Research Of Structural Adhesive's Application In Vehicle Body Safety And Lightweight Design

The use of the materials in body showing a trend of diversification, but there is a big difference in the physical, chemical and mechanical properties between dissimilar materials, and its presents new challenges to the connection technology. Now therefore, research focuses on connection technology between dissimilar materials. Due to the traditional connection technology has obviously phenomenon of stress concentration when making a connection to the dissimilar materials, such as spot welding, riveting and bolt connection. As a new connection technology, structural adhesive connection has a good connection performance between dissimilar materials. And its conducive to body lightweight, improving crash performance of the vehicle, increasing the body structure stiffness, strength and durability. And also solve the problem of the phenomenon of stress concentration and the poor fatigue performance in the traditional connection technology.Firstly, the mechanism of structural adhesive connection, the basic technological process and the main factors influencing the structural adhesive connection are analyzed in this study, and has also carried on the simple introduction for the basic types, stress analysis and failure mode of structural adhesive joints. And it's ensure the correct use of structural adhesives and the best technological process to develop, and it's also providing reliable scientific basis for the optimization design of structural adhesive joints and the prediction of connection strength, and also providing a basis theoretical for the production of single lap structural adhesive joint.Then, based on the tensile test of single lap structural adhesive joint and the theory of cohesive zone model, and use the finite element software LS-DYNA to establish a finite element model for single lap structural adhesive joint in this study. In order to verify the accuracy of the model, in this study, the dynamic axial drop test was made and test verification is conducted, the results show that the cohesive zone model can be used to simulate structural adhesive's deformation and failure in dynamic conditions. Meanwhile, different simulation methods for structural adhesive were compared in this study,and the accuracy of the model is further confirmation.Secondly, based on the concept of joint efficiency and Optimal Latin Hypercube Sample(OLHS) in this study, the impact factors of its joint efficiency was firstly studied, and the influence of the asymmetry stiffness at the ends of the structural adhesive joint was also studied. For structural adhesive connection between steel and aluminum, study have shown that with the increase of parent metal material property(material yield strength), joint efficiency is increasing, but when the material yield strength increases to a certain value, the joint efficiency showed a trend of decline. Study also showed that the material yield strength of aluminum is more sensitive to impact on the joint efficiency than the material yield strength of steel. Joint efficiency has a similar trend along with the change of the geometry of joint(thickness of parent metal?lap length and lap width of joint). For the structural adhesive joints with stiffness asymmetry, joint efficiency increases with the stiffness asymmetry to reduce, so in order to improve the joint efficiency, should reduce as far as possible at the ends of the joint stiffness asymmetry.Finally, analyzed structural adhesive connection technology influences on lightweight design for body. At the same time, based on the subsystem model method, with the structural crashworthiness as constraint conditions, lightweight design is carried on front longitudinal and B pillar, the results showed that application of structural adhesive connection technology is good for the lightweight design of body and improves the structural crashworthiness.