Mechanical Equation of State in Molybdenum

• Published in: Transactions of the Japan Institute of Metals 1982, Vol.23(5), pp.234-242
• Main Authors: Tanoue, Koji, Matsuda, Hidehiko
• Format: Article
• Language: English
• ISSN: 0021-4434; 2432-4701
• DOI: 10.2320/matertrans1960.23.234

Stress relaxation tests are made to study whether or not the mechanical equation of state σ=σ (y,\dotε) with “Hardness” (y) proposed by Hart holds in polycrystalline molybdenum with various deformation histories. Prior to stress relaxation tests, deformation history is given by any one of four loading modes of (A) monotonic loading, (B) cyclic loading, (C) strain rate cycling and (D) swaging, respectively, at 292 K. Consequently, any type of deformation history between (A), (B), (C) and (D) shows a good linear relationship with stress-strain rate scaling at the same temperature and forms one concave upward master hardness curve. The stress-strain rate scaling parameter m{=(δln\dotε⁄δlnσ)ν} changes depending on the deformation history. It is, therefore, concluded that the mechanical equation of state σ=σ (y,\dotε) does not hold in general because the form of the relationship changes when the deformation history changes, and that Hart’s hypothesis is valid experimentally only when the deformation history is given by a specific mode of loading.