• 제목/요약/키워드: Strain Energy Density Factor

검색결과 30건 처리시간 0.03초

Fatigue Strength Assessment of Spot-Welded Lap Joint Using Strain Energy Density Factor

  • Sohn, Ilseon;Bae, Dongho
    • Journal of Mechanical Science and Technology
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    • 제15권1호
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    • pp.44-51
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    • 2001
  • One of the recent issues in design of the spot-welded structure such as the automobile body is to develop an economical prediction method of the fatigue design criterion without additional fatigue test. In this paper, as one of basic investigation for developing such methods, fracture mechanical approach was investigated. First, the Model I, Mode II and Mode III, stress intensity factors were analyzed. Second, strain energy density factor (S) synthetically including them was calculated. And finally, in order to decide the systematic fatigue design criterion by using this strain energy density factor, fatigue data of the ΔP-N(sub)f obtained on the various in-plane bending type spot-welded lap joints were systematically re-arranged in the ΔS-N(sub)f relation. And its utility and reliability were verified by the theory of Weibull probability distribution function. The reliability of the proposed fatigue life prediction value at 10(sup)7 cycles by the strain energy density factor was estimated by 85%. Therefore, it is possible to decide the fatigue design criterion of spot-welded lap joint instead of the ΔP-N(sub)f relation.

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최소 변형에너지 밀도 기준의 모호성과 최대 극소 변형에너지 밀도 기준 (Ambiguity of Minimum Strain Energy Density Criterion and Maximum Minimum Strain Energy Density Criterion)

  • 구재민
    • 대한기계학회논문집A
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    • 제25권7호
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    • pp.1155-1162
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    • 2001
  • Sihs minimum strain energy density criterion(SED) often used in the mixed mode problem has the ambiguity of the choice of minimum values. In this paper, as the method to solve the problem of SED, maximum minimum strain energy density criterion is proposed that the crack propagates in the direction of having the maximum among the minimum values of modified strain energy density factor(MS), i.e., sign($\sigma$(sub)$\theta$).Smin.

평균응력을 동반하는 2.2Ni-lCr-0.5Mo강의 피로수명과 변형률에너지 밀도와의 상관관계 (Correlation Between Fatigue Life of 2.2Ni-0.1Cr-0.5Mo Steel Accompanying Mean Stresses with Cyclic Strain Energy Density)

  • 고승기;하정수
    • 대한기계학회논문집A
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    • 제27권1호
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    • pp.167-174
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    • 2003
  • Fatigue damage of 2.2Ni-1Cr-0.5Mo steel used fir high strength pressure tubes and vessels was evaluated using uniaxial specimens subjected to strain-controlled fatigue loading. Based on the fatigue test results from different strain ratios of -2. -i 0, 0.5, 0.75, the fatigue damage of the steel was represented by using a cyclic strain energy density. Mean stress relaxation depended on the magnitude of the applied strain amplitude. The high pressure vessel steel exhibited the cyclic softening behavior. Total strain energy density consisting of the plastic strain energy density and the elastic tensile strain energy density described fairly well the fatigue life of the steel, taking the mean stress effects into account. Compared to other fatigue damage parameters, fatigue life prediction by the cyclic strain energy density showed a good correlation with the experimental fatigue lift within a factor of 3.

Distortion and Dilatatioin in the Tensie Failure of Paper

  • Park, Jong-Moon;James L. Thorpe
    • 펄프종이기술
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    • 제31권5호
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    • pp.73-85
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    • 1999
  • Yield and fracture are separated in the tensile failure of paper. Failure in the machine direction of photocopy paper is contrasted with failure in the cross-machine direction . The ratios of distortion (shape change) to dilatation (volume change) for individual elements at yield and fracture are described. The ratios of distortion to dilatation are measured and compared to predicted values of the strain energy density theory. To evaluate the effect of the angle from the principal material direction on the strain energy density theory. To evaluate the effect of the angle from the principal material direction on the strain energy density factor, samples are prepared from machine direction to cross-machine direction in 15 degree intervals. the strain energy density of individual elements are obtained by the integration of stress from finite element analysis with elastic plus plastic strain energy density theory. Poison's ratio and the angle from the principal material direction have a great effect ion the ratio fo distortion to dilatation in paper. During the yield condition, distortion prevails over dilatation . At fracture, dilatation is at a maximum.

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혼합모드 피로문제에서의 최소 변형에너지 밀도기준의 적용 (An Application of Minimum Strain Energy Density Criterion in Mixed Mode Fatigue Problem)

  • 심규석;구재민
    • 한국안전학회지
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    • 제17권2호
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    • pp.1-7
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    • 2002
  • In this paper, the maximum minimum strain energy density criterion was applied to the mixed mode fatigue test of A5052 H34 alloy. In this study result we can have seen that the authors stress intensity factor for the finite width specimen and method of determining testing load, based on the plastic zone size and the limited maximum stress intensity factor by ASTM STANDARD E-647-95, is useful.

변위기여도 및 변형에너지밀도를 활용한 초고층 건물의 센싱 부재 선정 (Selection of Sensing Members in a High-rise Building Structures using Displacement Participation Factors and Strain Energy Density)

  • 이홍민;박성우;박효선
    • 한국전산구조공학회논문집
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    • 제22권4호
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    • pp.349-354
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    • 2009
  • 초고층 건물의 안전성 및 사용성을 합리적으로 확보하고 유지하기 위해서 부재의 구조 반응 모니터링은 필요하다. 이러한 대형 건물의 건전도 모니터링은 최근 들어 많은 연구자들에 의해서 관심 되어지고 있지만 건물 특성상 계측 대상 부재가 많고 하중과 구조반응의 관계가 복잡하기 때문에 센싱 부재 선정의 어려움으로 그 적용에 한계가 있다. 본 논문에서는 부재의 변위기여도 및 변형에너지밀도를 기반으로 초고층 건물의 안전성 모니터링을 위한 구조반응 계측 부재 선정에 대한 연구를 수행하였다.

단일 및 혼합모드하에서 304스테인리스강의 피로균열 진전속도와 방향특성 (Fatigue Crack Growth Rates and Directions in STS304 under Mode I and Mixed Mode)

  • 권종완;양현태
    • 한국공작기계학회논문집
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    • 제11권3호
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    • pp.102-109
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    • 2002
  • The fatigue crack growth under mixed mode condition has been discussed within the scope of linear fracture mechanics such as maximum tangential stress, maximum tangential principal stress and minimum strain energy density. The purpose of this study is to investigate the characteristics of fatigue test crack growth in 304 stainless steel under mixed node. The fatigue test results carried out by using inclined pre-crack specimens was compared to both of the theoretical predictions of the criteria, maximum tangential stress and stain energy density. As difference from theoretical analysis, the transition region from mixed mode to mode I appeared in the fatigue test. There is deep relationship between the angle of slanted pre-crack and transition. Therefore, as applying the different stress intensity factor to each node I+II and mode I, the directions and rates of fatigue crack growth are evaluated more accurately under mixed mode.

등가 단위하중을 이용한 동체 구조물 피로수명 평가 (Fatigue life evaluation for fuselage structure using equivalent unit load)

  • 김성준;안석민;염찬홍
    • 항공우주기술
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    • 제8권2호
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    • pp.13-18
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    • 2009
  • 본 연구에서는 피로해석을 단순화하기위한 등가 단위하중 방법을 제시하였다. 그리고 등가 단위하중을 이용하여 동체구조물의 피로수명을 평가하였다. 균열진전해석에 필요한 응력확대 계수와 기하학적 형상계수를 계산하기 위하여 유한요소 해석을 수행하였다. 또한 균열진전 방향을 평가하기 위하여 변형률 에너지 밀도 계수를 사용하였다.

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A Study on the Initial Crack Curving Angle of Isotropic/Orthotropic Bimaterial

  • Hawong, Jai-Sug;Shin, Dong-Chul;Lee, Ouk-Sub
    • Journal of Mechanical Science and Technology
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    • 제16권12호
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    • pp.1594-1603
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    • 2002
  • In this paper, when the initial propagation angle of a branched crack is calculated from the maximum tangential stress criterion (MTSC) and the minimum strain energy density criterion (MSEDC), it is essential that you use stress components in which higher order terms are considered and stress components at the position in a distance 0.005㎜ from the crack tip (=r). When an interfacial crack propagates along the interface at a constant velocity, the initial propagation angles of the branched crack are similar. to the mode mixities (phase angle) and the theoretical values obtained from MTSC and MSEDC. The initial propagation angle of the branched crack depends considerably on the stress intensity factor K$_2$.

자동차 루프의 진동제어를 위한 제진재의 위치 및 두께에 대한 실험적 연구 (An Experimental Study on Placements and Thickness of Damping Material for Vibration Control of Automotive Roof)

  • 이정균;김찬묵;사종성
    • 한국자동차공학회논문집
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    • 제13권6호
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    • pp.31-37
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    • 2005
  • This paper presents an experimental study on vibration characteristics of an automotive roof with damping material. The goal of the study is to extract modal parameters(natural frequency, loss factor, and mode shape) of automotive roof with damping materials treatment. To determine the effective positions and thickness of the damping material on a roof, vibration tests have been carried out for six cases; an aluminum plate with damping material on maximum strain energy positions, and an aluminum plate with damping material on nodal lines. From the result of aluminum plate, it is found that the damping material should be placed on the location with maximum strain energy part. For the automotive roof, patches of constrained damping material, which has two different density, have been attached to the positions of the maximum strain energy with four kinds of thicknesses. This paper shows that the proper positioning of the damping material is very important and the effective thickness is about twice that of the roof panel.