Fracture Mechanics Analysis of a PWR Under PTS Using XFEM and Input From TRACE

2019 ◽  
Author(s):  
Diego F. Mora ◽  
Roman Mukin ◽  
Oriol Costa Garrido ◽  
Markus Niffenegger
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Boundary Conditions ◽  
Three Dimensional ◽  
Element Model ◽  
Integrity Assessment ◽  
Mechanics Analysis ◽  
Dynamic Cooling

Abstract In this paper, an integrity assessment of a reference Reactor Pressure Vessel (RPV) under Pressurized Thermal Shock (PTS) is performed. The assessment is based on a multi-step simulation scheme, which includes the thermo-hydraulic, thermo-mechanical and fracture mechanics analyses. The proposed strategy uses a three dimensional (3D) finite element model (FEM) of the RPV with the Abaqus code to solve the thermo-mechanical problem for the scenario of a Large-Break Loss-of-Coolant Accident (LBLOCA). In order to obtain the boundary conditions for the thermal analysis, the thermo-hydraulic results from a 3D RPV model developed in the system code TRACE are used. The fracture mechanics analysis is carried out on submodels defined on the areas of interest. Submodels containing cracks or flaws are also located in regions of the RPV where there might be a concentration of stresses during the PTS. The calculation of stress intensity factor (SIF) makes use of the eXtended FEM (XFEM) approach. The computed SIF of the postulated cracks at the inner surface of the RPV wall are compared with the ASME fracture toughness curve of the embrittled RPV material. For different transient scenarios, the boundary conditions were previously calculated with a computational fluid dynamics (CFD) model. However, cross-verification of the results has shown consistency of both CFD and TRACE models. Moreover, the use of the later is very convenient for the integrity analyses as it is clearly less computationally expensive than CFD. Therefore, it can be used to calculate different PTS scenarios including different break sizes and break locations. The main findings from fracture mechanics analyses of the RPV subjected to LBLOCA are summarized and compared. The presented results also allow us to study the influence of the dynamic cooling plume on the stress intensity factor in more detail than with the conventional one-dimensional method. However, the plumes calculated with both approaches are different. How much this difference affects the integrity assessment of the RPV is discussed in the paper.

Stress Intensity Factors for Complex-Cracked Pipes Based on Elastic Finite Element Analyses

2015 ◽  
Author(s):  
Jae-Uk Jeong ◽  
Jae-Boong Choi ◽  
Nam-Su Huh ◽  
Yun-Jae Kim
Keyword(s):  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Stress Intensity Factors ◽  
Intensity Factors ◽  
Integrity Assessment ◽  
Complex Crack ◽  
Leak Before Break

A complex crack is one of severe crack that can occur at the dissimilar metal weld of nuclear piping. A relevant fracture mechanics assessment for a pipe with a complex crack has become interested in structural integrity of nuclear piping. A stress intensity factor is not only an important parameter in the linear elastic fracture mechanics to predict the stress state at the crack tip, but also one of variables to calculate the J-integral in the elastic plastic fracture mechanics. The accurate calculation of stress intensity factor is required for integrity assessment of nuclear piping system based on Leak-Before-Break concept. In the present paper, stress intensity factors of complex-cracked pipes were calculated by using detailed 3-dimensional finite element analysis. As loading conditions, global bending, axial tension and internal pressure were considered. Based on the present FE works, the values of shape factors for stress intensity factor of complex-cracked pipes are suggested according to a variables change of complex crack geometries and pipes size. Furthermore, the closed-form expressions based on correction factor are newly suggested as a function of geometric variables. These new solutions can be used to Leak-Before-Break evaluation for complex-cracked pipes in the step of elastic J calculation.

Application of 3D Fracture Mechanics for Improved Crack Growth Predictions of Gas Turbine Components

2017 ◽  
Author(s):  
Kanwardeep S. Bhachu ◽  
Santosh B. Narasimhachary ◽  
Sachin R. Shinde ◽  
Phillip W. Gravett
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Gas Turbine ◽  
Crack Growth ◽  
Structural Integrity ◽  
Crack Arrest ◽  
3D Crack Growth ◽  
Mechanics Analysis

Fracture mechanics analysis is essential for demonstrating structural integrity of gas turbine components. Usually, analyses based on simpler 2D stress intensity solutions provide reasonable approximations of crack growth. However, in some cases, simpler 2D solutions are too-conservative and does not provide realistic crack growth predictions; often due to its inability to account for actual 3D geometry, and complex thermal-mechanical stress fields. In such cases, 3D fracture mechanics analysis provides extra fidelity to crack growth predictions due to increased accuracy of the stress intensity factor calculations. Improved fidelity often leads to benefits for gas turbine components by reducing design margins, improving engine efficiency, and decreasing life cycle costs. In this paper, the application of 3D fracture mechanics analysis on a gas turbine blade for predicting crack arrest is presented. A comparison of stress intensity factor values from 3D and 2D analysis is also shown. The 3D crack growth analysis was performed by using FRANC3D in conjunction with ANSYS.

Closed Form Expressions for Fracture Mechanics Analysis of Cracked Pipes

1985 ◽  
Vol 107 (2) ◽  
pp. 203-205 ◽  
Author(s):  
A. Zahoor
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Internal Pressure ◽  
Closed Form ◽  
Bending Moment ◽  
Axial Tension ◽  
Mechanics Analysis ◽  
Pipe Radius

Closed form stress intensity factor (K1) expressions are presented for cracks in pipes subjected to a variety of loading conditions. The loadings considered are: 1) axial tension, 2) remotely applied bending moment, and 3) internal pressure. Expressions are presented for circumferential and axial cracks, and include both part-through and through-wall crack geometries. The closed form K1 expressions are valid for pipe radius to wall thickness ratio between 5 and 20.

Probabilistic Fracture Mechanics Analysis of Multiple Cracks in Cylindrical Pressure Vessel

2011 ◽  
Vol 462-463 ◽  
pp. 1314-1318 ◽  
Author(s):  
Tatacipta Dirgantara ◽  
Tuppi Summa Wicaksono ◽  
Thahir Ahmad ◽  
Indra Sadikin ◽  
Djoko Suharto ◽  
...  
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Service Life ◽  
Intensity Factor ◽  
Pressure Vessel ◽  
Initial Crack ◽  
Multiple Cracks ◽  
Cylindrical Pressure Vessel ◽  
Mechanics Analysis

In this work, a probabilistic fracture mechanics analysis of multiple cracks in a cylindrical pressure vessel was conducted. The analysis was performed to predict service life of a pressure vessel with a certain level of reliability if the vessel has a multiple internal surface cracks that interact each other. The stress intensity factor of multiple cracks configuration was determined from the stress intensity factor of a single surface crack in a plate subjected to uni-axial load and the interaction factor between the cracks. In this work, the Swift’s crack link-up criterion was employed. These parameters together with several other stochastic parameters, i.e. initial crack size, Paris’s crack propagation constants and fracture toughness, were then used to calculate the probability of failure with a certain level of reliability. The failure probability was simulated using guided direct simulation, for cycle-by-cycle crack propagation, to find the expected service life and the mode of failure (leak or break). A case study of a high-pressure vessel having different initial crack sizes have been simulated and the service life with 99,99% reliability were determined.

Three-Dimensional T-Stress to Predict the Directional Stability of Crack Propagation in a Pipeline with External Surface Crack

2012 ◽  
Vol 498 ◽  
pp. 31-41 ◽  
Author(s):  
H. Moustabchir ◽  
Z. Azari ◽  
S. Hariri ◽  
I. Dmytrakh
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Numerical Solutions ◽  
Three Dimensional ◽  
Experimental Results ◽  
Strain Gauges ◽  
Geometrical Parameters ◽  
Integrity Assessment ◽  
T Stress

In industrial structures, the presence of cracks under critical loads leads to complete ruin. Fracture rupture mechanics allowed studying macroscopic defect harmfulness. This requires the knowledge of the stresses fields and the deformations near of the crack. Our work is an application of fracture mechanics into the domain of the pressurised structures with defects in the presence of the T-stress parameter. Design of this type of structures is subjected to standards, codes and regulations driven by the potential risk which they represent. The knowledge of the limit pressures in these structures allows appreciating the safety domain of. We present numerical solutions by the commercial code CASTEM2000 in three dimensional 3D and experimental results for the stress intensity factor SIF and the transverse stress noted T-stress, distribution at defect-tip in a Pipeline. The elastic structure modelling will be treated by the finites elements simulation. We study the influence of the geometrical parameters for surface notches and the measures of strains near defects in the studied model have been made by strain gauges. On the basis of the detailed 3D elastic FE analysis results, solutions presented are believed to be the most accurate, and thus provide valuable information for structural integrity assessment considering a notch-tip constraint. The experimental results validate allow numerical simulation. Keywords: Crack, Pressure, T-stress, Stress Intensity factor, Finite element simulation, Strain gauges,

Evaluation of the fatigue life of a sintered machine element under the sliding/rolling contact condition based on fracture mechanics

2002 ◽  
Vol 37 (4) ◽  
pp. 327-336
Author(s):  
A Yoshida ◽  
Y Ohue ◽  
H Ishikawa
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Testing Machine ◽  
Element Model ◽  
Contact Condition ◽  
Rolling Contact ◽  
Hertzian Contact ◽  
Stress Intensity Factor Range

In order to evaluate the surface durability of sintered machine elements, the fatigue lives of 28 kinds of sintered roller under a sliding/rolling contact condition were estimated using Paris's law based on linear fracture mechanics. The fatigue tests were conducted using a two-cylinder testing machine. The stress intensity factor for the mode II under the Hertzian contact condition was calculated using the finite element model. The value of the stress intensity factor became larger as the crack length became longer to the contact surface, and the value of the stress intensity factor range was independent of the crack angle. It could be clarified that the fatigue lives of the sintered rollers depended on the pore diameter and the hardness. It was obvious that the pore distribution has to be taken into consideration to estimate the fatigue lives of the sintered rollers more precisely.

Three-Dimensional Fracture Mechanics Analyses of Single-Edge Cracked Plate Specimens

2014 ◽  
Author(s):  
Zhaoyu Jin ◽  
Xin Wang
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Three Dimensional ◽  
Loading Conditions ◽  
Stress Distributions ◽  
Single Edge ◽  
Cracked Plate ◽  
Nonlinear Stress

In this paper, single-edge cracked plate (SECP) specimens are analyzed using three-dimensional finite element analysis under mode I loading conditions. The stress intensity factor K, T11 and T33 stresses along the crack front of the SECP specimens with the crack surface subjected to uniform, linear, parabolic or cubic stress distributions are calculated. The relative crack depth, a/W, is varied by 0.2, 0.4, 0.6 or 0.8. And the relative thickness, t/W, is chosen by 0.1, 0.2, 0.5, 1.0, 2.0 or 4.0, respectively. For engineering applications, empirical equations of normalized stress intensity factor K, T11 and T33 stress at the mid-plane are also obtained. By superposition, the results enable the calculations of these fracture mechanics parameters under the loading conditions of tension, bending and nonlinear stress distributions.

Fracture Mechanics Analysis of the Dynamic Stress Intensity Factor of 3-Point Bending Specimen Suffering Cyclic Loads

2011 ◽  
Vol 143-144 ◽  
pp. 503-507 ◽  
Author(s):  
Ya Yu Huang ◽  
Xiang Ping Hu ◽  
Tao Hong Liao
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Dynamic Stress ◽  
Dynamic Stress Intensity Factor ◽  
Cyclic Loads ◽  
Fracture Characteristics ◽  
Mechanics Analysis ◽  
Practical Engineering

Fracture mechanics analysis of the Dynamic Stress Intensity Factor of a pre-cracked 3-Point Bending Specimen suffering cyclic loads has been studied. Using the theoretical equivalent system of the pre-cracked 3-Point Bending Specimen, the Dynamic Stress Intensity Factor could be obtained theoretically. The finite element method was then applied to study the dynamic behaviors of the Dynamic Stress Intensity Factor under different cyclic loads' conditions using the standard software ABAQUS. The results have also been analyzed and discussed, which provided a deeper view for the fracture characteristics of the materials and could be used to guide further researches and practical engineering design.

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