Thermal Conductance Measurement Techniques for High-Speed Bearings in Vacuum

2005 ◽  
Author(s):  
Steven M. Demsky ◽  
Yoshimi R. Takeuchi ◽  
James T. Dickey
Keyword(s):  
Experimental Method ◽  
Rotational Speed ◽  
Axial Load ◽  
High Speed ◽  
Thermal Environment ◽  
Measurement Techniques ◽  
Thermal Conductance ◽  
Conductance Measurement ◽  
Aerospace Corporation ◽  
Inner Race

An experimental method has been developed at The Aerospace Corporation to determine the thermal conductance of moving bearings in vacuum. The test involves the measurement of thermal conductance of a single bearing under controlled inner race rotational speed, axial load, and thermal environment. Applications of interest include high-speed momentum wheels and flywheels. This paper covers the experimental method developed for this purpose and the techniques used to establish measurement uncertainty.

Heat Transfer Across Ball Bearings in Vacuum

2005 ◽  
Author(s):  
Yoshimi R. Takeuchi ◽  
James T. Dickey ◽  
Steven M. Demsky ◽  
Matthew A. Eby
Keyword(s):  
Heat Transfer ◽  
Axial Load ◽  
High Speed ◽  
Thermal Conductance ◽  
Thermal Conditions ◽  
Test Results ◽  
Angular Contact Ball Bearing ◽  
Conductance Data ◽  
The Subject ◽  
Aerospace Corporation

Accurate spacecraft bearing temperature predictions often require both system and bearing level heat source and thermal conductance information. Bearing thermal conductance data is usually the most significant unknown in the development of the thermal model and little has been published in open literature on the subject. Consequently experiments have been conducted at The Aerospace Corporation to address this topic, with special attention given to applications such as high-speed momentum and flywheels. An experiment was designed to measure thermal conductance across a single bearing under both static and dynamic states. This paper will describe the test results for an angular-contact ball bearing under controlled inner race rotational speed, axial load, and thermal conditions. Tests were conducted on both dry and Nye Pennzane SHF2001 synthetic oil lubricated bearings. Test data showed that thermal conductance is sensitive to a complex interdependent set of variables including maximum run-in speed, axial load and temperature. A basic physical understanding of the heat transfer mechanism across a bearing was developed based on experimental results.

scholarly journals A new model for predicting the mechanical efficiency of ball screws based on the empirical equations for the friction torque of rolling bearings

2018 ◽  
Vol 10 (9) ◽  
pp. 168781401880017 ◽  
Author(s):  
Chang-Guang Zhou ◽  
Hu-Tian Feng ◽  
Yi Ou
Keyword(s):  
Rotational Speed ◽  
Axial Load ◽  
High Speed ◽  
Mechanical Efficiency ◽  
Friction Torque ◽  
Numerical Control ◽  
Measuring System ◽  
Empirical Equations ◽  
Rolling Bearings ◽  
New Model

Based on the empirical equations for the friction torque of rolling bearings, this article proposes a new model for predicting the friction torque and mechanical efficiency of ball screws. Meanwhile, a novel measuring system is constructed to obtain the mechanical efficiency of ball screws, where both the axial load and rotational speed are stable and adjustable. The experimental results at a rotational speed of 1000 r/min agree well with the theoretical values calculated by the present method, which show that the mechanical efficiency of ball screws increases with increasing axial load. Moreover, the model built in this article is more applicable to a relatively high-speed condition. The new model can be easily used to obtain the friction torque and mechanical efficiency for ball screws, which is essential for improving the performance of ball screws and the computer numerical control machine tools.

Influence of rotational speed on the impact characteristics caused by a localized defect of the outer raceway in a ball bearing under an axial load

2020 ◽  
Vol 234 (3) ◽  
pp. 498-513
Author(s):  
Pingping Hou ◽  
Liqin Wang ◽  
Qiuyang Peng
Keyword(s):  
Frequency Band ◽  
Rotational Speed ◽  
Axial Load ◽  
High Speed ◽  
Ball Bearing ◽  
Structural Vibration ◽  
Optimal Frequency ◽  
Nonlinear Dynamic Model ◽  
Impact Characteristics ◽  
The Impact

The rotational speed is a crucial parameter for bearing condition monitor. The present study shows the influence of the rotational speed on the impact characteristics caused by a localized defect of the outer raceway. A 2 Nb + 5-degrees-of-freedom nonlinear dynamic model for a ball bearing is developed. The waviness of bearing components, a localized defect of the outer raceway, and the centrifugal forces of balls caused by rotational speed are involved in the ball bearing model. Spectral kurtosis (SK) analysis and envelope spectrum analysis are used to extract the impact signal and confirm the position of the optimal frequency band affected by the impact signal. The peak of the impact signal rises with the increase in rotational speed. The position of the optimal frequency band affected by the impact signal is a linear piecewise function of the rotational speed. These simulated results are verified through vibration experiments of a ball bearing with a localized defect of the outer raceway under an axial load. In addition, considering both a localized defect on the outer raceway and the waviness of bearing components, only when the size of the localized defect is large enough, can the impact signal overcome the influence of the structural vibration of the system to extract impact characteristics. The case studies of high-speed spindle bearing state diagnosis show that high speed is not conducive to the extraction of the impact characteristics.

scholarly journals Operating temperatures of oil-lubricated medium-speed gears: Numerical models and experimental results

2003 ◽  
Vol 217 (2) ◽  
pp. 87-106 ◽  
Author(s):  
H Long ◽  
A A Lord ◽  
D T Gethin ◽  
B J Roylance
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Surface Temperature ◽  
Rotational Speed ◽  
High Speed ◽  
Applied Load ◽  
Frictional Heat ◽  
Transfer Coefficients ◽  
Gear Teeth ◽  
Heat Transfer Coefficients

This paper investigates the effects of gear geometry, rotational speed and applied load, as well as lubrication conditions on surface temperature of high-speed gear teeth. The analytical approach and procedure for estimating frictional heat flux and heat transfer coefficients of gear teeth in high-speed operational conditions was developed and accounts for the effect of oil mist as a cooling medium. Numerical simulations of tooth temperature based on finite element analysis were established to investigate temperature distributions and variations over a range of applied load and rotational speed, which compared well with experimental measurements. A sensitivity analysis of surface temperature to gear configuration, frictional heat flux, heat transfer coefficients, and oil and ambient temperatures was conducted and the major parameters influencing surface temperature were evaluated.

Wind-Induced Vibration Analysis and Remote Monitoring Test of Wind Turbine Power Tower

2013 ◽  
Vol 639-640 ◽  
pp. 293-296 ◽  
Author(s):  
Ai Jun Chen ◽  
Guo Jing He
Keyword(s):  
Wind Power ◽  
Electromagnetic Interference ◽  
High Speed ◽  
Measurement Techniques ◽  
Dynamic Monitoring ◽  
Leading Role ◽  
Tower Structure ◽  
Monitoring Test ◽  
Major Loss ◽  
Wind Induced Vibration

The major loss of the hurricane was damage and collapse of structures, In particular, wind power tower wich requires both the use of wind, wind on the structure plays a leading role in the tall slender flexible structure.In this paper, tests of remote sensing dynamic monitoring of tower structure with wind power are carried out, using measurement techniques of high-frequency and high-speed electromagnetic interference.

Analysis of the Lubrication Regimes at the Small End and Big End of a Connecting Rod of a High Performance Motorbike Engine

2012 ◽  
Author(s):  
Luca Bertocchi ◽  
Matteo Giacopini ◽  
Daniele Dini
Keyword(s):  
Rotational Speed ◽  
High Speed ◽  
High Performance ◽  
Hydrodynamic Lubrication ◽  
Vertical Axis ◽  
Connecting Rod ◽  
Lubrication Regimes ◽  
High Speed Rotation ◽  
Speed Rotation ◽  
Squeeze Effect

In the present paper, the algorithm proposed by Giacopini et. al. [1], based on a mass-conserving formulation of the Reynolds equation using the concept of complementarity is suitably extended to include the effects of compressibility, piezoviscosity and shear-thinning on the lubricant properties. This improved algorithm is employed to analyse the performance of the lubricated small end and big end bearings of a connecting rod of a high performance motorbike engine. The application of the algorithm proposed to both the small end and the big end of a con-rod is challenging because of the different causes that sustain the hydrodynamic lubrication in the two cases. In the con-rod big end, the fluid film is mainly generated by the relative high speed rotation between the rod and the crankshaft. The relative speed between the two races forms a wedge of fluid that assures appropriate lubrication and avoids undesired direct contacts. On the contrary, at the con-rod small end the relative rotational speed is low and a complete rotation between the mating surfaces does not occurs since the con-rod only oscillates around its vertical axis. Thus, at every revolution of the crankshaft, there are two different moments in which the relative rotational speed between the con-rod and the piston pin is null. Therefore, the dominant effect in the lubrication is the squeeze caused by the high loads transmitted through the piston pin. In particular both combustion forces and inertial forces contribute to the squeeze effect. This work shows how the formulation developed by the authors is capable of predicting the performance of journal bearings in the unsteady regime, where cavitation and reformation occur several times. Moreover, the effects of the pressure and the shear rate on the density and on the viscosity of the lubricant are taken into account.

The Study of Thermal Raising and Transmission Torque of High Speed Ball-Screw Lubricated by Different Greases

2015 ◽  
Vol 642 ◽  
pp. 212-216
Author(s):  
Yi Haung ◽  
Chin Chung Wei
Keyword(s):  
Contact Area ◽  
Axial Load ◽  
High Speed ◽  
Performance Test ◽  
Vertical Motion ◽  
High Viscosity ◽  
Ball Screw ◽  
Frictional Heat ◽  
Motion Platform ◽  
Base Oil

Ball screw is a high-precision and high performance linear drive of mechanical elements. The frictional heat of internal components what is very significant impact for platform transmission in high speed and the high axial load and causes the thermal expansion of element. In this research , the influence of different greases on ball screw is investigated in thermal rising of nut and driving torque in high speed and high axial load. A vertical motion platform was used for driving performance test. Thermal rising of nut of ball screw and the variance of transmission torque whose lubricated by high viscosity base oil grease is significant larger than the lower one. High viscosity grease is not easy to carry out the friction heat generated at ball and raceway contact area due to the bad flowing properties. It also has more serious wear occurred at contact area and high friction force, whose causes the large variance of transmission torque.

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