Study On Mechanical Properties Of Rivet-bonded Joint Structure In Vehicle Body

With the development of the body lightweight,the common use of hybrid connections and hybrid materials is increasing.The thesis mainly studies the static mechanical properties of the B-pillar T-joint based on rivet-bonded hybrid connection.In this paper,the T-joint structure with rivet-bonded connection is taken as the research object,and the mechanical properties and failure forms of the joint structure are studied by combining with test and simulation.The main research contents of this paper are as follows:(1)Johnson-Cook constitutive model and failure criterion are used to simulate the failure of the metal part of the T-joint.This part focuses on the Johnson-Cook failure criteria.Firstly,tensile failure tests under different stress triaxiality were carried out on metal specimens of various specifications,and then the corresponding finite element simulation was carried out on these tensile tests respectively to obtain the relationship between stress triaxiality and fracture strain of metal.Finally,the parameters of Johnson-Cook failure criterion were calculated,and the validity of the parameters was verified by numerical simulation and experimental results;(2)The rivet-bonded Single Lap Joint(SLJ)was connected by different materials.The failure mechanism of single lap joints was studied by quasi-static tensile test.Single lap joints were modeled in ABAQUS software where Johnson-Cook constitutive model and failure criterion were adopted for the metal part,the Hashin failure criterion was used for the thermoplastic carbon fiber reinforced composites and Cohesive Zone Model(CZM)was used for the adhesive layer.The Finite Element Analysis(FEA)of quasi-static tensile failure was carried out in ABAQUS,and the numerical simulation results were compared with the experimental results to obtain a reliable strength evaluation of the single lap bond riveting hybrid joint.Finally,these studies could build up an accurate and effective simulation model about forming,fracture and failure of SLJ.(3)The hybrid connection of multi-rivet riveting and adhesive bonding was adopted by connecting the cap plate made of thermoplastic carbon fiber reinforced composite material and the bottom plate made of 6061-T6 aluminum alloy to make a T-joint sample which is designed by our research team to conduct static mechanical properties studies.Then,the bending failure experiment of T-joint under quasi-static condition was designed and the displacement-load curve was obtained to evaluate the bearing capacity and bending resistance of the joint.In the FEA part,the bending pressure numerical simulation of the T-joint was carried out in ABAQUS using the parameters which obtained from the above part,and the corresponding displacementload curve was obtained.The numerical simulation results were compared with experimental results to verify that it was valid,and the bearing capacity and bending resistance of the T-joint were reliable.This paper explores the mechanical properties of the T-joint with rivet-bonded connection,and finds that the joint structure under the dissimilar material connection has a strong bending pressure resistance,which is a huge improvement to the bearing capacity of the T-joint structure.In this thesis,the research of joint structure connection belongs to the engineering application of the lightweight technology of multi-material body,which provides a certain reference value for the research of the joint structure with rivet-bonded connection and dissimilar material.