document: Microhardness can be related to other macroscopic mechanical properties such as yield stress, σ, and elastic modulus, E, both derived from compression testing. For work-hardened metals, Tabor derived a direct proportionality between hardness and compressive yield stress: H≈3σ [20]. However, it was soon realized that Tabor's relationship only applies to materials that exhibit full plasticity [9,10]. Deviations from this relationship have been reported for a number of metals, glasses and polymers where the elastic strains are non-negligible [9]. Hence, the different expressions describing the correlation of hardness with conventional macroscopic mechanical properties rely on the validity of the above-mentioned elasto-plastic models. In this way, hardness and yield stress no longer hold direct proportionality but their relationship depends on the specific material properties, such as Poisson's ratio and elastic modulus [9,11–13]. It has been shown that these elasto-plastic models not only satisfactorily explain an H/σ ratio of ≈2 for a number of polyethylene materials of different nature, but also theoretically account for the range of H/E ratios experimentally determined [21].
extractive_keyphrases: compression testing derived a direct proportionality deviations from this relationship glasses hold direct proportionality but their relationship materials that exhibit full plasticity microhardness polyethylene materials polymers where the elastic strains the different expressions describing the correlation of hardness with conventional macroscopic mechanical properties
abstractive_keyphrases: specific material properties, work-hardened metals