Visco-elastic Solid o Kelvin Material:
Creep Behaviour: The solution for a creep test to constant stress σ0 is:



The application of a stress step in this model produces a phenomenon of slowed down elasticity, in which initially all the load is supported by the piston, and then it is transferred little by little from the piston to the spring until this one supports all the load.

The yield curve drop corresponding to the elimination of the stress step at moment t1 is obtained by the superposition of the equation of yield that results from applying σ0 en t=0 y - σ0 en t=t1