Initial interest in applying unified viscoplastic theories was in determining deformations and stresses in structural components at high temperatures subjected to steady and low frequency cyclic loadings. These problems originated in the operation of gas turbine engines and power generation plants. Strain rates were generally less that 1 sec−1 and could be as low as 10−7 sec−1. For these problems, the parameter D0 in the kinetic equation (8) of the B-P model was set to be 104 sec−1 and sets of material constants were generated on that basis. These applications usually involved high temperatures so thermal recovery of hardening was an important component of the evolution equations. A number of more recent applications of the B-P model were concerned with strain rates above 10 sec−1 and were therefore based on the higher value of D0=108 sec−1. These sets of material constants could also be used at lower strain rates making use of modern numerical techniques. Recovery of hardening is usually unimportant in applications at high strain rates so those parameters tend to be omitted in the determination of the high rate material constants.
KeywordsHigh Strain Rate Material Constant Directional Hardening Dynamic Strain Ageing Isotropic Hardening
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