关键词: 变速箱中间轴, 焊接结构, 多轴疲劳, 多轴结构应力法, 非比例载荷路径

Abstract: The transmission system of heavy-duty vehicles had the characteristics of large speed ratio and large torque. The welded structures of transmission intermediate shafts carried complex working loads， and multiaxial fatigue failure was easy to occur at the weld seams. In order to evaluate the fatigue life more accurately and effectively， a fatigue life analysis method for the welded structures of transmission intermediate shafts of heavy-duty vehicles was proposed based on the multi-axial structural stress method. First， the finite element model with weld details for the welded structures of transmission intermediate shafts was built. Then， the time history of the structural stress components at the fatigue hazard points of the welds was solved， the load path was synthesized on the structural stress planes to obtain the equivalent stress range of the non-proportional loading path. Finally， the fatigue life was determined by combining the main S-N curve. This method was used to evaluate the fatigue life of the weld roots and weld toes of the welded structures of transmission intermediate shafts， and the results were compared with those of the fatigue bench tests. Results show that the predicted damage location and fatigue life are both in good agreement with the experiments， and the differences between the fatigue life of the weld roots and toes are consistent with the multi-axial fatigue test results in the existing literature， which indicating that the proposed multi-axial structural stress method is reliable for the fatigue life assessment of the welded structures of transmission intermediate shafts. 

Key words:  , transmission intermediate shaft, welded structure, multi-axial fatigue, multi-axial structural stress method, non-proportional load path