A novel method of determining residual stress distributions in plates using the incremental slitting technique

A method is described to determine residual stress distributions in homogeneous plates from strain measurements obtained using the incremental slitting method, which is modelled using a linear thermo-elastic analysis originally developed for anisotropic multiple-ply laminates having arrays of equally spaced ply cracks. A linear thermo-elastic analysis, for the special case where the plate is homogeneous and isotropic, is used within an inverse modelling problem to interpret measured strains, obtained by gradually slitting the plate and measuring strain changes on the external surface during bend deformation, in terms of distributions of residual stress. The model has been used to estimate the residual stress distributions within polypropylene-based samples, including samples with untreated and aminosilane-treated glass flakes. In the internal region of the plate, the residual stress distribution can be estimated reliably as results do not depend on the parameters used for the analysis. Results of predictions near the cut free surface show some variability, which is thought to be attributable to the insensitivity of strain measurements to the length of the slit. To overcome this problem it is recommended that a plate is slit from both free surfaces at different widely spaced locations. Comparisons of the calculated strains with the original smoothed experimental input data showed very close agreement, indicating that the linear thermo-elastic model is appropriate for these samples.