American Journal of Applied Sciences 6 (1): 48-56, 2009 ISSN 1546-9239 © 2009 Science Publications Corresponding Author: D.I. Stoicovici, Department of Engineering and Technological Management, North University of Baia Mare, Str. Dr. Victor Babe, Nr. 62A, 430083 Baia Mare, Romania Tel: +40 262 218922 Fax: +40 262 276153 48 Computer Model For Sieves’ Vibrations Analysis, Using an Algorithm Based on the False-Position Method Dinu I. Stoicovici, Miorita Ungureanu, Nicu Ungureanu and Mihai Banica Department of Engineering and Technological Management, North University of Baia Mare, Str. Dr. Victor Babes, Nr. 62A, 430083 Baia Mare, Romania Abstract: The analysis of the sieves vibrations in the case of screening civil engineering construction bulk materials is usual made by using some differential equations depending on parameters related to different material and sieves characteristics. One of those parameters is the throwing coefficient -c- that is the ratio between the force capable to throw up the particle from the sieve surface, and the gravity of this particle. The throwing coefficient is one of the most important characteristics of a sieve dynamic behavior and its values are often used to establish a particular case to the sieve oscillations. In order to find the position of a particle that jump on the screen surface, a system of 6 differential equations with 6 unknown integrating constants can be established. All the involved equations are in transcendent form and it is necessary to solve the system by computer algorithms. First of all, the 6 unknown integrating constants are replaced with related linear relations depending on the throwing coefficient. Secondly, an original computer algorithm based on the so-called false-position method is proposed. In order to validate it, the new system of 6 differential equations depending on the throwing coefficient is solved for some particular cases of the particle jumps. Finally, the solutions are compared for the same conditions of the initial used system. The conclusion is that in the case of the construction bulk materials, the two systems give almost similar solutions. In this case, the new system depending on the throwing coefficient is much easier to work with that the initial system. Another advantage is that in the very first steps one can choose the throwing coefficient and establish the best vibrating regime. Key words: Bulk construction material, sieves, throwing coefficient, false-position method INTRODUCTION Establishing the most favorable vibration operation conditions for swinging screens is the essential problem when devising such equipment. The amplitude and the frequency of vibrations are the decisive factors that influence the vibrating conditions. The sieves operate best in over-critical angular resonant regime, at high frequencies coupled with small amplitudes for materials with a mainly fine grading, and at small frequencies coupled with high amplitudes for sorting materials with mainly coarse grading. In the literature [1,2] , there are guiding principles that recommend how to adopt the frequencies, the amplitudes, and how to adopt the dynamical conditions. The most used vibrating system in screening construction bulk material is the inertia one. In Fig. 1 the main components of such equipment are presented. Screen t  Sieve Vibration generator   Fig. 1: Inertia vibrating one-deck screen components For the case of sorting construction bulk material on vibrating screens with inertia driving system, the over- critical regime is generally adopted, because it has lower sensitivity to perturbations. For example, when