Refinement Analysis Of Bolt Structure And Its Application In Nuclear Power Equipment

In nuclear power equipment,bolts are ubiquitous.No matter whether it is the transmission force or the sealing performance of the gasket,its role can not be ignored.This article takes the nuclear power equipment as the research background,takes the bolt structure as the research object,carries on the following analysis.(1)In order to study the load distribution of M thread and MJ thread,ABAQUS software was used to establish a two-dimensional thread model for mechanical analysis.Firstly,the effects of radial dimension,friction coefficient,elastic modulus,engagement count and pitch on the bearing distribution of M threads were analyzed.The calculation results were verified by empirical formulas;then the bearing rules of MJ threads under different materials were analyzed and compared.The load distribution law of MJ thread entering into plasticity was studied.Finally,the stress,displacement and plastic strain of M thread and MJ thread were analyzed numerically.The places where plastic yield occurred first for MJ thread when selecting different materials were mainly discussed and reasons were analyzed.It was found that when the nut material is 30 CrMnSiA,the fastener thread can achieve a more uniform bearing relatively.(2)Study the relationship between bolt torque and preload force based on a refined model.In the bolt loosening process under the harmonic load,considering the details of the screw contact surface,the nut contact surface and the influence of various factors on the bolt tensile force,the secondary development with ABAQUS software,established three bolt models,and perform mechanical analysis.The fine model can accurately simulate the relationship between torque and preload force.Under the harmonic load,the variation law of the bolt tension force in the fine model was analyzed,and the relationship between the resultant moment,contact pressure and friction stress to the origin moment was discussed.The classification of different influencing factors was studied,and the variation of mechanical parameters in the loosening process was summarized.(3)The nuclear blasting valve is a key protection device for a new generation of nuclear power units.During normal operation,the valve body is required to have zero leakage.In order to study the mechanical properties of the bolted joints and the tightness of the gasket under the effect of heat and working load.A refined finite element model that can accurately describe the thread details was established.The nonlinear behavior of the gasket was considered.GASKET elements in the ABAQUS software were adopted.The temperature field and stress field of the blasting valve and the bolt tension force were analyzed.The moment when the lowest tensile force of the bolt was found,and the sealing performance of the gasket was evaluated at this time.The relationship between the state change of the screw contact surface and the tension force of the bolt,The percentage of bolt tensile force for each fastener thread,the angle of the nut rotation and the tension force of the bolt were analyzed.It can be seen that the fine model can more realistically simulate the change of the tensile force of the bolt.(4)The sealing performance of the reactor pressure vessel and the mechanical properties of the bolted joint were analyzed.The finite element model of the container was established.The nonlinear behavior of the C-shaped seal ring was considered.GASKET elements in the ABAQUS software were adopted.The temperature field and stress field,and the bolt tensile force were analyzed.The moment when the lowest tensile force of the bolt was found,and the sealing performance of the inner and outer gaskets was evaluated at this time.The variation of bolt tension force under different preloads and different pressures was studied.The comparison of the model with and without gaskets showed that the calculated results of the fine model with gaskets were more realistic.Comparing the results of the fine model and the simplified model,it was found that the trends of the bolt tension force of the two models are basically the same.