• Title/Summary/Keyword: 다공탄성

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Analysis of Impact Response in a Poroelastic Spinal Motion Segment FE Model according to the Disc Degeneration (다공탄성체 척추운동분절 유한요소 모델에서 추간판의 변성이 충격 거동에 미치는 영향 해석)

  • 김영은;박덕용
    • Journal of the Korean Society for Precision Engineering
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    • v.20 no.11
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    • pp.188-193
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    • 2003
  • To predict changes in biomechanical parameters such as intradiscal pressure, and the shock absorbing mechanism in the spinal motion segment under different impact duration/loading rates, a three dimensional L3/L4 motion segment finite element model was modified to incorporate the poroelastic properties of the motion segment. The results were analyzed under variable impact duration for normal and degenerated discs. For short impact duration and a given maximum compressive force, relatively high cancellous pore pressure was generated as compared with a case of long impact duration, although the amount of impulse was increased. In contrast relatively constant pore pressure was generated in the nucleus. Disc degeneration increased pore pressure in the disc and decreased pore pressure in the cancellous core, which is more vulnerable to compressive fracture compared with intact case.

Evaluation Wave Induced Liquefaction in Seabed (파랑하중에 의한 해저지반의 액상화 평가)

  • Jang, Byeong-Uk;Do, Deok-Hyeon;Song, Chang-Seop
    • Geotechnical Engineering
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    • v.9 no.4
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    • pp.17-26
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    • 1993
  • The mechanism of wave -induced stresses and liquefactions in a seabed is studied theoretically and experimentally, A constitutive equation which is governing wave -induced effective stresses and porepressures in an unsaturated seabed under the hydraulically anisotropic conditions is developed. It is learned that the effective stresses and excessive porewater pressures are governed by the conditions of waves and sedimentary layers, Especially the magnitude of effective stresses and the depth of disturbed zone induced by waves is controlled by the degree of saturation of the unsaturated seabeds.

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A poroelastic model for ultrasonic wave attenuation in partially frozen brines (부분 동결된 소금물에서의 초음파감쇠에 대한 다공성탄성 모델)

  • Matsushima, Jun;Nibe, Takao;Suzuki, Makoto;Kato, Yoshibumi;Rokugawa, Shuichi
    • Geophysics and Geophysical Exploration
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    • v.14 no.1
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    • pp.105-115
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    • 2011
  • Although there are many possible mechanisms for the intrinsic seismic attenuation in composite materials that include fluids, relative motion between solids and fluids during seismic wave propagation is one of the most important attenuation mechanisms. In our previous study, we conducted ultrasonic wave transmission measurements on an ice-brine coexisting system to examine the influence on ultrasonic waves of the unfrozen brine in the pore microstructure of ice. In order to elucidate the physical mechanism responsible for ultrasonic wave attenuation in the frequency range of 350.600 kHz, measured at different temperatures in partially frozen brines, we employed a poroelastic model based on the Biot theory to describe the propagation of ultrasonic waves through partially frozen brines. By assuming that the solid phase is ice and the liquid phase is the unfrozen brine, fluid properties measured by a pulsed nuclear magnetic resonance technique were used to calculate porosities at different temperatures. The computed intrinsic attenuation at 500 kHz cannot completely predict the measured attenuation results from the experimental study in an ice-brine coexisting system, which suggests that other attenuation mechanisms such as the squirt-flow mechanism and wave scattering effect should be taken into account.

Elastic Analysis of Orthotropic Thick Plates with Perforated Many Holes (직교 이방성 관통 다공 후판의 탄성 해석)

  • Kim, Woo-Sik;Kwun, Taek-Jin
    • Journal of Korean Association for Spatial Structures
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    • v.2 no.1 s.3
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    • pp.59-65
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    • 2002
  • The structures with many perforated openings are widely used as a load-carrying element in the fields of civil engineering works, top slab of prestressed concrete reactor vessel, petrochemical industries and the like. Perforated concrete plates are usually thick. Therefore, the effect of transverse shear deformation is not negligible. This paper describes a new analytical method of perforated plates combining both the finite element method for effective elastic constants and the usual method in solving orthotropic plate with transverse shear deformation.

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Thermoelastic Properties of Porous Metals After Material Forming Processes (다공성 금속의 성형공정 후 열탄성 계수)

  • 이종원;김진원
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2003.10a
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    • pp.217-220
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    • 2003
  • The effective thermoelastic properties of porous metals are discussed herein after each material forming process such as hot pressing or extrusion. The voids in metal matrix are assumed to be initially spherical in shape and to be distributed randomly. Once the porous material deforms plastically due to each material forming process, the voids change their shape from a sphere to an ellipsoid and align in one direction. Since the voids are compressible in nature, the void volume fraction is assumed to be decreasing during each material forming process.

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Calculating transmission loss of cylindrical silencers lined with multi-layered poroelastic sound absorbing materials using mode matching method (모드 매칭법을 이용한 다층 다공성 탄성 흠음재가 채워진 원통형 소음기의 음향투과손실 계산)

  • Lee, Jongmoo;Yang, Haesang;Seong, Woojae
    • The Journal of the Acoustical Society of Korea
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    • v.41 no.4
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    • pp.375-388
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    • 2022
  • This paper deals with the process of obtaining sound transmission loss of a cylindrical silencer lined with multi-layered poroelastic sound absorbing materials. The Biot model and the Johnson-Champoux-Allard-Lafarge (JCAL) model were used to deal with waves propagating in multi-layered poroelastic materials. The boundary conditions required for analysis of the silencer were obtained and the numerical process of finding modes was explained. A numerical experiment was conducted on the 2-layered silencer using the modes and the transmission loss converged with the first 12 modes. Finally, the mode matching method proposed in this research was validated by being compared with the results calculated from Finite Element Method (FEM) about different kinds of sound absorbing materials.

Study on an Elastic and Permeable Pavement using Scrap Tire (폐타이어 분말을 이용한 탄성 투수성 도로포장재에 관한 연구)

  • Um, Jun-Gil;Chung, Kyung-Ho;Choo, Kang;Hong, Young-Keun
    • Elastomers and Composites
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    • v.33 no.4
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    • pp.290-296
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    • 1998
  • Recycling of waste tire has been limited and very simple, few applications have been observed. This study introduces a new elastic and permeable pavement made of scrap tire. Experimental results showed that key factors affecting the compressive strength were the size of scrap tire, size of aggregate, amounts and property of binder. Also, the water permeability depended on the size of aggregate and scrap tire. The compressive strength and water permeability of the samples were 1.4 and 116 times higher than those of the conventional porous cement concrete, respectively.

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Novel Porous Materials Prepared by Repeated Directional Crystallization of Solvent (용매의 반복 방향성 결정화를 통해 제작된 새로운 다공성재료)

  • Kim, Hyun Jin;Lee, Jonghwi
    • Polymer(Korea)
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    • v.39 no.1
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    • pp.151-156
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    • 2015
  • Herein, novel porous structures were fabricated from monomer solutions of dimethylsiloxane and benzene by directional crystallization in twice. First, a honeycomb-like structure was fabricated by $1^{st}$ directional crystallization of solvent. By infiltration of the solution and subsequent $2^{nd}$ directional crystallization, novel structures of different pores in the honeycomb-like structure were fabricated. The porous materials prepared by the repeated directional crystallization have higher indentation modulus and hardness than those of the samples prepared by single directional crystallization. When a higher solution concentration was used in $2^{nd}$ directional crystallization, the maximum increase (indentation modulus: 2140% increase, indentation hardness: 2330% increase) was obtained. On the other hand, porosity and contact angle were lower in the samples from $2^{nd}$ directional crystallization than those from $1^{st}$ directional crystallization. A large decreases was observed, when a relatively high concentration was used in $2^{nd}$ directional crystallization (porosity: 21% decrease, contact angle: 36% decrease).

Preparation and Characterization of the Impregnation to Porous Membranes with PVA/PSSA-MA for Fuel Cell Applications (연료전지 응용을 위한 다공성막에 친수성 고분자의 함침을 통한 고내구성 이온교환막의 제조 및 특성 연구)

  • Lee, Bo-Sung;Jung, Sun-Kyoung;Rhim, Ji-Won
    • Polymer(Korea)
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    • v.35 no.4
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    • pp.296-301
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    • 2011
  • This study focuses on the investigation of the impregnation of poly (vinyl alcohol) (PVA) crosslinked with poly(styrene sulfonic acid-co-maleic acid) (PSSA-MA) to porous polyethylene membrane for the fuel cell application. The membranes were characterized by the measurements of the water content, contact angle, FTIR spectra, thermal gravimetric analysis, ion exchange capacity, proton conductivity, methanol permeability and elastic modulus. The existence of hydrophilic moieties in the impregnated membranes was confirmed by contact angle and FTIR measurements. The impregnated PVA/PSSAMA(90:10) membrane exhibited a higher ion exchange capacity (1.2 meq./g dry membrane) than Nafion membrane (0.91 meq./g dry membrane). Through the elastic modulus measurement, the dimensional stability of the resulting membranes was expected to increase higher than the polyethylene membranes. The methanol crossover and water content decreased even if the PSSA-MA content increased due to the reduction of the free volume.

Mechanical Characteristics of Basalt in Jeju Island with Relation to Porosity (공극률에 따른 제주도 현무암의 역학적 특성)

  • Moon, Kyoungtae;Park, Sangyeol;Kim, Youngchan;Yang, Soonbo
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.34 no.4
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    • pp.1215-1225
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    • 2014
  • Volcanic rocks formed from magma near the earth surface commonly show vesicular structures due to exsolution of gaseous phases in magma. The distinction and the amount of vesicles are greatly various, but there are few researches on the effect of volume percentage of vesicles on the mechanical properties. In this study, mechanical characteristics of volcanic rocks in relation to the porosity are investigated through experimental tests with Jeju basalt. Two methods (the buoyancy method and the caliper method) are adopted for measuring porosity. And unconfined compressive strength, elastic modulus, tensile strength, and elastic wave velocity are plotted against porosity in order to propose the empirical relations after the regression analysis. Also, unconfined compressive strength and the elastic modulus in relation to the elastic wave velocity are proposed with the analysis. In the case of vesicular rocks with more than 5% porosity, it is found that the buoyancy method provides more accurate estimation of porosity than the caliper method. The unconfined compressive strength, the elastic modulus, and the elastic wave velocity decrease curvilinearly with increasing in porosity. Also, the unconfined compressive strength and the elastic modulus increase linearly with increasing in elastic wave velocity.