Welding Numerical Simulation Of TBM Cutterhead Supportand Analysis On Microstructure Of Its Welded Joint

The tunneling construction technology and TBM(Tunnel Boring Machine) has been vigorously promoted and widely used along with lots of infrastructure projects such as large tunnel engineering being carried out in our country. Our country has a huge market of TBM construction, but only few enterprises have mastered the TBM tunneling technology, the level of independent research and development and manufacturing is relatively backward. Therefore, it is of great significance to research and develop TBM, especially the core technology research on manufacturing of the key parts.The research object of this thesis is TBM cutterhead support, this research subject is derived from the 863 program “Key technology research and application of large-diameter hard rock tunnel boring equipment”. Cutterhead support is the driving box of TBM, which bearings the axial thrust and torque in the process of tunneling. Cutterhead support is box structure welded with large thickness steel plates, and its welding quality directly affects the performance of the whole TBM. Through the study on the force analysis of cutterhead support, numerical simulation of the welding temperature field and stress field, microstructure experiment of T joint and research on other aspects, this thesis aims to provide theoretical support for the development and improvement of manufacturing process on TBM cutterhead support. The specific research contents are as follows:(1) Calculate the maximum load cutterhead support bearings in the process of tunneling through its inner transmission principle, and perform static analysis with finite element method.(2) Select the structure of stress concentration on TBM cutterhead support as research object, build finite element model of the typical T joint structure. Set material parameters of thermodynamic properties, the heat source model and welding process parameters. Numerical simulate the welding process.(3) Numerically simulate the temperature field distribution of multi-layer and multi-pass welding process with element birth and death technology. Discuss the thermal cycling curve of key points on each area of welding part, and analyze the accuracy and rationality of the numerical simulation of welding temperature field in combination with the thermal characteristics of the actual welding.(4) Numerically simulate the transient stress field distribution of welding process with indirect coupling method based on the result of welding temperature field. Discuss the distribution of welding residual stress along different paths, and compare the residual stress generated in different welding processes.(5) Perform metallographic experiments on welded joint. Observe and analyze the microstructure characteristics in the areas of welding bead, heat affected zone and base metal. Discuss the quality of welded joint and provide guidance for the welding process.