• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문초록집
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• pp.372.2-372
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• 2002

This paper presents an efficient modeling method fur open cracked beam structures. An equivalent bending spring model is introduced to represent the structural weakening effect in the presence of open cracks. The proposed method adopts the exact dynamic element method (EDEM) to avoid the difficulty and numerical errors in association with re-meshing the structure. The proposed method is rigorously compared with a commercial finite element code. (omitted)

• 한국항공우주학회지
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• 제41권11호
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• pp.900-907
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• 2013

페이로드 페어링은 위성과 부품들을 외부환경으로부터 보호하며, 위성분리 전에 페이로드 페어링은 분리된다. 페이로드 페어링은 굽힘 강성과 무게에 비해 강도 비율이 우수한 복합재 샌드위치 재료로 제작 되었다. 페이로드 페어링은 비행 중에 압축, 굽힘 그리고 전단하중을 받게 된다. 본 연구에서는 PLF와 연결구조물의 강도를 확인하기 위하여 액추에이터와 치구를 사용하여 PLF 구조시험을 수행하였다. 구조시험의 목적은 분리 스프링의 힘이 PLF에 가해진 상태에서 조합하중이 PLF에 작용할 때 PLF의 건전성을 확인하는 것이다. 구조시험 결과에서는 분리 스프링 하중과 조합하중에 의한 PLF의 구조 건전성을 확인하였다.

• 한국정보과학회논문지:컴퓨팅의 실제 및 레터
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• 제12권3호
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• pp.208-217
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• 2006

본 논문은 소성변형(plastic deformation)특성을 갖는 직물의 움직임을 시뮬레이션하는 기법을 제안한다. 소성은 탄성과 반대되는 개념으로, 물질이 외부의 힘에 의해 변형되었을 때, 초기상태로 완전히 회복되지 못하는 성질이다. 직물은 파티클 모델(particle model)을 이용하여 모델링하며, 파티클간의 상호작용은 바로 인접한 파티클간의 순차연결과 한 파티클 건너에 있는 파티클간의 교차연결을 설정함으로써 표현한다. 순차연결은 직물의 압축과 인장변형을, 교차연결은 직물의 굽힙변형을 표현한다. 연결은 스프링으로 모델링하는데, 순차연결은 탄성스프링으로, 교차연결은 변형정도에 따라, 탄성스프링 또는 소성스프링으로 모델링한다. 본 논문은 기존의 파티클 모델에서 사용하는 탄성스프링에 소성스프링을 추가하여 직물의 소성변형 현상을 표현한 것이다. 그 결과, 굽힘주름과 영구변형된 구김주름, 그리고 주름이 직물 전체에 고루 분포되는 현상을 시뮬레이션할 수 있었다. 연결의 탄성스프링과 소성스프링을 모델링할 때 직물운동방정식 수치해법의 안정성을 보장하기 위해 직물 시스템의 강성 메트릭스 (stiffness matrix)가 indefinite이 되지 않도록 주의를 기울였다.

• 전산구조공학
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• 제9권3호
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• pp.199-207
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• 1996

원통관에 휨모멘트가 작용하면 변형후 단면은 타원형상을 갖게된다. 단면의 타원화에 의해 단면이 감소하게 되면 휨강성이 감소하게 되며, 따라서, 휨모멘트-곡률관계가 하중점감형으로 된다. 이 휨강성의 감소현상을 Brazier이론 또는 Brazier현상이라고 한다. 적층평판에 있어서도 각층의 재료상수가 뚜렷하게 다른 경우 원통관에서의 Brazier현상과 유사한 현상이 발생한다. 본 논문에서는 평판에서의 Brazier현상을 규명하기 위하여 3층 적층모델을 만들어 각층의 재료정수가 현저히 다른 경우 어떠한 현상이 일어나는 가를 실험적으로 규명하였고, 이론해석을 위하여 스프링모델을 사용하였다. 본 논문의 모델에서 알 수 있듯이 중간층의 재료상수가 상하층 요소의 재료상수 보다 뚜렷하게 작은 경우 중간층의 거동이 현저히 크게됨을 알 수 있었다. 즉, 본 논문에서 채택한 모델의 경우에 있어서도 원통관에서 일어나는 Brazier형상이 일어나고 있음이 실험적 그리고 해석적으로 규명되었다 .

• Tribology and Lubricants
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• 제15권3호
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• pp.278-286
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• 1999

To predict the behavior of the intravascular micro active endoscope in the real human vascular system, a human mock circulation system was developed. The intravascular micro active endoscope which consists of micro active bending catheter and micro drug infusion catheter was driven in the velocity, Re number and temperature controlled flow. The three SMA (Shape Memory Alloy) zigzag type spring in the micro active bending catheter was heated by the electric current generated by PWM controller, and the shape memory effect made the actuator bend to any direction. The micro drug infusion catheter was driven through the inner hole of the micro active bending catheter. A mock circulation system is shaped from Ascending Arota to Femoral artery according to a human data (the data contains many vascular sizes and hydrographs of many control points). We developed a vascular model with glass and silicone tubes, and set the flow system with circulation parts, flow settling parts, and lots of valves. The heater and heat-controller was added to the How system to centre! the temperature of the How at 36.5$^{\circ}C$. The result showed that the developed intravascular micro active endoscope could be induced to any point in the vascular model.

• 한국전산구조공학회논문집
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• 제34권6호
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• pp.393-401
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• 2021

본 논문에서는 폭발하중을 받는 부재의 저항성능 평가를 위한 모멘트-곡률 관계 기반 수치해석 기법을 소개한다. 직접전단 파괴 모드를 고려하기 위하여 경험적인 직접전단응력-슬립양 관계를 기반으로 하는 무차원 스프링 요소를 도입하였다. 재료에 대해 정의된 동적증가계수 식을 바탕으로 단면의 모멘트-곡률 관계에 직접적으로 적용가능한 단면의 곡률 변화율에 따른 동적증가계수 식을 제작하였다. 또한 부착슬립의 영향을 고려하기 위하여 소성힌지영역 내에 등가 휨강성을 도입하였다. 제안된 수치해석 모델의 타당성 검증을 위하여 실험결과와의 비교연구를 수행하였으며, 단자유도계 모델의 해석결과와의 비교를 통해 본 수치해석 모델의 우수성을 확인하였다. P-I 선도를 제작하여 부재의 휨 파괴 및 직접전단 파괴에 대한 저항성능을 평가하였으며, 매개변수 연구를 수행하여 P-I 선도 및 저항성능의 변화를 확인하였다.

• Journal of Biosystems Engineering
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• 제33권4호
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• pp.224-229
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• 2008

This study was aimed to minimize the impact force and vibration transmitted to the transporting materials from the trailer and wheel shaft by installing the leaf spring suspension device at the space between the wheel shaft and frame of power tiller trailer. The developed trailer equipped with leaf spring suspension device was compared to the existing trailer without suspension device, in order to identify the vibration absorption effect of the leaf spring. The results of this study could be summarized as follows; (1) The length and the maximum bending amount of the leaf spring were designed as 1,000 mm and 42 mm, respectively, considering the possible space for installing at below the trailer. When 4 leaf springs were installed on both wheel shafts, the allowable maximum load was identified as 9,418 N. (2) The average vibration accelerations for the frequency less than 20 Hz, where the severe transporting loss could be represented, were $0.017\;m/s^2$ and $0.133\;m/s^2$ for the developed and the existing trailer, respectively, showing the vibration absorption effect of about 87%. And the average vibration accelerations on the driver's seat for the frequency less than 20 Hz were $0.01\;m/s^2$ and $0.20\;m/s^2$ for the developed and the existing trailer, respectively, which showed the similar vibration absorption effect. (3) The change of the average vibration accelerations for the frequency from 20 Hz to 80 Hz showed the similar tendency with the result for the frequency less than 20 Hz, but the effect for developed trailer was reduced slightly. And the effect of vibration absorption for the above 80 Hz was reduced highly. However, by installing the leaf spring suspension device at the trailer, the low frequency below 40 Hz, which could affect on transporting loss severely, could be reduced highly. (4) The maximum vibration acceleration for the frequency less than 20 Hz were $0.027\;m/s^2$ and $1.267\;m/s^2$ for the developed and the existing trailer, respectively. And the change of maximum acceleration between 20 Hz and 120 Hz was showed similar tendency with the result for the frequency less than 20 Hz, but the width of change was reduced highly.

• 한국기계가공학회지
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• 제7권3호
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• pp.75-80
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• 2008

The progressive die performs a work of sheet metal processes with a piercing, notching, embossing, bending, drawing, cut-off etc. in many kinds of pressing. Now a days, these processes have been evaluated as a advanced tooling method to increase the productivity and high quality assurance. The first step analyzing of die design is production part review, then the arrangement drawing of product design and strip process layout design should be done as a next steps with a FEM simulation for its problem solution. After upper procedure were peformed, it was started to make the die, then tryout and its revision of the die and product quality, safety, productivity etc. were done continually. For the all of these process, we mobilized the theory and practice of sheet metal forming, die structure, the function and activity of die components, and the others of die machining, die material, heat treatment and know‐how so on. In this study the features of representative are production part analyzing through the FEM simulation of bending area with a considering spring back problem by DEFORM.

• 한국지진공학회논문집
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• 제24권2호
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• pp.95-102
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• 2020

Electrical instruments and devices contained in cabinets for controlling nuclear power plants require seismic qualification; likewise, in-cabinet response spectrum (ICRS) is necessary. Gupta et al. (1999) suggested the Ritz method, where rocking, frame bending, and plate bending behaviors of cabinets are considered, as a method for determining ICRS. This research proposes a method to determine the rocking stiffness of cabinets, which represents its rocking behavior. The cabinet is fixed on mounting frames and is connected to the base concrete by anchors. When horizontal excitation is applied to the cabinet, the mounting frames at anchors are locally deformed, the mounting frames are bent, and then rocking in the cabinet becomes evident. A method to determine equivalent vertical spring stiffness representing the local deformation of the mounting frames at anchors is then proposed. Subsequently, the rocking stiffness of this mounting frame is calculated upon assumption of the mounting frame as an indeterminate beam.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2001년도 추계학술대회 논문집
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• pp.247-252
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• 2001

Recently the steel parts used at automobiles are required to be used under high stress more than ever before in need of the weight down. To achieve this requirement of a high strength steel, it must be necessary to decrease inclusion content and surface defect as like decarburization, surface roughness etc.. In this study, the surface conditions are measured to know the influence on fatigue properties by two cases of shot peening of two-stage shot peening and single-stage shot peening. And for this study, two kinds of spring steel (SUP7, 50CrV4) are used. This study shows the outstanding improvement of fatigue properties at the case of two-stage shot peening in the rotary bending fatigue test and this is assumed to be from on low stress condition, the 1st stage shot peening is not affected by nonmetallic inclusion under metal. it is possible that the 2nd stage shot peening increases the fatigue life and the high stress but that is affected by nonmetallic inclusion under metal. so far beeasily 50CrV4 have made high stress. But, results also show fatigue failures originated at inclusion near surface, and this inclusion type is turned out to be a alumina of high hardness.