Modified Equivalent Load Method for Welding Distortion Analysis

In this study, modified equivalent load method for welding distortion analysis is suggested to improve its accuracy. To avoid the excessive computational time for welding distortion analysis of large welded structures, shell element-based elastic analysis methods are widely used, applying the inherent deformation approach. Equivalent nodal forces are commonly used in common FE (Finite Element) codes to enter these inherent deformation values. However, the conventional method cannot estimate precise longitudinal bending following the conventional equation. In this study, the problem of the existing equivalent load method is analyzed by a case study, and the modified equivalent load method that can estimate angular distortion, transverse shrinkage, and longitudinal bending is presented based on the FEM principle. The results show that by applying the proposed method, the shell element-based elastic FE approach for the welding distortion analysis can be achieved with improved accuracy.

Accurate FE Computation for Out-of-plane Welding Distortion Prediction of Fillet Welding with Considering Self-Constraint

Inherent deformation as key parameter plays an essential role in elastic finite element (FE) analysis for welding distortion prediction. In this study, the self-constraints supported by surrounding base material and lateral stiffener were presented, where their influences on magnitudes of inherent deformation components were qualitatively examined. In detail, self-constraint supported by the surrounding base material will distinguish the inherent deformation as an individual physical representation; and self-constraint supported by the lateral stiffener will significantly influence the bending component and final deformed mode. Taking into account fillet welding and orthogonal stiffened welded structure as the application, experiments were conducted for out-of-plane welding distortion measurement. Transient nonlinear thermal elastic-plastic FE analysis of fillet welding was carried out to evaluate inherent deformation after validation with the measured data; then, elastic FE analysis with inherent deformation was carried out to accurately predict the out-of-plane welding distortion and welding buckling behavior in fabrication of an orthogonal stiffened welded structure which is a part of typical ship panel, and there is a good agreement between the predicted and measured welding distortion.

Benchmark Investigation of Welding-Induced Buckling and Its Critical Condition During Thin Plate Butt Welding

Welding-induced buckling is a special type of welding distortion occurring during thin plate butt welding and was investigated using both experimental and computational approaches for this benchmark investigation. In addition, the characteristic parameter and its magnitude for the occurrence of welding-induced buckling were also presented. Fundamental theories of the inherent deformation, finite strains, and eigenvalues of the structure stiffness matrix were considered to investigate welding-induced buckling. A series of experiments on thin plate butt welding with different heat inputs were conducted, and buckling behavior was observed from the deformed shape and the distribution of out-of-plane welding distortion. Transient nonlinear thermal elastic–plastic finite element (TEP FE) and elastic finite element (FE) analyses were conducted to predict welding-induced buckling, and the results were in good agreement with the measurement data. Criteria for the occurrence of welding-induced buckling were proposed and discussed. Inherent deformation was considered as a characteristic parameter of buckling behavior during welding, and its critical magnitude was calculated using a loading incremental method and eigenvalue analysis with good agreement.

Recent Developments in Experimental and Numerical Assessments of Welding-Induced Residual Stresses

The objective of this work is to present and review the recent developments in the experimental and numerical assessment and simulation techniques on the welding induced distortions and residual stresses. The temperature distribution, welding induced distortion and residual stresses in thin walled welded structures, originating from different experimental tests are reviewed and discussed. Different mathematical models and their numerical applications in representing the heat source are analysed and their advantages and drawbacks are discussed. Thermal stress analyses employing the three-dimensional nonlinear thermo-elasto-plastic approaches and finite element simulations with inherent deformation applicable to large-scale and complex welded structures are also revised and discussed. Discussions on the material properties of the base metal, heat affected zone (HAZ) and weld metal, the effect of the welding sequence, and the pattern of residual stress distribution presented are given a special attention.