• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2007년도 춘계학술대회A
• /
• pp.1690-1695
• /
• 2007

Lightweight metallic truss structures with open, periodic cell are currently being investigated because of their multi-functionality such as thermal management and load bearing. The Kagome truss PCM has been proved that it has higher resistance to plastic buckling, more plastic deformation energy and lower anisotropy than other truss PCMs. The subject of this paper is an examination of the failure mechanism of Wire woven Bulk Kagome(WBK). To address this issue, the out-of-plane compressive responses of the WBK has been measured and compared with theoretical and finite element (FE) predictions. For the experiment, 2 multi-layered WBK are fabricated and 3 specimens are prepared. For the theoretical analysis, the brazed joints of each wire in WBK are modeled as the pin-joint. Then, the peak stress of compressive behavior and elastic modulus are calculated based on the equilibrium equation and energy method. The mechanical structure with five by five cells on the plane are constructed is modeled using the commercial code, PATRAN 2005. and the analysis is achieved by the commercial FE code ABAQUS version 6.5 under the incremental theory of plasticity.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2008년도 추계학술대회A
• /
• pp.13-19
• /
• 2008

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.

• 대한기계학회논문집A
• /
• 제31권6호
• /
• pp.694-700
• /
• 2007

Recently, a new cellular metal, WBK(Wire woven Bulk Kagome) has been introduced. WBK is fabricated by assembling metal wires in six directions into a Kagome-like truss structure and by brazing it at all the crossings. Wires as the raw material are easy to handle and to attain high strength with minimum defect. And the strength and energy absorption are superior to previous cellular metals. Therefore, WBK seems to be promising once the fabrication process for mass production is developed. In this paper, an upper bound solution for the mechanical properties of the bulk WBK under compression is presented. In order to simulate uniform behavior of WBK consisted of perfectly uniform cells, a unit cell of WBK with periodic boundary conditions is analyzed by the finite element method. In comparison with experimental test results, it is found that the solution provides a good approximation of the mechanical properties of bulk WBK cellular metals except for Young's modulus. And also, the brazing joint size does not have any significant effect on the properties with an exception of an idealized thin joint.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2007년도 춘계학술대회A
• /
• pp.1410-1415
• /
• 2007

Recently introduced WBK(Wire-wounded Bulk Kagome) shows relatively superior mechanical properties compared to other types of PCM. WBK is fabricated by assembling helical wires in 6 directions. Wire being a helix, the wire's geometric properties like pitch and helical radius shows certain geometric characteristics which can play some critical role in setting up an automatic fabrication process. In this study, geometry of WBK is modeled by various transformations of a piece of helical wire and the characteristics of the geometry of an element of WBK truss are discussed. In addition, the roles of pitch and helical radius of wire in optimizing the assembling process are described and the derivation of criteria is attempted to decide proper helical radius which would maintain minimal interference between wires at the crossings.

• 대한기계학회논문집A
• /
• 제33권4호
• /
• pp.353-359
• /
• 2009

Wire-woven Bulk Kagome (WBK) is a new truss type cellular metal fabricated by systematic assembling of helical wires in six directions. In this work, the experiments of mechanical behaviors of WBK cored sandwich panels subjected to bending load were performed and the results were compared with those by the corresponding analytic solutions. And also, finite element simulations were performed to validate the optimal design according to the analytic solutions. It is found the sandwich panel with WBK core performed excellently in terms of energy absorption and deformation stability after the peak point as well as the load capacity.

• Elastomers and Composites
• /
• 제51권4호
• /
• pp.275-279
• /
• 2016

Additive manufacturing or 3D printing is a new manufacturing process and its application is getting growth. However, the product qualities such as mechanical strength, dimensional accuracy, and surface quality are low compared with conventional manufacturing process such as molding and machining. In this study not only mechanical characteristics of polymer sandwich panel having three dimensional core layer but also mechanical characteristics of core layer itself were analyzed. The shape of three dimensional core layer was pyramidal kagome structure. This core layer was fabricated by two different methods, injection molding with PP resin and material jetting type 3D printing with acrylic photo curable resin. The material for face sheets in the polymer sandwich panel was PP. Maximum load, stiffness, and elongation at break were examined for core layers fabricated by two different methods and also assembled polymer sandwich panels. 3D printed core showed brittle behavior, but the brittleness decreased in polymer sandwich panel containing 3D printed core. The availability of 3D printed article for the three dimensional core layer of polymer sandwich panel was verified.

• 대한기계학회논문집A
• /
• 제34권9호
• /
• pp.1235-1240
• /
• 2010

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 WBK를 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 작동 된다. 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.

• Structural Engineering and Mechanics
• /
• 제45권4호
• /
• pp.439-454
• /
• 2013

Hollow cylindrical tubes with a prismatic sandwich lining designed to replace the solid cross-sections are studied in this paper. The sections are divided by a number of revolving periodic unit cells and three topologies of unit cells (Square, Triangle and Kagome) are proposed. Some types of multiple-topology designed materials are also studied. The feasibility and accuracy of a homogenization method for obtaining the equivalent parameters are investigated. As the curved elements of a unit cell are represented by straight elements in the method and the ratios of the lengths of the curved elements to the lengths of the straight elements vary with the changing number of unit cells, some errors may be introduced. The frequencies of the first five modes and responses of the complete and equivalent models under an internal static pressure and an internal step pressure are compared for investigating the scope of applications of the method. The lower bounds and upper bounds of the number of Square, Triangular and Kagome cells in the sections are obtained. It is shown that treating the multiple-topology designed materials as a separate-layer structure is more accurate than treating the structure as a whole.

• 한국구조물진단유지관리공학회 논문집
• /
• 제23권2호
• /
• pp.84-91
• /
• 2019

최근 들어 우리나라에서도 설치와 유지관리가 용이하며 경제성이 뛰어난 강재이력형 감쇠장치를 적용하여 내진성능을 확보하고자 하는 건물들이 다수 건설되고 있다. 하지만 이러한 강재이력형 감쇠장치가 철근콘크리트 건물에 적용되는 경우 감쇠장치를 설치하기 위한 연결구조물은 전체적인 시스템을 복잡하게 만들어 감쇠장치의 신뢰도를 저하시키는 요소가 되기도 한다. 이에 본 연구에서는 기존연구에서 개발된 카고메 감쇠장치를 대상으로 별도의 연결구조 없이 철근콘크리트 지지구조물에 감쇠장치를 직접 매립할 수 있는 시스템을 제안하고자 하며, 매립길이에 따른 내진거동을 확인하여 동 시스템의 정립을 위한 기초자료를 제공하고자 한다. 실험결과, $1.0l_d$ 매립길이 실험체의 경우 카고메 감쇠장치 매립부분에서 콘 파괴와 유사한 형태의 뽑힘이 발생하였다. 반면, $2.0l_d$ 매립길이를 확보한 실험체는 실험 종료 시까지 뽑힘 및 콘 파괴 없이 안정적인 이력거동을 나타내었고 $1.0l_d$ 매립길이 대비 $2.0l_d$ 매립길이가 약 1.3배의 향상된 에너지소산능력을 나타내었다. 본 연구에서 제안하는 시스템을 적용할 경우, 기존 설치방법 변경에 따른 기타 철물 제작 비용을 줄일 수 있으며, 시공 시에도 부수적인 철물 시공을 줄여 공기를 단축할 수 있다.

• 대한기계학회논문집A
• /
• 제41권8호
• /
• pp.737-744
• /
• 2017

최근 Shellular라는 새로운 극저밀도 재료가 소개되었다. Shellular는 주기적 구조를 가지면서도 한장의 부드러운 곡면의 쉘로 구성되어 있다. 최초의 Shellular는 리쏘그래피를 이용하여 제조되며 3주기최소곡면의 일종인 P-곡면과 유사한 형태를 갖는다. 본 연구에서는 와이어 직조에 기반하여 D-곡면과 유사한 Shellular를 제작하는 새로운 방법을 제시한다. 실험과 유한요소해석을 통하여 압축하중 하의 재료물성을 평가하고 종래의 극저밀도 재료와 비교하였다.