Development of decenterized structural integrity assessment system : Post processor for estimating path-independent J-integral under thermal loading

2002 ◽  
Vol 2002.15 (0) ◽  
pp. 77-78
Author(s):  
Terutaka FUJIOKA ◽  
Tsuyoshi HASHIMOTO
Keyword(s):  
Thermal Loading ◽  
Structural Integrity ◽  
Assessment System ◽  
J Integral ◽  
Integrity Assessment

Strain-Based Failure Assessment Based on a Reference Strain Method for Welded Pipelines

2020 ◽  
Vol 142 (4) ◽  
Author(s):  
Jae-Sung Lee ◽  
Myung-Hyun Kim
Keyword(s):  
Reference Strain ◽  
Structural Integrity ◽  
Equivalent Stress ◽  
Strain Curve ◽  
Evaluation Procedure ◽  
J Integral ◽  
Element Analysis ◽  
Plastic Energy ◽  
Integrity Assessment ◽  
Strain Method

Abstract Engineering critical assessment (ECA) is an evaluation procedure for structures with flaws and has been widely applied for assessing pipeline integrity. The standards for structural integrity assessment, including BS 7910, involve stress-based ECA, and they are known to produce overly conservative results. Therefore, strain-based ECA has been recently developed as an alternative approach. One of the effective methods for improving the accuracy of strain-based ECA is the reference strain method. However, only a limited number of studies have applied this method to welded pipelines. Therefore, a numerical analysis based on strain-based ECA was performed for girth-welded joints with a circumferentially oriented internal surface crack. Particular attention was given to the strength mismatch effects. The equivalent stress–strain curve in BS7910 was used to reflect the strength mismatch effects in the reference strain. The results of the proposed method were validated with the results of a finite element analysis (FEA) in terms of the J-integral. Previous methods and the proposed method exhibit a reasonable correlation of the J-integral in the case of over-matching (OM). In the under-matching (UM) cases, while the previous procedures tended to underestimate or excessively overestimate the elastic-plastic energy release rate in comparison with the FEA, the proposed method evaluated the J-integral of pipelines with sufficient accuracy.

Development of cyber-based autonomous structural integrity assessment system for building structures

2013 ◽  
Author(s):  
M. Kurata ◽  
K. Fujita ◽  
X. Li ◽  
T. Yamazaki ◽  
M. Yamaguchi
Keyword(s):  
Structural Integrity ◽  
Assessment System ◽  
Building Structures ◽  
Integrity Assessment

Improved Incremental J-Integral Equations for Determining Crack Growth Resistance Curves

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Xian-Kui Zhu
Keyword(s):  
Fracture Mechanics ◽  
Crack Growth ◽  
Integral Equations ◽  
Structural Integrity ◽  
Test Procedure ◽  
Fracture Toughness Test ◽  
J Integral ◽  
Integrity Assessment ◽  
Growth Increments ◽  
Unloading Compliance

The J-integral resistance curve is the most important material properties in fracture mechanics that is often used for structural integrity assessment. ASTM E1820 is a commonly accepted fracture toughness test standard for measuring the critical value of J-integral at the onset of ductile fracture and J-R curve during ductile crack tearing. The recommended test procedure is the elastic unloading compliance method. For a stationary crack, the J-integral is simply calculated from the area under the load-displacement record using the η-factor equation. For a growing crack, the J-integral is calculated using the incremental equation proposed by Ernst et al. (1981, “Estimations on J-integral and Tearing Modulus T From a Single Specimen Test Record,” Fracture Mechanics: Thirteenth Conference, ASTM STP 743, pp. 476–502) to consider the crack growth correction. For the purpose of obtaining accurate J-integral values, ASTM E1820 requires small and uniform crack growth increments in a J-R curve test. In order to allow larger crack growth increments in an unloading compliance test, an improved J-integral estimation is needed. Based on the numerical integration techniques of forward rectangular, backward rectangular, and trapezoidal rules, three incremental J-integral equations are developed. It demonstrates that the current ASTM E1820 procedure is similar to the forward rectangular result, and the existing Garwood equation is similar to the backward rectangular result. The trapezoidal result has a higher accuracy than the other two, and thus it is proposed as a new formula to increase the accuracy of a J-R curve when a larger crack growth increment is used in testing. An analytic approach is then developed and used to evaluate the accuracy of the proposed incremental equations using single-edge bending and compact tension specimens for different hardening materials. It is followed by an experimental evaluation using actual fracture test data for HY80 steel. The results show that the proposed incremental J-integral equations can obtain much improved results of J-R curves for larger crack growth increments and are more accurate than the present ASTM E1820 equation.

Fracture Assessment for Pressurized Water Reactor Vessel Nozzles Subjected to Pressure and Thermal Loading

2021 ◽  
Author(s):  
Qibao Chu ◽  
Qing Wang ◽  
Yonggang Fang ◽  
Wei Tan
Keyword(s):  
Crack Front ◽  
Thermal Loading ◽  
Structural Integrity ◽  
Safety Margin ◽  
Pressurized Water Reactor ◽  
Pressurized Water ◽  
Integrity Assessment ◽  
Main Challenge ◽  
Fracture Assessment ◽  
3D Finite Element Method

Abstract To ensure the structure integrity of the RPV, the main challenge is the embrittlement of beltline material. However, the stress of inlet or outlet nozzles of the RPV which are in general reinforced in comparison with the beltline, is more complex especially under the thermal loads. In recently studies, a lot of works have been done to show that the nozzle region may be more challenging under some conditions. In this paper, a fracture assessment for the RPV nozzles subjected to pressure and thermal loading is discussed using the software ABAQUS 6.12 and Zen Crack 7.9-3. It includes: SIF calculation based on 3D finite element method; structural integrity assessment under a typical LOCA transient; and the fatigue crack growth evaluation under cyclic loading situations. The results show that the SIF along the crack front is obviously asymmetric, and only to assess the safety of the deepest point along the crack front in the ASME and RCC-MR codes may be reconsider. If the KIa criteria is applied, under a typical LOCA transient, it is difficult to obtain an effective fracture safety margin for a 1/4 thickness crack, while based on the KIC criteria, the nozzle is shown to be safe in the case study. The shape of the surface elongated crack (which is often easily produced in the nozzle area) tends to be circle under the cyclic pressure loading situation which shows the crack shape assumed in the ASME and RCC-MR codes is reasonable.

Advances in Development of J-Integral Experimental Estimation, Testing and Standardization

2011 ◽  
Author(s):  
Xian-Kui Zhu
Keyword(s):  
Fracture Toughness ◽  
Fracture Mechanics ◽  
Structural Integrity ◽  
Experimental Testing ◽  
Estimation Method ◽  
J Integral ◽  
Fracture Testing ◽  
Integrity Assessment ◽  
Ductile Materials ◽  
Experimental Estimation

The J-integral is an important concept in the elastic-plastic fracture mechanics, and serves as a critical material parameter to quantify the toughness or resistance of ductile materials against fracture. The relation between the J-integral and crack extension has been widely used as the resistance curve of ductile materials in fracture mechanics design and in structural integrity assessment. Experimental testing and evaluation have played a central role in providing reliable fracture toughness properties to fracture mechanics analysis. Since the J-integral concept was proposed, extensive efforts of investigations have been made to develop its experimental estimation method, testing technique and standardization, as evident in the ASTM E1820 — a commonly used fracture toughness testing standard. In recent years, significant progresses of the J-integral fracture testing and experimental estimation have been achieved, and a part of them was accepted and updated in ASTM E1820. To better understand and use this fracture testing standard, the present paper gives a brief review of historical efforts and recent advances in the development of the J-integral experimental estimation and standard testing.

scholarly journals Applying Fracture Mechanics to Cracked Components Subjected to Unloading

2016 ◽  
Author(s):  
Sam Oliver ◽  
Martyn Pavier ◽  
Mahmoud Mostafavi
Keyword(s):  
Finite Element Analysis ◽  
Structural Integrity ◽  
Fracture Parameter ◽  
J Integral ◽  
Single Cycle ◽  
Element Analysis ◽  
Hardening Material ◽  
Integrity Assessment ◽  
Plastic Materials ◽  
Elastic Plastic Materials

The J-integral is widely used as a fracture parameter for elastic-plastic materials. The J-integral describes the intensity of the stress field close to the crack tip in a power-law hardening material under a set of well-known restrictions. This study investigates what happens when one of these restrictions is broken, namely the requirement for no unloading to occur. In this work, a centre-cracked plate is subjected to a single cycle of load in which unloading occurs. A remote tensile stress is applied, then released, then applied again up to and beyond its initial magnitude. The J-integral at each step of the analysis is calculated using finite element analysis. Its validity as a fracture parameter at each step is discussed with the aid of results from a strip yield analysis of the same problem. The relevance of the results in the context of structural integrity assessment is discussed.

Structural Integrity Assessment of Major Nuclear Components Using Probabilistic Fracture Mechanics

2006 ◽  
Vol 306-308 ◽  
pp. 339-344
Author(s):  
Sang Min Lee ◽  
Yoon Suk Chang ◽  
Jae Boong Choi ◽  
Young Jin Kim
Keyword(s):  
Fracture Mechanics ◽  
Nuclear Power ◽  
Structural Integrity ◽  
Simulation Method ◽  
Assessment System ◽  
Integrity Assessment ◽  
Probabilistic Fracture Mechanics ◽  
Reliability Method ◽  
Nuclear Component ◽  
Assessment Procedures

The integrity of major components in nuclear power plant should be maintained during operation. In order to maintain the integrity of these components, complicated assessment procedures are required including fracture mechanics analysis, etc. The integrity assessment of components has been performed by using conventional deterministic approaches whilst there are lots of uncertainties to carry out a rational evaluation. In this respect, probabilistic integrity assessment is considered as an alternative method for nuclear component evaluation. The objectives of this paper are to develop an integrity assessment system based on probabilistic fracture mechanics and to estimate the failure probability of major nuclear components containing a defect. The integrity assessment system consists of three evaluation modules which are first order reliability method, second order reliability method and crude Monte Carlo simulation method. The developed system has been applied to evaluate failure probabilities of nuclear structural components such as steam generator tube and piping. The evaluation results showed a promising applicability of the probabilistic integrity assessment system.

Deformation Versus Modified J-Integral Resistance Curves for Ductile Materials

2012 ◽  
Author(s):  
Xian-Kui Zhu ◽  
Poh-Sang Lam
Keyword(s):  
Fracture Mechanics ◽  
Size Dependence ◽  
Structural Integrity ◽  
Experimental Results ◽  
Integral Parameter ◽  
Fracture Toughness Test ◽  
J Integral ◽  
Resistance Curve ◽  
Integrity Assessment ◽  
Resistance Curves

The J-integral resistance curve (or J-R curve) has been widely used as material property in fracture mechanics methods for structural integrity assessment. ASTM E1820 provides the standard fracture toughness test methods to measure JIc and J-R curves. The conventional J-R curve utilizes the J-integral parameter proposed by Rice [1] based on the deformation theory of plasticity. Due to crack-tip constraint effect, J-R curves of a material depend on specimen size, geometry type and crack length. In order to obtain size-independent resistance curves, Ernst [11] introduced a modified J-integral or Jm to minimize the size dependence and to characterize the resistance curve for large crack extensions beyond the limitation of deformation J-R curves. In the late 1980s and in the early 1990s, different experimental results showed the modified Jm-R curves were still size-dependent and may even behave worse than the deformation J-R curves. However, to date, the Jm-R curves are still regarded as “size-independent” in fracture mechanics analysis. To clarify this, the present paper gives a brief historical review of ductile resistance curves in terms of deformation J-integral and the modified Jm-integral, and evaluates the size dependence using experimental results for various steels and specimens, including A285 carbon steel and SENB specimens. A suggestion how to use the resistance curves is made accordingly.

scholarly journals ANALYSIS OF 3D SEMI-ELLIPTICAL CRACK ON REACTOR PRESSURE VESSEL WALL WITH LOAD STRESS AND CRACK RATIO

2019 ◽  
Vol 21 (1) ◽  
pp. 33
Author(s):  
Mike Susmikanti ◽  
Roziq Himawan ◽  
Entin Hartini ◽  
Rokhmadi Rokhmadi
Keyword(s):  
Pressure Vessel ◽  
Nuclear Power ◽  
Goodness Of Fit ◽  
Structural Integrity ◽  
Reactor Pressure Vessel ◽  
Elliptic Crack ◽  
J Integral ◽  
Integrity Assessment ◽  
Neutron Exposure ◽  
Reactor Pressure

Reactor Pressure Vessel (RPV) wall is an important component in the Nuclear Power Plant (NPP). During reactor operation, RPV is subjected to high temperature, pressure, and neutron exposure. This condition could lead to RPV structure failure. In order to assure the integrity of RPV during the reactor lifetime, it is mandatory to perform a structural integrity assessment of RPV by evaluating postulated crack in RPV. In the previous study, the crack has evaluated in 2-D. However, 3-D analysis of semi-elliptic crack shape in the surface of the thick plate for RPV wall using SA 508 Steel is yet to be analyzed. The objective of this study is to analyze and modeling the evaluation in variation crack ratio with some load stress in 3-D. The Stress Intensity Factor (SIF) and J-integral are used as crack parameter. The J-Integral were calculated using MSC MARC MENTAT based on Finite Element Method (FEM) for obtaining the SIF value. The inputs are a crack ratio, load stress, material property, and geometry. The modeling of SIF value and goodness of fit are using MINITAB. The fracture condition could be predicted in comparison to the SIF value and fracture toughness. For the load stress 70 MPa and 80 MPa, with a crack ratio 0.25, 0.33 and 0.5,  the material on RPV wall will in fracture condition.Keywords: Semi elliptic surface crack, 3-dimension, reactor pressure vessel, elastic-plastic fracture mechanics, J-integral

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