With the increased application of ultrasonic motors, it is necessary to put forward higher demand for the adaptability to environment. Impact, as a type of extreme environment, is widespread in weapon systems, machinery and aerospace. However, there are few reports about the influence of impact on an ultrasonic motor. This article aimed to study the reasons for the performance degradation and failure mechanism of an ultrasonic motor in a shock environment. First, a finite element model is established to observe the dynamic response of ultrasonic motor in a shock environment. Meanwhile, the reasons of the performance degradation in the motor are discussed. An impact experiment is carried out to test the influence of impact on an ultrasonic motor, including the influence on the mechanical characteristic of an ultrasonic motor and the vibration characteristic of a stator. In addition, the protection effect of rubber on an ultrasonic motor in a shock environment is verified via an experimental method. This article reveals the failure mechanism of ultrasonic motors in a shock environment and provides a basis for the improvement of the anti-impact property of ultrasonic motors.
Lead lanthanum zirconate titanate actuators taken as one type of photo-deformable actuators have been widely applied for micro-driven systems and active vibration control of photostrictive laminated flexible structures. However, the slow response of photodeformation of single patch lead lanthanum zirconate titanate actuator greatly affects its application. In this article, the main factors for the slow response of the lead lanthanum zirconate titanate actuator are investigated using experimental method. The increasing temperature during light on state and the residual photovoltage and photodeformation during light off state are considered as dominant factors causing the slow response of the lead lanthanum zirconate titanate actuator. To gain a better driving capability of lead lanthanum zirconate titanate actuator, some effective solutions through weakening the effect of increasing temperature and eliminating residual photovoltage and photodeformation are proposed and experimentally validated in this article. Considering the effective solutions proposed in this article, a novel optical driving mechanism based on multi-patches combination is proposed.
The interval identification of dynamic loads for uncertain structures was performed primarily by the interval perturbation method (IPM). Influences of structural epistemic uncertainties on unknown loads cannot be effectively quantified for now and the interval inversion needs to be furtherly investigated. In this paper, Tikhonov regularized technique for the inverse analysis is integrated into a non-intrusive de/re-uncertainty procedure, i.e. the dimension-wise analysis, to reconstruct unknown loads under structural epistemic uncertainties. The proposed method transforms the interval identification model at zero-cut of fuzzy inputs into a finite number of classical ones with crisp parameters, regularized solutions to which are adopted to construct a polynomial approximation of each slice of the unknown load. The extreme point set of each approximation at zero-cut is derived to calculate its minimum/maximum (min/max) points at any alpha-cut with respect to the corresponding uncertain parameter, from which the min/max input vectors of the unknown load are assembled in a dimension-wise manner. Subsequently, the interval bounds of the unknown load at each alpha-cut can thus be evaluated by Tikhonov regularized inversion, based on which the fuzzy description is obtained. The effectiveness of the proposed method is validated by the inclusion of the unknown load in the identified result and a tighter identified interval suggests its accuracy advantage over the IPM if the same regularization method is adopted.
DOI : 10.1016/j.cma.2019.112718
ISSN: 0045-7825 Cilt: 360 Sayfa: 112718
The design of laminated composite microplate resonators with high quality (Q) factors requires careful analysis of thermoelastic damping since it is an inherent intrinsic energy dissipation mechanism. This paper presents a temperature field in a general trilayered microplate with thermally perfect interfaces based on the integral transform approach. In addition, an analytical model to calculate thermoelastic damping in general trilayered fully clamped microplates is developed. Total thermoelastic damping for trilayered microplates can be expressed as a sum of the normalized energy dissipated in each layer. In order to validate the present model, the results calculated by the present model are compared with those calculated by finite element method (FEM). Our results show that the energy dissipation in the middle part is less than that in the outer parts for homogenous microplates. Thermoelastic damping peaks in trilayered microplates are discussed, which are associated with the critical damping frequency and the Zener's modulus of each layer. When the Zener's modulus of one layer is 2–3 orders of magnitude higher than that of another layer and the critical damping frequency of this layer is also 2–3 orders of magnitude higher than that of another layer, the thermoelastic dissipation spectrum will exhibit multiple peaks. It is also observed that the second layer may exhibit negative energy dissipation in SiC/Ti/Au and Si3N4/Si/Au trilayered microplates.
DOI : 10.1016/j.ijmecsci.2018.12.015
ISSN: 0020-7403 Cilt: 151 Sayfa: 595-608
PLZT (lanthanum-doped lead zirconate titanate) ceramic has obtained widespread applications in the engineering fields. Especially, it has broad application prospects in driving field. In this article, aiming at the proposed opto-electrostatic hybrid driving torsion actuator, the influence of different factors on driving voltage and output deformation is analyzed and verified by a new mathematical model and a variety of experiments. According to the analysis and experimental results, different PLZT ceramics with different sizes can produce different driving voltage and deformation of the actuator. And as the length of the torsion beam increases or the width of the torsion beam decreases, the deformation increases while the driving voltage remains the same. The driving performance is better when the copper foil attached to the right end of the upper electrode. Moreover, when the area of copper foil decreases or the distance between electrodes increases, the driving voltage increases while the change of deformation is determined by driving voltage, area and distance between electrodes. Therefore, the analysis of the influence factors can not only explore their influence on driving performance, but also provide a theoretical basis for the practical application of opto-electrostatic hybrid driving torsion actuator based on PLZT ceramic.
The coupled thickness-twist and face-shear vibrations of the lateral-field-excitation (LFE) two-unit resonator array are analyzed, and the frequency interference and shift of LFE resonator arrays are both studied. Different from most of the quartz resonator arrays based on thickness-field-excitation, the resonator array in this study operates with LFE generated by a pair of electrodes on the top surface of the resonator. By using Mindlin's first-order theory of piezoelectric plates, the electrically forced vibrations are analyzed. The effects of various structural parameters on the frequency interference and shift are examined; furthermore, the corresponding mechanisms are discussed. Varying trends of the frequency interference and shift with various structural parameters are verified by the finite element method. The results are crucial for avoiding frequency interferences between two adjacent units in parameter design of the resonator array operating on LFE.
In this study, lateral-field-excitation (LFE) bulk acoustic wave sensors based on the structure ordered Ca3TaGa3Si2O14 (CTGS) crystal are investigated. It is found that LFE devices using (yxl)-6° CTGS crystal can operate with the pseudo-LFE mode. The impedance characteristics and sensitivities of the devices are measured and compared with the LFE devices based on structure disordered langasite (LGS) crystal. The experimental results show that the CTGS LFE sensor can achieve higher Q-factors than the LGS LFE sensor, which indicates that the former has higher frequency-stability. In addition, the CTGS LFE sensor is nearly 2 times more sensitive to both liquid conductivity and permittivity changes compared to the LGS LFE sensor. For liquid acoustic viscosity changes, the CTGS LFE sensor is approximately 1.3 times more sensitive than the latter. In some chemical and biological analysis process, mechanical and electrical property changes of analytes need to be measured simultaneously, therefore the LFE sensors based on the structure ordered CTGS crystal have a good potential for use in liquid-phase sensing of chemical and biological systems.