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1.
Singular variation property of elastic constants of piezoelectric ceramics shunted to negative capacitance 下载免费PDF全文
Piezoelectric shunt damping has been widely used in vibration suppression, sound absorption, noise elimination, etc.In such applications, the variant elastic constants of piezoelectric materials are the essential parameters that determine the performances of the systems, when piezoelectric materials are shunted to normal electrical elements, i.e., resistance,inductance and capacitance, as well as their combinations. In recent years, many researches have demonstrated that the wideband sound absorption or vibration suppression can be realized with piezoelectric materials shunted to negative capacitance. However, most systems using the negative-capacitance shunt circuits show their instabilities in the optimal condition, which are essentially caused by the singular variation properties of elastic constants of piezoelectric materials when shunted to negative capacitance. This paper aims at investigating the effects of negative-capacitance shunt circuits on elastic constants of a piezoelectric ceramic plate through theoretical analyses and experiments, which gives an rational explanation for why negative capacitance shunt circuit is prone to make structure instable. First, the relationships between the elastic constants c_(11), c_(33), c_(55) of the piezoelectric ceramic and the shunt negative capacitance are derived with the piezoelectric constitutive law theoretically. Then, an experimental setup is established to verify the theoretical results through observing the change of elastic constant c_(55) of the shunted piezoelectric plate with the variation of negative capacitance.The experimental results are in good agreement with the theoretical analyses, which reveals that the instability of the shunt damping system is essentially caused by the singular variation property of the elastic constants of piezoelectric material shunted to negative capacitance. 相似文献
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本文提出利用长度方向极化的压电材料的33模态来实现半主动减振。论文以横梁为例,通过理论分析和有限元仿真,对比研究了当压电材料分别连接31, 33两种模态对应的最佳分流电路时,压电材料两种模态在横梁的共振频率附近的减振效果。结果表明33模态比31模态具有更高的减振效率。此外,鉴于33模态存在极化长度有限的问题,仿真分析了压电材料的尺寸和位置对减振效果的影响。在此基础之上,提出了一个利用压电材料33模态的多模态减振的组合设计,对横梁的前三个模态起到了很好地减振作用。相对31模态而言,横梁的每个振动模态均有约15dB的减振提升。 相似文献
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作为重要的功能材料,压电材料已经在国民经济的多个领域里有着重要应用.随着现代工业的快速发展,特别是新能源、交通和国防工业的高速发展,功能材料的应用已经从常规使用转向极端环境下的服役.本文综述了具有高居里点的压电材料,包括钙钛矿型压电陶瓷、铋层状结构氧化物压电陶瓷、钨青铜结构压电陶瓷以及非铁电压电单晶等;介绍了其晶体结构特征和高温压电性能、最新研究进展,并列举了一系列的高温压电器件和应用,包括高温压电探测器、传感器、换能器和驱动器等.另外,本文总结了高温压电材料的热点研究问题,并展望了今后的发展方向. 相似文献
4.
Yue-Ting Zhou 《哲学杂志》2015,95(2):167-185
An exact analysis is conducted for periodic, two-dimensional (2D) contact of piezoelectric materials in contact with a rigid body with a wavy surface pressed by uniform stresses at infinity. For three cases of eigenvalue distribution, three harmonic functions automatically satisfying the periodicity conditions are carefully constructed to facilitate the derivation of the solution of the considered problem. The stresses and electric displacements are obtained as infinite series. It is found that for the full contact case, the disturbance stress and electric displacement fields remain only the first harmonic which has the slowest decay in the y-direction. The convergence behaviours of the infinite series are checked, which shows that the external loading p and different positions have a great effect on the convergence behaviours of the infinite series and 400 terms are enough to get accurate solution at each position. Numerical results are presented to justify the validity of the present derivation and show the effect of the external loading on the contact behaviours. 相似文献
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B Subramanyam 《Pramana》1995,45(3):227-234
Using Landau theory of phase transition, expressions for gyrotropic coefficients and piezoelectric coefficients are obtained
for barium titanate in the tetragonal phase. Both coefficients vanish at the ferroelectric phase transition temperature. The
piezoelectric coefficients tallied with the literature values. The attenuation coefficients for elastic waves propagating
along the principal directions in tetragonal, orthorhombic and rhombohedral phases are derived based on Landau theory. It
is predicted that there will be slight amplification for both longitudinal and transverse modes in the rhombohedral phase
at a temperature close to the rhombohedral phase transition temperature. 相似文献
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The possible lattice formation of grains of chosen material in a magnetized current carrying n-type piezoelectric semiconductor plasma has been examined. In addition to the repulsive Coulomb potential, there appears
a non-Coulombic oscillatory potential among the highly charged grains due to the strong resonant collective interaction of
the grains and the electron-acoustic mode of the host semiconductor giving rise to the possibility of the lattice formation
of grains of new materials. 相似文献
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A complete set of elastic constants C ij and piezoelectric coefficients e ij of a La3Ga5SiO14 (langasite) single crystal was determined from 5.5 to 275.5?K by resonant ultrasound spectroscopy. Unlike a conventional crystal, the elastic constants C ij of the langasite crystal showed three types of temperature dependence: (i) monotonic elastic stiffening upon cooling (C 44 and C 14); (ii) monotonic elastic softening (C 66); and (iii) a stiffening-to-softening transition below 150?K (C 11, C 12, C 13 and C 33). In addition, a strong correlation between C 66 and the piezoelectric coefficient e 11 was confirmed. Group theoretical lattice dynamics analysis revealed that the novel phenomena of elastic softening and strong correlation are explained on the basis of two types of optical mode internal displacements which have the totally symmetric A 1 and doubly degenerated E symmetries in the point group D 3. 相似文献
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The relaxor based ferroelectric (1-x)Pb(Zn(1/3)Nb(2/3))O(3)-xPbTiO(3) and (1-x)Pb(Mg(1/3)Nb(2/3))O(3)-xPbTiO(3) single crystals provided new challenges in property characterization because their extraordinarily large piezoelectric coefficients and electromechanical coupling coefficients. Large errors may occur in some of the derived material constants using conventional characterization techniques. This paper will analyze the inadequacy of the traditional characterization methods and provide some basic guidelines for properly characterizing piezoelectric materials with extremely high piezoelectric and electromechanical coupling coefficients. 相似文献
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In this paper,we analyze the stress and electric field intensity factors affected by residual surface stress for conducting cracks in piezoelectric nanomaterials.The problem is reduced to a system of non-linear singular integral equations,whose solution is determined by iteration technique.Numerical results indicate that the residual surface stress can significantly alter the crack tip fields at nanometer length scales.Due to the residual surface stress,281he electric field can produce stress around crack tip.This suggests a strong electromechanical coupling crack tip field for nanoscale piezoelectric materials.Such a finding is considerably different from the classical fracture mechanics results.A transit electric field to stress load ratio is identified,for which influences of residual surface stresses vanish.The research is useful for the applications of nanoscale piezoelectric devices. 相似文献
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《Phase Transitions》2012,85(4):345-352
Excitation of solitary waves and their propagation in surface-stabilized ferroelectric liquid crystal cells under alternating external electric field is investigated both theoretically and experimentally. The effect of solitary waves on electro-optic response spectra is analyzed for different amplitudes of applied fields, temperatures, and sample thicknesses. It is shown that solitons can only be excited within narrow ranges of frequencies of the sufficiently strong electric fields. The minimal frequency, at which soliton waves appear in ferroelectric smectic liquid crystals, is found to be related to the material constants of these systems. It is proved that measuring this threshold frequency gives the possibility to determine one of the material parameters, if the others are known. In this way, the intra-smectic-layer elastic constant is found for systems with the chevron geometry. 相似文献
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利用基于密度泛函理论的CASTEP软件构建Mg8Sn4-xMx(M=Al、Cu;x=0、1或2)晶体结构模型,采用第一性原理计算其晶格常数、结构稳定性和弹性常数,并分析不同量的M原子固溶于Mg2Sn后体系的电子特性、弹性性能和本征硬度.计算结果表明,M原子能自发固溶于Mg2Sn相,且所得Mg8Sn4-xMx(x=1或2)晶体结构均可稳定存在;当2个M原子固溶于Mg2Sn时,使其晶体结构由立方晶系转变为四方晶系.态密度分析表明,M原子固溶后体系原子存在明显轨道杂化现象,表现出较强的共价键,增加M原子固溶量不会改变各原子对态密度的贡献规律,但会提高该原子对电子对态密度的贡献度.弹性性能和本征硬度分析表明:Mg2Sn中固溶M原子后,体系力学性能仍稳定,增加M原子固溶量,体系硬度逐渐降低,韧塑性不断提高,即M原子固溶量增加能提升体系的... 相似文献
16.
The structural,elastic,and electronic properties of Zr_x Nb_(1-x)C alloys from first principle calculations 下载免费PDF全文
The structural,elastic,electronic,and thermodynamic properties of Zr x Nb1-x C alloys are investigated using the first principles method based on the density functional theory.The results show that the structural properties of Zr x Nb1-x C alloys vary continuously with the increase of Zr composition.The alloy possesses both the highest shear modulus(215 GPa)and a higher bulk modulus(294 GPa),with a Zr composition of 0.21.Meanwhile,the Zr0.21Nb0.79C alloy shows metallic conductivity based on the analysis of the density of states.In addition,the thermodynamic stability of the designed alloys is estimated using the calculated enthalpy of mixing. 相似文献
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采用含时哈特里-福克-博戈留波夫近似研究球对称铷原子玻色-爱因斯坦凝聚中单极子模的朗道阻尼和频移,并用现有实验和数值模拟研究的粒子数和囚禁频率参量,解析计算了阻尼系数和频移大小及其它们的温度依赖。计算中,考虑元激发的实际弛豫及其各弛豫间的正交关系以获得阻尼和频移计算公式,把基态波函数取为高斯分布函数的一级近似以消除三模耦合矩阵元的发散。我们的计算结果与数值模拟结果和实验结果分别进行直接和间接地对比,讨论和说明了我们理论方法的合理性。 相似文献
19.
Landau damping and frequency-shift of a quadrupole mode in a disc-shaped rubidium Bose–Einstein condensate 下载免费PDF全文
The damping and frequency-shift in Landau mechanism of a quadrupole mode in a disc-shaped rubidium Bose–Einstein condensate are investigated by using the Hartree–Fock–Bogoliubov approximation. The practical relaxations of the elementary excitations and the orthometric relation among them are taken into account to obtain advisable calculation formula for damping as well as frequency-shift. The first approximation of Gaussian distribution function is employed for the ground-state wavefunction to suitably eliminate the divergence of the analytic three-mode coupling matrix elements.According to these methods, both Landau damping rate and frequency-shift of the quadrupole mode are analytically calculated. In addition, all the theoretical results agree with the experimental ones. 相似文献
20.
采用含时哈特里-福克-博戈留波夫近似研究球对称铷原子玻色-爱因斯坦凝聚中单极子模的朗道阻尼和频移,并用现有实验和数值模拟研究的粒子数和囚禁频率参量,解析计算了阻尼系数和频移大小及其它们的温度依赖.计算中,考虑元激发的实际弛豫及其各弛豫间的正交关系以获得阻尼和频移计算公式,把基态波函数取为高斯分布函数的一级近似以消除三模耦合矩阵元的发散.我们的计算结果与数值模拟结果和实验结果分别进行直接和间接地对比,讨论和说明了我们理论方法的合理性. 相似文献