Dean Deng

Prediction of Welding Distortion by Elastic Finite Element Analysis using Inherent Deformation Estimated Through Inverse Analysis

During welding, deformation is produced as an unavoidable consequence. The inherent deformation method, in which the inherent deformation is introduced into the elastic finite element method (FEM) as the initial strain, is one of the effective methods to predict the welding distortion of large structures. However, the values of the inherent deformations for all weld joints included in the structure must be known beforehand. Generally, the inherent deformations are influenced by various factors such as materials, welding method, welding condition, joint geometry, plate thickness, and weld length. Thus, it is meaningful to develop a simple method to obtain the inherent deformation. In this report, a simple and efficient method to estimate inherent deformation of typical weld joints is proposed. Further, using the estimated inherent deformation, the welding deformation of joint specimens and large plate structures are predicted.

Predicting welding deformation in thin plate panel structure by means of inherent strain and interface element

Abstract In this study, welding distortion in a large thin plate panel structure was predicted by means of elastic finite element method based on inherent strain theory and interface element formulation. The welding distortions in the thin plate model computed by large deformation theory and small deformation theory were compared. The comparison suggests that the geometrical non-linearity should be carefully considered when welding distortion in a thin plate structure is predicted. In addition, the influences of welding procedure and assembly sequence on the final distortion were examined numerically. Simulation results indicate that both welding procedure and assembly sequence significantly affect the final deformation.

Estimating inherent deformation in thin-plate Al-alloy joint by means of inverse analysis with the help of cutting technique

A new method was developed to estimate inherent deformations in thin-plate Al-alloy joint.The proposed method is an effective tool to estimate inherent deformations for thin-plate joints with buckling distortion.The characteristics of inherent deformations in Al-alloy thin-plate joint were clarified by T-E-P FEM. The elastic finite element method based on inherent strain theory has been recognized as an effective tool to estimate the total welding deformation for large and complex welded structures. When this computational approach is employed to predict welding deformation in a weldment, one prerequisite is that the inherent deformations of each welded joint included in the welded structure should be known beforehand. The inverse analysis method based on the combination of measuring technology and finite element method can be used to obtain the inherent deformations for various welded joints. However, if buckling distortion occurs in a welded joint, it will be difficult for this method to accurately obtain the inherent deformations especially in thin-plate joints. To overcome this difficulty, an improved inverse analysis method with the help of cutting technique was developed in the current study. The effectiveness of the proposed method was demonstrated through obtaining the inherent deformations in an Al-alloy thin-plate joint with buckling distortion.

Influences of heat input, welding sequence and external restraint on twisting distortion in an asymmetrical curved stiffened panel

Abstract Welding distortion not only degrades the fabrication accuracy of ship hull blocks but also decreases the productivity due to correction works. The accurate prediction of welding-induced distortion will help control the dimension accuracy. In this study, a computational approach based on inherent strain theory and interface element method was employed to efficiently and precisely estimate welding-induced deformation for large welded structures generated during assembly process. In the proposed approach, the local shrinkage due to heat input were considered by inherent strain components. On the other hand, the gap as well misalignment between the two parts to be joined, and the change of stiffness during assembly process were taken into account by interface elements. Meanwhile, the geometrical nonlinearity was included in the developed computational approach. In the current study, the features of welding deformation in an asymmetrical curved stiffened panel were numerically investigated by mean of the new computational approach. In addition, the influences of heat input, welding sequence and external restraint on the twisting distortion of the curved stiffened panel were further studied.

Finite Element Analyses of Residual Stresses in Typical Welded Joints Used in Nuclear Power Plants and Comparisons With Experiments

Recent discoveries of stress corrosion cracking (SCC) at nickel-based metals in pressurized water reactors (PWRs) and boiling water reactors (BWRs) have raised concerns about safety and integrity of plant components. It has been recognized that welding residual stress is an important factor causing the issue of SCC in a weldment. In this study, both numerical simulation technology and experimental method were employed to investigate the characteristics of welding residual stress distribution in several typical welded joints, which are used in nuclear power plants. These joints include a thick plate butt-welded Alloy 600 joint, a dissimilar metal J-groove set-in joint and a dissimilar metal girth-butt joint. First of all, numerical simulation technology was used to predict welding residual stresses in these three joints, and the influence of heat source model on welding residual stress was examined. Meanwhile, the influence of other thermal processes such as cladding, buttering and heat treatment on the final residual stresses in the dissimilar metal girth-butt joint was also clarified. Secondly, we also measured the residual stresses in three corresponding mock-ups. Finally, the comparisons of the simulation results and the measured data have shed light on how to effectively simulate welding residual stress in these typical joints.Copyright