A Flaw Proximity Rule for Interacting Surface Cracks Based on Elastic-Plastic Fracture Analysis

2009 ◽  
Author(s):  
Masayuki Kamaya
Keyword(s):  
Structural Reliability ◽  
Crack Depth ◽  
Crack Size ◽  
Multiple Cracks ◽  
J Integral ◽  
Surface Cracks ◽  
Elastic Plastic ◽  
Offset Distance ◽  
Bending Load ◽  
The Relationship

When multiple cracks approach one another, the stress intensity factor and J-integral value of cracks are likely to change due to the interaction of the stress field. Since the changes in these parameters are not always conservative in structural reliability evaluations, the interaction between multiple cracks should be taken into account. Section XI of the ASME Boiler and Pressure Vessel Code provides a flaw characterization rule for interacting multiple cracks. In Section XI, adjacent cracks are replaced with a coalesced single crack when the distance between the cracks is less than half of the crack depth. However, the criterion for the offset distance is given as an absolute value, although the magnitude of the interaction depends on the crack size. In the current study, an alternative criterion for the offset distance was examined. Elastic-plastic analyses were performed for interacting semicircular and semi-elliptical surface cracks by the finite element method under a tensile and bending load. The change in the J-integral values due to the relative spacing of cracks was investigated. Based on the relationship between the magnitude of the interaction and the relative position of the cracks, the allowable condition for the offset distance was discussed.

A Criterion for Combination Rule in Flaw Assessment of Parallel Surface Cracks

2011 ◽  
Vol 133 (6) ◽  
Author(s):  
Masayuki Kamaya
Keyword(s):  
Stress Intensity ◽  
Structural Reliability ◽  
Crack Depth ◽  
Crack Size ◽  
Multiple Cracks ◽  
J Integral ◽  
Surface Cracks ◽  
Linear Elastic ◽  
Offset Distance ◽  
Bending Load

When multiple cracks approach one another, the stress intensity factor and J-integral value change due to the interaction of the stress field. Since the changes in these parameters are not always conservative in structural reliability evaluations, the interaction between multiple cracks should be taken into account. Section XI of the ASME Boiler and Pressure Vessel Code provides a flaw characterization rule for interacting multiple cracks. In Section XI, adjacent cracks are replaced with a coalesced single crack when the distance between the cracks is less than half of the crack depth. However, the criterion for the offset distance is given as an absolute value, although the magnitude of the interaction depends on the crack size. In the current study, an alternative criterion for the offset distance was examined. Linear-elastic and elastic–plastic analyses were performed for interacting semicircular and semi-elliptical surface cracks by the finite element method under a tensile or bending load. The change in the stress intensity factors and J-integral values due to the relative spacing of cracks was investigated. Based on the relationship between the magnitude of the interaction and the relative position of the cracks, the allowable ctriterion for the offset distance was discussed.

Flaw Proximity Rules for Parallel Surface Cracks Based on Elastic, Elastic-Plastic Fracture Mechanics and Limit Load Analyses

2006 ◽  
Author(s):  
Masayuki Kamaya
Keyword(s):  
Structural Reliability ◽  
Limit Load ◽  
Crack Size ◽  
Multiple Cracks ◽  
Surface Cracks ◽  
Elastic Plastic ◽  
Linear Elastic ◽  
Offset Distance ◽  
Bending Load ◽  
Elastic Fracture

When multiple cracks approach one another, the stress intensity factor, J integral value of cracks and limit load of cracked component are likely to change due to the interaction of the stress field. Since the changes in these parameters are not always conservative in structural reliability evaluations, the interaction between multiple cracks must be taken into account. Section XI of the ASME Boiler and Pressure Vessel Code provides a flaw characterization rule for interacting multiple cracks. In Sec. XI, adjacent cracks are replaced by a coalesced single combined crack if they are located within the distance of half depth of deeper crack. However, the criterion for offset distance is given by an absolute value, although magnitude of the interaction is inevitably dependent on the crack size. In current study, an alternative criterion for the offset distance is examined. The linear-elastic fracture, elastic-plastic fracture and limit load analyses are performed for interacting semi-circular and semi-elliptical surface cracks by using the finite element method under a tensile and bending load. Based on the relationship between fracture strength and relative position of the two cracks, the allowable condition for the offset distance is discussed.

scholarly journals Probabilistic Elastic-plastic Fracture Mechanics Analysis of Propagation of Cracks in Pipes under Internal Pressure

2020 ◽  
Vol 14 (54) ◽  
pp. 202-210
Author(s):  
Belaïd Mechab ◽  
Medjahdi Malika ◽  
Mokadem Salem ◽  
Serier Boualem
Keyword(s):  
Distribution Function ◽  
Internal Pressure ◽  
Structural Reliability ◽  
Mechanical Response ◽  
Crack Depth ◽  
Three Dimensional ◽  
Crack Size ◽  
Elastic Plastic ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

This study presents a three dimensional finite element method analysis of semi-elliptical surface cracks in pipes under internal pressure load. In the elastic–plastic case, estimates of the J-integral are presented for various ratios including crack depth to pipe thickness (a/t) and strain hardening index in the (R-O) Ramberg-Osgood (n).  Finally, failure probability is accessed by a statistical analysis for uncertainties in loads and material properties, and structural reliability and crack size. The Monte Carlo method is used to predict the distribution function of the mechanical response. According to the obtained results, we note that the stress variation and the crack size are important factors influencing on the distribution function of (J/Je).

Elastic-Plastic Analysis of an Elbow With Axial Part-Through Internal Crack at Crown Under In-Plane Bending

2008 ◽  
Author(s):  
K. M. Prabhakaran ◽  
S. R. Bhate ◽  
V. Bhasin ◽  
A. K. Ghosh
Keyword(s):  
Finite Element ◽  
Crack Depth ◽  
Bending Moment ◽  
Internal Crack ◽  
J Integral ◽  
Finite Element Analyses ◽  
Integrity Assessment ◽  
Elastic Plastic ◽  
Axial Part ◽  
Plane Bending

Piping elbows under bending moment are vulnerable to cracking at crown. The structural integrity assessment requires evaluation of J-integral. The J-integral values for elbows with axial part-through internal crack at crown under in-plane bending moment are limited in open literature. This paper presents the J-integral results of a thick and thin, 90-degree, long radius elbow subjected to in-plane opening bending moment based on number of finite element analyses covering different crack configurations. The non-linear elastic-plastic finite element analyses were performed using WARP3D software. Both geometrical and material nonlinearity were considered in the study. The geometry considered were for Rm/t = 5, and 12 with ratio of crack depth to wall thickness, a/t = 0.15, 0.25, 0.5 and 0.75 and ratio of crack length to crack depth, 2c/a = 6, 8, 10 and 12.

Growth Behavior of Two Interacting Surface Cracks of Dissimilar Size (Comparison for Tensile and Bending Load)

2010 ◽  
Author(s):  
Masayuki Kamaya ◽  
Masanori Kikuchi ◽  
Eiichi Miyokawa
Keyword(s):  
Finite Element ◽  
Element Model ◽  
Growth Behavior ◽  
Multiple Cracks ◽  
Surface Cracks ◽  
Element Mesh ◽  
Loading Direction ◽  
Parallel Surface ◽  
Bending Load ◽  
The Difference

When multiple cracks approach one another, the stress intensity factor is likely to change due to the interaction of the stress field. This causes change in growth rate and shape of cracks. In particular, when cracks are in parallel position to the loading direction, the shape of cracks becomes non-planar. In this study, the complex growth of interacting cracks is evaluated by using the S-Version finite element method, in which local detailed finite element mesh (local mesh) is superposed on cores finite element model (global mesh) representing the global structure. In this study, two parallel surface cracks are subjected to two types of loading; tensile and bending load. Comparisons are made on the growth behavior under two types of loading. It is shown that the smaller crack stop growing due to the interaction when the difference in size of two cracks is large. This tendency is more significant for the bending load. The procedure for evaluating crack growth for Fitness-for-Service assessment is discussed.

Validation on the Relationship Between J Integral and CTOD for Offshore Structural Steel Weldments by Experimental and Numerical Analyses

2014 ◽  
Author(s):  
Dong Hyun Moon ◽  
Jeong Soo Lee ◽  
Jae Myung Lee ◽  
Myung Hyun Kim
Keyword(s):  
Plastic Deformation ◽  
Crack Tip ◽  
J Integral ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Constraint Factor ◽  
Element Analysis ◽  
Elastic Plastic ◽  
Plastic Constraint ◽  
The Relationship

Elastic plastic fracture mechanics (EPFM) is the domain of fracture analysis which considers extensive plastic deformation at crack tip prior to fracture. J integral and crack tip opening displacement (CTOD) have been commonly used as parameters for EPFM analysis. The relationship between these parameters has been extensively studied by industry and academia. The plastic constraint factor can serve as a parameter to characterize constraint effects in fracture involving plastic deformation. Therefore, the characteristics of plastic constraint factor are important in EPFM analysis. In this study, the relationship between J Integral and CTOD was investigated by conducting fracture toughness tests using single edge notched bend (SENB) specimens. Also, plastic constraint factor was investigated by using finite element analysis. Numerical analysis was carried out using ABAQUS elastic-plastic analysis mode.

Detection of Multiple Cracks in Triangular Cantilevers Based on Frequency Measurements

2006 ◽  
Vol 324-325 ◽  
pp. 259-262
Author(s):  
Fei Wang ◽  
Xue Zeng Zhao ◽  
Jia Ying Chen
Keyword(s):  
Damage Index ◽  
Maximum Error ◽  
Crack Size ◽  
Force Sensors ◽  
Multiple Cracks ◽  
Cantilever Deflection ◽  
Local Flexibility ◽  
Small Force ◽  
The Relationship ◽  
Number Of Segments

Triangular cantilevers are used as small force sensors. Prediction of location and size of multiple cracks from experimental results will be of value to users and designers of cantilever deflection force sensors. We extend a method for prediction of location and size of multiple cracks in rectangular cantilevers to deal with triangular cantilevers in this paper. The cracks are assumed to introduce local flexibility change and are modeled as rotational springs. The beam is divided into a number of segments, and each segment is associated with a damage index, which can be calculated through the relationship between the damage index and strain energy of each segment and the changes in the frequencies caused by the cracks. The location of cracks can be obtained with high accuracy with sufficient segment numbers. The size of a crack can be calculated through the relationship between the crack size and its stiffness, which can be obtained from the damage index related to the crack. The maximum error in prediction of the crack position in the case of double cracks is less than 15%, and it is less than 25% in prediction of the crack size.

Investigating the Interaction Behavior Between Two Arbitrarily Oriented Surface Cracks Using Multilevel Substructuring

2002 ◽  
Vol 124 (4) ◽  
pp. 440-445 ◽  
Author(s):  
Walied A. Moussa
Keyword(s):  
Crack Depth ◽  
Plate Thickness ◽  
Multiple Cracks ◽  
Surface Cracks ◽  
Intensity Factors ◽  
Release Rates ◽  
Element Analysis ◽  
Wide Range ◽  
Total Failure ◽  
Energy Release Rates

The existence of arbitrarily oriented multiple cracks is a common problem in brittle materials. Some of these materials, such as ceramics, are used in mechanical and aerospace structures that suffer from aging. Because of that, such structures have shown some signs of sudden partial or total failure. The interaction and coalescence of multiple cracks may significantly affect the designed lives of aging structures. Knowledge of the growth behavior of interacting cracks is still limited. In this paper, a novel submodeling meshing algorithm is used to construct different cases of arbitrarily oriented identical surface cracks in a plate subjected to remote tension. These cases are solved using finite element analysis (FEA) and covered a wide range of crack geometries. The stress intensity factors (SIFs) and the energy release rates (G) for these cracks are calculated as a function of their relative orientation and the position along the interaction crack-front. In this paper, the studied ratio of crack depth to plate thickness, a/t, and to crack length, a/c, are kept at 0.2 and 0.3, respectively. Where possible, a comparison of the 3-D results with 2-D ones is also considered.

Fully-Plastic J and CTOD Solutions for Pipes With Circumferential Surface Cracks Subjected to Combined Bending and Tension

2011 ◽  
Author(s):  
Lui´s F. S. Parise ◽  
Claudio Ruggieri
Keyword(s):  
Material Properties ◽  
Tensile Load ◽  
Estimation Procedure ◽  
Large Set ◽  
J Integral ◽  
Surface Cracks ◽  
Defect Assessment ◽  
Wide Range ◽  
Bending Load ◽  
Assessment Procedures

This work provides an estimation procedure to determine the J-integral and CTOD for pipes with circumferential surface cracks subjected to combined bending and tensile load for a wide range of crack geometries and material (hardening) based upon fully-plastic solutions. A summary of the methodology upon which J and CTOD are derived sets the necessary framework to determine nondimensional functions h1 and h2 applicable to a wide range of crack geometries and material properties characteristic of structural, pressure vessel and pipeline steels. The extensive nonlinear, 3-D numerical analyses provide a large set of solutions for J and CTOD which enters directly into fitness-for-service (FFS) analyses and defect assessment procedures of cracked pipes and cylinders subjected to bending load.

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