High accuracy and efficiency calculation model for predicting the reduction of residual stress on large pressure vessels by ultrasonic impact surface treatment

Abstract

Ultrasonic impact treatment (UIT) is a new surface strengthening method to reduce the residual stresses on large pressure vessels induced by surface and repair welding. An accurate and high efficiency calculation model is the key to accurately predicting the full‐field residual stresses on large pressure vessels under the UIT process. In this article, a full‐coverage impacting model is proposed to simulate the impacting process of the UIT pin. The effects of UIT on the residual stresses on repair and surface welded pressure vessels were investigated by explicit dynamic simulation. Experiments were also performed to verify the prediction results. Results show that the proposed full coverage impacting model can greatly improve the simulation precision and the calculation efficiency. The predicted residual stresses after the UIT process using the proposed model are consistent with the measured results. A remarkable reduction in residual stress was achieved in the zone subjected to UIT. The tensile residual stresses on the surface of the treated area were reduced to compressive stresses. With the increase of the impact velocity and the coverage rate, the residual stresses on the surface and transition layers decreased and then tended to stabilize. The impact coverage rate should not exceed 200% to avoid damage and save time.