ABSTRACT
In the application of forces or displacements to a body, the effects are observed by the measurement of displacements (or strains). To predict the behaviour, tests must be carried out on specimens of the material to determine not only the elastic constants of the material but also the laws for its behaviour in the inelastic range. When forces are applied to a body or there is a change in temperature, deformations occur. These deformations are not necessarily elastic in the Hookean sense. That is, the stress-strain curve may not be a straight line and the deformations not recoverable. In the theory developed on strain, it is found that certain non-linear quadratic terms occur which together form a quadratic strain tensor. In this discussion on constitutive relationships the effects of temperature on both the yield surface and the modulus of elasticity of the material are taken into consideration.
