Discussion of “Contact Unloading Behaviors of Elastic-Power-Law Strain Hardening Material Considering Indenter Elasticity Effect” (Chen, C., Wang, Q., Wang, H., Ding, H., Hu, W., Xie, W., Weng, P., Jiang, L., and Yin, X., 2022, ASME J. Tribol., 144(12), p

Abstract

The readers ought to be aware of some claims based on unfounded theories in the subject paper [1], which could possibly distort results and hinder future research and development. To start, Eq. (3) in the subject paper is stated to be taken from Ref. [70] (Johnson’s classical textbook). However, said Eq. (3) is imprecise because it uses a constant coefficient θy = 1.1, as claimed. That coefficient does not account for the variability in compressibility of the materials in contact, i.e., the Poisson’s ratios of the materials. The general range of Poisson’s ratios, ν, for crystalline and engineering materials is between -1 and 0.5. For example, ν = 0.2 for cast iron, ν = 0.18 for glass, or ν = 0.44 for gold. There are many materials and crystallines that have negative Poisson ratios (some are even time-dependent). Thus, limiting analyses and discussions to narrow subsets of Poisson ratios, say around 0.3, would likewise be narrow. That dependence upon Poisson’s ratio is addressed not only in Ref. [70], but also in other dated work, such as by the Chang et al. (CEB) model [2]. The CEB derivation, however, has other flaws—see discussions in Refs. [3] and [4].