| Popis: |
The Bodner-Partom (B-P) model of isotropic elastic-viscoplastic behavior is intended to be representative of the macroscopic response of metals and metallic alloys to loading over a very wide range of strain rates, temperatures, and loading circumstances. It is an incremental theory consistent with the requirements and constraints of continuum mechanics and thermodynamics and is considered “unified” in that plasticity and creep are particular response characteristics based on a single inelastic strain rate variable. The model is also “unified” in a more general sense by not separating a fully elastic region from the overall response. A small strain formulation is presented in the chapter; extensions to large strains are developed. Procedures are developed by various investigators to obtain the material constants for the B-P equations from test data. First, most of the parameters at a given temperature can be obtained from monotonic uniaxial stress-strain curves over a range of strain rates for which thermal recovery of hardening is not effective. The parameters include those associated with directional hardening based on the observation that the rate of directional hardening is usually significantly larger than that for isotropic hardening ml. The method involves determining the stress-plastic strain relation from a uniaxial stress-strain curve at a constant applied strain rate and determining the quantity as a function of stress. |
