Creep & Stress Rupture

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Unlike fatigue, creep is the deformation of materials under constant stress and/or temperature over time. Generally, the creep of materials is speeded up by increasing the level of stress and temperature. The elongation of the material during creep testing is quantified using highly calibrated extensometry.  In this case, the creep testing provides the history of elongation at the designated stress and/or temperature over time. If no extensometry is utilised during the test, the creep life at fracture can only be recorded and this is known as ‘stress rupture’ testing. The creep life of materials is important in particular in constant-speed components where the stress is constant over time under certain temperatures. If the stress or temperature fluctuates, then this is no longer creep, but rather fatigue. The determination of the creep life is important to ensure the safety of structures and components that work under certain conditions.