Study On Assembly Process And Influencing Factors Of Screw Connection System For Automobile Key Components

With the development of science and technology and the promotion of manufacturing technology,people's production and living standards have been further improved.The automobile manufacturing industry has become a pillar industry of the national economy.And the thread connection is widely used and played an important role in the mechanical industry,such as automobile and internal combustion engine.Compared with other connecting techniques,the thread connection can generate great pretightening force,which is convenient for disassembly and assembly,and can realize batch production.But in order to guarantee the assembly quality of the screw thread connection system,the tightening state of the bolt joint system must be controlled.The main contents of this paper are as follows:Firstly,the theory of bolt tightening was introduced in this paper,including axial clamping force,and friction coefficient,torque coefficient,torque/angle included,then and it is discussed the relationship between torque and axial clamping force during bolt tightening,axial clamping force and angle,bolt working load etc.Secondly,the common method of bolt assembly was analyzed and the merits and demerits of these methods were compared.This paper focused on the torque assembly method as well as the influence factors of this method,which was widely used at home and abroad.The torque assembly method will cause the error range of the axial clamping force to be ± 35%,because the end faces friction,the friction of the thread,the tightening speed,the parameters of the thread and the assembly tool.Too much deviation will cause excessive torque.The preload will exceed the bolt strength limit and cause fracture failure,or to reach the limit torque,but the preload smaller.Torque method assembly is affected by many factors,even if the same process may lead to greater preload deviation,which can not meet the assembly requirements.Thirdly,this paper focuses on torque / corner assembly process and its influencing factors.The torque/angel method can be pre tightened by the first set of torque thresholds and then rotated at an angle to allow the bolt to exceed its elastic limit and achieve optimum preload.This can obviously reduce the influence of the friction coefficient,torque coefficient and other factors on the assembly results,so that the preload deviation is stable within ± 15%,and concentrated in the bolt near the yield strength.On the basis of theoretical analysis,the experimental research was carried out.The reasonable torque threshold and rotation angle were determined by analyzing and discussing the test results.Finally,the application prospects of assembly method and elongation method assembly were predicted and analyzed.