A predominant factor contributing to the structural failure of machine parts, pressure vessels, framed structures, etc., may be the Residual (locked-in) Stress that exists in the object prior to its being put into service.
Residual Stress is usually introduced during the manufacturing cycle, and are caused by processes such as casting, welding, machining, heat treating, molding, etc..
Residual Stress can neither be detected nor evaluated by
conventional surface measurement techniques, since the strain sensor (strain gauge, photoelastic coating, etc.) can only respond to strain changes that occur after the sensor is installed.
The most widely used practical technique for measuring residual stresses is the hole-drilling strain gauge method described in ASTM Standard E837. With this method, a specially configured electrical resistance strain gauge rosette is bonded to the surface of the test object and a small shallow hole is drilled through the center of the rosette.
Residual Stress Measurement Strain Gauges (Gages) and Instrumentation brochure provides more indepth information simply click on the .pdf file download below.
Residual Stress Measurement Strain Gauges (Gages) and Instrumentation