Lubrication mechanisms of rubbing interface in internal meshing teeth with small clearance

2020 ◽  
Vol 32 (4) ◽  
pp. 169-182
Author(s):  
Si Ren ◽  
Ying Zhang ◽  
Jialong Yang ◽  
Zongzheng Wang ◽  
Ling Dai ◽  
...  
Keyword(s):  
Small Clearance ◽  
Internal Meshing ◽  
Lubrication Mechanisms

A New Design of Cycloidal Planetary Reducer With Internal Cycloidal Profile

2018 ◽  
Author(s):  
He Mao ◽  
Guanyi Liu ◽  
Deqiang Zeng ◽  
Yaning Cao ◽  
Kai He ◽  
...  
Keyword(s):  
Mechanical Efficiency ◽  
Industrial Applications ◽  
Transmission Characteristics ◽  
Torque Transmission ◽  
Contact Frequency ◽  
Small Clearance ◽  
Rv Reducer ◽  
New Type ◽  
Integral Structure ◽  
Internal Meshing

Compared with other speed reducers, the two-stage cycloidal planetary one also known as RV reducer has higher precision, higher mechanical efficiency, higher loading capacity as well as long service life. These characteristics make it attractive for industrial applications, especially for robotics applications and machine tools, where high precision and large torque transmission are required. The traditional RV reducer uses cycloidal drive which is comprised of the cycloidal wheel and the pins. It has some disadvantages in the pin design, because of small clearance between the pin and the cycloidal wheel, the collision between the pin and the cycloidal wheel may lead to unstable stress in the key parts and output velocity fluctuation. This paper presents an innovative cycloidal planetary reducer using internal meshing principle instead of external meshing between cycloidal wheel and pins in traditional RV reducer. In the new design of the reducer, the internal teeth with cycloidal profile are processed inside the reducer housing, meshing with two pin holders which are placed at the inner side of the cycloidal teeth to achieve transmission. The pin holder is a new integral structure of pins integrated on a round plate. Then a comparison study is conducted through establishment of system dynamics analysis. The transmission characteristics and meshing force of both the new type of reducer and the traditional RV reducer are analyzed under the same condition of reduction ratio. The results show the new reducer improves on these shortcomings, its transmission performance is competitive as compared to traditional RV reducer. What’s even better is that its output speed is more stable, and the contact force between the pin position on the pin holder and the internal cycloidal teeth inside the reducer housing is smaller, as well as the contact frequency is obviously decreased.

scholarly journals Towards the understanding of lubrication mechanisms in total knee replacements – Part I: Experimental investigations

2021 ◽  
Vol 156 ◽  
pp. 106874 ◽  
Author(s):  
David Nečas ◽  
Martin Vrbka ◽  
Max Marian ◽  
Benedict Rothammer ◽  
Stephan Tremmel ◽  
...  
Keyword(s):  
Experimental Investigations ◽  
Total Knee Replacements ◽  
Knee Replacements ◽  
Total Knee ◽  
Lubrication Mechanisms

scholarly journals Experimental and Numerical Investigation about Small Clearance Journal Bearings under Static Load Conditions

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Carlo Alberto Niccolini Marmont Du Haut Champ ◽  
Fabrizio Stefani ◽  
Paolo Silvestri
Keyword(s):  
Three Dimensional ◽  
Journal Bearings ◽  
Radial Clearance ◽  
Small Scale ◽  
Test Rig ◽  
Small Clearance ◽  
Dimensional Simulation ◽  
Dynamic Loading Conditions ◽  
Static And Dynamic Loading ◽  
Good Agreement

The aim of the present research is to characterize both experimentally and numerically journal bearings with low radial clearances for rotors in small-scale applications (e.g., microgas turbines); their diameter is in the order of ten millimetres, leading to very small dimensional clearances when the typical relative ones (order of 1/1000) are employed; investigating this particular class of journal bearings under static and dynamic loading conditions represents something unexplored. To this goal, a suitable test rig was designed and the performance of its bearings was investigated under steady load. For the sake of comparison, numerical simulations of the lubrication were also performed by means of a simplified model. The original test rig adopted is a commercial rotor kit (RK), but substantial modifications were carried out in order to allow significant measurements. Indeed, the relative radial clearance of RK4 RK bearings is about 2/100, while it is around 1/1000 in industrial bearings. Therefore, the same original RK bearings are employed in this new test rig, but a new shaft was designed to reduce their original clearance. The new custom shaft allows to study bearing behaviour for different clearances, since it is equipped with interchangeable journals. Experimental data obtained by this test rig are then compared with further results of more sophisticated simulations. They were carried out by means of an in-house developed finite element (FEM) code, suitable for thermoelasto-hydrodynamic (TEHD) analysis of journal bearings both in static and dynamic conditions. In this paper, bearing static performances are studied to assess the reliability of the experimental journal location predictions by comparing them with the ones coming from already validated numerical codes. Such comparisons are presented both for large and small clearance bearings of original and modified RKs, respectively. Good agreement is found only for the modified RK equipped with small clearance bearings (relative radial clearance 8/1000), as expected. In comparison with two-dimensional lubrication analysis, three-dimensional simulation improves prediction of journal location and correlation with experimental results.

Exploring the Lubrication Mechanisms of Synovial Fluids for Joint Longevity – A Perspective

2021 ◽  
pp. 111926
Author(s):  
Max Marian ◽  
Raj Shah ◽  
Blerim Gashi ◽  
Stanley Zhang ◽  
Kiran Bhavnani ◽  
...  
Keyword(s):  
Synovial Fluids ◽  
Lubrication Mechanisms

Three-Dimensional Flows and Loss Reduction in Axial Compressors

1987 ◽  
Vol 109 (3) ◽  
pp. 354-361 ◽  
Author(s):  
Y. Dong ◽  
S. J. Gallimore ◽  
H. P. Hodson
Keyword(s):  
Three Dimensional ◽  
Axial Compressor ◽  
Axial Flow ◽  
Tracer Gas ◽  
Suction Surface ◽  
Axial Compressors ◽  
Small Clearance ◽  
Oil Flow ◽  
Stator Blade ◽  
Flow Compressor

Measurements have been performed in a low-speed high-reaction single-stage axial compressor. Data obtained within and downstream of the rotor, when correlated with the results of other investigations, provide a link between the existence of suction surface–hub corner separations, their associated loss mechanisms, and blade loading. Within the stator, it has been shown that introducing a small clearance between the stator blade and the stationary hub increases the efficiency of the stator compared to the case with no clearance. Oil flow visualizaton indicated that the leakage reduced the extensive suction surface–hub corner separation that would otherwise exist. A tracer gas experiment showed that the large radial shifts of the surface streamlines indicated by the oil flow technique were only present close to the blade. The investigation demonstrates the possible advantages of including hub clearance in axial flow compressor stator blade rows.

New Rotor with Variable Clearance in the Short Fiber Rubber Composite Mixing

2013 ◽  
Vol 328 ◽  
pp. 387-392
Author(s):  
Cai Jun Liu ◽  
Chuan Sheng Wang
Keyword(s):  
Production Efficiency ◽  
Short Fiber ◽  
Short Fibers ◽  
Mixing Chamber ◽  
Small Clearance ◽  
Rubber Composite ◽  
Mixing Quality ◽  
And Performance

The mixing mechanism of short fiber/rubber composite was analyzed. The clearance between the rotor edge peak and mixing chamber influenced mixing, dispersion and length of the short fibers in compound. The new rotor was designed with variable clearance. The large clearance gap improve the mixing, and the small clearance gap helped to improve the dispersion of short fiber. The mixing quality and performance of short fiber/rubber composite were improved by using the new rotor, and the production efficiency increased.

Packaging of In-Plane Thermal Microactuators for BioMEMS Applications

2005 ◽  
Author(s):  
Hrishikesh V. Panchawagh ◽  
Faheem F. Faheem ◽  
Cari F. Herrmann ◽  
David B. Serrell ◽  
Dudley S. Finch ◽  
...  
Keyword(s):  
Flip Chip ◽  
Atomic Layer ◽  
Thermal Actuator ◽  
Mems Devices ◽  
Thermal Actuators ◽  
Layer Deposition ◽  
Comb Drives ◽  
Small Clearance ◽  
Surrounding Liquid ◽  
Packaging Technique

This paper addresses two issues related to in-plane, electro-thermal actuators for BioMEMS applications. First, in order to protect the actuator from biological debris and particulates, a packaging technique using a flip-chip bonded polysilicon cap is demonstrated. The encapsulated actuator transmits motion outside the package via a piston, which moves through a small clearance. The second issue addressed is the reduction in efficiency of the thermal actuator in liquids. By coating the packaged actuator with a thin conformal hydrophobic layer via an atomic layer deposition (ALD) process, the liquid is prevented from entering the encapsulation. This avoids direct contact between the actuator and the surrounding liquid thereby improving its efficiency. The unpackaged and packaged actuators were tested in both air and de-ionized water. Although the packaging resulted in a reduction in the performance of the thermal actuator in air, the actuation efficiency in water was significantly improved due to the isolation of the hot arms from the liquid. This packaging technique is also applicable to other MEMS devices and in-plane actuators such as electrostatic comb drives for engineering as well as biological applications.

CFD Leakage Predictions of Unworn and Worn Labyrinth Seals With and Without Tooth Axial Offset

2017 ◽  
Author(s):  
Hasham H. Chougule ◽  
Alexander Mirzamoghadam
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Numerical Modeling ◽  
Steady State ◽  
Flow Field ◽  
Labyrinth Seals ◽  
Small Clearance ◽  
Total Leakage ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Deflection

The objective of this study is to develop a Computational Fluid Dynamics (CFD) based methodology for analyzing and predicting leakage of worn or rub-intended labyrinth seals during operation. The simulations include intended tooth axial offset and numerical modeling of the flow field. The purpose is to predict total leakage through the seal when an axial tooth offset is provided after the intended/unintended rub. Results indicate that as expected, the leakage for the in-line worn land case (i.e. tooth under rub) is higher compared to unworn. Furthermore, the intended rotor/teeth forward axial offset/shift with respect to the rubbed land reduces the seal leakage. The overall leakage of a rubbed seal with axial tooth offset is observed to be considerably reduced, and it can become even less than a small clearance seal designed not to rub. The reduced leakage during steady state is due to a targeted smaller running gap because of tooth offset under the intended/worn land groove shape, higher blockages, higher turbulence and flow deflection as compared to worn seal model without axial tooth offset.

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