• Title/Summary/Keyword: high strain rate

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Characterization of Dynamic Deformation Behavior of Al 7075-T6 at High Temperature by Using SHPB Technique (SHPB 기법을 사용한 고온에서의 Al 7075-T6 의 동적 변형 거동)

  • Lee, Ouk-Sub;Park, Jin-Su;Choi, Hye-Bin;Kim, Hong-Min
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.34 no.8
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    • pp.981-987
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    • 2010
  • The split Hopkinson pressure bar (SHPB) technique is extensively used to characterize material deformation behavior under high strain rate condition. In this study, the dynamic deformation behavior of aluminum 7075-T6 under a high strain rate and at a high temperature is investigated by using a modified SHPB set-up with the pulse shaper technique. The parameters used in the Johnson-Cook constitutive equation are determined by using the SHPB experimental results including the data on the effects of strain rate, temperature, strain hardening, and thermal softening of the material.

The High Temperature Deformation Behavior of the Wrought Superalloy 718 (단조용 초내열 718 합금의 고온 변형 거동)

  • Na, Y.S.;Choe, S.J.;Kim, H.M.
    • Analytical Science and Technology
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    • v.9 no.2
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    • pp.179-191
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    • 1996
  • In order to understand the high temperature deformation behavior of superalloy 718, a rotating grade 718 alloy has been compression tested to about 0.7 upset ratio at $927{\sim}1066^{\circ}C$ temperature range and $5{\times}10^{-4}{\sim}5{\times}10^0sec^{-1}$ strain rate. The maximum flow stress was increased with increasing strain rate, and similar behavior was observed with decreasing temperature. At low temperature and high strain rates other than $5{\times}10^{-1}sec^{-1}$, strain softening was occurred mainly by dynamic recovery and deformation twinning processes, while at high temperature and low strain rates strain softening was offseted by dynamic recrystallization. At $5{\times}10^{-1}sec^{-1}$, strain hardening was occurred due to work hardening of the dynamic recrystallized grains. Strain rate sensitivity, m, was varied with strain rates. In the case of lower strain rate tests, m was measured as 0.3 and it was observed that the deformation was mainly controlled by dynamic recrystallization. At higher strain rate, m was lowered to 0.1 and the deformation was controlled by the dynamic recovery and the deformation twinning processes.

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Dynamic deformation behavior of rubber and brass under high strain rate compressive loading (고변형률 속도 압축 하중 하에서의 고무와 황동의 동적 거동 특성)

  • 이억섭;김경준;이종원
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2003.06a
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    • pp.1491-1494
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    • 2003
  • A specific experimental method, the Split Hopkinson Pressure Bar (SHPB) technique has been widely used to determine the dynamic material properties under the impact compressive loading conditions with strain-rate of the order of 103/s∼104/s. This type of test procedure has been used to examine the dynamic response of materials in various modes of testing. In this paper, dynamic deformation behaviors of rubber materials widely used for the isolation of vibration from varying structures under dynamic loading are determined using a Split Hopkinson Pressure Bar technique.

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Dynamic deformation behavior of Ethylene Copolymer under high strain rate compressive loading (SHPB 기법을 사용한 고변형률 속도 하중하에서의 합성수지의 동적 변형 거동)

  • Lee, Jong-Won;Lee, Ouk-Sub;Hwang, Si-Won;Kim, S-Hyun
    • Proceedings of the KSME Conference
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    • 2004.04a
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    • pp.371-376
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    • 2004
  • It is well known that a specific experimental method such as the Split Hopkinson Pressure Bar (SHPB) technique is the simplest experimental technique to determine the dynamic material properties under the impact compressive loading conditions with strain-rate of the order of $10^3/s{\sim}10^4/s$. This type of experimental procedure has been widely used with proper modification on the test setups to determine the varying dynamic response of materials for the dynamic boundary conditions such as tensile and fracture as well. In this paper, dynamic compressive deformation behaviors of an Ethylene Copolymer materials widely used for the isolation of vibration from varying structures under dynamic loading are estimated using the SHPB technique.

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Effect of Strain Rate on the Mechanical Properties of High Performance Fiber-Reinforced Cementitious Composites (재하속도에 따른 고성능 섬유보강 시멘트 복합체의 역학적 특성)

  • Yun Hyun-Do;Yang Il-Seung;Han Byung-Chan;Hiroshi Fukuyama;Cheon Esther;Kim Sun-Woo
    • Proceedings of the Korea Concrete Institute Conference
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    • 2004.11a
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    • pp.29-32
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    • 2004
  • An experimental investigation of the behavior of steel cords(SC) and SC and Polyethylene(PE) hybrid fiber reinforced cementitious material under compressive and tensile loading is presented. In this experimental research, the tensile and compressive strength and strain capacity of high performance fiber-reinforced cementitious composites(HPFRCC) were selected using the cylindrical specimens. Uniaxial compressive and tensile tests have also been carried out at varying strain rates to better understand the behavior of. HPFRCC and propose the standard loading rate for compressive and tensile tests of new HPFRCC materials. The results show that there is a substantial increase in the ultimate compressive and tensile strength with increasing strain rate.

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Dynamic Deformation Behavior of Rubber and Ethylene Copolymer Under High Strain Rate Compressive Loading (SHPB기법을 사용한 고무와 합성수지의 고변형률 속도 하중 하에서의 동적 변형 거동)

  • 이억섭;이종원;김경준
    • Journal of the Korean Society for Precision Engineering
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    • v.21 no.6
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    • pp.122-130
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    • 2004
  • It is well known that a specific experimental method, the Split Hopkinson Pressure Bar (SHPB) technique is a best experimental technique to determine the dynamic material properties under the impact compressive loading conditions with strain-rate of the order of 10$^3$/s∼10$^4$/s. This type of experimental procedure has been widely used with proper modification on the test setups to determine the varying dynamic response of materials for the dynamic boundary conditions such as tensile and fracture as well. In this paper, dynamic compressive deformation behaviors of a rubber and an Ethylene Copolymer materials widely used for the isolation of vibration from varying structures under dynamic loading are estimated using a Split Hopkinson Pressure Bar technique.

Flammability Limits Variation of Opposed Flow Diffusion Flames for Different Channel Gap (채널 간격에 따른 대향류 확산화염의 가연 영역의 변화)

  • Lee, Min Jung;Kim, Nam Il
    • 한국연소학회:학술대회논문집
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    • 2012.11a
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    • pp.323-324
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    • 2012
  • Flammability limits of opposed flow diffusion flame in a narrow channel was investigated experimentally and theoretically. There were three different extinction modes corresponding to high strain rate (HSR), low strain rate (LSR) and dilution ratio (DR) limits. To investigate these limits, a theoretical study was followed by focusing on flow and heat transfer characteristics. Consequently, a dead space concept that has been used for premixed flames was important to reveal the heat loss mechanism in a narrow channel especially for LSR conditions even in the case of diffusion flames.

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Fiber blending Ratio Effect on Tensile Properties of Hybrid Fiber Reinforced Cement-based Composites under High Strain Rate (고변형속도 조건에서 섬유 혼합비가 하이브리드 섬유보강 시멘트복합체의 인장특성에 미치는 영향)

  • Son, Min-Jae;Kim, Gyu-Yong;Lee, Bo-Kyeong;Lee, Sang-Kyu;Kim, Gyeong-Tae;Nam, Jeong-Soo
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2017.11a
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    • pp.147-148
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    • 2017
  • In this study, the tensile properties of mono and hybrid fiber reinforced cement-based composite according to fiber blending ratio under the high strain rate was evaluated. Experimental results, the HSF1.5PVA0.5 shown the highest tensile strength because the PVA fiber suppressed the micro cracks in the matrix around the hooked steel fiber and improved the pull-out resistance of hooked steel fiber. Thus, DIF of strain capacity and fracture toughness of HSF1.5PVA were greatly improved. Also, the fracture toughness was greatly improved because the tensile stress was slowly decreased after the peak stress by improvement of the pull-out resistance of hooked steel fiber at strain rate 101/s.

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Rate-sensitive analysis of framed structures Part I: model formulation and verification

  • Izzuddin, B.A.;Fang, Q.
    • Structural Engineering and Mechanics
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    • v.5 no.3
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    • pp.221-237
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    • 1997
  • This paper presents a new uniaxial material model for rate-sensitive analysis addressing both the transient and steady-state responses. The new model adopts visco-plastic theory for the rate-sensitive response, and employs a three-parameter representation of the overstress as a function of the strain-rate. The third parameter is introduced in the new model to control its transient response characteristics, and to provide flexibility in fitting test data on the variation of overstress with strain-rate. Since the governing visco-plastic differential equation cannot be integrated analytically due to its inherent nonlinearity, a new single-step numerical integration procedure is proposed, which leads to high levels of accuracy almost independent of the size of the integration time-step. The new model is implemented within the nonlinear analysis program ADAPTIC, which is used to provide several verification examples and comparison with other experimental and numerical results. The companion paper extends the three-parameter model to trilinear static stress-strain relationships for steel and concrete, and presents application examples of the proposed models.

Low-temperature/high-strain rate superplasticity of two-phase titanium alloys (2상 타이타늄 합금의 저온/고속 초소성)

  • Part, C.H.;Lee, C.S.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2009.10a
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    • pp.76-79
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    • 2009
  • The current understanding for phase/grain boundary sliding and low-temperature/high-strain rate superplasticity of two-phase titanium alloys is summarized. The quantitative analysis on boundary sliding revealed increased sliding resistance on the order of $\alpha/\beta\;\ll\;\alpha/\alpha\;\approx\;\beta/\beta$ boundary, hence, led to the conclusion that approximately 50% alpha(or beta) volume fraction and/or grain refinement is beneficial for obtaining large superplastic elongation at low temperature and/or high strain rate. To predict the temperature for 50% alpha volume in various alpha/beta Ti, artificial neural network was applied. Finally, much enhanced superplasticity was achieved through grain refinement utilizing dynamic globularization.

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