Analysis of the couplant influence on the ultrasonic thickness measurement of the steel grade S355J0

The ultrasonic thickness measurement is the most commonly performed technique as a part of quality management of systems and constructions. The paper carries out a study of the couplant impact on the wall thickness ultrasonic measurement results. Experimental samples are made from the steel grade S355J0. By performing a theoretical and experimental analysis, it estimates that there exists a significant effect of the particular parameters of the ultrasound transducer, the couplants type and their interactions on the thickness measurement results. An experiment scheme and the appropriate methodology for experimental results analyses create the preconditions for the assessment of the influence of the couplant type, material thickness and the parameters of ultrasound probe to the measurement uncertainty.     

Ultrasonic couplants for acoustic microscopy of low speed materials

A method is presented for estimating the compression wave velocities of organic fluids, based only on their density and molecular properties. The method is applied to a search for very low-speed ultrasonic couplants, suitable for 250 MHz acoustic microscopy studies of epoxy materials. Experimental measurements confirmed that acoustic velocity could be predicted within 3% for simple fluorine-containing organic compounds, and within 10% for those with a more complex molecular structure. The compound 2-dichloropentafluoropropane (C(3 )HCl(2)F(5)), with a compression wave velocity of C(L)=638 m/s and acceptably low attenuation coefficient, was identified as a good coupling agent for acoustic microscopy studies of low speed materials.     

Portable Automated Radio-Frequency Scanner for Non-destructive Testing of Carbon-Fibre-Reinforced Polymer Composites

A portable automated scanner for non-destructive testing of carbon-fibre-reinforced polymer (CFRP) composites has been developed. Measurement head has been equipped with an array of newly developed radio-frequency (RF) inductive sensors mounted on a flexible arm, which allows the measurement of curved CFRP samples. The scanner is also equipped with vacuum sucks providing mechanical stability. RF sensors operate in a frequency range spanning from 10 up to 300 MHz, where the largest sensitivity to defects buried below the front CFRP surface is expected. Unlike to ultrasonic testing, which will be used for reference, the proposed technique does not require additional couplants. Moreover, negligible cost and high repeatability of inductive sensors allows developing large scanning arrays, thus, substantially speeding up the measurements of large surfaces. The objective will be to present the results of an extensive measurement campaign undertaken for both planar and curved large CFRP samples, pointing out major achievements and potential challenges that still have to be addressed.     

超声治疗中耦合液对声聚焦影响的研究

本文推导了凹球面聚焦换能器产生的声波经耦合液进入软组织后的声场计算公式，并对不同耦合液，耦合层厚度，温度对声聚焦的影响进行了研究，得到一一些对超声热疗具有指导意义的结果。     

A Method for the Verification of Wire Crimp Compression Using Ultrasonic Inspection

The development of a new ultrasonic measurement technique to assess wire crimp terminations is discussed. The amplitude change of a compressional ultrasonic wave propagating at right angles to the wire axis and through the junction of a crimp termination is shown to correlate with the results of a destructive pull test. The case of incomplete compression of crimped connections is ultrasonically tested, and the results are correlated with pull tests. Results show that the ultrasonic measurement technique consistently predicts good crimps when the ultrasonic transmission is above a certain threshold amplitude level. A quantitative measure of the quality of the crimped connection based on the ultrasonic energy transmitted is shown to respond accurately to crimp quality. A wave propagation model, describes the compressional ultrasonic wave propagation through the junction during the crimping process. This model is in agreement within 6% of the ultrasonic measurements. A prototype instrument for applying this technique while wire crimps are installed is also presented. The instrument is based on a two-jaw type crimp tool suitable for butt-splice type connections. A comparison of the results of two different instruments is presented and shows reproducibility between instruments within a 95% confidence bound.     

超声波化学反应器的温度场有限元模拟

文章基于有限元方法建立了超声波化学反应器的温度场模拟方法,并以超声波化学反应器内引发的苯乙烯分散聚合反应为例,利用ANSYS软件对超声波输出功率为400W时,不同时刻反应介质的温度场分布进行了模拟,研究结果表明超声波化学反应器内引发的分散聚合反应是分区域分阶段逐步进行的。     

Machining of Engineering Ceramics by Ultrasonic Vibration Assisted EDM Method

Ultrasonic vibration assisted EDM was performed by using an ultrasonic machine tool with a d.c. power supply, with its positive and negative poles connected to the workpiece and the tool electrode, respectively. The pulse discharge is produced by the relative motion between the tool electrode and the workpiece. In the working process of this combined technology, ultrasonic machining and EDM are complementary techniques. Experimental results show that the material removal rate is a little more than just the sum of ultrasonic machining and EDM, while surface roughness is about the same as that for ultrasonic machining.     

A new mechanism of ultrasonic absorption in aqueous solutions of rigid macromolecules

The temperature- and frequency-dependences of the ultrasonic absorption in lyotropic liquid crystals of rod-like FD virus particles have been measured with the ultrasonic beam being parallel or perpendicular to the rod axis. The experimental results show a strongly anisotropic ultrasonic absorption in the lyotropic liquid crystals, which varies with temperature exactly as the shear viscosity of water. Experimental results are in good agreement with the following model for the absorption process. The authors believe that the absorption arises from differential flow of water between the relatively long and rigid rod-like macromolecules. This mechanism of ultrasonic absorption becomes dominant for frequencies of 1-100 MHz. The validity of this mechanism is, however, not restricted to the special lyotropic crystals discussed here. Instead, this absorption process is expected to be important also for other macromolecular solutions whenever the dissolved macromolecular objects have a sufficiently large linear dimension in the direction parallel to the sound beam.     

超声振动辅助单晶硅划片的锯切力研究

采用金刚石超薄锯片对单晶硅划片的工艺会在划片时产生较大锯切力,从而导致较大的崩边损伤。而旋转超声辅助加工由于超声振动的作用可以减小加工时所产的切削力,同时获得较好的加工精度,越来越广泛地应用于硬脆材料的加工中。为了验证超声辅助对单晶硅划片中锯切力的作用,在实验中将超声振动添加到锯片上,使其产生径向的振动来完成对单晶硅的划片。并通过对比有超声振动辅助与无超声振动辅助的单晶硅划片的锯切力,对超声振动辅助划片中锯切力的特点进行分析。实验结果表明,超声辅助划片所产生的锯切力比无超声辅助划片所产生的锯切力小,说明超声振动的添加可以降低锯切力。同时在超声划片中产生的崩边要小于非超声加工条件下的崩边情况,说明超声振动降低锯切力可抑制硅片的崩边。     

基于声功率的液体中大功率超声场的评价方法

为解决超声清洗中超声设备性能的评价,以及工程应用中超声强度的选取和控制问题,提出了一种根据声功率大小来测定声场强度的评价方法。制作了一个专门的超声清洗系统,并用瓦特计法测定清洗液中得到的声功率,同时用一个探头从清洗液中提取信号;通过测量清洗液中的声功率与探头输出信号电压间的关系,用数字形式来显示超声场强度。用此法对不同清洗槽进行测量,结果表明,该方法可以作为工程中大功率超声场的一种评价方法。     

Estimation of Crack Depth in Concrete Using Diffuse Ultrasound: Validation in Cracked Concrete Beams

The objective of this paper is to experimentally validate the previously proposed diffuse ultrasonic technique for measuring crack depth in concrete structures. The validation ultrasonic measurements are performed on real cracks that are formed in full scale reinforced concrete beams. Three reinforced concrete beams are designed and manufactured, and then placed under four point bending to create vertical cracks on the top surface of the beams. Diffuse ultrasonic measurements are conducted on these cracks using the procedure and instrumentation developed in the previous research. The measured crack depth results are compared with the results of side-surface visual inspection and direct stereo-microscopy measurements on cores extracted from the cracked areas. In all cases considered, the crack depths measured by the diffuse ultrasonic method appear to deviate by about 1 cm when compared to those of the core results. The possible causes of this deviation are discussed. However, the overall results show that the diffuse ultrasonic method provides consistent and reasonably accurate crack depth measurement in concrete beams.     

Turning of Microgrooves Both With and Without Aid of Ultrasonic Elliptical Vibration

Microgroove, as a form of surface texturing, has a wide array of industrial applications. However, the use of conventional methods to machine microgrooves leads to a number of problems including large burrs, high cutting forces, and poor machining quality. In this paper, ultrasonic elliptical vibration cutting is used to assist microgrooves turning on cylindrical workpiece surfaces. The elliptical locus in the cutting process is generated by a newly designed 2D resonant ultrasonic vibrator. A series of microgrooves cutting experiments without and with the ultrasonic elliptical vibration-assistance is performed to verify the effects of the ultrasonic elliptical vibrations as compared to the ordinary cutting method. The generated cutting forces, burr suppression action, and microgroove surface quality are compared for the two classes of processes. Comparison results show the effectiveness of elliptical vibration-assisted microgroove cutting in reducing cutting forces and improving microgrooves machining quality for difficult-to-cut materials. The results also show that ultrasonic elliptical vibration-assisted cutting improves the microgroove turning process with respect to cutting forces, microgroove surface roughness, and burr formation for difficult-to-cut materials.     

超声波拉伸装置的研制

将超声引入金属塑性国呀领域，设计与制造了一套超声振动拉伸装置，并在设计与制造换能器的基础上，对超声系统的性能做了测试。利用该振动装置对金属铜试件进行了拉伸试验。结果表明，该装置性能可靠。     

MEMS ultrasonic transducers for the testing of solids

Arrays of capacitive diaphragm ultrasonic transducers could potentially be used for non-destructive ultrasonic testing and structural monitoring. In this paper, we consider the efficiency of coupling of these transducers to solid media. We show that efficient coupling can be realized by using a silicone coating as a coupling medium. We present the results of experimental characterization of ultrasonic transducers coupled to solids in this way. We show that these transducers can be used with piezoelectric emitting transducers within the range from 1 to 5 MHz, and we demonstrate the use of several transducers as a phased array to determine the direction and distance of an ultrasonic source.     

基于改进时间反转法的超声导波检测系统构建

针对目前国内自主研制超声导波检测设备能力不足以及常规超声导波检测灵敏度较低等问题,构建一种基于改进时间反转法的超声导波检测系统。利用超声导波线性叠加性,单独激励时间反转信号,再线性叠加检测信号,在LabVIEW环境下,开发基于NEXTKIT信号万用仪和NI PXI-6331采集卡的超声导波时间反转检测系统。实验结果表明:纯净的时间反转信号是获得良好聚焦效果的前提,为窗宽选择提供依据,有效提高小缺陷反射回波信号幅值,为设备小型化提供可能。     

超声提取蜂胶黄酮的研究

蜂胶黄酮是蜂胶的主要活性成分,具有抗氧化、抗菌等多种功效。优化蜂胶黄酮的超声提取工艺,为蜂胶产品的开发与利用提供了理论依据。首先进行了单因素试验,研究超声功率、超声时间和乙醇浓度这三个因素分别对蜂胶黄酮提取得率的影响。在此基础上,再采用响应面法优化蜂胶黄酮的超声提取条件。研究结果表明,影响蜂胶黄酮提取得率的主次因素依次是超声时间、乙醇浓度和超声功率。当超声功率为150 W、超声时间为16 min、乙醇浓度为86%时,蜂胶黄酮提取得率实际最大可达到21.10%±0.075%(n=3)。经本实验分析可知,湖北孝感蜂胶属于蜂胶中的优等品。相比于其他超声提取蜂胶黄酮的方法,该实验的超声提取方法具有提取温度低、提取时间短的优势。     

超声波技术在检测真空系统泄漏中的应用

基于电厂真空系统泄漏是一种常见故障,因此研究一种简便、快捷、准确的检测方法是必要的.运用超声波技术研究了检测真空系统泄漏的新方法.实践表明,该方法是可行的.所给出的应用超声波技术检测真空系统泄漏的原理和检测方法是有效的.     

大功率超声清洗机研制中的一些技术问题

本文介绍了微机控制的大功率超声清洗机研制的一些技术问题，探索了单片机在功率超声中的应用，提出了大功率超声振动子的一种新的设计方法，解决了一些影响振动子性能的关键问题，对于楔形工具头的超声振动子平均振幅的测量以及与同类机型的比较成为可能，文中还给出了部分比较曲线，实际测量证明，本文所述的系统比同类进口机平均振幅提高一倍以上，对工件的清效果明显优于进口机。     

PBX代用粉体超声加载成型的实验研究

设计了PBX代用粉体超声成型装置。研究了超声波加载对含能有机复合粉末成型效果的作用,对于直径为200mm、高为60~65 mm的压坯,与相同条件下无超声压制相对比,压坯密度提高了1.79%;声速测试表明,压坯强度有一定增强;CT成像表明压坯均匀性有一定提高;压坯表面温度分布均匀,未出现局部过热现象。研究表明超声波加载技术在较大尺寸含能材料成型过程中对提高成品品质具有促进作用。     

Acoustic softening in metals during ultrasonic assisted deformation via CP-FEM

In this paper, a phenomenological crystal plasticity model is modified to account for acoustic (ultrasonic) softening effects based on the level of ultrasonic intensity supplied to single and polycrystalline metals. The material parameters are identified using the inverse modeling approach by interfacing the crystal plasticity model with an optimization tool. The proposed model is validated and verified by comparing the microstructure evolution with experimental EBSD results reported in the literature. The model is able to capture the ultrasonic softening effect and the results show that as the ultrasonic intensity increases, the plastic deformation also increases. Differences in the stress-strain response are explained based on the slip system orientation tensor (Schmidt factors) which depends upon the crystal orientation.