Welding Deformation Predicting, Controlling And Applying For Box Structure

Box-shape welding structures have been widely applied in the various industrial fields. Like other welding structures, because of the unbalanced heating/cooling, these box-shape ones inevitably produce the residual deformations that should not be neglected. The welding residual deformation is the crucial influential factor in the design integrality, the rational manufacturing techniques and the service durability of welding structures. But the additional procedures, such as deformation rectification after welding, are expensive and liable to impair the service durability. So the scientific and quantitative predicting of welding deformation regularities and, thereon, taking the optimal quality-control measures, have theoretical values and engineering significance in the integral design, manufacturing technique selection and the service security evaluation of box-shape welding structures themselves, as well as other kinds of welding structures.Based on the summary of the domestic and foreign studies on welding deformation, a series of investigations were made gradually on the high-speed electric locomotive bogie, which composed of the box-shape welding frame and other parts, in analytical theory, digital simulation, experimental validation and the optimal realization of welding sequence, respectively. And the study works and achievements are summed up as follows:After detailed analysis of the classical weld contracting force method, which is considered as a loading manner in FEM model, therefore, a rapid estimation calculation technique for the wholly welding deformation is formed firstly in combination with the finite element method. This calculating technique then attempts to be applied to the box-shape-section lateral beam in the bogie's frame of SS7E electro-locomotive in order to obtain the FEM calculating results. To validate the fitness of this technique, the actual welding deformations are measured after welding. And comparing with the above calculating results, both are found to be consistent with each other. Sequentially, the above technique is further applied to the bogie's frame of high-speed driving locomotive , which has more complicated structure and more welds, and is required more tough requirements for service durability. Since the box-shape frame and other parts are investigated separately in this stage, the regularities of the wholly frame's welding deformations and their main manufacturing influential factors are becoming clear.Because the independent influential problem of every weld can not be analyzed by the oriented-to welding contracting force FEM, another calculating technique was proposed according to heat-elastic-plastic mechanics, that is, to establish the heating-elastic-plastic simulation model based on heating-mechanical coupling algorithm, which is present hot-topic study in this domain, but a very hard difficulty in the calculation. To avoid the problems in such large complicated simulation model that is manipulated in the low-efficiency, the following novel strategies are taken in establishing this kinds of simulation models, such as the active/inactive element strategy, adaptive mesh strategy, subsection heat-source strategy, parallel-treatmentstrategy and so on, which can catch the main relationship in the most complicated welding process simulation so that the conclusions are able to be applicable in the real engineering problems.To make sure that these achievements can be practicable in engineering, a number of strategies in establishing the complex models are also presented to normalize mechanical boundaries, thermal boundaries, initial boundary conditions, geometric boundaries and material properties. Based on the normalized finite element model, the above bogie frame's lateral beam of the high-speed driving locomotive is calculated again, respectively studying the effects of box structure welding sequence, welding heat input quantity, constraint condition and internal structure to welding deformations. And the rules of welding sequence, heat input quantity, constraint condition and internal structure impacting on welding deformations are found out to provide numerical evidences for the welding deformation control of box-shape structures.The above study works, especially, the presentation and corresponding techniques of the orient-to heat-elastic-plastic simulation models, make possible to optimize the welding sequence. Since the specialty in the welding sequence optimization, it is difficult to set up the optimizing model that the sensitivity analysis or the differential algorithm can be applicable. The heredity arithmetic, however, can be applied in the paper without differential algorithm. During to this kind of heredity arithmetic combining with the heat-mechanical nonlinear finite element model presented in the paper, the welding sequence optimization finally achieves the several obvious developments. A representative welding sequence optimization of box-shape welded beam is proved that this technique has important practical application in the future.It should be pointed out, in the end, that the method which takes the mean square deviation as welding deformation norm to measure welding deformations of all the points in the structure, and the study on the effects of box beam's internal structure to welding deformation, both make possible that the multi-constraint optimization to be applicable. This feasible route investigation of the multi-constraint optimization also has important theoretical values.