Multiaxial Fatigue Life Prediction Of A Semi-trailer Frame

The frame is a critical part of a semi-trailer, which sports the good and all the accessories. The frame must have enough stiffness and strength to maintain functionality and have sufficient life. It is also needed to be as lighter as possible to meet the lightweight purpose. When the truck is driving on the road, the frame of semi-trailer is mainly subjected to repeated loading. Subjected to this kind of loading, the main failure of the frame is the fatigue crack. So the fatigue analysis is crucial for the semi-trailer frame design and analysis. The traditional methods are usually based on experience; it can’t quantify some important factors. Because of which some parts of the frame could generate fatigue crack and some parts could have redundancy of strength. The recent static analysis method is instructive when the load of structure is static. When fatigue crack happens, the local stress is always less than the UTS of the material. So it is very important to introduce the fatigue analysis method into the semi-trailer frame lightweight design process.The research project of this paper is a semi-trailer for ore transportation, mainly driving on the roads which have severe roughness. According to the accident survey about this trailer, fatigue crack always initiates at the joining part of the longitudinal beam. This paper has performed a fatigue life prediction of the semi-trailer frame. The main works of this paper are:1) Assembled the multi-body dynamic model of the truck-trailer vehicle. Then run the full vehicle analyses (straight-line events) on the national road level B, obtain the PSD of acceleration of the trailer body centroid and10load spectrum of the trailer frame.2) The FE model of the trailer frame is built in ANSYS/workbench. A static strength analyses and a model analyses are carried out. The static stress distribution and first ten vibration modes are obtained. Based on the inertia relief method, the static stress distributions of the ten loads are separately obtained.3) Based on the static and model analyses, the mean stress modified Wang-Brown criterion is chosen to calculate the fatigue life. Meanwhile the main factors which have great influence on the frame fatigue feature are summarized and parameterized. Through analyzing the fatigue life distribution of the frame, the weak parts are fund out, and the life of the frame is less than regulation.4) Based on the fatigue analyses result, an optimization is given about the frame in material, structure and manufacturing process three aspects. Then calculate the fatigue life of the optimized frame. The frame not only meet the life regulation, but also lighter than the original one.This paper uses the virtual prototyping technology, combined with muti-body dynamics, Finite element analysis and fatigue analysis, to predict the fatigue life of the semi-trailer frame. Compared with actual failures, the result proves the accuracy of the model. An optimization about the material, structure and manufacturing process of the frame is provided. This paper is instrumental for optimization and lightweight design of the semi-trailer frame.