• 제목/요약/키워드: Elastic Rate

검색결과 609건 처리시간 0.029초

Mechanical analysis of non-uniform beams resting on nonlinear elastic foundation by the differential quadrature method

  • Hsu, Ming-Hung
    • Structural Engineering and Mechanics
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    • 제22권3호
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    • pp.279-292
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    • 2006
  • A new approach using the differential quadrature method (DQM) is derived for analysis of non-uniform beams resting on nonlinear media in this study. The influence of velocity dependent viscous damping and strain rate dependent viscous damping is investigated. The results solved using the DQM have excellent agreement with the results solved using the FEM. Numerical results indicated that the DQM is valid and efficient for non-uniform beams resting on non-linear media.

철근콘크리트뼈대 구조물의 정적 비선형 해석에 관한 연구 (A Study on the Nonlinear Analysis of R/C Frames Structures subjected to Static Loads)

  • 심종성;조민수
    • 한국콘크리트학회:학술대회논문집
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    • 한국콘크리트학회 1992년도 가을 학술발표회 논문집
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    • pp.196-201
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    • 1992
  • The purpose of this study is to develop the computer software for the nonlinear analysis of R/C frame structure under static loads. For this purpose, strain-rate dependant material model and physical element model considering both flexural and shear deformation are adopted and they are connected with 'TWO-D'which is commerical software for elastic structural analysis. The analytical results using the developed software are compared to the experiment results and they are generally satisfactory.

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복합재료의 피로수명 해석 (Fatigue Life Analysis of Composite Materials)

  • 이창수;황운봉;박현철;한경섭
    • 한국복합재료학회:학술대회논문집
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    • 한국복합재료학회 1999년도 추계학술발표대회 논문집
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    • pp.268-271
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    • 1999
  • Fatigue life Prediction is investigated analytically based on the fatigue modulus concept. Fatigue modulus degradation rate at any fatigue cycle was assumed as a power function of number of fatigue cycles. New stress function describing the relation of initial fatigue modulus and elastic modulus was used to account for material non-linearity at the first cycle. It was assumed that fatigue modulus at failure is proportional to applied stress level. A new fatigue life prediction equation as a function of applied stress is proposed. The prediction was verified experimentally using cross-ply carbon/epoxy laminate (CFRP) tube.

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강도적 불균질을 갖는 구조물의 동적하중하에서의 연성크랙 발생조건 (Criterion for ductile crack initiation with strength mismatch under dynamic loading)

  • 안규백;일본명;일본명;방한서;일본명
    • 대한용접접합학회:학술대회논문집
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    • 대한용접접합학회 2003년도 추계학술발표대회 개요집
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    • pp.179-181
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    • 2003
  • The present study focuses on the effect of geometrical discontinuity, strength mismatch, which can elevate plastic constraint due to heterogeneous plastic straining, and loading rate on the ductile crack initiation using two-parameter criterion. Fracture initiation testing has been conducted under static and dynamic loading using circumferentially notched round-bar specimens. In order to evaluate the stress/strain state in the specimens, especially under dynamic loading, a thermal elastic-plastic dynamic finite element (FE) analysis considering the temperature rise due to plastic deformation has been carried out.

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Reliability of an elastic bar under tension in a corrosive environment

  • Elishakoff, Isaac;Soret, Clement
    • Ocean Systems Engineering
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    • 제2권3호
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    • pp.173-187
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    • 2012
  • In this study we investigate the reliability of a bar subjected to a random tensile load in presence of corrosion. We consider linear, quadratic and exponential models that connect the stress in the bar with the corrosion rate. Two probability densities are considered for the load, with attendant derivation of the time-dependant reliability. The design time of operation is determined utilizing the requirement that the reliability must not be less than the required value.

Sodium Alginate-$CaSO_4{\cdot}1/2H_2O$ 彈性體의 生成速度 및 彈性에 미치는 金屬酸化物의 影響 (The Effect of Metallic Oxides on the Formation Rates and Rigidities of the Elastic Sodium Alginate-$CaSO_4{\cdot}1/2H_2O$ Gel.)

  • 신홍대;허연;김은식
    • 대한화학회지
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    • 제9권1호
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    • pp.16-22
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    • 1965
  • Sodium alginate-$CaSO_4{\cdot}$1/2 $H_2O$의 gel에 미치는 alkali鹽의 遲延효果를 Miyake date와 比較하고, Schwedoff法을 改良한 連續的 測定方法을 써서, 金屬酸化物의 添加에 依한 彈性 gel의 生成速度 및 彈性의 變化를 硏究하였다. 즉 (1) sample의 張力變化를 連續的으로 測定하여, sodium alginate와 $CaSO_4{\cdot}$1/2 $H_2O$ aqueous sol의 gel化 過程을 觀察하였다. (2) 彈性 gel의 生成速度에 미치는 $Na_3PO_4$의 遲延효果는 $Na_2CO_3$보다 크다는 點에서는 Miyake 報告와 一致하였으나, Miyake date처럼 兩者間에 그리 큰 差가 없었다. (3) 金屬酸化物이 彈性 gel生成速度에 미치는 影響에 어떤 規則性은 없었지마는 $SiO_2$와 MgO는 比較的 큰 速度增大효果를 나타내고 ZnO는 比較的 적었다. 그러나 $Al_2O_3$, $Sb_2O_3$$TiO_2$는 速度低下효果를 나타냈다. 結果的으로 酸化物의 種類나 그 添加量에 따라 어떤 明確한 規則性을 觀察하지 못하였다. (4) 彈性率과 生成速度에 미치는 효果사이에 比例關係는 없없으나 金屬酸化物을 添加하면 一般的으로 彈性率이 增加하였다. 이들 酸化物 中에서 彈性率增大효果가 가장 큰 것은 MgO였다.

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한.EU간 통상환경변화가 수출에 미치는 영향 (A Study on the Effects of Export in the Change on Trade Enviroment of Korea-EU)

  • 최창열;최혁준
    • 통상정보연구
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    • 제7권3호
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    • pp.269-286
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    • 2005
  • The exchange rate volatility has been increased since the time when the floating exchange rate system was introduced in Korea. As a result, the increase of the exchange rate volatility raised the risk in international trades in Korea. The purpose of this study in to study the feature of exchange rate volatility and the main sources of its increase and to confirm whether the exchange rate volatility influence export volume and price of Korea. In the first place, I measured exchange rate volatility with two methods. The one is descriptive statistic method such as the width of daily exchange rate fluctuation and the rate of exchange rate devaluation. The other is the time varying conditional variance of exchange rate. Then, I studied the sources of exchange rate volatility. In the second place, I defined the exchange rate volatility as the time varying conditional variance and estimated it by using elastic a approach model which shows exchange rate is affected by itself and its conditional variance, I estimated its effects on export volumes and prices of electric home appliances, information & communication equal and semi-conductor. The result of this study is as follows. With presumed result EU and Korea because is not the goods which is to substantial competition relationship, The effect where the relative value change of presumed result expression anger and the dollar of import and export function goes mad to the import and export of Korea the income compared to is to export and it is appearing a lot. The EU goods is sold more expensively the Korean goods than from about length being caused by American market of the dollar and the balance of trade of Korea is visible like being visible the improvement of single breadth. Because the relationship of competition is weak but substantially there is to a short term and expression - the effect where the dollar rate fluctuation is big in Korean trade there is a possibility of saying that widely known it is not.

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다이접착필름용 조성물의 탄성 계수 및 경화 특성 최적화 (Optimization of Elastic Modulus and Cure Characteristics of Composition for Die Attach Film)

  • 성충현
    • 한국산학기술학회논문지
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    • 제20권4호
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    • pp.503-509
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    • 2019
  • 더욱 작고 얇고 빠르며, 많은 기능을 가진 모바일 기기에 대한 요구가 그 어느 때보다 높다. 이에 대한 기술적 대응의 하나로 여러 개의 칩을 적층하는 Stacked Chip Scale Package(SCSP)가 어셈블리 업계에서 사용되고 있다. 다수의 칩을 접착하는 유기접착제로는 필름형 접착제인 die attach film(DAF)가 사용된다. 칩과 유기기판의 접착의 경우, DAF가 기판의 단차를 채우기 위해서는 고온에서 높은 유동성이 요구된다. 또한 와이어 사이를 채우면서 고용량 메모리와 같이 동일한 크기의 칩을 접착하는 DAF의 경우에도, 본딩 온도에서 높은 유동성이 요구된다. 본 연구에서는 DAF의 주요 원재료 3성분에 대한 혼합물 설계 실험계획법을 통하여 고온에서 낮은 탄성계수를 갖도록 최적화하고, 이에 따른 점착 특성 및 경화 특성을 평가하였다. 3성분은 아크릴 고분자(SG-P3)와 연화점이 다른 두 개의 고상에폭시 수지(YD011과 YDCN500-1P)이다. 실험계획법 평가 결과에 따르면, 고온에서는 아크릴 고분자 SG-P3의 함량이 작을수록 탄성계수가 작은 값을 나타내었다. $100^{\circ}C$에서의 탄성계수는 SG-P3의 함량이 20% 감소한 경우, 1.0 MPa에서 0.2 MPa 수준으로 감소하였다. 반면, 상온에서의 탄성계수는 연화점이 높은 에폭시 YD011에 의해 크게 좌우되었다. 최적 처방은 UV 다이싱 테이프를 적용시 98.4% 수준의 비교적 양호한 다이픽업 성능을 나타냈다. 유리칩을 실리콘 기판에 부착하고 에폭시를 1단계 경화시킨 경우, 크랙이 발생하였으나, 아민 경화 촉진제의 함량 증가와 2단계 경화를 통하여 크랙의 발생을 최소화할 수 있었다. 이미다졸계 촉진제가 아민계 촉진제에 비해 효과가 우수하였다.

Mechanisms of Platelet Adhesion on Elastic Polymer Surfaces: Protein Adsorption and Residence Effects

  • Insup Noh;Lee, Jin-Hui
    • Macromolecular Research
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    • 제9권4호
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    • pp.197-205
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    • 2001
  • Platelet adhesion onto elastic polymeric biomaterials was tested in vitro by perfusing human whole blood at a shear rate of 100 sec$\^$-1/ for possible verification of mechanisms of initial platelet adhesion perfusion of blood on the polymeric substrates was performed after treatments either with or without pre-adsorption of 1% blood plasma, and either with or without residence of the protein-preadsorbed substrate in phosphate buffered solution. The surfaces employed were elastic polymers such as poly(ether urethane urea), poly(ether urethane), silicone urethane copolymer, silicone rubber and poly(ether urethane) with the anti-calcifying agent hydroxyethane bisphosphate. Each polymer surface treated was exposed in vitro to the dynamic, heparinized whole blood perfused for upto 6 min and the surface area of platelets initially adhered was measured by employing in situ epifluorescence video microscopy. The blood perfusion was performed on the surfaces treated at the following three different conditions: directly on the bare surfaces, after protein pre-adsorption and after residence in buffer for 3 days of the surfaces protein pre-adsorbed for 2 h. The effects of blood plasma pre-adsorption on the initial platelet adhesion was surface-dependent. The amount of the adsorbed fibrinogen and the surface coverage area of the adhered platelets were dependent on the surface conditions whether substrates were bare surfaces or protein pre-adsorbed ones. To test an effect of possible morphological (re)orientations of the adsorbed proteins on the initial platelet adhesion, the polymeric substrate pre-adsorbed with 1% blood plasma was immersed in phosphate buffered solution for 3 days and then exposed to physiological blood perfusion. The surface area of the platelets adhered on these surfaces was significantly different from that of the surfaces treated with protein pre-adsorption only. These results indicated that platelet adhesion was dependent on the surface property itself and pre-treatment conditions such as blood perfusion without any pre-adsorption of proteins, and blood perfusion either after protein pre-adsorption or after subsequent substrate residence in buffer of the substrate pre-adsorbed with proteins. Understanding of these results may guide for better designs of blood-contacting materials based on protein behaviors.

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반복하중조건 하에서의 S45C 탄소강에 대한 미소피로균열 성장속도 해석의 수정 (A Modification in the Analysis of the Growth Rate of Short Fatigue Cracks in S45C Carbon Steel under Reversed Loading)

  • ;신용승
    • Journal of Welding and Joining
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    • 제13권2호
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    • pp.96-105
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    • 1995
  • 본 연구에서는 종래의 미소피로균열 성장속도 해석방법에 대한 수정안을 제시하고 수정 후의 방 법에 의해서 계산한 값들과 S4SC 탄소강에 대한 Nisitani와 Goto의 실험결과를 비교하여 계산한 값과 실험데이터 사이에 양호한 일치가 있음을 보였다. 이미 제시된 피로균열성장속도 식에는 하한계수준과 피로한도를 연관시키는 재료상수와 탄소성 거동에 대한 수정 및 균열닫힘효과를 나타내는 방법이 포함되어 있다. 본 연구에서 행한 수정중의 하나는 기하학적인 상수대신에 퍼만(Forman)의 탄성응력 강도계수 범위식을 이용하는 것이고, 다른 하나는 균열이 성장함에 따라 편심형단면으로 되면서 모멘트에 기인해 발생되는 굽힘효과를 고려하는 것이다. 이 방 법을 수명예측에 사용하면 용접구조물은 물론 기계구조물의 보다 정확한 수명예측이 가능할 것 이다.

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