Improvement of Residual Stresses of Circumferential Joint of Pipe by Heat-Sink Welding

1986 ◽  
Vol 108 (1) ◽  
pp. 14-23 ◽  
Author(s):  
Y. Ueda ◽  
K. Nakacho ◽  
T. Shimizu
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Heat Sink ◽  
Welding Residual Stress ◽  
Water Cooling ◽  
Intergranular Stress Corrosion ◽  
Steel Pipes ◽  
Nuclear Plants ◽  
Intergranular Stress Corrosion Cracking ◽  
Theoretical Analyses

Intergranular stress corrosion cracking may occur in some specific conditions on the inner surface of the welded joints of stainless steel pipes which are furnished in nuclear plants. One of the remedies for this cracking is to convert welding residual stress on this surface into compression. In this research, in order to improve welding residual stress, the authors investigated the effectiveness of the heat-sink welding (water cooling) by conducting theoretical analyses and experiments on SUS 304 pipes of different sizes in comparison with the conventional welding. The mechanisms of production of residual stresses by both methods are clarified and conditions for effective application of the heat-sink welding such as limitation of heat input, procedure of welding are indicated.

The Effect of Pipe Thickness on Residual Stresses due to Girth Welds

1982 ◽  
Vol 104 (3) ◽  
pp. 204-209 ◽  
Author(s):  
E. F. Rybicki ◽  
P. A. McGuire ◽  
E. Merrick ◽  
J. Wert
Keyword(s):  
Residual Stress ◽  
Stainless Steel ◽  
Residual Stresses ◽  
304 Stainless Steel ◽  
Stress Distributions ◽  
Intergranular Stress Corrosion ◽  
Steel Pipes ◽  
Inner Surface ◽  
Girth Welds ◽  
Intergranular Stress Corrosion Cracking

This paper addresses the question of what effect the pipe thickness has on weld residual stresses in 304 stainless steel piping. Two diameters are considered. These are nominal 4-in. and 10-in. diameters. Four pipe wall thicknesses corresponding to schedules 10, 40, 80, and 160 are examined for each pipe. The focus is on residual stress distributions on the pipe inner surface because this is a primary site for intergranular stress corrosion cracking in 304 stainless steel pipes. The trends in residual stress values are toward more compressive stresses at the pipe inner surface for thicker pipes with the same nominal diameter. Residual axial stresses for the thick 10-in. schedule 160 pipe were found to be compressive while those for the thinner schedule 80 pipe were tensile. X-ray residual stress data for a 6-in-dia schedule 160 pipe fall between the results for the 4-in. and 10-in. schedule 160 pipes and support the findings of the study.

A Computational Model of Backlay Welding for Controlling Residual Stresses in Welded Pipes

1981 ◽  
Vol 103 (3) ◽  
pp. 226-232 ◽  
Author(s):  
F. W. Brust ◽  
E. F. Rybicki
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Computational Model ◽  
Welding Process ◽  
Computational Results ◽  
Intergranular Stress Corrosion ◽  
Inner Surface ◽  
Piping Systems ◽  
Intergranular Stress Corrosion Cracking ◽  
Compressive Residual Stresses

Intergranular Stress Corrosion Cracking (IGSCC) has been a problem in Boiling Water Reactor (BWR) piping systems. One method for retarding IGSCC is to eliminate tensile residual stresses at the pipe inner surface in the heat affected zone produced by the welding process. A method called backlay welding can be effective in producing compressive residual stresses at the pipe inner surface. This paper describes a computational model and its use in examining the effectiveness of the backlay welding process. The model has demonstrated an ability to predict weld-induced residual stresses for a variety of pipe sizes and welding conditions. Computational results for backlay welding are in agreement with residual stress data. The mechanisms causing residual stresses and the effect of the number of backlay weld layers on residual stresses are discussed.

BWR Shroud Weld Off-Axis Crack Growth Investigation

2017 ◽  
Author(s):  
John E. Broussard ◽  
Wayne Lunceford
Keyword(s):  
Residual Stress ◽  
Stainless Steel ◽  
Stress Field ◽  
Welding Residual Stress ◽  
Steel Weld ◽  
Intergranular Stress Corrosion ◽  
The Core ◽  
Stainless Steel Weld ◽  
Residual Stress Analysis ◽  
Intergranular Stress Corrosion Cracking

Recent inspections have identified cracking in the core shroud that is atypical in that the cracks exhibit characteristics inconsistent with traditionally reported intergranular stress corrosion cracking (IGSCC) occurring within stainless steel weld heat-affected zones (HAZs). These flaws are oriented transverse to the weld and are observed to propagate significantly beyond the weld HAZ. This paper describes the investigations which have been performed to quantify the likely limits on growth of these “off-axis” SCC cracks. The investigation includes welding residual stress analysis to determine the stress field present adjacent to the weld and crack tip SIF calculations for the bivariant stress field.

scholarly journals Residual Stress Measurements in Mo/CuCrZr Tiles Using Neutron Diffraction

2008 ◽  
Vol 59 ◽  
pp. 299-303
Author(s):  
K. Mergia ◽  
Marco Grattarola ◽  
S. Messoloras ◽  
Carlo Gualco ◽  
Michael Hofmann
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Neutron Diffraction ◽  
Residual Stresses ◽  
Heat Sink ◽  
High Yield ◽  
Fusion Reactors ◽  
Plasma Facing Components ◽  
Induced Stresses ◽  
Compliant Layer

In plasma facing components (PFC) for nuclear fusion reactors tungsten or carbon based tiles need to be cooled through a heat sink. The joint between the PFC and the heat sink can be realized using a brazing process through the employment of compliant layer of either a low yield material, like copper, or a high yield material, like molybdenum. Experimental verification of the induced stresses during the brazing process is of vital importance. Strains and residual stresses have been measured in Mo/CuCrZr brazed tiles using neutron diffraction. The strains and stresses were measured in Mo tile along the weld direction and at different distances from it. The experimental results are compared with Finite Element Simulations.

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.

NRC/EPRI Residual Stress Validation Program Phase I: Experimental Specimen Modeling and Measurement

2011 ◽  
Author(s):  
J. Broussard ◽  
P. Crooker
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Phase 1 ◽  
Measurement Techniques ◽  
Corrosion Cracking ◽  
Welding Residual Stress ◽  
Hole Drilling ◽  
Pressurized Water

The US Nuclear Regulatory Commission (NRC) and the Electric Power Research Institute (EPRI) are working cooperatively under a memorandum of understanding to validate welding residual stress predictions in pressurized water reactor primary cooling loop components containing dissimilar metal welds. These stresses are of interest as DM welds in pressurized water reactors are susceptible to primary water stress corrosion cracking (PWSCC) and tensile weld residual stresses are one of the primary drivers of this stress corrosion cracking mechanism. The NRC/EPRI weld residual stress (WRS) program currently consists of four phases, with each phase increasing in complexity from lab size specimens to component mock-ups and ex-plant material. This paper describes the Phase 1 program, which comprised an initial period of learning and research for both FEA methods and measurement techniques using simple welded specimens. The Phase 1 specimens include a number of plate and cylinder geometries, each designed to provide a controlled configuration for maximum repeatability of measurements and modeling. A spectrum of surface and through-wall residual stress measurement techniques have been explored using the Phase 1 specimens, including incremental hole drilling, ring-core, and x-ray diffraction for surface stresses and neutron diffraction, deep-hole drilling, and contour method for through-wall stresses. The measured residual stresses are compared to the predicted stress results from a number of researchers employing a variety of modeling techniques. Comparisons between the various measurement techniques and among the modeling results have allowed for greater insight into the impact of various parameters on predicted versus measured residual stress. This paper will also discuss the technical challenges and lessons learned as part of the DM weld materials residual stress measurements.

The Effects of Loadings on Welding Residual Stresses and Assessment of Fracture Parameters in a Welding Residual Stress Field

2011 ◽  
Author(s):  
Liwu Wei ◽  
Weijing He ◽  
Simon Smith
Keyword(s):  
Residual Stress ◽  
Stress Field ◽  
Residual Stresses ◽  
Path Dependence ◽  
Welding Residual Stress ◽  
Assessment Procedure ◽  
Fe Model ◽  
J Integral ◽  
Residual Stress Field ◽  
Growing Crack

The level of welding residual stress is an important consideration in the ECA of a structure or component such as a pipeline girth weld. Such a consideration is further complicated by their variation under load and the complexity involved in the proper assessment of fracture mechanics parameters in a welding residual stress field. In this work, 2D axi-symmetric FEA models for simulation of welding residual stresses in pipe girth welds were first developed. The modelling method was validated using experimental measurements from a 19-pass girth weld. The modeling method was used on a 3-pass pipe girth weld to predict the residual stresses and variation under various static and fatigue loadings. The predicted relaxation in welding residual stress is compared to the solutions recommended in the defect assessment procedure BS 7910. Fully circumferential internal cracks of different sizes were introduced into the FE model of the three-pass girth weld. Two methods were used to introduce a crack. In one method the crack was introduced instantaneously and the other method introduced the crack progressively. Physically, the instantaneously introduced crack represents a crack originated from manufacturing or fabrication processes, while the progressively growing crack simulates a fatigue crack induced during service. The J-integral values for the various cracks in the welding residual stress field were assessed and compared. This analysis was conducted for a welding residual stress field as a result of a welding simulation rather than for a residual stress field due to a prescribed temperature distribution as considered by the majority of previous investigations. The validation with the 19-pass welded pipe demonstrated that the welding residual stress in a pipe girth weld can be predicted reasonably well. The relaxation and redistribution of welding residual stresses in the three-pass weld were found to be significantly affected by the magnitude of applied loads and the strain hardening models. The number of cycles in fatigue loading was shown to have little effect on relaxation of residual stresses, but the range and maximum load together governed the relaxation effect. A significant reduction in residual stresses was induced after first cycle but subsequent cycles had no marked effect. The method of introducing a crack in a FE model, progressively or instantaneously, has a significant effect on J-integral, with a lower value of J obtained for a progressively growing crack. The path-dependence of the J-integral in a welding residual stress field is discussed.

An Analysis of Residual Stress Improvement for a Dissimilar Metal Nozzle-to-Pipe Weld by Using the Heat Sink Method

2008 ◽  
Author(s):  
J.-S. Park ◽  
J.-M. Kim ◽  
G.-H. Sohn ◽  
Y.-H. Kim
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Heat Sink ◽  
Nuclear Power ◽  
Power Plants ◽  
Base Alloy ◽  
Fatigue Cracking ◽  
Hole Drilling ◽  
Fe Model ◽  
Dissimilar Metal

This study is concerned with the mechanics analysis of residual stress improvement by the heat sink method applied to a dissimilar metal weld (DMW) for the use in nuclear power plants. The DMW joint considered here is composed of ferritic low-alloy steel nozzle, austenitic stainless steel safe-end, and nickel-base alloy A52 weld metal. To prepare the DMW joint with a narrow-gap, the gas tungsten arc welding (GTAW) process is utilized, and the heat sink method is employed to control thermal gradients developed in the critical region of work pieces during welding. Weld residual stresses are computed by the non-linear thermal elasto-plastic analysis using the axisymmetric finite element (FE) model, for which temperature-dependent thermal and mechanical properties of the materials are considered. A full-scale mock-up test is conducted to validate analytical solution for the DMW joint, and residual stresses are measured by using the hole-drilling method. Results of the FE modeling and mock-up test for the DMW joint are compared and effects of the heat sink method are discussed. It is found that a significant amount of residual compressive stresses can be developed on the inner surface of the DMW joint by using the heat sink method, which can effectively reduce the susceptibility of the welded materials to stress corrosion or fatigue cracking.

Sign in / Sign up

Export Citation Format

Share Document