Relaxation and Creep
In approximate models, time does not influence the results.
The suitable representation of the laws of behaviour for time dependent materials has to be three-dimensional, with the variable time added to the stress and the strain. In order to simplify this, the following projections corresponding to tests are used:
(ε,t) Creep Test (σ=cte)
(σ,t) Relaxation Test (ε=cte)
(σ, ε) Tensile Test ( t=cte)
Stress Relaxation Test: This means the application of a constant strain to a specimen of material.
Creep Test: The material is subjected to constant stress measuring the strains over the course of time. The cross-sectional area of the specimen varies and tensions must be real and non engineered.
The types of solids are: elastics, elasto-plastics, visco-elastics and visco-plastics