• 제목/요약/키워드: Localized damage

검색결과 235건 처리시간 0.021초

Effect of Localized Recrystallization Distribution on Edgebond and Underfilm Applied Wafer-level Chip-scale Package Thermal Cycling Performance

  • Lee, Tae-Kyu
    • 마이크로전자및패키징학회지
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    • 제22권1호
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    • pp.27-34
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    • 2015
  • The correlation between crack propagation and localized recrystallization are compared in a series of cross section analyses on thermal cycled edgebond and underfilm material applied wafer level chip scale package (WLCSP) components with a baseline of no-material applied WLCSP components. The results show that the crack propagation distribution and recrystallization region correlation can explain potential degradation mechanisms and support the damage accumulation history in a more efficient way. Edgebond material applied components show a shift of damage accumulation to a more localized region, thus potentially accelerated the degradation during thermal cycling. Underfilm material applied components triggered more solder joints for a more wider distribution of damage accumulation resulting in a slightly improved thermal cycling performance compared to no-material applied components. Using an analysis on localized distribution of recrystallized areas inside the solder joint showed potential value as a new analytical approach.

국부 열손상을 받은 복합재료의 탄성파특성 (Characteristics of Elastics Waves of Fiber-Reinforced Plastic with Localized Heat Damage)

  • 남기우;김영운
    • 한국해양공학회지
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    • 제16권4호
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    • pp.48-53
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    • 2002
  • Fiber-reinforced composites are extensively used in electronic, ship and aerospace applications due to their high strength and high toughess. In these applications, they are often subjected to localized heat damage due to various sources. In order to ensure their reliability, it is important to predict their residual properties using nondestructive evaluation thchniques. Fabric fiber composite specimens were manufactured with six layers of the glass-fiber prepreg and the carbon-fiber prepreg, respectively. The specimens were subjected to a localized heat damage using a heated copper tip with a diameter of 10mm at 35$0^{\circ}C$(CFRP) and 30$0^{\circ}C$(GFRP), respectively. The specimens were then subjected to tension tests while acoustic emission (AE) activities of specimens were collected. The AE activity of all specimens showed three types of distinct frequency regions. Those are matrix cracking, failure of the fiber/matrix interface and fiber breakage.

손상과 소성을 고려한 콘크리트 변형률 국소화의 유한요소해석 (Finite Element Analysis of Strain Localization in Concrete Considering Damage and Plasticity)

  • 송하원;나웅진
    • 전산구조공학
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    • 제10권3호
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    • pp.241-250
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    • 1997
  • 콘크리트에 발생하는 변형률 국소화는 연화거동에 수반하여 변형이 국부적으로 집중되는 현상으로 이를 유한요소해석 할 수 있는 일관된 알고리즘을 개발하는 것이 본 연구의 목적이다. 변형률 국소화현상이 발생한 콘크리트는 변형률이 집중되는 국소화영역과 그외의 영역인 비국소화영역으로 크게 구분할 수 있으며 국소화영역에서는 연화현상을 포함하는 탄소성거동을 하게 되며 비국소화영역은 손상제하거동을 수반하게 된다. 변형률 국소화현상이 진행중인 콘크리트의 국소화영역을 모델링하기 위하여 열역학적으로 정식화된 전형적인 소성모델에 콘크리트의 극한응력 이후에 비선형 연화로 표현되는 소성거동을 고려할 수 있는 일반화된 Drucker-Prager모델을 도입하였으며 소성이론식의 적분을 위해 return-mapping 알고리즘을 사용하고 일관된 알고리즘을 전개하였다. 또한, 콘크리트의 비국소화영역의 모델링을 위하여 열역학적 자유에너지함수를 수정하여 비선형 탄성 및 손상의 일관된 알고리즘을 전개하였다. 개발된 알고리즘에 의한 유한요소해석을 통해 압축을 받는 콘크리트 부재의 변형률 국소화 현상을 해석하였다.

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Statistics based localized damage detection using vibration response

  • Dorvash, Siavash;Pakzad, Shamim N.;LaCrosse, Elizabeth L.
    • Smart Structures and Systems
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    • 제14권2호
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    • pp.85-104
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    • 2014
  • Damage detection is a challenging, complex, and at the same time very important research topic in civil engineering. Identifying the location and severity of damage in a structure, as well as the global effects of local damage on the performance of the structure are fundamental elements of damage detection algorithms. Local damage detection is essential for structural health monitoring since local damages can propagate and become detrimental to the functionality of the entire structure. Existing studies present several methods which utilize sensor data, and track global changes in the structure. The challenging issue for these methods is to be sensitive enough in identifYing local damage. Autoregressive models with exogenous terms (ARX) are a popular class of modeling approaches which are the basis for a large group of local damage detection algorithms. This study presents an algorithm, called Influence-based Damage Detection Algorithm (IDDA), which is developed for identification of local damage based on regression of the vibration responses. The formulation of the algorithm and the post-processing statistical framework is presented and its performance is validated through implementation on an experimental beam-column connection which is instrumented by dense-clustered wired and wireless sensor networks. While implementing the algorithm, two different sensor networks with different sensing qualities are utilized and the results are compared. Based on the comparison of the results, the effect of sensor noise on the performance of the proposed algorithm is observed and discussed in this paper.

2006년 강원지역 토석류의 특성과 피해현황분석 (A Case Study on Disaster and Characteristics of Debris Flows by Heavy Localized Rainfall of Gangwon Areas in July, 2006)

  • 송평현;유병옥;정찬규;안광국;이치근
    • 기술발표회
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    • 통권2006호
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    • pp.146-155
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    • 2006
  • 2006년도 집중호우에 의해 발생된 강원도지역의 수해에 대하여 자료를 수집, 분석하였으며 수해의 발생기구 및 유형에 따른 피해정도와 저감방안에 대한 고찰을 실시하였다. 2006년 7월 15일-17일 사이의 집중적인 호우는 강원도 지역에 많은 피해를 주었는데, 특히 강원도 인제, 양양, 평창지역에서의 피해로 수십명의 인명피해와 재산피해를 발생시켰다. 최근 들어 발생되는 집중호우로 인한 피해 중 토석류에 의한 피해가 많은 이유 중에는 지구온난화로 인한 100mm에 가까운 시간당 강우량을 보이고 있어 국내에서 산악지가 형성된 구간에서는 어느 지역이나 토석류가 발생될 가능성을 지니고 있다고 할 수 있다. 그러므로 본 연구에서는 2006년 7월에 발생된 강원도 인제, 양양지역을 중심으로 토석류 피해에 대하여 자료를 수집, 분석하였으며 토석류 발생기구 및 유형에 따른 피해정도와 저감방안에 대한 고찰을 실시하였다. 앞으로 빈번해지는 토석류에 대한 관리체계의 확립 및 보완대책과 토목 공사시에 반영될 수 있는 방안 등을 모색해야 할 것이다.

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Numerical Simulation of High Velocity Impact of Circular Composite Laminates

  • Woo, Kyeongsik;Kim, In-Gul;Kim, Jong Heon;Cairns, Douglas S.
    • International Journal of Aeronautical and Space Sciences
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    • 제18권2호
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    • pp.236-244
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    • 2017
  • In this study, the high-velocity impact penetration behavior of $[45/0/-45/90]_{ns}$ carbon/epoxy composite laminates was studied. The considered configuration includes a spherical steel ball impacting clamped circular laminates with various thicknesses and diameters. First, the impact experiment was performed to measure residual velocity and extent of damage. Next, the impact experiment was numerically simulated through finite element analysis using LS-dyna. Three-dimensional solid elements were used to model each ply of the laminates discretely, and progressive material failure was modeled using MAT162. The result indicated that the finite element simulation yielded residual velocities and damage modes well-matched with those obtained from the experiment. It was found that fiber damage was localized near the impactor penetration path, while matrix and delamination damage were much more spread out with the damage mode showing a dependency on the orientation angles and ply locations. The ballistic-limit velocities obtained by fitting the residual velocities increased almost linearly versus the laminate diameter, but the amount of increase was small, showing that the impact energy was absorbed mostly by the localized impact damage and that the influence of the laminate size was not significant at high-velocity impact.

A Case of Asymptomatic, Localized, and Idiopathic Diffuse Alveolar Damage

  • Jeon, Young-Do;Hong, Christian;Joh, Joon-Sung;Jung, Ja-Young;Min, Ji-Won;Park, Seon-Young;Lee, Ga-Ram
    • Tuberculosis and Respiratory Diseases
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    • 제72권4호
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    • pp.386-389
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    • 2012
  • Diffuse alveolar damage (DAD) is a histological change in lung tissue, and is generally caused by an acute lung injury, which is characterized by bilateral and widespread damages. Localized DAD occurs very rarely. The causes for DAD are numerous, but the chief cause is acute interstitial pneumonia or acute exacerbation of idiopathic interstitial pneumonia, in cases of idiopathic manifestation. The 82-year-old patient, in this case study, showed a DAD lesion in only 1 lobe. The patient was otherwise healthy, with no previous symptoms of DAD. He was admitted to our medical center owing to localized infiltration, observed on his chest radiograph. Laboratory studies showed no signs of infections. DAD was confirmed by a surgical lung biopsy. The patient received corticosteroid treatment and had gradually improved. We report the case of a patient with localized, idiopathic DAD that cannot be classified as acute interstitial pneumonia or acute exacerbation of idiopathic interstitial pneumonia.

Hybrid infrared-visible multiview correlation to study damage in a woven composite complex-shaped specimen

  • Andrija Zaplatic;Zvonimir Tomicevic;Xuyang Chang;Ivica Skozrit;Stephane Roux;Francois Hild
    • Coupled systems mechanics
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    • 제12권5호
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    • pp.445-459
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    • 2023
  • In this study, a cyclic tensile test on a notched butterfly specimen made of woven glass fiber composite was performed on a modified Arcan fixture. During the mechanical test, the sample was monitored with a hybrid stereoscopic system comprised of two visible lights and one infrared camera. The visible light cameras were employed for kinematic measurements using a finite-element-based multiview correlation technique. A semi-hybrid correlation approach was followed, providing Lagrangian temperature fields of the Region of Interest. Due to the complex composite architecture and specimen shape, localized shearing was observed during the tensile loading. Furthermore, asymmetrical damage developed around the notches as revealed by localized strains and thermal hot spots.

지점부 부재의 부식손상에 따른 강거더 단부 지압강도 평가 (Evaluation on Bearing Capacity of End Girder Member with Local Corrosion)

  • 안진희;이원홍;김인태;정영수
    • 한국구조물진단유지관리공학회 논문집
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    • 제21권5호
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    • pp.74-82
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    • 2017
  • 강교량은 유지관리가 충분히 이루어지지 않거나, 해안 과 같이 가설위치의 환경이 고온 다습한 경우 단면에 국부적인 부식손상이 발생할 수 있다. 특히 강거더 교량 의 지점부에서는 교대부와 강거더 단부의 공간이 협소하여 상대적으로 습도가 높고 신축이음부로부터의 강우 및 동결 방지제가 누수되어 침전물을 습윤상태로 유지하게 되므로, 복부판과 지점부 보강재에 집중적으로 부식이 발생되고 있으므로 이로인한 구조성능 변화를 확인하여야 한다. 따라서 본 연구에서는 실제 발생할 수 있는 강거더 단부 복부판과 보강재의 국부부식손상을 모사한 강재 실험체를 제작하고 이에 대한 단부 지압강도 변화를 실험적으로 평가하였다. 실험결과, 국부적 부식손상은 강거더 단부의 지압강도에 영향을 주며, 특히 수직 보강재에 의한 영향이 크게 나타남을 확인하였다.

내열합금 구조품에서의 국부적 소성변형과 이중후방응력 경화 모델 (Localized Plastic Deformation in Heat-Resistant Alloy and Combined Two-Back Stress Hardening Model)

  • 윤수진;이상연;박동창;윤현걸
    • 한국추진공학회지
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    • 제15권5호
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    • pp.82-88
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    • 2011
  • 본 논문에서는 유한요소해석을 통해 연소시험 과정 중 발생한 내열 구조품의 파단현상이 분석되었다. 구조 불안정성은 소성변형으로 인한 것으로 이는 급격한 열하중의 변화에서 비롯된 것이다. 한편 소성변형 국부화 현상을 이해하기 위해 구성방정식에 연속체 파손변수가 포함되었으며 또한 Armstrong-Frederick과 Phillips 경화식을 이용, 이중후방응력 구성방정식이 제안되었다. 따라서 본 모델은 광범위한 소성변형거동을 해석할 수 있는 토대를 마련하였다. 수치해석을 통해 소성변형 집중 현상은 지배적인 후방응력의 전개에 의존하는 것으로 나타났다. 또한 물체 내에서의 파손 현상은 소성변형 집중을 가속화하는 것으로 밝혀졌다.