J. D. White

Bio: J. D. White is an academic researcher. The author has contributed to research in topic(s): Shrinkage. The author has an hindex of 1, co-authored 1 publication(s) receiving 29 citation(s).

Numerical simulation of welding distortion in large structures

Abstract: Welding is a crucial manufacturing process and widely used in industries to assemble various products including ships, automobiles, trains and bridges. Welding distortion often results in problems such as dimensional inaccuracies during the assembly and increased fabrication costs. Therefore, prediction and reduction of welding distortion are critical to improve the quality of welded structures. Welding distortion during the assembly process is affected by not only local shrinkage due to rapid heating and cooling, but also root gap and misalignment between parts to be welded. In this study, based on inherent strain theory, an elastic finite element method is developed to precisely predict welding distortion during the assembly process considering both local shrinkage and root gap. First, thermal elastic–plastic finite element method is employed to estimate inherent deformations for different typical welding joints. Second, the proposed elastic FEM is used to predict welding distortion for large welded structures based on the obtained inherent deformations. Meanwhile, the influence of initial gap on welding distortion is investigated. Finally, experiments are carried out to verify the simulated results. The effectiveness of the proposed elastic FEM is confirmed using experimental results.

Determination of welding deformation in fillet-welded joint by means of numerical simulation and comparison with experimental measurements

Abstract: Fillet weld is the most common weld type used in the fabrication of structural members in shipbuilding, automobile and other industries. Fillet-welded joints usually suffer from various welding deformation patterns, such as longitudinal shrinkage, transverse shrinkage, angular distortion and longitudinal bending. Welding deformation has negative effects on fabrication accuracy, external appearance and various strengths of the welded structures. In this study, experiments are performed to investigate the characteristics of welding deformation in the fillet-welded joint. In order to precisely predict welding deformation by numerical method, a 3-D thermal elastic plastic finite element computational procedure is developed. The simulated results are in a good agreement with the experimental measurements. The influence on welding deformation of the flange thickness is investigated by experiment and numerical simulation. In addition, the generation mechanism of angular distortion is clarified through numerical simulation.

Prediction of welding distortion in a curved plate structure by means of elastic finite element method

Abstract: An elastic finite element method (FEM) for predicting welding distortions of large welded structures is developed. In the proposed elastic FEM, the inherent deformation is used to model the local deformation induced by welding, and the interface element is introduced to simulate the joining process and the correction of the gap between the welded parts. In this study, our emphasis is focused on examining the influence of initial gap on the final welding distortion. First, the usefulness of the proposed method is verified by experiment with simple welded structures. Secondly, the welding distortion of an asymmetric curved plate structure without initial gap is predicted using this elastic FEM. Finally, the influence of the initial gaps on the final welding distortion in the asymmetric curved plate structure is investigated.

Effect of jig constraint position and pitch on welding deformation

Abstract: Quantitative study on jig constraint effect on welding deformation was carried out. Welding deformation in a square plate with bead welding under a non-constraint free condition and a jig constraint condition was investigated by experiment. A 3D thermal elastic–plastic FEM program was employed to simulate the transient temperature and deformation occurred in the welding. It is observed that welding angular distortion has been greatly reduced by the jig constraint, and a good agreement was confirmed between simulation and experiment. Three-direction jig constraint and normal direction jig constraint were defined based on typical constraint types in practical engineering. Two parameters a and b , which represent the pitch between two jigs in the welding direction and the distance from the weld line, respectively, were focused. Effect of jig constraint on longitudinal shrinkage, transverse shrinkage and angular distortion were discussed in details.

An efficient FE computation for predicting welding induced buckling in production of ship panel structure

Abstract: In a Thermal-Elastic-Plastic (TEP) FE analysis to investigate welding induced buckling of large thin plate welded structure such as ship panel, it will be extremely difficult to converge computation and obtain the results when the material and geometrical non-linear behaviors are both considered In this study, an efficient FE computation which is an elastic FE analysis based on inherent deformation method, is proposed to predict welding induced buckling with employing large deformation theory, and an application in ship panel production is carried out The proposed FE computation is implemented with two steps: (1) The typical weld joint (fillet weld) existing in considered ship panel structure is conducted with sequential welding using actual welding condition, and welding angular distortion after completely cooling down is measured A TEP FE analysis with solid elements model is carried out to predict the welding angular distortion, which is validated by comparing with experimental results Then, inherent deformations in this examined fillet welded joint are evaluated as a loading for the subsequent elastic FE analysis Also, the simultaneous welding to assemble this fillet welded joint is numerically considered and its inherent deformations are evaluated (2) To predict the welding induced buckling in the production of ship panel structure, a shell element model of considered ship panel is then employed for elastic FE analysis, in which inherent deformation evaluated beforehand is applied and large deformation is considered The computed results obviously show welding induced buckling in the considered ship panel structure after welding With its instability and difficulty for straightening, welding induced buckling prefers to be avoided whenever it is possible