Study on fatigue performance and topology optimization of cast steel bifurcation joint under alternating load

The optimal shape under alternating load was studied using the topology optimization method to address the issues of heavy self-weight, insufficient optimization, and inadequate assessment of fatigue life on cast steel bifurcation joints. The numerical simulation analysis of a typical cast steel bifurcation joint under the alternating load was performed to comprehend its mechanical properties. The MSC Fatigue is used to explore and analyze the fatigue behavior of joints, and the control variable approach is used to examine the impact of various geometric parameters on fatigue life. Then, the load spectrum and fatigue life were invertedly calculated and transformed into maximum stress constraints by converting fatigue limitations into stress constraints. Finally, the optimal shape of cast steel bifurcation joint under fatigue limitations was studied using topology optimization methods. The research results show that the intersection of the main and branch pipes is the fatigue performance weakest part of the whole joint, which is different from the static analysis results. The geometric parameters affect the joint's fatigue performance, and the fatigue hazard zone disperses. The topology optimization shapes of cast steel bifurcated joints are different under vertical and horizontal stress constraints, indicating that different load conditions significantly impact topology optimization shapes. When optimizing cast steel bifurcation joints subjected to alternating loads, optimization can be done on the main pipe and branch pipes rather than in the intersection of the main pipe and branch pipes.