Papers by Keyword: Welding Distortion

Abstract: Welding distortion remains a significant challenge in vehicle structures incorporating aluminum components. This study investigates the application of pre-tension to mitigate welding distortion in an aluminum T-joint structure. Through finite element (FE) simulation, the mechanism by which pre-tension alters the residual stress state and reduces distortion is analyzed and comprehensively explained. Based on the findings, an optimized pre-tension condition is proposed to minimize welding distortion in the T-joint configuration.

Abstract: Submerged arc welding (SAW) process is extensively used in major industrial application such as wind turbine towers and ship building industries for joining of larger thickness (~10 to 50mm) of similar and dissimilar materials. However, other joining processes are not popular to weld larger thickness compared to SAW. In welding, one of the major problems is distortion, which destroys the dimensional stability of the component, a major concern in manufacturing. Simulation of larger thickness component will increase the simulation time. Therefore, an attempt has been made to evaluate a 3 - dimensional finite element analysis (FEA) using SYSWELD to study the effect of the joining of two similar shells of High Strength Low Alloy (HSLA) steel through scale down model in the ratio of 10:1. To reduce the simulation time, the two shells of steel having 400mm diameter and 2mm thickness are modelled and simulated with single pass GMAW process using eight different welding sequences as per welding procedure specification (WPS) using SYSWELD. Results show the simulated welding sequence no. 4 has a considerable amount of reduction in distortion of 1.526 mm compared to that of other sequences. Welding sequence no. 4 is then followed by actual windmill tower fabrication, which resulted in reduced distortion level of 5 mm.

Abstract: The welding involves the transfer of high localized heat flow, which results in residual stresses in the welded body. The impossibility of relieving these stresses generates welding distortions that become a problem in dimensional setting of welded structures. This study aims to evaluate the influence of some parameters in the welding process in a T-type joint. Due to the complexity of the welded joint and the deposition rate, a three-dimensional finite element model was developed for the solution of the temperature field and distortions. The transient thermal analysis used the Goldak equation for definition of the heat flux transferred to the part. The nonlinear characteristics of the phenomenon as well as the dependence of physical and mechanical properties with the temperature were considered in this work. The parameters studied were the welding speed, welding sequence and cooling time between weld beads. The results suggest that the higher welding speed, the welding sequence forward and back and with cooling interval between beads present themselves as the best parameters for welding with lower distortions.

Abstract: This paper presented a detailed finite element simulation on the basis of elastic-plastic method combined with thermo-mechannical coupling algorithm，and the software abaqus was used for the welding simulation of thin-walled 6061-T6 aluminum. The residual stress and distortion with various types of welding sequence were investigated and the optimal welding sequence was gained through comparison and analysis. The results showed that the maximum residual stress on the plane of the welds was tensile stress after welding in a rectangular. The method of symmetry welding got smaller residual stress which could enhance the stability of the weldments, and starting from a longer welding path got smaller residual distortion of aluminum alloy.

Abstract: The manufacture core of CRH380 high-speed train is aluminum alloy welding technology. However, welding residual distortion which occurs in welding process brings unfavorable effect on the quality of high-speed train. As a result, welding distortion forecasting and control become an important and urgent research topic in railway vehicles. Using equivalent thermal load method based on inherent strain given by the formulae, the welding distortion of aluminum alloy side-wall was predicted by an Elastic FEM which consider actual welding conditions. The simulation results were compared with experimentally measured data to evaluate the validity of the model and to verify effectiveness of this method for large-scale welding structure which had long seams.

Abstract: A typical case of integral all-welded panel joints on Shanghai Minpu Second Bridge is discussed in this paper. The prediction of welding residual stresses at joints is achieved by thermal elasto finite element analysis, and the research reveals that a proper scheme of multi-layer welding craft will reduce welding distortions and residual stresses through mutual offset. The welding distortions at upper and lower chord joints (Type I) and those of the overall structural model are predicted with the distribution of residual stresses obtained. The research aims to provide a theoretical basis for the control of welding distortion, the optimization of welding craft and the constitution of optimal assembly welding craft.

Abstract: Welding residual stress and subsequent distortions are a common problem during fabrication. Several techniques for controlling residual stress and distortion during welding, amongst which transient thermal tensioning is one of the more promising methods. Thermal tensioning can be achieved by two side heaters moving along with the weld heat source. The concept of transient thermal tensioning induces a redistribution of the stress field in the welded plate by altering the thermal field. In this paper, the results are presented on the mitigation of out-of-plane deformation during gas tungsten arc butt welding of 2 mm thick AISI-316L stainless steel. Acetylene-air burners are applied as side heaters. The thermal tensioning process induces a number of additional process parameters including the intensity, the size and the location of the heaters. A thermo-mechanical (TM) finite element model is used to cope with the complexity of the process. The model provides a better understanding of the development of the stress field, both in conventional and transient thermal tensioned welds and of the mechanisms which mitigate distortion. The model is validated by temperature, stress and distortion measurements. It appears that the redistribution of stresses and the introduction of tensile stresses by side heating is the main mechanism responsible for the reduction of distortion.

Abstract: The control of welding distortion during assembly process is very important. At present, there are mainly two numerical simulation methods for the welding distortion which are thermo-elastic-plastic finite element method and its simplified approach of inherent strains. At first, taking T-joint as an example, the welding distortions were computed using two methods mentioned above. Based on thermo-elastic-plastic finite element method, welding process was simulated by life and death element, moving heat source and transient state thermal field etc. Then, the welding distortion was calculated by inherent strains method after thermo-elastic-plastic computation. It was concluded from the comparison that the simulation results by using the two methods are consistent. Therefore, the inherent strains method can be conveniently and economically applied to prediction of structural welding distortion in engineering. Applied the inherent strains method, welding deformation was predicted for the bogie frame side beam of high speed train. According to the deformation results from the finite element analysis, the welding deformation of the bogie frame side beam was lager than the tolerance of quality and in reasonable agreement with the experimentally determined distortion values. The work in this paper indicated that the inherent strains method was effective to predict the welding deformation so as to control the welding quality in large complex structures, such as the bogie frame of railway vehicle. Key words: welding distortion; thermo-elastic-plastic method; inherent strains approach; numerical simulation; bogie frame;

Abstract: TA15 airplane wall panels are used widely in aircraft manufacture, which consist of some reinforced ribs and a motherboard. Therefore, welding sequences of different reinforced ribs directly determine distortion and residual stress distributions of welding wall panels, and then affect the structure service performance. Therefore, it is important to get the optimistic sequence during manufacture processing of welding wall panels. This paper analyses and predicts regularities of distributions of residual distortion and stress under four kinds of different welding sequence namely, order welding sequence, head-tail welding, head-tail symmetry welding and center symmetry welding. Compared the distortion and residual stress of four kinds of sequences, it is obvious that the welding distortion is smaller and welding quality is better under head-tail symmetry welding sequence, and the order welding sequence is the worst. The simulated distortions are in good agreement with the experiments. So this study puts forward the best welding sequence when welding airplane wall panels, which adapt to any amounts of reinforced ribs welded with the motherboard.

Abstract: This work deals with the welding simulation by the Finite Element Method (FEM). For the tube plate welding structure features of Membrane water-wall, the numerical computation method is applied to do the real-time simulation research on the temperature field and stress field during the welding process. The implemented models include a moving heat source, temperature dependence of thermo-physical properties, elasto-plasticity, non-steady state heat transfer, and mechanical analysis. The thermal problem is assumed to be uncoupled from the mechanical one, so the thermal analysis is performed separately and previously to the mechanical analysis at each time step. The mechanical problem is based on the thermal history. A special treatment is performed on mechanical elements during the liquid/solid and solid/liquid phase changes to account for stress states. The established simulation analysis method of welding temperature and stress field can provide theory foundation and direction for optimizing the welding structure design and standardizing the welding parameter.