• Title/Summary/Keyword: 응력 복원

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Thermal Stress Analysis of Composite Beam through Dimension Reduction and Recovery Relation (차원축소와 복원관계를 통한 복합재료 보의 열응력 해석)

  • Jang, Jun Hwan;Ahn, Sang Ho
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.30 no.5
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    • pp.381-387
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    • 2017
  • Fiber-reinforced composites not only have a direction of thermal expansion coefficient, but also inevitably suffer thermal stress effects due to the difference between the manufacturing process temperature and the actual use temperature. The damage caused by thermal stress is more prominent in the case of thick composite laminates, which are increasingly applied in the aerospace industry, and have a great influence on the mechanical function and fracture strength of the laminates. In this study, the dimensional reduction and thermal stress recovery theory of composite beam structure having high slenderness ratio is introduced and show the efficiency and accuracy of the thermal stress comparison results between the 3-D finite element model and the dimension reduction beam model. Efficient recovery analysis study will be introduced by reconstructing the thermal stress of the composite beam section applied to the thermal environment by constructing the dimensional reduction modeling and recovery relations.

Blade Analysis Library Development of Dimension Reducible Modeling and Recovery Analysis for Composite Rotor Blades (복합재 로터 블레이드의 차원축소와 복원해석을 위한 블레이드 해석 라이브러리 개발)

  • Jang, Jun Hwan;Lee, Hwan
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.43 no.10
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    • pp.920-927
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    • 2015
  • In this paper, numerical results of sectional analysis and stress recovery were compared with the results of VABS through the blade analysis library. The results of recovery analysis for one-dimensional model including the stiffness matrix is compared with the calculated three-dimensional stress results of three-dimensionial FEM based on the principle of virtual work. We discuss the configuration of the blade analysis library and compare verifications of numerical analysis results of VABS. Blade analysis library through dimensional reduction and stress recovery is intended to be utilized in conjunction with pre- and post-processing of the analysis program of the composite blade, high-altitude uav's wing, wind blades and tilt rotor blade.

Isogeometric Analysis for Two-dimensional Multipatch Model (2차원 멀티패치 모델의 아이소-지오메트릭 해석)

  • Kim, Min-Geun;Koo, Bonyong
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.30 no.6
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    • pp.515-522
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    • 2017
  • In this paper, an isogeometric analysis for multipatch problem is investigated, in which two or more geometries are connected at the interface in a conforming or non-conforming conditions. To express higher continuity at the patch interface, two approaches such as Nitsche based method and master-slave method are formulated for the linear elasticity problem and discretized using the isogeometric approach using NURBS basis functions. A short comparison between two approaches in formulations reveals the pros and cons of them with the applicability in the isogeometric multipatch problem. In addition, a NURBS based stress recovery is adopted to express a better stress continuity through the post-processing. Numerical examples indicate the effectiveness of Nitsche method in the non-conforming patch, following the exact solution well. For the stress concentration problem with the conforming patch, introduced two methodologies show comparative results, meanwhile the NURBS based stress recovery presents an improved smooth stress contour in the whole domain including the patch interface.

Effects of Carbon Blacks on Viscoelastic Behavior of Natural Rubber Melt (천연고무 용융체의 점탄성적 거동에 대한 카본블랙의 영향)

  • Shin, Soo;Choi, Chang-Nam;Nah, Chang-Woon;Kaang, Shin-Young
    • Elastomers and Composites
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    • v.34 no.3
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    • pp.262-268
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    • 1999
  • Effect of carbon blacks (CBs) on the stress relaxation and the elastic recovery of uncrosslinked natural rubber (NR) was examined. It was found that if the type of CB is characterized by smaller size and higher structure, the stress relaxation is more delayed and the elastic recovery becomes more active. These results are attributed to the degree of bound rubber, i.e., the interaction between NR and CB.

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A Study on Composite Blade Analysis Library Development through Dimension Reduction/Recovery and Calculating Energy Release Rate (단면의 차원축소/복원해석과 에너지 해방률 계산을 위한 복합재 블레이드 해석 라이브러리 개발에 대한 연구)

  • Jang, Jun Hwan;Ahn, Sang Ho
    • Composites Research
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    • v.29 no.1
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    • pp.16-23
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    • 2016
  • In this paper, numerical results of sectional analysis, stress recovery and energy release rate were compared with the results of VABS, 3-D FEM through the blade analysis library. The result of stress recovery analysis for one-dimensional model including the stiffness matrix is compared with stress results of three-dimensional FEM. We discuss the configuration of the blade analysis library and compare verifications of numerical analysis results of VABS. Blade analysis library through dimensional reduction and stress recovery is intended to be utilized in conjunction with pre- and post-processing of the analysis program of the composite blade, high-altitude uav's wing, wind blades and tilt rotor blade.

Evaluation of Characteristics for Stress Distribution on Cylindrical Beam Structure by Deformation and Restoration Process (변형 및 복원공정에 따른 실린더 형상 구조물의 응력분포 특성)

  • Park Chi-Yong;Kim Jin-Weon;Boo Myung-Hwan
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.29 no.1 s.232
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    • pp.132-138
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    • 2005
  • In heavy industrial fields such as power plant and chemical plant, it is often necessary to restore damaged part of large machinery and structure which is installed in the hazard working place. In this paper, to estimate stress distribution which occurs during damage and restoration of cylindrical beam structure, the finite element technique has been used. A finite element model was verified by experiment for non deformed cylindrical beam structure. The displacements and elastic recovery have an excellent agreement between experiment and finite element analysis. The variations of stress distribution on deformation and restoration procedure for surfaces have been examined. The maximum von Mises stress appears in the surface for deformation and restoration procedure. In deformation procedure, the maximum stress occurs in the vicinity of support body. In restoration procedure, the maximum stress occurs in the vicinity of the fixing body. The fixing body allows avoiding stress concentration in adjacent support structure boundary.

Rheological Properties of Rehydrated Freeze Dried Instant Rice (동결건조 즉석미반의 리올로지적 성질)

  • Kim, Kwan-Yu;Lee, Shin-Young;Joo, Hyun-Kyu
    • Applied Biological Chemistry
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    • v.32 no.4
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    • pp.332-337
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    • 1989
  • Rheological properties of rehydrated freeze dried instant rice were investigated in comparison with that of cooked rice. The time changes in reciprocal hardness of instant rice grains at various rehydration temperatures$(60{\sim}90^{\circ}C)$ could be expressed by the first order reaction rate equation regardless of rehydration temperature and reaction rate constant increased as the rehydration temperature increased. Activation energy for rehydrating instant rice was 6.1 kcal/g-mol. Analysis of compressive stress relaxation test showed that the viscoelastic properties of both rehydrated instant rice and cooked rice grains could be expressed by 6-elements generalized Maxwell model. Rehydrated instant rice revealed higher relaxation decay than that of cooked rice and showed the elastic property increased by increasing the rehydration temperature.

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Ti-50.lat.% Ni 합금의 변태거동에 미치는 시효처리의 영향

  • 박성범;류부형;우흥식
    • Proceedings of the Korean Institute of Industrial Safety Conference
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    • 2003.10a
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    • pp.107-112
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    • 2003
  • 형상기억합금(shape memory alloy; SMA)은 소성가공을 통하여 원하는 형태로 변형시킨 이후에도(현재로서는 최대 10%미만의 변형) 일정조건의 열을 가하면 원래의 형상으로 복원되는 합금을 말한다. 형상기억효과는 고상(solid state)에서의 금속조직이 오스테나이트(austenite: 이하 A 또는 B2상)로부터 마르텐사이트(martensite: 이하 M 또는 B19'상)로, 다시 역으로 마르텐사이트에서 오스테나이트로의 변태에 기인되는 것으로 밝혀지고 있으며 이러한 변태는 온도유기변태(temperature induced transformation)와 응력유기변태(stress induced transformation)로 분류할 수 있다.(중략)

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Accelerated Degradation Test and Failure Analysis of Rapid Curing Epoxy Resin for Restoration of Cultural Heritage (문화재 복원용 속(速)경화형 Epoxy계 수지의 가속열화시험 및 고장분석 연구)

  • Nam, Byeong Jik;Jang, Sung Yoon
    • Journal of Conservation Science
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    • v.33 no.6
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    • pp.467-483
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    • 2017
  • In this study, the degradation properties by temperature stress of $Araldite^{(R)}$ rapid-curing epoxy resin used for inorganic cultural heritages, was identified. The tensile and tensile shear strength of durability decreased for 12,624 hours at temperatures of $40{\sim}60^{\circ}C$. In terms of stability of external stress and temperature, the slow-curing epoxy was superior to the rapid-curing epoxy, and cultural heritage conservation plans should therefore consider the strength and stress properties of restoration materials. Color differences increased for 12,624 hours at temperatures of $40{\sim}60^{\circ}C$, and glossiness decreased. Both color and gloss stability were weak, which necessitates the improvement of optical properties. Thermal properties (weight loss, decomposition temperature, and glass transition temperature) of adhesives are linked to mechanical properties. Interfacial properties of the adherend and water vapor transmission rates of adhesives are linked to performance variation. For porous media (ceramics, brick, and stone), isothermal and isohumid environments are important. For outdoor artifacts on display in museums, changes in physical properties by exposure to varying environmental conditions need to be minimized. These results can be used as baseline data in the study of the degradation velocity and lifetime prediction of rapid-curing epoxy resin for the restoration of cultural heritages.