• 제목/요약/키워드: coefficient of restitution

검색결과 45건 처리시간 0.024초

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

  • 김태용;박진무
    • 한국정밀공학회:학술대회논문집
    • /
    • 한국정밀공학회 2000년도 추계학술대회 논문집
    • /
    • 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

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

  • 이봉현;최연선
    • 한국소음진동공학회:학술대회논문집
    • /
    • 한국소음진동공학회 2000년도 춘계학술대회논문집
    • /
    • 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

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

  • 최석정;유문식;전찬기;박선규
    • 한국구조물진단유지관리공학회 논문집
    • /
    • 제5권1호
    • /
    • 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

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

  • 한인환
    • 한국자동차공학회논문집
    • /
    • 제6권2호
    • /
    • 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

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

  • 김재환;박철우;한상용;권남진;강춘구;정영채
    • 한국소음진동공학회논문집
    • /
    • 제15권5호
    • /
    • 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.

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

  • 박철우;김재환;한상용;권남진;강춘구;정영채
    • 한국소음진동공학회:학술대회논문집
    • /
    • 한국소음진동공학회 2004년도 추계학술대회논문집
    • /
    • 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

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

  • 임종한
    • 한국인터넷방송통신학회논문지
    • /
    • 제18권2호
    • /
    • pp.217-226
    • /
    • 2018
  • 차량의 측면은 전면이나 후면과 다르게 비대칭으로 설계되어있기 때문에 측면충돌이 일어나는 경우 충돌부위에 따라 차체의 변형정도가 크게 달라진다. 충돌로 인하여 차체에 탄성 및 소성 변형이 일어날 때 운동에너지가 차체로 흡수되어 운동량이 감소하게 된다. 일반적으로 교통사고분석은 충돌 후 차량의 거동을 운동량 보존법칙으로 분석하며 차체의 변형에 따른 에너지 흡수량은 반발계수를 적용해 그 오차를 보정한다. 본 연구에서는 차체의 구조와 각 부품의 재료특성을 적용한 유한요소 차량모델을 LS-DYNA로 해석하였으며, 그 결과를 분석하여 SUV와 승용차의 측면충돌에서 차량의 접촉부위에 따른 반발계수와 충돌감지시간을 도출하였다. 최종적으로 산출된 반발계수와 충돌감지시간을 실제 교통사고 사례에 적용하였을 때 결과오차의 개선효과를 얻었다. 유한요소해석 모델을 이용하여 도출한 초기 입력값을 적용했을 때 기존의 분석기법보다 해석의 신뢰도가 높다는 결과를 얻게 되었다.

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

  • 김수태;주경진;박근종;최영휴
    • 한국기계가공학회지
    • /
    • 제21권8호
    • /
    • 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
    • /
    • 제43권3호
    • /
    • 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.