Applied Mechanics and Materials Vol. 430

Abstract: The paper presents the nonlinear torsional vibrations control of the joints in an articulated industrial robot, in Simulink /MATLAB. In this case, it is considered the classical linear control combined with compensations of the natural discontinuous nonlinearities in a robot with low speed.

Abstract: In this article is presented a dynamic mathematical model for a new type of dynamic balancing system, having a driving solution of the rotating part based on magnetic interactions. Experimental studies for evaluation of the dynamic stiffness and damping due to the magnetic coupling were performed by measuring the radial mobility of the whole system. The experimental studies were used to improve the analytical model.

Abstract: Various mechanical systems contain highspeed rotating bodies, which are affected by small eccentricities. During operation, such shape irregularities are the cause of vibrations that can produce malfunctioning, as well as early wear development in the bearings and in other parts of the devices. In order to control and reduce these undesirable effects, the eccentricity of the rotors must be determined, which, due to their geometrical complexity, can be seldom achieved by direct measurement. The paper proposes an analytic-experimental method for determining the eccentricity of a cantilever rotor, based on the statistical processing of data obtained by measuring the vibrations of its bearing. The application of the method is illustrated on a laboratory testing model built by the authors.

Abstract: The paper studies the vibration transmitted by a mechanical oscillating system to its fixing device. The influence of the mechanical characteristics (inertial and elastic) of the device on the quantities specific to the free and forced vibration, respectively, of the principal system, is analyzed. In this context, the paper investigates the possibility to correlate the vibrations of the mechanical system with the vibrations measured on the fixing device. The conclusions of this study can be used for the calibration of vibration measuring stands. In the final part, a practical application is presented, aimed to compare the theoretical results with the data obtained by measurements performed on an experimental model built by the authors.

Abstract: The application of Bondsim library for the stochastic vibrations modelling andsimulation is given in this paper. For that purpose the stochastic Bondsim elementsare used. The efficiency of the proposed approach for modeling and simulation ofstochastic dynamic systems vibrations is illustrated using an example ofhydraulic ram pump.

Abstract: The primary processing represents an important link of the process of capitalization of vegetal-origin products and, at the same time, an essential operation of the conditioning chain. Taking into account all considerations, the experts׳ attention has been drawn by the study of phenomena which influence upon the impurities separation process, aiming at a maximum reduction impurities. The paper presents the constructive-functional scheme of an gravitational separator SP-0 0 design, manufactured and testing at INMA Bucharest and the movement Eq. of gravitational separator centrifugally driven by means of non-balanced eccentric masses and also the constructive scheme of electric motovibrator, in view of its utilisation with best results for the drive of vibrating sieves of technical equipments used for impurities separation out of cereal seeds.

Abstract: The elastic impact of a free kinematic link with a surface is studied using MATLAB and SolidWorks. The differential equations of motion are developed using an elastic nonlinear contact force and a frictional force. The nonlinear equations of motion are written in an external m-file and are solved using numerical techniques. The results are checked using a simulation in SolidWorks. For the SolidWorks simulation a specific force is defined for the the elastic impact. The numerical results are obtained with the two methods are compared. The vertical elastic displacement during impact has lower values less for the frictional case.

Abstract: The paper presents a numerical example of utilizing a synthesis tool to determine the parameters and structures of machine drive systems in the form of torsional vibration models. In addition, the paper presents the algorithm for determining the values of controlling force parameters an active synthesis. The presented method makes it possible to choose a controlling force to maintain loads within the rated range under specified operating conditions.

Abstract: In the present paper aspects regarding the analytical modeling, the simulation and the experiments related to random vibrations, with applications to automotive industry, are discussed. Simplified car dynamical models based on lumped masses, springs and dampers being exposed to random vibrations, are considered. The power spectral density is used to define the excitation produced by the unevenness of the road surface which are correlated to the vehicle speed. Two different approaches are observed in parallel. The analytical one is using the dynamical model of the car, the random excitation estimation, the transfer functions from the excitation sources to the target, and the response at the comfort points or the points of interest. The associated numerical calculations are performed with Matlab. For the second approach the finite element models of the car simplified structure are created and the simulations are performed. Statistical tools are used to describe the excitation sources and the response. Good correlation of the results for the two approached is observed. In the sequel a real car component made of plastic is considered. The estimation of the component structure stress with probability of 1σ, 2σ and 3σ, are coming out from the simulation of the part subjected to random vibrations by using finite element analysis. Frequency response functions (FRF) are experimentally measured in the laboratory by placing the plastic component on a shaker. The measured FRFs and the results are compared to the ones resulted from the simulation, observing a good correlation. The output of the random vibration analysis can be used to estimate the fatigue of the component.

Abstract: In this paper, a model with four degrees of freedom is studied to assess the discomfort of car passengers due to vibrations. The response of the half car model due to road irregularities is presented in order to attain a control method for the dampers. For the analytical study, the differential equations of the motion were written in order to determine the critical frequencies. The resulted model takes into account both the forced and damped solution for a numerical case, thus giving a more detailed overview of the phenomena. Using this numerical case, a control method can be developed to reduce the passenger discomfort, based on the motion diagrams.