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.

Instrumented-Indentation-Technique-Based Residual Stress Characterization for Weldment of Structural Components

2006 ◽  
Author(s):  
Dongil Kwon ◽  
Jung-Suk Lee ◽  
Kwang-Ho Kim ◽  
Afshin Motarjemi ◽  
Julian Speck
Keyword(s):  
Residual Stress ◽  
Welding Process ◽  
Indentation Load ◽  
Welding Residual Stress ◽  
Hole Drilling ◽  
Structural Components ◽  
Instrumented Indentation ◽  
Indentation Technique ◽  
Safety And Reliability ◽  
Depth Curve

The weld joints in structural components have long been considered important sites for safety and reliability assessment. In particular, the residual stress in piping weldments induced by the welding process must be evaluated accurately before and during service. This study reports an indentation technique for evaluating welding residual stress nondestructively. Indentation load-depth curves were found to shift with the magnitude and direction of the residual stress. Nevertheless, contact depths in the stress-free and stressed states were constant at a specific indentation load. This means that residual stress induces additional load to keep contact depth constant at the same load. By taking these phenomena into account, welding residual stress was obtained directly from the indentation load-depth curve. In addition, the results were compared with values from the conventional hole-drilling and saw-cutting method.

Nondestructive Evaluation of Welding Residual Stress in Power Plant Facilities Using Instrumented Indentation Technique

2005 ◽  
Vol 297-300 ◽  
pp. 2122-2127 ◽  
Author(s):  
Yeol Choi ◽  
Yun Hee Lee ◽  
Jae Il Jang ◽  
Sang Ki Park ◽  
Kwang Ho Kim ◽  
...  
Keyword(s):  
Residual Stress ◽  
Power Plant ◽  
Welding Process ◽  
Indentation Load ◽  
Welding Residual Stress ◽  
Hole Drilling ◽  
Instrumented Indentation ◽  
Indentation Technique ◽  
Safety And Reliability ◽  
Depth Curve

The weld joints in power-plant pipelines have long been considered important sites for safety and reliability assessment. In particular, the residual stress in pipeline weldments induced by the welding process must be evaluated accurately before and during service. This study reports an indentation technique for evaluating welding residual stress nondestructively. Indentation load-depth curves were found to shift with the magnitude and direction of the residual stress. Nevertheless, contact depths in the stress-free and stressed states were constant at a specific indentation load. This means that residual stress induces additional load to keep contact depth constant at the same load. By taking these phenomena into account, welding residual stress was obtained directly from the indentation load-depth curve. In addition, the results were compared with values from the conventional hole-drilling and saw-cutting methods.

Evaluation of Welding Residual Stresses in Power Plant Facilities by Using a Newly Developed Indentation Technique

2002 ◽  
Author(s):  
Jae-il Jang ◽  
Dongil Son ◽  
Yeol Choi ◽  
Yun-Hee Lee ◽  
Won-Jae Ji ◽  
...  
Keyword(s):  
Residual Stress ◽  
Power Plant ◽  
Residual Stresses ◽  
Stress Measurement ◽  
Welding Residual Stress ◽  
Large Scatter ◽  
Indentation Technique ◽  
Cutting Test ◽  
Non Destructive ◽  
Non Destructive Techniques

It is well known that residual stress is one of the important problems in welding design/fabrications and sound maintenance of welded structures. Thus, the demand for quantitative evaluation of welding residual stress has been increased. However, conventional non-destructive techniques for welding residual stress measurement have many difficulties in in-field applications according to poor repeatability, large scatter of obtained data, complex procedures, inaccurate results, and etc. To overcome these difficulties, a newly developed indentation technique was proposed in this study, and applied to evaluate the welding residual stress in electric power plant facilities. By comparing with the stress values obtained from the destructive saw-cutting test, it could be concluded that the new indentation technique is very useful for quantitative/non-destructive evaluation of welding residual stresses in industrial fields such as power plant facilities.

Standardisation on Measurement and Interpretation of Residual Stress Data

2019 ◽  
Author(s):  
Ali Mirzaee-Sisan ◽  
P. John Bouchard ◽  
Foroogh Hosseinzadeh
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Practice Guidelines ◽  
Structural Integrity ◽  
Good Practice ◽  
Critical Assessment ◽  
Numerical Prediction ◽  
Specific Technique ◽  
Integrity Assessment

Abstract This paper highlights many unanswered questions relating to the characterisation of residual stresses in weldments and their treatment in engineering critical assessment and fitness for service assessment codes and standards. The need for an overarching standardisation framework is identified which goes beyond developing good practice guidelines for numerical prediction or measurement using a specific technique. The framework should cover all uncertainties and possible errors in measuring, simulating and interpreting residual stress in the context of structural integrity assessment.

Application of a portable indentation rig with Rockwell indenter to determine mechanical properties and residual stresses on an aluminum plate

2020 ◽  
Vol 55 (7-8) ◽  
pp. 246-257
Author(s):  
Saba Salmani Ghanbari ◽  
Amir-Hossein Mahmoudi
Keyword(s):  
Mechanical Properties ◽  
Residual Stresses ◽  
Structural Integrity ◽  
Indentation Load ◽  
Instrumented Indentation ◽  
Unknown Parameters ◽  
Plastic Properties ◽  
Wide Range ◽  
Portable Apparatus ◽  
Non Destructive

Measuring residual stresses is still a dilemma in many engineering applications. It is even more crucial when the industrial requirements demand for a non-destructive technique in order to avoid compromising the structural integrity of the engineering components. Furthermore, estimating the mechanical properties of the materials, especially when the components are aged, is of importance. Instrumented indentation has gained much interest in recent years. There are many studies in the literature which are focused on measuring residual stresses or mechanical properties using instrumented indentation. Since in many cases there is no possibility of transferring large samples or those under service, for possible measurements, having a portable rig can be very useful. Furthermore, indentation procedure is a low-cost non-destructive method with high accuracy which is able to measure the plastic properties of material as well as its residual stresses on which the designing and construction of the portable apparatus were based. The instrumented indentation testing details were followed according to the ASTM E2546-15 standard practice. In this research, a wide range of simulations were performed on a group of aluminum alloys in order to estimate the equi-biaxial residual stresses by analyzing the indentation load–displacement curves which were obtained from the experimental outcomes. Then neural networks were employed to estimate the unknown parameters. The performance accuracy of the designed portable apparatus and the acceptable precision of the introduced method were then verified with experimental tests performed on Al 2024-T351.

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.

Instrumented Indentation Technique to Measure Flow Properties: A Novel Way to Enhance the Accuracy of Integrity Assessment

2003 ◽  
Author(s):  
Jae-Il Jang ◽  
Yeol Choi ◽  
Yun-Hee Lee ◽  
Jung-Suk Lee ◽  
Dongil Kwon ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Crack Detection ◽  
Structural Integrity ◽  
Instrumented Indentation ◽  
Flow Properties ◽  
Integrity Assessment ◽  
Indentation Technique ◽  
Failure Assessment ◽  
Similar Vein ◽  
Non Destructive

While most in-field technologies for structural integrity diagnosis focus on precise crack detection, the instrumented indentation technique has emerged as one of the most practically useful technologies for non-destructive and quantitative in-field measurement of mechanical properties. In a similar vein, here an advanced indentation technique for determining tensile properties and its application to structural integrity assessment are introduced and discussed. This novel indentation technique can enhance the accuracy of fitness-for-service (FFS) assessment by application to failure assessment diagram (FAD) construction.

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 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.

The Validation of Weld Residual Stresses for Use in Structural Integrity Assessment

2011 ◽  
Vol 70 ◽  
pp. 297-302 ◽  
Author(s):  
Steve K. Bate ◽  
P. John Bouchard
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Residual Stresses ◽  
Structural Integrity ◽  
Measurement Techniques ◽  
Element Analysis ◽  
Integrity Assessment ◽  
Modelling Techniques ◽  
High Level ◽  
Assessment Procedures

The continued safe and reliable operation of plant invariably has to consider the assessment of defects in welded structural components. This requires some estimate of the residual stresses that have developed during the welding fabrication process. For as-welded structures these stresses can be of yield magnitude. Engineering critical assessment procedures such as R6, BS 7910, FITNET and API 579-1 provide simplified estimates, bounding profiles or advice on detailed analysis or measurement which can be applied to provide conservative estimates of the remaining life of plant. The use of finite element analysis (FEA) is being applied more frequently to predict residual stresses in welded components for assessment purposes. This calculation involves complex non-linear analyses with many assumptions. As a consequence, the accuracy and reliability of solutions is variable. In order to improve the consistency of weld modelling, and hence the accuracy and confidence in their use, a set of Guidelines covering the calculation of residual stresses have been developed. The residual stress calculations need to be validated before the results can be used in assessments and guidance on how to demonstrate the required standard of validation proof is provided with these Guidelines. The level of validation required, depends on the problem being solved and the sensitivity of the assessment to the presence of residual stress. For example a high level of validation may be required for assessments of safety critical plant. To support these calculations, measurements are required and a series of ‘Weld Residual Stress Benchmarks’, describing welded mock-ups which have been measured using various measurement techniques, are being collated which the users can then refer to when validating their finite element modelling techniques and thus provide a greater confidence in the predicted results.

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