A gear rattle model accounting for oil squeeze between the meshing gear teeth

2005 ◽  
Vol 219 (9) ◽  
pp. 1075-1083 ◽  
Author(s):  
R Brancati ◽  
E Rocca ◽  
R Russo
Keyword(s):  
High Frequency ◽  
Oil Viscosity ◽  
Damping Force ◽  
Oil Film ◽  
One Dimensional ◽  
Gear Teeth ◽  
High Frequency Vibrations ◽  
The Impact ◽  
Gear Rattle ◽  
Lubrication Conditions

In this paper a non-linear one-degree-of-freedom model for analysis of gear rattle vibrations in automotive manual transmissions is presented. In order to take into account the damping effects owing to the oil in the gap between two teeth of a meshing gear, a simple one-dimensional model for the oil-film squeeze effects is proposed. The squeeze model assumes that the damping force is proportional to the oil viscosity and to the extension of the oil film in the plane of curvature of the teeth, which may depend on the lubrication conditions (dry sump, splash, bath). The results provided from several numerical simulations, carried out with reference to helical involute tooth pairs, confirm the capability of oil in reducing the high-frequency vibrations subsequent to the impact between the teeth. In particular, the influence exerted by oil viscosity and gap extension on the rattle characteristics is investigated through the analysis of the transient response of the driven gear by imposing a harmonic motion to the driving gear.

Influence of Misalignments on EHD Lubrication in Hypoid Gears

2007 ◽  
Author(s):  
Vilmos V. Simon
Keyword(s):  
Angular Position ◽  
Density Variation ◽  
Oil Viscosity ◽  
Hypoid Gears ◽  
Oil Film ◽  
Gear Teeth ◽  
Ehd Lubrication ◽  
Load Carrying ◽  
Tooth Surfaces ◽  
Oil Film Pressure

The thermal elastohydrodynamic analysis of lubrication is applied to investigate the influence of misalignments of the meshing members on EHD lubrication in hypoid gears. The calculation is based on the simultaneous solution of the Reynolds, elasticity, energy, and Laplace’s equations. The full thermal EHD lubrication analysis is applied, therefore, the oil viscosity variation with respect to pressure and temperature and the density variation with respect to pressure are included. The real shape of the gap existing between the contacting tooth surfaces is treated, based on gear teeth geometry defined by the gear processing method and including the misalignments of mating members. By using the corresponding computer program, the influence of pinion’s running offset and axial adjustment errors, and angular position error of pinion axis on maximum oil film pressure and temperature, EHD load carrying capacity, and on power losses in the oil film is investigated. The obtained results are presented and discussed.

Impact of a Lubricated Surface by a Sphere

1975 ◽  
Vol 97 (4) ◽  
pp. 613-615 ◽  
Author(s):  
H. D. Conway ◽  
H. C. Lee
Keyword(s):  
Flat Surface ◽  
Oil Viscosity ◽  
Film Pressure ◽  
Oil Film ◽  
Pressure Distributions ◽  
The Impact ◽  
Oil Film Pressure

This paper presents an analysis of the impact between a sphere and a flat surface covered by an oil film. Pressure distributions are found as functions of time for oils whose viscosities are either constant or pressure-dependent. It is believed that the increase of oil viscosity with pressure is a main cause of the deep conical dents observed experimentally.

Prevention of Nozzle Wear in Abrasive Water Suspension Jets (AWSJ) Using Porous Lubricated Nozzles

2002 ◽  
Vol 125 (1) ◽  
pp. 168-180 ◽  
Author(s):  
Umang Anand ◽  
Joseph Katz
Keyword(s):  
Flow Rate ◽  
High Speed ◽  
Abrasive Particle ◽  
High Viscosity ◽  
Oil Viscosity ◽  
Axisymmetric Nozzle ◽  
Oil Film ◽  
Nozzle Wear ◽  
Dimensional Facility ◽  
The Impact

This paper introduces a novel method for preventing nozzle wear in abrasive water jets. It consists of using a porous nozzle, surrounded by a reservoir containing high-viscosity lubricant, which is exposed to the same driving pressure as the flow in the nozzle. The pressure difference across the porous medium, generated due to the high-speed flow in the nozzle, continuously forces lubricant through it. The resulting thin oil film forming on the walls of the nozzle protects the walls from the impact and shear caused by the abrasive particles. The porous nozzles were manufactured using Electric Discharge Machining and examined with Scanning Electron Microscopy. Two test facilities were used for evaluating the porous lubricated nozzles. The first was a two-dimensional facility, supporting a 145 μm wide nozzle with windows on both sides, which enabled visualization of the oil film and measurements of the liquid and abrasive-particle velocities using Particle Image Velocimetry. The measured slip velocities were also compared to computed values from a simple numerical model involving one-way coupling. The second facility used a 200 μm axisymmetric nozzle to determine the extent of nozzle wear under different conditions. We found that the presence of an oil film substantially reduced the extent of nozzle wear, from 111 percent of the diameter, when the nozzle was not lubricated, to 4 percent, when the oil viscosity was 1800 mm2/s and its flow rate was 2.4 percent of the water flow (over the same period). The wear increased as the lubricant flow rate and viscosity decreased. The presence of the oil film also improved the coherence of the jet.

Vibration monitoring and strength of structural elements taking into account the inertial properties of materials under broadband vibration

2020 ◽  
Author(s):  
О.B. Skvortsov
Keyword(s):  
High Frequency ◽  
Cyclic Strength ◽  
Vibration Monitoring ◽  
Structural Elements ◽  
High Frequency Vibration ◽  
Latent Defects ◽  
Current State ◽  
Properties Of Materials ◽  
High Frequency Vibrations ◽  
The Impact

The paper considers influence of the inertial properties of structural materials on mechanical stresses under high-frequency vibrations. The necessity of considering acceleration estimates when creating vibration monitoring systems focused on the incorporating cyclic strength is proved. The importance of the effects of high-frequency vibration in the local areas of the structural material is noted, taking into account the formation of latent defects and reducing the fatigue limit during gigacycle fatigue. Recommendations are given concerning supplement to the vibration monitoring system, taking into account the decrease in strength under high-frequency vibration when solving problems of diagnostics, forecasting and protection with new innovative solutions. It provides increased reliability of the diagnosis and protection of equipment. In addition to evaluating the current state of the unit based on the results of vibration intensity measuring, the proposed solutions allow additional assessing the degree of wear and taking into account the impact of fatigue processes in the operation of a multi-level automatic protection system of the equipment.

Mitigating Peak Impact Forces by Customizing the Passive Foot Dynamics of Legged Robots

2020 ◽  
Vol 12 (5) ◽  
Author(s):  
Jesse J. Rond ◽  
Michael C. Cardani ◽  
Matthew I. Campbell ◽  
Jonathan W. Hurst
Keyword(s):  
High Frequency ◽  
Legged Locomotion ◽  
Control Algorithms ◽  
Maximum Compression ◽  
Impact Forces ◽  
Damping Material ◽  
Physical Testing ◽  
Force Peak ◽  
High Frequency Vibrations ◽  
The Impact

Abstract Impact forces are a destructive, yet common occurrence in legged locomotion. Every step produces a collision when the leg’s inertia stops as a result of ground contact. This results in peak forces and high-frequency vibrations that resonate through the system, damage components, and complicate control algorithms. Prior research considers how damping material, such as rubber, mitigates these effects. However, this paper shows the benefits of spring protection where both stiffness and maximum compression are customized to the leg. The spring mitigates the impact force peak by gradually bringing the leg’s inertia to rest. The maximum compression point (i.e., a hard stop) then provides a rigid surface that is ideal for stance. We provide a foot design methodology, validated through simulation and physical testing, that first considers springs in isolation, then in tandem with damping. We show that the coupling of springs and dampers reduces rigid body collisions and foot vibrations in a way that traditional methods—reliant on damping—have yet to achieve.

Acoustically Induced Vibration of Drums Excited by Rotating Machinery

2005 ◽  
Author(s):  
Itsuro Hayashi ◽  
Shijie Guo
Keyword(s):  
Fatigue Failure ◽  
High Frequency ◽  
Three Dimensional ◽  
Rotating Machinery ◽  
Coupled Analysis ◽  
Pressure Loading ◽  
High Frequency Region ◽  
One Dimensional ◽  
Material Fatigue ◽  
High Frequency Vibrations

Rotating machinery generates pressure pulsations, and the pulsations may cause severe vibrations of drums in high frequency region, resulting in material fatigue failure under certain conditions. Experiments and numerical simulations were performed to investigate the mechanism of the high frequency vibrations of the drums downstream of compressors. The results show that fatigue failure occurs when acoustic diametral modes of a drum are excited by pressure loading. In order to establish practical countermeasures against the vibrations, three-dimensional sound-structural coupled analysis as well as one-dimensional pulsation analysis were conducted. As a result, practical measures such as changing diameter, or thickness of the drums, applying restriction orifice are confirmed effective by using the approach proposed in this study. The validity of the simulation methods incorporating the sensitivity to the fluid conditions is shown.

Simulation of vibration piercing of pipe blank at press

2020 ◽  
Vol 76 (11) ◽  
pp. 1128-1138
Author(s):  
S. R. Rakhmanov
Keyword(s):  
High Frequency ◽  
Deformation Zone ◽  
Pipe Blank ◽  
Equipment Operation ◽  
Metal Deformation ◽  
Technological Tool ◽  
High Frequency Vibrations ◽  
Pipe Blanks ◽  
Wave Phenomena

In some cases, the processes of piercing or expanding pipe blanks involve the use of high-frequency active vibrations. However, due to insufficient knowledge, these processes are not widely used in the practice of seamless pipes production. In particular, the problems of increasing the efficiency of the processes of piercing or expanding a pipe blank at a piercing press using high-frequency vibrations are being solved without proper research and, as a rule, by experiments. The elaboration of modern technological processes for the production of seamless pipes using high-frequency vibrations is directly related to the choice of rational modes of metal deformation and the prediction resistance indicators of technological tools and the reliability of equipment operation. The creation of a mathematical model of the process of vibrating piercing (expansion) of an axisymmetric pipe blank at a piercing press of a pipe press facility is an actual task. A calculation scheme for the process of piercing a pipe plank has been elaborated. A dependence was obtained characterizing the speed of front of plastic deformation propagation on the speed of penetration of a vibrated axisymmetric mandrel into the pipe workpiece being pierced. The dynamic characteristics of the occurrence of wave phenomena in the metal being pierced under the influence of a vibrated tool have been determined, which significantly complements the previously known ideas about the stress-strain state of the metal in the deformation zone. The deformation fields in the zones of the disturbed region of the deformation zone were established, taking into account the high-frequency vibrations of the technological tool. It has been established that the choice of rational parameters (amplitude-frequency characteristics) of the vibration piercing process of a pipe blank results in significant increase in the efficiency of the process, the durability of the technological tool and the quality of the pierced blanks.

High-frequency, "quantum" and electromechanical effects in quasi-one-dimensional charge density wave conductors

2013 ◽  
Vol 183 (1) ◽  
pp. 33-54 ◽  
Author(s):  
Vadim Ya. Pokrovskii ◽  
Sergey G. Zybtsev ◽  
Maksim V. Nikitin ◽  
Irina G. Gorlova ◽  
Venera F. Nasretdinova ◽  
...  
Keyword(s):  
Charge Density ◽  
High Frequency ◽  
Charge Density Wave ◽  
Density Wave ◽  
One Dimensional ◽  
Electromechanical Effects

Global Algorithmic Capital Markets

2018 ◽  
Keyword(s):  
Public Policy ◽  
Capital Markets ◽  
Systemic Risk ◽  
High Frequency ◽  
Investor Protection ◽  
High Frequency Trading ◽  
Market Making ◽  
Market Governance ◽  
Policy Objectives ◽  
The Impact

This book illustrates and assesses the dramatic recent transformations in capital markets worldwide and the impact of those transformations. ‘Market making’ by humans in centralized markets has been replaced by supercomputers and algorithmic high frequency trading operating in often highly fragmented markets. How do recent market changes impact on core public policy objectives such as investor protection, reduction of systemic risk, fairness, efficiency, and transparency in markets? The operation and health of capital markets affect all of us and have profound implications for equality and justice in society. This unique set of chapters by leading scholars, industry insiders, and regulators sheds light on these and related questions and discusses ways to strengthen market governance for the benefit of society at large.

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