Research On The Key Parameters Of Bolted Joints With One Cylindrical Bolt

Bolted joints are widely used in mechanical connection structures.They not only have the advantages of simple structure,convenient disassembly and good versatility,but also have good mechanical performance,vibration resistance and transmission performance.Preloading bolted joints structures during service may be subjected to combined loads such as vibration,impact,alternation and temperature.Compared with assembly preloading process,the stress of bolted joints structures in service is more complex.Therefore,when designing and checking the bolted joints,the required calculation parameters should be determined reasonably.The axial relative stiffness of bolts and the number of interfaces for transferring transverse loads are two key parameters.Accurate determination of their values are an important step in the design and verification of bolted joints.In this paper,a large number of finite element models of bolted joints structures were established,and the research was carried out by combining theoretical analysis with finite element simulation.Based on the actual loading situation of bolt preloading process,a simulation method of bolt preloading with threaded structure,the rotation angle method of bolt head,was proposed in this paper.At the same time,three-dimensional small stiffness spring elements were introduced into the contact interface of the bolt connection finite element model,and a boundary constraint method of the finite element model was proposed to study the axial relative stiffness of bolts.According to the axial stress nephograms of the finite element model of bolted joints structures after preloading simulation,the modified initial diameter of the compression deformation body in the compression area were proposed.And the quartic theoretical modified analytical formulas of compression stress for the axial stiffness of the compression deformation body were also proposed.Then,by comparing the transverse load transfer of each contact interface of the finite element model of bolted joints structures of different groups,the effects of different variables on transverse load transfer were explored.Variables included the thickness of the jointed parts,the outer diameter of the jointed parts,the outer diameter of the washer,the thickness of the washer and the long axle sleeve,the number of the jointed parts,the position of the transverse load and the proportion of the transverse load at different action positions.The results showed that the number of interfaces for transferring transverse loads was not related to the bolt head,nut support surface,and the contact interface between washer,long axle sleeve and jointed parts,only related to the number of contact interfaces between the jointed parts under transverse load.Finally,combining the theory of design and verification of the bolted joints and the research results of this paper,the software of design and verification of the bolted joints was compiled.The results show that the relative error between the simulated stress and the theoretical stress is less than 3.00%,which indicates that the rotation angle method of bolt head can realize the preloading simulation of bolts with threaded structure accurately.The boundary constraint method of constraining the free end of spring elements can be used to study the axial relative stiffness of bolts.When calculating the axial relative stiffness of bolts,the relative error between the quartic theoretical modified analytical formulas of compressive stress and the simulation calculation is less than 1.5%,which shows that the calculated results of the quartic theoretical modified analytical formulas of compressive stress have high accuracy.The number of interfaces for transferring transverse loads is not always equal to the number of interfaces between connectors under transverse loads,but should be taken in 1 or 2 according to the actual situation of bolted joints structures.As for the software of the design and verification of bolted joints,users can realize the verification of bolted joints automatically by inputting basic parameters,and also output the corresponding verification report automatically.