Five-bar and one-bar models for thermal stress generation in the FZ, HAZ, and BM during arc welding

Abstract

A descriptive mode, named the five-bar model, is presented in this work to explicate thermal stress generation in welding. Taking as the base the widely known three-bar model, it is claimed that the proposed model is also capable of explaining stress generation at the HAZ. This stress would be progressively smaller than in the FZ, turning null at the material point in which the thermal stress does not reach the material yielding stress. In addition, the model also showed itself to be able to explain that the highest stress will be generated in the FZ and that the resultant stress will be defined by the yielding stress of the bead material and by the capability of the material in consuming these stresses through plastic deformation. However, the stresses in the HAZ might be as high as in the BM, once the coarse grain region of the HAZ sustains a higher yielding stress than in the FZ, defining the final intensity of the generated stress. The one-bar model, in turn, based on the same approach, allows us to demonstrate that the generated thermal stresses happen when the piece is free of angular bending or at limited plastic deformation and they are always tensile stresses. By analogy, the resultant stresses on the component are defined by the yielding stress of the weld bead material and by the capacity of the whole material to accommodate the stress through plastic deformation.

Keywords:

• Stress and deformation
• thermal stress
• modelling