• Journal of the Korean Ceramic Society
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• v.31 no.5
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• pp.543-551
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• 1994

The creep behavior and creep fracture of sintered alumina at high temperature were investigated under four point flexural test. Steady-state creep behavior was observed at low bending stress and primary creep until fracture was observed at hish bending stress. The loading history of bending stress did not affect on steady-state creep rate. Intergranular fracture was dominant for fracture of alumina at room and high temperature. However, transgranular fracture was dominant on creep of alumina under high temperature by nucleation and growth of microcracks due to residual flaws or cavities in the material.

• Journal of Ocean Engineering and Technology
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• v.29 no.6
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• pp.454-462
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• 2015

An extended study was conducted on the fracture criterion by Choung et al. (2011; 2012) and Choung and Nam (2013), and the results are presented in two parts. The theoretical background of the fracture and the results of new experimental studies were reported in Part I, and three-dimensional fracture surface formulations and verifications are reported in Part II. How the corrected true stress can be processed from the extrapolated true stress is first introduced. Numerical simulations using the corrected true stress were conducted for pure shear, shear-tension, and pure compression tests. The numerical results perfectly coincided with test results, except for the pure shear simulations, where volume locking appeared to prevent a load reduction. The average stress triaxialities, average normalized lode parameters, and equivalent plastic strain at fracture initiation were extracted from numerical simulations to formulate a new three-dimensional fracture strain surface. A series of extra tests with asymmetric notch specimens was performed to check the validity of the newly developed fracture strain surface. Then, a new user-subroutine was developed to calculate and transfer the two fracture parameters to commercial finite element code. Simulation results based on the user-subroutine were in good agreement with the test results.

• Archives of Reconstructive Microsurgery
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• v.10 no.1
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• pp.18-22
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• 2001

Purpose : The purpose of this study was to evaluate stress fracture of vascularized fibular grafts(VFG) by analyzing factors associated with stress fracture and the treatment results. Materials and Methods : From June 1985 to May 1998, 7 patients with stress fractures in the 38 patients with long bone defect who had vascularized fibular graft were evaluated with clinical and radiologic methods including grafted fibular length and hypertrophic index of de Boer. The average age of the patients was 35 years(range, $14{\sim}60$ years). The mean follow-up period was 20 months(range, $16{\sim}32$ months). Results: 7(18.4%) stress fractures occurred in 38 patients. Characteristics of the fractures were (1) all occurred at lower extremity of male patients treated with VFG for long bone defected caused by infected nonunion; (2) all occurred 10 months at the average(range, $4{\sim}17$ months) after VFG; and (3) the length and hypertrophic index of grafted fibula had no influence on the incidence of stress fracture. Union was obtained in 3 patients by conservative treatment. 4 patients obtained union by internal fixation; one at immediately onset of fracture; and three after failure of conservative treatment who had fracture around the knee joint. Conclusion : Stress fracture may occur during the first one year after vascularized fibular graft and more attention must be paid for prevention of it, especially in the cases of infected nonunion. Stress fracture around the knee joint was expected to lead to a good result of early union by operative treatment.

• The Korean Journal of Nuclear Medicine
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• v.21 no.1
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• pp.39-46
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• 1987

The stress fracture is a disease caused by and abnormal stress to the normal bone with constant, repeated pull. Early detection of stress fracture plays an important role in treatment and prevention of its complication. Bone scintigraphy was performed to evaluate 18 patients with stress fracture of the lower extremities from May, 1985 to April, 1987, in the Department of Internal Medicine of National Police Hospital. The results were as follows: 1) Seventeen of the 18 cases showed positive bone scans at the initial study performed from 1 week to S months after the onset of symtom. 2) Ten of the 18 patients had findings of stress fracture at the initial X-ray film. Two out of 8 negative case revealed positive findings in the follow-up studies. 3) The bone scans in the 2 cases taken 5 months after the onset of symton; the one showed only slightly increased radiouptake, the other showed no abnormal findings. In conclusion, bone scanning is a more sensitive indicator of early stress fracture than radiologic study. The healing phase is characterized by a gradual decline in radioactivity at the fracture site in concordance with subsidence of symptom.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1-6
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• 2004

In this study, the intrinsic static/dynamic fracture toughness of Al 7175=T74 is evaluated from the apparent static/ dynamic toughness of notched specimen, The critical average stress fracture model is suggested to establish the relationship to predict the intrinsic fracture toughness from the apparent fracture toughness of a notched specimen. The critical average stress fracture model is established using the relation between the notch root radius and the effective distance calculated by finite element analysis. Also, effective distance is applied to estimate the failure criterion for the combustion pipe with notch. It is conclude that the true fracture toughness can be estimated from test results of apparent fracture toughness measured by using a notched specimen. Also, the effective In this study, the intrinsic static/dynamic fracture toughness of Al 7175=T74 is evaluated from the apparent static/ dynamic toughness of notched specimen, The critical average stress fracture model is suggested to establish the relationship to predict the intrinsic fracture toughness from the apparent fracture toughness of a notched specimen. The critical average stress fracture model is established using the relation between the notch root radius and the effective distance calculated by finite element analysis. Also, effective distance is applied to estimate the failure criterion for the combustion pipe with notch. It is conclude that the true fracture toughness can be estimated from test results of apparent fracture toughness measured by using a notched specimen. Also, the effective distance can be used to evaluate the failure criterion of structure with notch.

• Structural Engineering and Mechanics
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• v.26 no.1
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• pp.87-97
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• 2007

Some mixed mode fracture criterion may be converted in to elliptical or ellipsoidal formula with the aid of mathematical translation. Hence, the crack initiation in mixed mode fracture I+II emanating from notches, has been studied using notched circular ring specimens. On the basis of Irwin (1957) theory, a new criteria in mixed mode fracture I+II, based fracture elliptic criterion and notch stress intensity factors has been developed.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1518-1520
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• 2008

Recent clinical studies have shown that computer navigation for total knee arthroplasty (TKA) provides improved component alignment accuracy. However, femoral stress fracture after computernavigated TKA have been reported due to the pin hole and we hypothesized that osteoporosis would be one of the key factors in pin hole fracture after computer-navigated TKA. We investigated the von-Mises stress around the femoral pin-hole for different elastic modulli and ultimate stresses and four different pin penetration modes to understand the aging effect on femoral stress fracture risk after computer-navigated TKA by finite element analysis. In this study, aging effect was shown to increase the femoral stress fracture risk for all pin penetration modes. Especially, aging effect was shown dramatically in the transcortical pin penetration mode.

• Journal of The Korean Society of Integrative Medicine
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• v.7 no.4
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• pp.213-222
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• 2019

Purpose : The purpose of this study was to compare stress and psychological status between a stroke and a fracture patient's caregivers. Methods : Data was collected from September to December 2018 and participants of this study were 60 stroke and 61 fracture patient's caregivers. Stress was evaluated with the Global Assessment of Recent Stress scale-Korean Version and psychological status was measured with the Symptom check List-90-Revision. Results : The stroke patient's caregivers scored significantly higher than the fracture patient's caregivers in stress relevant to interpersonal, change in relationship, sickness or injury, financial, change/no change in routine (p<.05). The stroke patient's caregivers scored significantly higher in somatization, interpersonal sensitivity, depression, anxiety, paranoid ideation, and psychoticism than the fracture patient's caregivers (p<.05). Conclusion : It was found that the severity of mental health in the stroke patient's caregivers is necessary to develop a customized mental health improvement program for stroke patient's caregivers.

• Journal of the Korean Institute of Gas
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• v.25 no.1
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• pp.20-29
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• 2021

During multi-stage fracturing in a low permeable shale formation, stress interference occurs between the stages which is called the "stress shadow effect(SSE)". The effect may alter the fracture propagation direction and induce ununiform geometry. In this study, the stress shadow effect on the hydraulic fracture geometry and the well productivity were investigated by the commercial full-3D fracture model, GOHFER. In a homogeneous reservoir model, a multi-stage fracturing process was performed with or without the SSE. In addition, the fracturing was performed on two shale reservoirs with different geomechanical properties(Young's modulus and Poisson's ratio) to analyze the stress shadow effect. In the simulation results, the stress change caused by the fracture created in the previous stage switched the maximum/minimum horizontal stress and the lower productivity L-direction fracture was more dominating over the T-direction fracture. Since the Marcellus shale is more brittle than more dominating over the T-direction fracture. Since the Marcellus shale is more brittle than the relatively ductile Eagle Ford shale, the fracture width in the former was developed thicker, resulting in the larger fracture volume. And the Marcellus shale's Young's modulus is low, the stress effect is less significant than the Eagle Ford shale in the stage 2. The stress shadow effect strongly depends on not only the spacing between fractures but also the geomechanical properties. Therefore, the stress shadow effect needs to be taken into account for more accurate analysis of the fracture geometry and for more reliable prediction of the well productivity.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.6 s.177
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• pp.1547-1556
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• 2000

In this paper, an evaluation method of fracture toughness to apply interfacial fracture mechanics was investigated in adhesively bonded double-cantilever beam (DCB) joints. Four types of adhesively bonded DCB joints with an interface crack were prepared for analyses of the stress intensity factors using boundary element method(BEM) and the fracture toughness test. From the results of BEM analysis and fracture toughness experiments, it is found that the stress intensity factor, K1 is a parameter driving the fracture of adhesively bonded joints. Also, the evaluation method of fracture toughness by separated stress intensity factors of mixed mode cracks was proposed and the influences of mode components for its fracture toughness are investigated in adhesively bonded DCB joints.