• 제목/요약/키워드: Dynamic physical properties

검색결과 338건 처리시간 0.032초

Understanding of dynamic system properties in the frequency domain using bond graphs (본드선도를 이용한 동적시스템의 주파수역 특성이해)

  • Park, Jeon-Soo;Kim, Jong-Shik
    • Transactions of the Korean Society of Mechanical Engineers A
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    • 제22권4호
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    • pp.801-810
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    • 1998
  • Modeling and analysis of dynamic systems generally demand their resutls to be interpreted each other with a physical sense. It sometimes requires that there should exist a unified tool in the treatment of dynamic systems which can be applied to both their modeling and analysis equally. This paper shows how models just after the progress of modeling via bond graph standards are converted to ones which are appropriate for analyzing a dynamic system in the frequency domain. Four bond graph prototypes are introduced to obtain frequency properties of dynamic systems such as zero stability, relative order, zero and pole dynamics, etc. directly from bond graphs, and the method are proposed which reduces nearly all models of bond graph standards to one of the prototypes without any change of physical similarity. This procedure as a tool for the structural reduction of bond graphs and finding frequency properties of a dynamic system is further investigated to survey its effectiveness through an example.

The Study on the Properties of EPDM/NR Blends (EPDM/NR 블랜드의 물성에 관한 연구)

  • Go, Jin-Hwan;Park, Sung-Soo
    • Elastomers and Composites
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    • 제29권2호
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    • pp.121-130
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    • 1994
  • The physical properties of rubber blend between natural rubber(NR) and ethylene propylene diene terpolymer(EPDM) were investigated as a study of EPDM composite materials. For EPDM/NR blends, the effects of ethylene and diene contents in EPDM, blend ratio, dicumyl peroxide(DCP) curing system on the physical properties, interfacial adhesion force and dynamic crack growth etc. were studied. EPDM/NR blends loaded with carbon black were prepared by mechanical mixing and cured by plate heating cure press. Crosslinking density was measured by swelling method with toluene. The physical properties of all blends were measured with Instron, fatigue to failure(FTF), Demattia flex cracking tester(DMFC), scanning electron microscopy (SEM), etc. As the ethylene and diene contents in EPDM increased, the physical properties, such as dynamic crack growth, adhesion to other component were increased too. Interfacial adhesion force of EPDM/NR blends to dissimilar layer was improved by the use of optimum peroxide curing system.

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Structure and Properties of Segmented Block Copolyetheresters Based on PBT and PTMGT. 2. Mechanical and Dynamic Mechanical Properties

  • Jeon, Byoung-Yeol;Baik, Doo-Hyun
    • Proceedings of the Korean Fiber Society Conference
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    • 한국섬유공학회 1998년도 가을 학술발표회논문집
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    • pp.33-36
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    • 1998
  • Segmented block copolyetheresters defined as copolymers having sequences of alternating polyester hard blocks and polyether soft blocks create labile physical cross-links upon crystallization of hard polyester blocks Since the nature of the physical interlocking is a crystallite formed exclusively from the crystallizable hard segment, the hard segment content (HSC) and hard segment length (HSL) will play an important role in determining the properties such as mechanical property and dynamic mechanical property. (omitted)

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Comparison of Dynamic Balance Ability and Leg Muscle Properties during Bulgarian Split Squat Exercises using the Visual Block and Unstable Support Plane (시각 차단과 불안정한 지지면을 이용한 불가리안 스플릿 스쿼트 운동 시 동적 균형 능력과 근속성의 비교)

  • Jin-hyun Yang;Gyo-hyeon Lee;Kyung-ho Park;Soo-kyoung Park
    • The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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    • 제29권1호
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    • pp.41-52
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    • 2023
  • Background: Bulgarian split squat (BSS) is beneficial to improve dynamic balance ability and muscle activity of lower extremities, however its effects have not been fully investigated. Therefore, this study aimed to compare changes in dynamic balance ability and muscle properties according to various modifications of BSS exercises. Methods: Thirty healthy male volunteers participated in this study, and they were randomly divided into three different groups. The subjects performed the BSS exercise either on a stable surface with the eyes opened (n=10) or eyes closed (n=10), and on an unstable support plane with eyes opened (n=10) conditions, respectively. Dynamic balance ability was measured via Biodex balance system under the eyes-opened and closed conditions. Additionally, muscle properties of the rectus femoris (RF), vastus medialis (VM) and vastus lateralis (VL) were evaluated. Results: Dynamic balance ability did not show the significant differences among the groups that performed the BSS exercises. However, in the Unstable group, there were significant differences in the overall stability index and anterior posterior stability index under the eyes-closed condition between pre-exercise and post-exercise. In comparison of muscle properties according to the groups, RF muscle showed a significant difference in amount of change of elasticity (p=.038). Additionally, there were significant changes in post measurements of VM muscle tone (p=.016), stiffness (p=.012) and elasticity (p=.002). VL muscle, however had no significant differences in muscle properties. Conclusion: These results indicate that BSS exercises could induce the alteration of RF and VM muscle properties, in particular VM muscle which is susceptible to weakness. Thus, BSS could be applied in various ways as an effective rehabilitation exercise.

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Physical and Chemical Properties of Silk Fiber Treated with Calcium Nitrate (질산칼슘 처리농도에 따른 수축견사의 이화학적 특성)

  • 이광길;이용우
    • Journal of Sericultural and Entomological Science
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    • 제40권1호
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    • pp.70-77
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    • 1998
  • This study was carried out in order to find out the relationship between physical and chemical properties of silk fiber treated by concentrated calcium nitrate solution. The tensile, thermal and dynamic mechanical properties are also examined on Ca(NO3)2 treated silk fibers. The tensile properties of silk fibers treated by calcium nitrate changed with a concentration. The thermal behavior were also affected by the concentration of calcium nitrate. The degradation temperature (endotherms) and glass transition temperature shifted to lower temperature as the treated concentration increased. It is thought that the physical properties are strongly related to the structure and morphology of Ca(NO3)2 treated silk fibers. As a result, these give property changes with a concentration dependence.

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Dynamic characteristics of CFRP-Strengthened wooden beams: Experimental and numerical study

  • Nur Sunar;Habib Uysal
    • Structural Engineering and Mechanics
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    • 제89권3호
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    • pp.323-334
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    • 2024
  • Physical and chemical factors can cause traditional timber constructions to lose structural integrity. Knowing the dynamic properties of the building components is vital to avoid damage to the buildings from dynamic effects, a subset of physical effects. In this work, spruce and scotch pine wooden beams that had been strengthened in three distinct ways with carbon fiber strengthened polymer (CFRP) were investigated for changes in their dynamic properties. For this, CFRP was used to strengthening unstrengthened wooden beams in the form of bottom confinement, U-shaped confinement, and full confinement after the dynamic parameters of the beams were determined. By using experimental modal analysis with both free-free and fixed-fixed boundary conditions, the beams'initial natural frequencies were identified.

Resonance Test for Dynamic Physical Properties of Concrete with Recycling Materials (공명진동시험을 통한 재활용재 혼입 콘크리트의 동적 물성치 측정)

  • 박용구;정영수
    • Proceedings of the Korea Concrete Institute Conference
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    • 한국콘크리트학회 1998년도 가을 학술발표회 논문집(I)
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    • pp.111-116
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    • 1998
  • Most previous wave tests for concrete have been done to evaluate static material properties, and thus there are less works to investigate dynamic material characteristics of concrete, which should be few in Korea. The objective of this experimental work is to investigate dynamic material characteristics of concrete, such as dynamic elastic modulus, dynamic shear modulus, first resonant frequency, dynamic poisson's ratio and etc. A dynamic Signal Analyzer has been used to perform the wave analysis for various dynamic material properties of test specimen. First Fourier transform technique has been carried out on various wave data acquired by the Resonant Column method, which is a kind of nondestructive tests. Wave analysis has been performed based on KS F2437, which is similar to ASTM C607-71 and is identical to JIS A 1127-1976.

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Evolution of dynamic mechanical properties of heated granite subjected to rapid cooling

  • Yin, Tubing;Zhang, Shuaishuai;Li, Xibing;Bai, Lv
    • Geomechanics and Engineering
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    • 제16권5호
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    • pp.483-493
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    • 2018
  • Experimental study of the deterioration of high-temperature rock subjected to rapid cooling is essential for thermal engineering applications. To evaluate the influence of thermal shock on heated granite with different temperatures, laboratory tests were conducted to record the changes in the physical properties of granite specimens and the dynamic mechanical characteristics of granite after rapid cooling were experimentally investigated by using a split Hopkinson pressure bar (SHPB). The results indicate that there are threshold temperatures ($500-600^{\circ}C$) for variations in density, porosity, and P-wave velocity of granite with increasing treatment temperature. The stress-strain curves of $500-1000^{\circ}C$ show the brittle-plastic transition of tested granite specimens. It was also found that in the temperature range of $200-400^{\circ}C$, the through-cracks induced by rapid cooling have a decisive influence on the failure pattern of rock specimens under dynamic load. Moreover, the increase of crack density due to higher treatment temperature will result in the dilution of thermal shock effect for the rocks at temperatures above $500^{\circ}C$. Eventually, a fitting formula was established to relate the dynamic peak strength of pretreated granite to the crack density, which is the exponential function.

A Study on the Physical Properties of Recycled Asphalt Mixtures Using Glass Fiber Reinforcement (유리섬유 보강재를 이용한 재활용 아스팔트 혼합물의 물리적 특성에 관한 연구)

  • Park, Ki Soo;Yoo, Pyeong Jun
    • International Journal of Highway Engineering
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    • 제20권4호
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    • pp.27-34
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    • 2018
  • PURPOSES : The objective of this study is to evaluate the physical properties of recycled asphalt mixtures reinforced with glass fiber. METHODS : Firstly, mixing design was conducted on recycled asphalt mixture for use of 50% recycled aggregate. Various laboratory tests were performed on four types of recycled asphalt mixtures with different glass fiber content to evaluate the physical properties. The laboratory tests include indirect tensile strength test, dynamic modulus test, Hamburg wheel tracking test and tensile-strength ratio to evaluate cracks, rutting and moisture resistance of mixtures. RESULTS : The indirect tensile strength of fiber reinforced glass increased about 139.4%. As a result of comparing the master curves obtained by the dynamic modulus test, the elasticity was low in the low temperature region and high in the high temperature region when the glass fiber was reinforced. The glass fiber contents of PEGS 0.3%, Micro PPGF 0.1% and Macro PPGF 0.3% showed the highest moisture resistance and rutting resistance. CONCLUSIONS : The test results show that use of glass fiber reinforcement can increase the resistance to cracking, rutting, and moisture damage of asphalt mixtures. It is also necessary to validate the long-term performance of recycled asphalt mixtures with glass fiber using full scale pavement testing and field trial construction.

The Study of Optimized Compounds Containing Silica and Coupling Agent to Improve the Physical Properties of Rubber Compounds (고무물성 향상을 위한 실리카 및 실란 커플링제의 최적배합에 관한 연구)

  • Oh, Sae-Chul;Go, Jin-Hwan;Lee, Seag;Park, Nam-Cook
    • Elastomers and Composites
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    • 제30권2호
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    • pp.112-121
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    • 1995
  • The physical properties of rubber compounds containing silica and siliane coupling agent in order to replace the carbon black and prepare for environmental regulation showed improved dynamic properties(rebound, heat build-up, $60^{\circ}C\;tan\;{\delta}$), but the abrasion resistance did not improve compared with the compounds containing carbon black. Also, curing retardation because of coherent structure of silica improved by the addition of DEG, but the mixing step change of activators did not so much improve the static and dynamic properties of the compounds containing high synthetic rubber, the status of mixing and dispersion showed that the compounds containing carbon black was much better than the compounds containing silica by TEM investigation.

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