Finite Element Analysis of Residual Stresses in TT-Welded Joint of a Fixed Jacket Platform

2006 ◽  
Author(s):  
Kh. Rostami ◽  
A. R. M. Gharabaghi ◽  
M. R. Chenaghlou ◽  
A. Arablouei
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Thermal Stresses ◽  
Welded Joint ◽  
Welding Process ◽  
Element Analysis ◽  
Welded Steel ◽  
Buckling Strength ◽  
Structural Distortions ◽  
Weld Toe

Welded steel tubular joints are the kind of connections used extensively in the construction of fixed jacket platforms. The welding process creates considerable tensile residual stresses near the toe of TT-joint due to the rapid cooling and contraction of final welding layers. Welding produces thermal stresses that cause structural distortions, which influence the buckling strength of the structure. In this study thermal elasto-plastic analysis is carried out using ANSYS finite element techniques to evaluate the thermo-mechanical behavior and the residual stresses of the TT-joint. Moreover, the technique of element birth and death is employed to simulate the weld filler variation with time in TT-joint. The results show the considerable tensile residual stress near the weld toe that it may cause crack initiation in this region and threats the fatigue life of joint.

Simplified FEA Models in the Analysis of the Redistribution of Beneficial Compressive Stresses in Welds During Cyclic Loading

2018 ◽  
Author(s):  
B. L. Josefson ◽  
J. Alm ◽  
J. M. J. McDill
Keyword(s):  
Cyclic Loading ◽  
Residual Stresses ◽  
Compressive Stress ◽  
Welding Process ◽  
Plastic Behavior ◽  
Element Analysis ◽  
Compressive Stresses ◽  
Static Contact ◽  
Weld Toe ◽  
Compressive Residual Stresses

The fatigue life of welded joints can be improved by modifying the weld toe geometry or by inducing beneficial compressive residual stresses in the weld. However, in the second case, the induced compressive residual stresses may relax when the welded joint is subjected to cyclic loading containing high tensile or compressive stress peaks. The stability of induced compressive stresses is investigated for a longitudinal gusset made of a S355 steel. Two methods are considered; either carrying out a high frequency mechanical impact (HFMI) treatment after welding or alternatively using low transformation temperature (LTT) electrodes during welding. The specimen is then subjected to a cyclic loading case with one cycle with a tensile peak (with magnitude reaching the local yield stress level) followed by cycles with constant amplitude. A sequential finite element analysis (FEA) is performed thereby preserving the history of the elasto-plastic behavior. Both the welding process and the HFMI treatment are simulated using simplified approaches, i.e., the welding process is simulated by applying a simplified thermal cycle while the HFMI treatment is simulated by a quasi-static contact analysis. It is shown that using the simplified approaches to modelling both the welding process and HFMI treatment gives results that correlate qualitatively well with the experimental and FEA data available in the literature. Thus, for comparison purposes, simplified models may be sufficient. Both the use of the HFMI treatment and LTT electrodes give approximately the same compressive stress at the weld toe but the extent of the compressive stress zone is deeper for HFMI case. During cyclic loading it is shown that the beneficial effect of both methods will be substantially reduced if the test specimen is subjected to unexpected peak loads. For the chosen load sequence, with the same maximum local stress at the weld toe, the differences in stress curves of the HFMI-treated specimen and that with LTT electrodes remain. While the LTT electrode gives the lowest (compressive) stress right at the well toe, it is shown that the overall effect of the HFMI treatment is more beneficial.

Estimation of Residual Stresses in Steel Welded Joints Using Three Dimensional Finite Element Analysis

2018 ◽  
Author(s):  
Shivdayal Patel ◽  
B. P. Patel ◽  
Suhail Ahmad
Keyword(s):  
Residual Stress ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Residual Stresses ◽  
Boundary Conditions ◽  
Welding Speed ◽  
Welded Joints ◽  
Plate Thickness ◽  
Welding Process ◽  
Element Analysis

Welding is one of the most used joining methods in the ship industry. However, residual stresses are induced in the welded joints due to the rapid heating and cooling leading to inhomogenously distributed dimensional changes and non-uniform plastic and thermal strains. A number of factors, such as welding speed, boundary conditions, weld geometry, weld thickness, welding current/voltage, number of weld passes, pre-/post-heating etc, influence the residual stress distribution. The main aim of this work is to estimate the residual stresses in welded joints through finite element analysis and to investigate the effects of boundary conditions, welding speed and plate thickness on through the thickness/surface distributions of residual stresses. The welding process is simulated using 3D Finite element model in ABAQUS FE software in two steps: 1. Transient thermal analysis and 2. Quasi-static thermo-elasto-plastic analysis. The normal residual stresses along and across the weld in the weld tow region are found to be significant with nonlinear distribution. The residual stresses increase with the increase in the thickness of the plates being welded. The nature of the normal residual stress along the weld is found to be tensile-compressive-tensile and the nature of normal residual stress across the weld is found to be tensile along the thickness direction.

Strengthening of wide-flange columns under load

1990 ◽  
Vol 17 (5) ◽  
pp. 835-843 ◽  
Author(s):  
H. Marzouk ◽  
S. Mohan
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Critical Load ◽  
Closed Form Solution ◽  
Welding Process ◽  
Form Solution ◽  
Element Analysis ◽  
Welding Stress ◽  
Existing Structures ◽  
Welding Sequence

The present work deals with formulation of theoretical and analytical methods leading to the development of column strength curves. The formulations were developed for both elastic and inelastic behaviour. Two types of reinforcement have been developed for strengthening the W-shape columns under load. Since the column strength curves are based in part on the magnitude and distribution of residual stresses, it is extremely important to consider the new pattern of residual stresses due to welding process. Also, the welding sequence will affect the magnitude and distribution of residual stresses. Theoretical formulations leading to a closed-form solution for the prediction of critical load were developed for two types of strengthening using the superposition of original residual, new welding, and initial loading stresses. A nonlinear finite element analysis based on the large deformation theory of stability was used to predict the strengthened column critical load. It takes into consideration the effect of cooling residual stresses and new welding residual stresses. The formulations were incorporated with gradual penetration of yielding, the spreading of inelastic zones along the member length, the presence of residual stresses, and strain hardening of the material. Experiments were carried out to determine the actual capacity of strengthened columns. Seven specimens were tested using two and four strengthening plates. The welding stresses were measured through a series of experiments, and it was found that the parabolic distribution is a very close approximation to the actual new welding stress distribution. Key words: reinforcement of steel columns, welding stresses, welding sequence, strengthening of existing structures, buckling, steel plating, finite element.

Finite Element Analysis Used to Optimize Welding Patterns for Marine Structure

1998 ◽  
Author(s):  
Dmitry Ischenko ◽  
Raafat Ibrahim
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Welding Process ◽  
Element Analysis ◽  
Gusset Plate ◽  
Transient Problem ◽  
Element Simulation ◽  
Marine Structure ◽  
Solid Plate ◽  
Nonlinear Transient

Abstract The development of optimum welding patterns which can reduce the adverse effects of welding is important for industry, and particularly, for shipbuilding. In this investigation, a finite element simulation was employed in order to optimize the design of the weldment and reduce residual stresses and distortions. A gusset plate, which was used to increase the stiffness of marine structures, was subjected to thermal loads to simulate the effect of the welding process. Temperature distributions were obtained as a solution of the nonlinear transient problem of thermal conductivity. These distributions were then used to calculate residual stresses and distortion by solving thermo-elastic-plastic problems. The results indicated a significant reduction in the distortion when a plate with circular slots and interrupted welding was used instead of a continuously welded solid plate.

Prediction of Welding Residual Stresses, Crack Initiation and Creep Crack Driving Forces C(t) Within a Continuous Finite Element Solution

2010 ◽  
Author(s):  
D. P. Bray ◽  
R. J. Dennis ◽  
M. C. Smith
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Driving Forces ◽  
Welding Process ◽  
Creep Damage ◽  
Operating Conditions ◽  
Finite Element Solution ◽  
Element Solution ◽  
Element Analysis ◽  
Creep Crack

The work reported in this paper investigates the manufacture, through-life operation and cracked behaviour of an attachment weld in a UK AGR boiler. A structural assessment of the attachment weld was performed to demonstrate its integrity. This assessment made use of complex finite element analysis of both the welding process and postulated defects. A simulation of the welding process was performed in order to predict the residual stresses and hardened material state throughout the attachment weld. The welding simulation was performed in two stages since a butter weld was deposited prior to the attachment weld itself. The accumulation of creep damage was predicted during steady normal operating conditions for the lifetime of the component. A contour map of creep damage was used to postulate the location and size of hypothetical single and double edge surface cracks within the weld. These postulated cracks were then explicitly introduced into the finite element model. The crack tip stress parameter C(t) was evaluated in order to predict the creep crack driving forces. The results from a cracked body simulation suggested that the creep crack driving force C(t) reduces as the crack grows, due to relief of the dominant welding residual stresses. The residual stress, creep damage and cracked body simulations have been brought together into a novel continuous finite element solution. The results can be used to support a safety case for continued operation of existing plant.

Numerical Study of Welding with Trailing Heat Sink Considering Phase Transformation Effects

2014 ◽  
Vol 875-877 ◽  
pp. 2118-2122
Author(s):  
Shirish R. Kala ◽  
N. Siva Prasad ◽  
G. Phanikumar
Keyword(s):  
Finite Element ◽  
Phase Transformation ◽  
Residual Stresses ◽  
Material Properties ◽  
Heat Sink ◽  
Numerical Study ◽  
Gaussian Model ◽  
Welding Process ◽  
Source Model ◽  
Element Analysis

Welding process with trailing heat sink for 2 mm mild steel plates has been analyzed to estimate distortion and residual stresses using a finite element modeling software Sysweld. The material properties used for the analysis are both temperature dependent and phase dependent. A transient thermal analysis is carried out using Goldak double ellipsoidal heat source model and heat sink as Gaussian model with negative heat flux. The finite element analysis (FEA) is conducted by considering the material properties of all phases of steel as well as without phase transformation i.e. by considering properties of only ferrite phase. Temperature distribution, distortion and residual stresses are calculated and compared for four cases: without phase without cooling, without phase with cooling, with phase without cooling and with phase with cooling. It is found that FEA without phase transformation effects overestimates the residual stresses in the fusion zone (FZ) and heat affected zone (HAZ). It is also found that a trailing heat sink reduces transverse compressive residual stresses thus minimizing the possibilities of buckling.

Development of Predicted Stress and Strain during Conventional and after Mitigation of Welded Aluminium-Manganese Alloy

2013 ◽  
Vol 762 ◽  
pp. 596-601
Author(s):  
F. Soul ◽  
M. Ateeg
Keyword(s):  
Heat Transfer ◽  
Residual Stress ◽  
Finite Element ◽  
Residual Stresses ◽  
Thermal Stresses ◽  
Stress And Strain ◽  
Manganese Alloy ◽  
Element Analysis ◽  
Longitudinal Residual Stress ◽  
Mitigation Technique

The trend in automotive, aircraft, and marine industries is the increasing use of sheet materials to reduce weight in components and optimize materials performance. Welding is the main fabrication and assembly process in many of these industrial applications. However, in using thin-shell structures in such applications, welding may results in significant residual stresses and out-of-plane distortion. Transient thermal stresses, residual stresses, and distortion sometimes cause cracking and mismatching of joints. High tensile residual stresses are undesirable since they can contribute to fatigue failure. The analysis and measurement of temperature and stresses in component are often too complex to conduct in practise, and thus finite element models provide feasible approach to examine these matters. In this paper, finite element analysis has been performed using the ANSYS package to study the behaviour of longitudinal residual stress and strain in a welded thin aluminium-manganese alloy. The model presented simulates conventional welding and welding with the introduction of welding mitigation technique for enhancement of heat transfer, in which a trailing heat sink was applied. The thermal profiles obtained using the mitigation technique is completely different from those obtained in the conventional cooling. The localized transient residual stress and through-thickness strain after applying a cooling sink are discussed. The transient residual stress behaviour was highly affected by the modified temperature distribution and magnitude due to introducing the heat transfer enhancement.

scholarly journals Thermo-mechanic and Microstructural Analysis of an Underwater Welding Joint

2016 ◽  
Vol 21 (2) ◽  
pp. 156-164 ◽  
Author(s):  
Pedro Hernández Gutiérrez ◽  
Francisco Cepeda Rodríguez ◽  
Jose Jorge Ruiz Mondragón ◽  
Jorge Leobardo Acevedo Dávila ◽  
Martha Patricia Guerrero Mata ◽  
...  
Keyword(s):  
Thermal Analysis ◽  
Finite Element ◽  
Residual Stresses ◽  
Microstructural Analysis ◽  
Welding Process ◽  
Temperature History ◽  
Welding Parameters ◽  
Pipe Material ◽  
Element Analysis ◽  
Underwater Welding

Abstract The aim of this research is to present a comparative analysis between theoretical and experimental thermal fields as well as a microstructural behaviour and residual stresses applying multiple weld beads in the joint of two API 5L X52 pipe sections. The thermal field, microstructural and residual stresses were numerically modelled through the finite element method (FEM) and compared to experimentally. The simulation conditions used in the FEM analysis were similar considerations to the underwater welding conditions. The finite element analysis was carried out, first by a non-linear transient thermal analysis for obtaining the global temperature history generated during the underwater welding process. Subsequently, a microstructural behaviour was determined using the temperatures distribution obtained in the pipe material by calculating the structural transformations of the material during the welding process, and finally a stress analysis was developed using the temperatures obtained from the thermal analysis. It was found that this simulation method can be used efficiently to determinate with accuracy the optimum welding parameters of this kind of weld applications.

Effect of Thermal Input on Finite Element Predictions of Welding Residual Stresses

2011 ◽  
Vol 399-401 ◽  
pp. 1976-1983
Author(s):  
Ai Hui Wu ◽  
Stavros Syngellakis ◽  
B. G. Mellor
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Welded Joint ◽  
Welding Process ◽  
Mechanical Analysis ◽  
Two Dimensional ◽  
Distribution Modelling ◽  
Element Simulation ◽  
Key Factor ◽  
Dimensional Finite Element

A two-dimensional finite element simulation of a welding process is developed for predicting temperature histories and residual stresses in a structural steel butt-welded joint. The purpose of the simulation presented in this paper is the assessment of the effect of uncertainties in thermal material, loading and constraint input on both the thermal and mechanical analysis predictions. The model is validated by comparison with previously welded and tested specimen with published residual stresses measurements. Residual stress results are not sensitive to the thermal analysis input even if the latter has significant influence on temperature distribution. Modelling boundary conditions for both thermal and stress analyses, was identified as a key factor affecting predictions of residual stresses and distortion.

scholarly journals Finite element analysis of residual stress generation during spot welding and its affect on fatigue behavior of spot welded joints

2005 ◽  
Author(s):  
◽  
Xin Long
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Spot Welding ◽  
Welded Joint ◽  
Fatigue Behavior ◽  
Welding Process ◽  
Stress Generation ◽  
Fracture Mechanisms ◽  
Element Analysis ◽  
Spot Welded

This dissertation presents the finite element based prediction of residual stress generation in a spot welded joint during the spot welding process and the effects of residual stress on fatigue behavior of a spot welded joint. Spot welded advanced high strength steels, namely dual phase DP600 GI and transformation induced plasticity TRIP600 steels were investigated for their fatigue life, microstructure changes and fatigue fracture mechanisms to develop design data for possible application in future light weight and more fuel efficiency automobiles.

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