scholarly journals Numerical simulation of laser welded joints: modern fatigue analysis methodology

2020 ◽  
Vol 53 (4) ◽  
pp. 342-355
Author(s):  
Rami Markus Kokko ◽  
Joona Vaara ◽  
Teemu Kuivaniemi ◽  
Tero Frondelius
Keyword(s):  
Numerical Simulation ◽  
Cyclic Loading ◽  
Residual Stresses ◽  
Welded Joints ◽  
Fatigue Cracks ◽  
Fatigue Behaviour ◽  
Noticeable Effect ◽  
Microstructural Changes ◽  
Analysis Methodology ◽  
Simulation Results

Welding always induces discontinuities and imperfections in the structure that allows for potential fatigue cracks. Welding effects thermal strains, which yield to residual stresses of the structure that have a noticeable effect on the fatigue behaviour of the structure. Welding inexorably leads to microstructure and geometry changes in the welding region. Material internal changes, residual stresses and microstructural changes can be simulated numerically, and the simulation results can be used in cyclic loading analysis in FEA.

Residual Stress Shakedown in Typical Weld Joints and Its Effect on Fatigue of FPSOs

2007 ◽  
Author(s):  
Liangbi Li ◽  
Torgeir Moan ◽  
Bin Zhang
Keyword(s):  
Residual Stress ◽  
Cyclic Loading ◽  
Residual Stresses ◽  
Welded Joints ◽  
Hot Spot ◽  
Fatigue Behaviour ◽  
Combined Effect ◽  
Element Analysis ◽  
Variable Amplitude ◽  
Initial Residual Stress

Structural members of FPSO hulls often undergo fairly large static loading before they enter service or variable amplitude cyclic loading when they are in service. The combined effect of both applied stress and high initial residual stress is expected to cause shakedown of the residual stresses. Only a few papers seem to deal with appropriate procedures for fatigue analysis by considering the combined effect of variable amplitude cyclic loading with shakedown of residual stresses. Hence, the fatigue behaviour of welded joints in some experiments could not be explained reasonably well. In this paper, some typical welded connections in ship-shaped structures are investigated with 3-D elastic-plastic finite element analysis. The effect of residual stress relaxation, initial residual stress and the applied load after variable amplitude cyclic loading is revealed, and a formula for predicting the residual stress at hot spot quantitatively is proposed. Based on the formula, an improved fatigue procedure is introduced. The proposed fatigue procedure was validated against the experimental results. Therefore, the modified fatigue procedure could be applied to welded joints under arbitrary cyclic loading while accounting for shakedown of residual stresses.

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

2010 ◽  
Author(s):  
Dean Deng ◽  
Kazuo Ogawa ◽  
Nobuyoshi Yanagida ◽  
Koichi Saito
Keyword(s):  
Numerical Simulation ◽  
Residual Stress ◽  
Residual Stresses ◽  
Welded Joints ◽  
Nuclear Power ◽  
Power Plants ◽  
Butt Joint ◽  
Welding Residual Stress ◽  
Dissimilar Metal ◽  
Water Reactors

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.

Influence of Forming Residual Stresses on the Welding Distortions of Two Thick Plates

2009 ◽  
Vol 83-86 ◽  
pp. 125-132 ◽  
Author(s):  
Sebastien Gallée ◽  
Antoine Martin ◽  
Vincent Robin ◽  
Daniel Nelias
Keyword(s):  
Numerical Simulation ◽  
Electron Beam ◽  
Heat Source ◽  
Residual Stresses ◽  
Electron Beam Welding ◽  
Initial Conditions ◽  
Rolling Process ◽  
Vacuum Vessel ◽  
Thick Plates ◽  
Simulation Results

The manufacturing of the ITER (International Thermonuclear Experimental Reactor) vacuum vessel involves the welding of thick deformed plates. The aim of this study is to investigate the influence of forming residual stresses on the welding distortions of two thick plates. The plates are deformed using a three point rolling process. A first numerical simulation is performed to investigate the residual stresses induced by this process. The forming residual stresses are taken into account as initial conditions to perform the electron beam welding simulation of a deformed plate. This simulation first requires calibrating the heat source. Two welding simulations are then performed: the first one with residual stresses and the second one without. The comparison of the simulation results points out a low effect of the residual stresses on the electron beam welding distortions. As a result, in the next electron beam welding simulations of the vacuum vessel, no forming residual stresses will be taken into account.

Growth rate of fatigue cracks in fields of residual stresses in titanium welded joints with different content of embrittling impurities

1990 ◽  
Vol 22 (11) ◽  
pp. 1562-1569 ◽  
Author(s):  
V. T. Troshchenko ◽  
V. V. Pokrovskii ◽  
V. L. Yarusevich ◽  
V. I. Mikhailov ◽  
V. A. Sher
Keyword(s):  
Growth Rate ◽  
Residual Stresses ◽  
Welded Joints ◽  
Fatigue Cracks ◽  
Different Content

Residual Stress and Strain Responses of Welded Piping Joints Under Low-Cycle Fatigue Loading

2009 ◽  
Author(s):  
Pei-Yuan Cheng ◽  
Tasnim Hassan
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Residual Stresses ◽  
Fatigue Failure ◽  
Welded Joints ◽  
Low Cycle Fatigue ◽  
Fatigue Cracks ◽  
Stress And Strain ◽  
Weld Toe ◽  
Strain Responses

It is well known that residual stress of welded joints influence their fatigue lives. This influence of residual stress is manifested through strain ratcheting response at the weld toe. Among many other reasons, strain ratcheting at the weld toe is anticipated to be a reason of many premature fatigue failure of welded joints. Hence, accurate simulations of weld toe residual stress and strain responses are essential for fatigue life simulation of welded joints. This paper presents results form an ongoing study on fatigue failure of welded piping joints. A modeling scheme for simulating weld toe residual stress and strain response is developed. Uncoupled, thermo-mechanical, finite element analyses are employed for imitating the welding procedure, and thereby simulating the temperature history during welding and initial residual stresses. Simulated residual stresses are validated by comparing against the measured residual stresses. Finite element simulations indicate that both residual stress and resulting strain responses near the weld toe are the key factors in inducing fatigue cracks at the weld toe. Research needs in revealing the fatigue failure mechanisms at the weld toe are discussed.

Characteristics of Fatigue Cracks Propagating in Different Directions of FSW Joints Made of 5754-H22 and 6082-T6 Alloys

2014 ◽  
Vol 794-796 ◽  
pp. 371-376 ◽  
Author(s):  
Ákos Meilinger ◽  
János Lukács
Keyword(s):  
Fatigue Crack ◽  
Cyclic Loading ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Welded Joints ◽  
Fatigue Cracks ◽  
Research Work ◽  
Friction Stir ◽  
Base Materials ◽  
Welding Processes

The Friction Stir Welding (FSW) is a dynamically developing version of the pressure welding processes. High-quality welded joints can be created using this process for different engineering applications (e. g. automotive parts). Nowadays, the knowing of the properties and the behaviour of the welded joints is an important direction of the investigations, especially under cyclic loading. The research work aimed to demonstrate the behaviour of the friction stir welded joints under cyclic loading conditions. Fatigue Crack Propagation (FCG) experiments were performed on 5754-H22 and 6082-T6 aluminium alloys and their friction stir welded joints. The CT type specimens were cut parallel and perpendicular to the characteristic directions of the base materials and the welded joints, and the notch locations in the specimens of welded joints were different, too. Therefore, the propagating cracks represent the possible directions of the fatigue cracks both on the base materials and on the welded joints. The results of the fatigue crack propagation tests on the welded joints clearly demonstrate the different characteristics of the thermo-mechanically affected zone (TMAZ), the heat affected zone (HAZ), and the advancing (AS) and retreating sides (RS) of the weld nugget (WN). The investigations and their results were compared with each other and with the results can be found in the literature.

scholarly journals Fatigue Behaviour of 7N01-T4 Aluminium Alloy Welded by Ultrasonic-Assisted Friction Stir Welding

Materials ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 4582 ◽  
Author(s):  
Zhiqiang Zhang ◽  
Changshu He ◽  
Ying Li ◽  
Jingxun Wei ◽  
Menggang Zhai ◽  
...  
Keyword(s):  
Friction Stir Welding ◽  
Residual Stresses ◽  
Ultrasonic Vibration ◽  
Fatigue Cracks ◽  
High Stress ◽  
Fatigue Behaviour ◽  
Second Phase ◽  
Friction Stir ◽  
Stress Levels ◽  
Ultrasonic Assisted

This study investigates the effects of axial ultrasonic vibration on the microstructure evolution, residual stresses distribution and fatigue fracture behaviour of a 7N01-T4 joint, and demonstrates that ultrasonic vibration can significantly promote the flow of plasticised metals, expand the stirred zone (SZ) width and refine the grain size. The longitudinal residual stresses of the joints are dominant, and the peak longitudinal residual stresses of the thermo-mechanically affected zone (TMAZ) on the advancing side (AS) (TMAZ-AS) in the ultrasonic-assisted friction stir welding (UAFSW) joint are 31.5 MPa lower than those in the friction stir welding (FSW) joint. Compared to that of FSW joints, the fatigue strength of UAFSW joints increases by 20 MPa at 107 cycles (stress ratio of R = 0.1). At high-stress levels, crack initiation occurs at the TMAZ-AS, and is mainly attributed to high residual stresses and second-phase particles. At low-stress levels, fatigue cracks are likely to initiate in the transition zone (TZ).

scholarly journals Prediction and numerical simulation of residual stress in multi-pass pipe welds

2021 ◽  
Author(s):  
Mahmood Hasan Al-Hafadhi ◽  
Gyorgy Krallics
Keyword(s):  
Numerical Simulation ◽  
Residual Stress ◽  
Residual Stresses ◽  
Hardness Test ◽  
Element Model ◽  
Good Prediction ◽  
Two Dimensional ◽  
Residual Welding Stress ◽  
Welding Stress ◽  
Simulation Results

AbstractA numerical simulation procedure is presented to predict residual stress states in multi-pass welds in oil transportation pipes. In this paper, a two-dimensional thermo-mechanical finite element model is used to calculate the temperature distribution, hardness, and the distribution of residual stresses during multi-pass welding of pipes of dissimilar metals and varying thicknesses. In this model, the temperature dependence of the thermal and mechanical properties of the material was considered. The present model was validated using the hardness measurement. Good agreement was found between the measurement and the numerical simulation results. The simulated result shows that the two-dimensional model can be effectively used to simulate the hardness test and predict the residual stress in the pipe weld. The simulation results and measurements suggest that the model with moving heat source can obtain a good prediction of residual welding stress. Both the two-dimensional and the three-dimensional modeling can be used to estimate the residual stresses in different weld regions and help saving time.

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