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고배속 CD-ROM Drive의 진동댐퍼 설계에 관한 연구
장승환,김현석,최진경,이대길,Chang, Seung-Hwan,Kim, Hyeon-Seok,Choi, Jin-Gyeong,Lee, Dae-Gil 대한기계학회 1998 大韓機械學會論文集A Vol.22 No.4
Rubber dampers are widely used to damp out vibrations generated in many mechanical elements because of the excellent damping characteristics of rubber. The damping characteristics of rubber is much dependent on temperature and frequency, which, in some cases, limit the effectiveness of rubber dampers. In this study, in order to increase the damping properties and axial and cross stiffnesses of rubber vibration dampers which are used in recording and regenerating devices, solid cores were inserted with interference tolerance in the rubber dampers. The damping characteristics of the rubber dampers with cores were investigated by experimentally and numerically using finite element method with respect to the interference tolerance, the core roughness, the materials of the core and the environmental temperature. From the experimental and theoretical investigations, it was found that the core in the rubber increased both the damping and stiffness of the damper. Also, it was found that the damping and stiffness of the rubber damper were much dependent on the temperature and frequency. Using the results of the experimental and theoretical investigations, the optimum design method for the cored rubber damper for recording and regenerating devices was developed.
한민구 ( Min Gu Han ),배지훈 ( Ji Hun Bae ),이성우 ( Sung Woo Lee ),장승환 ( Seung Hwan Chang ) 한국복합재료학회 2017 Composites research Vol.30 No.1
일방향 탄소섬유 복합재료는 복잡한 성형 공정과 낮은 드레이핑능을 보여 비교적 단순한 형태의 구조물 제작에 제한적으로 사용되어 왔으나, 최근 이를 해결하고자 성형성과 생산효율이 우수한 장섬유 복합재료(Long Fiber Prepreg Sheet; LFPS)가 제안되었다. 본 연구에서는 단순한 성형 공정과 높은 성형 정밀도를 갖는 LFPS를 활용하여 전자 기기용 커버 플레이트 설계를 수행하였다. 설계에 앞서 리브 구조가 적용되는 대상 구조물을 8-inch 태블릿 PC 제품의 뒷 커버로 선정하였다. 해당 구조물에 평판에 적용되는 대표적인 하중 조건을 선정하여 유한 요소해석에 적용하였고, 이를 활용하여 리브 구조물의 패턴과 리브 형상 변화에 따른 구조물의 구조 강성을 확인하였다. 해석 결과 제한된 부피 내에서 최적의 리브 패턴과 형상을 확보하였으며, 리브 폭이 균일하지 않은 경우가 균일한 경우에 비해 6~10% 처짐량이 감소함을 확인하였다. Carbon fiber reinforced composites have light weight and high mechanical properties. These materials are only applicable in limited shape structure cause by complex curing process and low drapability. To solve this problem, Long Fiber Prepreg Sheet (LFPS) has been proposed. In this research, electric device cover plate was selected and designed by using LFPS. Before the design process, we analyzed the target structure to which the rib structures were applied. And 8-inch tablet PC product was selected. For FE analysis, simple loading and boundary conditions were applied. Stiffness of rib structure was investigated according to the rib pattern and shape changes. Rib pattern and shape were selected based on fixed volume condition analysis results. And uneven rib width model was selected for the best case whose deflection was reduced 6~10% than uniform rib model.
발포재가 내장된 직조 탄소섬유 샌드위치 구조의 미소 유한요소 모델링에 관한 연구
장승환(Seung Hwan Chang),전성식(Seong Sik Cheon) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
In this paper, a modified unit cell model was employed to characterise the mechanical behaviors of the metallic foam, which can be used for the core material of sandwich structures. Also, a representative unit volume (RUV) FE model was introduced to simulate thermoforming process of carbon fabric-metallic foam sandwich structures. Thermoforming simulations, which capture crimp angles and amplitude changes of carbon fabric with respect to different operational pressure were conducted with the help of RUV FE model. Changed shapes of tow structure after thermoforming were rigorously reflected in the two dimensional models to determine mechanical properties of skin parts, i.e. carbon fabric composites after thermoforming.
반구형 금형으로의 드레이핑에 의한 탄소섬유/에폭시 직물 복합 재료 미세 토우구조의 변형
장승환(Seung Hwan Chang),정지규(Jee Gyu Chung) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
This paper aims to investigate the tow deformation pattern with respect to shear angle and mold property during draping of plain weave carbon/epoxy prepreg. Aluminum and PVC foams with different foam density are used for the draping hemisphere molds with 250 mm diameters. Microscopic observation reveals that tow parameters like crimp angle and Y-directional tow intervals are influenced by shear angle and mold density at the same time. The correlation between crimp angle and Y-directional tow interval is also found out.
장승환(Seung Hwan Chang),김주호(Ju Ho Kim) 한국생산제조학회 2007 한국공작기계학회 춘계학술대회논문집 Vol.2007 No.-
In this paper, foam-composite sandwich structure for EDM machine tool components such as column and column block were designed by controlling stacking sequence and number of ply considering bending stiffness and damping ratio of the composite structures. The original column block is a box-shaped structure made of aluminum connecting column and Z-stage of the system. This research was focused on the design of efficient column block structure using foam-composite sandwich structure which have good bending stiffness and damping characteristics to reduce the mass and increase damping ratio of the system. Vibration tests for getting damping ratio with respect to the stacking angle and thickness of the composites was performed. Finite element analysis for static defection due to the dead weight and vibration behaviour were also carried out to find out the appropriate stacking conditions; that is, stacking sequence and rib configuration. From the test and analysis results it was found that composite-foam sandwich structures for the microfactory system can be successful alternatives for high precision machining.
직교 그리드 센서가 삽입된 인솔을 이용한 족압분포 연구
손정협 ( Jeong-Hyeop Son ),정인준 ( In-jun Jung ),장승환 ( Seung-hwan Chang ) 한국복합재료학회 2021 Composites research Vol.34 No.3
본 연구에서는 당뇨병 환자들의 균일한 족압 분포를 유도하여 발의 상처를 예방하는 신발을 개발하기 위한 연구방법을 제시하였다. 직교 그리드 센서를 사용하여 일반인의 직립 상태 시 족압 분포를 확인하고, 다양한 조건에 대한 족압분포의 변화를 비교하였다. 신발 바닥부에 삽입된 스프링의 스프링 상수와 인솔의 아치부 유무 등에 따른 족압 분포의 변화를 파악하여 효과적인 족압 분산 조건을 확인하였다. 인체거동의 임의성 등에 의한 실험 오차를 최소화 하기 위해, 직립 상태를 모사한 유한요소해석을 통해 특정 조건에서의 족압 분포를 예측하고 실험 결과와 비교하여 실험의 정확성을 확보할 수 있도록 하였다. 스프링의 개수와 배치에 따른 족압 분포의 변화를 유한요소해석을 통해 확인하여 보다 균일한 족압을 구현할 수 있는 조건을 제시하였다. 이러한 결과는 당뇨발을 가진 환자를 위한 신발 설계에 활용할 수 있을 것으로 기대된다. In this study, we present a research method to develop a shoe that prevents foot injury by inducing the foot pressure. An orthogonal grid sensor was used to check the foot pressure in the upright standing position, and the change in the foot pressure distribution for various conditions was compared. We checked the conditions for distributing foot pressure efficiently by changing the spring constant of the spring inserted into the sole of the shoe and the foot pressure generated with or without the arch of the insole. In order to minimize the experimental error from the randomness of the human body's behavior, it is possible to predict through foot pressure under certain conditions through finite element analysis that simulates the pressure distribution. By checking the change of foot pressure according to the number and arrangement of springs through finite element analysis, conditions were established to provide more efficient foot pressure. The result can be used for designing footwear for patients with diabetic feet.