Residual stress part 2 - nature and origins

Abstract

Residual stress is that which remains in a body which is stationary and at equilibrium with its surroundings. It can be detrimental when it reduces the tolerance of the material to an externally applied force, as is the case with welded joints. On the other hand, it can be exploited to design materials or components which are resistant to damage, toughened glass being a good example. This review, which accompanies one on measurement techniques, examines the nature and origins of residual stresses on a variety of scales. This ranges from the long--range residual stress fields in engineering components and welded structures, through the interphase stresses present in composites and coatings, to the microscale interactions of phase transformations with local stresses.

Residual stresses are those that remain in a material after its original cause of stress is removed. It is useful to distinguish between macrostresses (Type I) that span large distances and microstresses (Types II and III) that occur at the grain or atomic level. There exist many measurement techniques, including destructive mechanical methods like hole drilling and non-destructive diffraction methods using X-rays or neutrons. How these stresses influence structural integrity is explained, where tensile stresses may cause failure while compressive stresses can enhance fatigue resistance. It is important to use the techniques that best represents the length scale and engineering problem at hand.