Overview - Residual stress part 1 - Measurement techniques

Residual stress is that which remains in a body that is stationary and at e quilibrium with its surroundings. It can be very detrimental to the perform ance of a material or the life of a component. Alternatively, beneficial re sidual stresses can be introduced deliberately, Residual stresses are more difficult to predict than the in-service stresses on which they superimpose , For this reason, it is important to have reliable methods for the measure ment of these stresses and to understand the level of information they can provide. In this paper, which is the first part of a two part overview, the effect of residual stresses on fatigue lifetimes and structural integrity are first summarised, followed by the definition and measurement of residua l stresses. Different types of stress are characterised according to the ch aracteristic length scale over which they self-equilibrate. By comparing th is length to the gauge volume of each technique, the capability of a range of techniques is assessed. In the second part of the overview, the differen t nature and origins of residual stress for various classes of material are examined.