• Title/Summary/Keyword: Radial Contact Force

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Rotordynamic Analysis of Automotive Turbochargers Supported on Ball Bearings and Squeeze Film Dampers in Series: Effect of Squeeze Film Damper Design Parameters and Rotor Imbalances (볼 베어링과 스퀴즈 필름 댐퍼로 지지되는 차량용 터보차저의 회전체동역학 해석: 스퀴즈 필름 댐퍼 설계 인자와 회전체 불균형 질량의 영향)

  • Kim, Kyuman;Ryu, Keun
    • Tribology and Lubricants
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    • v.34 no.1
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    • pp.9-15
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    • 2018
  • Modern high-performance automotive turbochargers (TCs) implement ceramic hybrid angular contact ball bearings in series with squeeze film dampers (SFDs) to enhance transient responses, thereby reducing the overall emission levels. The current study predicts the rotordynamic responses of the commercial automotive TCs (compressor wheel diameter = ~53 mm, turbine wheel diameter = ~43 mm, and shaft diameter at the bearing locations = ~7 mm) supported on ball bearings and SFDs for various design parameters of SFDs, including radial clearance, axial length, lubricant viscosity, and rotor imbalance conditions (i.e., amplitudes and phase angles) while increasing rotor speed up to 150 krpm. This study validates the predictive rotor finite element model against measurements of mass, polar and transverse moments of inertia, and free-free mode natural frequencies and mode shapes. A nonlinear rotordynamic model integrates nonlinear force coefficients of SFDs to calculate the transient responses of the TC rotor-bearing system. The predicted results show that SFD radial clearances, as well as phase angles of rotor imbalances, have the paramount effect on the dynamic responses of TC shaft motions.

The Influence of Assembling Errors on the Performance of the Rotor Supported by Active Magnetic Bearings (조립오차가 능동 자기베어링으로 지지된 축의 성능에 미치는 영향)

  • Kim, Dae-Gon;Kim, Kyung-Woong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.20 no.12
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    • pp.3909-3916
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    • 1996
  • Magnetic bearing is the machine element that supports the shaft without mechanical contact using the magnetic force induced by permanent magnet of electromagnet. Active magnetic bearing system is composed of sensor, controller, power amplifier, and electromagnet. If all the elements were dieal, shaft position could be controlled to sensor resolution, Because each elements inreal system have mechanical and electricla losses and nonlinearity, it is impossible to attain the desired performance using general control algorithm. So far it has been studied on improvement of the control algorithm of the electric characteristics of each elements. Another factors to affect shaft behavior are the manufacturing errors due to machine work, and assembling errors due to accumulate manufacturing errors of the radial magnetic bearing. This paper describes that the shaft behavior due to accumulate manufacturing errors and asymmetric bolting. This paper describes that the shaft behavior due to assembling errors of the radial bearings donot affect the rotaitonal accuracy of the shaft. But when the amplitude of the assembling errors increasees over the certain value, the bearing can not support the shaft properly.

The effect of composite-elastomer isolation system on the seismic response of liquid-storage tanks: Part I

  • Shahrjerdi, A.;Bayat, M.
    • Earthquakes and Structures
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    • v.15 no.5
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    • pp.513-528
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    • 2018
  • A typical viable technique to decrease the seismic response of liquid storage tanks is to isolate them at the base. Base-isolation systems are an efficient and feasible solution to reduce the vulnerability of structures in high seismic risk zones. Nevertheless, when liquid storage tanks are under long-period shaking, the base-isolation systems could have different impacts. These kinds of earthquakes can damage the tanks readily. Hence, the seismic behaviour and vibration of cylindrical liquid storage tanks, subjected to earthquakes, is of paramount importance, and it is investigated in this paper. The Finite Element Method is used to evaluate seismic response in addition to the reduction of excessive liquid sloshing in the tank when subjected to the long-period ground motion. The non-linear stress-strain behaviour pertaining to polymers and rubbers is implemented while non-linear contact elements are employed to describe the 3-D surface-to-surface contact. Therefore, Nonlinear Procedures are used to investigate the fluid-structure interactions (FSI) between liquid and the tank wall while there is incompressible liquid. Part I, examines the effect of the flexibility of the isolation system and the tank aspect ratio (height to radius) on the tank wall radial displacements of the tank wall and the liquid sloshing heights. Maximum stress and base shear force for various aspect ratios and different base-isolators, which are subjected to three seismic conditions, will be discussed in Part II. It is shown that the composite-base isolator is much more effective than other isolators due to its high flexibility and strength combined. Moreover, the base isolators may decrease the maximum level pertaining to radial displacement.

Vehicle Vibration Study by Tire Flat Spot (타이어 플랫 스팟에 의한 차량진동 연구)

  • Park, Ju-Pyo;Choi, Jung-Hyun;Lee, Sang-Ju
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2007.11a
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    • pp.1395-1400
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    • 2007
  • Tire flat spot is a deformation which occurs around the contact patch during long-period parking and does hardly recovered even after driving. The deformation makes a tire self-excited and ride comfort gets worse. In this study, it is shown that the flat spot can be evaluated by measuring change in radial run out or force. Its effects on vibration at vehicle floor and steering wheel are also revealed. Finally it is shown that the flat spot is likely to occur if the inflation pressure is low and the tire is suppressed by a heavy load at a high temperature.

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Life Analysis of Ball Bearings by Accelerated Life Test (가속수명시험을 이용한 볼 베어링 수명분석)

  • 김형의;이윤표;유영철
    • Proceedings of the Korean Reliability Society Conference
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    • 2004.07a
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    • pp.335-342
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    • 2004
  • The failures such as flaking, wear, crack and seizing caused by the high contact pressure accompanied with sliding motion between inner or outer ring and ball are potential failures of ball bearing. In this research, we have qualitatively selected the efficient test items through the analysis of the life and potential failures of ball bearing. The bearing's failures are related closely to the whole system in using the bearing. So, the bearing itself requires an estimation of life in order to opreate the system safely. We have tested ten ball bearings. Our research has applied both radial and axial direction force of maximum torque conditions simultaneously for the accelerated life testing. The result is established by employing the weibull plot and compared the predicted life of ball bearing to the experimental result.

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The Lubrication Characteristics of the Vane Tip Under Pressure Boundary Condition of Oil Hydraulic Vane Pump

  • Cho Ihn-Sung;Oh Seok-Hyung;Song Kyu-Keun;Jung Jae-Youn
    • Journal of Mechanical Science and Technology
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    • v.20 no.10
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    • pp.1716-1721
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    • 2006
  • The Lubrication Mode of line contacts between the vane and the camring in an oil hydraulic vane pump has been investigated. First, the variations of the radial force of a vane were calculated from previous measurements of dynamic internal pressure in four chambers surrounding a vane. Next, the lubrication modes were distinguished with Hooke's chart, which is an improvement over Johnson's chart. Finally, the influence of the boundary conditions in the lubrication region on the fluid film lubrication was examined by calculating the film pressure distributions. The results showed that the lubrication mode of the vane tip exists in the rigid-variable-viscosity region, and that discharge pressure higher than 7 MPa greatly affects the oil film pressure in the small and the large arc section because of the Piezo-viscous effect.

A Study on Slow Rolling tire for Prediction of the Tire Forces and Moments (회전하는 타이어의 접지면 동특성 예측에 관한 연구)

  • 김항우;황갑운;조규종
    • Computational Structural Engineering
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    • v.10 no.2
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    • pp.161-169
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    • 1997
  • It is known that tire plays an important role to the dynamic performances of a vehicle such as noise, vibration, ride and handling. Therefore, force and moment measurements have been a part of the traditional tire engineering process. In this paper, a computational analysis technique has been explored. A FE model is made to simulate inflation, vertical load due to the vehicle weight, and the slow rolling of a radial tire. A rigid surface with Coulomb friction is included in the model to simulate the slow rolling contact. The tire slip during the in-plane motion of the rigid surface is calculated. Results are presented for both lateral and vertical loads, as well as straight ahead free rolling. The calculated and measured tire slips are in good correlation. A Study on slow Rolling Tire for perdiction of tire Forces and Moments.

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Damage mechanism of particle impact in a ${Al_2}}O_3}-TiO_2$plasma coated soda-lime glass (${Al_2}}O_3}-TiO_2$ 플라즈마 코팅된 유리의 입자충격에 의한 손상기구)

  • Suh, Chang-Min;Lee, Moon-Hwan;Hong, Dea-Yeong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.22 no.3
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    • pp.529-539
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    • 1998
  • A quantitative study of impact damage of ${Al_2}}O_3}-TiO_2$ plasma coated soda-lime glasses was carried out and compared with that of the uncoated smooth glass specimen. The shape of cracks by the impact of steel ball was observed by stereo-microscope and the decrease of the bending strength due to the impact of steel ball was measured through the 4-point bending test. At the low velocity, cone cracks were occurred. As the impact velocity increases, initial lateral cracks were propagated on the slanting surface of a cone crack, and radial cracks were generated at the crushed site. When the impact velocity of steel ball exceeds the critical velocity, the contact site of specimen was crushed due to plastic deformation and then radial and lateral cracks were largely grown. Crack length of coated specimens was smaller than that of uncoated smooth specimen due to the effect of coating layer on the substrate surface. According to impact velocity, the bending strength of coated specimens had no significant difference, compared with that of the uncoated smooth specimen. But this represents that the bending strength of coated specimens was increased, considering the effect of sand blasting damage which was performed to increase the adhesion force of coating layer.

A Study on the tire structure-borne sound (타이어 구조 진동음에 관한 연구)

  • Chi, Chang-Heon
    • The Journal of the Acoustical Society of Korea
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    • v.14 no.2
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    • pp.80-91
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    • 1995
  • A theoretical models has been prepared which describes the noise generated by tire/road interaction for the tire structure-borne sound analysis. The model begin with a set of thin shell equations describing the motion of the belt of a radial ply tire, as drived by Bohm('mechanisms of the belted tire', Igeniur-Archiv, XXXV, 1966). Structural quantities required for these equations are derived from material properties of the tire. The rolling shape of a tire is computed from the steady-state limit of these equations. Vibrational response of the tire is treated by the full dependent shell equations. The force input at the tire/road interface is calculated on the basis of tread geometry and distribution of contact patch pressure. Radiation of noise is calculated by a simpson integral. Using the programs, the effect on noise of various tire design variations is computed and discussed. Trends which lead to quiet tire design are identified.

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Dynamic Analysis of Spindle Supported by Multiple Bearings of Different Types (복합베어링으로 지지된 스핀들의 동적 해석)

  • Tong, Van-Canh;Bae, Gyu-Hyun;Hong, Seong-Wook
    • Journal of the Korean Society for Precision Engineering
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    • v.32 no.2
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    • pp.117-125
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    • 2015
  • This paper presents a dynamic modeling method for the indeterminate spindle-bearing system supported by multiple bearings of different types. A spindle-bearing system supported by ball and cylindrical roller bearings is considered. The de Mul's bearing model is extended for calculating ball and cylindrical roller bearing stiffness matrices with inclusion of centrifugal force and gyroscopic moment. The dependence between spindle shaft reaction forces and bearing stiffness is effectively resolved using an iterative approach. The spindle rotor dynamics is established with the Timoshenko beam theory based finite elements. The spindle reaction forces, bearings stiffness and spindle natural frequencies are obtained with taking into account spindle radial load, ball bearing axial preload and rotational speed effects. The developed method is verified by comparing the simulation results with those from a commercial program.