• Design & Manufacturing
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• 제7권1호
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• pp.28-33
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• 2013

During the cold forming, due to high working pressure acting on the die surface, failure mechanics must be considered before die design. One of the main reasons of die failure in industrial application of metal forming technologies is wear. The mechanisms of wear are consisted of adhesion, abrasion, erosion and so on. Die wear affects the tolerances of formed parts, metal flow, and costs of process. The only way to control these failures is to develop a prediction method on die wear suitable in the design state in order to optimize the process. The wear system is used to analyse 'operating variables' and 'system structure'. In this study, with AISI D2, AISI 1020, AISI 304SS materials, a series of the wear experiments of pin-on-disk type to obtain the wear coefficients from Archard's wear model and the upsetting processes are carried out to observe the wear phenomenon during the cold forming process. The analysis of upsetting processes are performed by the rigid-plastic finite element method. The result of the analysis is used to investigate the die wear the processes, and the analysis simulated die wear profiles are compared with the experimental measured die wear profiles.

• Steel and Composite Structures
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• 제31권5호
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• pp.453-467
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• 2019

Portal frame structures, made up of cold-formed steel trusses, are increasingly being used for lightweight building construction. A novel pin-jointed moment connector, called the Howick Rivet Connector (HRC), was developed and tested previously in T-joints and truss assemblage to determine its reliable strength, stiffness and moment resisting capacity. This paper presents an experimental study on the HRC, in moment resisting cold-formed steel trusses. The connection method is devised where intersecting truss members are confined by a gusset connected by HRCs to create a rigid moment connection. In total, three large scale experiments were conducted to determine the elastic capacity and cyclic behaviour of the gusseted truss moment connection comprising HRC connectors. Theoretical failure loads were also calculated and compared against the experimental failure loads. Results show that the HRCs work effectively at carrying high shear loads between the members of the truss, enabling rigid behaviour to be developed and giving elastic behaviour without tilting up to a defined yield point. An extended gusset connection has been proposed to maximize the moment carrying capacity in a truss knee connection using the HRCs, in which they are aligned around the perimeter of the gusset to maximize the moment capacity and to increase the stability of the truss knee joint.

• 한국항공우주학회지
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• 제41권8호
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• pp.625-631
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• 2013

핀풀러의 신뢰도를 몬테카를로 시뮬레이션을 통해서 예측하였다. 예측방법은 응력-강도 간섭 모델에 근거한다. 이 모델은 강도가 응력보다 작을 경우를 고장으로 간주한다. 본 연구에서 강도는 핀을 예정된 거리까지 후퇴시키는데 필요한 에너지로, 응력은 이 핀의 운동을 방해하는데 소요되는 에너지로 간주하였다. 전자는 주로 화약량에 의해 결정되고 후자는 여러 가지 마찰력과 반발방지장치에서 소모되는 에너지에 의존한다. 응력과 강도 변수들은 해석적 성능 모델로부터 계산하였다. 본 연구에서 제시된 방법은 많은 시료가 필요하지 않기 때문에 유사한 종류의 파이로 장치 신뢰도 계산에도 적용될 수 있다.

• 해양환경안전학회지
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• 제26권6호
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• pp.706-714
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• 2020

전 세계 90 %의 인구가 WHO의 연평균 미세먼지 노출 기준(10 ㎍/㎥)을 초과한 공기를 흡입하고 있다. 전 세계적으로 육상뿐만 아니라 해양에서 발생하는 질소산화물에 대한 규제를 통해 2차 오염물질, 초미세먼지 저감에 대해 노력하고 있으며 국내에서는 선박에서 미세먼지 발생의 주요한 원인인 황 함유량 저감과 환경친화적 선박의 개발 및 보급 등을 통해 깨끗한 해양환경 조성을 위한 노력을 하고 있다. 디젤엔진 유해 배출가스 저감을 위한 기술 중 압력 손실이 적고 높은 집진 효율 및 NOx의 제거와 유지 관리의 장점이 많은 전기 집진기의 수요와 중요성이 증가하고 있다. 본 연구는 총톤수 999톤급 선박의 2,427 kW 선박용 디젤엔진의 미세먼지 저감을 목적으로 개발된 전기 집진기를 예지보전단계에서 고장모드영향분석을 통해 장비 품질을 높여 선박 내에서의 내구연한을 높이고자 위험 우선순위 도출하였다. 위험 우선순위는 고장모드 241(poor dust capture efficiency)이 RPN 180으로 가장 높았다. Collecting electrode에서 가장 많은 고위험 고장모드를 검출하여 집중관리 부품으로 관리해야 할 필요가 있었으며 원인으로 진동과 핀 풀림으로 인한 유격 불량이 가장 많이 검출되었다. 핀 풀림 역시 근본적으로는 선체 또는 장비에서 발생하는 진동이 원인이 되어 발생할 수 있는 사항이기 때문에 핀 풀림이 발생하는 개소에 보완이 필요하겠다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2012년도 제38회 춘계학술대회논문집
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• pp.411-413
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• 2012

본 연구에서는 핀 하중 시험을 통해 열습환경이 탄소섬유/에폭시 복합재료에 미치는 영향을 조사하고 음향방출법을 적용하여 핀 체결부의 파손거동을 분석하였다. 열습환경이 적용된 핀 체결부 시편은 base (침수전), RT (상온침수), HT ($75^{\circ}C$침수)의 세 가지의 조건으로 구분하였다. 결과에 의하면 RT의 경우 base에 비해 베어링강도의 저하정도가 적지만 수분과 온도가 동시에 적용된 열습환경에 노출된 HT의 경우 베어링강도의 저하정도가 크게 나타났다. 또한 음향방출법을 적용하여 누적히트수를 분석한 결과에 따르면 열습을 고려한 경우가 base에 비해 모재균열에 의한 이벤트가 감소하는 경향이 나타났다.

• 한국구조물진단유지관리공학회 논문집
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• 제12권1호
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• pp.151-157
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• 2008

공용 중인 보는 시공상의 원인으로 충분한 매입깊이를 확보하기 어렵다. 이러한 문제점 때문에 현재의 FRP-Rod 매입공법은 단면증설 공법과 병행해서 실시하는 경우가 많다. 본 연구에서는 단면증설 없이 FRP-Rod의 활동 및 보강보의 일체성 문제를 해결하기 위하여 앵커핀이 채택되었다. 실험에서 피복 콘크리트의 할렬파괴와 FRP-Rod의 활동현상은 발생하지 않았으며, FRP-Rod는 보수보가 파괴 될 때까지 RC보와 일체 거동을 하는 것이 확인되었다.

• 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.

• Steel and Composite Structures
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• 제48권6호
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• pp.667-679
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• 2023

Concrete filled rectangular steel tubular (CFRST) composite truss girder is composed of the CFRST truss and concrete slab. The failure mechanism of the girder was different under bending and shear failure modes. The bending and shear strength of the girder were investigated experimentally. The influences of composite effect and shear to span ratio on failure modes of the girder was studied. Results indicated that the top chord and the joint of the truss were strengthened by the composited effect. The failure modes of the specimens were changed from the joint on top chord to the bottom chord. However, the composite effect had limited effect on the failure modes of the girder with small shear to span ratio. The concrete slab and top chord can be regarded as the composite top chord. In this case, the axial force distribution of the girder was close to the pin-jointed truss model. An approach of strength prediction was proposed which can take the composite effect and shear to span ratio into account. The approach gave accurate predictions on the strength of CFRST composite truss girder under different bending and shear failure modes.

• 한국안전학회지
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• 제32권3호
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• pp.54-59
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• 2017

This paper presents an efficient finite analysis model and a simulation-based reliability analysis method for stowage device system failure of a container crane with respect to lateral load. A quasi-static analysis model is introduced to simulate the nonlinear resistance characteristics and failure of tie-down and stowage pin, which are the main structural stowage devices of a crane. As a reliability analysis method, a subset simulation method is applied considering the uncertainties of later load and mechanical characteristic parameters of stowage devices. An efficient Markov chain Monte Carlo (MCMC) method is applied to sample random variables. Analysis result shows that the proposed model is able to estimate the probability of failure of crane system effectively which cannot be calculated practically by crude Monte Carlo simulation method.

• 한국신뢰성학회지:신뢰성응용연구
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• 제16권2호
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• pp.125-133
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• 2016

Purpose: The purpose of this study is to evaluate durability of platform safety step system in railway. Method: We performed finite element analysis & durability analysis of platform safety step system with VPD (Virtual Product Development) techniques and examined the durability standard & qualification life through the rig test during no failure test time in reliability qualification test. We continued to test 1 million cycles in KRS (Korea Railway Standard) for system's robust design performance. Result: FEM analysis results are 14.9MPa & 14.7MPa of pin-joint, pivot and durability analysis result is above 1 million cycles. we calculated theoretically no failure test time 855,000 cycles and through the 1 million cycles durability rig test in KRS standard we confirmed product quality. Conclusion: This platform safety step system was designed very safe in terms of a mechanical strength & durability.