| The heavy-duty scraper conveyor is the a equipment for high-yield and high-efficiency mechanized coal mining,and it undertakes important tasks such as coal transportation,shearer operation guide,and fulcrum points for hydraulic support.The scraper chain is one of the key components of the heavy-duty scraper conveyor,and there are various failure mechanisms such as fatigue,corrosion,and wear.In the using process of the scraper chain,it has to withstand the comprehensive effects of impact,wear,corrosion and fatigue.Therefore,the scraper chain has a variety of different failure modes and is prone to failure.Once the scraper chain fails during use,the coal mining operation will be suspended at the fully mechanized mining face,which will seriously affect the mining efficiency of the fully mechanized face.In addition,with the continuous development of our country’s coal mines in the direction of deepening and large-scale,the requirements for the transportation capacity,distance,strength,reliability and intelligent level of scraper conveyors are getting higher and higher.Therefore,it is of important theoretical significance and practical value to carry out research on the reliability evaluation of the scraper chain for the heavy-duty scraper conveyor to break through relevant key technical issues.This dissertation is funded by the Joint Fund Key Project of National Natural Science Foundation of China "Basic Research on Intelligent Driving System of Heavy-duty Scraper Conveyor"(Item Number: U1510205).Based on the engineering background of heavy-duty scraper conveyors for coal transportation,taking scraper chains as the research object,combining mechanical reliability with reliability mathematics,reliability physics,material strength,failure analysis,etc.,the reliability of the scraper chain is analyzed from multiple perspectives of catastrophic failure,degradation failure,and dependent competing failure.First of all,according to the structural characteristics and working environment of the scraper conveyor,the polygon effect of the sprocket,the coal falling law of the shearer,and the interaction between the scraper chain and coal,etc.are considered.Based on the finite element method,the dynamic model of the scraper conveyor is established and solved by the Hilber-Hughes-Taylor method.The tension fluctuation law of the scraper chain is obtained.Field experiments and case analysis verified the effectiveness of the model.Secondly,in view of the problems related to the strength and stiffness of the scraper chain with multiple failure modes,a reliability model is established for each failure mode,and the reliability of each failure mode is evaluated by the random perturbation technique and the fourth-order moment method;the Copula function is introduced to describe the failure mode,AIC value is used to determine the optimal Copula function;based on the Copula function and the narrow-bound theory,a system reliability model under multiple failure modes is established;a reliability evaluation and design optimization method for scraper chain system with multiple failure modes is proposed;The validity of the model is verified through case analysis.Thirdly,a study on the reliability evaluation and design optimization of the scraper chain based on Skidding wear between scraper chains is carried out.Based on the dynamic tension of the scraper chain and the external contact model of the sphere;a wear model between scraper chains is established;the wear volume of the scraper chain is converted into the diameter wear rate of the scraper chain through the spherical cap model;a wear-based reliability model between scraper chains is established based on the third-order moment saddlepoint approximation method;the time-dependent reliability analysis and design optimization research based on the wear between scraper chain are carried out;the effectiveness of the model is verified through an example analysis.Then,according to dynamic tension and the stress analysis of the scraper chain,the equivalent stress of the scraper chain is obtained;considering the influence of corrosive wear,a fatigue crack model is established based on the revised Paris law;based on the fourth-order moment saddlepoint approximation method,the fatigue reliability of the scraper chain under the interaction of corrosive wear and fatigue cracks is evaluated;the scraper chain is optimized based on the reliability design optimization theory;the effectiveness of the model is verified through an example analysis.Finally,in view of the multiple catastrophic failures and degradation failures of the scraper chain,an extreme shock model that obeys the non-homogeneous Poisson distribution and a strength degradation model based on the nonlinear fatigue damage criterion are constructed;considering the interaction of catastrophic failure and degradation failure,a competing reliability model for multiple catastrophic failures and degradation failures is established with the mutual influence of shock and degradation.And then the time-dependent Copula function is used to analyze the correlation between each failure mode,and the scraper chain dependent competing failure reliability model is established;the established dependent competing failure reliability model of the scraper chain is verified through an example analysis.There are 72 figures,27 tables and 210 references in this dissertation. |
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