Creep Testing

Creep is the slow, continuous, inelastic, permanent deformation of materials that increases with time under the action of constant stressStress. Generally occurs at high temperature, but can also happen at room or very low temperatures, albeit much slower. Creep results in large mechanical stressStress when loads are applied for long time. The rate of creep deformation is a function of the material’s properties, exposure time, temperature and applied load. In this chapter we first present rheological modelsRheological models for the understanding of the three major types of material deformation including elastic, plastic and creep deformation. Based on these models we give constitutive equations for steady-state and transient creepTransient creep. Also we study relaxationRelaxation behavior, which is the decrease of stressStress when a material is held at constant strainStrain. Linear and nonlinear creepNonlinear creep and relaxation are analyzed. Finally, we present mechanical tests for the creep, recovery and relaxation characterization of materials.