• Title/Summary/Keyword: Dynamic compression behavior

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High Strain Rate Compression Behavior of EPP Bumper Foams (변형률 속도에 따른 EPP Foam의 대변형 동적 압축 특성에 관한 연구)

  • Choi, Ki-Sang;Kang, Woo-Jong;Kim, Gi-Hoon;Kim, Seong-Kun
    • Transactions of the Korean Society of Automotive Engineers
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    • v.17 no.4
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    • pp.118-125
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    • 2009
  • Bumper is designed to protect the automotive frame without damage at low velocity. Expanded polypropylene (EPP) foam is used in the bumper as an energy absorbing material. In order to exactly predict the energy absorbing performance of the foam material under impact loading condition, it is important to use high strain rate material properties. In this study, a new apparatus for dynamic compression tests was developed to investigate the high strain rate behavior of EPP foams. Three kinds of EPP foams which have different expansion ratios were tested to investigate the quasi-static and dynamic compression behavior. Quasi-static compressions were performed at low strain rates of 0.001/s, 0.1/s and 1/s. The dynamic compressions were carried out at high strain rates of 50/s and 100/s with the developed apparatus. It was observed that the EPP foam has significant strain rate effect as compared to quasi-static behavior.

Analysis and Experiment of the Dynamic Characteristics of Rubber Materials for Anti-Vibration under Compression (압축하중을 받는 방진고무의 동특성 해석 및 실험)

  • 김국원;임종락;한용희;손희기;안태길
    • Journal of KSNVE
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    • v.8 no.5
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    • pp.900-907
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    • 1998
  • Rubber materials are extensively used in various machine design application, mainly for vibration/shock/noise control devices. Over the years an enormous effort has been put into developing procedures to provide properties of rubber material for design function. However, there are still a lot of difficulties in the understanding of dynamic characteristics of the rubber components in compression. In this paper, the dynamic characteristics of rubber materials for anti-vibration under compression were investigated. Dynamic and static tests for rubber material with 3 different hardness were performed. In dynamic tests, non-resonance method, impedance method, was used to obtain the complex modulus(storage modulus and loss factor) and the effects of static pre-strain on the dynamic characteristics were investigated. Also, a relation equation between linear dynamic and nonlinear static behavior of rubber material was discussed and its usefulness to predict their combined effects was investigated.

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Analysis of the Dynamic Behavior and Characteristics of the CNG Compressor Considering Bearing Characteristics (베어링 특성을 고려한 CNG 압축기의 동적 거동 및 동특성 해석)

  • Kim, Tae-Jong
    • Tribology and Lubricants
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    • v.22 no.6
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    • pp.342-349
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    • 2006
  • In this study, a dynamic behavior of rotor-bearing system used in CNG compressor has been investigated using the combined methodologies of finite elements and transfer matrices. The finite element is formulated including the field element for a shaft section and the point element for roller bearings. The Houbolt method is used to consider the time march for the integration of the system equations. The transient whirl response of rotating shaft supported on roller bearings is obtained, considering compression forces and unbalance forces at eccentric crank-pin part. And, the steady state displacements of the rotor are compared with a variation in stiffness coefficient of roller bearings. Results show that the loci of crankshaft considering unbalance forces and external compression forces are more severe in whirl motion than with only unbalance forces.

Dynamic Behavior Analysis of a Crankshaft-Bearing System in Variable Speed Reciprocating Compressor (가변속 왕복동형 압축기 크랭크축-베어링계의 동적 거동 해석)

  • 김태종
    • Tribology and Lubricants
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    • v.17 no.6
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    • pp.426-434
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    • 2001
  • The hermetic reciprocating compressor driven by the BLDC motor rotating with variable speeds, is modelled and analyzed for dynamic characteristics. The governing equations of piston, connecting rod and crank-shaft of the reciprocating compression mechanism and characteristics of driving torque of the motor are obtained. Dynamic behavior of the crankshaft supported on 2 journal bearings is analyzed considering compression load and eccentric unbalance for the 4 rotating speeds of crankshaft. And. reaction forces generated from oil film in the journal bearings are analyzed under transient condition using Reynolds' equation. To take into account the dynamic characteristics depending on the variable rotating speeds, comparison on the dynamic behavior of crank-shaft is made for the 4 operating modes of the compressor. Results show that the magnitude of crankshaft locioperating on the lower rotating speeds is more larger than the higher ones due to reduction of inertia force of the reciprocating piston.

Analysis of the Dynamic Behavior and Lubrication Characteristics of a Small Reciprocating Compressor (소형 왕복동 압축기의 동적 거동 및 윤활특성 해석)

  • Kim, Tae-Jong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.27 no.7
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    • pp.1138-1145
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    • 2003
  • In this paper, a study on the dynamic behavior and lubrication characteristics of a reciprocating compression mechanism used in small refrigeration compressor is performed. In the problem formulation of the compressor dynamics, the viscous frictional force between piston and cylinder wall is considered in order to determine the coupled dynamic behaviors of piston and crankshaft. The solutions of the equations of motion of the reciprocating mechanism along with the time dependent Reynolds equations for the lubricating film between piston and cylinder wall and oil films of the journal bearings are obtained simultaneously. The hydrodynamic forces of journal bearings are calculated using finite bearing model and Gumbel boundary condition. And, a Newton-Raphson procedure was employed in solving the nonlinear equations of piston and crankshaft. The results explored the effects of design parameters on the stability and lubrication characteristics of the compression mechanism.

Dynamic Behavior Analysis of Rotor-Bearing System Under External Forces in Swash Plate Compressor (외부 가진력을 고려한 사판식 압축기 회전축-베어링계의 동적 거동 해석)

  • 김태종
    • Tribology and Lubricants
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    • v.17 no.1
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    • pp.56-63
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    • 2001
  • The dynamic behavior of rotor-bearing system used in swash plate compressor has been investigated using the combined methodologies of finite elements and transfer matrices. The finite element is formulated including the field element for a shaft section and the point element for swash plate, disk pulley and bearings. The Houbolt method is used to consider the time march for the integration of the system equations. The transient whirl response of rotating shaft supported on roller bearings is obtained, considering compression forces and unbalance forces at swash plate and driving pulley. And, the steady state displacements of the rotor are compared with a variation in unbalance mass. Results show that the loci of rotating shaft considering unbalance forces and external compression forces are more severe in flutter motion than with only unbalance forces.

Deformation Behavior and Dynamic Recrystallization of Torsion-Tested Alloy 718 (Alloy718의 비틀림변형과 동적재결정)

  • Park, N.K.;Kim, C.H.;Kim, N.Y;Lee, D.G.;Yeom, J.T.
    • Transactions of Materials Processing
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    • v.15 no.8 s.89
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    • pp.591-596
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    • 2006
  • Torsion testing was employed to investigate the deformation and recrystallization behavior of coarse-grained Alloy 718, and the results are compared with the compression testing results. Mechanical testing was conducted on bulk Alloy718 samples within the temperature ranges, $1000^{\circ}C{\sim}1100^{\circ}C$. The strain gradient formed in the torsion specimens resulted in a recrystallization behavior which varied along the radial direction from the center to the surface. The flow curves based on effective stress and effective strain as obtained by Fields and Backofen's isotropic deformation theory and the dynamic recrystallization within the compression tested samples and torsion tested samples are different. The different deformation and recrystallization behavior can be rationalized by the fact that the deformation in the coarse-grained torsion specimens is not uniform and thus the strain gradient within the specimens cannot be analytically predicted by FE simulation. Thus, the extent of recrystallization cannot be properly predicted by the established recrystallization equations based on compression tests.

High Temperature Deformation Behavior of Al-Zn-Mg-Based New Alloy Using a Dynamic Material Model

  • Jang, Bong Jung;Park, Hyun Soon;Kim, Mok-Soon
    • Metals and materials international
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    • v.24 no.6
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    • pp.1249-1255
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    • 2018
  • High temperature compression tests for newly developed Al-Zn-Mg alloy were carried out to investigate its hot deformation behavior and obtain deformation processing maps. In the compression tests, cylindrical specimens were deformed at high temperatures ($300-500^{\circ}C$) and strain rates of 0.001-1/s. Using the true stress-true strain curves obtained from the compression tests, processing maps were constructed by evaluating the power dissipation efficiency map and flow instability map. The processing map can be divided into three areas according to the microstructures of the deformed specimens: instability area with flow localization, instability area with mixed grains, and stable area with homogeneous grains resulting from continuous dynamic recrystallization (CDRX). The results suggest that the optimal processing conditions for the Al-Zn-Mg alloy are $450^{\circ}C$ and a strain rate of 0.001/s, having a stable area with homogeneous grains resulting from CDRX.

Analysis and Experiment of the Dynamic Characteristics of Rubber Materials for Anti-Vibration under Compression (압축하중을 받는 방진고무의 동특성 해석 및 실험)

  • 김국원;임종락;한용희;손희기;안태길
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 1998.04a
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    • pp.602-607
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    • 1998
  • Rubber materials are extensively used in various machine design application, mainly for vibration/shock/noise control devices. Over the years an enormous effort has been put into developing procedures to provide properties of rubber material for design function. However, there are still a lot of difficulties in the understanding of dynamic characteristics of the rubber components in compression. In this paper, the dynamic characteristics of rubber materials for anti-vibration under compression were investigated. Dynamic and static tests for rubber material with 3 different hardness were performed. In dynamic tests, non-resonance method, impedance method, was used to obtain the complex modulus (storage modulus and loss factor) and the effects of static pre-strain on the dynamic characteristics were investigated. Also, a relation equation between linear dynamic and nonlinear static behavior of rubber material was discussed and its usefulness to predict their combined effects was investigated.

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The Effect of Microstructure on the Static and Dynamic Deformation Behavior of Ti-6Al-4V Alloy (Ti-6Al-4V 합금의 미세조직에 따른 정적 및 동적 변형에 관한 연구)

  • Lee D. G.;Lee Y. H.;Lee S. H.;Hur S. M.;Lee C. S.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2001.10a
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    • pp.277-280
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    • 2001
  • The effects of a -phase morphology on the static and dynamic deformation behavior of a Ti-6Al-4V alloy was investigated in this study. Static tension test, static and dynamic tension test and hot compression test were conducted on three microstructures of Ti-6Al-4V alloy, i.e., equiaxed, widmanstatten and bimodal microstructures. Fracture surfaces of all three microstructures represented ductile fracture appearance, though the formation of adiabatic shear bands was noticed at dynamic torsion test. The susceptibility of forming adiabatic shear bands was greatest in the equiaxed microsoucture and lowest in the bimodal microstructure, which was evidenced by hot compression test.

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