• Title/Summary/Keyword: T-응력

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Dynamic Fracture Analysis of Structural Element due to Stress Wave Propagation (응력파에 의한 구조부재의 동적파괴 해석)

  • 김경수;박준범;정배훈
    • Computational Structural Engineering
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    • v.10 no.4
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    • pp.195-203
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    • 1997
  • The interaction between cracks and stress wave due to impact and explosive loads is numerically calculated in the study. The interaction and the effects of stress wave are numerically examined with the application of Bicharacteristic Method. This method has been used with confidence for its reliability in reproducing the realistic and physical wave pattern in the complete solution domain. The dynamic stress intensity factor, K/sub I/(t) for cracks under impact loads are numerically simulated and its results are compared favorably with Kalthoff's experimental output. Also the influence of stress wave to the dynamic stress intensity factor for the case of two symmetric holes around cracks are investigated. The results of study are also compared favorably with the experiment and proven to be applied to the structures exposed to impact and explosive loads.

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Stress Relaxation of mayonnaise Colloidal Solution (마요네즈 콜로이드 용액의 응력완화에 관한연구)

  • 윤승희
    • The Korean Journal of Rheology
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    • v.7 no.1
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    • pp.28-34
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    • 1995
  • 고체가 아닌 계인 마요네즈에 대해 Couette형 점도계를 사용하여 일정한 전단속도에 서 시간과 더불어 전단응력이 감소하는 응력완화 곡선을 온도 2$0^{\circ}C$, $25^{\circ}C$, 3$0^{\circ}C$, 34$^{\circ}C$, 4$0^{\circ}C$ 에서 얻었다 이현상을 설명하기 위하여 구조가 형성되는 flow unit 2와 구조가파괴되는 flow unit 3에 대한 fraction (X2, X3)사이의 평형을 생각하고 X2 와 X3 에 해당하는 항에 실 험적 조건인 s=p(t0+t)의 관계를 적용하여 다음과 같은 응력완화에 관한 식을 구하고 이식을 실험결과에 적용하여 유동파라메타를 구하였으며 그 파라메타중의 평형상수 k와 실험 온도 를 이용하여 열역학 파라메타를 구하였다.

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A Quantitative Analysis of ΔK Conversion Method for the Retardation Behavior of Fatigue Crack Growth in Varying Thickness of Al 2024-T3 Sheet Alloy (판재 Al 2024-T3 합금재료에서 나타나는 두께별 피로균열진전지연거동에 관한 ΔK환산법의 정량적분)

  • Kim, Seung-Gwon;Lee, Ouk-Sub
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.35 no.11
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    • pp.1415-1422
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    • 2011
  • Sheet aluminum alloys used in manufacturing of machine structures for transportation show the difference of crack growth speed depending on thickness under the constant fatigue stress condition. The referred thickness effect is a major fatigue failure property of sheet aluminum alloys. In this work, we identified the thickness effect in fatigue test of thick plate and thin plate of Al 2024-T3 alloy under the constant fatigue stress condition, and presented the thickness effect to a correlative equation, $U_{i}^{equ}=f(R_t)$ which is determined by the shape factor, thickness ratio, $R_t$ and the loading factor, equivalent effective stress intensity ratio depending on thickness, $U_{i}^{equ}$. And we analyzed quantitatively the crack growth retardation behavior in thin plate compared to thick plate by the thickness effect using ${\Delta}K$ conversion method. We obtained such values as decrement of thickness(DoT), decrement of stress intensity factor range, ${\Delta}K$ (DoS) and identified the relation between them to present the nature of thickness effect in this work.

A Study on the Strength Safety of a Composite Hydrogen Fuel Tank for a Vehicle (차량용 복합소재 수소연료탱크의 강도안전성에 관한 연구)

  • Kim, Chung-Kyun;Kim, Do-Hyun
    • Journal of the Korean Institute of Gas
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    • v.15 no.5
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    • pp.37-41
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    • 2011
  • This paper presents the strength safety of a hydrogen gas composite fuel tank, which is analyzed using a FEM based on the criterion of US DOT-CFFC and Korean Standard. A hydrogen gas composite tank in which is fabricated by an aluminum liner of 6061-T6 material and carbon fiber wound composite layers of T800-24K is charged with a filling pressure of 70MPa and a gas storage capacity of 130 liter. The FEM results indicated that von Mises stress, 255.2MPa of an aluminum liner inner tank is low compared with that of 95% yield strength, 272MPa. And a carbon fiber stress ratio of a composite fuel tank is 3.11 in hoop direction and 3.04 in helical direction. These data indicate that a carbon fiber gas tank is safe in comparison to that of a recommended criterion of 2.4 stress ratio. Thus, the proposed composite tank with 130 liter capacity and 70MPa filling pressure is usable in strength safety.

A Fracture Mechanics Approach on Delamination and Package Crack in Electronic Packaging(l) -Delamination- (반도체패키지에서의 층간박리 및 패키지균열에 대한 파괴역학적 연구 (1) -층간박리-)

  • 박상선;반용운;엄윤용
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.8
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    • pp.2139-2157
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    • 1994
  • In order to understand the delamination between leadframe and epoxy molding compound in an electronic packaging of surface mounting type, the stress intensity factor, T-stress and J-integral in fracture mechanics are obtained. The effects of geometry, material properties and molding process temperature on the delamination are investigated taking into account the temperature dependence of the material properties, which simulates as more realistic condition. As the crack length increases the J-integral increases, which suggest that the crack propagates if it starts growing from the small size. The effects of the material properties and molding process temperature on stress intensity factor, T-stress is and J-integral are less significant than the chip size for the practical cases considered here. The T-stress is negative in all eases, which is in agreement with observation that interfacial crack is not kinked until the crack approaches the edge of the leadframe.

Reference Stress Based Stress Analysis for Local Creep Rupture of a T-pipe (참조응력법에 입각한 T-배관 국부 크리프 파단 평가를 위한 응력해석 사례연구)

  • Shin Kyu-In;Yoon Kee-Bong;Kim Yun-Jae
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.30 no.8 s.251
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    • pp.873-879
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    • 2006
  • To investigate applicability of the reference stress approach as simplified inelastic stress analysis to estimate local creep rupture, detailed finite element stress analyses of a T-piece pipe with different inner pressure and system loading levels are performed. The reference stresses are obtained from the finite element (FE) limit analysis based on elastic-perfectly-plastic materials, from which the local reference stress for creep rupture is determined from R5. The resulting inelastic stresses are compared with elastic stresses resulting from linear elastic FE calculations. Furthermore they are also compared with the stresses from full elastic-creep FE analyses. It shows that the stresses estimated from the reference stress approach compare well with those from full elastic-creep FE analysis, which are significantly lower than the elastic stress results. Considering time and efforts for full inelastic creep analysis of structures, the reference stress approach is shown to be a powerful tool for creep rupture estimates and also to reduce conservatism of elastic stress analysis significantly.

Analysis of Hydraulic Fracture Geometry by Considering Stress Shadow Effect during Multi-stage Hydraulic Fracturing in Shale Formation (셰일저류층의 다단계 수압파쇄에서 응력그림자 효과를 고려한 균열형태 분석)

  • Yoo, Jeong-min;Park, Hyemin;Wang, Jihoon;Sung, Wonmo
    • Journal of the Korean Institute of Gas
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    • v.25 no.1
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    • pp.20-29
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    • 2021
  • During multi-stage fracturing in a low permeable shale formation, stress interference occurs between the stages which is called the "stress shadow effect(SSE)". The effect may alter the fracture propagation direction and induce ununiform geometry. In this study, the stress shadow effect on the hydraulic fracture geometry and the well productivity were investigated by the commercial full-3D fracture model, GOHFER. In a homogeneous reservoir model, a multi-stage fracturing process was performed with or without the SSE. In addition, the fracturing was performed on two shale reservoirs with different geomechanical properties(Young's modulus and Poisson's ratio) to analyze the stress shadow effect. In the simulation results, the stress change caused by the fracture created in the previous stage switched the maximum/minimum horizontal stress and the lower productivity L-direction fracture was more dominating over the T-direction fracture. Since the Marcellus shale is more brittle than more dominating over the T-direction fracture. Since the Marcellus shale is more brittle than the relatively ductile Eagle Ford shale, the fracture width in the former was developed thicker, resulting in the larger fracture volume. And the Marcellus shale's Young's modulus is low, the stress effect is less significant than the Eagle Ford shale in the stage 2. The stress shadow effect strongly depends on not only the spacing between fractures but also the geomechanical properties. Therefore, the stress shadow effect needs to be taken into account for more accurate analysis of the fracture geometry and for more reliable prediction of the well productivity.

The simple measurement of physical properties and stress fringe value for photo-elastic orthotropic material (광탄성 직교이방성체의 물성치와 응력 프린지치 간이 측정법)

  • 황재석;이광호
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.14 no.1
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    • pp.23-36
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    • 1990
  • The various composite materials have been developed with the development of high strength material and the increasement of composite material usage. Therefore many researchers have studied about the stress analysis and the fracture mechanics for composite materials through the experiment or the theory. Among the experimental methods, the photoelastic experiments have been used for the stress analysis of the isotropic structures or the anisotropic structures. To analyze the stresses in the orthotropic material with photoelastic experiment, the basic physical properties ( $E_{L}$, $E_{T}$, $G_{LT}$ , .nu.$_{LT}$ ) and the basic stress fringe values ( $f_{L}$, $f_{T}$, $f_{LT}$ )are needed, therefore the relationships between the basic physical properties and the stress fringe values were derived in this paper. When the stress fringe value is very large, it was assured by the experiment that the relationships are established both in the room temperature and in the high temperature (T = 130.deg. C). Therefore the basic physical properties can be obtained from the relationships by measuring stress fringe values instead of measuring the basic physical properties.rties.

Structural Safety Analysis on Car Body at Overturn (전복시 차체에 대한 구조 안전 해석)

  • Cho, Jae-Ung;Kim, Key-Sun;Lee, Eun-Jong
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.12 no.1
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    • pp.32-37
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    • 2011
  • In this study, the changes of displacement and stress are investigated by structural analysis according to the thickness of car body in case of overturn. In case of 5 mm thickness, the maximum displacement of 7.5024 mm at its right ceiling and the maximum equivalent stress of 113.69 MPa at the left lower part are occurred on the elapsed time of 2 second. In case of 10 mm thickness, the maximum displacement of 1.2557 mm at its right ceiling and the maximum equivalent stress of 15.134 MPa at the left lower part are occurred on the elapsed time of 2 second. In case of 15 mm thickness, the maximum displacement of 0.426067 mm at its right ceiling and the maximum equivalent stress of 4.4842 MPa at the left lower part are occurred on the elapsed time of 2 second. As stress and displacement are uniformly distributed according to time in this case, the design of car body can be stabilized.