The Vibroacoustic Behavior of a Rotating Annular Complex Plate With Application to the Design of Circular Saws

1995 ◽  
Author(s):  
Noureddine Atalla ◽  
André Côté ◽  
Benoît Cournoyer ◽  
Jean Nicolas
Keyword(s):  
Experimental Data ◽  
Noise Reduction ◽  
Variational Approach ◽  
Annular Plate ◽  
Theoretical Models ◽  
Viscoelastic Damping ◽  
Circular Saw ◽  
Constrained Damping ◽  
Effects Of Rotation ◽  
Circular Saws

Abstract This paper discusses the vibroacoustic behavior of an annular rotating complex plate with application to the design of circular saws. The effects of rotation and constrained viscoelastic damping are investigated both theoretically and experimentally. On the theoretical front, a model based on the variational approach has been developed. Special attention has been devoted to 1) the effects of rotation on both the vibration and the noise radiated by the annular plate and 2) the optimization of viscoelastic constrained damping. On the experimental front, several set ups have been devised to validate the theoretical models and to test some noise reduction avenues. Examples showing predictions from the theoretical models will be presented together with comparisons to experimental data. Finally, application of the above results to the design of a quieter circular saw will be discussed.

Statistical and Theoretical Models of Ingestion Through Turbine Rim Seals

2012 ◽  
Vol 135 (2) ◽  
Author(s):  
Kunyuan Zhou ◽  
Simon N. Wood ◽  
J. Michael Owen
Keyword(s):  
Experimental Data ◽  
Statistical Model ◽  
Flow Parameter ◽  
Likelihood Estimation ◽  
Theoretical Models ◽  
Operating Conditions ◽  
Data Points ◽  
Effects Of Rotation ◽  
Effectiveness Data ◽  
Good Agreement

In recent papers, orifice models have been developed to calculate the amount of ingestion, or ingress, that occurs through gas-turbine rim seals. These theoretical models can be used for externally induced (EI) ingress, where the pressure differences in the main gas path are dominant, and for rotationally induced (RI) ingress, where the effects of rotation in the wheel space are dominant. Explicit “effectiveness equations,” derived from the orifice models, are used to express the flow rate of sealing air in terms of the sealing effectiveness. These equations contain two unknown terms: Φmin, a sealing flow parameter, and Γc, the ratio of the discharge coefficients for ingress and egress. The two unknowns can be determined from concentration measurements in experimental rigs. In this paper, maximum likelihood estimation is used to fit the effectiveness equations to experimental data and to determine the optimum values of Φmin and Γc. The statistical model is validated numerically using noisy data generated from the effectiveness equations, and the simulated tests show the dangers of drawing conclusions from sparse data points. Using the statistical model, good agreement between the theoretical curves and several sets of previously published effectiveness data is achieved for both EI and RI ingress. The statistical and theoretical models have also been used to analyze previously unpublished experimental data, the results of which are included in separate papers. It is the ultimate aim of this research to apply the effectiveness data obtained at rig conditions to engine-operating conditions.

Statistical and Theoretical Models of Ingestion Through Turbine Rim Seals

2011 ◽  
Author(s):  
Kunyuan Zhou ◽  
Simon N. Wood ◽  
J. Michael Owen
Keyword(s):  
Experimental Data ◽  
Statistical Model ◽  
Flow Parameter ◽  
Likelihood Estimation ◽  
Theoretical Models ◽  
Operating Conditions ◽  
Data Points ◽  
Effects Of Rotation ◽  
Effectiveness Data ◽  
Good Agreement

In recent papers, orifice models have been developed to calculate the amount of ingestion, or ingress, that occurs through gas-turbine rim seals. These theoretical models can be used for externally-induced (EI) ingress, where the pressure differences in the main gas path are dominant, and for rotationally-induced (RI) ingress, where the effects of rotation in the wheel-space are dominant. Explicit ‘effectiveness equations’, derived from the orifice models, are used to express the flow rate of sealing air in terms of the sealing effectiveness. These equations contain two unknown terms: Φmin, a sealing flow parameter, and Γc, the ratio of the discharge coefficients for ingress and egress. The two unknowns can be determined from concentration measurements in experimental rigs. In this paper, maximum likelihood estimation is used to fit the effectiveness equations to experimental data and to determine the optimum values of Φmin and Γc. The statistical model is validated numerically using noisy data generated from the effectiveness equations, and the simulated tests show the dangers of drawing conclusions from sparse data points. Using the statistical model, good agreement between the theoretical curves and several sets of previously-published effectiveness data is achieved for both EI and RI ingress. The statistical and theoretical models have also been used to analyse previously-unpublished experimental data, the results of which are included in separate papers. It is the ultimate aim of this research to apply the effectiveness data obtained at rig conditions to engine-operating conditions.

TEMPERATURE DEPENDENCE BEHAVIOR OF ELECTRICAL RESISTIVITY IN NOBLE METALS AT LOW TEMPERATURES

2014 ◽  
Vol 5 (3) ◽  
pp. 982-992 ◽  
Author(s):  
M AL-Jalali
Keyword(s):  
Experimental Data ◽  
Electrical Resistivity ◽  
Temperature Dependence ◽  
Concentration Dependence ◽  
Low Temperatures ◽  
Noble Metals ◽  
Phonon Scattering ◽  
Theoretical Models ◽  
Residual Resistivity ◽  
Electron Phonon Scattering

Resistivity temperature – dependence and residual resistivity concentration-dependence in pure noble metals(Cu, Ag, Au) have been studied at low temperatures. Dominations of electron – dislocation and impurity, electron-electron, and electron-phonon scattering were analyzed, contribution of these mechanisms to resistivity were discussed, taking into consideration existing theoretical models and available experimental data, where some new results and ideas were investigated.

Simple theoretical models of elimination reactions on polar catalysts; Dehydration reactivity of secondary alcohols on acidic and basic catalysts

1985 ◽  
Vol 50 (4) ◽  
pp. 920-929 ◽  
Author(s):  
Jiří Sedláček
Keyword(s):  
Experimental Data ◽  
Quantum Chemical ◽  
Theoretical Models ◽  
Aliphatic Alcohols ◽  
Secondary Alcohols ◽  
Carbonium Ion ◽  
Dehydration Reactions ◽  
Aromatic Alcohols ◽  
Basic Catalysts ◽  
Simple Models

CNDO/2 calculations for simple models of adsorption and dehydration reactions of secondary aliphatic and aromatic alcohols on polar catalysts are presented. The models involve selected stages of elimination mechanisms of various types (E1, E2 and E1cB elimination). Calculated quantum chemical quantities were correlated with reported experimental data. It is shown that reactivities for the series of substituted phenylethanols correlate very well with the ease of carbonium ion formation. In the case of aliphatic alcohols, calculated quantities correlate generally with the reactivities on SiO2 and are in anticorrelation with the reactivities on Al2O3.NaOH.

scholarly journals Exhaust Noise Reduction by Application of Expanded Collecting System in Pneumatic Tools and Machines

Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1592
Author(s):  
Dominik Gryboś ◽  
Jacek S. Leszczyński ◽  
Dorota Czopek ◽  
Jerzy Wiciak
Keyword(s):  
Experimental Data ◽  
Mathematical Model ◽  
Noise Reduction ◽  
Sound Pressure ◽  
Acoustic Pressure ◽  
Pressure Level ◽  
Computational Results ◽  
Noise Measurements ◽  
Exhaust Noise ◽  
Collecting System

In this paper, we demonstrate how to reduce the noise level of expanded air from pneumatic tools. Instead of a muffler, we propose the expanded collecting system, where the air expands through the pneumatic tube and expansion collector. We have elaborated a mathematical model which illustrates the dynamics of the air flow, as well as the acoustic pressure at the end of the tube. The computational results were compared with experimental data to check the air dynamics and sound pressure. Moreover, the study presents the methodology of noise measurement generated in a pneumatic screwdriver in a quiet back room and on a window-fitting stand in a production hall. In addition, we have performed noise measurements for the pneumatic screwdriver and the pneumatic screwdriver on an industrial scale. These measurements prove the noise reduction of the pneumatic tools when the expanded collecting system is used. When the expanded collecting system was applied to the screwdriver, the measured Sound Pressure Level (SPL) decreased from 87 to 80 dB(A).

Modeling and Experimental Validation of the Effective Bulk Modulus of a Mixture of Hydraulic Oil and Air

2014 ◽  
Vol 136 (5) ◽  
Author(s):  
Hossein Gholizadeh ◽  
Doug Bitner ◽  
Richard Burton ◽  
Greg Schoenau
Keyword(s):  
Experimental Data ◽  
Bulk Modulus ◽  
Theoretical Models ◽  
Operating Conditions ◽  
Air Bubbles ◽  
Pressure Sensitivity ◽  
Hydraulic Oil ◽  
Effective Bulk Modulus ◽  
Experimental Apparatus ◽  
Major Factors

It is well known that the presence of entrained air bubbles in hydraulic oil can significantly reduce the effective bulk modulus of hydraulic oil. The effective bulk modulus of a mixture of oil and air as pressure changes is considerably different than when the oil and air are not mixed. Theoretical models have been proposed in the literature to simulate the pressure sensitivity of the effective bulk modulus of this mixture. However, limited amounts of experimental data are available to prove the validity of the models under various operating conditions. The major factors that affect pressure sensitivity of the effective bulk modulus of the mixture are the amount of air bubbles, their size and the distribution, and rate of compression of the mixture. An experimental apparatus was designed to investigate the effect of these variables on the effective bulk modulus of the mixture. The experimental results were compared with existing theoretical models, and it was found that the theoretical models only matched the experimental data under specific conditions. The purpose of this paper is to specify the conditions in which the current theoretical models can be used to represent the real behavior of the pressure sensitivity of the effective bulk modulus of the mixture. Additionally, a new theoretical model is proposed for situations where the current models fail to truly represent the experimental data.

The Mechanical Analysis of the Composite Reinforced Circular Saw Blade

2011 ◽  
Vol 228-229 ◽  
pp. 484-489
Author(s):  
Xiao Ling Wang ◽  
Zhong Jun Yin ◽  
Chao Zhang
Keyword(s):  
Volume Fraction ◽  
Mechanical Analysis ◽  
Loading Conditions ◽  
Circular Saw ◽  
Model And Simulation ◽  
Circular Saw Blade ◽  
Saw Blade ◽  
Reinforcement Model ◽  
Circular Saws ◽  
Composite Reinforcement

Thinner saw blades cannot resist large lateral cutting forces due to their lower stiffness. In this paper we propose a composite reinforcement method to improve the mechanical properties of circular saw blades. We analyze and simulate the stress and strain fields of our proposed reinforced circular saws by Finite element method. Our analytical results contain not only influences of reinforcing parameters but also loading conditions on the lateral stiffness and the natural frequency of composite saw blades. Here the reinforcing parameters include: 1) the reinforcement location on circular saw blades, 2) the volume fraction of the reinforcements, 3) the number of the reinforcements; and loading conditions include: 1) the cutting force, 2) the rotational speed. Our composite reinforcement model and simulation results can contribute to a better design of circular saw blades.

scholarly journals IMPROVEMENT OF THE ROUGHNESS FORECASTING MODEL OF COATING OF NON-RIGID ROAD PAVEMENT COATING

2021 ◽  
Vol 4 (164) ◽  
pp. 71-76
Author(s):  
A. Batrakova ◽  
H. Sarkisian ◽  
E. Zakharova
Keyword(s):  
Experimental Data ◽  
Service Life ◽  
Pearson Correlation ◽  
Safety Margin ◽  
Calculated Data ◽  
Statistical Processing ◽  
Theoretical Models ◽  
Rigid Pavement ◽  
Improved Model ◽  
Over Time

To ensure safe, comfortable driving at high speeds, a strong, even surface is required for the entire life of the pavement. In this regard, the issue of predicting changes in the equality of coverage over time is very important. The article considers the peculiarities of changing the longitudinal equality of the road surface. Purpose is to improve the model of forecasting the equality of non-rigid pavement. Methods – analytical and experimental. The analysis of existing decisions on the issue of forecasting the equality of coverage is performed. The most important factors influencing the change in the equality of road coverage have been identified. Based on the analysis of theoretical models and a number of experimental data, an improved model for predicting the equality of coverage of non-rigid pavement is proposed. MathCAD and MS Excel were involved in the development of an improved model that takes into account the most important factors. The model of change of coverage roughness, where increase in the roughness index over time is considered as a function of such parameters, is improved: the modulus of pavement elasticity (actual or required); the number of load cycles for t years of pavement operation; the share of trucks in the traffic flow; the factor of safety margin of the pavement structure. The adequacy of the developed model of changing the roughness of coverage is confirmed by statistical processing of experimental data obtained by the thesis author and other researchers on public roads with different service life, and calculated data under the theoretical model. The Pearson correlation coefficient between experimental and calculated data is more than 0.95, which indicates the adequacy of the developed model. Compared to the well-known models of forecasting coverage roughness, the improved model allows to apply a wider range of values of the general equivalent modulus of elasticity of pavement design (from 100 MPa to 600 MPa) and to receive forecast values of roughness for service life of non-rigid pavement over 5 years.

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