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Wilczek A.,Technical University of Radom
Journal of Tribology | Year: 2011

This paper presents a model study of inductive, capacitive, and piezoelectric effects on the accuracy of pressure measurements in an EHD contact. Circuit and mathematical models of a thin-layer sensor and a measurement system were developed. It has been assumed that isolation layers of the sensor, deposited as SiOx (1 ≤ x ≤ 2) layers, have piezoelectric properties. The circuit model of the sensor contains a resistance, an electric capacitance, an inductance of a sensor's circuit, and an ideal current source representing piezoelectric properties of isolating layers of the sensor. The circuit model of the measurement system forms a full measuring bridge with the thin-layer sensor in one of its branches. A derived equation for output voltage of the measurement bridge was used as a mathematical model of the measurement system. The investigations show that at inappropriate electric parameters of the measurement system, inappropriate shape of the sensor's transducer and short transition time of the sensor through the contact zone, the capacitive, and piezoelectric effects have a significant impact on the accuracy of pressure measurement in the EHD contact. The transducer with an active part located along its connection edges (asymmetric transducer) and a transducer with the active part located in the middle of connections width (symmetric transducer) was tested. It was shown that in the case of the symmetric transducer, the pressure measurement signal change caused by the capacitive and piezoelectric effects, is much smaller than in the case of the asymmetric transducer. © 2011 American Society of Mechanical Engineers. Source

Blajer W.,Technical University of Radom
Computer Methods in Applied Mechanics and Engineering | Year: 2011

Multibody systems are frequently modeled as constrained systems, and the arising governing equations incorporate the closing constraint equations at the acceleration level. One consequence of accumulation of integration truncation errors is the phenomenon of violation of the lower-order constraint equations by the numerical solutions to the governing equations. The constraint drift usually tends to increase in time and may spoil reliability of the simulation results. In this paper a comparative study of three methods for constraint violation suppression is presented: the popular Baumgarte's constraint violation stabilization method, a projective scheme for constraint violation elimination, and a novel scheme patterned after that proposed recently by Braun and Goldfarb [D.J. Braun, M. Goldfarb, Eliminating constraint drift in the numerical simulation of constrained dynamical systems, Comput. Meth. Appl. Mech. Engrg., 198 (2009) 3151-3160]. The methods are confronted with respect to simplicity in applications, numerical effectiveness and influence on accuracy of the constraint-consistent motion. © 2011 Elsevier B.V. Source

Komorska I.,Technical University of Radom
Mechanika | Year: 2013

An engine vibration and noise signal being applied for the engine combustion assessment contains also information on: a valve clearance, head gasket damage and wearing out of elements of a vehicle drive system. As the engine mileage increases the wearing out of driving system elements also increases, and in consequence the characteristics of vibration and noise generated by individual sub-assemblies are changing. Diagnosing of defects can be performed on the grounds of the model-based vibroacoustic signal by comparing the measured signal with this mod-el. However, this model should be adapted after each changes of driving system elements and after each engine overhaul. Thus, it should be easily and fast automatically identifiable. Methods of generating the base model and its identification were proposed. The model based diagnostic method was verified - in the paper - on the example of the engine exhaust valve defect. Source

Walasek J.,Technical University of Radom
Macromolecular Theory and Simulations | Year: 2012

The theory presented starts from the model of gas of statistical segments with potential interactions between them. The fact that the system considered is an elastomer is incorporated into the model by constraints imposed on orientations of segments. Constraints are caused by the elastomer structure. The structure is determined by a connection of segments in linear chains, while chains are connected in the network structure. The statistical and thermodynamic description of the system is obtained by use of the conditional optimization of its free energy (Helmholtz function). The Lagrange multipliers for that optimization are calculated by use of cumulants and the multivariate method. In general, results of the theory presented are formulated for any type of potential interactions. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Kotnarowska D.,Technical University of Radom
Progress in Organic Coatings | Year: 2010

Destruction of epoxy coatings was examined under the influence of ageing with sulphuric acid aqueous solutions (3, 10 and 20%). The ageing caused oxidation, blistering and porosity increase of examined coatings as well as their surface roughness increase. © 2009 Elsevier B.V. All rights reserved. Source

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