Micromechanics of Osteonal Cortical Bone Fracture

1998 ◽  
Vol 120 (1) ◽  
pp. 112-117 ◽  
Author(s):  
X. E. Guo ◽  
L. C. Liang ◽  
S. A. Goldstein
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Cortical Bone ◽  
Bone Tissue ◽  
Cement Line ◽  
Linear Elastic ◽  
Age Related ◽  
Microcrack Propagation

Microcracks have been associated with age-related bone tissue fragility and fractures. The objective of this study was to develop a simple osteonal cortical bone model and apply linear elastic fracture mechanics theory to understand the micromechanics of the fracture process in osteonal cortical bone and its dependence on material properties. The linear fracture mechanics of our composite model of conical bone, consisting of an osteon and interstitial bone tissue, was characterized in terms of a stress intensity factor (SIF) near the tip of a microcrack. The interaction between a microcrack and an osteon was studied for different types of osteons and various spacing between the crack and the osteon. The results of the analysis indicate that the fracture mechanics of osteonal cortical bone is dominated by the modulus ratio between the osteon and interstitial bone tissue: A soft osteon promotes microcrack propagation toward the osteon (and cement line) while a stiff one repels the microcrack from the osteon (and cement line). These findings suggest that newly formed, low-stiffness osteons may toughen cortical bone tissue by promoting crack propagation toward osteons. A relatively accurate empirical formula also was obtained to provide an easy estimation of the influence of osteons on the stress intensity factor.

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.

scholarly journals Impact of the Weld Geometry on the Stress Intensity Factor of the Welded T-Joint Exposed to the Tensile Force and the Bending Moment

2015 ◽  
Vol 11 (2) ◽  
pp. 103-109
Author(s):  
Jelena M. Djoković ◽  
Ružica R. Nikolić ◽  
Ján Bujňák
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Tensile Force ◽  
Bending Moment ◽  
Linear Elastic ◽  
Weld Geometry ◽  
Axial Tensile ◽  
The Impact

Abstract In this paper it is analyzed the welded T-joint exposed to the axial tensile force and the bending moment, for determining the impact of the weld geometry on the fracture mechanics parameters. The stress intensity factor was calculated analytically, based on the concept of the linear elastic fracture mechanics (LEFM), by application of the Mathematica® programming routine. The presence of the weld was taken into account through the corresponding correction factors. The results show that increase of the size of the triangular welds leads to decrease of the stress intensity factor, while the SIF increases with increase of the welds’ width. The ratio of the two welded plates’ thicknesses shows that plate thicknesses do not exhibit significant influence on the stress intensity factor behavior.

Assessment of Methods in Girth Welds of Steel Pipelines

2005 ◽  
Vol 473-474 ◽  
pp. 243-248 ◽  
Author(s):  
Gyula Nagy ◽  
János Lukács ◽  
Imre Török
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
The Other ◽  
Burst Test ◽  
Linear Elastic ◽  
Elastic Fracture ◽  
Material Discontinuities ◽  
Girth Welds

This paper presents two basic methods for the assessment of failed girth welds of steel hydrocarbon transporting pipelines. One of them is based on the principles of linear elastic fracture mechanics (LEFM) and stress intensity factor conception for planar material discontinuities, and the other can be used for the complex assessment of all kinds of occurring defects. The results of the presented methods are compared to the results of burst test of pipeline sections containing a failed girth weld and cut from a Hungarian gas pipeline.

VALIDITY OF THE DIRECT RELATION BETWEEN THE FRACTURE MECHANICS PARAMETERS, K AND G, IN THE CASE OF BONE

2004 ◽  
Vol 04 (03) ◽  
pp. 321-331 ◽  
Author(s):  
SATYA PRASAD PARUCHURU ◽  
KOGANTI MOHAN RAO ◽  
XIAODU WANG ◽  
C. M. AGRAWAL
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Sampling Site ◽  
Direct Relation ◽  
Linear Elastic

The critical values of stress intensity factor and energy release rate (KIc, GIc) are important fracture mechanics parameters used in the characterization of bone fracture, assessment of bone quality, and prosthesis design. There exists, a direct relationship between stress intensity factor, K and energy release rate, G that holds good for linear elastic, isotropic, and homogeneous materials. As bone is anisotropic and non-homogeneous, whether or not the relationship is still valid is an important factor. Bone is a brittle material and if it is tested for a particular crack orientation and at a particular sampling site, it may behave as a linear elastic, isotropic, and homogeneous material. The present work verifies the direct relation between K and G of bone in the case of tangential cracks.

The Application of Fracture Mechanics in Highway Tunnel Lining Cracking

2014 ◽  
Vol 580-583 ◽  
pp. 1377-1381
Author(s):  
Song Zhou Chen
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Stress Field ◽  
Tunnel Lining ◽  
Concrete Fracture ◽  
Linear Elastic ◽  
Highway Tunnel ◽  
Elastic Fracture

Lining cracks of highway tunnel has a very important effect on the healthy operation of the tunnel. Establishing the model for concrete fracture mechanics evaluation, we could identify the tunnel lining cracking situation. By using Linear elastic fracture mechanics method we could calculate the stress field of crack in the lining. Separately by different depth we have calculated crack stress intensity factor. We get that growing rates of variation of stress intensity factor as the crack depths increase. So lining tunnel health operations severely cracked.

Study on the Relationship Between Interaction Factors and Stress Intensity Factor for Elliptical Flaws

2017 ◽  
Author(s):  
Kisaburo Azuma ◽  
Yinsheng Li ◽  
Kunio Hasegawa
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Front ◽  
Elastic Solid ◽  
Element Analysis ◽  
Linear Elastic ◽  
Close Proximity ◽  
Interaction Factors ◽  
The Relationship

The interaction of multiple flaws in close proximity to one another may increase the stress intensity factor of the flaw in structures and components. This interaction effect is not distributed uniformly along the crack front. For instance, the strongest interaction is generally observed at the point closest to a neighboring flaw. For this reason, the closest point could show a higher value of the stress intensity factor than all other points in some cases, even if the original value at the point of the single flaw is relatively low. To clarify the condition when the closest point shows the maximum stress intensity factor, we investigated the interaction of two similar elliptical flaws in an infinite model subjected to remote tension loading. The stress intensity factor of the elliptical flaws was obtained by performing finite element analysis of a linear elastic solid. The results indicated that the interaction factors along the crack front can be expressed by a simple empirical formula. Finally, we show the relationship between geometrical features of the flaw and the stress intensity factor at the closest point to a neighboring flaw.

An Investigation of the Stress Intensity Factor Along a Corner Crack in Pressurizer Vent Nozzle Penetration Weld

2009 ◽  
Author(s):  
Sang-Min Lee ◽  
Jeong-Soon Park ◽  
Jin-Su Kim ◽  
Young-Hwan Choi ◽  
Hae-Dong Chung
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Plastic Zone ◽  
Structural Integrity ◽  
Operating Conditions ◽  
Corner Crack ◽  
Elastic Plastic ◽  
Material Fracture

Elastic-plastic fracture mechanics as well as linear-elastic fracture mechanics may be applied to evaluate a flaw in ferritic low alloy steel components for operating conditions when the material fracture resistance is controlled by upper shelf toughness behavior. In this paper, the distribution of the stress intensity factor along a corner crack using elastic-plastic fracture mechanics technique is investigated to assess the effect of a structural factor on mechanical loads in pressurizer vent nozzle penetration weld. For this purpose, the stress intensity factor and plastic zone correction of a corner crack are calculated under internal pressure, thermal stress and residual stress in accordance with Electric Power Research Institute (EPRI) equation and Irwin’s approach, respectively. The resulting stress intensity factor and plastic zone correction were compared with those obtained from Structural Integrity Associates (SIA) and Kinectrics, and were observed to be good agreement with Kinectrics results.

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.

Variation of Stress Intensity Factor and Crack Distance Length for Double Edge Crack in Human Femur Bone

2014 ◽  
Vol 695 ◽  
pp. 580-583
Author(s):  
Noor A. Md Zain ◽  
Ruslizam Daud ◽  
W.Z.A.W. Muhamad ◽  
Khairul Salleh Basaruddin ◽  
Yazid Bajuri ◽  
...  
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Parallel Edge ◽  
Linear Elastic ◽  
Femur Bone ◽  
Double Edge ◽  
Crack Tips ◽  
Elastic Fracture ◽  
Edge Cracks

The theory of linear elastic fracture mechanic (LEFM) has proven that we can evaluate the amount of stress located at the crack tip by determining the stress intensity factor (). The stress at the tip of a sharp crack has the highest stress which can lead to failure on the material. Thus, the cracks within human bones are quite complicated because of the bone microstructure. There are a few factors that can minimize the effect of the cracks so that patients can heal much faster. Hence, this paper focuses on how several crack distances, between two parallel edge cracks can affect the value of stress intensity factor (). Using the LEFM theory, the interaction between two neighboring crack tips was investigated.

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