On the Growth Rate of Thermoelastic Instability

2004 ◽  
Vol 126 (1) ◽  
pp. 50-55 ◽  
Author(s):  
J. Y. Jang ◽  
M. M. Khonsari
Keyword(s):  
Growth Rate ◽  
Surface Roughness ◽  
Hot Spots ◽  
Wave Speed ◽  
Failure Process ◽  
Finite Thickness ◽  
Critical Value ◽  
Frictional Heat ◽  
Operating Speed ◽  
Thermoelastic Instability

Thermoelastic instability (TEI) is known to be directly related to the occurrence of hot spots in friction systems, such as brakes, seals, and clutches. TEI is a failure process where the local frictional heat, thermal expansion, contacting pressure and temperature grow rapidly over a certain critical value of the operating speed. In this article, we examine the rate of growth of instability and establish a link between the wave speed and the configuration of hot spots as well as its penetrating depth. The analysis includes provision for surface roughness and is capable of treating bodies of finite thickness with or without liquid lubrication.

Thermoelastic Instability With Consideration of Surface Roughness and Hydrodynamic Lubrication

1999 ◽  
Vol 122 (4) ◽  
pp. 725-732 ◽  
Author(s):  
J. Y. Jang ◽  
M. M. Khonsari
Keyword(s):  
Thermal Conductivity ◽  
Surface Roughness ◽  
Film Thickness ◽  
Hot Spots ◽  
Critical Speed ◽  
Hydrodynamic Lubrication ◽  
Lubricant Film Thickness ◽  
Governing Equations ◽  
Thermoelastic Instability ◽  
Liquid Lubricant

An idealized model consisting of a surface with high thermal conductivity separated by a film of liquid lubricant from a rough surface with low thermal conductivity is developed to study thermoelastic instability. The governing equations are derived and solved for the critical speed beyond which thermoelastic instability leading to the formation of hot spots is likely to occur. A series of dimensionless parameters is introduced which characterizes the thermoelastic behavior of the system. It is shown the surface roughness and the lubricant film thickness both play an important role on the threshold of instability. [S0742-4787(00)00104-1]

scholarly journals Моды волновода с пороговой нелинейностью

2020 ◽  
Vol 46 (16) ◽  
pp. 43
Author(s):  
С.Е. Савотченко
Keyword(s):  
Dielectric Constant ◽  
Optical Properties ◽  
Surface Waves ◽  
Nonlinear Optical ◽  
Layer Structure ◽  
Finite Thickness ◽  
Critical Value ◽  
Field Structure ◽  
Finite Width ◽  
Border Regions

A three-layer structure consisting of a nonlinear optical medium with a stepwise change in the dielectric constant inside which there is a dielectric layer of finite thickness is considered. The surface waves of two types of symmetry with a special field structure can propagate along the layers. Domains of finite width with different optical properties in the border regions in a nonlinear medium are formed. The formation of domains, as well as the existence of surface waves, occurs at interlayer thicknesses not exceeding a certain critical value.

scholarly journals Equipments to manage soil and irrigated rice straw for the sequential sowing of soybean in tropical floodplains1

2019 ◽  
Vol 49 ◽  
Author(s):  
José Geraldo da Silva ◽  
Adriano Stephan Nascente ◽  
Pedro Marques da Silveira
Keyword(s):  
Surface Roughness ◽  
Fuel Consumption ◽  
Rice Straw ◽  
Soil Surface ◽  
Plant Residues ◽  
Operating Speed ◽  
Randomized Design ◽  
Consequent Reduction ◽  
Soil Surface Roughness ◽  
Energetic Performance

ABSTRACT The presence of straw hinders the sowing of soybean cultivated in succession to rice, in areas irrigated by flooding. This study aimed to evaluate the combination of different configurations of a rice harvester and subsequent activities in the operational and energetic demand of rice straw management and in the soil surface roughness, in order to cultivate soybean in succession. Three independent experiments were conducted in a completely randomized design, as well as evaluated the fuel consumption, effective operating speed, working capacity and final surface roughness of the ground. The energy costs of harvesting rice do not increase when the automated harvester operates with a spreader to distribute the straw on the ground and to avoid the formation of furrows. The presence of rice plant residues in the field increases the skidding of the tractor when pulling the knife-roller, with a consequent reduction of the operating speed, but this does not affect the operational capacity and the fuel consumption. The increase in the number of light harrowings, from one to two operations, in areas worked with knife-roller or intermediate harrow, requires more time and fuel in the management of the soil and rice straw, but leaves the ground with less surface roughness. The management system with knife-roller operation and two light harrowings is the most appropriate method to prepare the soil for soybean cultivation after rice, because it provides the best combination of technical and energetic performance.

scholarly journals Qualitative Analysis of the Effect of Weeds Removal in Paddy Ecosystems in Fallow Season

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Leru Zhou ◽  
Zhigang Liu ◽  
Tiejun Zhou
Keyword(s):  
Growth Rate ◽  
Equilibrium State ◽  
Excretion Rate ◽  
Critical Value ◽  
Inorganic Fertilizer ◽  
Paddy Fields ◽  
Asymptotically Stable ◽  
Intrinsic Growth Rate ◽  
Stable Conditions ◽  
Coexistence Equilibrium

In the paper, we introduce a differential equations model of paddy ecosystems in the fallow season to study the effect of weeds removal from the paddy fields. We found that there is an unstable equilibrium of the extinction of weeds and herbivores in the system. When the intensity of weeds removal meets certain conditions and the intrinsic growth rate of herbivores is higher than their excretion rate, there is a coexistence equilibrium state in the system. By linearizing the system and using the Routh–Hurwitz criterion, we obtained the local asymptotically stable conditions of the coexistence equilibrium state. The critical value formula of the Hopf bifurcation is presented too. The model demonstrates that weeds removal from paddy fields could largely reduce the weeds biomass in the equilibrium state, but it also decreases the herbivore biomass, which probably reduces the content of inorganic fertilizer in the soil. We found a particular intensity of weeds removal that could result in the minimum content of inorganic fertilizer, suggesting weeds removal should be kept away from this intensity.

On the Formation of Hot Spots in Wet Clutch Systems

2001 ◽  
Vol 124 (2) ◽  
pp. 336-345 ◽  
Author(s):  
J. Y. Jang ◽  
M. M. Khonsari
Keyword(s):  
Hot Spots ◽  
Friction Material ◽  
Mechanical Seal ◽  
Comprehensive Model ◽  
Governing Equations ◽  
Thermoelastic Instability ◽  
Wet Clutch ◽  
Special Case

A comprehensive model is developed for analyzing the onset of thermoelastic instability in a wet clutch. For this purpose, appropriate governing equations are derived that take into account the porosity and deformability of the friction material. The effect of the thickness of the separator disk and that of the friction material are also included. The model is general and can be used to describe TEI in a variety of other systems such as in a mechanical seal, as a special case. A series of simulations are presented that predict the thermoelastic behavior of a wet clutch from an instability viewpoint.

Roughness, impurities and strain in low-temperature epitaxial silicon films grown by tantalum filament hot-wire chemical vapor deposition

2006 ◽  
Vol 910 ◽  
Author(s):  
Charles W. Teplin ◽  
Matthew Page ◽  
Eugene Iwaniczko ◽  
Kim M. Jones ◽  
Robert M. Ready ◽  
...  
Keyword(s):  
Growth Rate ◽  
Surface Roughness ◽  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Epitaxial Films ◽  
Silicon Films ◽  
Epitaxial Silicon ◽  
Hot Wire ◽  
Film Interface

AbstractWe grow epitaxial silicon films onto (100) silicon wafers from pure silane by hot-wire chemical vapor deposition (HWCVD). The films grow epitaxially for a thickness hepi before a Si:H cones nucleate and expand. We study the dependence of hepi on growth rate and the differences between Ta and W filaments. The surface morphology of thin but completely epitaxial films are studied in order to correlate the surface roughness during growth with the eventual epitaxial breakdown thickness. Surface roughness, strain and H at the wafer/film interface are not likely to cause the observed breakdown.

A STUDY ON THE FAILURE ANALYSIS OF CAST IRON BRAKE BLOCKS THAT ARE USED FOR RAILWAY APPLICATIONS

2006 ◽  
Vol 20 (25n27) ◽  
pp. 4535-4540
Author(s):  
CHANG-MIN SUH ◽  
BYUNG-WON HWANG ◽  
WOO-HO BAE
Keyword(s):  
Cast Iron ◽  
Hot Spots ◽  
Hot Spot ◽  
Frictional Heat ◽  
Failure Behavior ◽  
Surface Cracks ◽  
Element Analysis ◽  
Actual Application ◽  
The Matrix ◽  
Brake Block

In order to clarify the cracking and failure behavior of gray cast iron brake blocks that are used for the railway applications, macro- and micro observations regarding the cracks and the micro-structure of the used brake blocks were examined. Three brake blocks, which have different degrees of hot spots and cracking during the actual application, were selected for testing. In addition, a thermal-mechanical coupled finite element analysis (FEA) was applied to calculate the temperature and the stress field in the brake blocks during braking. As a result, it was observed that surface cracks were initiated at the hot spots and propagated into the matrix. From the observation of dispersed graphites close to the crack path, it can be said that the deterioration of materials due to the frictional heat of braking made it easy to initiate cracks at the hot spot. The hardness of the brake block was recommended to be under 85 by the Rockwell B scale in order to prevent hot spots and crack initiation. From the FEA, the procedure for the occurrence of hot spots and cracks was successfully simulated by assuming the surface roughness on the slid surface of the brake block.

scholarly journals Effect of ionospheric depth on the ionospheric feedback instability: cutoff and subsequent <I>E</I><sub>||</sub> modes

2010 ◽  
Vol 28 (9) ◽  
pp. 1777-1794 ◽  
Author(s):  
R. Cosgrove ◽  
R. Doe
Keyword(s):  
Growth Rate ◽  
Electric Fields ◽  
Finite Thickness ◽  
Higher Order ◽  
Plasma Structure ◽  
Higher Order Modes ◽  
Order Of Magnitude ◽  
E Region ◽  
The One ◽  
Two Fluid

Abstract. The ionospheric feedback instability (IFI), which involves feedback between ionospheric modifications and waves reflected off the magnetosphere, has up to this point been analyzed in terms of field line integrated (FLI) ionospheric quantities, that is, with the assumption that the ionospheric thickness can be ignored. In this work we test this assumption by solving the two-fluid equations for a representative ionospheric slab of finite thickness. We find that the results are for the most part incompatible with a description in terms of FLI quantities, and that their use can easily lead to an order of magnitude overestimation of the growth rate. This occurs because the first eigenmode, which is the one compatible with an FLI description, is cutoff above a certain frequency, leaving only higher order modes with wavelengths along B that are subsumed by the slab. Taking the results at face value, the parallel electric fields associated with the higher order modes are a possible contributor to electron heating and plasma structure in the E-region ionosphere.

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