THE marked dependence of the strength of metals on temperature, and on rate of loading at high temperatures, can be explained by assuming that above the equi‐cohesive temperature rupture takes place by plastic flow in a non‐homogeneous medium, consisting of rigid crystallites weakly cemented together. Although the stress concentrations required by the Griffith theory must still be operative above the equi‐cohesive temperature, it is suggested that they produce intergranular flow, rather than the elastic separation that occurs at temperatures below the equi‐cohesive temperature. A theory is developed based on the assumption that the strain energy at rupture reduces the energy of activation of the flow process, and the theory is shown to be in numerical agreement with the experimental results, if the energy of activation of the flow process is about one seventh of the latent heat of evaporation per gram atom. Values of the cohesive strengths and of the stress concentration factors are also derived.
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