• 제목/요약/키워드: Life curve

검색결과 987건 처리시간 0.35초

Glass/Epoxy 복합재료의 피로강도평가 및 피로수명예측 (The Fatigue Strength and the Fatigue Life Prediction in Plain Woven Glass/Epoxy Composite Plates)

  • 김정규;김도식
    • 대한기계학회논문집
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    • 제17권10호
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    • pp.2475-2482
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    • 1993
  • The effects of the hole size(2R) and the specimen width(W) on the fatigue strength and the fatigue life in plain woven glass/epoxy composite plates are experimentally investigated under constant amplitude tensile fatigue loading. It is shown in this study that the notch sensitivity under fatigue loading is lower than that under static loading. It can be explained by the fact that the stress concentration is relaxed by the damage developed at the boundary of circular hole. To predict the fatigue strength at a specific cycle, the modified point stress criterion represented as a function of the geometry of the specimen(2R and W) is applied. It is found that the model used in the prediction of the notched tensile strength predicts the fatigue strength with reasonable accuracy. A model for predicting the fatigue life in the notched specimen, based on the S-$N_f$, curve in the smooth specimen, is suggested.

장애인의 삶의 만족도 변화양상과 예측요인에 관한 연구: 사회 자본의 구성개념인 네트워크와 사회참여를 중심으로 (A Study on the Longitudinal Change Pattern and the Predictor Factor of Life Satisfaction of People with Disabilities: Focused on Social Capital including network and social participation)

  • 이계승
    • 사회복지연구
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    • 제45권2호
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    • pp.375-402
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    • 2014
  • 이 연구는 장애와 그에 따른 부가적 실체(낙인, 편견, 차별,, 사회적 제약 등)들로 인해 낮은 삶의 만족도를 나타내는 장애인들의 삶의 만족도 변화양상을 종단적으로 살펴보고, 그에 대한 예측요인으로서 사회자본의 구성개념인 네트워크와 사회참여의 영향력을 파악하는데 목적이 있다. 이를 위해 2차~5차 장애인고용패널조사 자료를 활용해, 3206명을 대상으로 잠재성장모형 분석을 실시하였다. 분석결과, 장애인의 삶의 만족도는 시간이 흐를수록 감소하는 경향을 나타냈으며, 초기 높은 삶의 만족도를 나타낸 장애인의 경우 시간이 흐를수록 완만하게 감소하고, 낮은 삶의 만족도를 나타낸 장애인의 경우 가파르게 감소하는 경향을 보였다. 삶의 만족에 영향을 미치는 네트워크와 사회참여의 영향력을 살펴보면, 네트워크는 삶의 만족도 초기 값에 정적인 영향을, 변화율에는 부적인 영향을 미쳤다. 사회참여는 삶의 만족도 초기 값에 정적인 영향을 미쳤으나, 변화율에는 영향을 미치지 못하였다. 이러한 결과를 바탕으로 실천적 개입방안과 정책적 함의를 제시하였다.

동적기하프로그램을 활용한 이차곡선 최적화 문제해결에 관한 연구 (A Study on the Optimization Problem Solving utilizing the Quadratic Curve using the Dynamic Geometry Software)

  • 김정수;전보현;정영우;김부윤;이양
    • East Asian mathematical journal
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    • 제30권2호
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    • pp.149-172
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    • 2014
  • The problems of optimization addressed in the high school curriculum are usually posed in real-life contexts. However, because of the instructional purposes, problems are artificially constructed to suit computation, rather than to reflect real-life problems. Those problems have thus limited use for teaching 'practicalities', which is one of the goals of mathematics education. This study, by utilizing 'GeoGebra', suggests the optimization problem solving related to the quadratic curve, using the contour-line method which contemplates the quadratic curve changes successively. By considering more realistic situations to supplement the limit which deals only with numerical and algebraic approach, this attempt will help students to be aware of the usefulness of mathematics, and to develop interests in mathematics, as well as foster students' integrated thinking abilities across units. And this allows students to experience a variety of math.

구조응력기반 마스터 피로 선도를 이용한 하중 비전달형 십자 필렛 용접조인트의 피로예측 (Fatigue Life Prediction of Non-Load-Carrying Cruciform Welded Joint using Master S-N Curve based on Structural Stress Approach)

  • 곽시영
    • Journal of Welding and Joining
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    • 제33권6호
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    • pp.49-54
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    • 2015
  • Welding process is of importance to assemble products or structures, but also the process is structural weakness due to stress concentration in welding joint. The fatigue design of welded joint requires time & labor consuming fatigue test because the fatigue life is various according to the depth of joint, joint type and load type etc. In fatigue design codes, they guide to classify welding joints with their shape( BS7608, IIW Documents) and provide fatigue assessment information. In terms of numerical method for fatigue analysis, it is also difficult to decide the stress peak in joint because of mesh sensitivity which means that stress value is varies with element type or size on stress concentration zone. Hot-spot method is used generally, but Battelle of United States proposed Master S-N Curve based on structural stresses converted by mechanical equilibrium theory. In this research, we extracted master S-N curve from Battelle's fatigue test DB including test data of various welding joints to apply on Non-Load-Carrying cruciform Joint. Comparing fatigue results between the case of using normal stress and case of structural stress cor the cruciform Joint, The suggested Battelle method showed successive results.

사망원인과 특정사인생명표에 관한 연구 (A Study on The Life Tablefor Specific Causes of Death in Korea)

  • 한동준
    • 한국인구학
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    • 제6권1호
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    • pp.43-69
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    • 1983
  • This study was conducted to make the life tables from specific causes of death in Korea. Both "Life tables of Korea in l978-79" and "the statistics on causes of death statistics in 1980" issued by Economic Planning Board were used as source of data for this study. Among the 58, 187 death certificates reported to the concerned authorities, 39, 801 causes were drawn for the purpose of this study. As a result, it is revealed that two thirds of men in Korea died from these 10 major causes of death. The summarized results are as follows: 1. According to recent statistics, 10 major causes of death in 1980 were shown in the order of 1) malignant neoplasms, 2) cerebrovascular disease, 3) accidents and adverse effects, 4)hypertensive disease, 5) ischaemic heart disease and heart attack, 6) chronic liver disease and cirrhosis, 7) tuberculosis, 8) pneumonia, bronchitis, emphysema and asthma, 9) suicide, 10) diabetes mellitis. 2. The major causes of death in Korea were very similar to those of developed countries such as West Germany, Denmark and Japan. This means that our pattern of death causes is almost approaching to that of developed countries. 3. Our crude death rate in 1980 was on the line of 6.6 per 1, 000 people. This is very low level, compared with 12.1 in West Germany and 10.0 in Denmark, however, our age sepcific death rate was on the verge of doubled level in each age category as to that of West Germany, Denmark and Japan. The fact tells us that our death rate is very high yet, especially in young and prime adult age, and the proportion of the aged is quite low. 4. Average ages of people died from malignant neoplasms, cerebro vascular diseases and hypertensive diseases were 63.1, 66.6, 67.3 respectively, however, that of accidents and adverse effect was only 42.5. This shows that accidents occur indifferently from age. 5. In the curve of eventual death probability, the curve of malignant neoplasms was the highest of all curves before 60 in age. However, the probability curve of eventually dying from accidents and adverse effects tends to decline with age. 6. In this study five life tables from major causes of death (four leading causes of death and of tuberculosis) were constructed for 1979. These life tables are reflecting accurately the effects of age distribution on the specific cause of death. In the surviving curje of these tables we can see that the curve of accidents is adversely related to age. While curves of neoplasms, hypertension and tuberculosis are not diminishing before 40 in age, they are going sharply downward after 50 in age.ard after 50 in age.

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자동차 Transimission용 Helical Gear의 굽힘 피로 수명 곡선(SS-N Curve)에 관한 실험적 고찰 (An experimental study of bending fatigue life (S-N curve) of the helical gear for the automotive transmission)

  • 이원희;허윤무
    • 오토저널
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    • 제12권6호
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    • pp.11-17
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    • 1990
  • 자동차용 변속기의 설계에 있어서 적용 Engine의 출력 및 차량 성능에 부합하는 동력전달 요소의 전달 용량 및 내구 수명을 고려해야 한다. 특히 자동차가 고속 경량화됨에 따라 변속기의 설계에 있어서도 동력전달 요소들의 소형 고용량화가 요구되며 이를 위해서는 설계시 동력전달 요소들의 정확한 강도 및 피로수명 예측이 필수적이다. 본 보고서에서는 Gear의 굽힘응력 계산식에 대한 고찰 및 Gear의 피로시험을 통하여 Helical 치차의 Bending stress에 대한 피로수명 곡선의 시험식을 도출하였다.

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복합재 플라이 오버랩 조인트 구조의 피로 수명 예측 (Prediction for Fatigue Life of Composite Ply-overlap Joint Structures)

  • 이예주;김휘엽;박정선
    • 항공우주시스템공학회지
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    • 제17권2호
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    • pp.62-70
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    • 2023
  • 본 논문에서는 두 가지 복합재료의 플라이를 부분적 또는 전체적으로 적층하여 접합시킨 플라이 오버랩 조인트 구조의 기하학적 특징을 이용하여 응력-수명(S-N) 선도 및 피로 수명을 예측하는 기법을 제안한다. 구조의 피로 특성에 영향을 주는 기하학적 특징을 변수로 선정하였다. 기하학적 변수와 복합재 피로 모델인 Epaarachchi-Clausen 모델을 구성하는 재료상수의 관계를 분석하여 두 요소의 관계식을 제안하였다. 제안한 방법의 예측 정확도 검증을 위해서 CFRP/GFRP 플라이 오버랩 조인트의 피로 수명을 예측하였다. 예측된 수명과 시험 데이터 기반 모델로 얻은 수명을 실제 수명에 비교하였다. 또한, 예측된 S-N 선도의 결정 계수를 계산함으로써 높은 예측 정확도를 확인하였다.

단조 금형의 수명 평가에 관한 연구 (A Study on Life Estimation of a Forging Die)

  • 최창혁;김용조
    • 소성∙가공
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    • 제16권6호
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    • pp.479-487
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    • 2007
  • Die life is generally estimated taking failure life and wear amount into consideration. In this study, the forging die life was investigated considering both of these two factors. The fatigue life prediction for the die was performed using the stress-life method, i.e. Goodman's and Gerber's equations. The Archard's wear model was used in the wear life simulation. These die life prediction techniques were applied to the die used in the forging process of the socket ball joint of a transportation system. A rigid-plastic finite element analysis for the die forging process of the socket ball was carried out and also the elastic stress analysis for the die set was performed in order to get basic data for the die fatigue life prediction. The wear volume of the die was measured using a 3-dimensional measurement apparatus. The simulation results were relatively in good agreement with the experimental measurements.

平활材表面 의 微小피勞균열에 관한 基礎的 特性 (Basic Characteristics of Micro-Fatigue-Cracks on the Unnotched Smooth Specimens)

  • 서창민;북천영부;결성양치
    • 대한기계학회논문집
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    • 제7권1호
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    • pp.28-35
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    • 1983
  • Quantitative analysis have been carried out on the micro-cracks on the surface and into the depth of unnotched smooth mild steel specimen under cyclic stains by rotating bending fatigue tests. Some of the results are; (1) Cracks initiate at the early stage of fatigue life N$_{I}$/ N$_{f}$=10 to 20%, and propagate during the rest of fatigue life. (2) Coalescence of highly crowded small fatigue cracks of random distribution seems to induce the final fracture at higher stress level. (3) The curves of crack initiation and the equal crack length on the graph of stress versus number of cycles are parallel to the S-N curve. (3) The curves of crack initiation and the equal crack length on the graph of stress versus number of cycles are parallel to the S-N curve. (4) The distributions of micro-surface crack length and depth show the composite Weibull distributions which are approximated to two straight lines separated by the value of transient region between stage I and stage II crack.k.k.