Designing a Digital Twin of Weld Fatigue Based on Grid Interpolation and Equivalent Structural Stress Methods

This paper presents a digital twin (DT) to realize the prediction of weld fatigue for large and complex engineering equipment. Digital twin in this context consists of an equivalent structural stress method based on grid interpolation, radial basis function (RBF), and fatigue damage estimation which is adopted to calculate the remaining useful life (RUL). At first, methods for structural stress of tetrahedral mesh calculation are presented. This method provides trained data for the RBF model to realize the online prediction of structural stress since the complexity of the engineering structure. The predicted real-time stress values feed the fatigue damage model of the weld joint. The model combines the main S-N curve of the weld structure, the rainflow counting method, and the linear damage accumulation method to online calculate the RUL of the weld joint. Moreover, the boom weld of telehandlers is an example to validate the proposed framework for structural stress prediction and RUL estimation of the engineering equipment. The results show that the equivalent structural stress method based on grid interpolation can implement the structural stress analysis of tetrahedral mesh. Most importantly, a compensated radial basis function (C-RBF) is developed to realize structural stress prediction in real-time and online RUL estimation. The C-RBF method can improve prediction accuracy compared with the RBF method. All in all, the proposed framework can leverage the advantages of DT for the fatigue online analysis of weld joints, and then promote the development of DT in engineering applications.