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Abstract:The objective of this study is to investigate the effects of key factors on the powertrain loading dynamic characteristics and fatigue damage. First, the engine and the transmission output shaft torque of a multi-axle vehicle powertrain system were measured by proving grounds (PG) testing and analyzed with a conclusion that the powertrain loading changes were mainly related to three key factors: the mean engine torque, the harmonic engine torque, and the vibration properties of the system. Subsequently, a dynamic model considering the three factors was built and validated by the test data. Finally, fatigue damage of shaft parts and gear parts were calculated to investigate the influence degrees of the three factors. The results show that, the harmonic engine torque and the vibration properties of the powertrain system have a great influence on the fatigue damage of shaft parts, and the mean engine torque is the main factor causing the fatigue damage of gear parts.

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Struck axle is a critical component of truck that bears the auto-body weight and load weight. Fatigue life safety is the primary consideration in the design process of axle. With the development of environmental protection concept of energy saving and emission reduction, lightweight design of vehicles becomes more and more urgent. It has been becoming a mainstream trend for design to ensure both safety and significantly reduce the weight of axle. Based on the basic truck axle structure design, revised designs with thickness-reduced were proposed to reduce the weight of truck axle .Both basic and modified design were modeled using Abaqus 3D software to calculate the stress and strain contours in the case of vertical load and axial torque, then fatigue life contours of models for each load case were calculated with the help of Brown-Miner biaxial fatigue theory. It was shown by the research that topology-optimization of truck axle, under a premise of qualified fatigue life and stiffness required by customers, can reduce the weight of two kinds of truck axles by 15.3% and 18.1% respectively.

Fatigue failure easily occurs in the weld seam of bogie frame, fatigue life prediction is very important. Based on the UIC615-4 (Motive power units- Bogies and running gear-Bogie frame structure strength tests ) and IIW standard (Recommendations for fatigue design standard of welded joints and components-IIW document XIII-1965-03/ XV-1127-03), fatigue test process of bogie frame is simulated by means of finite element method. Using Miner cumulative damage theory, on the basis of IIW welded joints S-N data, fatigue life of the welded frame is predicted, and the virtual fatigue test of welded frame is completed. During the phase of product design, virtual fatigue test technology can be used to evaluate the fatigue strength, which can find the weak part and improve product design quality.