Analytical model for predicting residual stresses in abrasive waterjet peening

Abstract

Abrasive waterjet peening (AWJP) is a new mechanical surface treatment where particles are delivered by a waterjet to induce plastic deformation and achieve surface strengthening effects on a workpiece. Although fatigue strength can be improved by inducing compressive residual stress, the prediction of residual stress distribution remains challenging because particle–workpiece interaction occurs with randomicity, superposition, and overlapping. In this paper, a theoretical model is proposed for predicting workpiece plastic deformation and compressive residual stress by analysing i) the non-uniform energy distribution of the AWJP beam caused by the non-uniformity of the abrasive size, spatial distribution, and impact velocity; ii) material hardening among multiple impacts by abrasive particles; and iii) overlapping traces induced by the changing position of the AWJP beam. The AWJP experiments were conducted in single-pass/multiple-pass/multiple-overlapping footprints with different pump pressures, traverse speeds, and jet centre distances of the adjacent traces to validate the model. The results showed good agreement with the predicted surface roughness and compressive residual stress. Compressive residual stress increased with the pump pressure, whereas the effect of pump pressure change rate decreased when the pump pressure was increased; further, residual stress is nearly constant with the variation in traverse speed and jet centre distance of the adjacent traces when it decreases to a certain value. These results can act as references for the control of residual stress and the prediction model can aid industrial manufacturing in AWJP parameter optimisation (e.g. pump pressure, traverse speed, surface roughness, compressive residual stress, and centre distance between two adjacent traces).

Keywords

• Abrasive waterjet peening
• Analysis model
• Compressive residual stress distribution
• Work hardening
• Overlapped footprints