Interferometric strain rosette and incremental ring-core cutting applied to residual stress measurement on a spot weld

Residual stresses varying with depth can be measured by using the interferometric strain rosette and incremental ring-core cutting. During the ring-core cutting, the residual stresses are released which cause strains relieved at the central ring core where an interferometric strain rosette is applied to it surface to measure the relieved strains. The relieved strain data can be used to calculate residual stresses. The stress-strain coefficients were calculated from Finite Element Analysis of the ring-core cutting process in previously published papers. A MATLAb software is developed to input the strains from an input data file, load the stress-strain coefficients, and calculate residual stresses. An example of residual stress measurement on an ultrasonic welding is shown to demonstrate the procedure of the measurement on small area of the spot weld through its thickness.