A Nonlinear Uniaxial Integral Constitutive Equation Incorporating Rate Effects, Creep, and Relaxation,
Abstract
A previously proposed first order nonlinear differential equation for uniaxial viscoplasticity, which is nonlinear in stress and strain but linear in stress and strain rates, is transformed into an equivalent integral equation. The proposed equation employs total strain only and is symmetric with respect to the origin and applies for tension and compression. The limiting behavior for large strains and large times for monotonic, creep, and relaxation loading is investigated and appropriate limits are obtained. When the equation is specialized to an overstress model it is qualitatively shown to reproduce key features of viscoplastic behavior. These include: initial linear elastic or linear viscoelastic response; immediate elastic slope for an instantaneous change in strain rate; normal strain rate sensitivity and nonlinear spacing of the stress-strain curves obtained at various strain rates; primary and secondary creep and relaxation such that the creep (relaxation) curves do not cross. Isochronous creep curves are also considered. Other specializations yield wavy stress-strain curves and inverse strain rate sensitivity. For cyclic loading the model must be modified to account for history dependence in the sense of plasticity. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 1978
- Accession Number
- ADA054252
Entities
People
- E. Krempl
- E. P. Cernocky
Organizations
- Rensselaer Polytechnic Institute