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이병곤 ( Byung Kon Lee ),이학구 ( Hak Gu Lee ),이상복 ( Sang Bok Lee ),이원오 ( Won Oh Lee ),이진우 ( Jin Woo Yi ),엄문광 ( Moon Kwang Um ),김병선 ( Byung Sun Kim ),변준형 ( Joon Hyung Byun ) 한국복합재료학회 2010 Composites research Vol.23 No.3
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 multilayered 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.
Bulk PCMs composed of helically formed Kagome truss were investigated on the characteristics of compressive behavior. In this work, different number of layers, slenderness ratio and specimen configurations such as pointed faced and flat faced were experimentally and theoretically measured under compression. When the number of layers increases, the strength slowly decreases because of imperfection existing in the specimens. The compressive strength of the bulk PCMs depended on the slenderness ratio rather than number of layers and the wire diameter, the strut length. For the pointed faced specimen the stress level tends to keep increasing more rapidly with the slenderness ratio, while for the flat faced specimens it has the peak earlier and then monotonically decreases until densification becomes in effect.
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).
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최근 산업 발전에 따라 회전기기에 대한 수요 증가와 더불어 사고 발생률도 크게 높아졌으며, 이들 문제에 대한 해결 방안으로 지능형 결함 진단이 대두되었다. 이에 본 논문에서는 회전기기 부품들 중 손상 발생 빈도수가 높은 회전체를 대상으로 진단 알고리즘에 입력되는 특징 파라미터들을 제시하였다. 이를 위해서, 원자력발전소의 펌프 고장 이력 자료로부터 대표적 결함 유형 9가지를 선정하였고, 현장 신호 확보의 어려움으로 모사 실험을 수행하였다. 특징적인 결함 신호 패턴을 정량화시키기 위해 가속도 신호로부터 총 84개의 통계 파라미터를 계산하였고, Z-SCORE법을 이용하여 통계 파라미터들 각각의 결함 식별 능력을 평가하였다. 그리고 서포트벡터머신을 이용한 결함 분류 상태 확인을 통해 RAW-P7, RAW-P8, RAW-P4, WT2-NNL, WT2-EE 파라미터들이 회전체 진단에 우수한 특징 파라미터임을 제안하였다. Recently, uses of rotating machinery have been increased sharply and failure occurrence also was significantly increased along with the industrial development. To solve these problems, intelligent fault diagnosis was tried. In this paper, feature parameters for the rotor with high frequency of failure occurrence, which are used as algorithm input, were suggested. To do this, 9 fault types from pump historical failure data of nuclear power plants were selected and simulation testing was performed. Total 84 statistical parameters were calculated to quantify fault signal pattern from the acceleration signal and fault discrimination capability for each parameter was evaluated by using the Z-SCORE method. Finally, RAW-P7, RAW-P8, RAW-P4, WT2-NNL, WT2-EE through verification of fault classification status using the SVM were proposed as the superior parameters for intelligent fault diagnosis of rotor.
Mechanical seals are one of main components of high speed centrifugal pumps. So, it is very important to detect the faults of mechanical seals since the damage of seal can cause a critical failures of accidents of machinery system. In the past, many researchers mainly performed to detect the seal fault using the time signals measured from sensors. Recently, studies are focused on the development of on-line real time monitoring system. But sutyd on the feature perameters used fault detection of mechanical seals has a little been performed. In theis paper, we showed feature parameters extracted from accelerated and acoustic signals by using the discrete wavelet tansform, alpha coefficient, statistical parameters. And also verified the possibility for fault detection of mechanical seal.
Mechanical seals are one of main components of high speed centrifugal pumps. So, it is very important to detect the faults (scratch, notch, indentation, wear) of mechanical seals since the damage of seal can cause a critical failures or accidents of machinery system. In the past, many researchers mainly performed to detect the seal fault using the time signals measured from sensors. Recently, studies are focused on the development of on-line real time monitoring system. But study on the feature parameters used for fault detection of mechanical seals has a little been performed. In this paper, we showed feature parameters extracted from accelerated and acoustic signals by using the discrete wavelet transform (DWT), alpha coefficient, statistical parameters. And also verified the possibility for fault detection of mechanical seal
This study suggests a new type of wire-woven bulk kagome (WBK) structures constituting of helically woven tube-wires. The present work consists of two parts; the experiments and the numerical analysis. In the numerical simulation, to implement the compression behavior of tube-WBK trusses, the numerical model is postulated with perfect unit cells and specified by appropriate boundary conditions. Two different tube-wires are introduced to check the mechanical compression behavior under compression. In the experiment, the uniaxial compression test is fulfilled by a universal testing machine with the same dimension of numerical models, and then the stress-strain curve is calculated from the measured displacement of tube-WBKs. From the comparisons between the prediction of finite element analyses and the experimental data for tube-wires, this work finds that the mechanical compression behavior of tube-WBKs is considerably dependent on the geometry of helically woven tube-wires.