Journal of Theoretical and Applied Mechanics

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		Geometrical Nature of Linear System Design: Introduction to Optimal Linear Closed-Loop System Design Al. Cheremensky Institute of Mechanics, Bulg. Acad. Sci., Sofia It is proved that the feedback principle universality claimed by N. Wiener is ensured exclusively by linear system intrinsic properties, namely: almost all solutions of a linear system can be realized with the help of the corresponding feedback. In the case of the incomplete measurements, it is shown that there is the feedback polymorphism. JTAM, Sofia, vol. 26 Issue 2 pp. 09-24 (1996), [Full Article]

		Analysis of Skew-Axes Gears with Plane Region of Mesh V. Abadjiev, D. Petrova, V. Guenov Institute of Mechanics, Bulg. Acad. Sci., Sofia What is considered is a special type of skew-axes gears with a planar region of mesh and whose tooth surfaces are generated by Olivier's second principle. It means that the one of the gears is cut by a tool which is a copy of the another one. The tool has the same relative position and performs the same relative motion as the larger gear. The problem is to analyze the conditions of meshing of such type of gears. JTAM, Sofia, vol. 26 Issue 2 pp. 25-30 (1996), [Full Article]

		Dynamic Characteristics and Loadings of Controlled Start and Stop Processes of Battery-Powered Universal Fork Lift Truck P. Petrov Balkancar-Engineering Ltd., Sofia A dynamic plane model of universal electric fork lift truck is created. The characteristics of the basic units in the electric power circuit are considered and the mechanical system is presented in terms of four masses and six generalized coordinates, associated with the rigidities and resistances. The effect of the controlled moment of the electric traction motor is considered, as well as the road resistance and the controlled braking moment in the brakes. A mathematical model and a computer programme are created to perform the motion parameters calculation their velocities and the loadings in some assemblies, units and joints, under either contactor or pulse control of the electric traction motor in the case of controlled start and stop mode; forward and backward motion mode. Results of a calculation experiments are presented. JTAM, Sofia, vol. 26 Issue 2 pp. 31-45 (1996), [Full Article]

		In-Situ Full-Scale Testing of 1000 MW Unit of NPP Kozloduy for Determination of its Dynamic Characteristics S. M. Simeonov, K. D. Hadjiyski, M. V. Haralanov Central Laboratory for Seismic Mechanics and Earthquake Engineering, Bulg. Acad. Sci., Sofia An experimental study by means of in situ full-scale forced vibrations tests of the 1000 MW Unit 5 of NPP Kozloduy have been carried out. The results are used for verification of the analytical investigations of the latest seismic safety programme. The dynamic properties of the reactor and auxiliary building structures have been experimentally identified taking into account their interaction and the effect of the special equipment and the foundation soil. The experimental procedure, the results and their application for correction of the spatial models are discussed. At the end some conclusions are given. JTAM, Sofia, vol. 26 Issue 2 pp. 46-55 (1996), [Full Article]

		Self-Excited Oscillations with Mixed Friction Regimes when Reading the Hydrodynamic Theory of Lubrication S. Butchvarov, S. Karapetkov Technical University, Sofia This paper deals with a dynamics model with two degrees of freedom on the basis of which a profound analysis is made about the excitation and behaviour of the self-excited oscillation. At the same time reads the hydrodynamics action of lubrication and dry friction with its dynamic performance. The differential equations are solved in analytical way by the averaging method. The dynamic proposed model gives an explanation of the objective laws, which we observe by the origin of the friction oscillations with mixed friction. JTAM, Sofia, vol. 26 Issue 2 pp. 56-65 (1996), [Full Article]

		A Cross-strip Scheme of Bubnov-Galerkiu Method to Determine the Frequencies of Rectangular Plates El. Gavrilova Mining and Geological University, Sofia A cross-strip scheme of the Bubnov-Galerkin method is used to obtain the eigenvalue equation for the free vibrations of thin rectangular plates. Numerical results for the natural frequency parameters of plates with divers combinations of clamped and simply-supported edges are presented, and a comparison with previously published results is made. JTAM, Sofia, vol. 26 Issue 2 pp. 66-79 (1996), [Full Article]

		Determination of Stress Concentration in a Nonlinear-elastic Plane with a Circular Hole for the Case of Known Displacement Vector at the Boundary P. Pavlov, R. Raev Technical University, Rousse The class of materials considered in the present paper is the so-called harmonic material. A discrete algorithm is constructed for determination of stress concentration coefficient on circular opening outline in elastic plane. The problem is solved with analytical methods. JTAM, Sofia, vol. 26 Issue 2 pp. 80-85 (1996), [Full Article]

		On the Concept about Distribution of Stress along a Rod Subjected to an Impact V. Baranov, I. Lopa, H. Hristov, Z. Chiwikov ¹Tula State University, Russia ²Unit 42660, Ministry of Defence, Sofia, Bulgaria ³F "Dunarit", Rousse, Bulgaria This paper postulates the possibility for analytic presentation of compression stress along the length of a rod, as a wave, for an elastic visco-ductile material of Malvern-Sokolovski, in case of longitudinal compressing impact with a solid mass. Dependences are obtained and they are convenient to apply in order to solve prognostic tasks for dynamic longitudinal instability of parts of a rod, loaded by a wave of compressing stresses. JTAM, Sofia, vol. 26 Issue 2 pp. 86-90 (1996), [Full Article]

		Brittle Crack Propagation in Structural Steels G. Kortenski Institute of Metal Science, Bulg. Acad. Sci., Sofia This paper describes the results of an investigation on brittle crack propagation in structural steels, as well as the measurement method of crack propagation rate. The critical fracture toughness KId, crack arrest toughness KIa and crack propagation toughness KID values have been measured for wide range of loading rates. JTAM, Sofia, vol. 26 Issue 2 pp. 91-94 (1996), [Full Article]