• Title/Summary/Keyword: micro-cracks

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Micro-crack Detection in Silicon Solar Wafer through Optimal Parameter Selection in Anisotropic Diffusion Filter (비등방 확산 필터의 최적조건 선정을 통한 태양전지 실리콘 웨이퍼의 마이크로 크랙 검출)

  • Seo, Hyoung Jun;Kim, Gyung Bum
    • Journal of the Semiconductor & Display Technology
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    • v.13 no.3
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    • pp.61-67
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    • 2014
  • Micro-cracks in crystalline silicon wafer often result in wafer breakage in solar wafer manufacturing, and also their existence may lead to electrical failure in post fabrication inspection. Therefore, the reliable detection of micro-cracks is of importance in the photovoltaic industry. In this paper, an experimental method to select optimal parameters in anisotropic diffusion filter is proposed. It can reliably detect micro-cracks by the distinct extension of boundary as well as noise reduction in near-infrared image patterns of micro-cracks. Its performance is verified by experiments of several type cracks machined.

The analysis of electrical characteristics with Micro-crack in PV module (Micro-cracks에 의한 PV 모듈의 전기적 특성 분석)

  • Song, Young-Hun;Ji, Yand-Geun;Kim, Kyung-Soo;Kang, Gi-Hwan;Yu, Gwon-Jong;Ahn, Hyung-Gun;Han, Deuk-Young
    • 한국태양에너지학회:학술대회논문집
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    • 2011.04a
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    • pp.25-30
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    • 2011
  • In this paper, we analyzed the electrical characteristics with Micro-cracks in Photovoltaic module. Micro cracks are increasing the breakage risk over the whole value chine from the wafer to the finished module, because the wafer or cell is exposed to mechanical stress. And The solar cells have to with stand the stress under out door operation in the finished module. Here the mechanical stress is induced by temperature changes and mechanical loads from wind and snow. So, we experimentally analyze the direct impact of micro-cracks on the module power and the consequences after artificial aging. The first step, we made micro-cracks in PV module by mechanical load test according to IEC 61215. Next, PV modules applied the thermal cycling test, because micro-cracks accelerated aging by thermal cycling test, according to IEC61215. Before every test, we checked output and EL image of PV module. As the result of first step, we detected little power loss(0.9%). But after thermal cycling test increased power loss about 3.2%.

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The analysis of growth and electrical characteristics of micro-crack with thermal effect in PV module (PV 모듈에서 온도 영향에 의한 micro-crack 성장과 전기적 특성 분석)

  • Song, Young-Hun;Kang, Gi-Hwan;Yu, Gwon-Jong;Ahn, Hyung-Gun;Han, Deuk-Young
    • Proceedings of the KIEE Conference
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    • 2011.07a
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    • pp.1318-1319
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    • 2011
  • In this paper, we analyzed of growth and electrical characteristics of micro-cracks with thermal effect in PV module. The micro-cracks are increasing the breakage risk over the whole value chine from the wafer to the finished module, because the wafer or cell is exposed to mechanical stress. we experimentally analyze the direct impact of micro-cracks on the module power and the consequences after artificial aging. The first step, we made micro-cracks in PV module by mechanical load test according to IEC 61215. Next, PV modules applied the thermal cycling test, because microcracks accelerated aging by thermal cycling test. according to IEC61215. Before every test, we checked output and EL image of PV module.

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Effect of thermal-induced microcracks on the failure mechanism of rock specimens

  • Khodayar, Amin;Nejati, Hamid Reza
    • Computers and Concrete
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    • v.22 no.1
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    • pp.93-100
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    • 2018
  • It is seldom possible that geotechnical materials like rocks and concretes found without joints, cracks, or discontinuities. Thereby, the impact of micro-cracks on the mechanical properties of them is to be considered. In the present study, the effect of micro-crack on the failure mechanism of rock specimens under uniaxial compression was investigated experimentally. For this purpose, thermal stress was used to induce micro-cracks in the specimens. Several cylindrical and disk shape specimens were drilled from granite collected from Zanjan granite mine, Iran. Some of the prepared specimens were kept in room temperature and the others were heated by a laboratory furnace to different temperature levels (200, 400, 600, 800 and 1000 degree Celsius). During the experimental tests, Acoustic Emission (AE) sensors were used to monitor specimen failure at the different loading sequences. Also, Scanning Electron Microscope (SEM) was used to distinguish the induced micro-crack by heating in the specimens. The fractographic analysis revealed that the thin sections heated to $800^{\circ}C$ and $1000^{\circ}C$ contain some induced micro-fractures, but in the thin sections heated to $200^{\circ}C$, $400^{\circ}C$ and $600^{\circ}C$ have not been observed any micro-fracture. In the next, a comprehensive experimental investigation was made to evaluate mechanical properties of heated and unheated specimens. Results of experimental tests showed that induced micro-cracks significantly influence on the failure mode of specimens. The specimens kept at room temperature failed in the splitting mode, while the failure mode of specimens heated to $800^{\circ}C$ are shearing and the specimens heated to $1000^{\circ}C$ failed in the spalling mode. On the basis of AE monitoring, it is found that with increasing of the micro-crack density, the ratio of the number of shear cracks to the number of tensile cracks increases, under loading sequences.

Behavior of Fatigue Crack Propagation from Surface Flaw (表面欠陷 에 發생하는 疲勞크랙擧動)

  • 송삼홍;오환섭
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.9 no.2
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    • pp.150-157
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    • 1985
  • In terms of behavior of fatigue cracks propagated after build-up around the artificial drilled miro-hole, this study has been made of the build-up process of slips and micro cracks, behavior of micro-crack propagation and the definition of fatigue limit under the rotating bending stress with low carbon steel. The results of this study are as follows: (1) The fatigue limit is the repropagating critical stress for the nonpropagating cracks which have grown to some limit around the micro-hole in regard of the magnitude of micro-hole. (2) Behavior of the slips and micro-cracks initiation are occurring simultaneously in front and in rear of micro-hole tips in the view of the rotational direction, regardless of the magnitude of micro-hole. (3) Behavior of fatigue crack propagation is different from magnitude of micro-hole, its behavior is propagation of single crack about respectively large hole, but about respectively small hole, fatigue crack propagated joining phenomena of micro-cracks. (4) The behavior of fatigue fracture is affected by the factor of its defects in the view of magnitude of micro-hole when the diameter of the micro-holes are smaller than 50.mu.m, and this is also affected with the size effect of micro-hole diameter.

A Study on Classification of Micro-Cracks in Silicon Wafer Through the Fusion of Principal Component Analysis and Neural Network (주성분분석과 신경회로망의 융합을 통한 실리콘 웨이퍼의 마이크로 크랙 분류에 관한 연구)

  • Seo, Hyoung Jun;Kim, Gyung Bum
    • Journal of the Korean Society for Precision Engineering
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    • v.32 no.5
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    • pp.463-470
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    • 2015
  • Solar cell is typical representative of renewable green energy. Silicon wafer contributes about 66 percent to its cost structure. In its manufacturing, micro-cracks are often occurred due to manufacturing process such as wire sawing, grinding and cleaning. Their detection and classification are important to process feedback information. In this paper, a classification method of micro-cracks is proposed, based on the fusion of principal component analysis(PCA) and neural network. The proposed method shows that it gives higher results than single application of two methods, in terms of shape and size classification of micro-cracks.

Analysis of the stress disribution around flaws and the interaction effects between fatigue cracks by finite element method (유한요소법에 의한 결함 주위의 응력분포와 피로크랙의 간섭효과)

  • Song, S.H.;Kim, J.B.
    • Journal of the Korean Society for Precision Engineering
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    • v.12 no.2
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    • pp.154-161
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    • 1995
  • In order to analysis of the stress distribution around flaws and the interaction effects between fatigue cracks, stress around micro hole was analyzed by Finite Element Method(F.E.M.) and micro hole specimens were tested using rotary bending fatigue machine and twisting fatigue machine to identify stress effects for fatigue cracks initiating from micro holes and interaction effects between micro holes. The results are as follows : Interaction effects of .sigma. $_{y}$for the micro hole side is larger than the large micro hole side when the interval between micro holes is near. Stress concentration factor increase as the diameter of micro hole becomes smaller. But, stress field of micro hole is smaller than that of large micro hole at h .leq. r (h:depth of micro hole, r:radius of micro hole) and that of large hole is larger than that of small micro hole at h >r expect the small range from micro hole.e.

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A Study on the Design of Fatigue Strength using Fractal Character of Surface Micro-crack (표면미소균열의 프랙탈 특성을 이용한 피로강도설계에 관한 연구)

  • Cho, Seok-Swoo;Joo, Won-Sik
    • Journal of the Korean Society for Precision Engineering
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    • v.16 no.12
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    • pp.143-151
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    • 1999
  • The shape of surface micro-crack is very irregular due to nonhomogeneous microstructure but is very important in respect to qualitative estimation of fatigue life. Fractal geomety can quantify the shape of surface mciro-crack. Fractal dimension is measured for surface micro-cracks with coast line and box counting method and estimates cycle ration in Al 2024-T3. The average fractal dimension $D_{favg}$ of surface micro-cracks has 3-parameter weibull distribution and location parameter is nearly constant but shape parameter decreases as cycle ration increases. The fractal dimension by coast line method is measured for individual surface micro-crack but the fractal dimension by box countin method is measured for all the surface micro-cracks under sampling area. Therefore, This paper shows fractal dimension $D_{fb}$ can predict cycle ratio $N/N_f$ more convenient than fractal dimension $D_{favg}$.

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Micro-Surface-Cracks Behavior of 304 Stainless Steel Under Creep-Fatigue Interaction at Elevated Temperature (고온하 304 스테인리스강의 크리프-피로상호작용하의 미소표면균열에 관한 파괴거동)

  • 서창민;이상돈;조일현
    • Journal of Ocean Engineering and Technology
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    • v.2 no.2
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    • pp.104-111
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    • 1988
  • This paper deals with the micro-surface-cracks behavior on the unnotched smooth specimens of Type 304 stainless steel at $593^{\circ}C$ in air under creep and creep-fatigue conditions that have 10 mim and 1 min load holding times respectively. The behaviors of the micro-surface-cracks have been visualized by means of surface replica method and optical micro-photography. The quantitative characteristics of initiation, growth and coalescence of micro-surface-cracks have been investigated by observing and measuring the crack growth behaviors. some of the important results are as follows: Main crack initiates at grain boundary in the early stage(10 to 20%)of its life time and grows through coalescence and finally leads to fracture. The distribution of micro-surface-crack length, 2a, can be plotted against the composite Weibull distribution. The growth rate of the main crack can be plotted against the stress intensity factor, crack tip opering displacement and J integral.

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Micro-Cracks Control of LB-DECK Using Polymer Cement Concrete (폴리머 시멘트 콘크리트를 이용한 LB-DECK의 미소균열 제어)

  • Lho, Byeong-Cheol;Choi, Jong-Yun;Cho, Gyu-Dae;Choi, Jong-Gwon
    • Journal of the Korea Concrete Institute
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    • v.24 no.2
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    • pp.103-109
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    • 2012
  • Micro-cracks with a width less than 0.1 mm in precast concrete panels do not cause structural problem, but they can cause problems in long term durability and concrete surfaces aesthetic, requiring additional repair costs. In this paper, polymer cement concrete is used to increase flexural tensile strength and to prevent micro-cracks due to construction loads on LB-DECK panels. Using 5% polymer-cement ratio, the panel crack moment is increased by improving flexural tensile strength and controlling visible micro-cracks during construction stage of LB-DECK.