Measurement of residual stresses in beams and plates using the crack compliance technique

The crack compliance method provides a useful extension to the range of techniques available for the measurement of residual stress fields. The method is most suitable for simple geometries where the stresses vary in one direction only (e.g, usually depth). This paper describes the application of the dislocation density method to the calculation of the compliance functions required for the analysis of experimental data (the surface strain changes as a slot is cut). In particular, the kernel functions appropriate to a specimen of finite thickness (i.e. a beam or a plate) are given. The use of the technique for this geometry, including the use of multiple strain gauges, is discussed. Some sample results are given for the case of a plastically bent beam and these are compared with predictions from beam theory and with neutron diffraction measurements.