• Title, Summary, Keyword: 변형률 속도

Search Result 469, Processing Time 0.052 seconds

Experimental and Numerical Analysis for Superelastic Behaviors of SMAs with Strain-rate Dependence (변형률 속도에 따른 형상기억합금 초탄성 거동의 실험 및 해석 연구)

  • Roh, Jin-Ho;Park, Jeong-In;Lee, Soo-Yong
    • Journal of the Korean Society for Aeronautical & Space Sciences
    • /
    • v.39 no.1
    • /
    • pp.9-15
    • /
    • 2011
  • The influence of the strain-rate on the superelastic behaviors of shape memory alloys (SMAs) wires is experimentally and numerically investigated. The one-dimensional SMA constitutive equations considering strain-rate effect is developed. The evolution of stress-strain curves of SMA wires is examined with various strain-rates. Results show that the superelastic behaviors of SMAs may significantly be changed depending on the variation of strain-rate.

Design and Fabrication of Split Hopkinson Pressure Bar for Dynamic Mechanical Properties of Self-reinforced Polypropylene Composite (폴리프로필렌 자기 보강 복합재의 동적 물성 구축을 위한 Split Hopkinson Pressure Bar의 설계 및 제작)

  • Kang, So-Young;Kim, Do-Hyoung;Kim, Dong-Hyun;Kim, Hak-Sung
    • Composites Research
    • /
    • v.31 no.5
    • /
    • pp.221-226
    • /
    • 2018
  • The Split Hopkinson Pressure Bar(SHPB) has been the most widely used apparatus to characterize dynamic mechanical behavior of materials at high strain rates between $100s^{-1}$ and $10,000s^{-1}$. The SHPB test is based on the wave propagation theory which was developed to give the stress, strain and strain rate in the specimen using the strains measured in the incident and transmission bars. In this study, the SHPB was directly designed and fabricated for the dynamic mechanical properties of fiber reinforced plastic (FRP) composites. In addition, this apparatus was verified for the validity by comparing the strain data obtained through the high speed camera and Digital Image Correlation(DIC) during the high strain rate compression test of the self-reinforced polypropylene composite (SRPP) specimen.

Finite Element Simulation of a Superplastic Sheet Metal Forming Process with a Pressure Cycle Control Algorithm (초소성 박판 성형 공정의 유한 요소 압력 제어 해석)

  • 한수식;양동열;이종수
    • Transactions of the Korean Society of Mechanical Engineers
    • /
    • v.15 no.5
    • /
    • pp.1563-1571
    • /
    • 1991
  • 본 연구에서는 가상일 원리로 부터 유한 요소 수식화를 updated-Lagrangian 형태로 유도하였으며, 유도된 수식화를 연속체 유한 요소로 유한 근사화 하였다. 이 때 초소성 재료의 거동은 비압축성, 비선형 점성 유ㄷ옹으로 묘사하였다. 유한 요소 프로그램은 성형 기구 해석과 하중 압력을 제어하는 기법으로 구성되어 있으며 하중 압력의 제어는 성형 시간이 최소가 되게 하기 위하여 변형률 속도 민감 계수가 최대가 되고, 국부 변형에 의한 두께 감소를 방지하며 변형률 속도는 일정하게 유지되면서 성 형이 될 수 있도록 하였다. 즉 하중 압력 제어는 상당 변형률 속도가 최대가 되게하 여 성형 시간을 최소화하게 구성하였다.개발된 유한 요소 프로그램은 정수압 벌징 가공에 적용하였으며 최적 압력 시간 선도, 성형 형상, 두께 및 두께 변형률 분포, 상 당 변형률 분포 등을 구하였다.

Effect of Strain Rate and Material Hardness on Residual Stress in Multiple Impact Shot Peening (다중충돌 쇼트피닝에서 변형률 속도와 소재 경도가 잔류응력에 미치는 영향에 관한 연구)

  • Kim, Tae-Woo;Yang, Zhao-Rui;Na, Doo-Hyun;Lee, Young-Seog
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.35 no.11
    • /
    • pp.1369-1375
    • /
    • 2011
  • Shot ball impacts to materials cause residual compressive stress on their surfaces. Improving the fatigue strength of a material that has this residual compress stress is the purpose of the shot peening process. A numerical study was performed to evaluate the effect of the strain rate sensitivity and hardness of the shot ball on the residual compressive stress. We calculated the residual compressive stress due to multiple impact shot peening using ABAQUS 6.9-1. AISI 4340 steel was the material used in this study. We compared the effects of high strain rate sensitivities and low strain rate sensitivities and found that when the material's sensitivity to the strain rate increased, the residual compressive stress decreased. In addition, the residual compressive stress of low-hardness material is higher than that of high-hardness material.

Application of Field test to the Rate-dependent relation in Constitutive model (변형률속도-의존 구성모델의 현장 시험 적용)

  • Song, Young-Sun
    • Journal of the Korea Academia-Industrial cooperation Society
    • /
    • v.9 no.2
    • /
    • pp.470-474
    • /
    • 2008
  • The rate-dependent constitutive model and the rate-independent model were analyzed for comparing with the piezocone penetration test and dissipation test. The mathematical expressions of the rate-dependent constitutive model were introduced, and the predictions using the both models were compared with the experimental results of in-situ field test. The rate-dependent model analysis gave better results than the rate-independent model analysis, that is appreciated since the process of the piezocone penetration and dissipation depends on the strain rate. Therefore, it is recommended the concept of the rate-dependent model for the prediction of soil behaviors using the field penetration test.

Asphalt Concrete Pavement Response to Moving Load and Viscoelastic Property (아스팔트 혼합물의 점탄성과 차량의 이동 속도가 포장 거동에 미치는 영향)

  • Jo, Myoung-hwan;Kim, Nakseok;Seo, Youngguk
    • Journal of The Korean Society of Civil Engineers
    • /
    • v.28 no.4D
    • /
    • pp.485-492
    • /
    • 2008
  • This study presents a viscoelastic characterization of flexible pavement subjected to moving loads. A series of field tests have been conducted on three pavement sections (A2, A5, and A8) at the Korea Expressway Corporation (KEC) test road. The effect of vehicle speed on the responses of each test section was investigated at three speeds: 25 km/hr, 50 km/hr, and 80 km/hr. During the test, both longitudinal and lateral strains were measured at the bottom of asphalt layers and in-situ measurements were compared with the results of finite element (FE) analyses. A commercial FE package, ABAQUS was used to model each test section and a step loading approximation has been adopted to simulate the effect a moving vehicle. For viscoelastic analysis, relaxation moduli of asphalt mixtures were obtained from laboratory test. Field responses reveals the strain anisotropy (i.e., discrepancy between longitudinal and lateral strains) and the amplitude of strain normally decreases as the vehicle speed increases. In most cases, lateral strain was smaller than longitudinal strain, and strain reduction was more significant in lateral direction.

  • PDF

Strain Rate-dependent Model for Anisotropic Cohesive Soils (비등방성 점성토에 있어서 변형률속도 의존적 구성모델)

  • Kim, Dae-Kyu
    • Journal of the Korean Geotechnical Society
    • /
    • v.19 no.3
    • /
    • pp.15-22
    • /
    • 2003
  • The appropriate description of the stress-anisotropy and time-dependent behavior of cohesive soils is very important in representing the real soil behavior. In this study, two constitutive relations have been incorporated based on the generalized viscous theory: one is the plastic constitutive relation adopted to capture the stress-anisotropy with a few model parameters; the other is the rate-dependent constitutive relation adopted to describe the strain rate-dependent behavior, an important time-dependent behavior in cohesive soils. The incorporated and proposed constitutive model has relatively a few model parameters and their values need not to be re-evaluated at different strain rates. The proposed model has been verified and investigated with the anisotropic triaxial test results obtained by using the artificial homogeneous specimens.

Viscoelastic Behavior of High Density Polyethylene Using High Tibial Osteotomy with Respect to the Strain Rate (근위경골절골술(HTO)용 X-밴드 플레이트에 적용되는 고밀도 폴리에틸렌(HDPE)의 변형률속도에 따른 점탄성거동)

  • Hwang, Jung-Hoon;Kim, Cheol-Woong
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.36 no.4
    • /
    • pp.431-438
    • /
    • 2012
  • The mechanical behavior of the polymeric material, HDPE depends on both time and temperature. The study of the tensile behavior at different strain rates is important in engineering design of the orthopedics device such as X-band plate. The mechanical properties and deformation mechanisms of HDPE are strongly dependent on the applied strain rate. Generally, the deformation behavior of HDPE based on the stress-strain curve is complex because of the highly inhomogeneous nature of plastic deformation, particularly that of necking. Therefore, we attempted to determine the mechanical behavior of HDPE in this study. Normally, tensile testing under various strain rates of the HDPE has been used to determine the mechanical behavior. We performed tensile tests at various strain rates (1 to 500 %/min) to analyze the viscoelastic behavior on increasing the strain rate. A tensile stress-strain curve was plotted from the data, and the point of transition was marked to calculate the transition stress, strain, and modulus.

Thermomechanical Characteristics of SMAs with Strain-rate Dependence (변형률 효과를 고려한 형상기억합금의 열-기계적 특성)

  • Roh, Jin-Ho
    • Journal of the Korean Society for Aeronautical & Space Sciences
    • /
    • v.38 no.2
    • /
    • pp.129-134
    • /
    • 2010
  • The influence of the strain-rate on the thermomechanical characteristics of shape memory alloys (SMAs) is numerically investigated. The three-dimensional SMA constitutive equations of strain-rate effect is developed. The strain-rate effect is taken into account by introducing a coupling equation between the production rate of martensite and the temperature change. For the numerical results, the SMA algorithm is implemented into the ABAQUS finite element program. Numerical simulation shows that the pseudoelasticity of SMA may significantly be changed by considering the strain-rate due to the temperature change.

Strain-rate-dependent Consolidation Characteristics of Busan Clay (부산점토의 변형률 속도 의존적인 압밀특성)

  • Kim Yun-Tae;Jo Sang-Chan;Jo Gi-Young
    • Journal of the Korean Geotechnical Society
    • /
    • v.21 no.6
    • /
    • pp.127-135
    • /
    • 2005
  • In order to analyze effects of strain rate on consolidation characteristics of Busan clay, a series of constant rate of strain (CRS) consolidation tests with different strain rate and incremental loading tests (ILT) were performed. From experimental test results on Busan clay, it was found that the preconsolidation pressure was dependent on the corresponding strain rate occurring during consolidation process. Also, consolidation curves normalized with respect to preconsolidation pressure gave a unique stress-strain curve. Coefficient of consolidation and permeability estimated from CRS test had a tendency to converge to a certain value at normally consolidated range regardless of strain rate. An increase in excess pore pressure was observed after the end of loading without change of total stress on the incremental loading test, which phenomenon is called Mandel-Cryer effect. It was also found that rapid generation of excess pore pressure took place due to collapse of soil structure as effective stress approached to preconsolidation pressure.