• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.2
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• pp.313-330
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• 1993

The propagating crack problems under dynamic plane mode in orthotropic material is studied in this paper. To analyze the dynamic fracture problems in orthortropic material, it is important to know the dynamic stress components and dynamic displacement components around the crack tip. Therefore the dynamic stress components of dynamic stress field and dynamic displacement components of dynamic displacement field in the crack tip of orthotropic material under the dynamic load and the steady state in crack propagation were derived. When the crack propagation speed approachs to zero, the dynamic stress component and dynamic displacement components derived in this study are identical to the those of static state. In addition, the relationships between dynamic stress intensity factor and dynamic energy release rate are determinded by using the concept of crack closure closure energy with the dynamic stresses and represented according to physical properties of the orthotrophic material and crack speeds. The faster the crack velocity, the greater the stress value of stress components in crack tip. The stress value of the stress component of crack tip is greater when fiber direction coincides with the crack propagation than when fider direction is normal to the crack propagation.

• Journal of Chest Surgery
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• v.24 no.1
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• pp.8-14
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• 1991

Methods for the operative management of patent ductus arteriosus are now well established, and in the vast majority of children the circulatory shunt can be safely and effectively abolished by dividing the ductus or by closing it in continuity with ligatures and transfixing sutures. In adults, however, closure of patent ductus arteriosus may pose important technical problems, particularly when there are associated pulmonary hypertension, calcification, aneurysm and infective endocarditis. Under these circumstance, division or ligation is unusually hazardous because the diseased vessels often fracture or tear when sutures are placed in them. Then we closed the patent ductus arteriosus by use of cardiopulmonary bypass in 18 patients and ligated the ductus via thoracotomy in 18 patients from Jan. 1986 to May 1990. And we compared the results between two different methods. We concluded that ligation of ductus had a problem of rupture and transpulmonary internal suture closure of PDA had a problem of injury of recurrent laryngeal nerve.

• Journal of the Society of Naval Architects of Korea
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• v.38 no.3
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• pp.84-92
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• 2001

The development of a crack propagation simulation model in consideration of crack closure behavior was discussed in the accompanying paper by the authors, Kim et al(2001). To verify crack propagation behavior under variable amplitude loading based on the model, calculations of effective crack driving stresses and corresponding propagation lives are carried out for load spectrums with various stress ratios, overload and underload. Good agreement is confirmed between test results in the literatures and simulations using the developed model.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.6
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• pp.867-876
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• 1987

Corrosion fatigue fracture with change in the grain size of M.E.F. dual phase steel is investigated in 3.5% NaCI aqueous solution at pH 2, 4, 6, 9, and 11. Generally speaking, decrease in corrosion fatigue life is strongly dependent on decrease in pH and slightly on the grain size. For the B material with the big grain size, the fatigue life is small due to its large reduction ratio of corrosion fatigue life. The influence of grain size on the reduction ratio of corrosion fatigue life is large at pH 11-6. Whi9le at pH 4-2 the reduction ratio of corrosion fatigue life only depends on the corrosion effect. The larger grain size and the lass pH result in the greater influence on corrosion fatigue crack propagation rate. As pH decreases, the plateau portion in the crack propagation rate curves of the B material are distinct. Crack propagation rate curves become slow down at high .DELTA.K range because crack closure effect by minute corrosion products inside crack causes the oxidation corrosion action less effective for a certain period of time. In A material with small grain size, fatigue life is increased in proportion with increase of martensite intergranular which brings forth restraining the crack propagation decreases crack propagation rate. Corrosion pit which is created in the surface of specimen is found at pH 6,4 and 2 which is noticeable and the unevenness of the surface of the specimen becomes severe as pH decreases. The unevenness of corrosion fatigue fracture surface is severe as the effect of pH increases i.e. as pH decreases. In proportion with increase in the grain size and decrease in pH, the aspect of brittle fracture becomes evident.

• Journal of Trauma and Injury
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• v.33 no.1
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• pp.18-22
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• 2020

Purpose: Damage control laparotomy has contributed to improved survival rates for severe abdominal injuries. A large part of severe abdominal injury occurs with a concomitant pelvic bone fracture. The safety and effectiveness of internal fixation of pelvic bone fracture(s) has not been established. The aim of the present study was to evaluate infection risk in the pelvic surgical site in patients who underwent emergent abdominal surgery. Methods: This single-center retrospective observational study was based on data collected from a prospectively maintained registry between January 2015 and June 2019. Patients who underwent laparotomy and pelvic internal fixation were included. Individuals <18 and ≥80 years of age, those with no microbiological investigations, and those who underwent one-stage abdominal surgery were excluded. Comprehensive statistical comparative analysis was not performed due to the small number of enrolled patients. Results: A total of six patients met the inclusion criteria, and the most common injury mechanism was anterior-posterior compression (67%). The average duration of open abdomen was 98 hours (range, 44-98), and the time interval between abdominal closure and pelvic surgery was 98 hours. One patient (16.7%) died due to multi-organ dysfunction syndrome. Micro-organisms were identified in the abdominal surgical site in five patients (83%), with no micro-organisms in pelvic surgical sites. There was no unplanned implant removal. Conclusions: Internal fixation of pelvic bone fracture(s) could be performed in the state of open abdomen, and the advantages of early fixation may countervail the risks for cross contamination.

• Journal of Power System Engineering
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• v.4 no.4
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• pp.41-47
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• 2000

Fatigue crack propagation rate and threshold characteristics of the SA516/70 steel which is used for the low temperature pressure vessels, were studied in the room temperature of $25^{\circ}C$ and low temperature ranges of $-10^{\circ}C,\;-30^{\circ}C,\;-60^{\circ}C\;and\;-80^{\circ}C$ with stress ratio of R=0.1. In the logarithmic relationship between the fatigue crack propagation rate($d{\alpha}/dN$) and stress intensity factor range ${\Delta}K$, the linear relationship was obtained up to $d{\alpha}/dN=4.425{\times}10^4mm/cycle$ in the same of room temperature, but in low temperature case, the relationship was extended to the range of low crack propagation rate. The fractured specimens were examined by SEM. Tested results showed that specimen failed at low temperature exhibit the quasi-cleavage fracture formation however considerable ductility proceed final fracture.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.4
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• pp.174-181
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• 2005

In order to investigate the behavior of fatigue crack growth of SiC-particulate- reinforced Al-Si alloy composites, fatigue tests using single edge notched tension(SENT) specimens were performed. Composite materials were manufactured by using both permanent die casting and extrusion processes with different volume fractions of $10\%\;and\;20\%$. $SiC_p-reinfurced$ Al-Si composites showed the increased levels of threshold stress intensity factor range, ${\Delta}K_{th}$, for the increased volume fractions of SiC particles, which implies the increased fatigue crack growth resistance at the threshold or low ${\Delta}K$ levels, compared to the unreinforced Al-Si alloy. In the Paris region, however, the composites showed the increased rate of crack growth resulting in the unfavorable effects on the fatigue crack growth resistance. Critical stress intensity factor range at unstable crack growth leading to final fracture decreased as the volume fraction of SiC particle increased, because of the reduced fracture toughness of the composites. Extruded materials showed higher threshold and critical values than the cast materials.

• Journal of Korean Foot and Ankle Society
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• v.1 no.1
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• pp.51-58
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• 1997

The purpose of this study is to evalute the efficacy af the Ilizarov external fixation for the surgical treatment. of the tibial plafond fractures. We reviewed retrospectively fourteen cases of tibial plafond fractures with moderate to severe soft. tissue damage, which were fixed with Ilizarov external fixator. Using the AO Muler classification, there were four Type C1 fractures, six Type C2 and four Type C3. In most, of the cases, the ankles were operated on with other associated fractures within a few days after injury. We reduced the fracture indirectly by soft issue taxis and fixed externally across the ankle joint. using the circular external fixator with tensioned wires and ankle hinge. In cases of inadequate closed reduction, we applied limited open reduction and internal fixation. Range of motion exercise began immediately. Postoperative follow-up averaged fourteen months (ranges, 8-30 months). Overall clinical results rated good or excellent in 7 cases, fair in 4 and poor in 3. There were three cases of pin tract infection which were resolved with short-term antibiotics and local care; one delayed wound closure in a patient. whose fracture was associated with Type III open wound; one wound slough in a patient associated with Type II open wound, which was closed later by skin graft; and one osteoarthritis. From this review, we concluded that cross-ankle circular external fixation with tensioned wires with or without. limited open reduction is a reasonable alternative for the treatment of the tibial plafond fractures with severe soft tissue damage.

• Tunnel and Underground Space
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• v.21 no.2
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• pp.117-127
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• 2011

The purpose of this study is to demonstrate the effect of in-situ rock stresses on the deformability and permeability of fractured rocks. Geological data were taken from the site investigation at Forsmark, Sweden, conducted by Swedish Nuclear Fuel and Waste Man-agement Company (SKB). A set of numerical experiments was conducted to determine the equivalent mechanical properties (essentially, elastic moduli and Poisson's ratio) and permeability, using a Discrete Fracture Network-Discrete Element Method (DFN-DEM) approach. The results show that both mechanical properties and permeability are highly dependent on stress because of the hyperbolic nature of the stiffness of fractures, different closure behavior of fractures, and change of fluid pathways caused by deformation. This study shows that proper characterization and consideration of in-situ stress are important not only for boundary conditions of a selected site but also for the understanding of the mechanical and hydraulic behavior of fractured rocks.

• Archives of Craniofacial Surgery
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• v.13 no.1
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• pp.22-28
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• 2012

Purpose: In accordance to an increased interest in facial appearance and the popularization of computed tomography scanning, the number of diagnosis and treatment of blowout fractures has been increased. The purpose of this article is to review pure blowout fracture surgery through transconjunctival incision focusing on complications and their management. Methods: In this retrospective study, 583 patients, who had been treated for pure blowout fracture through transconjunctival incision from 2000 to 2009, were evaluated. Their hospital records were reviewed according to their sex, age, fracture site, preoperative presentations, time interval between trauma and surgery, and postoperative complications. Results: According to postoperative follow-up results, there were early complications that included wound dehiscence and infection (0.2%), hematoma (insomuch as extraocular movement is limited) (0.7%), lacriminal duct injury (0.5%), and periorbital nerve injury (0.7%). In addition, there were late complications that lasted more than 6 months, that included persistent diplopia (1.7%), extraocular movement limitation (0.9%), enophthalmos (1.0%), periorbital sensation abnormalities (1.0%), and entropion (0.5%). Conclusion: We propose the following guidelines for prevention of postoperative complications: layer by layer closure; bleeding control with the epinephrine gauzes, Tachocomb, and Tisseel; conjunctival incision 2 to 3 mm away from punctum; avoidance of excessive traction; performing surgical decompression and high dose corticosteroid therapy upon confirmation of nerve injury; atraumatic dissection and insertion of Medpor Barrier implant after securing a clear view of posterior ledge; using Medpor block stacking technique and BioSorb FX screw fixation; performing a complete resection of the anterior ethmoidal nerve during medial wall dissection; and making an incision 2 to 3 mm below the tarsal plate.