새로운 와이어 직조 다공질 금속의 압축 특성

고경득(Gyeong-Deuk Ko),이기원(Ki-Won Lee),강기주(Ki-Ju Kang) 대한기계학회 2010 大韓機械學會論文集A Vol.34 No.11

WBD(wire-woven bulk diamond)라고 명명한 와이어로 직조된 다공질 금속의 새로운 형태를 소개한다. WBD 는 기계적 열 특성과 공학적 응용면에서 몇 년 전에 소개되어진 WBK(wire-woven bulk Kaogme)와 같이 나선형 와이어로 구성된다. WBK 에서는 각 교차점에서 3 개의 와이어가 접하나 WBD 에서는 4 개의 와이어가 서로 접하여 배열된다. 압축하중 하에서 WBD 의 기계적 거동을 조사하고 그 결과를 WBK 와 비교하였다. 같은 세장비(d/c)에서 WBD 의 밀도 및 강도는 WBK 의 약 2 배이나, WBD 의 강성도는 WBK 보다 그만큼 높지 않다. In this study, a new type of wire-woven cellular metal named WBD(wire-woven bulk diamond) was developed. Like WBK(wire-woven bulk Kagome), WBD is composed of helically formed wires; WBK was introduced a few years ago, and its mechanical, thermal properties, and engineering applications have been extensively investigated. The number of wires that pass by one another at each cross point in WBD is four, whereas that in WBK is three. The mechanical behavior of WBD subjected to compression was investigated and the results were compared to those for WBK. For a given slenderness ratio the density and yield strength of WBD were about twice as high as those for WBK, but elastic stiffness of WBD was not that higher than that for WBK.

새로운 와이어직조 다공질 금속의 압축 특성

고경득(Gyeong Deuk Ko),강기주(Ki-Ju Kang) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.4

In this work, a new kind of wire-woven cellular metal named wire-woven bulk diamond(WBD) was introduced. WBD is composed of helically formed wires same as wire-woven bulk Kagome(WBK), which has been introduced a few years ago and has been investigated on its mechanical thermal properties, and engineering applications. In WBD four wire pass by one another at each cross point, where as in WBK three wires do. Mechanical behaviors of WBD under compression were investigated and the results were compared to those of WBK.

압축하중을 받는 WBK의 기계적 거동에 대한 방향 의존성

강기주(Ki-Ju Kang),김판수(Pan-Su Kim),허해규(Hae-Kyu Hur) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11

Wire-woven Bulk Kagome (WBK) is fabricated by assembling metallic wires spatially formed in the three-dimensional directions, and the WBK assembly is uniformly composed of a number of twisted wires. To get a better understanding of WBK structures and their mechanical characteristics, the concepts of WBK unit cell/sub-unit cell are introduced. And also several geometrical parameters based on a WBK unit cell are suggested to get the three-dimensional volume. By using the WBK unit cells, the orientation dependency on the mechanical behavior of WBK assemblies under compression is investigated theoretically. The strength, elastic modulus and failure mechanism of WBK structures are analyzed under various directions of loading. Finally, a good agreement between the present results and the available data is suggested.

다구찌법을 이용한 WBK(Wire-woven Bulk Kagome)의 최적설계

최지은(Ji ?Eun Choi),강기주(Ki-Ju Kang) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.11

A Wire-woven Bulk Kagome (WBK) is the new truss type cellular metal fabricated by assembling the helical wires in six directions. The WBK seems to be promising with respect to morphology, fabrication cost, and raw materials. In this paper, first, the geometric and material properties are defined as the main design parameters of the WBK considering the fact that the failure of WBK is caused by buckling of truss elements. Taguchi approach was used as statistical design of experiment(DOE) technique for optimizing the design parameters in terms of maximizing the compressive strength. Normalized specific strength is constant regardless of slenderness ratio even if material properties changed, while it increases gradually as the strainhardening coefficient decreases. Compressive strength of WBK dominantly depends on the slenderness ratio rather than one of the wire diameter, the strut length. Specifically the failure of WBK under compression by elastic buckling of struts mainly depended on the slenderness ratio and elastic modulus. However the failure of WBK by plastic failed marginally depended on the slenderness ratio, yield stress, hardening and filler metal area.

제진 댐퍼로서 WBK 의 적용가능성

고경득(Ko Gyeong-Deuk),주재황(Joo Jai-Hwang),황재승(Hwang Jae-Seung),강기주(Kang Ki-Ju) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11

최근 개방형이고 규칙적인 다기능성 다공질 금속인 Wire-woven Bulk Kagome(WBK)가 소개되었다. 이번 논문은 건물의 지진 대비 진동제어 장치용 댐퍼로서 WBK 의 적용가능성을 조사는 것이 목적이다. WBK 의 에너지 소산능력을 조사하기 위해 전단 하중 아래에서 WBK 의 이력곡선은 실험적으로 측정하였고 실험결과와 비교를 위해서 3-D 유한요소해석에 의거하는 동일한 시뮬레이션 또한 수행하였다. 실험과 시뮬레이션 결과는 WBK 가 초기 연성후에 안정된 이력현상을 보여준다. Recently, multifunctional cellular metal with open and periodic structures, Wire-woven Bulk Kagome(WBK) has been introduced. The purpose of present work is to examine the feasibility of the WBK as an anti-seismic vibration control device for building structures. Hysteresis loop of the WBK under cyclic shear loading was experimentally measured to investigate the performance of WBK in the energy dissipation capacity and in parallel a numerical simulation based on the 3-D finite element analysis was also carried out for the verification of the experimental results. Both experimental and numerical simulation results show that the WBK has a stable hysteresis response after some initial softening.

초경량 금속 구조재 직조장치의 설계 및 제작

김판수(Pan Su Kim),강기주(Ki Ju Kang) 대한기계학회 2010 大韓機械學會論文集A Vol.34 No.9

와이어직조 카고메(WBK)는 나선형으로 성형된 와이어를 6 방향에서 조립하여 제작된다. 지금까지의 WBK 는 수작업으로 조립되어 왔지만, 산업적 적용을 위해서는 조립공정의 자동화가 필수적이다. 또한, 유연한 와이어로 WBK 를 제작할 경우 기하학적 형상을 유지할 수 없으므로 직조기와 같은 자동화 기계의 개발이 절실하다. 이번 연구에서는, 유연한 와이어를 이용하여 WBK 를 제작하는 직조기를 설계 및 제작하였다. 이 직조기는 상부 플레이트의 회전운동과 와이어를 삽입하는 장치의 병진운동으로 작동된다. 그리고 이미 삽입된 와이어 간의 간섭을 방지하기 위한 빗살장치는 다층의 카고메망 사이에 위치된다. 또한 이 직조기는 나선형 와이어와 직선형 와이어로 구성된 semi-WBK 의 제작에도 이용될 수 있다. Wire-woven Bulk Kagome (WBK) is fabricated by assembling helically formed wires in six directions. To date, WBK samples have been assembled manually. For industrial application, the assembly process must be automated. Furthermore, if WBK is to be fabricated using flexible wires that cannot maintain their helical shape during fabrication, a specialized automatic machine, i.e., a loom needs to be developed. In this work, we designed and constructed a loom for fabricating WBKs using flexible wires. This loom is operated by one rotation of the upper plate, two translations of the insertion device, and insertion of wires. So-called “comb devices” are placed between multiple layers of Kagome nets to prevent the wires that are already in place from getting entangled with those that are being inserted. This loom can be also used to fabricate semi-WBKs composed of helically formed wires and rigid straight wires.

Wire-woven Bulk Kagome 의 압축 특성 분석

이병곤(Byung-Kon Lee),최지은(Ji-Eun Choi),전인수(Insu Jeon),강기주(Ki-Ju Kang) 대한기계학회 2008 大韓機械學會論文集A Vol.32 No.1

Periodic cellular metals (PCMs) are actively being investigated because of their excellent specific strength and stiffness, and multi-functionality such as a heat disperse structure bearing external loading. The Kagome truss PCM has been proved that it has higher resistance to plastic buckling and lower anisotropy than other truss PCMs. In this paper, the out-of-plane compressive responses of the WBK specimens have been measured, theoretically predicted and numerically analyzed. Three specimens of two-layered WBK are fabricated and tested for measuring the responses. The peak stress of compressive behavior and effective elastic modulus are predicted based on the equilibrium equation and elastic energy conservation. Moreover, the structure of the specimen is modeled using the commercial mesh generation code, PATRAN and the finite element analysis for the model under the compression is carried out using the commercial FE code, ABAQUS. Finally, the obtained results are compared with each other to analyze the compressive characteristics of Wirewoven Bulk Kagome (WBK).

WBK 의 구조적 특성에 대한 와이어 굴곡 효과

이기원(Ki Won Lee),강기주(Ki-Ju Kang) 대한기계학회 2011 大韓機械學會論文集A Vol.35 No.9

기존의 WBK(와이어 직조 카고메)의 기계적 강도와 강성은 WBK 를 구성하는 요소가 반듯하다는 가정 아래에서 계산되었다. 실제 WBK 의 요소는 3 차원 나선형상을 이루고 있어 계산된 이론 해와 실험 결과값과 차이를 보인다. 이번 연구에서는 정확한 WBK 의 기계적 강도와 강성을 위해 하나의 트러스 요소의 굴곡 효과와 브레이징 접합 부를 고려하여 계산하였다. 또한 예측한 이론 해의 검증을 위한 경계주기조건(PBC) 유한요소해석을 수행하여 실험 결과값과 비교 분석하였다. Since the mechanical strength and stiffness of wire-woven bulk Kagome (BK) have been theoretically estimated by assuming that WBK is composed of straight struts, the analytical solutions occasionally give substantial errors as compared with the experimental results. The struts of WBK are helically formed, which results in errors in the estimations In this study, for accurately predicting the mechanical properties of WBK, the effects of waviness and brazed part are taken into account for estimating the strength and stiffness of WBK. The results are compared with the measured experimental results and the results estimated by a finite element analysis performed on a unit cell under periodic boundary conditions (PBC).

벌크형 와이어 직조 카고메 트러스 PCM의 압축거동에 미치는 와이어직경/피치비의 영향

최지은(Ji-Eun Choi),주재황(Jai-Hwang Joo),강기주(Ki-Ju Kang) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5

According to pervious works, the compression, shear and bending strength of Wire-woven Bulk Kagome cellular metals are compare able to those expected for Kagome trusses with ideal configuration, which are composed of straight struts. The results could be regarded unexpected or even doubtable if it is considered that WBK is composed of curved struts and that the main failure mechanism of WBK is buckling of the struts. This work intends to answer the question about the unexpected high strength of WBK. For the purpose, geometric and material parameters related to compression strength of WBK are screened and then the effect of each parameter is evaluated by finite element analysis on the unit cell of WBK under Periodic boundary condition.

WBK의 구조적 특성에 대한 와이어 굴곡 효과

이기원(Ki Won Lee),강기주(Ki-Ju Kang) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.4

기존의 WBK(와이어 직조 카고메)의 기계적 강도와 강성은 WBK를 구성하는 요소가 반듯하다는 가정 아래에서 계산되었다. 실제 WBK의 요소는 3차원 나선형상을 이루고 있어 계산된 이론 해와 실험 결과값과 차이를 보인다. 이번 연구에서는 정확한 WBK의 기계적 강도와 강성을 위해 하나의 트러스 요소의 굴곡 효과와 브레이징 접합 부를 고려하여 계산하였다. 또한 예측한 이론 해의 검증을 위한 경계주기조건(PBC) 유한요소해석을 수행하여 실험 결과값과 비교 분석하였다. Since the mechanical strength and stiffness of WBK have been theoretically estimated on basis of assumption that WBK is composed of straight struts, the analytic solutions sometimes give substantial errors compared with experimental. Consequently, the struts of the WBK are curved, which resulted in errors in estimation based on the previous analytic solution. In this work, to predict the mechanical properties about WBK accurately, the effect of waviness and brazing paπ are taken into account to estimate the strength and the stiffness of WBK. The results are compared with those measured by experimental and estimated by finite element analysis conducted on a unit cell under periodic boundary conditions.