Research On Dynamic Simulation Analysis Method Of Bolted Joint Structure

With the development of Chinese modern industry,various large-scale equipments emerged one after another.These equipments are often not integrally forged and generally require assembly through jointed structure.The bolted joint structure has the advantages of easy disassembly,convenient use,high reliability and is widely applied.The bolted joint system exhibits different mechanical properties under different load environments.How to model the bolted joint system and study its influence on the overall structural dynamic behavior is an important subject in current research.Under above background,the research on numerical analysis method of bolted joint structure dynamics is of great significance to the safety and reliability of combined structure which includes bolted joints.In this paper,the following research is carried out on the bolted joint dynamics:Firstly,the bolted joint system is modeled based on the Iwan model,and dynamic characteristics under free vibration and cyclic loading are discussed.It is simplified into a spring vibration system.The system dynamics equation is established to simulate the nonlinear slip behavior of the bolted joint interface.Giving initial slip condition,the harmonic balance method and fourth-order Runge-Kutta method are used to caculate free vibration response and steady state response under cyclic loading.Furthermore,system’s uncertainty analysis is carried out to study the influence of slip stiffness randomness on system response with Monte Carlo method.Then,the equivalent linear model of the bolted plate is established,which has large contact area,and the statistical characteristics of structural response are analyzed under random load.The cone-frusta method and array springs are used to simulate bolt contact area and contact area between the plates.Based on the modal information,bolt layout design is achieved,controlling the overall frequency of structure.Using two-degree-freedom model verifies the correctness and feasibility of solving random vibration problem by pseudo-excitation method and commercial FEM software.Based on above,the random vibration problem of the large contact area bolted plate is studied.Finally,the research on the dynamic fatigue problem of through bolt in low-speed diesel engine is carried out.Considering the overall dynamic response of the low-speed machine under the working load,the local complex load of the through bolt is extracted as the force boundary condition.3D solid finite element model of through bolt is established to obtain time-domain stress response by explicit dynamic analysis.Then the fatigue life is estimated by using Fe-safe software and the strength check is carried out by minimum invariant stress caculation method under asymmetric cyclic loading to ensure engineering needs are met.