given in the accompanying paper 7 …”