Research On The Performance Of Clinch-bonded Hybrid Joints Between Steel And Aluminum Alloy Sheets And Its Application On Auto Body

With the increasingly serious energy and environmental problems, energy conservation and emissions reduction of the car has become the important direction of the development of the automotive industry. As an important means of energy conservation and emissions reduction, automobile lightweight has been brought to the attention of the automotive industry. At present, many lightweight materials such as aluminum alloy, magnesium alloy and carbon fiber have been used in car body in different degrees, in which aluminum alloy is used the most widely. In addition, steel-aluminum hybrid structure car body has also been put into use. The use of these lightweight metal materials can not only meet the needs of the body performance, but also greatly reduce the weight of the car body and even the whole car.The density of aluminum alloy is only one-third of that of steel, and it has the high specific strength and specific stiffness as well as good energy absorption property. However, when aluminum alloy is used to weld in traditional steel car body, its connection performances cannot meet the requirements due to welding penetration and electrochemical corrosion such phenomena. New connection technology with pressure connection, cementing and clinch-bonded hybrid joint, etc., can realize the reliable connection of steel aluminum plate. Through a comparison of experiments, it is concluded that clinch-bonded hybrid joint has higher bonding strength than single pressure connection and cementing; at the same time its connection safety has improved.Clinch-bonded hybrid joint is not just the simple sum of pressure connection and cementing, its connection effect and destruction mechanism are more complicated. The finite element simulation model of clinch-bonded hybrid joint is built based on cohesive zone model, and its validity is obtained through a comparative analysis of experiments and simulations. After verifying the validity of the simulation model, with composite joint shear strength and peel strength, RSM model, RBF model and Kriging model are built by selecting the factors influencing joint strength and adopting the method designed based on experiments. Through this comparative analysis, it is concluded that RBF model has the best fitting effect, and based on this model the multi-objective optimization can be realized by genetic algorithm. By the comparison of optimization results and simulation analyses, the correctness of the optimization results is verified.In order to study the practical application of clinch-bonded hybrid joint to the car body, it’s necessary to build the simplified model of steel aluminum mixed front longeron and steel front longeron with the same specifications, and then analyze the situation of the peak load, the total energy absorption and the specific energy absorption under its quasi-static crush, which should be verified through the experiment. Based on experiments and simulations, it is concluded that the steel aluminum mixed front longeron of clinch-bonded hybrid joint has better energy absorption property, and its load is also more stable in the process of crushing, through which higher safety performance is obtained. By analyzing the application of the front longeron, it can reach a conclusion that clinch-bonded hybrid joint has a positive influence on further expansion of the application of aluminum alloy to car body.