Research On The Influence For Weld Residual Stress And Weld Numerical Simulation Between Hollow Ball And Pipe

The welded hollow spherical joint is a common joint used in the long span steel structures, but there exists complicated residual stress in such joints for their weld forming way engendering residual stress easier. Researching on the residual stress distribution and magnitude can be helpful to the application of such joint in project. And the development of numerical simulation methods provides the vigorous condition for the progress of the welding technique, and conduces a leap from experience to science and from qualitative analysis to quantitative analysis in the welding technique development. It can be brought about a reduction in the practice cost in project when combining numerical simulation method with experiment method to solve welding residual stress problems.In this thesis the ANSYS software is applied to simulate the welding process. With its APDL language some programs are programmed to create the geometric model and FEM model in the case of single pipe, double pipes and four pipes with hollow sphere welding respectively, and to control the simulation of temperature, stress, and strain field with the birth and death function. As the design code of welded hollow spherical joint steel grid requested, some factors are considered about such as the diameter, thickness of hollow spheres and diameter of pipes and the welding speed and welding sequence to study its influence on the distribution and magnitude of temperature, stress, and strain field. The result can provide guidance and be consulted in projects. Based on the forenamed result, the influence on the distribution and magnitude of temperature and stress field in the case of double or four pipes welding with hollow sphere are studied about the degree between the tow pipes or four pipes, and the stress distribution in different path has obtained at the end.The resolving process on the welding damage problem is deduced in the thesis combining the damage theory and the basic theory of initial stress problems and the static mechanics performance of such joints are provided with comparative analysis between the one with initial stress damage and the one without by Ansys software. The conclusion can be draw that the initial stress is not influent to the static strength of the joint but to the stiffness reducing seriously.In order to check the reliability of the numerical simulation, two weld joints residual stress testing experiment are made with blindhole method in the weld. Through the experiment it can find the depth of the blindhole is related with diameter of drill and the simulation result is in keeping with the experiment result to a certain extent.All in all, the research will be helpful to know the residual stress distribution and the practical methods to reduce the residual stress in the joint and the result can be refered to in projects.