Guidance on a Defect Interaction Effect for In-Plane Surface Cracks Using Elastic Finite Element Analyses

2008 ◽  
Author(s):  
Nam-Su Huh ◽  
Suhn Choi ◽  
Keun-Bae Park ◽  
Jong-Min Kim ◽  
Jae-Boong Choi ◽  
...  
Keyword(s):  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Interaction Effect ◽  
Elastic Stress ◽  
Plane Surface ◽  
Surface Cracks ◽  
Defect Interaction

The crack-tip stress fields and fracture mechanics assessment parameters, such as the elastic stress intensity factor and the elastic-plastic J-integral, for a surface crack can be significantly affected by adjacent cracks. Such a defect interaction effect due to multiple cracks can magnify the fracture mechanics assessment parameters. There are many factors to be considered, for instance the relative distance between adjacent cracks, crack shape and loading condition, to quantify a defect interaction effect on the fracture mechanics assessment parameters. Thus, the current guidance on a defect interaction effect (defect combination rule), including ASME Sec. XI, BS7910, British Energy R6 and API RP579, provide different rules for combining multiple surface cracks into a single surface crack. The present paper investigates a defect interaction effect by evaluating the elastic stress intensity factor of adjacent surface cracks in a plate along the crack front through detailed 3-dimensional elastic finite element analyses. The effects of the geometric parameters, the relative distance between cracks and the crack shape, on the stress intensity factor are systematically investigated. As for the loading condition, only axial tension is considered. Based on the elastic finite element results, the acceptability of the defect combination rules provided in the existing guidance was investigated, and the relevant recommendations on a defect interaction for in-plane surface cracks in a plate were discussed.

Finite Element Analysis of Polyethylene Pipe Butt Fusion Joints with Circumferential Surface Cracks

2013 ◽  
Vol 785-786 ◽  
pp. 1151-1158
Author(s):  
Zhi Bin Zhu ◽  
Xiao Xiang Yang ◽  
Li Jing Chen ◽  
Nai Chang Lin ◽  
Zhi Tuo Wang ◽  
...  
Keyword(s):  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Viscoelastic Material ◽  
Surface Crack ◽  
Crack Depth ◽  
Surface Cracks ◽  
Element Analysis ◽  
Polyethylene Pipe

Based on the viscoelastic material property of polyethylene pipe, software ANSYS was used to simulate and analyze the mechanical property of polyethylene pipe butt fusion joints with circumferential surface crack defects. The viscoelastic material creep parameters were characterized as Prony series and 1/4 node singular element was selected for meshing along the boundaries of the crack, then the stress intensity factor of polyethylene pipe butt fusion joints with circumferential surface crack was calculated under the uniform internal pressure. Through the finite element simulation, the result showed that polyethylene pipe were most likely to fracture failure when crack initiated. Thus the viscoelasticity of materials can be ignored when analyzing the stress intensity factor of circumferential surface cracks of polyethylene pipe. the main influencing factor of the circumferential crack defects was the ratio of the crack depth to the thickness of polyethylene pipe.

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.

Fracture Mechanics Fatigue Evaluation of a Flowline Clamp Connector Using Finite Element Modeling of a Crack

2019 ◽  
Author(s):  
Curtis Sifford ◽  
Ali Shirani
Keyword(s):  
Finite Element Analysis ◽  
Stress Intensity Factor ◽  
Finite Element ◽  
Fatigue Life ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Pressure Vessel ◽  
Crack Tip ◽  
Element Analysis

Abstract This paper presents the application of the rules from ASME Section VIII, Division 3 of the ASME Boiler and Pressure Vessel Code for a fracture mechanics evaluation to determine the damage tolerance and fatigue life of a flowline clamp connector. The guidelines from API 579-1 / ASME FFS-1 Fitness-For-Service for the stress analysis of a crack-like flaw have been considered for this assessment. The crack tip is modeled using a refined mesh around the crack tip that is referred to as a focused mesh approach in API 579-1 / ASME FFS-1. The driving force method is used as an alternative to the failure assessment diagram method to account for the influence of crack tip plasticity. The J integral is determined using elastic-plastic finite element analysis and converted to an equivalent stress intensity factor to be compared to the fracture toughness of the material. The fatigue life is calculated using the Paris Law equation and the stress intensity factor calculated from the finite element analysis. The allowable number of design cycles is determined using the safety factors required from Division 3 of the ASME Pressure Vessel Code.

Fracture Mechanics Fatigue Evaluation of a Flowline Clamp Connector Using Finite Element Modeling of a Crack

2018 ◽  
Author(s):  
Curtis Sifford ◽  
Ali Shirani
Keyword(s):  
Finite Element Analysis ◽  
Stress Intensity Factor ◽  
Finite Element ◽  
Fatigue Life ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Pressure Vessel ◽  
Crack Tip ◽  
Element Analysis

This paper presents the application of the rules from ASME Section VIII, Division 3 of the ASME Boiler and Pressure Vessel Code for a fracture mechanics evaluation to determine the damage tolerance and fatigue life of a flowline clamp connector. The guidelines from API 579-1 / ASME FFS-1 Fitness-For-Service for the stress analysis of a crack-like flaw have been considered for this assessment. The crack tip is modeled using a refined mesh around the crack tip that is referred to as a focused mesh approach in API 579-1 / ASME FFS-1. The driving force method is used as an alternative to the failure assessment diagram method to account for the influence of crack tip plasticity. The J integral is determined using elastic-plastic finite element analysis and converted to an equivalent stress intensity factor to be compared to the fracture toughness of the material. The fatigue life is calculated using the Paris Law equation and the stress intensity factor calculated from the finite element analysis. The allowable number of design cycles is determined using the safety factors required from Division 3 of the ASME Pressure Vessel Code.

scholarly journals The Application of Fracture Mechanics to the Problem of Crevasse Penetration

1976 ◽  
Vol 17 (76) ◽  
pp. 223-228 ◽  
Author(s):  
R. A. Smith
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Stress Intensity Factors ◽  
Close Agreement ◽  
Elastic Stress ◽  
Intensity Factors ◽  
Wide Range ◽  
Sharp Crack

AbstractThe elastic stress intensity factor is a parameter used in fracture mechanics to describe stress conditions in the vicinity of the tip of a sharp crack. By superimposing solutions of stress intensity factors for different loading conditions, equations are derived which model crevasses in ice. Solutions are presented for the theoretical depth of isolated crevasses, free from or partially filled with water. Close agreement exists with a previous calculation by Weertman using a different technique. The effect of crevasse spacing is investigated and it is demonstrated that closer spacing always reduces crevasse depth, but over a wide range of spacing the predicted variation in depth is slight.

J-Integral Evaluation for Calculating Structural Intensity and Stress Intensity Factor Using Commercial Finite Element (FE) Solutions

2013 ◽  
Vol 650 ◽  
pp. 379-384 ◽  
Author(s):  
Jong Wan Hu
Keyword(s):  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Integral Approach ◽  
J Integral ◽  
Fe Modeling ◽  
Linear Elastic ◽  
Structural Intensity

This report is mainly performed to investigate finite element (FE) modeling and post-processing capacities for fracture mechanics analyses characterized by the stress intensity factor (SIF) at successively stationary crack tip positions. As part of a linear elastic fracture mechanics (LEFM) analysis, the determination of stress intensity factor distribution can also be adopted by J-integral approach. The aim of this report is to review three papers related to estimate J-integrals through FE study and represent the theoretical backgrounds. Furthermore, the technical details for both FE modeling and SIF evaluation will be described in this report based on complete understanding of three reference papers. These numerical approaches to deal with SIF evaluation of general cracks can be applied in 2D and 3D FE models.

Influence of the Interaction on Stress Intensity Factor of Semi-Elliptical Surface Cracks

2005 ◽  
Author(s):  
Masayuki Kamaya
Keyword(s):  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Size ◽  
Surface Cracks ◽  
The Finite Element Method ◽  
Cracking Behavior ◽  
Tip Position ◽  
New Criteria

The interaction between multiple surface cracks is an important consideration in the cracking behavior due to thermal fatigue and stress corrosion cracking. However, it is difficult to evaluate the intensity of the interaction quantitatively because there are many factors such as the relative position, size and geometry of the cracks. Furthermore, the influence of the interaction differs with the crack tip position along the front. In this study, in order to investigate the intensity of interaction, the stress intensity factor (SIF) of interacting semi-elliptical surface cracks was evaluated by the finite element method and finite element alternating method. These methods enable us to evaluate the SIF of interacting cracks for various conditions. The analysis results reveal that the change in the averaged SIF along the crack front caused by coalescence of two cracks can be estimated from the change in the area size. The maximum interaction can be estimated by simple addition of the area size of two cracks regardless of the loading condition and relative crack size. To exclude the conservativeness caused by the current combination rule, new criteria are shown.

scholarly journals The Application of Fracture Mechanics to the Problem of Crevasse Penetration

1976 ◽  
Vol 17 (76) ◽  
pp. 223-228 ◽  
Author(s):  
R. A. Smith
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Stress Intensity Factors ◽  
Close Agreement ◽  
Elastic Stress ◽  
Intensity Factors ◽  
Wide Range ◽  
Sharp Crack

Abstract The elastic stress intensity factor is a parameter used in fracture mechanics to describe stress conditions in the vicinity of the tip of a sharp crack. By superimposing solutions of stress intensity factors for different loading conditions, equations are derived which model crevasses in ice. Solutions are presented for the theoretical depth of isolated crevasses, free from or partially filled with water. Close agreement exists with a previous calculation by Weertman using a different technique. The effect of crevasse spacing is investigated and it is demonstrated that closer spacing always reduces crevasse depth, but over a wide range of spacing the predicted variation in depth is slight.

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