| The shearer is an equipment with low speed and heavy load.The stick-slip friction and collision impact between the sliding boots and the guiding rail are the root causes of wear and fracture failure of the sliding boot and the pin row.Due to the influence of coal powder particles in the gap between the sliding boots and the guiding rail,the time variation and complexity exist in the process of the friction and contact between the sliding boots and guiding rail.Due to the influence of geometric matching shape between the sliding boots and the guiding rail,there are multi-surface contact collision and friction behaviors between the sliding boots and the guiding rail,thus,between the shearer and the scraper,the three-body,multi-surface contact stick-slip vibration behavior with gap collision exists.The combination of theoretical modeling,numerical method and experimental verification is employed to reveal the mechanical mechanism of action between the shearer and the scraper in the paper.The main contents are as follows:To reveal the stick-slip friction mechanism of the shearer sliding boots,i.e.,the guiding boots and the flat boots,taking a guiding boot and a flat boot as the research objects,the contact forms between the guiding boot and the pin row and between the flat boot and the coal shovel are discussed based on the modern contact theory,the calculation models of boot contact forces for quadrilateral,polygonal and line-surface contact are established respectively.Based on the stick-slip friction theory and the three-body friction theory,the friction mechanical models between the guiding boot and the pin row and between the flat boot and the coal shovel are set up,also the three-body friction mechanical model between the sliding boots,the guiding rail and the coal powders is constructed.The effects of surface roughness and particle size of coal powders on the friction force of sliding boots are studied.The results show that the rougher the contact surface is,the more obvious lubrication effect of the coal powder on the sliding boots under gap filling is.To construct the vibration model of shearer walking unit under complicated working conditions,the key components such as the drive wheel,the guiding boot and the flat boot of shearer walking unit are studied.The meshing vibration model of the drive wheel is constructed considering the bearing supporting action,and the meshing stiffness equation is derived based on Hertz contact theory.Taking the contact collision vibration model of the guiding boot and the pin row and that of the flat boot and the coal shovel under the shearer twist,and based on the sliding boot contact model constructed in Chapter 2,the contact stiffness calculation equation of thesliding boot with clearance is derived.To deeply study the influence of working condition on the vibration characteristics of the shearer sliding boot,by combining the stick-slip friction model of the shearer sliding boot,the dynamics models of guiding boot,of flat boot and of drive wheel,the dynamics models of shearer walking unit under normal cutting,pitching,rolling and chamfering conditions are constructed.The influences of shearer pitch angel,side inclination angle and the swing angle to the vibration characteristics of shearer sliding boot are studied.The results show that with the increase of the pitch angle,the vibration characteristics of the guiding boots and the flat boots change significantly in the y direction,the vibration acceleration of the forward guiding boot and the forward flat boot increase the most,which indicates the larger the pitch angle,the more intense the vibration of the forward guiding boot and the forward flat boot.With the increase of the roll angle,the vibration characteristics of the sliding boot and the flat boot change significantly in the y direction,the vibration accelerations of the forward sliding boot and the rear sliding boot are negatively correlated,which indicates the larger the roll angle,the smaller the vibration ranges of the forward sliding boot and the forward flat boot,the vibration of the flat boot in the y direction is the opposite,the larger the roll angle,the more intense the vibration,and influences of the roll angle variation to the vibrations in the x and z directions are small,and only with slight fluctuations.With the increase of the swing angle,the vibrations of the guiding boot and the flat boot change most significantly in the y direction,followed by the vibration accelerations of the forward guiding boot and the forward flat boot increase in the x direction.It shows that the larger the swing angle,the more intense the vibration of the forward guiding boot and the forward flat boot in the x and y direction,while the vibration of the rear flat boot in the x direction and that of the rear guiding boot in the y direction are on the opposite,and with the swing angle increases,the vibration decreases;but the change of the swing angle has no obvious effect on the vibration in the z-direction,with only slight fluctuation.With reference to shearer MG500/1130,the shearer MG500/1130 is scaled by 1: 10 according to the principle of similarity,the experimental prototype is processed and the walking unit is tested.Taking working condition,excitation,friction and speed as the influence factors to the testing experiment,the experiment scheme is determined by employing the orthogonal experimental design method,the vibration signals are obtained by the three-dimensional acceleration sensors installed on the guiding boot and the flat boot,and the influence of working condition,excitation,friction and speed to the vibration of shearer sliding boot are studied by analyzing the experimental results.The research results in this paper provide theoretical support for improving the dynamic characteristics of shearer and optimal design of sliding structure,also provide basis for the study of friction and collision behavior of mechanical system with dust and clearance. |
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