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Kelvin Voigt’s model of single piezoelectric plate
Get PDFAssemblies and subassemblies based on a piezoelectric effect, in construction and operation of machines, have been used for decades. Among important examples of the piezoelectric elements can be distinguish non-destructive testing methods of a various objects, such as an ultrasonic diagnostic technique, in which a piezoelectric film is glued on a surface of a tested object. In this article an impact of these phenomena on the dynamic characteristics of a modeled system will be examined. It is a base for a study of complex piezoelectric plates by other methods. Moreover, a damping of the systems in a single piezoelectric plate will be considered
Parameter identification of aircraft thin-walled structures using incomplete measurements
Get PDFEarly parametric identification is critical for the decision making of repair or replacement in order to guarantee structural safety. Nowadays, aircraft thin-walled structures are widely applied in aero-/astronautics areas and their health conditions receive considerable attention. Parameter identification in aircraft thin-walled structures is more challenging because of the structural complexity. In this research, a new time-domain analysis method, the sequential nonlinear least square estimation (SNLSE) method, along with model reduction technique is proposed to identify the parameters of aircraft thin-walled structures using vibration data, which is referred to as the reduced order model based SNLSE approach. Herein, model reduction technique is used to reduce the number of degrees of freedom for conducive to the placement of sensors and high-efficiency calculation by SNLSE method. Simulation and experimental studies have been conducted for the parameter identification of the aluminum thin-walled structure. As demonstrated by simulation and experimental results, the proposed approach using incomplete measurements is very effective in parameter identification of aircraft thin-walled structures
Correlation of shear-wave velocities and cone resistance of quaternary glacial sandy soils defined by Seismic Cone Penetration Test (SCPT)
Get PDFThe derivation of dynamic geotechnical parameters of soil are of primary importance in designing specific structures. Direct measurements are expensive and time-consuming. In this study the correlation between the seismic wave velocities and cone resistance was derived from seismic cone penetration testing (SCPT) of Quaternary glacial sandy soils in Lithuania. The close relationship was obtained for sandy soils indicating wide range of cone resistance and seismic wave velocities. The correlation is as high as R = 0.80. The derived regression equation could be reasonably used in assessing dynamic geotechnical and seismic parameters in Lithuania and other territories characterized by similar geological conditions using conventional cone penetration testing (CPT) method. It enables consistent geotechnical and seismic zoning of sandy soils
Numerical model of journal bearing lubrication considering a bending stiffness effect
Get PDFAn analysis for operating characteristics of journal bearing lubrication system is performed based on the numerical model. Dynamic bearing lubrication characteristics such as oil film pressure and thickness distribution can be analyzed through a numerical model with an integration of elastohydrodynamics and multi-flexible-body dynamics (MFBD). In particular, the oil film thickness variation by elastic deformation is considered in the elastohydrodynamic analysis by applying the bending stiffness effect of journal. And the oil film thickness variation by the bending stiffness effect is applied to the fluid governing equations to calculate the oil film pressure in the elastohydrodynamic lubrication region. A series of process proposed in this study is available for the analysis of realistic elastohydrodynamic lubrication phenomenon. Also, a numerical example for the journal bearing lubrication system is demonstrated and compared with the experimental results. The numerical results considering the bending stiffness effect show a good agreement with the experimental results
Nonlinear dynamic characteristics of SMA simply supported beam in axial stochastic excitation
Get PDFIn this paper, nonlinear dynamic characteristics of shape memory alloy (SMA) simply supported beam in axial stochastic excitation were studied. Von del Pol nonlinear difference item was introduced to interpret the hysteresis phenomenon of the strain-stress curve of SMA, and the hysteretic nonlinear dynamic model of SMA simply supported beam in axial stochastic excitation was developed. The local stochastic stability of the system was analyzed according to the largest Lyapunov exponent, and the global stochastic stability of the system was discussed in singular boundary theory. The steady-state probability density function and the joint probability density function of the system were obtained in quasi-nonintegrable Hamiltonian system theory. The result of simulation shows that the stability of the trivial solution varies with bifurcation parameter, and stochastic Hopf bifurcation appears in the process. The result is helpful to stochastic bifurcation control to SMA simply supported beam
Experimental and numerical investigation on the structural performance of the tensioning air beam system
Get PDFAn experimental and numerical study on the structural performance of the tensioning air beam system (TABS) is presented. TABS is a hybrid structural system consisting of a membrane air beam, steel frames and cable struts. This system has the advantage of reduced self-weight and is easy to construct while it can improve the load bearing capacity of membrane structures. It maximizes the structural capacities of individual elements, thus can be considered as a very effective system in terms of both structural and economical aspects. In this paper, a test was carried out to examine the structural performance of TABS under different membrane pressure conditions. The material properties of the air beam were obtained from the results of two membrane tensile strength tests, which were performed prior to the main test. A simple numerical model was proposed to predict the structural behavior of TABS and its validity was evaluated by comparing its results with the test values
Design and numerical analysis of a novel coaxial rotorcraft UAV
Get PDFThis paper reports the design of a novel coaxial rotorcraft UAV with canard wing, main wing and tail rotor, which is capable of converting status between contra-rotating case model and fixed wing model. Computational fluid dynamics approach involving momentum source method is adopted to study its aerodynamic characteristics in various states. A validation case is introduced in this paper to verify the reliability and precision of this method. The result proves that the designed coaxial rotorcraft UAV is able to hover, take off and land vertically as well as change between the contra-rotating case model and the fixed wing model. Accordingly, it is able to accomplish various operating statuses and demonstrate good aerodynamic characteristics during the whole fight envelope
A survey of Hopf bifurcation analysis in nonlinear railway wheelset dynamics
Get PDFThis article attempts to analyze the Hopf bifurcation behavior of a railway wheelset in the presence of dead-zone and yaw damper nonlinearities. A model that is more precise than Yang and Ahmadian is investigated. Using Bogoliubov-Mitropolsky averaging method and critical speed, the amplitude of the limit cycle in the presence of the mentioned nonlinearities is taken into consideration. To solve these nonlinear equations analytically, the integration interval has been divided into three sub-domains. Two-dimensional bifurcation diagrams are provided to illustrate the mechanism of formation of Hopf bifurcation. These diagrams can be used for design of stable wheelset systems
Damage localization by wavelet analysis of uniform load surface
Get PDFThis paper presents a new technique for identifying damages in beam-type structures based on wavelet analysis of uniform load surface (ULS). Having come into focus in the field of damage detection, wavelet analysis revealed itself as a practical and state-of-the-art signal processing method for discerning abnormalities of mode shapes of structures, where the irregularities are considered as the indications of cracks. ULS is beneficial in terms of participating lower mode shapes and better immunity to noise. Continuous wavelet transform (CWT) is employed to analyze the ULS in order to find the damage site. The proposed method does not require any prior knowledge of the structure and combines the synergistic advantages of ULS technique and CWT to provide more accurate results in the face of high signal to noise ratio. A numerical study is conducted and three kinds of wavelets are utilized to evaluate the technique, namely symmetrical 4, Gaussian 4 and bior 6.8. The procedure is also experimentally investigated using a free-free beam structure
Frequency domain identification of the active 3D mechanical structure for the vibration control system
Get PDFNowadays structures are light and compliance therefore such structures are opened to the influence of external and internal excitations which in results lead to the structure vibrations and cause a loss of the energy which is used in the process realized by the structure. For example: arms, antennas, satellite solar batteries or slender skyscrapers are such plants. To damp the vibrations and save loss energy we develop design the active vibration control systems. To design such control system we should realized very important stages beginning from analytical investigations through process identification of the dynamical system. The 3D bar structure with sticked parallel piezo-stacks into chosen bars is considered in the paper. Piezo-elements play a role of piezo-actuators, while two eddy-current sensors located in free plane the structure are used to measurement displacement in directions X and Y. Such control plane will be considered as a two input and two output (TITO) system. As a result of analytical and numerical investigations such system was divided to two single input single output (SISO) subsystems. Such the coupled system was used in the process of the full model identification. The chirp signal was applied in identification process. The structure was excited according to single input single output controlling force while outputs signals were measured in perpendicular direction X and Y. In such way we have confirmed that for control purposes the plant can be decupled