Creep testing

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.

Testing in which a specimen or component is subjected to repeated cyclic loading to establish how many cycles it survives at given stress or strain levels, with results often presented as S-N curves. It underpins life prediction for structures exposed to vibration, wind, wave and traffic loading.

The temperature at which a standard plastic bar deflects by a specified amount under a defined bending load while being heated at a set rate, measured to ISO 75 or ASTM D648. It is used to compare the short-term temperature resistance of resins and compounds, but it is not a safe continuous service temperature.

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.