Numerical and experimental analysis of residual stress induced by elastic-plastic bending, tension or torsion loading

In this work a complete analytical model of elastic-plastic bending, tension and/or torsion has been developed to simulate the manufacturing of leaf springs and coil suspensions. A special procedure was also implemented to simulate mechanical surface treatments such as shot peening. These models allow predicting the plastic strains and residual stresses induced by successive loadings of the part. Our approach required first defining the mechanical behaviour of the material. The constitutive laws of the employed steels were therefore identified starting from cyclic loops recorded for tests carried out at various imposed strains. These laws were introduced in the plasticity model to simulate the different steps of manufacturing: forming of the part, presetting operations, shot peening, elastic-plastic shake down produced by the first cycles of fatigue. In order to validate the model, residual stress maps were also characterized by X-Ray diffraction. However, to retrieve the maximum of information from this kind of measurement, the experimental data has been analysed through a global method which processes the whole acquired diffraction peaks at once.