Fatigue Growth and Small Testing of Welded Connection in a Residual Life Assessment (RLA) Strategy

This paper presents a computational fracture mechanics approach for Residual Life Assessment (RLA) of a welded connections in a typical crane and lifting equipment. These structural details are submitted to cyclic loadings, resulting in fatigue damage around microcracks in the heat-affected zones (HAZ), and consequently to safety and reliability issues. The complexity of crack propagation in welded structures requires experimental validation tools, determination of microstructural and physical properties in the HAZ, and fracture mechanics using efficient simulation tools for. A 3D finite element post processing analysis software – Z cracks – has been used to simulate the rate and direction of crack growth along the heat-affected zones (HAZ) of the welded connection using linear elastic fracture mechanics (LEFM) principles. The numerical results were then compared with fatigue crack growth tests results on a crane subsystem containing the welded connections. The numerical tool implementation procedure has resulted in identification of the strong and weak points of the LEFM-based crack growth simulation used. Based in a better understanding of the crack propagation, the results obtained should contribute to the improvement of engineering practices for the prediction of the Residual Life Assessment (RLA) of welded structures and to the definition of improved procedures maintenance procedures. This study could also use of small punch testing and statistical fractography to obtain material parameters in a quasi-non-destructive characterization method.