Nondestructive testing and characterization of residual stress field using an ultrasonic method

To address the difficulty in testing and calibrating the stress gradient in the depth direction of mechanical components, a new technology of nondestructive testing and characterization of the residual stress gradient field by ultrasonic method is proposed based on acoustoelasticity theory. By carrying out theoretical analysis, the sensitivity coefficients of different types of ultrasonic are obtained by taking the low carbon steel(12%C) as a research object. By fixing the interval distance between sending and receiving transducers, the mathematical expressions of the change of stress and the variation of time are established. To design one sending-one receiving and oblique incidence ultrasonic detection probes, according to Snell law, the critically refracted longitudinal wave (LCR wave) is excited at a certain depth of the fixed distance of the tested components. Then, the relationship between the depth of LCR wave detection and the center frequency of the probe in Q235 steel is obtained through experimental study. To detect the stress gradient in the depth direction, a stress gradient LCR wave detection model is established, through which the stress gradient formula is derived by the relationship between center frequency and detecting depth. A C-shaped stress specimen of Q235 steel is designedto conduct stress loading tests, and the stress is measured with the five group probes at different center frequencies. The accuracy of ultrasonic testing is verified by X-ray stress analyzer. The stress value of each specific depth is calculated using the stress gradient formula. Accordingly, the ultrasonic characterization of residual stress field is realized. Characterization results show that the stress gradient distribution is consistent with the simulation in ANSYS. The new technology can be widely applied in the detection of the residual stress gradient field caused by mechanical processing, such as welding and shot peening.     

A technique of ultrasonic testing of articles with curvilinear surfaces

The results of development of a technique, specimens, and special transducers for ultrasonic testing of valves (taps) for high-pressure pipelines and for the compressed part of pipeline taps (elbows) are discussed. Specific features of adjustment of the scan duration, a depth gauge, and the sensitivity of a flaw detector are considered.     

Calibration blocks for ultrasonic nondestructive testing

The main parameters of calibration blocks for ultrasonic testing that must be measured during metrological certification are considered: the geometric dimensions of reflectors, the velocity and attenuation of elastic waves, etc. A method for measuring the damping factor is proposed that simplifies the measurement procedure. A form of the certificate registered officially for calibration blocks that were subjected to metrological certification is presented.     

Improving signal-to-noise ratio in ultrasonic testing

A method for improving signal-to-invoice ratio in information systems of ultrasonic measurements is proposed. Algorithm and embodiment are suggested that can be realized with least costs. Numerical modeling has proved the efficiency of this method for various values of raw data.     

A novel method for digital ultrasonic time-of-flight measurement

Most ultrasonic ranging measurements are based on the determination of the ultrasonic time-of-flight (TOF). This paper develops a novel method for the TOF measurement which combines both the improved self-interference driving technique and the optional optimization signal processing algorithms. By stimulating the transmitter with the amplitude modulation and the phase modulation envelope square waveforms (APESWs), the proposed system can effectively reduce the errors caused by inertia delay and amplitude attenuation. In addition, based on different signal-to-noise ratio test conditions, the resultant received zero-crossing samples, which are deteriorated by noise, can be precisely inspected and calculated with two optimized algorithms named zero-crossing tracking (ZCT) and time-shifted superposition (TSS) method. The architecture of the designed system is divided into two parts. The novel APESW driving module, the received envelope zero-crossings phase detection module, and the ZCT method processing module are designed in a complex programmable logic device. The TSS signal processing module and the optimization algorithm discrimination program module are integrated in a digital signal processor. The TOF measurements calibrated in ultrasonic ranging experiments indicate that the relative errors of the method are limited in ±0.8%. Therefore, a feasible method is provided with the advantages of high noise immunity, accuracy, low cost, and ease of implementation.     

超声电动机测试系统的研究

超声电动机技术参数的测量对其研究有重大意义,分析目前超声电动机测量的研究现状和存在问题,提出一种基于LabVIEW的测试系统构架,将是未来超声电动机测试技术发展的一个趋势和方向.     

A program for 3D simulation of signals for ultrasonic testing of specimens

Optimization of the parameters of schemes using multichannel ultrasonic flaw detectors for sonic testing of rails (sonic test schemes), as well as development of algorithms for processing test signals, are considered. The efficiency of the RAIL-3D computer code proposed for the 3D simulation of the propagation and formation of echo signals during ultrasonic testing is tested by comparing real signals and simulation results for a CB-2 calibration block. The comparison is performed for the complex conditions under which rails are tested. The code can also be used for simulating signals of ultrasonic nondestructive testing in other metal products.     

Classification of flaws in ultrasonic and X-ray testing

Classification of flaws in welded joints during X-ray and ultrasonic nondestructive testing are considered. The consideration is focused on the parameters of flaws that affect the reliability of the tested item. Recommendations are made to improve identification of a flaw’s shape and type via relationships between test signatures and to assess parameters involved in calculations of the strength and service life of a tested item.     

An automated system for ultrasonic testing of disks

The design and functions of separate units of an automated system for ultrasonic testing of disks in aircraft industry are briefly described. The testing results are presented in the form of a defectogram     

Application of the double-scanning method in ultrasonic nondestructive testing of metals for reconstruction of model defect images

The results of application of the double-scanning method for obtaining images of model defects during ultrasonic flaw detection in metals are presented. It has been shown in model experiments that, during reconstruction of flaw images, the amplitudes of parasitic reflections formed by echo signals, which were transformed and repeatedly scattered by inhomogeneities, decrease considerably. These properties of the double-scanning method may be useful in the practice of ultrasonic inspection of heavily loaded objects, especially in the case of the pressing problem of classifying the detected flaws. To identify the type of defects and determine their number accurately, it is desirable to use images obtained in both the double-scanning and transceiver modes. The images obtained during operation of a transducer in these two modes are compared.     

小波包分析在摩擦焊超声检测信号消噪中的应用

在摩擦焊接过程中,由于焊接参数的波动或一些非正常因素的介入,接头中容易产生未焊合及伪结合等缺陷。对于伪结合缺陷,其超声检测信号信噪比很低,一般条件下很难检测出来。本文采用小波包对该类缺陷超声检测信号进行消噪,结果表明,该方法不仅能有效抑制噪声,而且能明显提高信噪比。     

A new reference method for testing hydrometers

The two methods for determining the density or specific gravity of liquids used in testing hydrometers are: (1) comparison with standard reference hydrometers, and (2) hydrostatic weighing. In this paper, a new method for the determination of the density of liquids for the testing of hydrometers is described. The method involves determining the differential pressure between two points or planes separated vertically in a liquid and dividing the differential pressure by the product of the local acceleration due to gravity and the vertical separation. The system is based on sound scientific principle, is easy to use, is very precise, and is easily and accurately calibrated using water. The results for such a system are demonstrated for water and for nitric acid solutions. The precision is shown to be approximately 1 part in 10 000 or 0.01%, which is ideal for the testing of hydrometers the precision of which is about 1 part in 1 000 or 0.1%.     

A method for proximate testing of railroad wheels

A new method for nondestructive testing of railroad wheels using natural vibrations that are excited by a hammer impact is proposed. The method is based on the effect of the generation of the dominant frequencies of natural vibrations in the presence of cracks. A physical substantiation of the method and the results of experimental studies are presented. The place of the proposed method in the general system of nondestructive testing of railroad wheels is determined. In addition, methods for nondestructive testing based on using natural vibration frequencies are briefly reviewed.     

一种快速检测非球面面形的新方法

目前非球面面形的检测方法大部分复杂且费时。介绍了在干涉测量法的基础上利用ZYGO干涉仪的波面相减功能,用波面相减的方法对非球面面形进行测量。利用Matlab软件进行程序设计解决该方法中对理想非球面的Zernike系数计算的关键技术,并验证了程序的正确性。这种方法达到直接检测的目的,缩短检测时间和成本。     

Modern approaches to the certification of ultrasonic testing techniques

Algorithms intended for certifying ultrasonic testing techniques and based on the complex application of reliability and accuracy indices, which are constructed taking into account the character of techniques, specific features of their use, and the objectives of their certification (comparison of techniques, introduction of a new technique involving measurement procedures, etc.) are proposed. On the basis of the main regulations of GOST (State Standard) R ISO 5725-1, 5725-2, the reproducibility and repeatability of determining the measured characteristics of artificial reflectors and actual flaws and the reliability of ultrasonic testing of welded joints have been assessed.     

自动扫描超声探伤检测系统抗干扰解决方案

为解决自动扫描超声探伤检测系统中超声信号所遇到的干扰,从系统的组成、工作流程方面人手,探讨了噪声产生的来源、传导方式、途径,并进行了分析,然后从系统集成的层面上提出了在设备设计及实施过程中具有一定抗干扰能力又行之有效的系统集成方案,并探讨了在该集成方案下对各种干扰可以采取的措施,对之进行了分析、比较,提出了有效的解决方...     

Application of 3D coherent processing in ultrasonic testing

A 3D variant of the coherent method of projection in the spectral space (PSS) for obtaining images of reflectors on the basis of measured echo signals is considered. Its application allows recon-struction of reflector images with a high frontal resolution in both the main plane of an ultrasonic transducer and an additional plane. The application of the PSS method is especially efficient when a reflector is far from the receiving aperture. In this case, it is possible to increase the signal-to-noise ratio by more than 12 dB and a tenfold increase in the frontal resolution can sometimes be attained as compared to the 2D layer-by-layer variant of the PSS method. Examples of the application of this method during reconstruction of reflector images in a specimen of the wall of a chemical reactor, in the case of multiple reflections from the walls of a welded T-branch with an overlaid plate (WTP), and when testing large-diameter studs and supports of the divertor, which is manufactured as part of the work on the thermonuclear reactor (ITER) project, are presented. The efficiency of applying the 3D variant of the PSS method for testing at large depths is shown.     

The possibility of using the maximum-entropy method in ultrasonic nondestructive testing for increasing the resolution of echo signals

The problem of deconvoluting echo signals via regularization according to the maximum entropy method followed by the reconstruction of 2D images via the Fourier transformation synthetic aperture focusing technique (FT-SAFT) is considered. Numerical and experimental simulations have been performed. The possibility of improving the ray resolution of echo signals and reducing the speckle-noise level is demonstrated. The results obtained are compared to the results of constructing an AR model of the spectrum of echo signals.     

一种激光束形参数简便测试方法

在以激光作为测试光源的高精度测试装置中,激光器实际输出的束形参数值与其标称值的偏离会直接传递并影响到后续测试结果的准确度。提出一种基于CCD的多点测试方法,此方法在不降低测量精度的条件下可实现激光束形参数的简便测试。在搭建的测试装置上实现了633nm He-Ne激光器束腰半径、远场发散角和M2质量因子的测量,可以方便地评价激光光束质量。将束形参数简便测试方法的结果与法国Phasics公司的SID4波前探测器的测量结果进行了比对,结果表明,激光束形参数简便测试方法不仅能用于激光束形参数的简便检测,而且具有较高的精度。