Plasticity effects in incremental slitting measurement of residual stresses

The effect of plasticity is investigated for the incremental slitting, or crack-compliance, method for measuring through-thickness profiles of residual stress. Based on finite element simulations, the errors can be strongly correlated with KIrs, the stress-intensity factor caused by the cut extending into a residual stress field. 3-D simulations also show that the errors are strongly dependent on the amount of constraint provided by the part width. The simulations are used to develop a procedure for estimating errors from experimental data. Even with the possibility of plasticity errors in the measured residual stresses, the KIrs can be simply calculated using only the experimentally measured strains. This KIrs is called “apparent” because the calculation assumes elasticity. The apparent KIrs can then be used to bound the errors in the measured residual stresses. The error bound is given as a function of non-dimensionalized apparent KIrs and part width.