Browsing by Author "Aleksandrova V."
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Item 3D SPACE KINEMATICS OF A ROBOT FOR PROCESS AUTOMATION IN METALLURGY(2024-01-01) Slavov V.; Aleksandrova V.This paper presents the main results of a study on the kinematics in 3D space of a robot used for process automation in metallurgy. The robot is studied as a mechanical system with twelve degrees of freedom consisting of seven rigid bodies. The transition matrices between the local and reference coordinate systems are defined in symbolic form. The position vectors and linear velocities of characteristic points are also defined in symbolic form as well as angular velocities of bodies from the mechanical system. A calculation algorithm is compiled and entered into a standard mathematical software product. Results are obtained in symbolic form and are valid for all mechanical systems with an analogous dynamic model. The kinematics results represent a basis for studying the dynamics and vibrations of a robot for automating processes in metallurgy.Item Carbonate - apatite forming ability of polyphase glass - ceramics in the CaO - MgO - SiO2 system(2015-01-01) Mihailova I.; Radev L.; Aleksandrova V.; Colova I.; Salvado I.M.M.; Fernandes M.H.V.Several types of glass-ceramics in the CaO - MgO - SiO2 system are shown to be bioactive, biocompatible and exhibiting various advantages for bone regeneration. A polyphase calcium-magnesium-silicate glass-ceramics is prepared by the sol-gel method including a two-step thermal treatment procedure aiming to investigate the effect of its phase composition on the in-vitro bioactivity observed. The dried gels of a chemical composition 3CaO.MgO.2SiO2 corresponding to merwinite are thermally treated at 700°C and 1100°C. The structural behavior of the synthesized samples is examined by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). Larnite as the main crystalline phase, accompanied by merwinite, akermanite and periclase are detected after heat treatment at 1100°C. The in-vitro bioactivity of the glass-ceramics is detected by investigating the apatite formation ability in Simulated Body Fluid (SBF) for different times of soaking. The changes on the surface of the immersed samples and the formation of Mg- and Si-substituted carbonated apatites are verified by FTIR, SEM and Energy Dispersive Spectroscopy (EDS) techniques. The dissolution behavior of the glass-ceramics in SBF is also carried out by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). The results indicate fast degradation in SBF and high reactivity of the polyphase glass-ceramics. The latter might be used as a bioactive implant material.Item Cyclic loading of rubbers - amplitude spectrum and payne effect(2017-01-01) Hadjov K.; Aleksandrova V.Introducing nonlinear integral constitutive equation with singular kernels the authors have obtained the stressstrain hysteresis curves in the case of imposed large strains (stresses), respectively. The respective solutions of the integral equations are represented in Fourier series, which coefficients being convergent are used to obtain the Fourier amplitude spectrum and the amplitude dependence (decreasing) of the storage modulus - the so called Payne effect. The respective enhancement of the compliance with the imposed stress amplitude is also discussed. The experimental data obtained for polyisoprene rubber well agree with the theoretical predictions.Item FREE UNDAMPED SPATIAL VIBRATIONS OF A ROBOT FOR PROCESS AUTOMATION IN METALLURGY(2024-01-01) Slavov V.; Aleksandrova V.This paper presents the results of mechano-mathematical modeling of free undamped spatial vibrations of a robot for process automation in metallurgy. A dynamic model of the robot is made. It is studied as a mechanical system with twelve degrees of freedom, contained by seven rigid bodies. Kinetic and potential energy are derived symbolically by using the kinematics study results. The matrices characterizing the mass-inertial and elastic properties of the mechanical system are obtained. The differential equations that describe the free undamped vibrations are derived. They take into account the geometrical, mass, inertial and elastic characteristics of the mechanical system. A compiled calculation algorithm is entered into a standard mathematical software product. Results are obtained in symbolic and graphical form. The natural frequencies and natural mode of a robot with concrete parameters are determined. Results of the study of free undamped vibrations represent a basis for studying of the free damped and forced vibrations of a robot for process automation in metallurgy.