Residualspænding

Residualspænding refers to the internal stresses that remain within a material or component after all external loads have been removed. These stresses are not caused by applied forces but arise from processes like manufacturing, welding, machining, heat treatment, or plastic deformation. Residual stresses can be tensile, meaning they tend to pull the material apart, or compressive, meaning they tend to push it together. They are always in equilibrium within the body, meaning the sum of all tensile residual stresses must be balanced by an equal amount of compressive residual stresses.

The presence and distribution of residual stresses can significantly influence a material's mechanical behavior. Tensile residual stresses generally decrease fatigue life and increase the susceptibility to stress corrosion cracking. Conversely, compressive residual stresses can enhance fatigue resistance and protect against crack initiation and propagation. Understanding and controlling residual stresses is crucial in many engineering applications, particularly in areas where structural integrity and long-term durability are paramount, such as in aerospace, automotive, and pressure vessel design. Techniques like shot peening, laser peening, and case hardening are often employed to intentionally introduce beneficial compressive residual stresses. Measurement of residual stresses can be performed using non-destructive methods like X-ray diffraction or ultrasonic testing, or destructive methods such as hole drilling.