Stress relaxation

Slow, time-dependent deformation of a material under sustained load. Polymers and adhesives creep far more readily than metals, particularly at elevated temperature or as the glass transition temperature is approached, so long-term loads must be assessed separately from short-term strength.

Material behaviour that combines viscous flow with elastic response, so that stiffness depends on time, loading rate and temperature. Polymers are viscoelastic, which gives rise to creep, stress relaxation and damping, and is characterised by dynamic mechanical analysis.