Sources and scope for this page: Industry convention — no single governing standard (conventional usage, definitions vary between sources), covering the definition of creep. No independent source check is recorded for this page: the content rests on the sources listed and on the working shown on the page. How sources, methods and updates are recorded.
Definition
Creep happens because materials flow over time under stress, even below yield. It becomes significant at temperatures above roughly 30% of the melting point in kelvin for metals — around 300 °C for steel, 150 °C for aluminium, and room temperature for many plastics.
It is why a plastic part under sustained load deforms without ever being overloaded, and why PTFE gaskets take a set. Design for it by keeping sustained stress low, or by choosing a material with a higher temperature capability.
Common misuse
Designing a plastic part for a sustained load from short-term tensile data. Creep can double or triple the deformation over weeks.