HIGH-FREQUENCY VIBRATIONS OF CORRUGATED CYLINDRICAL PIEZOELECTRIC SHELLS

Coupled extensional and flexural cylindrical vibrations of a corrugated cylindrical piezoelectric shell consisting of multiple pieces of circular cylindrical surfaces smoothly connected along their generatrix are studied. To validate the results for the case of relatively thick shells or equivalently high-frequency modes with short wavelengths, existing analysis is extended by considering shear deformation and rotatory inertia. An analytical solution is obtained. Based on the solution, resonant frequencies and mode shapes are calculated.     

电涡流传感器所受电磁力研究

本文研究电涡流传感器的探测线圈与电涡流之间的电磁作用力。理论计算与测量结果表明,对于某些应用电涡流传感器的灵敏装置而言,这个力的影响是不能忽略的。     

结构参数对偶极声波换能器谐振频率的影响

偶极横波远探测技术在我国复杂地质结的构油气勘探中具有十分广阔的应用前景。换能器的工作频率直接影响声波测井的探测深度。本文对正交偶极声波测井换能器弯曲模态的谐振频率进行了解析计算,并利用有限元方法研究了其结构参数对谐振频率的影响。计算结果表明:当压电陶瓷片的长度增加时,换能器一阶谐振频率先降低后升高,三阶谐振频率先升高再降低之后又上升;当金属基片厚度增加时,换能器一阶与三阶谐振频率均升高;当压电陶瓷片厚度增加时,换能器谐振频率的变化方向与幅度还与压电陶瓷片长度等其他参数相关,有可能升高或降低。     

Influence of the Geometry of a Piezotransformer Transducer on Its Electric Potential During Electroelastic Vibrations of a Piezoceramic Disk

The resonant radial vibrations of a thin piezoceramic disk with solid electrodes and thickness polarization are considered as an example to study the influence of the geometry of piezotransformer transducers on their electric potentials and the mutual influence of neighboring transducers__________Translated from Prikladnaya Mekhanika, Vol. 41, No. 2, pp. 75–80, February 2005.     

电涡流传感器温度漂移的自动补偿

本文分析了影响电涡流传感器温度漂移的主要因素，经过理论分析提出一种减少温度漂移行之有效的方法，实践结果表明此方法有很好的温度漂移自由补偿效果。     

Evolution of the planar vibrations of a rectangular piezoceramic plate as its aspect ratio is changed

The evolution of the planar vibrations of a rectangular piezoceramic plate as its aspect ratio is changed starting with 1 is studied. Experimental data are obtained using an integrated technique based on Meson’s circuit, Onoe’s circuit, and a piezotransformer transducer. As the aspect ratio increases (square plate becomes rectangular), the intensity of electromagnetic vibrations rapidly increases at the first longitudinal resonance and gradually decreases in the first radial mode. When the aspect ratio is changed so that the length of one of the plate sides remains constant, the resonant frequencies of all vibration modes change too __________ Translated from Prikladnaya Mekhanika, Vol. 43, No. 7, pp. 98–106, July 2007.     

Review of air-coupled ultrasonic materials characterization

This article presents a review of air-coupled ultrasonics employed in the characterization or nondestructive inspection of industrial materials. Developments in air-coupled transduction and electronics are briefly treated, although the emphasis here is on methods of characterization and inspection, and in overcoming limitations inherent in the use of such a tenuous sound coupling medium as air. The role of Lamb waves in plate characterization is covered, including the use of air-coupled acoustic beams to measure the elastic and/or viscoelastic properties of a material. Air-coupled acoustic detection, when other methods are employed to generate high-amplitude sound beams is also reviewed. Applications to civil engineering, acoustic tomography, and the characterization of both paper and wood are dealt with here. A brief summary of developments in air-coupled acoustic arrays and the application of air-coupled methods in nonlinear ultrasonics complete the review. In particular, the work of Professor Bernard Hosten and his collaborators at Bordeaux is carefully examined.     

Coded waveforms for optimised air-coupled ultrasonic nondestructive evaluation

This paper investigates various types of coded waveforms that could be used for air-coupled ultrasound, using a pulse compression approach to signal processing. These are needed because of the low signal-to-noise ratios that are found in many air-coupled ultrasonic nondestructive evaluation measurements, due to the large acoustic mismatch between air and many solid materials. The various waveforms, including both swept-frequency signals and those with binary modulation, are described, and their performance in the presence of noise is compared. It is shown that the optimum choice of modulation signal depends on the bandwidth available and the type of measurement being made.     

Cavitation field from a horn—A new model

The cavitation field from a horn-type transducer is experimentally probed by the optical method.Based on these observations,we propose a model of the field which hypothesizes that most violent caviation bubbles originate from the vibrating surface and there-from fast drift to the near liquid region.These bubbles are chiefly responsible for the practical applications of cavitation for a large power input to the transducer.During migration they become weakened.Cavitation bubbles are also produced in the liqui...     

混凝土框架结构内力测量传感器研制

研制了一种可用于混凝土结构试验中测量柱底截面轴向力、剪力和弯矩的内力测量传感器。该传感器主要由加载板、基座、4根竖向测力杆和2根水平测力杆组成。使用时,柱底截面的内力通过加载板传递给6根测力杆,根据6根测力杆的结果,通过力平衡方程可以计算实际加载的轴向力、剪力和弯矩的大小。对该传感器进行了4种工况下的标定试验。结果表明,传感器的测量误差满足框架结构内力测量精度要求。将该传感器应用到单层两跨的钢筋混凝土框架推覆试验中,获得了整个试验过程中构件的内力时程。