Ultrasonic methods for measuring crack location,crack height and crack angle

Two ultrasonic methods are proposed to measure the crack location and the crack height for vertical and inclined defects. The methods measure the time traversed between the entry point of the sound beam in the material and the defect. Differing from most previous methods, they do not depend on knowing the probe angle, a parameter difficult to measure accurately and which varies from material to material being inspected. Accordingly, the crack can be viewed from different angles, thus reducing the random error in the measurement.     

Ultrasonic density measurement for process control

A method has been devised for determining the density of a fluid by measuring the velocity and amplitude of an ultrasonic pulse passed through it. The theory of the method is presented, together with the results of an experimental verification.     

The measurement of residual stress in textured steel using an ultrasonic velocity combinations technique

A new ultrasonic technique for the determination of residual stresses in steel, intended to correct for the effects of variable texture and microstructure, is proposed. The method is based upon the use of the compressional wave time delay in addition to the time delays of two orthogonally polarized shear waves used in the shear wave birefringence technique. This method is justified theoretically using expressions for the ultrasonic velocities in an aggregate of orthorhombic symmetry composed of cubic crystallites.Measurements of the three time delays for propagation in the through thickness direction have been made on a large number of steel plates selected at random. The measurements are found to fall on two lines, and reveal that two types of texture are present in rolled steel plates. In the presence of a stress, the measured points deviate from the lines and this effect is quantified theoretically using elastic constants obtained by applying a uniaxial compressive stress to one of the samples.The usefulness of the technique to determine a residual stress distribution is demonstrated by measurements near the tip of a crack in a compact tension specimen.     

Acoustic cavitation series: part six. Gas body activation

An ultrasonic instrument for the accurate measurement of bolt stress is described. The instrument, which is based on the pseudo-continuous-wave technique, uses carrier phase detection to track the frequency of the mechanical resonance of the bolt. The basic operation of the instrument and the experimental results obtained are discussed.     

Ultrasonic SH wave velocity in textured aluminium plates

Neutron diffraction has been used to measure the crystallite orientation distribution function for a sample of rolled aluminium plate. Based on this study an expression is given for the ultrasonic velocity of the fundamental horizontally polarized shear (SH) wave propagating in the plane of the plate at an angle θ to the rolling direction. This expression is correct to second order in the leading texture component and is compared with the exact numerical result and with measurements of the SH wave velocity for this plate. In textured materials the group and phase velocities are not, in general, parallel and an expression for the angle between them is derived. Inclusion of this effect leads to better agreement between experiment and theory. The results have application to the texture-independent determination of stress with ultrasonics recently proposed by MacDonald and Thompson et al.     

在线超声波流量监测系统设计及其应用

为解决地源热泵系统中的进出水流量测量,设计研究基于超声波时差法原理的非接触式在线流量监测装置。系统以STM32F407 ZE为主控制器,定时采集流量、完成数据封包、加密和远端服务器交互任务;以MSP430F2618为流量测量控制器,采用时差法以TDC-GP22精准测量超声波在介质中传播时间,实现管道流体流速、流量实时监测。系统测试结果实现流量数据测量及上传存储到远端服务器,满足地源热泵系统流量监测需求。     

微机化超声螺栓轴向应力仪的原理与误差分析

本文提出用沿轴向纵波声时差以测螺栓的轴向应力，推导了声时差与应力的关系．利用声时差测螺栓轴向应力，能克服耦会误差”“，同时还能克服温度引起的伸缩及波速变化的声时误差·本文还导出并且从实验上测出了，只与螺栓材料有关，而与螺栓的夹紧长度，直径，总长无关的常数，简化了测量过程．经实验测定，在夹紧长度大于30mm，应力低于240MPa时，应力最大误差小于±4MPa．本文还分析了声时，夹紧长度测量误差所导致的应力误差．     

Determining quality of graphite electrodes for electric arc furnaces by measuring ultrasonic velocity

Measuring ultrasonic velocity is an efficient means of determining electrode quality for electric arc furnaces. Close correlation between ultrasonic velocity and the physico-mechanical characteristics of the electrodes was obtained by statistical analysis.The variation of ultrasonic velocity is shown for different fabrication stages of graphite electrodes as a function of their mechanical characteristics and structure. We also present some aspects of the experimental work and apparatus used.     

含气量测量仪的研制

利用压强差与液体中含气量间的关系,制作出液体中含气量的测量装置。     

Ultrasonic Lamb wave method for sizing of spot welds

Two spot-welded thin sheets can be treated as two elastic waveguides coupled by a small common welded region. It is proposed to use Lamb waves to evaluate the quality of the weld. The feasibility of selecting the working frequency and mode number of the Lamb wave so that no resonance of the elastic vibrations appears in the weld region is considered analytically. This condition ensures a one-to-one correspondence between the mean diameter of the spot-weld region and the coefficient of transmission of the Lamb waves through it.A simple technique is suggested for determining the transmission coefficient and the scattering patterns of Lamb waves at the weld region. Experiments indicate that, to a satisfactory approximation, the wave transmission coefficient is proportional to the cube of the weld diameter. This allows a unique determination of the dimension of the welded region on the basis of the amplitude of the transmitted signal.     

Ultrasonic synthetic aperture focusing using planar pulse-echo transducers

The lateral resolution of digital data from the planar (unfocused) pulse-echo transducers used in conventional ultrasonic inspections can be improved using the synthetic aperture focusing technique (SAFT).

For practical applications it is important to minimize the level of sidelobes (artefacts) introduced by SAFT, without significant loss of resolution. This may be achieved by the inclusion of a suitable aperture-weighting function in the SAFT algorithm, combined with a synthetic aperture size related to the width of the transducer beam-spread.

The properties of the resulting optimized SAFT algorithm are quantified using experimental data from a series of artificial flaws (slots) of different sizes.     

标准白场仪及视角测量方法的研究

 针对目前主流彩色电视与平板显示器,建立了能够溯源到国家光谱辐射度、光度与色度基准的标准白场仪装置,可用于显示器光色特性参数测量。对该装置进行了定标,提供了标准白场仪光谱、稳定性以及光色参数。应用该标准装置对主流的液晶显示器进行了视角研究,主要考虑了测量过程中所忽略的被测发光面积因素对视角特性的影响。结果表明,基于绝对亮度的视角阈值方法,差别可达8%以上,是测量过程中需要考虑和避免的。     

用纵横波声时比法测螺栓轴力精度研究

用纵横波测量螺栓轴力的技术已取得较大发展,本文介绍了纵横波比值法原理,通过理论推导,获得比值法计算的简易公式。建立试验平台,用现场用螺栓进行标定和测量,得出比值法在工程实践状态下的测量误差为10%以内,基本能满足工程应用的要求。此外,针对试验结果,本文还初步探讨了误差出现的原因以及提高精度的方法。本文介绍的比值法,无需精确测量标定螺栓长度和纵横波声速,现场应用更加简洁,具有较大的工程应用价值。     

靶场红外成像测量设备精度检测方法研究

提出了采用动态精度检测靶标对红外跟踪测量系统进行检测的方法。分析了靶标与被检测设备的空间运动关系。研究了跟踪性能和测量精度。对检测数据进行了计算处理,检测结果验证了这种检测方法的可行性。     

An ultrasonic method for measuring the elastic constants of wood increment cores bored from living trees

Three stiffness moduli and three shear moduli were determined using an ultrasonic velocity method for 5 mm diameter increment cores bored from living beech trees. The validity of the method was assessed by comparing the results for the increment cores with those for standard specimens loaded in static bending and on cubes tested with ultrasonic transverse waves.Good correlation was found between the elastic constants of the cores and standard specimens. It was noted that the regression equation between the modulus of rupture and the longitudinal stiffness modulus for cores, or between the modulus of rupture for standard specimens and longitudinal velocity in cores, permits one to predict the strength of living tree wood through a simple ultrasonic test. The technique is capable of rapidly detecting the differences between individual characteristics of living trees.     

基于LabVIEW的时间反转超声检测系统的开发

时间反转技术在超声无损检测中的应用非常广泛,它可以忽略介质的非均匀性及初始信号源的位置,能够在时间和空间上聚焦超声波,实现对介质缺陷的聚焦检测。基于LabVIEW图形化编程软件,结合计算机、信号发生器、示波器、超声换能器、GPIB等的使用,对超声检测系统实验平台进行了构建,实现了超声信号的发射、接收以及时间反转一系列的信号处理过程。系统工作过程中,采用了三种不同的时间反转技术：经典时间反转技术(Time Reversal：TR)、反向滤波技术(Inverse Filter：IF)及1位处理技术(1Bit Processing),来实现信号的聚焦。实验验证该系统可以有效的实现时间反转超声检测过程中对信号的激励、接收、处理和存储等功能,有良好的精确性和适用性。     

螺栓材料应力与声速、温度关系的测定

基于应力－超声波速度关系方法已用于螺栓轴向应力的测量。而声速与被测材料的许多物理因素有关，如弹性模量，密度与温度。本文介绍了用于分析超声波速度－应力－温度三者关系的实验与计算方法，并给出了三种金属材料的结果。检测的质量。     

基于双频超声波技术的导盲实验设计

为提高学生对超声波的实际应用能力,在超声波测距技术的基础上,引入广泛应用于海洋探测方法中的双频超声波探测技术设计了一个导盲实验。该导盲系统能够在十几米甚至二十米的范围精确地探测障碍物距离,同时具有大量程与高精度两大优势,且采用太阳能供电,报警装置还可以播报障碍物距离。     

六面顶压机上常温高压超声测量的样品组装设计

 简要介绍了高压超声测试技术中样品组装的设计原则。设计了一套新的样品组装,并测量了纯Al和纯Cu在常温下的等温状态方程。实验结果表明,新的组装能够实现较理想的准静水压加载,同时也能够测试出良好的超声信号。分析了六面顶压机上常温超声测量的主要误差来源。     

变对比度变频变亮度四方位人眼对比度阈值仪器的测试技术研究

为了提高诊断人眼对比敏感度性能,研制了变对比度、变频率、变亮度和四方位可控的计量校准级对比度阈值测试仪器。提出了可行的变对比度挡光板的移动以及变频率和四方位靶板组切换的优化控制设计方案。