How Validates Residual Stress Effect on Fatigue Strength and SCC Evaluations?

2004 ◽  
Author(s):  
Masahito Mochizuki ◽  
Masao Toyoda
Keyword(s):  
Residual Stress ◽  
Fatigue Strength ◽  
Process Control ◽  
Stress Corrosion ◽  
Base Metal ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking ◽  
Stress Effect ◽  
Residual Stress Effect ◽  
Welding Processes

The availability of several processes for residual stress control is discussed in order to verify residual stress effect on fatigue strength and SCC evaluations The effectiveness protecting from fatigue and stress-corrosion cracking is validated by numerical analysis and actual experiment. In-process control during welding is the easiest method to reduce residual stress without any treatment after welding process. Control of welding pass sequence for multi-pass weld is applied to cruciform joints and butt-joints with X-shaped groove. Other processes after welding are confirmed the validity of residual stress improvement. Water jet peening is useful for obtaining compressive residual stress on the surface, and the tolerance against both fatigue and stress-corrosion cracking is verified. Cladding of corrosion-resistant material is also effective for preventing stress-corrosion cracking by the metallurgical respect on the basis that residual stress at the interface to base metal should be considered carefully. The residual stress of the base metal near the clad edge is confirmed within the tolerance of crack generation. Controlling methods both during and after welding processes are found to be effective for assuring the integrity of the welded components.

Technical Basis for Revisions to Section XI Appendix C for Alloy 600/82/182/132 Flaw Evaluation in Both PWR and BWR Environments

2008 ◽  
Author(s):  
Warren Bamford ◽  
Russell Cipolla ◽  
David Rudland ◽  
Guy De Boo
Keyword(s):  
Residual Stress ◽  
Stress Corrosion ◽  
Base Metal ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking ◽  
Flaw Size ◽  
Alloy 600 ◽  
Stress Determination ◽  
Residual Stress Determination ◽  
Technical Basis

This paper provides the technical basis for a revision to the flaw evaluation guidelines of Section XI, to cover Alloy 600 base metal and Alloy 182, 82, and 132 welds, for both PWR and BWR environments. Included are guidelines for residual stress determination, allowable flaw size calculation, and both fatigue and stress corrosion cracking predictions.

Finite Element Modelling of Transgranular Chloride Stress Corrosion Cracking in 304L Austenitic Stainless Steel

2008 ◽  
Author(s):  
Mark Wenman ◽  
James Barton ◽  
Kenneth Trethewey ◽  
Sean Jarman ◽  
Paul Chard-Tuckey
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Residual Stresses ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Chloride Ions ◽  
Corrosion Cracking ◽  
General Corrosion ◽  
Premature Failure ◽  
Welding Processes

Austenitic stainless steels (ASS) have excellent resistance to general corrosion. However, these steels can be susceptible to localised corrosion such as pitting and crevice corrosion. In the presence of a tensile stress they can also exhibit stress corrosion cracking (SCC). In pressurised water reactor (PWR) nuclear plant incidents of SCC, especially chloride-induced SCC (CISCC), have been observed. Chloride ions which can lead to CiSCC of even low carbon austenitic grades can be introduced from many sources including the atmosphere and materials introduced into the reactor environment. Stress can result from primary loading or introduced as secondary stresses, such as residual stress, through machining or welding processes. Residual stresses are internal self-balancing stresses that can act alone or together with a primary stress to cause premature failure of a component. 15 mm lengths of 304L ASS tube were subjected to an in-plane compression of between 1–10 mm before unloading. This created regions of plasticity and on relaxation the specimen contains a complex state of residual stresses that can be modelled by finite element (FE) methods. The tube specimens were then boiled in MgCl2 for 14 days before metallographic examination. A FE model of transgranular CISCC has been created by writing a VUMAT user subroutine implemented into the commercial FE code ABAQUS. The model is based on simple rules which include the initiation of surface corrosion pits from which, under mechanical control, SCC cracks may propagate. The model includes rules for SCC growth, based on hydrostatic stress state, and can incorporate the idea of grain orientation effects. Cracks created interact with and modify the residual stress field in the tube. Test results were then compared with model outputs. Crack morphologies and to a certain extent crack positions matched well with experiment. Attempts were made to calculate the crack tip driving forces from the model. The results also highlight the need to consider the importance of triaxial stress states, created by pits and cracks, and stress as a tensor rather than a scalar property. The effect of grain misorientation is also investigated, but so far, found to be of more limited importance for modelling transgranular CISCC.

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.

Effects of Cold Working and Heat Treatment on Caustic Stress Corrosion Cracking of Alloy 800M

2005 ◽  
Vol 297-300 ◽  
pp. 993-998 ◽  
Author(s):  
Chun Bo Huang ◽  
Guang Fu Li ◽  
Zhan Peng Lu ◽  
Jian Min Zeng ◽  
Wu Yang
Keyword(s):  
Heat Treatment ◽  
Residual Stress ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Cold Working ◽  
Corrosion Cracking ◽  
Caustic Solution ◽  
Surface Films ◽  
Microstructure Examination ◽  
Increasing Temperature

The effects of cold working and heat treatment on caustic stress corrosion cracking (SCC) of mill annealed (MA) alloy 800M in boiling solution of 50%NaOH+0.3%SiO2+0.3%Na2S2O3 were investigated by means of microstructure examination, tensile test, X-ray stress analysis, SCC testing of C-rings, Auger electron spectroscopy (AES), scanning electron microscopy (SEM) and metallography. The microstructure of alloy 800M under tested conditions was austenite. With a train of 25% by cold working, the grains of alloy 800M became longer, yield strength (YS) and ultimate tensile strength (UTS) increased, elongation (δ ) decreased, residual stress and the susceptibility to SCC increased. With increasing temperature of heat treatment of alloy 800M with cold working, the grains became bigger , residual stress, YS and UTS decreased and δ increased, the susceptibility to SCC of alloy 800M decreased. In boiling caustic solution, SCC cracks on the surfaces of C-ring specimens polarized potentiostatically at –20mV/SCE initiated from pitting and propagated along grain boundaries. AES analysis indicated that the surface films on MA alloy 800M were enriched in nickel and depleted in iron and chromium.

Effect of Ultrasonic Impact Treatment on the Stress Corrosion Cracking of 304 Stainless Steel Welded Joints

2008 ◽  
Author(s):  
Gang Ma ◽  
Xiang Ling
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Stainless Steel ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Welded Joints ◽  
Corrosion Cracking ◽  
Coarse Grained ◽  
304 Stainless Steel ◽  
Ultrasonic Impact Treatment

High tensile weld residual stress is an important factor contributing to stress corrosion cracking (SCC). Ultrasonic impact treatment (UIT) can produce compressive stresses on the surface of welded joints that negate the tensile stresses to enhance the SCC resistance of welded joints. In the present work, X-ray diffraction method was used to obtain the distribution of residual stress induced by UIT. The results showed that UIT could cause a large compressive residual stress up to 325.9MPa on the surface of the material. A 3D finite element model was established to simulate the UIT process by using a finite element software ABAQUS. The residual stress distribution of the AISI 304 stainless steel induced by UIT was predicted by finite element analysis. In order to demonstrate the improvement of the SCC resistance of the welded joints, the specimens were immersed in boiling 42% magnesium chloride solution during SCC testing, and untreated specimen cracked after immersion for 23 hours. In contrast, treated specimens with different coverage were tested for 1000 hours without visible stress corrosion cracks. The microstructure observation results revealed that a hardened layer was formed on the surface and the initial coarse-grained structure in the surface was refined into ultrafine grains. The above results indicate that UIT is an effective approach for protecting weldments against SCC.

X-Ray Fractography of Stress Corrosion Cracking in Aisi 4340 Steel Under Controlled Electrode potential

1987 ◽  
Vol 31 ◽  
pp. 269-276 ◽  
Author(s):  
Masaaki Tsuda ◽  
Yukio Hirose ◽  
Zenjiro Yajima ◽  
Keisuke Tanaka
Keyword(s):  
Residual Stress ◽  
Fracture Surface ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Electrode Potential ◽  
Diffraction Method ◽  
Corrosion Cracking ◽  
Fracture Mechanisms ◽  
X Ray ◽  
Electrode Potentials

The residual stress left on the fracture surface is one of the important parameters in X-ray fractography and has been used to analyze fracture mechanisms in fracture toughness and fatigue tests especially of high strength steels.In the present paper, the distribution of residual stress beneath the fracture surface made by stress corrosion cracking was measured by the X-ray diffraction method. Stress corrosion cracking tests were conducted by using compact tension specimens of 200°C tempered AISI steel in 3.5% NaCl solution environment under various electrode potentials. The effect of electrode potential on the growth kinetics of stress corrosion cracking is discussed on the basis of residual stress distribution.

Stress Corrosion Cracking and Non-Destructive Examination of Dissimilar Metal Welds and Alloy 600

2002 ◽  
Author(s):  
Deborah A. Jackson
Keyword(s):  
Stress Corrosion ◽  
Base Metal ◽  
Stress Corrosion Cracking ◽  
The United States ◽  
Corrosion Cracking ◽  
Primary System ◽  
Alloy 600 ◽  
Control Rod ◽  
System Pressure ◽  
Non Destructive

The United States Nuclear Regulatory Commission (USNRC) has conducted research since 1977 in the areas of environmentally assisted cracking and assessment and reliability of non-destructive examination (NDE). Recent occurrences of cracking in Alloy 82/182 welds and Alloy 600 base metal at several domestic and overseas plants have raised several issues relating to both of these areas of NRC research. The occurrences of cracking were identified by the discovery of boric acid deposits resulting from through-wall cracking in the primary system pressure boundary. Analyses indicate that the cracking has occurred due to primary water stress corrosion cracking (PWSCC) in Alloy 82/182 welds. This cracking has occurred in two different locations: in hot leg nozzle-to-safe end welds and in control rod drive mechanism (CRDM) nozzle welds. The cracking associated with safe-end welds is important due to the potential for a large loss of reactor coolant inventory, and the cracking of CRDM nozzle base metal and welds, particularly circumferential cracking of CRDM nozzle base metal, is important due to the potential for a control rod to eject resulting in a loss of coolant accident. The industry response in the U.S. to this cracking is being coordinated through the Electric Power Research Institute’s Materials Reliability Project (EPRI-MRP) in a comprehensive, multifaceted effort. Although the industry program is addressing many of the issues raised by these cracking occurrences, confirmatory research is necessary for the staff to evaluate the work conducted by industry groups. Several issues requiring additional consideration regarding the generic implications of these isolated events have been identified. This paper will discuss the recent events of significant cracking in domestic and foreign plants, discuss the limitations of NDE in detecting SCC, identify deficiencies in information available in this area, discuss the USNRC approach to address these issues, and discuss the development of an international cooperative effort.

A Development of the Technical Basis for the New Code Case “Mitigation of PWSCC and CISCC in ASME Section III Components by the Advanced Surface Stress Improvement Technology”

2019 ◽  
Author(s):  
S. W. Cho ◽  
W. G. Yi ◽  
N. Mohr ◽  
A. Amanov ◽  
C. Stover ◽  
...  
Keyword(s):  
Residual Stress ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Surface Stress ◽  
Compressive Residual Stress ◽  
Corrosion Cracking ◽  
Chloride Salt ◽  
Spent Fuel ◽  
Term Operation ◽  
Technical Basis

Abstract It is necessary for nuclear power plant operation and spent fuel canisters to provide a sound technical basis for the safety and security of long-term operation and storage respectively. A new code case for mitigation of Primary Water Stress Corrosion Cracking (PWSCC) and Chloride Induced Stress Corrosion Cracking (CISCC) in Section III components by using an advanced surface stress improvement technology (ASSIT) is being developed by Task Group ASSIT which is one of the task groups under the ASME (The American Society of Mechanical Engineers). The necessary technical reports supporting this code case are being developed as part of joint research projects conducted by Doosan Heavy Industries and Construction (DOOSAN), Electric Power Research Institute (EPRI) and Sun Moon University (SMU). A well-known approach to prevent PWSCC and CISCC are to be performed using materials resistant to PWSCC and CISCC. The objective is to eliminate residual tensile stresses, or to induce compressive residual stress using ASSIT methods such as laser peening, water jet/cavitation peening, ultrasonic peening and ultrasonic nanocrystal surface modification (UNSM). Performance and measurement criteria for mitigation of PWSCC by ASSIT will be established based on the magnitude of surface stress and depth of compressive residual stress, sustainability, inspectability and lack of adverse effects. Additionally, for mitigation of CISCC by ASSIT, the evaluation of chloride induced corrosion pitting, the depth and density of corrosion pits and stress corrosion crack initiation and growth under chloride salt chemistry conditions are also being examined. This paper explains the approach, and progress of testing and analysis. The results and details from testing and analysis will be presented in a future PVP paper upon completion.

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