Numerical Analysis of Residual Stresses in Hyperbaric Welding

2012 ◽  
Author(s):  
Xiaobo Ren ◽  
Odd M. Akselsen ◽  
Sigmund K. Ås ◽  
Bård Nyhus
Keyword(s):  
Residual Stress ◽  
Numerical Analysis ◽  
Residual Stresses ◽  
Pressure Range ◽  
Structural Integrity ◽  
Sea Water ◽  
Welding Residual Stress ◽  
Transformation Plasticity ◽  
Micro Structure ◽  
Welding Procedure

Hyperbaric welding residual stress is one of the main concerns for deep water operation. This study presents the numerical investigation of residual stresses in hyperbaric welding by using WeldsimS code. The pressure range investigated in this study is from 3 to 35 bar, which corresponds to 30 to 350 msw (Meters of Sea Water). Experiments results indicate that the welding procedure might be significantly influenced within the pressure range studied. A 2D axisymmetric model has been considered in this study to simulate circumferential welding of a pipe. Phase transformations and transformation plasticity during the welding procedure have been taken into account. The main aim of the study is to predict the hyperbaric welding residual stresses. The temperature evolution and the micro-structure were also studied. Results show that residual stresses induced by hyperbaric welding are significant within the pressure range investigated, which should be assessed for the sake of structural integrity.

Welding Residual Stress Analysis Using Axisymmetric Modeling for Shroud Support Structure

2008 ◽  
Author(s):  
Kazuo Ogawa ◽  
Yukihiko Okuda ◽  
Toshiyuki Saito ◽  
Takahiro Hayashi ◽  
Rie Sumiya
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Large Scale ◽  
Structural Integrity ◽  
Plastic Material ◽  
Welding Residual Stress ◽  
Stress Distributions ◽  
Surface Residual Stress ◽  
Actual Structure ◽  
Elastic Plastic Material

Recently, several cracks caused by stress corrosion cracking (SCC) have been found on welds of shroud supports in Boiling Water Reactor (BWR) plants. The major cause of SCC in a weld joint is considered due to welding residual stress generated in the fabrication processes of the components. For continuous safety operations, it is necessary to estimate the structural integrity of such shroud supports with cracks based on the distribution of residual stresses induced by welding. In order to know and to validate the numerical method of residual stresses induced by welding of large scale and complex shaped components, a BWR shroud support mock-up with a hemispherical base of reactor pressure vessel (RPV) was fabricated by Japan Nuclear Energy Safety Organization (JNES) as a national project. The mock-up has a 32° section of actual BWR shroud supports with approximately the same configurations, materials and welding conditions of an actual component. During welding in the fabrication process of the mock-up, temperature was measured and after completion of the mock-up fabrication, surface residual stress distributions for each weld were also measured by the sectioning method. In addition, through-thickness residual stress distributions were investigated. Residual stress for each weld was calculated by using axisymmetric models considering temperature dependent elastic-plastic material properties. Though the actual structure of shroud supports is essentially complex, we simplified axisymmetric models in the center of the cross section. The analysis results show a similar profile and good agreement with the measured results on the surface of all the welds and through the welds at the upper and lower joints of the shroud support leg.

Welding Residual Stresses in Tubular Joints

2013 ◽  
Vol 768-769 ◽  
pp. 605-612 ◽  
Author(s):  
Majid Farajian ◽  
Thomas Nitschke-Pagel ◽  
Klaus Dilger
Keyword(s):  
Residual Stress ◽  
Fatigue Crack ◽  
Crack Initiation ◽  
Residual Stresses ◽  
Structural Integrity ◽  
Fatigue Crack Initiation ◽  
Welding Residual Stress ◽  
Structural Safety ◽  
Welding Parameters

In spite of an increased awareness of welding residual stress threat to structural integrity, the extent of its influence on fatigue especially under multiaxial loading is still unclear and is a matter of debate. One important reason for this lack of clarities is that the determination of the initial welding residual stress field in welded structures even at the fatigue crack initiation sites is difficult and requires complementary instruments. Since the fatigue crack initiation in sound welds almost always occurs on the surface, the determination of surface residual stresses could increase the awareness of the extent of their threat to the structural safety. In this paper the development of residual stresses in different TIG-welded tubular specimens out of S355J2H and S690QL steel is studied and compared. The mechanisms of the development of residual stresses based on heat input and cooling rate are discussed. The welding parameters and thus heat inputs are varied and the mechanisms leading to different residual stress states are investigated. X-ray method was used for residual stress state characterization.

Residual Stresses in Strength Mismatched Welded Pipes

2017 ◽  
Author(s):  
Ali Mirzaee-Sisan ◽  
Junkan Wang
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Thermal Stresses ◽  
Structural Integrity ◽  
Welding Residual Stress ◽  
Temperature Fields ◽  
Transient Temperature ◽  
Element Analysis ◽  
Girth Welds ◽  
Welded Pipe

It is commonly understood that residual stresses can have significant effects on structural integrity. The extent of such influence varies and is affected by material properties, manufacturing methods and thermal history. Welded components such as pipelines are subject to complex transient temperature fields and associated thermal stresses near the welded regions. These thermal stresses are often high in magnitude and could cause localized yielding around the deposited weld metal. Because of differential thermal expansion/contraction episodes, misfits are introduced into the welded regions which in turn generate residual stresses when the structure has cooled to ambient temperature. This paper is based on a recently completed Joint Industry Project (JIP) led by DNV GL. It briefly reviews published experimental and numerical studies on residual stresses and strength-mismatched girth welds in pipelines. Several Finite Element Analysis (FEA) models of a reeling simulation have been developed including mapping an initial axial residual stress (transverse to the weld) profile onto a seamless girth-welded pipe. The initial welding residual stress distribution used for mapping was measured along the circumference of the girth welds. The predicted residual stresses after reeling simulation was subsequently compared with experimental measurements.

A Study of the Effect of Hardening Model in the Prediction of Welding Residual Stress

2012 ◽  
Author(s):  
Martina M. Joosten ◽  
Martin S. Gallegillo
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Structural Integrity ◽  
Kinematic Hardening ◽  
Welding Process ◽  
Cyclic Hardening ◽  
Welding Residual Stress ◽  
Isotropic Hardening ◽  
Hardening Models ◽  
Set Up

The presence of residual stresses can significantly affect the performance of manufactured products. The welding process is one of the most common causes of large tensile residual stresses, which may contribute to failure by brittle fracture or cause other forms of failure such as damage by corrosion and creep. Welding is a widely used method of fabrication and it can generate high levels of residual stress over significant proportions of the thickness of a component. In order to study the effect of material characterisation on computer based predictions of welding residual stresses, the presented work was carried out as part of the European Network on Neutron Techniques Standardisation for Structural Integrity (NeT). Within the NeT, a task group is investigating a three-pass Tungsten Inert Gas (TIG) weld benchmark. The three-pass specimen offers the possibility of examining the cyclic hardening and annealing behaviour of the weld metal and heat affected zone. A 3D model of the benchmark NeT problem was set up using ABAQUS v6.9.1 and validated against measurements. This paper presents the finite element work. Future papers from the NeT shall present experimental measurements. Different hardening models were considered in order to study their effect on the residual stresses. The different hardening models were isotropic hardening, linear and nonlinear kinematic hardening and combinations of these. Also the effect of annealing on the hardening behaviour is studied. Finally, the results of the simulations are compared to residual stress distributions as given in several standards.

scholarly journals Numerical Investigation of Welding Residual Stress Field and its Behaviour under Multiaxial Loading in Tubular Joints

2014 ◽  
Vol 996 ◽  
pp. 788-793
Author(s):  
Kimiya Hemmesi ◽  
Majid Farajian ◽  
Dieter Siegele
Keyword(s):  
Residual Stress ◽  
Yield Strength ◽  
Residual Stresses ◽  
Structural Integrity ◽  
Weld Zone ◽  
Welding Residual Stress ◽  
Multiaxial Loading ◽  
Residual Stress Field ◽  
Tubular Joints ◽  
Welded Structure

The lack of clarities in estimating the residual stress threat to the structural integrity has led to conservative assumptions in the current design of welds. The complexities become more in the case of multiaxial loading of welded structure, considering fracture or fatigue. To what extent the residual stresses influence the performance of a welded structure, depends on how stable they are under service loads. Finite element analyses are used here to describe the development of welding residual stresses in tubular joints and their relaxation under multiaxial loading. It is observed that the effect of the torsion load is more significant than the effect of tension load in releasing of the residual stresses. For pure tensile loading, the relaxation of the residual stresses are negligible as long as the applied load is lower than 50% of the yield strength of the material. For a combined tension-torsion loading of 75% of the yield strength, the residual stresses are almost completely released, and in the weld zone they become compressive.

Advanced Indentation Techniques: NDE for Flow Properties and Residual Stresses of Pipelines

2002 ◽  
Author(s):  
Yeol Choi ◽  
Dongil Son ◽  
Jae-Il Jang ◽  
Joon Park ◽  
Woo-Sik Kim ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Residual Stress ◽  
Residual Stresses ◽  
Structural Integrity ◽  
Potential Method ◽  
Indentation Load ◽  
Welding Residual Stress ◽  
Destructive Testing ◽  
Integrity Assessment ◽  
Indentation Technique

Structural integrity assessment is indispensable for preventing catastrophic failure of industrial structures/components/facilities that are faced with time-dependent and environmentally-accelerated degradation. This diagnosis of operating components should be done periodically for safe maintenance and economical repair. However, conventional standard methods for mechanical properties have the problems of bulky specimen, destructive and complex procedure of specimen sampling. So, an advanced indentation technique has been developed as a potential method for non-destructive testing of in-field structures. This technique measures indentation load-depth curve during indentation and analyzes the mechanical properties related to deformation such as yield strength, tensile strength and work-hardening index. Also the advanced indentation technique can evaluate residual stresses based on the concept that indentation load-depth curves were shifted with the direction and the magnitude of residual stress applied to materials. In this study, we characterized the tensile properties and welding residual stress of various Industrial pipeline steels through the new techniques, and the results are introduced and discussed.

Review of Welding Residual Stress Stiffening Effect on Vibrational Characteristics of Structures Using Damage Approach and Vibratory Stress Relief Implementation

2017 ◽  
Author(s):  
AmirHossein MajidiRad ◽  
Yimesker Yihun
Keyword(s):  
Residual Stress ◽  
Modal Analysis ◽  
Structural Integrity ◽  
Material Selection ◽  
Welding Process ◽  
Stress Relief ◽  
Welding Residual Stress ◽  
Welded Structure ◽  
Welding Procedure

There is a huge amount of research and study on the quality, parameter manipulation, material selection etc. of welding to develop optimized results for specific applications. To have a profound understanding of the process, and to investigate and verify various parameters which affect the quality of the welding process, experts use analytical, numerical and experimental methods. The major concern regarding the welding procedure is welding defect, which can affect the integrity of the welded structure. Various nondestructive structural health monitoring methods and modal analysis techniques have been employed to study and improve the strength and quality of the welded structure. Modal analysis is one of the most accurate and commercial techniques to track down the damage within the structures. It uses natural frequency, damping factors and modal shapes to observe the structural and material defects in details. There have been noticeable developments in this area and lots of studies have been conducted applying this technique to put welding procedure under rigorous scrutiny to improve its efficiency. While modal analysis is a tool to identify structural integrity of the components, vibration can affect the nature of the metal and change the mechanical properties in some cases. Mechanical vibration and Ultrasonic as low and high frequency oscillations respectively, are able to change the microstructure of the structures so that dislocations move, hence the stress trapped within will redistribute. This redistribution can lead to residual stress reduction up to a level. In this review paper, all remarks above are considered, defined and accurately studied through various cases in order to address different application of vibratory stress relief and recent achievement in this field.

Pipeline Girth Weld Residual Stresses and the Effects of Hydrotesting

2002 ◽  
Author(s):  
Vinod Chauhan ◽  
Zhili Feng
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Structural Integrity ◽  
Steel Structures ◽  
Welding Residual Stress ◽  
Hole Drilling ◽  
Fe Model ◽  
Hole Drilling Method ◽  
Surface Residual Stresses ◽  
Stress Levels

Welding residual stresses are an important consideration in the fracture mechanics based fitness-for-purpose (FFP) assessment of steel structures. Reliable predictions of structural integrity can only be made provided that welding residual stresses are adequately accounted for. In the majority of cases, their magnitude is not known and can vary widely. In the absence of detailed information, it is common practice to assume that the welding residual stress is tensile, uniform through the thickness and of yield strength magnitude. However, this assumption will often lead to conservative fracture assessments which may lead to the conclusion that a weld repair is necessary when in practice the structure is safe to continue operation. In this paper, an integrated thermal-metallurgical-mechanical finite element (FE) model is described which simulates the formation of residual stresses at pipeline girth welds. The simulation takes into account detailed variations of the microstructure in the weld and heat affected zone (HAZ) in order to predict residual stress levels. Results of the FE analysis were validated with measurements of the microhardness and surface residual stresses using the air abrasive center hole drilling method. Sensitivity of residual stress levels to steel strength level, pipe wall thickness and pipe misalignment is discussed. The effects of hydrotesting and the alleviation of welding residual stresses are also described.

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 Weld Residual Stresses on Ductile Crack Behavior in AISI Type 316LN Stainless Steel Weld Joint

2018 ◽  
Author(s):  
Sai Deepak Namburu ◽  
Lakshmana Rao Chebolu ◽  
A. Krishnan Subramanian ◽  
Raghu Prakash ◽  
Sasikala Gomathy
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Crack Growth ◽  
Weld Joint ◽  
Volume Fraction ◽  
Growth Behavior ◽  
Welding Residual Stress ◽  
Crack Growth Behavior ◽  
Ductile Crack ◽  
Ductile Crack Growth

Welding residual stress is one of the main concerns in the process of fabrication and operation because of failures in welded steel joints due to its potential effect on structural integrity. This work focuses on the effect of welding residual stress on the ductile crack growth behavior in AISI 316LN welded CT specimens. Two-dimensional plane strain model has been used to simulate the CT specimen. X-ray diffraction technique is used to obtain residual stress value at the SS 316LN weld joint. The GTN model has been employed to estimate the ductile crack growth behavior in the CT-specimen. Results show that residual stresses influence the ductile crack growth behavior. The effect of residual stress has also been investigated for cases with different initial void volume fraction, crack lengths.

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