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81.
This paper is concerned with the optimum design and sensitivity analysis methods of piezoelectric intelligent trusses on the
structural stiffness and free-vibration frequency. On the basis of the finite element method and taking into account the mechanical-electric
coupling effect under electric load and mechanical load, the computational formula of sensitivities of structural displacement
and free-vibration frequency with respect to the size and shape design variables are proposed. A new kind of design variable
of the electric voltage and the calculating method of displacement sensitivity with respect to the electric voltage variable
is presented. The new method for structural deformation control by optimizing the voltages of piezoelectric active bars is
given. The numerical methods of optimum design and sensitivity analysis for piezoelectric truss structures are implemented
in JIFEX software. Numerical examples demonstrate the effectiveness of the methods and the program.
Project supported by the Special Funds for National Key Basic Research of China (No. G1999032805) and the Foundation for University
Key Teachers by the Ministry of Education of China. 相似文献
82.
Hairui Xia Jiyang Wang Lixia Li Zhigiang Zou 《Progress in Crystal Growth and Characterization of Materials》2000,40(1-4):253-261
A new series of non-ferroelectric crystals, the piezoelectric solid solution aluminium gallium orthophosphate Al1-xGaxPO4 (AGP, 0 < x < 1) system has been successfully developed by a hydrothermal method. The AGP crystal with X = 0.10 shows a phase transition temperature T−β = 587 ± 3 °C with a cell parameters A = b = 0.49386(3) and C = 1.09563(2) nm. Raman spectra including directional dispersion in AGP are similar to those from -AIPO4 and -quartz crystals, indicating all of them belong to an isomorphic family, the short-range interaction being dominant in AGP. Comparison with -AIPO4 crystals, there exists an apparent red shift of the mode frequency and a smaller TO/LO mode splitting of the E species in the AGP crystals. 相似文献
83.
An in-depth investigation is made on the problem of an arc-shaped interface insulating crack in a three-phase concentric circular
cylindrical piezoelectric composite constitutive model. An exact solution in series form is derived by employing the complex
variable method. In addition, the distribution of physical quantities such as stresses, strains, electric displacements and
electric fields in the whole field and along the interface is also presented. Explicit expressions for crack opening displacement,
jump in electric potential on the crack surface and the electro-elastic field intensity factors at the crack tips are obtained.
Specific calculations demonstrate that the convergence of the series form solution is satisfactory and that the outer phase
(composite phase) will exert a significant effect on the electro-mechanical coupling response of the composite system. Owing
to the fact that stresses and electric displacements still possess conventional inverse square root singularities, the oscillating
singularities near the crack tip under plane strain conditions will be absent and, as a result, no unphysical interpenetration
phenomenon of the two crack surfaces will occur. In conclusion, the elastic solution obtained is also based on a solid physical
foundation.
Project supported by the National Natural Science Foundation of China (No.59635140), and the Doctorate Foundation of Xi'an
Jiaotong University. 相似文献
84.
85.
Saqlain Abbas Fucai Li Zulkarnain Abbas Taufeeq Ur Rehman Abbasi Xiaotong Tu Riffat Asim Pasha 《声与振动》2021,55(1):1-18
Structural health monitoring (SHM) is recognized as an efficient tool to interpret the reliability of a wide variety of infrastructures. To identify the structural abnormality by utilizing the electromechanical coupling property of piezoelectric transducers, the electromechanical impedance (EMI) approach is preferred. However, in real-time SHM applications, the monitored structure is exposed to several varying environmental and operating conditions (EOCs). The previous study has recognized the temperature variations as one of the serious EOCs that affect the optimal performance of the damage inspection process. In this framework, an experimental setup is developed in current research to identify the presence of fatigue crack in stainless steel (304) beam using EMI approach and estimate the effect of temperature variations on the electrical impedance of the piezoelectric sensors. A regular series of experiments are executed in a controlled temperature environment (25°C–160°C) using 202 V1 Constant Temperature Drying Oven Chamber (Q/TBXR20-2005). It has been observed that the dielectric constant ε33T which is recognized as the temperature-dependent constant of PZT sensor has sufficiently influenced the electrical impedance signature. Moreover, the effective frequency shift (EFS) approach is optimized in term of significant temperature compensation for the current impedance signature of PZT sensor relative to the reference signature at the extended frequency bandwidth of the developed measurement system with better outcomes as compared to the previous literature work. Hence, the current study also deals efficiently with the critical issue of the width of the frequency band for temperature compensation based on the frequency shift in SHM. The results of the experimental study demonstrate that the proposed methodology is qualified for the damage inspection in real-time monitoring applications under the temperature variations. It is capable to exclude one of the major reasons of false fault diagnosis by compensating the consequence of elevated temperature at extended frequency bandwidth in SHM. 相似文献
86.
87.
A new configuration for compression-shear soft-recovery experiments is presented. This technique is used to investigate various failure mechanisms during dynamic multiaxial loading of an Al2O3/SiC nanocomposite and TiB2. Velocity profiles of the target surface are measured with a variable sensitivity displacement interferometer, yielding normal and transverse velocity-time histories. A dynamic shear stress of approximately 280 MPa is obtained, in the Al2O3/SiC nanocomposite, for an imposed axial stress of about 3.45 GPa on a 540 m thick sample. This dynamic shear stress is well below the value predicted by elastic wave propagation theory. This could be the result of stress-induced damage and inelasticity in the bulk of the sample or inelasticity on the sample surface due to frictional sliding. To gain further insight into the possible failure mechanisms, an investigation of compression-shear recovery techniques, with simultaneous trapping of longitudinal and lateral release waves, is conducted. 相似文献
88.
Functionally graded piezoelectric cantilever beam under load 总被引:3,自引:0,他引:3
Summary In the present paper, the problem of a functionally graded piezoelectric cantilever beam subjected to different loadings is studied. The piezoelectric beam is characterized by continuously graded properties for one elastic parameter and the material density. A pair of stress and induction functions in the form of polynomials is proposed and determined. Based on these functions, a set of analytical solutions for the beam subjected to different loadings is obtained. As particular cases, series of solutions for some canonical problems can be directly obtained from the solutions of the present paper, such as for the problems of a piezoelectric cantilever beam with constant body force or without body forces, etc.This research work is supported by the National Natural Science Foundation of China (50272003). Support was also given by the Teaching and Research Award Fund for Outstanding Young Teachers in Higher Education Institutions of MOE, P.R.C. 相似文献
89.
90.
The gelation of a ceramic precursor, zirconium alkoxide, has been studied using dynamic oscillatory measurements. The gelation time is controlled by varying the concentrations of zirconium propoxide, hydrolysis with water, and acetylacetone concentration which acts as a chelating ligand. Gelation times were varied from minutes to months. The gelation time varied with zirconium concentration to the –10 power, hydrolysis to the –7 power, and ligand concentration of the –17 power. The sol-gel transition was monitored using the criteria of Winter in which GG
n
and tan () = tan
. It is shown that the use of multiple superimposed sinusoidal waves to simultaneously measure the moduli at several frequencies is faster than using individual frequency sweep experiments. The selection of rate and strain criteria for brittle network gels is discussed in detail. 相似文献