Abstract
A version of the metal plasticity relaxation model based on a plasticity integral criterion with the characteristic relaxation time parameter is suggested. The dislocation concepts of metal plasticity together with the Maxwell model for a strongly viscous fluid are used to show that this characteristic relaxation time parameter can be interpreted in terms of dissipation and energy accumulation in the case of mobile dislocations. The coincidence of the values of characteristic plastic relaxation time obtained for various descriptions of the whisker deformation allows one to conclude that the characteristic relaxation time is a basic characteristic of the material dynamic properties.
Highlights
Several cases of unexpected mechanical behavior of metals in deformation can readily be explained by taking their dynamic characteristics into account
For a material with such properties, these strain rates are already sufficient for exciting the dynamic deformation mode, which cannot be described on the basis of quasi-static concepts that there are critical flow stresses in the material
The maximum shear stresses (3) are proportional to the yield point of the material. It follows from (3) that, in the case of small characteristic times and strain rates, we have a constant value of the yield point, which can vary only due to the strain strengthening [19]
Summary
Several cases of unexpected mechanical behavior of metals in deformation can readily be explained by taking their dynamic characteristics into account One such wellknown paradox is the yield drop [1,2,3] and sharp yield point phenomenon in metal whiskers [4] when, in the case of quasi-static loading rates 10−5–10−2s−1, the stresses attained in the material are dozens times greater than the value of its quasi-static yield point [4]. This parameter should be independent of the deformation process characteristics but should express the mechanical properties of the material itself in a wide range of loading rates
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