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피라미드 형상의 내부구조를 가지는 초경량 금속 내부구조 접합판재의 제작 및 정적 굽힘실험
정창균(Chang Gyun Jung),윤석준(Seok-Joon Yoon),양동열(Dong-Yol Yang),이상민(Sang Min Lee),나석주(Suck-Joo Na),이상훈(Sang-hoon Lee),안동규(Dong-Gyu Ahn) Korean Society for Precision Engineering 2005 한국정밀공학회지 Vol.22 No.6
Inner structured and bonded panel, or ISH Panel, as a kind of sandwich type panel, has metallic inner structures which have low relative density, because of their dimensional shape of metal between a pare of metal skin sheets or face sheets. In this work, ISH panels and inner structures formed as repeated pyramidal shapes are introduced. Pyramidal structures are formed easily with expanded metal sheet by the crimping process. Three kinds of pyramidal structures are made and used to fabricate test specimen. Through the multi-point electrical resistance welding, inner structures are bonded with skin sheet. 3-point bending tests are carried out to measure the bending stiffness of ISH panel and experimental results are discussed.
트러스형 금속 샌드위치 판재에서 심재의 전단탄성계수의 실험적 결정
정창균(Chang Gyun Jung),성대용(Dae-Young Seong),양동열(Dong-Yol Yang),문경제(Kyung-Je Moon),안동규(Dong-Gyu Ahn) Korean Society for Precision Engineering 2007 한국정밀공학회지 Vol.24 No.8
A sandwich plate with a truss core is composed of two face sheets and a pyramidal truss core between face sheets. This paper shows how to estimate the shear modulus of a truss core, experimentally. To determine the shear modulus of truss cores, 3-point bending tests are performed. For tests, metallic sandwich beams with truss cores are fabricated. Two kinds of truss cores are tested to investigate the shear modulus. Each test is repeated under different widths in order to increase accuracy. As a result, the shear modulus of sandwich beam is properly calculated. The deflection of a sandwich beam with a truss core by shear deformation takes the major contribution of the total deflection and the shear modulus of sandwich beam should be considered whenever it is designed.
수직방향 직조 금속망을 이용한 초경량 금속 내부구조 접합판재의 제작 및 특성에 관한 기초 연구
정창균(Chang Gyun Jung),윤석준(Seok-Joon Yoon),양동열(Dong-Yol Yang),이상민(Sang Min Lee),나석주(Suck-Joo Na),이상훈(Sang-hoon Lee),안동규(Dong-Gyu Ahn) Korean Society for Precision Engineering 2005 한국정밀공학회지 Vol.22 No.5
Inner structured and bonded panel, or ISB Panel, as a kind of sandwich type panel, has metallic inner structures which have low relative density, due to their dimensional shape of metal between a pair of metal skin sheets or face sheets. Previous works showed that ISB panels containing inner structures formed as repeated pyramidal shapes saved weight up to 60% in condition of same stiffness comparing with solid sheet. In this work, woven metal is adapted to inner structures replacing pyramidal structures. The test specimens of ISB panel containing woven metal made by multi-point electric resistance welding and 3-point bending test have been carried out. The results of experiments and comparisons of process parameters, stiffness and failure mode are discussed.
피라미드 구조를 가지는 초경량 금속 내부구조 접합판재의 제작 및 특성평가
정창균(Chang Gyun Jung),윤석준(Seok-Joon Yoon),성대용(Dae-Yong Sung),양동열(Sung Dong-Yol),안동규(Dong-Gyu Ahn) 한국정밀공학회 2004 한국정밀공학회 학술발표대회 논문집 Vol.2004 No.10월
Inner structured and bonded panel, or ISB Panel, as a kind of sandwich type panel, has metallic inner structures which have low relative density, because of their dimensional shape of metal between a pare of metal skin sheets or face sheets. In this work, ISB panels and inner structures formed as repeated pyramidal shapes are introduced. Pyramidal structures are formed easily with expanded metal sheet by the crimping process. Three kinds of pyramidal structures are made and used to fabricate test specimen. Through the multi-point electrical resistance welding, inner structures are bonded with skin sheet. 3-point bending tests are carried out to measure the bending stiffness of ISB panel and experimental results are discussed.
트러스형 내부구조를 가지는 샌드위치 판재의 저속 충격 특성 연구
정창균(Chang Gyun Jung),성대용(Dae-Yong Seong),양동열(Dong-Yol Yang),김진석(Jin-Suck Kim),안동규(Dong-Gyu Ahn) Korean Society for Precision Engineering 2006 한국정밀공학회지 Vol.23 No.10
Metallic sandwich plate with a truss core has metallic inner structures which have low relative density between a pair of metal skin sheets or face sheets. In this work, low impact tests have been carried out to examine the behavior of sandwich plates with a pyramidal truss core. For the low velocity impact, the impact apparatus of drop weight type has been fabricated. From the results of the experiments, maximum energy absorption is found to happen when the upper sheet fails. The sandwich plate loses its absorption ability as soon as the inner structures have been crashed completely and optimal core thickness has existed to maximize energy absorption. Comparing the metallic sandwich plate with the monocoque plate, the absorbed energy has been improved up to 160 % and the deflection decreased by up to 76%. As a result, the metallic sandwich plate with a truss core is shown to have good material for impact resistance and energy absorption.
굽힘 하중을 받는 딤플형 내부구조 금속 샌드위치 판재의 최적설계변수의 수식화 및 파손선도
성대용(Dae Yong Seong),정창균(Chang Gyun Jung),윤석준(Seok Joon Yoon),양동열(Dong Yol Yang),안동규(Dong Gyu Ahn) Korean Society for Precision Engineering 2006 한국정밀공학회지 Vol.23 No.8
Metallic sandwich plates with inner dimpled shell subject to 3-point bending have been analyzed and then optimized for minimum weight. Inner dimpled shells can be easily fabricated by press or roll with high precision and bonded with same material skin sheets by resistance welding or adhesive bonding. Metallic sandwich plates with inner dimpled shell structure can be optimally designed for minimum weight subject to prescribed combination of bending and transverse shear loads. Fundamental findings for lightweight design are presented through constrained optimization. Failure responses of sandwich plates are predicted and formulated with an assumption of narrow sandwich beam theory. Failure is attributed to four kinds of mechanisms: face yielding, face buckling, dimple buckling and dimple collapse. Optimized shape of inner dimpled shell structure is a hemispherical shell to minimize weight without failure. It is demonstrated that bending stiffness of sandwich plate is 2 or 3 times larger than solid plates with the same strength. Failure mode boundaries and iso-strength lines dependent upon the geometry and yield strain of the material are plotted with respect to geometric parameters on the failure map. Because optimal parameters of maximum strength for given material weight can be selected from the map, analytic solutions for maximum strength are expressed as a function of only material property and proposed strength. These optimal parameters match well with numerical optimal parameters.
3 차원 유한요소해석을 이용한 스트레칭 조건에서의 두께 0.7 ㎜ 스테인레스 강판의 저속 충격 특성 분석
안동규(Dong Gyu Ahn),문경제(Kyung Je Moon),정창균(Chang Gyun Jung),양동열(Dong Yol Yang) Korean Society for Precision Engineering 2008 한국정밀공학회지 Vol.25 No.8
This paper investigated into the impact characteristics of the stainless sheet with thickness of 0.7 ㎜ on the stretching boundary condition through three-dimensional finite element analysis. High speed tensile tests were carried out to obtain strain-stress relationships with the effects of the strain rate. The FE analysis was performed by the ABAQUS explicit code. In order to improve an accuracy of the FE analysis, the hyper-elastic model and the damping factor were introduced. Through the comparison of the results of the FE analyses and those of the impact tests, a proper FE model was obtained. The results of the FE analyses showed that the absorption rate of energy maintains almost 82.5-83.5 % irrespective of the impact energy level and the diameter of the impact head. From the results of FE analyses, variations of stress, strain, dissipation energy, strain energy density, and local deformation characteristics in the stainless sheet during the collision and the rebound of the impact head were quantitatively examined. In addition, it was shown that the fracture of the specimen occurs when the plastic strain is 0.42 and the maximum value of the plastic dissipation energy of the specimen is nearly 1.83J.
망형 직조 금속을 내부구조체로 가진 ISB 판재의 심재 종탄성 및 전단 계수 예측
안동규(Dong-Gyu Ahn),남경흠(Gyung-Heum Nam),정창균(Chang-Gyun Jung),양동열(Dong-Yol Yang) Korean Society for Precision Engineering 2009 한국정밀공학회지 Vol.26 No.11
The elastic properties of core affect mechanical properties and deformation behaviours of the lightweight sandwich panel. The objective of the present paper is to estimate experimentally Young’s and shear moduli of a core in internally structured boned (ISB) panel with woven metal as inner structures using the deflection theory of sandwich beam considered core stiffness. Three points bending experiments were performed to obtain force-deflection curves of the designed ISB panel in each material direction. The elastic and shear moduli of the core in each material direction were estimated from slopes and intercepts of relationships between compliance per the span length and square of the span length, respectively. The results of the estimation showed that the fabric technology of the woven metal affects the variation of the elastic properties in the core. Through the comparison of shear moduli and force-deflection curves of the proposed method and those without considering the core stiffness, it was shown that the core stiffness should be considered to estimate properly the Young’s and shear moduli of ISB panels. Finally, the contribution ratio of bending and shear deflections of ISB panels to the total deflection was quantitatively examined.
피라미드형 내부구조체를 가진 ISB 판넬의 접합형태에 따른 충격 특성 변화
안동규(Dong-Gyu Ahn),문경제(Gyung-Jae Moon),정창균(Chang-Gyun Jung),양동열(Dong-Yol Yang) Korean Society for Precision Engineering 2007 한국정밀공학회지 Vol.24 No.9
ISB(Inner structured and bonded) panel with a pyramidal inner structure is actively developing to reduce the weight and to improve the crashworthiness of the material. The objective of this paper is to investigate into the variation of impact characteristics of ISB panels with a pyramidal inner structure according to joining types between skin sheets and inner structures. Several drop impact tests have been performed. In order to examine the impact characteristics at a drawing condition, drawing type of experimental set-up has been proposed. From the results of the experiments, the influence of joining types between skin sheets and the inner structures on the characteristics of the deformation, the energy absorption and the failure has been quantitatively examined. In addition, it has been shown that maximum load decreased and the maximum displacement increases as the joining type changes from the bonding to the welding. The results of the observation of the specimen have been shown that major wrinkles form in the minor crimping direction irrespective of the joining types. Through the comparison of the experimental results for bonding and welding specimens, it has been shown that the absorption energy of the bonded specimen is nearly 1.3-1.5 times of the welded specimen at the same displacement.
안동규(Dong-Gyu Ahn),문경제(Kyung-Je Moon),정창균(Chang-Gyun Jung),한길영(Gil-Young Han),양동열(Dong-Yol Yang) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
The objective of this paper is to investigate the influence of impact conditions on the impact characteristics of the stainless sheet for the case of the fixed boundary conditions. In order to examine impact characteristics of the sheet, three-dimensional finite element analyses and impact tests have been performed. High speed tensile tests have been carried out to obtain strain-stress relationships including the effects of the strain rate. In order to improve an accuracy of the FE analysis, the hyper-elastic model and the damping factor have been introduced. The results of the FE analyses and the impact tests have been shown that the diameter of the impact head does not affect the absorption energy of the stainless sheet. In addition, it has been shown that the absorption rate of energy maintains almost 82.5 - 83.5 % irrespective of the impact energy level and the diameter of the impact head. From the results of FE analyses, the variation of stress and strain energy in the stainless sheet has been quantitatively examined.