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Analysis of the dynamics of the vibratory valve-injector
Get PDFConstruction of a novel vibratory valve-injector and its design optimization is presented in the paper. The principle of the system operation is based on the effect of dynamic positioning of a steel ball in a vibrating tube. Theoretical analysis of the stability of this non-linear system is coupled together with the experimental study of an operating valve. Laser holographic interferometry is used for the identification and optimization of working regimes of the syste
Vibratory stress relieving – it’s advantages as an alternative to thermal treatment
Get PDFThe aim of this study was to investigate the use of vibration to reduce the residual stress resulting from the welding process. Butt weld joints were subjected to vibration immediately after welding. The existing methods for relieving residual stress from welds are: mechanical, heat and electromagnetic. The mechanical method may be performed by hammering or vibration. The heat method consists of heating the whole welded piece or each weld, one by one. The electromagnetic method uses the electromagnetic hammer technique. In the heat treatment the part is heated until the yield point is reduced to less than the residual stress, which in turn causes local plastic distortion, decrease of the residual stress intensity and reduction of hardness. The vibration method introduces energy into the part by means of vibrations. For the stressed atomic structure there is no difference between the energy introduced through heat and the energy introduced through vibrations. The applied energy reorganizes the crystalline structure, relieving stress and stabilizing the piece, without distortion [1]. The article deals with reducement of welding stresses with the help of vibration treatment and to compare it with the classical heat treatment. The experiments were performed by a welding of structural low-alloy steel 16GS plates. Therefore the result is submitted by the mechanical tests and metal magnetic memory control. Several specimens, after welding and vibrotreatment, were cut off the welded plates and submitted for tensile, impact, hardness tests and metallographic analysis. The specimens, which were treated by vibration treatment, had strength and elasticity properties changed similarly as after the heat treatment. The metal magnetic memory test shows that this control method is suitable for evaluation of residual welding stresses variations after the weldment’s treatmen
Stable parametric identification of vibratory diagnostics objects
Get PDFA common model of vibratory diagnostics objects is the stochastic difference schemes, and theirs parametrical identification is carried out least squares and least absolute deviations techniques. It is well known that these techniques are unstable under stochastic heterogeneity of observable process, specifically, in the presence of outliers. One way to make the stable parametrical identification of vibratory diagnostics objects is implementation of generalized least absolute deviations method based on concave loss function. Obtained requirements to the loss function guaranteeing the steadiness evaluation, algorithms of identification and examples are presente
Investigation of actuators with smart links
Get PDFPrincipal schemes of actuators with smart links have been designed. Equations are presented for describing motion of a pneumatic actuator with viscous magnetorheological liquid and the vibration actuator with a smart link with shape memory. Amplitude-frequency characteristics of the vibration actuator and the pressure developed by the magnetorheological liquid vane have been determined. Application areas of the devices are propose
Analysis of holographic interferogram of microelectromechanical system with non harmonic cycles excitation
Get PDFRecent technological trends based on miniaturization of mechanical, electromechanical and photonic devices to the microscopic scale have led to the development of microelectromechanical systems (MEMS). Effective development of MEMS components requires the synergy of advanced design, analysis, and fabrication methodologies as well as application of quantitative metrology techniques for characterizing their performance, reliability and integrity during design stage. In this paper, we describe analysis of holographic interferograms of MEMS links which includes interferometric fringes related to deformation appearing because of the non-harmonic excitation of MEMS link
A surface micromachined comb drive with superior stability for application as an actuator
No full textThis paper presents results of ongoing research on fundamental issues related to comb drive, including mechanical and electrical properties. Attention is mostly focused on the case when comb drive is used as a power source with a cantilever beam attached to the moving plate. FEM simulations are carried out to show the resonant behaviour of balanced and unbalanced comb drive. Fringing effect, which helps to actuate the comb drive, is modeled. Different measurement approaches in frequency domain are discussed. Theoretical formulas are derived and analyzed. In this work we designed and fabricated both balanced and unbalanced comb drives using MUMPs (Multi-user MEMS Processes) technology. Balanced comb drives exhibit superior stability both in SEM observations and spectrum analysis. Formulas governing the spectrum are experimentally verified by mixing frequency measurement
Research of nonlinear electromechanical and vibro-impact interactions in electrostatically driven microactuator
Get PDFThis paper provides results of dynamic numerical analysis of nonlinear electromechanical and vibro-impact interactions in electrically-actuated contact-type microactuator, which is a common component in such devices as microswitches. Mathematical modeling was performed by means of finite element method, representing microactuator as a 3D cantilever microstructure and taking into account influence of bending forces generated by electrostatic field, damping forces due to squeezed air-film in the gap as well as bouncing of the microactuator tip upon its contact with substrate. Electrostatic-structural simulations were performed in order to predict actuation (pull-in) voltages of fabricated microswitches as well as to study influence of various system parameters on the value of the voltage. Results of these simulations were compared with experimental findings obtained by using electrical probe measurements of fabricated microswitches. Numerical analysis of free impact vibrations was carried out and allowed determination of effect of ambient air pressure and intermolecular adhesive interactions on the phenomenon of contact bouncin
Low – frequency acoustic instability of the working process in the combustion chamber of the solid propellant rocket engine
Get PDFThe following problems is investigated by statement of direct numerical experiment in offered paper. 1) The real oscillatory process is reproduced. 2) The mechanism of occurrence and refill of low-frequency acoustic instability in the combustion chamber of the solid propellant rocket.. The direct numerical modeling of low-frequency acoustic instability will be carried out by a Davydov’s method. This powerful numerical method was discovered by Yuri M. Davydov 40 years ago as the method of large particles The further modern complex improvement of this numerical technique was titled Davydov’s method. It is good itself recommending at the decision of many tasks of the mechanics of continuous media. The description of physical and mathematical model of flow in the rocket engine combustion chamber is given. The results of numerical modeling are resulted. The hydrodynamical deeply nonlinear nature of low-frequency fluctuations connected to structure and character of current in the combustion chamber of the solid propellant rocket engine proves to be tru
Vibration control of cantilever beam
Get PDFThe paper describes two approaches to problem of active damping of vibrations of cantilever beam. First one uses standard LTI (linear time invariant) mathematical model of the system and state feedback with the state observer designed by pole placement method. The incomplete pole assignment method is used instead of the standard full assignment. The second one is based on experimental identification of the first mode shape and design dynamic compensator. Experimental results of both methods are compared. The problem of robustness of the compensator by frequency domain method based on the unstructured uncertainty of the model is also addresse
Possibilities of assessment of reliability of an anthropotechnical system
Get PDF"Reliability and safety characteristics [7] of an anthropotechnical system are the basic information about the correctness of relation between a man (e.g. pilot) and a helicopter (machine). Methods of defining them are still an open problem. The article presents an innovative way of definition of reliability characteristics of a pilot and a helicopter engine as well as an entire anthropotechnical system. Described are theoretical bases of this method, which are various configurations of the ""equation of state"" describing relations pilot – helicopter and helicopter – pilot [8, 9]. Defined was the set of ""numbers of limit state violations"" of the parameter of pilot’s physical condition aP and technical state of the helicopter aS, which as ""premises of damage"" were used for calculation of estimators of reliability characteristics. It is noteworthy that these characteristics could be particularly useful in the process of comparing different pilots and helicopters in various situations appearing in the course of utilisation