Numerical Methods for Welding Simulation: The Next Technical Step

2008 ◽  
Author(s):  
N. A. Leggatt ◽  
R. J. Dennis ◽  
M. C. Smith ◽  
P. J. Bouchard
Keyword(s):  
Residual Stress ◽  
Numerical Methods ◽  
Heat Source ◽  
Measurement Techniques ◽  
Welding Process ◽  
Moving Heat Source ◽  
Computing Performance ◽  
Solution Accuracy ◽  
Welding Processes ◽  
Insight Into

Numerical methods have been established to simulate welding processes, often based around the use of methods which represent the welding process in a simplified manner. Simplified methods include simultaneous deposition of weld beads and bead lumping where stringers or individual weld beads are grouped together and deposited. These approaches are widely accepted, however the requirement for simplified methods often results in compromises to the solution accuracy usually driven by limitations in data and the capability of computing hardware. In many cases this compromise in accuracy is acceptable providing it is well understood, however there are frequently cases where such simplifications are unacceptable and improved representation of the welding process is required. In practice this generally implies the requirement for a full moving heat source simulation. The transition from simplified simulation methods to the next technical step, full moving heat source simulations, is now possible for a wide variety of scenarios as will be demonstrated in this paper. This paper presents two specific cases, a 3 pass slot weld and a multipass repair weld, where full moving heat source simulations have been considered necessary. For each of these cases the reasons why moving heat source methods are necessary and the benefits that this more demanding simulation technique offers are described. Furthermore the predicted residual stress results are compared with residual stress measurements using a variety of measurement techniques. The work provides an extremely useful insight into how moving heat source methods are now considered a practical analysis method for a wide variety of real world problems. Of further consideration is the fact that in the 2 years since the work reported in this paper was undertaken computing performance would have at least doubled.

Numerical simulation of welding-induced residual stress in fusion welding process using adaptive volumetric heat source

2014 ◽  
Vol 228 (16) ◽  
pp. 2960-2972 ◽  
Author(s):  
S Singh ◽  
N Yadaiah ◽  
S Bag ◽  
S Pal
Keyword(s):  
Residual Stress ◽  
Numerical Model ◽  
Heat Source ◽  
Measurement Errors ◽  
High Performance ◽  
Welding Process ◽  
Fusion Welding ◽  
Volumetric Heat Source ◽  
Welding Processes

The mechanical properties of a weldment structure are influenced by the level of residual stress generated during fusion welding process. The experimental determination of residual stress is cumbersome and not free from measurement errors. A sophisticated numerical model is relatively easy approach to predict residual stress due to the advancement of high performance computational technology. However, the integration of all process physics to make a sophisticated numerical model is ever demanding. The present work is motivated in that direction and involves a finite element based numerical model for simulation of welding-induced residual stresses. A thermal model using adaptive volumetric heat source has been used to estimate temperature distribution. Subsequently, the thermal history is used to perform stress analysis for butt welded plates using three different fusion welding processes. The material behaviour is assumed as elasto-plastic in nature. The calculated results and their trend have been validated with experimental results available in open literature.

Numerical Methods to Predict Distortion in Welded Components

2008 ◽  
Author(s):  
N. A. Leggatt ◽  
R. J. Dennis ◽  
P. J. Bouchard ◽  
M. C. Smith
Keyword(s):  
Residual Stress ◽  
Numerical Methods ◽  
Structural Integrity ◽  
Large Strain ◽  
Stress Fields ◽  
Specimen Thickness ◽  
Single Bead ◽  
Stress Profiles ◽  
Welding Processes ◽  
Integrity Assessments

Numerical methods have been established to simulate welding processes. Of particular interest is the ability to predict residual stress fields. These fields are often used in support of structural integrity assessments where they have the potential, when accurately characterised, to offer significantly less conservative predictions of residual profiles compared to those found in assessment codes such as API 579, BS7910 and R6. However, accurate predictions of residual stress profiles that compare favourably with measurements do not necessarily suggest an accurate prediction of component distortions. This paper presents a series of results that compare predicted distortions for a variety of specimen mock-ups with measurements. A range of specimen thicknesses will be studied including, a 4mm thick DH-36 ferritic plate containing a single bead, a 4mm thick DH-36 ferritic plate containing fillet welds, a 25mm thick 316L austenitic plate containing a groove weld and a 35mm thick esshete 1250 austenitic disc containing a concentric ring weld. For each component, distortion measurements have been compared with the predicted distortions with a number of key features being investigated. These include the influence of ‘small’ vs ‘large’ strain deformation theory, the ability to predict distortions using simplified analysis methods such as simultaneous bead deposition and the influence of specimen thickness on the requirement for particular analysis features. The work provides an extremely useful insight into how existing numerical methods used to predict residual stress fields can be utilised to predict the distortions that occur as a result of the welding fabrication process.

Phenomenological Modeling of Fusion Welding Processes

MRS Bulletin ◽  
1994 ◽  
Vol 19 (1) ◽  
pp. 29-35 ◽  
Author(s):  
S.A. David ◽  
T. DebRoy ◽  
J.M. Vitek
Keyword(s):  
Solid State ◽  
Heat Source ◽  
Base Metal ◽  
Weld Pool ◽  
Welding Process ◽  
Poor Performance ◽  
Consumer Products ◽  
Phase Changes ◽  
Fusion Welding ◽  
Welding Processes

Welding is utilized in 50% of the industrial, commercial, and consumer products that make up the U.S. gross national product. In the construction of buildings, bridges, ships, and submarines, and in the aerospace, automotive, and electronic industries, welding is an essential activity. In the last few decades, welding has evolved from an empirical art to a more scientifically based activity requiring synthesis of knowledge from various disciplines. Defects in welds, or poor performance of welds, can lead to catastrophic failures with costly consequences, including loss of property and life.Figure 1 is a schematic diagram of the welding process showing the interaction between the heat source and the base metal. During the interaction of the heat source with the material, several critical events occur: melting, vaporization, solidification, and solid-state transformations. The weldment is divided into three distinct regions: the fusion zone (FZ), which undergoes melting and solidification; the heat-affected zone (HAZ) adjacent to the FZ, that may experience solid-state phase changes but no melting; and the unaffected base metal (BM).Creating the extensive experimental data base required to adequately characterize the highly complex fusion welding process is expensive and time consuming, if not impractical. One recourse is to simulate welding processes either mathematically or physically in order to develop a phenomenological understanding of the process. In mathematical modeling, a set of algebraic or differential equations are solved to obtain detailed insight of the process. In physical modeling, understanding of a component of the welding process is achieved through experiments designed to avoid complexities that are unrelated to the component investigated.In recent years, process modeling has grown to be a powerful tool for understanding the welding process. Using computational modeling, significant progress has been made in evaluating how the physical processes in the weld pool influence the development of the weld pool and the macrostructures and microstructures of the weld.

Numerical Investigation on Interruption in the Welding Process Used in Shipbuilding

2015 ◽  
Vol 31 (04) ◽  
pp. 220-229
Author(s):  
Debabrata Podder ◽  
Sara Kenno ◽  
Sreekanta Das ◽  
Nisith Ranjan Mandal
Keyword(s):  
Residual Stress ◽  
Heat Source ◽  
Complex Geometry ◽  
Time Lag ◽  
Welding Process ◽  
Diffraction Method ◽  
Nonlinear Material ◽  
Fe Model ◽  
Temperature Dependent ◽  
Longitudinal Residual Stress

Interruptions in the welding process in shipbuilding are unavoidable because of complex geometry and human fatigue. This article presents an uncoupled three dimensional finite element (FE) modeling technique for bead-on-plate welding and an interruption in the welding process for low carbon and high notch toughness steel plate typically used in shipbuilding. The goal of the FE model was to successfully predict the effect of various time delays in the welding interruption on the residual stress distributions. The FE results are compared with the experimental results for the validation of the model. The experimental work was completed using the neutron diffraction method. The element birth-and-death algorithm was used in ANSYSW to simulate the filler metal deposition. A double ellipsoid heat source was used to simulate the heat source of the weld pool. The FE model considers the temperature dependent nonlinear material properties and uses the temperature-dependent combined coefficient of heat loss. The study found that weld interruptions in the welding process change the residual stress patterns and cause an increase in the maximum longitudinal tensile residual stresses. However, the maximum longitudinal compressive stress reduces as a result of interruptions in the weld process. This study found that a weld interruption duration of approximately 2 minutes is optimum for both fatigue and buckling strength. This study also analyzed the effect of preheat on longitudinal residual stress distribution and concluded that a suitable short time lag without any preheat is equivalent to preheat after a long welding interval.

Round Robin Prediction of Residual Stresses in the Edge-Welded Beam R6 Validation Benchmark Problem

2013 ◽  
Author(s):  
Chris Aird ◽  
Mike Smith ◽  
Priyesh Kapadia ◽  
Kiranmayi Abburi Venkata ◽  
Ondrej Muransky
Keyword(s):  
Heat Source ◽  
Constitutive Models ◽  
Round Robin ◽  
Beam Specimen ◽  
Assessment Procedure ◽  
Moving Heat Source ◽  
Benchmark Problem ◽  
Training Problem ◽  
Defect Assessment ◽  
Solution Accuracy

A simple austenitic steel beam specimen with a single autogenous weld bead laid along its top edge is an ideal training problem for novice weld modellers. This geometry may be analysed using either 3D or 2D FE models and employing either block-dumped or moving heat source techniques, with a variety of material constitutive models. This paper describes a residual stress simulation round robin performed on the validation benchmark problem of this type recently added to the R6 defect assessment procedure. A variety of solution strategies of increasing complexity are applied to the problem and the results compared with accuracy targets specified in the validation benchmark. It is found that the greatest solution accuracy is obtained using a 3D moving heat source, and mixed isotropic-kinematic material hardening behaviour.

Fast Simulation for Multi-Pass Welding Process Using Iterative Substructure Method: Investigation of Optimization and Efficient Computation

2014 ◽  
Author(s):  
Akira Maekawa ◽  
Atsushi Kawahara ◽  
Hisashi Serizawa ◽  
Hidekazu Murakawa
Keyword(s):  
Residual Stress ◽  
Power Plants ◽  
Welding Process ◽  
Computation Time ◽  
Efficient Computation ◽  
Element Analysis ◽  
Substructure Method ◽  
Elastic Plastic ◽  
Plastic Analysis ◽  
Welding Processes

Residual stress caused by welding processes affects characteristics of strength and fracture of equipment and piping in power plants. Numerical thermal elastic-plastic analysis is a powerful tool to evaluate weld residual stress in actual plants. However, the conventional three-dimensional precise analysis for a welding process such as multi-pass welding, machining and thermal treatment requires enormous computation time though it can provide accurate results. In this paper, the finite element analysis code based on the iterative substructure method that was developed to carry out thermal elastic-plastic analysis efficiently, with both high computational speed and accuracy, was proposed to simulate the welding process of plant equipment and piping. Furthermore, optimization of the proposed analysis code was examined and the computational efficiency and accuracy were also evaluated.

Effect of Weld on Axial Buckling of Cylindrical Shells

2010 ◽  
Vol 139-141 ◽  
pp. 171-175 ◽  
Author(s):  
Zhou Fang ◽  
Zhi Ping Chen ◽  
Chu Lin Lu ◽  
Ming Zeng
Keyword(s):  
Residual Stress ◽  
Critical Stress ◽  
Cylindrical Shells ◽  
Welding Process ◽  
Circumferential Welds ◽  
Axial Buckling ◽  
Oil Storage ◽  
Stress And Deformation ◽  
Welding Processes ◽  
Residual Stress And Deformation

Large oil storage tank (oil tank for short) shells are vulnerable to buckling damage when suffering the seismic loads. Numerical simulation analysis was taken to estimate the effects of the weld form, number and their location to axial buckling stress of cylindrical shells, considering not only the characteristic of welding processes, but also the effects probably caused by magnitude of residual stress and deformation on elephant foot buckling to oil tanks. It is revealed that the existence of circumferential welds had obvious negative effect on axial buckling critical stress compared with the structure without welds, while the effects of weld number and location were not as much; longitudinal welds had no visible effect on axial buckling critical stress; controlling the residual stress and deformation range caused by circumferential welds should be the key point during the tanks welding process.

scholarly journals Development of Finite Element Solver for Welding Analysis

2018 ◽  
Vol 2 (2) ◽  
Author(s):  
Abid Ali Khan ◽  
Farzeen Shahid ◽  
Ihtzaz Qamar
Keyword(s):  
Finite Element ◽  
Temperature Field ◽  
Heat Conduction ◽  
Heat Source ◽  
Welding Process ◽  
Transient Heat Conduction ◽  
Moving Heat Source ◽  
Structural Members ◽  
Final Solution ◽  
Governing Equations

Welding is a process of joining the similar or different metals. Improper welding process leads to inaccuracies and misalignments of structural members, causing high cost and delays in work. Therefore, it is essential to predict the temperature field during welding process. Different techniques can be used to predict the temperature field, which may lead to structure distortion. The present study aims to develop a finite element solver for transient heat conduction analysis. The final solution is calculated from the assumed solution and compared with the numerical computations. The solver is then modified for use of moving heat source. The modification comprise, change in governing equations with the inclusion of phase change. The moving heat source continuously increases the temperature during motion. When the heat source completes a pass, model is allowed to cool down in order to study the temperature distribution during cooling.

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