Optimization Design And Welding Analysis Of High Strenth Steel Sheild Cutter Head

Cutterhead is the key part of shield tunneling,and the reasonable design of cutterhead structure is the important guarantee of shield tunneling.In the actual project,the cutter head of shield machine is too large in quality and insufficient in structural space due to design reasons,which causes difficulties in cutter change,mud cake in the center of cutter head and other construction problems,and finally leads to the shutdown of shield machine and delays the construction period,resulting in economic losses.In addition,the cutter head of shield machine belongs to a large-scale welding structure.In its working process,the weld crack of cutter head is one of its main failure forms.The welding quality of cutter head directly determines its service performance and service life.Based on this,under the condition that the strength and rigidity of the cutter head are satisfied,the structure of the cutter head is optimized and studied in this paper.At the same time,the key welding parts of the cutter head are simulated and analyzed.The main work and results are as follows:1.Based on the actual shield engineering,the mathematical model of the shield cutter head under different working conditions is established;the static simulation analysis of the shield cutter head under different working conditions is carried out by using ANSYS Workbench,and the most dangerous working condition in the working process of the cutter head is the maximum thrust condition;The finite element model of cutter head with Q690 as the cutter head frame material is established,and the surplus of strength and rigidity between the cutter head and the original cutter head(Q345C)is analyzed based on the static simulation.The comprehensive comparison shows that the cutter head with Q690 as the cutter head frame material has greater "optimization potential".2.The optimal mathematical model of high strength steel cutter head is established,and the optimal design of the selected design variables is carried out.The radial basis function neural network model is established to replace the finite element model of cutter head.The multi Island genetic algorithm is used to optimize the design of high strength steel cutter head.The mass of the optimized cutter head is reduced by 15%,the opening rate is increased from35% to 40%,and the center opening rate is increased by 8.6%.3.Modal analysis and harmonic response analysis are carried out to verify the dynamic characteristics of the optimized high strength steel cutter head.Based on the ISIGHT software,the approximate model of cutter head is established.Considering the change of material properties and load fluctuation,the first-order reliability method,the second-order reliability method and the Monte Carlo method are used to calculate the reliability of the optimized high-strength steel cutter head structure.The results show that the reliability of cutter head meets the requirements.4.The basic finite element theory of welding numerical simulation and the research method of welding thermal stress calculation by ANSYS are introduced.The finite element model of the key welding parts of the cutter head is established,and the distribution of welding temperature field and stress-strain field is calculated.The effects of different preheating conditions on welding temperature field and stress strain field are discussed.the results show that the distribution of temperature field at the same time under different preheating conditions is very similar on the whole.For both welding and cooling processes,the higher the initial preheating temperature,the higher the maximum temperature at the same time.Compared with the cooling process under the four conditions,the preheating time of t8/5 is the longest when the temperature is 200℃,that is,the control effect of cold crack in welding is the best under this condition.When the preheating temperature is 200℃,the peak of welding stress is the smallest.Under the preheating condition,the peak of welding strain decreases with the increase of preheating temperature,and the lowest peak of welding strain is0.708 mm when the preheating temperature is 200℃.5.The stress distribution of welding structure including welding residual stress under external load is calculated.The results show that the total equivalent stress of the cloud legs is599 MPa under the condition of welding residual stress,while the maximum equivalent stress of the cloud legs under the condition of maximum thrust without considering welding residual stress is 334.25 MPa,which is significantly lower than the maximum equivalent stress under the condition of welding residual stress.At the same time,the compressive stress of the cloud legs in all directions decreases after applying external force The results show that the welding residual stress has a significant effect on the structural stress.