DETERMINATION OF RESIDUAL-STRESSES IN BIMATERIALS

Residual stresses play a prominent role in the fracture process of bim aterials and therefore knowing these stresses prior to failure is impo rtant for understanding the mechanical behaviour of bimaterials. A cri tical assessment has been made of three methods for determining the re sidual stresses. These methods are: stress optical measurement, indent ation method, and finite element method. With stress optical measureme nts the difference in the principal normal stresses, delta sigma, can be determined. In the centre region adjacent to the interface, the mea sured stress values are in agreement with results from a simple analyt ical formula for the normal residual stresses parallel to the interfac e. Surface stresses at arbitrary locations can be obtained by the usua l indentation technique. At the surface, stresses perpendicular to the interface are dominant and have the opposite sign to the stresses par allel to the interface. When there is no mechanical mismatch between t he components the magnitude of the residual stresses can be estimated with the above-mentioned formula. Two-dimensional plane strain finite element calculations are in good agreement with the stress optical mea surements.