• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 추계학술대회 논문집
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• pp.403-407
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• 2009

In this work, finite element investigations were carried out to manufacture a seamless aluminum liner without crack generation using four-stage deep drawing followed by two-stage ironing process. In order to predict the crack generation during the liner manufacturing process, the Normalize Cockroft-Latham(NCL) which is one of ductile fracture criteria was adopted. In addition, the tensile tests were carried out to obtain the critical value of NCL by comparing the experimental and FE simulation results. From this, various case studies based on FE simulation were carried to obtain the optimum die designs which can prevent the crack generation during ironing processes. Finally, the aluminum liner was successfully made using obtained die designs so that requirements were met in terms of thickness and height of the liner.

• 한국해양공학회지
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• 제6권1호
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• pp.113-121
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• 1992

In this study, the variation of fatigue strength in CF/PEEK and CF/EPOXY, the matrix and interfacial strength of which differ from each other, has been studied from the viewpoint of microfracture behavior. The results obtained are as follows; According as the fatigue strength moves from the lower cycle range to the higher cycle range, that of CF/PEEK shows higher curve than that of CF/EPOXY does. In the early stage of fatigue life, the characteristic of fatigue crack in CF/PEEK is mainly the fracture of longitudinal fiber, while that in CF/EPOXY is the fracture of transverse fiber. The difference of fatigue strength in these materials can be explained by the fracture criteria of transverse fiber and longitudinal fiber.

• 대한족부족관절학회지
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• 제10권1호
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• pp.84-87
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• 2006

Purpose: To review the results of surgical decompression for tarsal tunnel syndrome associated with calcaneus fractures. Materials and Methods: Six tarsal tunnel syndromes in five patients were surgically decompressed at our hospital with followed up of average 26.0 months (range, $12{\sim}36$ months). All patients were male and average age at surgery was 50.0 years (range, $33{\sim}69$years). All five cases developed after calcaneus fractures including one bilateral case. Clinical results were assessed according to the criteria of Pfeiffer and Cracchiolo. Results: The result was good in three cases, fair in one case and poor in two cases. Four cases in four patients were satisfied with the result of treatment. Conclusion: Clinical results of surgical treatment for tarsal tunnel syndrome associated with calcaneus fracture of the foot or ankle was improved and maintained in four of six cases.

• 대한두개안면성형외과학회지
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• 제16권3호
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• pp.136-142
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• 2015

Background: The incidence and etiology of facial bone fracture differ widely according to time and geographic setting. Because of this, prevention and management of facial bone fracture requires ongoing research. This study examines the relationship between socioeconomic status and the incidence of facial bone fractures in patients who had been admitted for facial bone fractures. Methods: A retrospective study was performed for all patients admitted for facial bone fracture at the National Medical Center (Seoul, Korea) from 2010 to 2014. We sought correlations amongst age, gender, fracture type, injury mechanism, alcohol consumption, and type of medical insurance. Results: Out of the 303 patients meeting inclusion criteria, 214 (70.6%) patients were enrolled in National Health Insurance (NHI), 46 (15.2%) patients had Medical Aid, and 43 (14.2%) patients were homeless. The main causes of facial bone fractures were accidental trauma (51.4%), physical altercation (23.1%), and traffic accident (14.2%). On Pearson's chi-square test, alcohol consumption was correlated significantly with accidental trauma (p<0.05). And, the ratio of alcohol consumption leading to facial bone fractures differed significantly in the homeless group compared to the NHI group and the Medical Aid group (p<0.05). Conclusion: We found a significant inverse correlation between economic status and the incidence of facial bone fractures caused by alcohol consumption. Our findings indicate that more elaborate guidelines and prevention programs are needed for socioeconomically marginalized populations.

• 대한토목학회논문집
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• 제7권1호
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• pp.75-82
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• 1987

본(本) 연구(硏究)는 소규모강복범위(小規模降伏範圍)를 벗어나는 대규모강복조건하(大規模降伏條件下)에서 구조안정성(構造安定性)에 관(關)한 중요(重要)한 문제(問題)인 불안정연성파괴(不安定延性破壞)를 평가(評價)할 수 있는 파괴역학인자(破壞力學因子)로서의 J 적분(積分)을 수치해(數値解)로서 구하는데 그 목적(目的)을 두었다. 이를 위해 균열재(龜裂材)의 균열선단요소(龜裂先端要素)로 8절점등방특이요소(節點等方特異要素)를 사용(使用)하고, 균열발생(發生)은 파괴인성(破壞靭性) $J_{IC}$를 초과할 때 일어나도록 하였으며, 그리고 균열성장(成長)의 취급(取級)은 균열개구각(龜裂開口角)을 이용(利用)했다. 본(本) 연구(硏究)에 의해 해석(解析)된 J 적분치(積分値)를 사용(使用)하여 균열재의 균열발생 과 안정성장(安定成長), 불안정(不安定) 발생점(發生點)을 찾은 결과(結果) 다른 연구결과(硏究結果)와 잘 일치(一致)하고 있어 탄소성(彈塑性)을 고려(考慮)한 J 적분치(積分値)가 균열의 안정성장(安定成長) 및 불안정연성파괴(不安定延性破壞) 문제(問題)를 다루는 파괴역학인자(破壞力學因子)로서 직접(直接) 이용(利用)될 수 있음을 보였다.

• Journal of Korean Neurosurgical Society
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• 제41권1호
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• pp.7-10
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• 2007

Objective : The aim of this study was to determine the efficacy of percutaneous radiofrequency neurotomy[RFN] of ramus communicans nerve in patients suffering from severe low back pain due to osteoporotic compression fracture. Methods : Twenty two patients with lumbar osteoporotic compression fracture who had intractable back pain for less than two weeks and were performed with RFN at L1-L4 from May 2004 to December 2005 were retrospectively analyzed. Clinical outcome using visual analogue scale[VAS] pain scores and modified MacNab's grade was tabulated. Complications related to the procedure were assessed. Results : Twenty-two female patients [age from 63 to 81 years old] were included in this study. The mean VAS score prior to RFN was 7.8, it improved to 2.6 within postoperative time of 48 hours, and the mean VAS score after 3 months was 2.8, which was significantly decreased. Eighteen of 22 patients were graded as excellent and good according to modified MacNab's criteria at final follow up. All patients recovered uneventfully, and the neurologic examination revealed no deficits. Two patients showing poor results worsened in symptom. Percutaneous was performed eventually resulting in symptom improvement. There were no significant complications related to the procedure such as sensory dysesthesia, numbness or permanent motor weakness. Conclusion : RFN is safe and effective in treating the painful osteoporotic compression fracture. in patients with intractable back pain due to lumbar osteoporotic compression fracture, RFN of gray ramus communicans nerve should be considered as a treatment option prior to vertebroplasty.

• 한국압력기기공학회 논문집
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• 제12권2호
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• pp.1-24
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• 2016

The original fracture criteria developed by Maxey/Kiefner for axial through-wall and surface-cracked pipes have worked well for many industries for a large variety of relatively low strength and toughness materials. However, newer line pipe steels have some unusual characteristics that differ from these older materials. One example is a test data that has demonstrated that X80 line-pipe with an axial through-wall-crack can fail at pressures about 30 percent lower than predicted with commonly used analysis methods for older steels. Thus, it is essential to review the currently available models and investigate the applicability of these models to newer high-strength line pipe materials. In this paper, the available models for predicting the failure behavior of axial-cracked pipes (through-wall-cracked and external surface-cracked pipes) were reviewed. Furthermore, the applicability of these models to high-strength steel pipes was investigated by analyzing limited full-scale pipe fracture initiation test results. Based on the analyzed results, the shortcomings of the available models were identified. For both through-wall and surface cracks, the major shortcomings were related to the characterization of the material toughness, which generally leads to non-conservative predictions in the J-T analyses. The findings in this paper may be limited to the test data that were consider for this study. The requisite characteristics of a potential model were also identified in the present paper.

• 한국공작기계학회논문집
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• 제18권2호
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• pp.170-177
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• 2009

The objective of this study is to evaluate an acoustic emission (AE) source characterization and fracture behavior of the SM45C steel by using back-propagation neural network (BPN). In previous research Ref. [8] about k-nearest neighbor classifier (k-NNC) continuity, we used K-means clustering method as an unsupervised learning method for obtaining multi-variate AE main data sets, such as AE counts, energy, amplitude, risetime, duration and counts to peak. Similarly, we applied k-NNC and BPN as a supervised learning method for obtaining multi-variate AE working data sets. According to the error of convergence for determinant criterion Wilk's ${\lambda}$, heuristic criteria D&B(Rij) and Tou values are discussed. As a result, in k-NNC before fracture signal is detected or when fracture signal is detected, showed that produce some empty classes in BPN. And we confirmed that could save trouble in AE signal processing if suitable error of convergence or acceptable encoding error give to BPN.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2000년도 추계학술발표대회 논문집
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• pp.102-105
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• 2000

Recently, applications of integrated large composite structures have been attempted to many structures of vehicles. To improve the cost performance and reliability of the integrated composite structures, it is necessary to judge structural integrity of the composite structures. For the judgement, we need fracture simulation techniques for composite structures. Many researches oil the fracture simulation method using FEM have been reported by now. Most of the researches carried out simulations considering only matrix cracking and fiber breaking as fracture modes, and did not consider delamination. Several papers have reported the delamination simulation, but all these reports require three-dimensional elements or quasi three- dimensional elements for FEM analysis. Among fracture mechanisms of composite laminates, delamination is the most important factor because it causes stiffness degradation in composite structures. It is known that onset and propagation of delamination are dominated by the strain energy release rate and interfacial moment. In this study, laminated composite has been described by using 3 dimensional finite elements. Then impact behavior of the laminated composite is simulated using FEM(ABAQUS/Explicit) with progressive failure mechanism. These results are compared with experimental results.

• 대한기계학회논문집A
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• 제30권9호
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• pp.1086-1093
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• 2006

A local failure criterion for the API X65 steel is applied to predict ductile failure of full-scale API X65 pipes with simulated corrosion and gouge defects under internal pressure. The local failure criterion is the stress-modified fracture strain for the API X65 steel as a function of the stress triaxiality (defined by the ratio of the hydrostatic stress to the effective stress). Based on detailed FE analyses with the proposed local failure criteria, burst pressures of defective pipes are estimated and compared with experimental data. The predicted burst pressures are in good agreement with experimental data. Noting that an assessment equation against the gouge defect is not yet available, parametric study is performed, from which a simple equation is proposed to predict burst pressure fur API X65 pipes with gouge defects.