Residual Stresses are stresses developed in the work piece because of welding, casting, forging
or any other processing. The presence of residual stress in component can cause distortion.
This distortion is the cause of dimensional instability. Sometimes this distortion is so severe that it may lead to total destruction of the component.
There are various methods of relieving residual stresses. The earlier techniques include hammering the work piece with a wooden mallet and dropping a casting or weldment from a height to pile of sand. This probably set up vibrations which eliminated some of the residual stresses caused during casting or fabrication process. The more recent methods are ageing and annealing. These earlier methods of relieving stresses formed the first step towards what is known as vibratory stress relief
The vibratory stress relief process can be described as a ‘method of applying Controlled low amplitude, low frequency vibrations in metal components to Obtain dimensional stability and control for machining tolerances’. It is an Economical, fast and convenient method of reducing stresses and is used during process to achieve the dimensional stability