Determination of residual stresses in bimaterials

Residual stresses play a prominent role in the fracture process of bimaterials and therefore knowing these stresses prior to failure is important for understanding the mechanical behaviour of bimaterials. A critical assessment has been made of three methods for determining the residual stresses. These methods are: stress optical measurement, indentation method and finite element method. With stress optical measurements the difference in the principal normal stresses, Delta sigma , can be determined. In the centre region adjacent to the interface, the measured stress values are in agreement with results from a simple analytical formula for the normal residual stresses parallel to the interface. Surface stresses perpendicular to the interface are dominant and have the opposite sign to the stresses parallel to the interface. When there is no mechanical mismatch between the components the magnitude of the residual stresses can be estimated with the aforementioned formula. Two-dimensional plane strain finite element calculations are in good agreement with the stress optical measurements.