Finite element simulation prediction of repeated bending failure zone of roll-welded bellows based on an equivalent welding model

Abstract

In this paper, an equivalent welding model is proposed that takes the tensile stress and strain parameters of the axial weld area of the roll-welded bellows as the material properties to replace welding simulation. The integrated finite element method is used to simulate the following two model forming processes for the roll-welded bellows: (i) welding-bulging-repeated bending model, and (ii) equivalent welding-bulging-repeated bending model. The stress and strain distributions of the two models are compared and analyzed, and the main failure areas of the roll-welded bellows in the repeated bending process are predicted. At the same time, the accuracy of the model prediction is verified by the limited repeated bending test of the roll-welded bellows, and the failure mechanism of the roll-welded bellows is revealed. The results indicate that the stress and strain distributions of the two models are essentially the same, thus verifying the feasibility of the equivalent welding model. When the cyclic deformation reaches the limit, the predicted stress failure risk zone is located at the base metal position of the first wave-like trough of the bellows near the heat affected zone at the fixed end, which is consistent with the experimental results. This indicates that the equivalent welding-bulging-repeated bending model can accurately predict the position of the repeated bending fatigue failure of the bellows, thus laying a foundation for the optimization of the roll-welded bellows.