Simulation A Nalysis And Experimental Study On Contact Stiffness And Damping Of Serrated Lock Washer

Serrated joint surface has a wide range of applications in the fields of agricultural machinery,aerospace and rail transit.The contact stiffness and contact damping of the joint surface have a significant impact on the static and dynamic characteristics of the mechanical structure.Contact damping can reduce the vibration,but excessive damping influences the contact stiffness and dynamic performance of the mechanical structure.Therefore,the law of energy dissipation and contact characteristics of the serrated joint surface should be studied,and the contact stiffness and contact damping should be controlled within a reasonable range.In this paper,the serrated lock washer was taken as the research object,and the simulation calculation and experimental research on the contact stiffness and contact damping of the serrated joint surface were mainly studied.The main research contents and conclusions of this paper include:Loosening reasons and locking measures of bolt structure were analyzed.The structure and working principle of serrated lock washer are introduced.Based on the contact fractal theory,the normal contact stiffness and contact damping fractal model of the joint surface were established.The effects of normal load,contact area and loading times on contact damping were analyzed.In order to explore the influencing factors of contact stiffness and contact damping,a bolt-connected cantilever beam structure test bench with serrated lock washers was built.The first four natural frequencies and the first two damping ratio of the cantilever beam structure were tested.The influence of bolt preload,contact area and loading times on the natural frequencies and damping ratio were analyzed.Theoretical analysis and experimental research have the same conclusion.The experimental results show that the first four natural frequencies of the cantilever beam structure increase with the increase of the bolt preload,contact area and loading times;the first two damping ratio of the cantilever beam structure decrease with the increase of the bolt preload,contact area and loading times.The first-order bending amplitudes of different positions of the cantilever beam under the excitation of JZ-5 exciter were measured,and law of change with the preload was found.It is found that the first-order bending response amplitudes decrease with the increase of preload.The finite element model of the bolt-connected cantilever beam structure with serrated lock washers was established,and the first four natural frequencies of the structure under different bolt preload were obtained;The finite element model of the bolt structure with the serrated lock washer was established and different bolt loads were applied to the model.The dynamic contact stiffness of the serrated joint surface was obtained.Through the harmonic response analysis,the first-order bending response amplitude of the cantilever beam structure under different bolt preload was obtained and compared with the experimental results.The results show that the simulated first-order bending response amplitude matches the experimental results.