• Title/Summary/Keyword: Coefficient of Restitution

Search Result 45, Processing Time 0.029 seconds

Restitution Behaviors and Mechanical Characteristics of Strings (스트링의 반발거동과 역학적 특성)

  • 김태용;박진무
    • Proceedings of the Korean Society of Precision Engineering Conference
    • /
    • 2000.11a
    • /
    • pp.543-546
    • /
    • 2000
  • Static and dynamic experiments were done to study on the restitution behaviors of strings. The elastic and viscoelastic model were compared. To apply a linear viscoelastic model (Kelvin model) to longitudinal behaviors of strings, static and dynamic tensile tests were done. Using their results, it should be intended to acquire damped stress (Stress related to velocity), and to calculate the viscoelastic coefficient. Fixing both ends, string was pushed by the loadcell attached to the tensile tester. The experimental results were in accordance with the calculated results using the Kelvin model acquired from the results of longitudinal tensile test. But the results of falling mass experiments, the behaviors of strings were near to elastic model. The clamping condition of strings in both sides has an effected on the value of COR. The smaller contact area, the grower the value of COR.

  • PDF

Nonlinear Analysis of Beam Vibration with Impact (충격성분을 갖는 보의 진동에 대한 비선형 해석)

  • Lee, B.H.;Choi, Y.S.
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2000.06a
    • /
    • pp.455-460
    • /
    • 2000
  • Impact occurs when the vibration amplitude of a mechanical component exceeds a given clearance size. Examples of these mechanical systems include impact dampers, gears, link mechanism, rotor rub, and so on. The vibration due to impact has strong non-linear characteristics, which cannot be predicted by usual linear analysis. The designs of mechanical systems with impacts should be done on the basis of overall dynamic characteristics of the systems. In this paper, the nonlinear behaviors of a beam with a periodically moving support and a rigid stop are investigated numerically and experimentally. The beam vibration with impact is modeled by the equations of motion containing piecewise linear restoring forces and by the coefficient of restitution, respectively. Experimental and numerical results show jump phenomena and higher-harmonic vibrations. The effects between the increase of stiffness during impact and the coefficient of restitution are investigated through the comparison of the experimental and numerical results.

  • PDF

Dynamics Analysis of Concrete Bridges at Expansion Joints Considering Pounding (신축이음부에서 충돌을 고려한 콘크리트 교량의 동적해석)

  • Choi, Suk-Jung;Yoo, Moon-Sig;Jeon, Chan-Ki;Park, Sun-Kyu
    • Journal of the Korea institute for structural maintenance and inspection
    • /
    • v.5 no.1
    • /
    • pp.176-187
    • /
    • 2001
  • Most bridges have expansion joints to accommodate thermal expansion and contraction without inducing large forces in the bridges. To evaluate the effects of earthquake-induced at expansion joints of concrete bridges, the first part of this paper deals with a collinear impact between concrete segments, which have the same cross section but different lengths. Especially, impact force, momentum, strain energy and kinetic energy are formulated in mathematically. These results are then used in the second part of this paper to simulate a realistic yet simple analysis of seismic pounding in concrete bridges. Analysis of seismic pounding in idealized concrete bridges is carried out by using a simple lumped-mass model and rationally determined values of the coefficient of restitution and the duration of impact.

  • PDF

Impact Analysis for Vehicle Accident Reconstruction (자동차 사고 재고성을 위한 충돌 해석)

  • 한인환
    • Transactions of the Korean Society of Automotive Engineers
    • /
    • v.6 no.2
    • /
    • pp.178-190
    • /
    • 1998
  • We have developed a planar impact model with a capability of reverse calculation to reconstruct various types of automobile collisions. This topic is the main part of what is referred to as accident reconstruction. The model uses the principle of impulse and momentum, and introduces a restitution coefficient and an impulse ratio at the impact center. Based on the car-to-car collision test results, we present how to estimate the restitution coefficient and the impulse ratio from some impact conditions. To validate the model and improve its reliability in accident analysis, the collision analysis has been performer with the estimated parameters. The analysis and experimental results agree well in the kinetic energy loss and the post-impact velocity.

  • PDF

Research for Performance Improvement of Impact Hammer Drill (충격 햄머 드릴의 성능향상을 위한 연구)

  • Kim, Jeahwan;Park, Cheolwoo;Han, Sangyong;Guan, Namjin;Kang, Chungu;Jung, Youngchae
    • Transactions of the Korean Society for Noise and Vibration Engineering
    • /
    • v.15 no.5 s.98
    • /
    • pp.536-541
    • /
    • 2005
  • This paper Presents the performance test of an impact hammer drill in conjunction with the parameter consideration of coefficient of restitution, lubrication and friction, pressure leakage, vibration damper and production quality. Novel measurement setups are innovated in order to get the Parameter data. The measured data are compared with the computational results, and this comparison gives a confidence on the computational model, which can be used for a optimal design of impact hammer drills.

Research for performance improvement of impact hammer drill (충격 헤머 드릴의 성능향상을 위한 연구)

  • Park, Cheol-Woo;Kim, Jea-Hwan;Han, Sang-Yong;Guan, Nam-Jin;Kang, Chun-Gu;Jung, Young-Chae
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2004.11a
    • /
    • pp.333-336
    • /
    • 2004
  • This paper presents performance of the impact hammer drill with coefficient of restitution, lubrication and friction, pressure leakage, damper efficiency and the general quality test. The novel measurement systems are introduced in order to get the reasonable data. The mechanism of strikers with inner pressure is revealed in the general quality test. Due to these factors we are able to make the computational analysis correctly.

  • PDF

A Study on the Side Impact Characteristics Occurred from SUV-to-Passenger Car using LS-DYNA (LS-DYNA를 이용한 SUV와 승용차의 측면충돌 특성에 대한 연구)

  • Lim, Jong-Han
    • The Journal of the Institute of Internet, Broadcasting and Communication
    • /
    • v.18 no.2
    • /
    • pp.217-226
    • /
    • 2018
  • Since the sides of a vehicle are designed asymmetrically unlike its front or rear, the degree of deformation of the car body greatly differs depending on the site of collision if a broadside collision takes place. When elastic deformation and plastic deformation occur in the car body occur due to a collision, the kinetic energy is absorbed into the body, and the momentum decreases. Generally, an analysis of traffic accidents analyzes the vehicle's behavior after a collision by the law of momentum conservation and corrects the error of the amount of energy absorption due to the deformation of the car body, applying a restitution coefficient. This study interpreted a finite element vehicle model applying the structure of the car body and the material properties of each part with LS-DYNA, analyzed the result and drew the restitution coefficient and the depth of penetration according to the contact area of the vehicle in a broadside collision between an SUV and a passenger car. When the finally calculated restitution coefficient and depth of penetration were applied to the examples of the actual traffic accidents, there was an effect on the improvement of the error in the result. It was found that when the initial input value, drawn using the finite element analysis model, it had a higher reliability of the interpretation than that of the existing analysis techniques.

Mechanical Vibration Characteristics Analysis of a Counterblow Hammer Press in the Forging Process (카운터블로 해머 프레스 단조공정의 기계진동 특성 해석)

  • Kim, Soo Tae;Ju, Gyeong Jin;Park, Geon Jong;Choi, Young Hyu
    • Journal of the Korean Society of Manufacturing Process Engineers
    • /
    • v.21 no.8
    • /
    • pp.43-52
    • /
    • 2022
  • The vibration characteristics of a hammer press are important parameters for machine design and production control. In this study, a counterblow hammer press was mathematically modelled as a mass-spring-damper system in order to analyze its vibration characteristics. The forging efficiency was theoretically derived as a function of the mass ratio, momentum ratio, and the coefficient of restitution And the effects of the mass ratio, momentum ratio and the restitution coefficient on the forging efficiency were also investigated for two particular cases of the unit mass ratio and unit momentum ratio. Additionally, the vibration responses of the counterblow hammer press due to the ram colliding impact were analyzed, and the force transmitted to the foundation through the mounting unit was determined.

Measurement of Mechanical and Physical Properties of Pepper for Particle Behavior Analysis

  • Nam, Ju-Seok;Byun, Jun-Hee;Kim, Tae-Hyeong;Kim, Myoung-Ho;Kim, Dae-Cheol
    • Journal of Biosystems Engineering
    • /
    • v.43 no.3
    • /
    • pp.173-184
    • /
    • 2018
  • Purpose: This study was conducted to investigate the mechanical and physical properties of a Korean red pepper variety for particle behavior analysis. Methods: Poisson's ratio, modulus of elasticity, shear modulus, density, coefficient of restitution, and coefficient of friction were derived for "AR Legend," which is a domestic pepper variety. The modulus of elasticity and Poisson's ratio were measured through a compression test using a texture analyzer. The shear modulus was calculated from the modulus of elasticity and Poisson's ratio. The density was measured using a water pycnometer method. The coefficient of restitution was measured using a collision test, and the static and dynamic friction coefficients were measured using a inclined plane test. Each test was repeated 3-5 times except for density measurement, and the results were analyzed using mean values. Results: Poisson's ratios for the pepper fruit and pepper stem were 0.295 and 0.291, respectively. Elastic moduli of the pepper fruit and pepper stem were $1.152{\times}10^7Pa$ and $3.295{\times}10^7Pa$, respectively, and the shear moduli of the pepper fruit and pepper stem were $4.624{\times}10^6Pa$ and $1.276{\times}10^7Pa$, respectively. The density of the pepper fruit and the pepper stem were $601.8kg/m^3$ and $980.4kg/m^3$, respectively. The restitution coefficients between pepper fruits, pepper stems, a pepper fruit and a pepper stem, a pepper fruit and plastic, and a pepper stem and plastic were 0.383, 0.218, 0.277, 0.399, and 0.148, respectively. The coefficients of static friction between pepper fruits, pepper stems, a pepper fruit and a pepper stem, a pepper fruit and plastic, and a pepper stem and plastic were 0.455, 0.332, 0.306, 0.364, and 0.404, respectively. The coefficients of dynamic friction between a pepper fruit and plastic and a pepper stem and plastic were 0.043 and 0.034, respectively.