Acoustic load dependency of electroacoustic efficiency in the electrostrictive ultrasonic transducer and acoustical matching

The acoustic load dependency of the electroacoustic efficiency in the electrostrictive transducer is derived theoretically and measured experimentally. The results show that there is an optimum acoustic load resistance which maximizes the electroacoustic efficiency. It is considered reasonable to cite the optimum condition as ‘acoustical matching’ of the transducer to the acoustic load.     

High-frequency broadband transducers of ultrasonic oscillations

The amplitude-frequency responses (AFRs) of ultrasonic oscillation transducers based on piezoelectric lithium iodate crystals of hexagonal modification and on magnetic soft ferrite powders are experimentally studied. The possibility to control the efficiency of magnetostriction powder transducers (MPTs) by variation in the value and orientation of the external magnetic field is shown. Results of measurements of the transformation efficiency for ferrites of various chemical compositions are presented.     

Superimposed ultrasonic oscillations in compression tests of aluminium

The application of ultrasonics in metal forming applications has been shown to reduce the forming load significantly in many research studies. The load reduction has been related to the stress superposition effect, rise in temperature and change in the friction condition between the specimen and die interfaces. This paper reports an investigation into the effects of superimposed ultrasonic oscillation of the die in compression tests on aluminium specimens. In particular, a finite element model is developed to simulate uniaxial compression and to model the effects of a change in the friction boundary condition when ultrasonic excitation is applied to the lower platen. The model predictions of the stress-strain relationship can be compared with test data to provide some insights into the effects of the interfacial condition. The paper shows how the analysis of the test data, combined with finite element models of ultrasonic compression test simulations, allows some initial conclusions to be drawn regarding the influence of the interfacial friction during ultrasonic compression.     

Giant quantum oscillations of ultrasonic attenuation in tin

We report giant quantum oscillations from both of the 3δ orbits in tin, which we interpret as normal oscillations from orbit 3δ², which does not suffer breakdown, and the recently predicted magnetic breakdown, giant quantum oscillations from orbit 3δ¹.     

The effect of small-amplitude load oscillations on the nanocontact characteristics of materials in nanoindentation

A continuous stiffness measurement method allowing one to obtain physical-mechamical characteristics of materials in the process of indentation during gradually increasing loading has been scrutinized. The limits of applicability of this approach depend on the testing conditions at which the additional smallamplitude oscillations exert no influence on the mechanics, kinetics, and plastic strain of material being in contact with the indenter. As is shown by taking as examples specimens with amorphous structure, and fcc and bcc lattices, various techniques for determining the nanocontact characteristics of materials are different by their sensitivity to small-amplitude load oscillations. The oscillation amplitudes and the indentation depth ranges where one can neglect the oscillation effects have been evaluated. The impacts of the oscillations on the behavior of the contact (local) characteristics of the studied materials in supercritical modes have been established.     

抗性负载超声变幅杆振动特性研究

在负载为纯力抗的状况下，利用纵振型变幅杆等效四端网络，对频率方程和放大系数进行了研究．得到了三类常用变幅杆频率方程和放大系数的表达式；并通过MATLAB编程，分别绘制了三类变幅杆共振频率及放大系数随负载变化的曲线图．这将对超声变幅杆的研究和设计提供一定的理论依据．     

The transfer of ultrasonic energy in the diffraction technique for crack sizing

During the past five years a programme of work has been carried out at the Harwell NDT Centre concerned with the use of scattered or diffracted ultrasound in the sizing of defects. The progress made in this direction and some of the possible lines of further research have been indicated in other papers.^1–3 This diffraction technique has been evaluated on a number of fatigue cracked specimens and it has been found that accuracies in crack sizing consistently better than $\text{1}\text{2}$ mm have been achieved. The technique is thus thought to be on the verge of application to practical ndt problems.The basis of the sizing technique is the recognition and subsequent timing of various discrete ultrasonic pulses, as will be outlined later. The scope of the technique thus depends on these signals remaining both well separated and large enough to be resolved in a wide range of examination geometries. The purpose of the present paper is to consider the mechanisms by which two of the ultrasonic pulses of importance in the diffraction technique are produced. In this connection the current theoretical situation is reviewed and this is compared, where appropriate, with experimental measurements taken during the period of this work.     

A transfer efficiency model for ultrasound mediated drug/gene transferring into cells

Ultrasound is a very promising technology to mediated drug/gene transferring into cells. However the relations between cell experimental conditions and results have been still unknown. It seriously impeded the development of the technology. In the article, a transfer efficiency model for ultrasound mediated drug/gene transferring into cells in stable cavitation was constructed. To testify the model, the numerical results were compared with the cell experimental data from six literatures in the entirely different experimental conditions. The numerical results fit the cell experimental data well. Despite simplifications and limitations, the model for the first time established the relationship between the cell experimental results about transfer efficiency and the conditions including ultrasound, microbubble and cells in stable cavitation.     

Effect of ultrasonic oscillations on the fluidity of heavy oil products at low temperatures

We develop a laboratory setup to estimate the force of rotation of a metal branch pipe in a viscoelastic medium. We show that 2-min action of shearing ultrasonic oscillations (frequency, 32.5 kHz; specific power, no more than 0.008 W/cm²) reduces by 17% the static limit of fluidity brought to an initial temperature of ì-100 fuel oil cooled to −15°C in the wall layer of a rotating branch pipe. We obtain a linear regression dependence between the ratio of the threshold force of the onset of branch pipe motion to the consumption current of the ultrasonic transducer and the fuel temperature.     

Study of the influence of thermal history on the load transfer efficiency and fibre failure in carbon/polypropylene microcomposites using Raman spectroscopy

The influence of thermal history on the interfacial load transfer efficiency and fibre failure in carbon/polypropylene microcomposites has been studied using Micro Raman spectroscopy. Microcomposites were manufactured by cooling from the melt at different constant cooling rates or isothermally crystallized. Thermal residual strains were measured during and after manufacture of the microcomposites. The residual strains resulted in compressive fibre failure. Based on the experimental data, interfacial load transfer efficiency was determined quantitatively for the different cooling procedures. Results indicate that thermal history has a very large influence on the interfacial load transfer efficiency of the microcomposites. This was shown to be due to the influence of thermal history on transcrystallinity and interfacial residual stresses. A transcrystalline interphase provides a more effective load transfer compared to the non-transcrystalline interphase. Furthermore, decreasing cooling rates leads to an increase in load transfer efficiency due to increased transcrystallinity and higher crystallization temperature resulting in higher interfacial stresses.     

Ultrasound field distribution and ultrasonic oxidation desulfurization efficiency

Ultrasonic oxidation desulfurization (UODS) has been considered a promising method for deeply desulfurization technology since it can be carried out using mild conditions. During the last few decades many experimental investigations have been carried out on optimizing the reaction condition such as ultrasonic irradiation time, oxidizing reagents amount, kind of organic acid and so on. But limited work has been reported on the influence of the ultrasonic cavitation field distribution. In this work, the relative intensity of the cavitation events has been measured with the aluminum foil erosion method in a commonly used ultrasonic cleaning vessel both in horizontal and vertical directions. The aluminum foil erosion image was then collected into computer by a scanner. In addition, the image processing program of MATLAB software was used to pretreat the erosion image and find out the positions of the erosion points so that the ratio of the erosion area to the entire area can be calculated which helped to quantify the measurement result since the erosion ratios was the representation of the cavitation intensity. The desulfurization efficiency was then measured in different position of the vessel. The results match well with the cavitation field distribution results which indicate that the cavitation field distribution can be used to guide the UODS process.     

松孔镀铬层的高效超声珩磨

作者使用自行研制的立式超声珩磨装置对钢质薄壁气缸套松孔镀铬层进行了超声珩磨试验。试验结果使用人造金刚石和ＣＢＮ油石时，与普通珩磨相比，超声珩磨镀铬层可提高珩磨效率１４－５９倍，表面粗度Ｒａ可达０．２－１．２７μｍ，加工精度可达ＩＴ６－ＩＴ７。     

Characterization of ultrasonic imaging systems using transfer functions

The transfer functions for focussed and defocussed, coherent and confocal optical imaging systems have been applied to the equivalent ultrasonic imaging systems. The transfer functions with varying degrees of defocus were calculated to show the defocus effects for ultrasonic imaging systems. Assuming that the acoustic waves are reflected perfectly on the surface of the step edge, the theoretical line-scans for small amplitude signals across a step edge, with various degrees of defocus, were generated. The first derivative of the line-scan for a step edge is shown theoretically to yield the same impulse response as that calculated using the inverse Fourier transform applied to the original transfer function. These results show how the real and imaginary parts of the transfer functions contribute to ultrasonic image formation. A method for the experimental determination of the impulse response, and the transfer functions for the characterization of an ultrasonic imaging system, such as an acoustic microscope, is provided.     

The influences of ultrasonic on embedding nanoparticles into porous fabric materials

The feasibility of embedding 40 nm ZnO particles into porous materials by using ultrasonic and its influence factors were studied in this paper. Through investigations, it is proved that the higher the concentration of nanoparticle suspension is, the higher the weight of embedding percentage (EPW) is. However, the increasing trend of EPW will minish quickly when the concentration exceeds 1%. In addition, the longer the process time of ultrasonic is, the higher EPW is. EPW is always higher when the distance between film and ultrasonic transducer is λ/2 and 3λ/2, and lower when the distance is 1 λ and 2 λ. For 40 nm ZnO particles, EPW of the film effected by ultrasonic with the frequency of 42 kHz reaches the maximum.     

An investigation into the ultrasonic treatment of polluted solids

Granular pieces of brick impregnated with copper oxide were used as a model for contaminated soil. Washing this model substrate by passing water across the substrate on an ultrasonically shaken tray irradiation afforded a 40% reduction in copper content. This was compared with only a 6% reduction when the sample was treated under otherwise identical conditions but using a tray shaken conventionally. The majority of the copper was removed as a result of the removal of surface materials which were more heavily contaminated with the copper oxide.