High-accuracy standard specimens for the line-focus-beam ultrasonic material characterization system

We prepared standard specimens for the line-focus-beam ultrasonic material characterization system to obtain absolute values of the propagation characteristics (phase velocity and attenuation) of leaky surface acoustic waves (LSAWs). The characterization system is very useful for evaluating and analyzing specimen surfaces. The calibration accuracy of these acoustic parameters depends on the accuracy of acoustical physical constants (elastic constants, piezoelectric constants, dielectric constants, and density) determined for standard specimens. In this paper, we developed substrates of non piezoelectric single crystals (viz., gadolinium gallium garnet [GGG], Si, and Ge) and an isotropic solid (synthetic silica [SiO₂] glass) as standard specimens. These specimens can cover the phase velocity range of 2600 to 5100 m/s for Rayleigh-type LSAWs. To determine the elastic constants with high accuracy, we measured velocities by the complex-mode measurement method and corrected diffraction effects. Measurements of bulk acoustic properties (bulk wave velocity and density) were conducted around 23°C, and bulk wave velocities were obtained with an accuracy of within ±0.004%. We clearly detected differences in acoustic properties by comparing the obtained results with the previously published values; the differences were considered to be due to differences of the specimens used. We also detected differences in acoustic properties among four SiO₂ substrates produced by different manufacturers     

Evaluation method of TiO/sub 2/-SiO/sub 2/ ultra-low-expansion glasses with periodic striae using the LFB ultrasonic material characterization system

Experimental procedures and standard specimens for characterizing and evaluating TiO/sub 2/-SiO/sub 2/ ultralow expansion glasses with periodic striae using the line-focus-beam (LFB) ultrasonic material characterization system are discussed. Two types of specimens were prepared, with specimen surfaces parallel and perpendicular to the striae plane using two different grades of glass ingots. The inhomogeneities of each of the specimens were evaluated at 225 MHz. It was clarified that parallel specimens are useful for accurately measuring velocity variations of leaky surface acoustic waves (LSAWs) excited on a water-loaded specimen surface associated with the striae. Perpendicular specimens are useful for obtaining periodicities in the striae for LSAW propagation perpendicular to the striae plane on a surface and for precisely measuring averaged velocities for LSAW propagation parallel to the striae plane. The standard velocity of Rayleigh-type LSAWs traveling parallel to the striae plane for the perpendicular specimens was numerically calculated using the measured velocities of longitudinal and shear waves and density. Consequently, a reliable standard specimen with an LSAW velocity of 3308.18 /spl plusmn/ 0.35 m/s at 23/spl deg/C and its temperature coefficient of 0.39 (m/s)//spl deg/C was obtained for a TiO/sub 2/-SiO/sub 2/ glass with a TiO/sub 2/ concentration of 7.09 wt%. A basis for the striae analysis using this ultrasonic method was established.     

Evaluation method of TiO2-SiO2 ultra-low-expansion glasses with periodic striae using the LFB ultrasonic material characterization system.

Experimental procedures and standard specimens for characterizing and evaluating TiO2-SiO2 ultra-low expansion glasses with periodic striae using the line-focus-beam (LFB) ultrasonic material characterization system are discussed. Two types of specimens were prepared, with specimen surfaces parallel and perpendicular to the striae plane using two different grades of glass ingots. The inhomogeneities of each of the specimens were evaluated at 225 MHz. It was clarified that parallel specimens are useful for accurately measuring velocity variations of leaky surface acoustic waves (LSAWs) excited on a water-loaded specimen surface associated with the striae. Perpendicular specimens are useful for obtaining periodicities in the striae for LSAW propagation perpendicular to the striae plane on a surface and for precisely measuring averaged velocities for LSAW propagation parallel to the striae plane. The standard velocity of Rayleigh-type LSAWs traveling parallel to the striae plane for the perpendicular specimens was numerically calculated using the measured velocities of longitudinal and shear waves and density. Consequently, a reliable standard specimen with an LSAW velocity of 3308.18 +/- 0.35 m/s at 23 degrees C and its temperature coefficient of 0.39 (m/s)/degrees C was obtained for a TiO2-SiO2 glass with a TiO2 concentration of 7.09 wt%. A basis for the striae analysis using this ultrasonic method was established.     

Characterization of laser hardened steels by laser induced ultrasonic surface waves

Ultrasonic surface waves are suitable for the characterization of surface hardened materials. This is shown on laser hardened turbine blades. The martensitic microstructure within the surface layer of surface hardened steels has a lower surface wave propagation velocity than the annealed or normalized substrate material. Because the propagation velocity depends on the ratio of layer thickness to wavelengthd/, its measurement allows the determination of the hardening depth. If the surface wave frequency is high enough, the surface wave propagates mainly within the hardened layer. A correlation of the surface wave velocity to the surface hardness has been found. Because the variation of the surface velocity in hardened steels is small, a high measurement accuracy is necessary to obtain the interesting hardening parameters with sufficient certainty. Therefore, a measuring arrangement has been developed where laser pulses, guided by optical fibers to the surface hardened structure, generate simultaneously surface wave pulses at two different positions. The two ultrasonic pulses are received by a piezoelectric transducer. The surface wave velocity is obtained from the time delay between these pulses which is determined by the cross-correlation method. To evaluate simultaneously surface waves with different penetration depths from the same signal acquisition, digital filtering has been used in connection with the cross-correlation.     

一个高温持久/蠕变测控温及试验管理系统

介绍了采用测控分开形式对近百台五六十年代制造的高温持久/蠕变试验机进行测控温系统改造的工作.改造后的控温系统创造了不同热电偶数量(测控温共偶,1～3支)都可实现对试样温度和梯度的稳定控制,系统具有较强抗外界干扰能力,而且控温过程中对电网无干扰.测量系统测量误差≤±0.1%FS.测控温系统采取单炉闭环控制、30台集中巡回...     

细管道中流速的超声相关法测量

针对应用常规超声波方法测量极小管径(5 mm及以下)中流体速度的精度较低问题,文章应用相关函数法精确测量时延,降低噪声对测量结果的影响,提高了极小管径中流体速度的测量精度.首先,利用COMSOLMultiphysics有限元仿真软件建立管道传输模型,然后将被顺、逆水流影响后的超声波波形数据分别导入Matlab软件,用插...     

超声法测量螺栓轴向力的测量准确度分析

用超声法测量螺栓轴向力时,测量结果受多因素的复杂关联影响,这导致测量准确度偏低。为实现短螺栓(M8×37)紧固后轴向力值的准确测量,针对超声法测量螺栓轴向力问题进行理论分析,构建测量误差模型;对测量中的若干要素(如温度、探头位置与耦合状态等)进行分离、控制,分两阶段开展试验,研究多要素对测量结果的影响规律,探知可达的测量准确度。分析结果表明:用超声法测量螺栓轴向力时,声时差-轴向力系数对测量结果的准确度影响显著,故应对系数进行准确标定,使之与测量螺栓有效匹配;温度的波动、探头耦合状态的改变,使测量结果准确度降低,此时应采用温度补偿、二次回波分析法将这些因素的不利影响排除;探头摆放位置的不一致将使测量准确度显著降低,但可借助于相关分析方法对测量异常值进行识别与剔除。通过合理有效的测量工艺控制措施,可使超声法得到的螺栓轴向力测量结果具有较高的准确度,满足工程应用需求。     

刮板细度计示值误差非接触自动校准装置

采用光谱共焦传感器以及激光位移传感器相互配合的设计方式,研制一套新型刮板细度计示值误差非接触自动校准装置。利用光谱共焦传感器测量光点可小至5μm的优点,实现对刮板细度计测量点的精准定位,同时避免了接触测量造成测头及测量面磨损的问题。经实验证明,该装置测量重复性好、效率高,测量结果准确可靠,具有重要技术推广价值。     

基于涡流检测信号的金属曲面距离测量方法研究

为提高曲面试件的涡流测距精度,提出一种基于涡流信号差值的测距修正方法.该方法通过研究不锈钢平板试件与曲面试件涡流信号的不同,拟合计算出曲面涡流信号和平面涡流信号之间差值与曲面试件曲率的定量关系.利用这一函数关系,对不同曲率试件的测量结果进行补偿,可修正由于试件存在曲面造成的测量误差.通过实验进行可行性验证,对平板试件与...     

Measurement of acoustic reflection coefficients by an ultrasonicmicrospectrometer

An ultrasonic microspectrometer (UMSM) was developed in order to evaluate the elastic properties of a solid specimen at a small spot on its surface. In this system, spherical-planar-pair (SPP) lenses were used, by which the acoustic reflection coefficient of a liquid/solid interface was measured as a function of the incident angle in the frequency range from 20 to 140 MHz. Using a specimen of fused quartz whose material constants were well known, the measurement accuracy was examined. The phase velocity of a leaky Rayleigh wave was obtained from the phase change of the reflection coefficient with 0.4% accuracy in this frequency range. For a specimen of steel with a large acoustic attenuation, bulk attenuation factors and their frequency dependence were successfully estimated by computer-fitting of the reflection coefficient. As an example of anisotropic materials, the reflection coefficient of X-cut quartz was also measured. Measured phase of the reflection coefficient was in good agreement with numerical calculation     

Design of Low Cost Broadband Ultrasonic Pulser–Receiver

Determination of ultrasonic propagation velocity in materials provides an insight into their intrinsic and extrinsic properties. The American National Standard, E-494–95 describes an exhaustive procedure of ultrasonic velocity measurement and various material parameters that are based on ultrasonic velocity. Ultrasonic pulser–receiver is a device, used to excite piezoelectric transducers. Further, a oscilloscope or data acquisition device is employed to display and analyze the receiver output. The quality of measured parameter mainly depends on the capabilities of the measurement device used at the receiver. Careful study of the displayed wave pattern enables the detection of deformities inside the metal blocks. In this article, a low cost pulser–receiver designed in the laboratory has been discussed. The design provided can be used by a person having considerable knowledge of electronics to build up a pulser–receiver. The designed device has been tested for its functionality to measure ultrasonic velocity and attenuation. The measured values have been compared with the literature values and are in close agreement with the measurements taken by an imported system.     

测量复合材料热导率的前表面技术

本文提出了一种测量非匀质各向异性复合材料的热导率的新瞬态法——“前表面技术”。在此法中,试样是一个园柱体(直径约10mm、高约10～20mm),一端面受激光辐照,记录下试样前表面的温度变化,并由此可算得试样的热导率。这种方法是在派克法的基础上发展起来的,具有试样大小适中,测速快,应用范围广等优点。文中阐述了方法的理论模型、公式和测试结果。      

A PC-based real-time Hall probe automatic measurement system formagnetic fields [of SRRC magnets]

A real-time, Hall-probe automatic measurement system was developed at the Synchrotron Radiation Research Center (SRRC) for the magnetic field measurement of the “C”-type rectangular combined function bending magnet, multipole magnets, and the insertion device magnets. The sampling rate on the x-y-z table with dynamic moving speed of 15 cm/s can be up to 200 samples/s, and the precision is within ±0.01%. A PC is used as a system controller which connects instrument function cards with instruments via the PC bus and an IEEE-488 interface card. An inexpensive, stable within ±15 ppm current source is produced to supply a high-stability constant current for the Hall probe; a temperature controller maintains the Hall probe temperature within ±0.2°C. The system's software has been divided into different modules that can be connected into a network global data base. System testing has shown that the magnetic field measurement accuracy of this system is better than ±25 ppm in the static measurement     

Experimental study of construction mechanism of V(z) curves obtained by line-focus-beam acoustic microscopy

The propagation characteristics, viz., phase velocity and attenuation, of leaky surface acoustic waves (LSAWs), excited on the water/sample boundary are obtained through analyzing the V(z) curves measured by line-focus-beam acoustic microscopy. However, different values of these characteristics are obtained, depending upon different ultrasonic devices and operating frequencies employed. The construction mechanism of V(z) curves was investigated experimentally by measuring the amplitude and phase for Teflon to provide an understanding of the device performance for velocity measurements. A V(z) curve measured for Teflon, on which no leaky waves are excited when water is the coupling medium, can be used for the characteristic device response, depending only upon the device parameters and the operating frequencies. From the investigation of the ultrasonic device and the frequency dependences of the characteristic device responses, the phase gradient was found to be directly related to values of measured LSAW velocities. From this result, apparent frequency dependences in LSAW velocity measurements are explained quantitatively for a specimen of gadolinium gallium garnet.     

超声水浸法高精度测量玻璃材料声速的研究

材料的声速与其杨氏模量和密度有关,通过测量材料的声速可以评价材料的特性。相关研究表明,超低膨胀玻璃的声速是评价其热膨胀系数的关键参数,通过测量声速可以实现对超低膨胀玻璃热膨胀系数的间接无损测量。针对市售的超声声速测量仪器存在系统复杂且不易集成化的问题,结合高精度的数据采集卡设计了超声信号采集显示软件,并基于超声水浸脉冲反射法搭建了高精度的声速测量系统,系统结构简单,操作方便且较易集成化。采用该测量系统对制备的超低膨胀玻璃样品的声速进行了测量,结果表明该系统具有较高的声速测量分辨率,声速分辨率可达为0.2 m.s^-1,为使用超声声速法高精度测量超低膨胀玻璃的热膨胀系数奠定了研究基础。     

A High-Speed Ultrasonic Sing-Around System

An ultrasonic sing-around system has been developed that allows the measurement of the velocity of sound in a sample to an accuracy of a few parts in 104 in a period of 10 ?s. A facility is also provided to store a succession of measured sing-around periods. This approach enables the continuous measurement of the velocity of sound in materials undergoing rapid changes of thermodynamic parameters such as temperature, magnetic field, or pressure to be achieved. As an example, the magnetic-field variations of the velocity of sound in a magnetic gadolinium-yttrium alloy are reported.     

超声测流装置的实验室测试与优化

为提高大口径管道流量在线校准的准确度,建立了一套多声道超声测流装置,对其现场探头定位安装及几何测量方法进行了优化,并在研究流量计算模型的基础上进行了不同探头插入状态的实验室测试。在DN400的管道上安装交叉4声道超声探头,测试了3种探头插入状态,通过分析流量测量误差来得到最优化方案。实验表明,探头插入状态显著影响装置流量测量误差,随着插入深度的增加流量测量结果逐渐增大,但即使全突状态流量依然偏小;3种状态中全缩线性较好,经过系数修正后,全缩状态下超声测流装置计量准确性最高,达到0.2级;超声测流装置经过实验室测试与优化,可以满足1.0级大口径管道流量在线校准的要求。     

运动参量校准装置系统的研制

摘 要：为了对运动参量测试设备进行校准,研制了一套双曲柄连杆耦合运动装置。通过两套变频调速伺服电机进行运动控制,产生了大范围可调的动态位移、速度、加速度等运动参量。通过4通道高速采集卡和工控机完成全程运动参数的精确测量和运动误差分析。在设计机械结构、控制系统和信号测量系统的基础上,提出了一种基于时间共轭的超前反馈控制算法和基于相位比较的测量方法。测试结果表明速度、加速度的测量误差小于1%。该校准装置可以用于运动测试设备的校准。     

Measurement of fatigue crack growth in large compact tension specimens using an AC magnetic field method

Fatigue crack growth rate data are required in order to carry out a numerical analysis of the fatigue performance of complex structural components. These data are obtained by measuring crack growth in standard fracture mechanics specimens. A new method for measuring fatigue crack growth in compact tension specimens has been developed. The technique is based on the measurement of the surface magnetic fields produced when passing a high-frequency alternating current through the specimen. Fatigue crack growth data recorded using this method indicated an accuracy of ±0.02 mm when compared with optical measurements. The technique is suitable for computer-controlled operation and could easily be applied to other standard specimen geometries.     

一种直接驱动式振动管密度测量装置的研制

研制了一种基于直接驱动式振动管原理的密度测量装置。在振动管内为真空和充满无水乙醇的条件下,温度为260～360K、压力为0.1～20MPa范围内标定了装置的仪器常数。通过测量异丙醇和仲丁醇的液体密度检验了装置的性能,并将实验结果与文献数据进行比较,异丙醇数据与文献数据偏差在0.2%以内,仲丁醇数据与文献数据偏差在0.3%以内,验证了装置的精度满足密度测量需求。