• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 춘계학술대회 논문집
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• pp.159-162
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• 2005

The milli-components for electronic and medical device etc. have been manufactured by conventional process. Forming and machining process for those milli-components need tremendous cost and time because products require higher dimensional accuracy than the conventional ones. For instance, conventional mechanical punching process has many drawbacks for applying to high accuracy products. The final radius of hole can be varied and burr which interrupting another procedure is generated. Hydro-mechanical punching process makes possible to reduce amount of burr and obtain the fine shearing surface using the operating fluid. Hydrostatic pressure retards occurrence of initial crack and induces to locate the fracture surface in the middle of sheet to thickness direction. In this paper, Hydro-mechanical punching process is analyzed using finite element method and the effect of hydrostatic pressure is evaluated during punching process. The prediction of fracture is performed adopting the various ductile fracture criteria such as Cockcroft, Brozzo and Oyane's criterion using a user subroutine in ABAQUS explicit.

• Coupled systems mechanics
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• 제12권2호
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• pp.183-197
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• 2023

Scarce research has been published on crack propagation fracture of flywheels manufactured with carbon fiber-reinforced polymers. The present work deals with a calculation method to determine the conditions for which a crack propagates in the axial direction of the flywheel. The assumptions are: flywheels made with just a single thick ply or ply clustering laminates, oriented following the hoop direction; a single crack is analyzed in the plane defined by the hoop and axial directions; the crack starts close to one of the free edges; its axial length is initially large enough so that its tip is far away from that free edge, and the crack expands the entire circumferential perimeter and keeps its concentric position. The developed method provides information for a good design of flywheels. It is concluded that a fracture-based crack propagation criterion generally occurs at a lower speed than a stress-based criterion. Also, that the evolution of failure with thickness using the fracture criterion is exponential, demonstrating that thin flywheels are relatively not sensitive to crack propagation, whereas thick ones are very prone.

• 한국가스학회지
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• 제18권3호
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• pp.13-19
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• 2014

이산화탄소 포집 및 저장 시스템(CCS, Carbon dioxide Capture and Storage system)의 수송배관에 대한 연속연성파괴(DDF, Dynamic Ductile Fracture)를 연구하기 위하여 Battlle Two Curve법(BTCM)으로 CCS수송배관의 연속연성파괴거동을 해석하여 천연가스 수송배관의 연속연성파괴거동과 비교하였다. 또한, $CO_2$배관에서의 배관두께 및 사용온도에 따른 연속연성파괴 민감도를 분석함으로써 연속연성파괴에 대한 사용기준을 해석하였다. 우리나라 기후조건에 따른 $CO_2$배관두께와 수송압력 사용기준을 분석하였으며, 상온의 경우에는 기존의 천연가스용 배관을 $CO_2$배관으로 사용하기 위해서는 배관두께가 7mm이상이어야 하고 수송압력은 54bar이하이어야 함을 해석하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 추계학술대회논문집
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• pp.291-295
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• 2003

The occurrence of ductile fracture is the working limit of many metal forming processes. It is necessary to predict the criteria and to apply the condition in a process design. Over the years. the way for clarifying conditions have been studied and presented. However such a way needs lots of experiments and analysis. In this study, in order to determine the critical damage value of a used material Cu 4N, it was performed a tensile test and FEM analysis by using DEFORM 2D. For applying the obtained critical damage value it was also performed a upsetting test by using DEFORM 2D. The way of determining a critical damage value which is presented in this study will make possible to find easily it which is one of the working limit factor. And the way of determining a critical damage value will make possible to find in multi-pass drawing process.

• 대한기계학회논문집
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• 제14권5호
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• pp.1181-1185
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• 1990

본 연구에서는 정적파괴는 피로균열 진전의 최종과정에서 생기는 경우가 많다. 따라서 정적파괴의 경우의 파괴평가선도 및 피로파괴의 경우의 파괴평가선도가 얻어지 면 실제의 사용에 대해서 대단히 유용하다. 이와같은 관점에서 피로파괴에 대한 파 괴평가선도와 데이터베이스(data base)의 구축을 검토해 보고자 한다.

• 대한정형외과스포츠의학회지
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• 제5권1호
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• pp.63-68
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• 2006

목적: 전위성 쇄골 간부 골절의 치료로 관혈적 정복술 후 LCP를 사용하여 내고정을 시행한 환자를 대상으로 방사선학적, 임상적 결과를 분석하여 전위성 쇄골 간부 골절의 치료에 있어서 LCP의 유용성을 알아보고자 하였다. 대상 및 방법: 2003년 5월부터 2004년 11월까지 본원에서 쇄골 간부 골절에 대해 LCP를 이용한 관혈적 정복, 금속내 고정술을 시행하고 6개월 이상 추시가 가능하였던 26례를 대상으로 하였다. 수술 후 최종 평가는 방사선 결과와 fang s criteria를 이용한 임상적 결과로 분석하였다. 결과: 수술 후 평균 9.3주에 모든 예에서 지연유합 없이 골유합 되었으며 임상적으로 Kangs criteria에 따라 구분한 결과, 우수 이 상이 22례로 나타났다. 특히, 견관절 운동은 상완골 골절이 동반된 두 경우를 제외한 24례에서 2.9주내에 정상 범위로 빠른 회복을 보였다. 합병증으로는 견관절 운동 장애 2례, 수술 절개 부위의 켈로이드 형성 1례였으며 그 이외에 다른 주요 합병증은 없었다. 결론: 전위성 쇄골 간부 골절에서 LCP를 이용한 관혈적 정복 및 금속내 고정술은 기존의 금속판에 비해 수술 후 합병증을 줄이고 효과적인 골유합과 조기 견관절 운동에 도움을 줄 수 있는 좋은 치료 방법 중 하나라고 사료된다.

• Journal of Yeungnam Medical Science
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• 제4권2호
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• pp.131-138
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• 1987

1. 총 8예중 남자 6례, 여자 2례이었다. 2. 손상의 원인은 낙상이 4례로 가장 많았다. 3. Bado 분류에 의한 빈도는 I형이 4례(50%), II형 1예(12.5%), III형 3예(37.5%)이었다. 4. 척골골절의 위치는 상 1/3 이상 부위가 7예이었다. 5. 요골두 탈구 방향은 전방이 3예로가장 많았다. 6. 치료는 소아는 2예 모두 비수술적 방법으로 하였으며 성인 6예중 2예는 도수정복하고 4례는 골골절윤 압박금속판을 사용하여 내고정하였으며 골두 탈구는 모두 도수정복하였다. 7. 결과는 Bruce 등에 의한 판정으로 excellent 3예, good 2례, fair 1예, poor 2례이었다.

• Journal of Preventive Medicine and Public Health
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• 제47권1호
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• pp.36-46
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• 2014

Objectives: To evaluate the association between fracture risk and levothyroxine use in elderly women with hypothyroidism, according to previous osteoporosis history. Methods: We conducted a cohort study from the Korean Health Insurance Review and Assessment Service claims database from January 2005 to June 2006. The study population comprised women aged ${\geq}65$ years who had been diagnosed with hypothyroidism and prescribed levothyroxine monotherapy. We excluded patients who met any of the following criteria: previous fracture history, hyperthyroidism, thyroid cancer, or pituitary disorder; low levothyroxine adherence; or a follow-up period <90 days. We categorized the daily levothyroxine doses into 4 groups: ${\leq}50{\mu}g/d$, 51 to $100{\mu}g/d$, 101 to $150{\mu}g/d$, and > $150{\mu}g/d$. The hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated with the Cox proportional hazard model, and subgroup analyses were performed according to the osteoporosis history and osteoporosis-specific drug prescription status. Results: Among 11 155 cohort participants, 35.6% had previous histories of osteoporosis. The adjusted HR of fracture for the > $150{\mu}g/d$ group, compared with the 51 to $100{\mu}g/d$ group, was 1.56 (95% CI, 1.03 to 2.37) in osteoporosis subgroup. In the highly probable osteoporosis subgroup, restricted to patients who were concurrently prescribed osteoporosis-specific drugs, the adjusted HR of fracture for the > $150{\mu}g/d$ group, compared with the 51 to 100 ${\mu}g/d$ group, was 1.93 (95% CI, 1.14 to 3.26). Conclusions: While further studies are needed, physicians should be concerned about potential levothyroxine overtreatment in elderly osteoporosis patients.

• The Journal of Advanced Prosthodontics
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• 제4권2호
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• pp.76-83
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• 2012

PURPOSE. Zirconia has been used in clinical dentistry for approximately a decade, and there have been several reports regarding the clinical performance and survival rates of zirconia-based restorations. The aim of this article was to review the literatures published from 2000 to 2010 regarding the clinical performance and the causes of failure of zirconia fixed partial dentures (FPDs). MATERIALS AND METHODS. An electronic search of English peer-reviewed dental literatures was performed through PubMed to obtain all the clinical studies focused on the performance of the zirconia FPDs. The electronic search was supplemented by manual searching through the references of the selected articles for possible inclusion of some articles. Randomized controlled clinical trials, longitudinal prospective and retrospective cohort studies were the focuses of this review. Articles that did not focus on the restoration of teeth using zirconia-based restorations were excluded from this review. RESULTS. There have been three studies for the study of zirconia single crowns. The clinical outcome was satisfactory (acceptable) according to the CDA evaluation. There have been 14 studies for the study of zirconia FPDs. The survival rates of zirconia anterior and posterior FPDs ranged between 73.9% - 100% after 2 - 5 years. The causes of failure were veneer fracture, ceramic core fracture, abutment tooth fracture, secondary caries, and restoration dislodgment. CONCLUSION. The overall performance of zirconia FPDs was satisfactory according to either USPHS criteria or CDA evaluations. Fracture resistance of core and veneering ceramics, bonding between core and veneering materials, and marginal discrepancy of zirconia-based restorations were discussed as the causes of failure. Because of its repeated occurrence in many studies, future researches are essentially required to clarify this problem and to reduce the fracture incident.

• Journal of Trauma and Injury
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• 제28권3호
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• pp.144-148
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• 2015

Purpose: Immediate identification of vascular injury requiring embolization in patients with pelvic bone fracture isn't an easy task. There have been many trials finding indicators of embolization for patients with pelvic bone fracture. Although Young and Burgess classification is useful in decision making of treatment, it is reported to have little value as indicator of embolization in major trauma patients. The aim of this study is to find out Young and burgess classification on predicting vessel injury by analzyng pelvic radiograph taken from major trauma patients with pelvic bone fracture. Methods: Among major trauma patients with injury severity scores (ISS) higher than 15 who visited our emergency room from January 2011 to June 2014, 200 patients were found with pelvic bone fracture in trauma series and thus pelvic CT angiography was taken. Setting aside patients with exclusion criteria, 153 patients were enrolled in this study for analysis of Young and Burgess classification. Results: The most common mechanism of injury was lateral compression in both groups. There was no statistical significant difference in Young and Burgess classification (p=0.397). The obturator artery was the most commonly injured artery in both groups. Six patients had more than one site of bleeding. Conclusion: Prediction of transcatheter angiographic embolization using Young and Burgess classification in severe trauma patients is difficult and requires additional studies.