Mathematical models for acoustical pollution prognosis at signalized intersections

Noise related problems are increasing worldwide with detrimental effects on health and quality of life[18]. The regulations and laws of European Union and Lithuania emphasize the importance of noise reduction, the necessity to collect and disseminate information related to traffic flow, the development of traffic flow mathematical models and their implementation for noise evaluation. In this paper, mathematical methods are applied to determine the noise intensity. Measurements of urban traffic noise were performed at the arterial street intersections in Kaunas ant its suburbs. At this location traffic flow rates are high and noise is dominated by low frequencies. It was determined that the LAeq levels decrease continuously till the end of cycle of the green traffic signal. The developed methodology can be used to estimate traffic noise levels in a city and country districts using data provided by the automated traffic flow registration system. The aim of the article is to develop the mathematical model of a longitudinal noise sources and to apply it for the prediction of acoustical pollution in an environment of roads and streets intersections

Investigation of vibro-acoustic properties of modern lathe collet chuck

Manufacturing industry has been attempting to attain the required cutting performance in order to achieve high precision, fast productivity and lower maintenance costs. Vibrations generated during machining can be a serious problem degrading component quality, precision, tool service life, lathe performance and cutting rates. This paper is concerned with analysis of cutting process by using modal testing. Static and dynamic deformations of lathe collet chuck have a significant impact on cutting process stability, which affects workpiece quality and production output. Modal analysis was applied to develop a mathematical model of chucks dynamics, which consist of a number of mode shapes each with natural frequency and modal damping. Modal analysis and experimental measurements were performed on a collet chuck of CNC lathe installed in metal working company UAB “Stevila”

Vibrations of a double wall plane adaptive to electrorheological materials

An analytical study of vibrations response and control capabilities of an Electrorheological (ER) material-filled double wall plate to random excitation pressure is presented. The governing equations of motion are developed by incorporating the ER material constitutive relations to thin face plate equations. A three-parameter viscoelastic model is used to characterize ER material behaviour in pre-yield regime. The effect of electric field strength on the response of the double wall sandwich plate with ER material is investigated. Numerical results include response spectral densities and modal frequencies for several ER material core thicknesses and different electric field level

Prognostics of vibration induced risk to operators of agricultural machinery

Frequent use of vibrating hand-held tools and operation of machinery can result in various chronic diseases. Operators of machinery are often afflicted with peripheral and systematic disorders. The statistical data collected over several decades clearly indicate the lack of operator’s safety from exposure to vibrations. The causes and impacts of vibration effects on humans are reviewed in annual reports by health and safety experts in many countries. One of the most common occupational diseases that has been frequently reported is the musculoskeletal disorder due to extended exposure to mechanical vibrations. The influence of vibrations during time period τ can be described by vibro-energy load aτ2·τ. If this load value over a specified time period does not exceed the permissible level a2·T0, it will not induce negative effects on human health. This approach was used in the present study for the prediction of hands and whole body vibration effects on operators of various vibration inducing machinery. Agricultural operators were selected as test subjects, since agricultural tractors and other mobile machinery emit high levels of vibration. Vibration data were obtained from statistical reports developed in the time period from 1988 to 2008. It was found that majority of agricultural machinery does not guarantee proper vibration safety. Thus organizational prevention methods should be developed and implemented. Reduction of vibrations by various technical methods and/or reduction of vibration exposure could be costly, but they are needed in order to provide effective solutions in reducing vibration risk to operators

Investigation of grain separation through straw layer over …

Straw walker is a separator that separates grain from straw, and limits the efficiency of combine-harvesters therefore special attention is devoted to the development and improvement of its design and technological parameters. The most important parameter of walker operation is Froude-number k that depends on the amplitude of the straw walker movement in vertical direction, i.e., walker sieve oscillation amplitude r and angular velocity ω. High speed camera used in the investigation tests helped to determine not only the behavior of the straw layers on the oscillating sieve of straw walker but also the duration of grain penetration (separation) through the straw. With estimation of these parameters the rational values of Froude-number k were substantiated. It has been determined that at various ω and r combinations when k=const. sieve vertical accelerations when the crankshaft is rotated at the same angle are equal, but speeds and displacements are varied. For this reason the duration of grain separation is different. The rational angular velocity of the crankshaft is 22.5 s-1 (r=0.05 m), as then the straw layer when the crankshaft is rotated at the angle 2π, raised from the walker surface (sieve) the most early and strokes with it latest, i.e. the duration of free movement of the straw is 1.5 times longer and the grain separation about 15% more intensive than when ω=21.5 s-1. The estimation of grain separation enabled to define critical value of crankshaft angular velocity equal to ω=23.5 s-1. When this value is exceeded the top straw layers receive only one stroke when the crankshaft is rotated at the angle 4π, therefore the increase of crankshaft angular velocity and, simultaneously, sieve oscillation intensity above the critical value is inexpedient

Investigagation of vibrations of variable cross-section linking elements

The applicability of analytical models for vibrations of variable cross-section two- layered cylindrical structural elements is investigated. Natural frequencies of longitudinal and lateral vibrations are calculated and validated experimentally. Natural frequency )( 0 n ? dependence on material properties (?, E) and geometric parameters (l, R, r, S) of structural element provide means for optimization of vibration amplitude characteristic

Vibration and noise measurements during silage thickening with inertia directional vibrator

Literature review and performed theoretical investigation indicates that it is environmentally and economically feasible for small and average size farms to use vibrational thickening method for silage preparation. However, the results need to be verified with experiments. This research work provides analysis and evaluation of flat surface inertia type vibrator, in which the excitation force is induced by turning the unbalanced mass. Directed action vibrator was manufactured and tested. Results indicate that application of inertia directional vibrator for thickening of finely chopped corn and Jerusalem artichoke stalk mixture, after 40 minutes thickening, allows to obtain a 114.6 kg m-3 density for both layers, while thickening the first 65 kg mass mixture layer after 10 minutes - a 197.9 kg m-3 density. Dry material densities correspond to 61.5 and 106.3 kg m-3 respectively. After examination of fodder quality it was determined that corn mixture silage, thickened by the inertia directional vibrator, satisfies highgrade silage requirements. Performed tests demonstrated that the effect of vibrations on whole body and the measured noise levels do not have detrimental effect on human health and the established acceptable limits are not exceeded while operating the inertia directional vibrator. The vibrator is suitable for silage preparation since it does not contaminate the fodder with dirt and gasoline products during operation. The proposed silage preparation method provides opportunities to use ecologically safe containers as well as sectional and other types of enclosure