Research On Fatigue Life Prediction And Remanufacturing Scheme Of TBM Cutter-head

At present,the contradiction between economic development and resources and environment has become increasingly prominent due to the rapid growth of population and the excessive dependence on resources by the accompanying economic model.The problems caused by serious environmental pollution,huge resource consumption and low recovery rate have become the bottleneck for China's economy to maintain sustainable development.As a pioneer of green manufacturing,the remanufacturing industry is one of the important ways to develop a circular economy and build a conservation-oriented society.It has been highly valued by the state and society.As a complex large-scale mechanical and electrical product,the implementation of remanufacturing of tunnel boring machine can not only improve the technical performance of the machine,maximize the residual value,but also save resources and reduce environmental damage effectively.As the core component,cutter-head is the key to the remanufacturing of tunneling boring machine.And whether the cutter-head has residual fatigue life is the precondition for its remanufacturing.Therefore,it is of great significance to study the residual fatigue life and remanufacturing scheme of cutter-head for the development of the remanufacturing industry of tunneling boring machine.Based on the analysis of relevant research at home and abroad,the fatigue crack growth characteristics of TBM cutter-head and the interaction between near cracks are studied.Based on the crack damage characteristics,the residual fatigue life prediction model of the cutter-head is established,and the overall remanufacturing scheme for TBM cutter-head is proposed.The main contents of this thesis are as follows:(1)A numerical method for solving the stress intensity factor(SIF)by combining the extended finite element method(XFEM)with the sub-model technique is established.The propagation characteristics of cracks in the dangerous area of TBM cutter-head are analyzed by using the stress intensity factor theory,and the effects of the position angle,shape and size of cracks on the propagation of the cutter-head cracks are studied.The results show that during the propagation of the cutter-head crack,the type I crack plays a leading role,and the crack mainly propagates toward the short axis.(2)The interference coefficient between near double cracks is defined,and the influence of relative position,size and shape of cracks between near double cracks in the dangerous area of TBM cutter-head on the interference coefficient of cracks is studied.It is found that when the near cracks are distributed vertically or collinearly,the interference between the two cracks is the strongest,and the most serious impact on the residual fatigue life of the cutter-head.(3)The prediction model of residual fatigue life of TBM cutter-head is established by using statistics and finite element method.Based on the above model,the influence of the speed of cutter-head,penetration of tunneling and cutter wear degree on the residual fatigue life of cutter-head is studied.The residual fatigue life of the cutter-head varies with the increase of the rotational speed of the cutter-head in a cosine-like curve.With the increase of penetration,the residual fatigue life of the cutter-head decreases gradually and the speed of reduction decreases slowly.When the normal wear amount of cutter reaches 14 mm,the residual fatigue life of the cutter-head decreases linearly.(4)Based on the redundancy strength theory,the failure rule of mechanical products and the minimum service life requirement,the critical residual fatigue life threshold of the remanufacturing of TBM cutter-head is determined,and the overall scheme model of the remanufacturing of TBM cutter-head is established by considering the life characteristics,reliability,geological matching and technical,economic and environmental factors.