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Bucharest, Romania

Baldovin D.,Institute of Solid Mechanics | Baldovin S.,Polytechnic University of Bucharest
Romanian Journal of Acoustics and Vibration | Year: 2012

Conventional railway vehicle systems exhibit lateral instability phenomenon doe to self-induced oscillations of the rigid axle wheelsets, which increases component wear and imposes operating speed limits. To improve the stability performances, without increasing the rail-wheel interaction forces above safety limits, elastic joints and dissipative devices are used to connect the wheelset to the bogie frame. Using the linear elastic and damping model, this paper derives the governing differential equations of motion for a bogie with independently rotating wheelsets. The bogie is modeled by a 6 degree-of-freedom (DOF) system which considers the lateral displacement and yaw angle of each wheelset and the lateral displacement and yaw angle of the truck frame. The equations of motion of the mechanical model, were proceeding in a Matlab-Simulink program. In this paper is presented the influence of the damping coefficients of the model on the hunting motion stability of the considered bogie by numerical simulations. Source

Picu M.,University of Galati | Sireteanu T.,Institute of Solid Mechanics
Proceedings of the Romanian Academy Series A - Mathematics Physics Technical Sciences Information Science | Year: 2016

After an exposure to vibrations, the sensitivity of the mechanoreceptors in fingers is temporary altered and that the subjects suffer from paresthesia and numbness. So far it is not known how significant these temporary changes are, what is the frequency dependence or their likely repercussions on employment security. The subjects (10 men aged 20 to 25 years, perfectly healthy) were irradiated with vibrations with 1.2; 2.8; 5.8 şi 10.5 m/s2, for 10 and 20 min; frequencies were: 4; 16; 31.5; 63; 125; 250 şi 500 Hz. Subsequent, the subjects were tested with the Semmes-Weinstein test and Purdue Pegboard test. It is found that the results almost coincide for the two tests. This means that a prolonged irradiation with accelerations exceeding 2.8m/s2, subjects lose control of the fingers. If we compare the variation of the weighting factors based on the acceleration for these two tests with the variation of the weighting factors based on ISO 5349-1: 2001 we can see a total discrepancy. It can therefore be concluded that, as far as the vibration perception threshold is concerned, and therefore the sensitivity of the mechanoreceptors and the development of temporary neurological impairment, the ISO frequency weighting has no value. Source

Sireteanu T.,Institute of Solid Mechanics | Nastac S.,University of Galati | Picu M.,University of Galati
Proceedings of the Romanian Academy Series A - Mathematics Physics Technical Sciences Information Science | Year: 2011

The paper is based on the nonlinear biomechanical model developed by Hill. The central idea of this study is the behavioural and structural optimization of this model so that it emphasizes the auto adaptive capacity of the real biomechanical system. The paper analyses and compares the responses to harmonic and step signals. A version of the Hill model which contains nonlinear elastic and dissipative elements was developed based on observed results. It has also been established the constitutive law of these additional elements so that the initial objective of the study to be met. The evaluation of characteristic measurements and completing the final expression of the constitutive equation have been established taking into account a series of experimental results developed on the actual model of the hand-arm system subjected to dynamic vibration actions. The results of this research provide the necessary foundation and support for future implementations of this version of Hill's model in some virtual tools to analyze the dynamics of the human body subjected to vibration or shock. Source

Sharifimajd B.,Institute of Solid Mechanics | Olvander J.,Linkoping University | Stalhand J.,Linkoping University
International Journal for Numerical Methods in Biomedical Engineering | Year: 2016

There are limited experimental data to characterize the mechanical response of human myometrium. A method is presented in this work to identify mechanical parameters describing the active response of human myometrium from the in vivo intrauterine pressure measurements. The human uterine contraction during labor is simulated by implementing a coupled model in a finite element scheme, and the intrauterine pressure is evaluated as the outcome. A meta-model is developed to approximate the finite element simulation response with a lower computational cost and used to identify model parameters through fitting its prediction to the in vivo measurements. © 2016 John Wiley & Sons, Ltd. Source

Krejci P.,Institute of Solid Mechanics | Bradac M.,Institute of Solid Mechanics
Mechatronics: Recent Technological and Scientific Advances | Year: 2011

The paper deals with using LabVIEW graphical programming language for design and prototyping of mechatronic system controller. The paper describes possibility of using LabVIEW Real-Time and LabVIEW ARM module for control of electronic automotive throttle valve and its controller development. The advantage of this approach is using high-level graphical design tools for programming of RISC processors instead of using low level programming techniques. This allows to engineers quick transitions from hardware and software development to deployment. Source

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