• 제목/요약/키워드: Hertz 접촉 모델

검색결과 11건 처리시간 0.025초

부품간의 접촉을 고려한 유연체모델을 이용한 엔진 밸브트레인의 동특성 해석 (Dynamic Analysis of Engine Valve Train with Flexible Multibody Model Considering Contact between Components)

  • 황원걸;성원석;안기원
    • 한국자동차공학회논문집
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    • 제19권1호
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    • pp.125-132
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    • 2011
  • The dynamic characteristics of valve train are responsible for the dynamic performances of engine. We derived the equation of motion for 6 degrees of freedom model of the valve train. Computer model is also developed with flexible multibody model considering contact between components. The simulation results with these two models are compared with experimental results. We investigated the effect of the two spring models, TSDA (Translational Spring Damper Actuator) element and flexible body model, on the valve behavior and spring force. It is found that the dynamic behavior of the two models are not very different at normal operational velocity of the engine. By modeling contact between cam and tappet, the stress distributions of the cam were found. Using stress distribution obtained, contact width and contact stresses of the cam surface were calculated with Hertz contact theory.

역동역학을 이용한 충격을 받는 보의 충격력 복원 및 충격모델의 변수 파악 (Impact Force Roconstruction and Impact Model Identification Using Inverse Dynamics of an Impacted Beam)

  • 박형순;박윤식
    • 대한기계학회논문집
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    • 제19권3호
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    • pp.623-630
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    • 1995
  • The impulse response functions (force-strain relations) for Euler-Bernoulli and Timoshenko beams are considered. The response of a beam to a transverse impact force is numerically obtained with the convolution approach using the impulse response function obtained by Laplace transform. Using this relation, the impact force history is determined in the time domain and results are compared with those from Hertz's contact law. The parameters of timpact force model are identified using the recovered force and compared with the Hertz's contact model. In order to verify the proposed algorithm, measurements were done using an impact hammer and a steel ball drop test and these results are also compared with the simulated values.

입자 패킹 공정에 대한 접촉모델별 이산요소법 해석 (Analysis of Particle Packing Process by Contact Model in Discrete Element Method)

  • 유재희;박준영
    • 한국기계가공학회지
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    • 제18권3호
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    • pp.59-65
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    • 2019
  • In many industries, particle packing is adopted quite frequently. In the particle packing process, the Discrete Element Method (DEM) can analyze the multi-collision of particles efficiently. Two types of contact models are frequently used for the DEM. One is the linear spring model, which has the fastest calculation time, and the other is the Hertz-Mindlin model, which is the most frequently used contact model employing the DEM. Meanwhile, very tiny particles in the micrometer order are used in modern industries. In the micro length order, surface force is important to decreased particle size. To consider the effect of surface force in this study, we performed a simulation with the Hertz-Mindlin model and added the Johnson-Kendall-Roberts (JKR) theory depicting surface force with surface energy. In addition, three contact models were compared with several parameters. As a result, it was found that the JKR model has larger residual stress than the general contact models because of the pull-off force. We also validated that surface force can influence particle behavior if the particles are small.

LM 볼가이드의 마찰력 정식화 (Formulation of Friction Forces in LM Ball Guides)

  • 오광제;김경호;박천홍;정성종
    • 대한기계학회논문집A
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    • 제40권2호
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    • pp.199-206
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    • 2016
  • LM 볼가이드는 구름접촉을 갖는 이송시스템의 핵심요소로서 공작기계, 반도체 장비, 로봇 등 정밀기계에 널리 사용된다. 그러나 LM 볼가이드에서 발생하는 마찰력은 마찰열을 유발하여 위치 정도를 저하시키고 강성과 예압 변화를 야기한다. 이런 영향을 정확하게 분석하여 정밀 기계설계에 응용하기 위해서는 마찰력 모델의 정식화가 요구된다. 본 논문에서는 구름마찰, 점성마찰, 슬립마찰을 고려한 LM 볼가이드의 정확한 마찰력 모델을 유도한다. 그리고 다양한 조립, 부하 및 속도 조건에서 실험을 수행하여 마찰력 모델의 신뢰성을 검증하고, 마찰력 모델로부터 마찰 성분의 영향력을 분석한다.

6 단 압연기의 극박 압연공정에서 3 차원 판 형상 예측 (Prediction of Three-Dimensional Strip Profile for 6-High Mill in Thin-Strip Rolling)

  • 이상호;송길호;이성진;김병민
    • 대한기계학회논문집A
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    • 제35권8호
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    • pp.855-861
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    • 2011
  • 본 연구에서는 극박 압연 이론과 6 단 압연기 수식 모델을 이용하여 압연 후 판 형상 예측에 대하여 제안하였다. 폭 방향에서 롤 사이의 접촉 압력과 판과 워크롤 사이의 압연하중은 6 단 압연기의 형상학적 구조와 경계조건을 이용한 수식모델을 통하여 계산된다. 그리고 압연 방향의 압연하중 분포는 Fleck 의 극박 압연 이론을 이용하여 계산하였다. 워크롤의 3 차원 탄성 변형량은 폭 과 압연방향의 압력분포에 의하여 계산된다. 이때, 3 차원 판 형상은 워크롤의 탄성변형에 의하여 얻어진다. 또한 3 차원 판 형상은 극박 압연 실험과 유한요소해석을 통하여 검증하였다.

다수의 각접촉 볼베어링으로 지지된 5자유도 회전계에서 볼베어링의 Waviness에 의해 발생하는 비선형진동 해석모델 (Nonlinear Vibration Model of Ball Bearing Waviness in a Rigid Rotor Supported by Multi-Row Ball Bearing Considering Five Degrees of Freedom)

  • 정성원;장건희
    • 소음진동
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    • 제11권2호
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    • pp.336-345
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    • 2001
  • This research presents a nonlinear model to analyze the ball bearing nitration due to the waviness in a rigid rotor supported by multi-row ball bearings. The waviness of a ball and each races is modeled by the superposition of sinusoidal function, and the position vectors of inner and outer groove radius center are defined with respect to the mass center of the rotor in order to consider five degrees of freedom of a general rotor-bearing system. The waviness of a ball bearing is introduced to these position vectors to use the Hertzian contact theory in order to calculate the elastic deflection and nonlinear contact force resulting from the waviness while the rotor has translational and angular motion. They can be determined by solving the nonlinear equations of motion with five degrees of freedom by using the Runge-Kutta-Fehlberg algorithm. Numerical results of this research are validated with those of prior researchers. The proposed model can calculate the translational displacement as well as the angular displacement of the rotor supported by the multi-row ball bearings with waviness. It also characterizes the nitration frequencies resulting from the various kinds of waviness in rolling elements, the harmonic frequencies resulting from the nonlinear load-deflection characteristics of ball bearing. and the sideband frequencies resulting from the waviness interaction.

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센서 동역학을 고려한 충격응답해석 (Analysis of Impact Responses Considering Sensor Dynamics)

  • 류봉조;권병희;안길영;오일성;이규섭
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2002년도 추계학술대회논문집
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    • pp.731-736
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    • 2002
  • Impact is the most common type of dynamic loading conditions that give rise to impulsive forces and affects the vibrational characteristics of mechanical systems . Since the real impact force and acceleration at the contact surface are measured indirectly through the sensors, the measured outputs can be a little different from the real impact responses. In this study, the contact force model based on the Hertz law is proposed in order to predict the impact force correctly. To investigate the influence of the position of the sensor attached to the impacting bodies, the two kinds of sensors were used. Finally, the contact force model obtained by drop test was applied to predict the impact force between the moving part and the stopper in magnetic contactor.

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센서 동역학을 고려한 충돌체간의 충격응답 (Impact Responses of Two Colliding Bodies Considering Sensor Dynamics)

  • 류봉조;안길영;권병희;송오섭;이종원
    • 한국소음진동공학회논문집
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    • 제14권5호
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    • pp.394-401
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    • 2004
  • This paper presents a study on the analysis of impact responses taking into account sensor dynamics. The contact force between impacting bodies is modelled by using Hertz force-displacement law and linear damping function. Since the real impact force and acceleration at the contact surface of two colliding bodies are measured indirectly by the sensors, the measured outputs can be a little different from the real impact responses. Therefore, in this study, the importance of consideration of sensor dynamics in the impact problems of two colliding bodies is emphasized. In order to verify the appropriateness of the proposed contact force model, the drop type impact test using two kinds of sensors is carried out. Through the numerical analysis and experiment, the effect of sensor dynamics and characteristics on the contact force model is investigated.

응력 구배 효과를 고려한 구름 접촉 모델의 피로수명해석 (Fatigue Life Analysis of Rolling Contact Model Considering Stress Gradient Effect)

  • 조인제;유용훈;이보라;조용주
    • Tribology and Lubricants
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    • 제31권6호
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    • pp.272-280
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    • 2015
  • Recently, Luu suggested fatigue life equation that uses every term of the Crossland equation with stress gradient effect. Luu’s model, however, has a limit of being unable to coverage small radii that are less than a specified length. Furthermore, rolling model has a very small contact area compared to the rolling element size, and fatigue failure occurs on the small radius such as surface asperity by cyclic loading. Therefore, it is necessary to modify fatigue life equation in order to enable fatigue analysis for a small radius. In this paper, the fatigue life considering a stress gradient effect in rolling contact was obtained using Luu’s modified equation. Fatigue analysis was performed to study the effect of stress gradient on the fatigue life using newly adopted equation and to compare the results with pervious models. In order to do this, a series of simulation such as surface stress analysis, subsurface stress analysis, and fatigue analysis are conducted for two rolling balls of same size that contact each other. Through such a series of processes, the fatigue life can be calculated and equation that is proposed in this paper evaluates the fatigue life in case the contact area is small.

풍력발전기용 볼 베어링의 단순화 볼 모델을 이용한 해석기법 연구 (A Study on a Finite Element Analysis Method Using Simplified Ball Models of Wind Turbine Ball Bearings)

  • 김승우;송정우;홍준표;강종훈
    • 풍력에너지저널
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    • 제14권4호
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    • pp.21-28
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    • 2023
  • This study focuses on the analysis of slewing ball bearings in wind turbines. Slewing bearings have an outer diameter of several meters, and hundreds of balls are in contact with the raceway. Due to the large number of balls and raceway contact conditions, it is difficult to accurately analyze contact stresses using general analysis techniques. To analyze the contact stress of a slewing ball bearing, the sub-modeling method is applied, which is a technique that first analyzes the displacement of the entire model and then analyzes the local stress at the point of maximum displacement. In order to reduce the displacement analysis time of the entire ball bearing, the technique of replacing the ball with a nonlinear spring is adopted. The analytical agreement of the simplified model was evaluated by comparing it with a solid mesh model of the ball for three models with different spring attachment methods. It was found that for the condition where a large turnover moment is applied to the bearing, increasing the number of spring elements gives the closest results to modeling the ball with a solid mesh.