Vibration Characteristics Analysis And Optimization Ofconnecting Bolt Sets Used In Walking Frame And Track Frame Of Mine Excavator

Mining excavators are a very important part of mining machinery and play a decisive role in mining operations.Excavator walking frame and track frame connection mechanism of mine excavator is often in a bad environment and is often subjected to various impact loads,and its connection performance directly affects the work performance and operation safety performance of the excavator.Therefore,it is necessary to study the vibration characteristics of the connection bolts of walking frame and track frame of mining excavators,and optimize the parameters of the connection bolts to improve the service life of the bolts and improve the safety factor of the excavator.This article takes the WK-75 mechanical excavator as an example.The main research contents are as follows:(1)Using UG and RecurDyn software to set up a complete machine model and simulate the walking movement in a typical working condition to obtain the load spectrum of the connecting bolt set.The Fourier transform of each load spectrum is used to obtain the frequency and amplitude of the main load component of the load spectrum.It is found that the frequency and amplitude of the main load components may be related to the turning radius of the excavator.Different steering radius simulations are performed and the load spectrum is Fourier transformed to obtain the frequency and amplitude of the main load components.Taking the turning radius as an independent variable,the main load component frequency and amplitude are dependent variables.The fitting curve obtains the functional relationship between the frequency and amplitude of the main load component and the turning radius.(2)The reference document specifies that the load amplitude when the bolt is loosened is the analysis threshold value,the steering radius range that causes the loosening of the bolt group is found by the function of the amplitude of the main load component,and the structure is inherent in the modal analysis of the walking chassis and the track frame assembly.At the frequency,the turning radius of the resonance of the coupling bolt group is obtained by the frequency function of the main load component.Compare the turning radius that causes the bolt group to loosen and the steering radius that causes the bolt group to resonate.The overlapping radius is a dangerous condition in which the bolt group loosens and resonates.(3)The dynamic curves of dangerous working conditions are obtained and the displacement curves of each roller are obtained.The frequency and amplitude of the main displacement components are obtained by Fourier transform.The main displacement component amplitude is used to analyze the displacement constraints of the harmonic response,and the main displacement component frequency range is the harmonic response analysis.Sweep range,analysis of overall model harmonic response.Comparing the maximum displacement of each bolt vibration under all dangerous working conditions,the condition with the largest bolt vibration displacement is the most dangerous working condition.(4)The submodel method and genetic algorithm are introduced.The aim is to minimize the vibration displacement of bolts.The design parameters are the pitch,bolt center hole diameter,pretightening force and bolt diameter.The optimization algorithm uses genetic algorithm to establish the sub bolt model Initial optimization.By analyzing the influence of each design variable on the vibration displacement of the bolt,the best combination of design variables is obtained.The bolt structure is secondarily optimized to obtain the best optimization solution.The correctness of the optimization results was verified by comparing the maximum bolt vibration displacements.Through structural optimization,the maximum vibration displacement of the bolt is reduced from 1.26513 mm before optimization to 0.33584 mm,a drop of 73%,and the maximum stress is increased from 215.32 MPa to 337.57 MPa,but is still within the yield limit of the bolt material,and the maximum utilization is achieved.The material extends the life of the bolt.