Plastic Flow, Creep, and Stress Relaxation: Part II. Creep

Publisher Website
Google Scholar
Abstract
The general equation covering the deformation of plastic substances given in Part I is applied to creep. Creep is defined as a mechanism of deformation for systems which have a curvilinear relationship between stress and strain rate and a curvilinear relationship between strain and time at constant stress. Creep is connected with changes in the internal structure of a plastic substance and results in an increase in strength of such materials through work‐hardening. Equations are derived which give the stress as a function of strain rate and time (time‐hardening), as a function of strain rate and strain (strain‐hardening) and as a function of strain rate, strain, and time. The difference between time‐hardening and strain‐hardening is discussed. Expressions are given for the coefficients of viscosity of such systems which are independent of the stress applied. The relaxation of stress at constant strain is discussed, and it is shown that the stress relaxation depends upon the history of the substance under test. The concept of creep is also applied to thixotropic systems which are considered as cases of work‐softening.

This publication has 5 references indexed in Scilit: