Determining the fatigue strength of a material requires a high experimental effort, which results in high costs for material development. Thus, efficient methods for estimating the materials fatigue strength are of great industrial and scientific interest. For steels, the Vickers hardness HV can be used to roughly approximate the fatigue strength (1.6*HV) [Mura02]. Although this method can be applied easily, it often leads to relatively high deviations, as it does not consider the cyclic the deformation behavior, which significantly influences the fatigue strength of a material. In this context, instrumented cyclic indentation tests enable a fast and reliable evaluation of the cyclic hardening potential, represented by the cyclic hardening exponent_CHT e_II [Görz22], which only requires a small material volume and short test durations.

Consequently, in the presented work an estimation model based on the relation between HV and the fatigue strength, complemented by e_II was developed. Therefore, the fatigue strength, HV and e_II were determined for different conditions of various low alloyed steels and their correlations were analyzed. This revealed a strong correlation between the fatigue strength and the product of HV and |e_II|. Based on this relation, an equation to approximate the fatigue strength was determined, which results in substantially smaller deviations of the estimation than achieved by the relation 1.6*HV proposed in literature [Mura02] (compare [Görz22]). Thus, considering the cyclic hardening potential leads to a more precise estimation of the fatigue strength.

Note that HV and |e_II| can be determined with relatively low experimental effort and hence, this model enable an efficient estimation of the fatigue strength. Additionally, a reduction of the indentation force in the CIT enables a high spatial resolution and thus, the proposed estimation model might be useful to determine the local fatigue strength in graded structures, which will be analyzed in future work.

[Görz22] Görzen et al. (2022): doi.org/10.3390/met12071066

[Mura02] Murakami (2002): ISBN 0080440649