Solid State Phenomena Vols. 147-149

Abstract: The study is devoted to the electromagnetic induction device (EID) attached to the magnetorheological (MR) damper. The study covers design considerations, calculations of magnetic field, fabrication and testing of the EID on the dynamic testing machine (DTM).

Abstract: The paper presents results of investigation on physico-chemical (among others – mechanical) properties of epoxy coatings subjected to the ageing with ultraviolet radiation and such aggressive media as 20% aqueous solutions of: sodium chloride, potassium hydroxide and sulfuric acid (for 1080 h).

Abstract: This paper is devoted to modeling of a three-layered cantilever beam filled with magnetorheological (MR) fluid. The beam consists of two aluminium outer layers and an MR fluid layer placed between them. The study covers description of MR fluid behavior in the pre-yield regime, analysis of strain and internal forces, formulation of differential equations of motion and finite element model (FEM) and numerical calculations. The aim of the study is to determine maximal amplitudes up to which the MR fluid operates in the pre-yield regime.

Abstract: In this paper we address the design of the controller for semi-active vehicle suspension system that employs an MR damper as the actuator. MR dampers are nonlinear devices which are difficult to model. Several MR damper forward models have been proposed; they can estimate the damping force of the device taking variables such as control voltage and velocity inputs. However, the inverse model, i.e., the model that computes the control variable is even more difficult to find due to the numerical complexity that implies the inverse of the nonlinear forward model. In our case, we develop a neural network able to reproduce such inverse dynamics. This neural network is connected to a backstepping controller that estimates the damping force to reduce the vibrations of the system. The performance of the controller is evaluated by means of simulations in MATLAB/Simulink.

Abstract: A systematic investigation of the fabrication process, microstructure and treatment technology of the Rare earth oxide doped Mo cermet (REO-Mo in brief) on the secondary electron emission (SEE) mainly has been performed. The REO-Mo samples were fabricated by liquid-liquid, Liquid-Solid and Liquid-Liquid doping method and subsequently by the Spark Plasma Sintering (SPS) techniques. It was found that the uniform mixing of REO with Mo would have considerable benefit for enhancement of SEE coefficient (δ). Annealing the cathode in hydrogen (called as the pre-activation treatment) could greatly improve the SEE performance by removing the absorbed water and oxygen at the cathode surface which might cause the oxidation of molybdenum during cathode high temperature operation. It is found that the activation temperature of REO-Mo cathode annealed in hydrogen could decrease to 1000oC, about 300oC lower than that of the cathode without pre-activation treatment, which is favorable for the practical application.

Abstract: Vanadium doped, nitrogen doped, and vanadium and nitrogen co-doped SrTiO3 powders with size of 20-30 nm in diameter were prepared by high energy milling method respectively. It was found that compared with those of pure SrTiO3, the photocatalytic activities of these three doped SrTiO3 samples for decomposing NO under visible light (λ>400 nm) and near ultraviolet light (λ>290 nm) irradiation were improved, and the co-doped sample exhibited the highest photocatalytic activity. 43.2% NO could be eliminated under the irradiation of light with wavelength larger than 400nm, about 3 times higher than that by pure SrTiO3. The photocatalytic activity of this sample near ultraviolet range is about 1.7 times higher than that of pure SrTiO3. The high visible light photocatalytic activity of this substance may be due to the high visible light absorption and large specific surface area.

Abstract: Vitreous enamel is a glassy coating formed on a metal substrate by firing at temperatures above 800 °C. The quality of vitreous enamel coating depends on the pre-treatment of the steel substrate surface and the quality of enamel slip. The main aim of this study was to characterize the composition of the steel substrate surface after firing with double finish, to explain the effect of steel substrate surface pre-treatment (blasting, acid pickling) on forming the phase interface of the steel substrate – vitreous coating system, and on its final microhardness, fracture strength and the adhesive properties of the coating. To achieve these aims, the following experimental methods were used: Mössbauer spectroscopy, X-ray diffraction, electron analyzer, and EDAX. Based on the chemical composition of the initial enamel slip and the firing technology, the metal - enamel system interface exhibited various ratios of layers of magnetite, hematite, nonstoichiometric wüstite, and crystals of faylite. The measuring results indicate that the quality and age of enamel slip influences the brittle fracture properties of vitreous enamel coating.

Abstract: Piezoelectric transducers have been used extensively as the distributed actuators and sensors in active control of structural vibrations. Piezoelectric actuator/sensors are distributively bonded on or embedded in the host structure and have the inherent advantage of integrating over their surface area, which leads to potentially more robust implementations as compared to implementations that use shaker/accelerometers. For this reason piezoelectric actuator/sensors have attracted more and more attention in recent years. In this paper, a theoretical analysis is presented of the active control of a vibrating beam using collocated triangular and rectangular piezoelectric actuator/sensor pairs. The aim of this study is to generate points of zero displacements and zero slopes at any designated position. So the control systems impose a virtual clamped boundary condition at the control position on the beam, in which both displacement and slope are driven to zero. Two independent single-input single-output (SISO) control systems similar to direct velocity feedback (DVFB) are implemented, i.e. for the rectangular pair the voltage signal measured by a triangular piezoelectric sensor is electronically multiplied by a fixed gain and fed directly back to a collocated piezoelectric actuator. The triangular and rectangular piezoelectric actuator/ sensor pairs positioned at one end of the beam are used to measure and control the displacement and slope of the structure respectively. The active control systems are unconditionally stable for any type of primary disturbance acting on the structure due to the collocated actuator/sensors. It should be noted that the presented control strategy is different to DVFB. In DVFB, when the control gain is increased, the vibration energy of the beam is initially reduced at resonance frequencies because of the active damping effect. However this effect does not continue. When large control gains are implemented, the overall kinetic energy of the beam is increased to the same or even higher values than those of the beam without control systems because the vibration of the beam is rearranged into a new set of lightly damped resonance frequencies. Imposing a virtual clamped boundary condition at the control position is clearly more complicated than DVFB, because in addition to the zero displacement constraints, the zero slope constraints must also be satisfied. The proposed control system allows for certain points of the structure to remain stationary without using any rigid supports. Furthermore, such control systems have the potential to create a region of nearly zero vibration for any ‘excitation’ frequency. This means that no progressive waves or reflected waves exist in the designated region, thus significantly reducing the vibration level in that region of the beam. The control systems impose a virtual clamped boundary condition at the control position on the beam in which the displacement and slope are driven to zero. As a result, the vibration of the actively controlled beam can be described in terms of two beams clamped at the control position. A numerical analysis is then performed to verify the proposed control system. It is found that the new resonance frequencies and mode shapes seen in the simulations are consistent with the natural frequencies and natural modes of the controlled beam derived analytically. The capability of the proposed method for generating a zero-vibration region is also numerically demonstrated.

Abstract: The paper presents analysis of flexural vibrating machatronic system. Considered system is compounded of a cantilever bending beam and a strip-like piezoelectric transducer. The transducer is bonded with the beam surface by means of connection layer which has homogeneous properties in whole length. External RC circuit is adjoined to the transducer’s clamps. This mechatronic system is loaded with harmoniousness variable force. Beam’s vibrations affect piezoelectric transducer through the agency of connection layer which generates electric charge and produces additional stiffness. Dynamic equations of considered mechatronic system were determined on the basis of elementary beam and transducer’s section dynamic equilibrium. Transducer’s dynamic equation was assigned using transducer’s piezoelectric properties. Dynamic flexibility of considered mechatronic system was assigned on the basis of approximate Galerkin’s method. Solution of beam’s differential motion’s equation was defined as a product of time and displacement’s eigenfunctions which satisfy defined boundary conditions. Dynamic characteristic of considered mechatronic system, including pure shear of the connection layer was assigned on the end of the beam and illustrated on the chart at the same time taking into account beam and transducer’s geometrical and material parameters.

Abstract: Some applications, like force feedback joystick, require force measurement with high stiffness sensor to limit handle oscillations. In this way, this article presents an original technology to measure static force using the resonance frequency variation principle of a piezoelectric actuator subject to preload variation. We present in a first part comparison of various involved technologies to justify our choice (stiffness, inertia.....). The second part deals with the analytical modelling by variational principle of Langevin transducer. A comparison with the numerical FEM results is performed. Experimental results are then reached to validate the detailed concept. They demonstrate the potentiality of static force measurement with classical resonant structure like Langevin transducer with laboratory instruments. A last part is dedicated to the definition of an electronic to supply the sensor and to treat the measure. First experimental results are presented in an open loop electronic power supply configuration.