What is residual stress?

Residual stress is a self-equilibrating internal stress that exists within a material without any external load applied to it. It can arise from various processes such as manufacturing techniques, heat treatment, plastic deformation, phase transformations, and mechanical damage. Residual stresses can be classified as either macroscopic or microscopic. Macroscopic residual stresses are those that vary significantly over distances that are large compared to the grain size of the material, while microscopic residual stresses are those that vary significantly over distances comparable to the grain size.

Residual stresses can have significant effects on the properties and performance of materials. They can affect the material's strength, ductility, fatigue life, corrosion resistance, and dimensional stability. In some cases, residual stresses can be beneficial, such as in the case of prestressed concrete, where the residual compressive stresses can improve the material's strength. However, in other cases, residual stresses can be detrimental, such as in the case of welded structures, where the residual tensile stresses can lead to cracking and failure.

There are various methods to measure residual stresses, such as X-ray diffraction, neutron diffraction, and hole-drilling techniques. These techniques provide valuable information about the magnitude, distribution, and depth of residual stresses within a material. Managing and controlling residual stresses is an important aspect in materials engineering and design, as it can help improve the performance and safety of materials and components.