• 제목/요약/키워드: isotropic point

검색결과 114건 처리시간 0.02초

다수의 직선 다중균열이 존재하는 등방성 무한판의 교호법을 이용한 해석 (Analysis of an Isotropic Infinite Plate with Many Collinear Multiple Cracks by the Alternating Method)

  • 박재학
    • 대한기계학회논문집A
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    • 제20권12호
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    • pp.3838-3846
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    • 1996
  • A method is proposed to obtain the stress intensity factors of multiple cracks lying on many straight llnes in an infinite isotropic plate. In this mehtod, analytical solutions for collinear multiple cracks subject to surface point forces are obrained and used as Green functions. For the multiple cracks lying onmany straight lines, the equivalent crack surface tractions are obtained by using the alternating method and the stress intensity factors are calculated. By using the proposed method several useful problems are solved and discussed.

석탄계 타르의 열처리 중 압력변화에 따른 변성 콜타르 핏치의 미세구조 및 물성 변화 (Changes of Microstructure and Properties of Manufactured Modified Pitches via Pressure Changes during Heat Treatments in Coal Tar Pitch)

  • 고효준;정성모;한지훈;박창욱;김명수;임연수
    • 한국재료학회지
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    • 제24권6호
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    • pp.293-300
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    • 2014
  • Coal-tar pitch, a feedstock which can be heat-treated to create graphite, is composed of very complex molecules. Coal-tar pitch is a precursor of many useful carbon materials (e.g., graphite, carbon fibers, electrodes and matrices of carbon/carbon composites). Modified coal-tar pitch (MCTP) was prepared using two different heat-treatment methods and their properties were characterized and compared. One was prepared using heat treatment in nitrogen gas; the other was prepared under a pressure of 350 mmHg in air. The MCTPs were investigated to determine several properties, including softening point, C/H ratio, coke yield, formation of anisotropic mesophase and viscosity. The MCTPs were subject to considerable changes in chemical composition due to condensation and polymerization in the used-as-received coal-tar pitch after heat-treatment under different conditions. The MCTPs showed considerable increases in softening point, C/H ratio, and coke yield, compared to those of as-received coal-tar pitch. The MCTP formed by heat-treatment in nitrogen showed isotropic phases below $350^{\circ}C$ for 1 h of soaking time. However, MCTP heat-treated under high pressure (350 mmHg) showed isotropic phases below $300^{\circ}C$, and showed anisotropic phases above $350^{\circ}C$, for 1 h of soaking time. The viscosity of the MCTPs increased with increase in their softening points.

Point load actuation on plate structures based on triangular piezoelectric patches

  • Tondreau, Gilles;Raman, Sudharsana Raamanujan;Deraemaeker, Arnaud
    • Smart Structures and Systems
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    • 제13권4호
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    • pp.547-565
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    • 2014
  • This paper investigates the design of a perfect point load actuator based on flat triangular piezoelectric patches. Applying a difference of electric potential between the electrodes of a triangular patch leads to point loads at the tips and distributed moments along the edges of the electrodes. The previously derived analytical expressions of these forces show that they depend on two factors: the width over height (b/l) ratio of the triangle, and the ratio of the in-plane piezoelectric properties ($e_{31}/e_{32}$) of the active layer of the piezoelectric patch. In this paper, it is shown that by a proper choice of b/l and of the piezoelectric properties, the moments can be cancelled, so that if one side of the triangle is clamped, a perfect point load actuation can be achieved. This requires $e_{31}/e_{32}$ to be negative, which imposes the use of interdigitated electrodes instead of continuous ones. The design of two transducers with interdigitated electrodes for perfect point load actuation on a clamped plate is verified with finite element calculations. The first design is based on a full piezoelectric ceramic patch and shows superior actuation performance than the second design based on a piezocomposite patch with a volume fraction of fibres of 86%. The results show that both designs lead to perfect point load actuation while the use of an isotropic PZT patch with continuous electrodes gives significantly different results.

Large deflection analysis of point supported super-elliptical plates

  • Altekin, Murat
    • Structural Engineering and Mechanics
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    • 제51권2호
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    • pp.333-347
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    • 2014
  • Nonlinear bending of super-elliptical plates of uniform thickness under uniform transverse pressure was investigated by the Ritz method. The material was assumed to be homogeneous and isotropic. The contribution of the boundary conditions at the point supports was introduced by the Lagrange multipliers. The solution was obtained by the Newton-Raphson method. The influence of the location of the point supports on the central deflection was highlighted by sensitivity analysis. An approximate relationship between the central deflection and the super-elliptical power was obtained using the method of least squares. The critical points where the maximum deflection may develop, and the influence of nonlinearity were highlighted. The nonlinearity was found to be sensitive to the aspect ratio. The accuracy of the algorithm was validated by comparing the central deflection with the solutions of elliptical and rectangular plates.

계면활성제/1-Hoxanol/물 혼합물의 상태도와 전기 전도도에 관한 연구

  • 오성근;김종득
    • 대한화장품학회지
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    • 제12권1호
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    • pp.34-61
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    • 1986
  • The microstructural transitions of aqueous micellar solutions of cetyltrime-thylammonium bromide and sodiumdodecyl sulfate by adding 1-hexanol were investigated, measuring the concentrations of equilibrated phases and the electrical conductivities at the low concentrations of surfactants, where the solobilities of 1-hexanol varied significantly, at 3$0^{\circ}C$ and 45$^{\circ}C$. Ternary phase diagrams of multiphase regions, constructed by liquid chromatography analysis and by counting the number of phase of samples, consisted of one three-phase region and three two-phase regions. One of the two-phase regions was found to equilibrate an aqueous micellar solution and a liquid crystal, and had a critical point between them. Near this region, the solubility curve varied abruptly, and the isotropic solution turned birefrigent. The conductivities of the single phase regions above the critical point increased up to a certain point as 1-hexanol added, and then decreased, representing the microstructural transition at the supercritical region. Further, the solubility of 1-hexanol in aqueous micellar solution was found to increase as temperature and the number of hydrophilelipophile balance of surfactants increase.

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Modelling of strain localization in a large strain context

  • Cescotto, S.;Li, X.K.
    • Structural Engineering and Mechanics
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    • 제4권6호
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    • pp.645-653
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    • 1996
  • In order to avoid pathological mesh dependency in finite element modelling of strain localization, an isotropic elasto-plastic model with a yield function depending on the Laplacian of the equivalent plastic strain is implemented in a 4-node quadrilateral finite element with one integration point based on a mixed formulation derived from Hu-Washizu principle. The evaluation of the Laplacian is based on a least square polynomial approximation of the equivalent plastic strain around each integration point. This non local approach allows to satisfy exactly the consistency condition at each integration point. Some examples are treated to illustrate the effectiveness of the method.

Analytical solutions to magneto-electro-elastic beams

  • Jiang, Aimin;Ding, Haojiang
    • Structural Engineering and Mechanics
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    • 제18권2호
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    • pp.195-209
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    • 2004
  • By means of the two-dimensional basic equations of transversely isotropic magneto-electro-elastic media and the strict differential operator theorem, the general solution in the case of distinct eigenvalues is derived, in which all mechanical, electric and magnetic quantities are expressed in four harmonic displacement functions. Based on this general solution in the case of distinct eigenvalues, a series of problems is solved by the trial-and-error method, including magneto-electro-elastic rectangular beam under uniform tension, electric displacement and magnetic induction, pure shearing and pure bending, cantilever beam with point force, point charge or point current at free end, and cantilever beam subjected to uniformly distributed loads. Analytical solutions to various problems are obtained.

Orthotropic Theory for the Prediction of Mechanical Performance in Thermally Point-bonded Nonwovens

  • Kim, Han-Seong
    • Fibers and Polymers
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    • 제5권2호
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    • pp.139-144
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    • 2004
  • The orthotropic theory is applied for the nonwoven fabrics that have a preferred orientation direction, the case if the structure is not isotropic. The polynomial regression analysis is employed to allow the attainment of more statistically meaningful information. A functional form based on the transformation rule is developed for the orthotropic approach. The predictions thus obtained are seen to be in excellent agreements with experimental data and the resulting compliances exhibit meaningful relationships for the processing conditions. The compatibility of the compliances from tensile and shear analyses has been explored prior to a practical application of the four compliances defining the in-plane strain-stress field.

CFRP적층재의 잔류피로굽힘강도애 미치는 열습의 영향 (Influence of Hygrothermals on Residual Fatigue Bending Strength of CFRP Composite Laminates)

  • 박노식;임광희;양인영
    • 한국안전학회지
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    • 제12권2호
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    • pp.27-36
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    • 1997
  • This paper evaluates the static and fatigue bending strengths of CFRP (carbon fiber reinforced plastic) laminates subjected to hygrothermals. The specimens which had different stacking composition, orthotropic and quasi-isotropic laminated plates, were prepared for this experiment. A steel ball launched by the air gun collides against CFRP laminates to generate impact damages, and the 3-point fatigue bending test is carried out by using the impacted laminates to investigate the influence of hygrothermals on the effect on the residual bending fatigue strength of CFRP laminates.

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Calculation of gamma buildup factors for point sources

  • Kiyani, Abouzar;Karami, Abbas Ali;Bahiraee, Marziye;Moghadamian, Hossein
    • Advances in materials Research
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    • 제2권2호
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    • pp.93-98
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    • 2013
  • Objective of this study is to calculate gamma buildup factors for pointed and isotropic gamma sources in depleted uranium, uranium dioxide, natural uranium, tin, water and concrete using MCNP4C code. The thickness of the media ranges from 0.5 to 10 mean-free-path (mfp) and gamma energy ranges from 0.5 to 10 MeV. Owing to the outstanding accuracy of MCNP in calculation involving gamma interaction, results fairly match those reported previously. The maximum relative error is 2%.