• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.497-501
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• 2008

To improve occupants' safety in an emergency, crashworthy design is necessary to rotorcraft design and development. To improve crashworthiness capability, most of the crash energy should be absorbed by rotorcraft and the energy transmitted to the occupants should be minimized. To absorb the crash energy efficiently, the individual energy attenuation provided by landing gear, structure, fuel tank and seats should be considered totally. Especially, landing gear has the important role for crashworthy design because landing gear absorbs relatively large energy for the crash landing. In addition, military specifications require failure of landing gear shall not increase danger to any occupants by penetration of the airframe. To meet the specification requirements, failure mechanism should be prepared so that landing gear is collapsed safely and doesn't penetrate the airframe. In this study, design of failure mechanism which is necessary for the rotorcraft landing gear was performed and the results were presented.

• 대한조선학회논문집
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• 제52권1호
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• pp.52-60
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• 2015

In the present study, an evaluation method for progressive failure of composite laminates has been proposed based on Puck's failure criterion and damage mechanics. The initial failure (or initiation of crack/delamination) has been assessed using Puck's failure criterion, and the progressive failure (or growth of crack/delamination) has been evaluated using fiber- and matrix-dependent damage variables. Based on Puck's failure criterion-damage mechanics coupling theories, the ABAQUS user-defined subroutine UMAT has been developed in order to analyze the progressive failure of glass/carbon fiber-reinforced composite laminates efficiently. In addition, the developed subroutine has been applied to progressive failure problem of industrial composite laminates, and the analysis results has been compared to experimental results which have been already reported in publications. It was confirmed that the simulation results were coincided well with the reported composite failure results.

• International Journal of Precision Engineering and Manufacturing
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• 제1권2호
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• pp.48-54
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• 2000

This paper presents the effect of shape of external corrosion in pipeline on failure prediction by using a numerical simulation. The numerical study for the pipeline failure analysis is based on the FEM(Finite Element Method)with an elastic-plstic and large-deformation analysis. Corrosion pits and narrow corrosion grooves in pressurized pipeline were analysed. A failure criterion, based on the local stress state at the corrosion and a plastic collapse failure mechanism, is proposed. The predicted failure stress assessed for the simulated corrosion defects having different corroded shapes along the pipeline axis compared with those by methods specified in ANSI/ASME B31G code and a modified B31G code. It is concluded the corrosion geometry significantly affects the failure behavior of corroded pipeline and categorisation of pipeline corrosion should be considered in the development of new guidance for integrity assessment.

• Geomechanics and Engineering
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• 제15권1호
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• pp.669-676
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• 2018

The "pseudo-wedge" failure is a name for a complex instability occurring at the Sarcheshmeh open-pit mine (Iran). The pseudo-wedge failure contains both the rock bridge failure and sliding along pre-existing discontinuities. In this paper, a cross section of the failure area was first modeled using a bonded-particle method. The results indicated development of tensile cracks at the slope toe which explains the freedom of pseudo-wedge blocks to slide. Then, a three-dimensional discrete element method was used to perform a block analysis of the instability. The technique of shear strength reduction was used to calculate the factor of safety. Finally, the influence of geometrical characteristics of the mine wall on the pseudo-wedge failure was investigated. The safety factor significantly increases as the dip and dip direction of the wall decrease, and reaches an acceptable value with a 10-degree decrease of them.

• 산업기술연구
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• 제27권B호
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• pp.245-253
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• 2007

Failure rate serves as a pivotal role in reliability study. Of all, the constant failure rate is the most popularly used in field exercises. In reality, however, the electrical and electronic parts' life is represented by not only the constant failure rate but the decreasing and/or increasing failure rates. Explicit consideration and incorporation of them into the model development may yield more desirable results. In this study, we built a reliability model for failure rates varying over time intervals and derived well known measures such as probability density function, reliability function, mean life, moments, and mission time. We then evaluated mean life with consideration of the first-year multiplier and compared the results those with constant failure rate. The results given in the study may provide a reference applying for practical decision making.

• 항공우주시스템공학회지
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• 제15권6호
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• pp.19-25
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• 2021

This paper presents a method that uses the stress failure criteria to predict the tensile failure strength of open-hole laminates with stress concentrations. The composite material used in this study corresponds to a 177 ℃ cured, carbon/epoxy unidirectional tape prepreg. The results obtained by testing ten different laminates were compared and analyzed to verify the tensile strength of the open-hole laminates predicted using the proposed stress failure criteria. The findings of this study confirm that the tensile strength predictions performed using the proposed method are generally accurate, except in cases involving highly soft laminates (10% of 0° ply).

• 간호행정학회지
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• 제2권1호
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• pp.57-72
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• 1996

Provision of better nursing care to patients is a difficult but important task. The first problem for nursing quality improvement is development of evaluation tool for the quality of nursing care. This study tries to develop a patient care tool for patients with chronic renal failure. This study as a procedural evaluation of patient care, tries to show what, how, at what order to provide care to patients with chronic renal failure. This study is divided into process of development of tool, its reliability and validity. Among process of development of tool is focal group, small expert group and expert evaluation group. To develop approprieteness of tool, nurses working is four major hospitals is Seoul were selected. To evaluate the credibility of subjects, 19 patient who were hospitalized and discharged within 3 months were selected. The period for collecting data for reliability and valiability evaluation was between Sept. 20 to Oct. 18, 1995. The development process of this study is as follows ; 1. Make preliminary list of the tool by focal group consisting of 8 clinical nurses. 2. Modify and add preliminary list by 4 expert nursing panel. 3. Calculate content validity of the tool by 23 nursing expert panel of judge. 4. Verity relability and validity of the tool. 5. Finalize an evaluation tool for the quality of nursing care in chronic renal failure patient. The result of this study were as follows ; 1. Development of evaluation tool for the quality of nursing care in chronic renal failure. 1) The evaluation of this study was developed 5 standards, 28 criteria. and 130 indicators 2) Nursing care evaluation scores for chronic renal failure patients were average 68.8. 2. Verity reliability and validity of the tool. 1) 5 standards were divided into 4 point scale and according to 28 creteria, indicators of standard were 3.72 and of criteria were 3.77 2) Inter - rater reliability (consentaneity score) of the tool by pearson correlation coefficient betwwen rates were r= .72, r= .75 and interreliabilities by single - facet crossed design were r= .96. 3) The alpha coeffecient relating to internal consistency was .7259 over 27 items of 28 criterias of developed tool. Through this study, I'm sure that the developed tool for the quality of patient care in chronic-renal failure patient will show the way of more improvement of the quality of nursing care and effective nursing intervention.

• 대한기계학회논문집A
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• 제34권1호
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• pp.111-116
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• 2010

비상착륙상황에서 승객의 안전을 향상시키기 위한 내추락 설계는 회전익기 설계 개발에 있어 필수적이다. 특히, 추락 시 착륙장치는 상대적으로 많은 에너지를 흡수할 수 있기 때문에, 내추락 설계에 있어 중요한 역할을 한다. 군사규격에서는 착륙장치의 에너지 흡수능력 뿐만 아니라, 파손 후 동체를 뚫고 들어가 승객에게 2차 피해를 주지 않아야 함을 규정하고 있다. 이와 같은 군사규격을 만족하기 위해서는 파손장치와 같은 내추락 장치를 마련하여, 착륙장치가 파손 후 안전하게 붕괴되어 동체를 뚫고 들어가지 않도록 해야 한다. 본 연구에서는 회전익기 착륙장치에 필수적인 파손장치의 설계 및 설계개발시험을 수행하였다. 먼저 착륙장치가 동체를 뚫고 들어가지 않도록 하기 위한 붕괴 과정을 결정하였다. 다음으로 파손장치에서 가장 중요한 부품인 파손 핀을 설계하였고, 설계기준을 만족하도록 2가지 강도 범위로 설계되었다. 최종적으로 설계개발시험을 통해 파손장치 설계를 성공적으로 검증하였다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.532-543
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• 2004

The present work have been developed the interpretation processor including the behavior of material failure and the separation phenomena under transient dynamic loading (the operation of explosive bolt) using AUTODYN V4.3, SoildWork 2003 and TrueGrid V2.1 programs. It has been demonstrated that the interpretation in ridge-cut explosive bolt under dynamic loading condition should be necessary to the appropriate failure model and the basic stress of bolt failure is the principal stress. The use of this interpretation processor developing the present work could be extensively helped to design the shape and the amount of explosives in the explosive bolt having a complex geometry. It is also proved that the interpretation processor approach is an accurate and effective analysis technique to evaluate the separation mechanism in explosive bolts.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• 제12권sup1호
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• pp.41-45
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• 2009

Optimal nutrition in infancy and early childhood is the success behind good health, growth, and development of children. Failure to thrive may be the end point of any combination of a nutritional disorder, poor growth, and psychosocial deprivation. Hospital admission is rarely necessary and may be counterproductive. Day attendance, for investigation and observation of child-parent interaction, may be more valuable. Nutritional supplementation, together with nutritional counseling, can improve food intake and growth in children with failure to thrive.