Welding Simulation Of Large-scale Penstocks And Numerical Analysis Of Defective Weld

With the continuous development of our country's industry,the application of welding technology has become more and more extensive.People's understanding and research of welding have become more and more in-depth.The welding stress refers to the structural stress formed by the thermal stress during the welding process of the component.The welding instantaneous stress changes rapidly with time.The welding residual stress is the final formed stress that does not change with time.It is generated by the welding heat source.Caused by uneven temperature field.Correctly understanding the formation mechanism,role and influence of welding stress and deformation has a very important role in improving the manufacturing quality and service performance of welded structures.Due to the complicated welding process,long welding cycle,and difficulty in calculation and analysis,the stress state and distribution characteristics of large-thickness weldments have so far been the focus of research.However,due to the wide application of large-thickness welded structures in important industrial applications,more and more attention has been paid to the study of stress states and characteristics of such welded structures.Based on the development basis of modern computer technology and information technology,this paper explores the distribution characteristics of the temperature field and stress field of large-scale penstocks and welds with defects in a hydropower station in Yunnan using finite element numerical methods.The main research content of this article is as follows:1)The inner diameter of the water diversion pipe on the right bank of a hydropower station in Yunnan Province is 11500 mm,and the wall thickness is 60 mm.It belongs to super-large pressure pipe.When it is used as a research object for welding simulation,a reasonable geometric model of the model is first simplified,and the grid is divided by sweeping.Establish its finite element model.2)Programming ANSYS welding parameterization language the APDL command flow implements the "heat" and "death" of the heat source model and the control unit.By analyzing the temperature field of the simplified finite element model,the distribution of temperature field during the welding process of large-scale penstocks is obtained.Based on this,the changes of the node temperature along the path with time and the effect of thermal cycles between layers are discussed.3)Using indirect coupling method,the distribution of welding residual stress of large-scale pressure steel pipe is obtained.Comparative analysis of the welding residual stress and equivalent residual stress in each direction,and study the stress distribution along the path.4)Three finite element models were established for defect-free,0.5mm undercut and 1mm undercut.The welding temperature field and residual stress field were solved.The effect of different undercuts on welding temperature field and welding residual stress was discussed.Through the research on the welding of penstocks used for water diversion of a certain hydropower station in Yunnan,some valuable analysis results have been obtained,which provide some guidance for the construction of large-scale penstocks.At the same time,through the study of the welds containing defects,it can also provide theoretical guidance for the treatment of defective welds,especially the elimination of welding residual stress.