Research On Connection Behavior Of High-Strength Steel-Aluminum Alloy Of Bus Frame Based On Friction Stirring Blind Riveting

As a new energy public transportation vehicle,pure electric buses have the advantages of zero emissions,flexible travel,and low maintenance costs,which can effectively alleviate the problems of traditional energy depletion,environmental pollution,and traffic jams.In order to further reduce the quality of the entire vehicle and improve the cruising range,it is necessary to design a lightweight body frame.Method for multi-material combination in frame is a common idea for vehicles to achieve light weight.A key problem faced by this program is joining technology in different materials.In order to provide a theoretical basis for the design of the joint of a high-strength steel-aluminum hybrid body of a pure electric bus,this paper is based on the friction stir blind riveting joining technology.The main contents of the research can be summarized as follows:(1)Taking friction stir blind riveting as the research object,on the basis of rationally simplifying the geometric model of the joint,the compressive stress distribution results of the members are obtained through finite element analysis of the joint,assuming that the compressive stress distribution is non-uniform distribution within the scope of the truncated cone,based on the theory of solid mechanics,the theoretical model of the stiffness calculation of the joint is proposed.The accuracy of the theoretical model is verified based on the results of the finite element analysis.The calculation accuracy based on the finite element analysis can be controlled within 7%.(2)Considering the influence of the structural configuration of the members,the joint thickness,plate thickness ratio,rivet diameter,contact coefficient,and aperture factor on the joint stiffness,the nonlinear quasi-static analysis of a total of 55 experimental groups were completed through 4 control groups,joining with the calculation results of the theoretical model derived in this paper,the stiffness feature of the members of friction stir blind riveted joints is studied.The joint stiffness check should focus on the rivet diameter and the structural configuration of the members.(3)Taking the typical beam-column friction stir blind riveting corner fittings joint of a pure electric bus body as the research object,the finite element analysis of 8 experimental samples was used to study the load bearing capacity,the failure mode under the limit state,the change of contact state and contact force and other characteristics of the different construction type of beam-column corner fittings connection.The recommended connection geometry configuration form is given based on the Moment-Rotation characteristic of the connection.(4)In order to study the initial rotational stiffness characteristics of the beam-column friction stir blind riveted corner fittings connection,an orthogonal test with mixed 4 factors and 5 levels was designed,where the factors are only for the geometry of the rivets and corner fittings in the connections.After completing the finite element analysis of 25 experimental samples,five typical failure modes of joints are discussed.Through multiple linear regression analysis,the initial stiffness calculation model of the beam-column friction stir blind riveted corner fitting joints is given,and the goodness of fit reached 0.719.