Nonlinear signal processing techniques in ultrasonic tomography of concrete structures

Questions of using various techniques for processing echo signals in ultrasonic tomography instruments for extended complexly structured concrete articles are considered. Various algorithms are discussed for constructing tomograms of tested articles, techniques for radio engineering processing of ultrasonic signals, and different variants of nonlinear image transformations intended for increasing the signal-to-structural noise ratio and improving image quality.     

Identification techniques applied to a passive elasto-magnetic suspension

The paper presents an experimental passive elasto-magnetic suspension based on rare-earth permanent magnets, characterized by negligible dependence on mass of its natural frequency.The nonlinear behaviour of this system, equipped with a traditional linear elastic spring coupled to a magnetic spring, is analysed in time domain, for non-zero initial conditions, and in frequency domain, by applying sweep excitations to the test rig base. The dynamics of the system is very complex in dependence of the magnetic contribution, showing both hardening behaviour in the elasto-magnetic setup, and softening motion amplitude dependent behaviour in the purely magnetic case. Hence it is necessary to adopt nonlinear identification techniques, such as non-parametric restoring force mapping method and direct parametric estimation technique, in order to identify the system parameters in the different configurations.Finally, it is discussed the ability of identified versus analytical models in reproducing the nonlinear dependency of frequency on motion amplitude and the presence of jump phenomena.     

Special features of the ultrasonic tomography of thick-sheet products

The special features of the beam tomography of thick-sheet products are considered, and a few techniques aimed at improving the efficiency of tomographic reconstruction based on limited data collected by ultrasound methods are proposed. Results of computational modeling and experimental reconstruction of the physical-mechanical characteristics of a thick-sheet product containing a welded joint and a thermal inhomogeneity obtained using the suggested information technologies are presented.Translated from Defektoskopiya, Vol. 40, No. 7, 2004, pp. 3–16.Original Russian Text Copyright © 2004 by Koshovyy, Kryvin, Muraviov, Romanyshyn.Deceased     

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.     

Anisotropic characterization of particleboard by ultrasonic and static techniques

The anisotropic properties of particleboard (PB) are studied by ultrasonic and static techniques. Ultrasonic wave velocity and modulus of elasticity in bending (MOE) are determined at parallel and perpendicular to manufacturing direction and at the interval angles of 15° in clockwise and counter-clockwise directions. The experimental results are compared with the predicted values using empirical formulas such as the Hankinson and Jacoby equations. The results show that the ultrasonic wave velocity and MOE are the highest in the parallel direction in PB and the lowest values occurred in the perpendicular direction. The predicted ultrasonic wave velocity using the Hankinson and Jacoby equations are in close agreement with the measured value. The relationship among particles angle, ultrasonic wave velocities, and MOE could be successfully presented by cubic and quadratic regression equations as well.Translated from Defektoskopiya, Vol. 40, No. 9, 2004, pp. 42–50. Original Russian Text Copyright © 2004 by Kazemi Najafi, Abbasi Marasht, Ebrahimi.This article was submitted by the authors in English.     

Detection of reflecting planes in ultrasonic tomography of concrete building structures

The features of algorithms for identifying the configurations of reflecting objects (points, spheres, planes, cylinders, etc.) in ultrasonic tomography of complexly structured concrete products are considered. The results of a practical solution to the problem of recognizing a pattern and determining the coordinates of a flat reflector using ultrasonic phased antenna arrays are presented for the example of applying the algorithm of focusing to a plane.     

Gas/liquid two-phase flow regime identification by ultrasonic tomography

A gas/liquid two-phase flow is considered as a strongly inhomogeneous medium with respect to high contrast in acoustic impedance distribution. Based upon a binary logic operation and a method of “time-of-propagation along straight path”, an ultrasonic facility for tomographic imaging of gas/liquid two-phase flow was developed. In this paper the principle and construction of this facility are briefly introduced. Emphasis is placed on the evaluation of its performance in flow regime identification and cross-sectional void fraction measurement. Several flow pattern models were used and the corresponding monitoring results given. Finally, limitations and possible future improvements of the system are discussed.     

Methodological principles and techniques of ultrasonic acceptance tests of wheelset axles

The ultrasonic system designed for performing acceptance tests of wheelset axles of railway rolling stock during production with the aim of detecting metallurgical flaws and/or flaws caused by drawbacks in the manufacturing process is substantiated. The effect of the factors not regulated by the normative documents on the testing reliability, including the type and structure of probes, their location, and the surface state of a tested object, is analyzed. Recommendations for improving reliability and reproducibility of the acceptance test data on wheelset axles are formulated and confirmed experimentally.     

一种超声波洗衣机的研发

为解决目前市场上的超声波洗衣机体积大、价格高、洗涤效果差、使用不方便等缺点,研制了一款新型超声波洗衣机。该款超声波洗衣机与传统洗衣机在结构、体积和功能上都有革命性改变,主要分为储液装置、清洁装置和操作台3部分,较重部件都装在主机上,由手柄实现两大功效———清洁和干燥,即用力挤压衣物时利用超声波的空化作用,向初步湿润的衣物局部发出高频超声波使油污在声场的作用下乳化,达到固体粒子脱离衣物实现表面净化的目的;轻触衣物时利用高温高速气流实现对衣物局部湿润面的熨烫干燥。在功能上与市面上的普通洗衣机相比毫不逊色,且集洗涤、熨烫和干燥等功能于一体,在细节处理上具有更多优势。     

超声表面强化技术的研究进展

介绍了目前发展较为成熟的几种超声表面强化技术,如超声喷丸、超声挤压、超声滚压和超声振动辅助电火花脉冲放电等的基本原理、技术特点和研究进展,指出了各类超声表面强化技术研究中尚待解决的问题,并提出了超声表面强化技术的发展趋势。     

Contingency table techniques for three dimensional atom probe tomography

A contingency table analysis procedure is developed and applied to three dimensional atom probe data sets for the investigation of fine-scale solute co-/anti-segregation effects in multicomponent alloys. Potential sources of error and inaccuracy are identified and eliminated from the technique. The conventional P value testing techniques associated with chi(2) are shown to be unsatisfactory and can become ambiguous in cases of large block numbers or high solute concentrations. The coefficient of contingency is demonstrated to be an acceptable and useful basis of comparison for contingency table analyses of differently-conditioned materials. However, care must be taken in choice of block size and to maintain a consistent overall composition between experiments. The coefficient is dependent upon block size and solute composition, and cannot be used to compare analyses with significantly different solute compositions or to assess the extent of clustering without reference to that of the randomly ordered case. It is shown that as clustering evolves into larger precipitates and phases, contingency table analysis becomes inappropriate. Random labeling techniques are introduced to infer further meaning from the coefficient of contingency. We propose the comparison of experimental result, mu(exp), to the randomized value, micro(rand), as a new method by which to interpret the quantity of solute clustering present in a material. It is demonstrated that how this method may be utilized to identify an appropriate size of contingency table analysis blocks into which the data set is partitioned to optimize the significance of the results.     

超声波技术在核电厂给水流量测量中的应用

为了解决差压式流量计在主给水流量测量中存在的问题,将超声波技术应用到主给水流量测量中。开展了主给水流量精度对于核电厂反应堆热功率计算及其不确定度影响的分析,总结了国内外核电厂通过提高主给水流量测量精度的方式进行核电厂小幅度功率提升的研究成果和实践经验。分析了国内在建的AP1000核电厂中,通过采用超声波流量计进行主给水流量测量以及进行小幅度功率提升项目的意义、可行性、需要开展的工作以及实施该项目潜在的收益和风险。研究结果表明,基于超声波技术完成主给水流量测量,可以实现AP1000核电厂的小幅度功率提升,同时可以使核电厂更加安全、稳定和有效地运行。     

横向超声多普勒互相关湍流测量方法研究

本文分析了多普勒频谱展宽效应引起的湍流估计谱模糊,提出横向多普勒双采样单元互相关方法进行湍流测量,并设计了湍流测量实验系统。实验结果表明,该方法可消除湍流、渡越时间效应、采样单元内流速梯度和双采样单元内散射粒子互相关性等因素造成的湍谱模糊,实现无模糊湍流测量。     

二维频域光学相干层析系统研究

针对时域光学相干层析成像系统的成像速度较慢的问题,采用VC++与Matlab混合编程技术开发了二维频域光学相干层析成像系统,实现了对被测样品进行内部快速成像;搭建二维频域光学相干层析成像系统代替一维频域光学相干层析成像系统;利用计算机驱动面阵CCD相机对干涉信号进行采集得到干涉信号;采用计算机驱动NI卡对压电陶瓷(PZT)移相器进行相移控制以达到频域光学相干层析成像系统对移相的需求,利用计算机驱动线性电动移动平台实现检测样品进行横向扫描以达到对样品进行三维成像。研究结果表明,该系统集成度高,开发的软件功能齐全、界面友好、便于维护和升级;该二维系统相比一维光学相干层析成像系统而言减少了一维的扫描采集次数,大大提高了成像速度。     

Nondestructive testing of a bottom surface and construction of its profile by ultrasonic tomography

A technology for ultrasonic tomography aimed at the detection of flawed zones in unilaterally accessible concrete structures and the determination of their thickness and coordinates was presented. The construction of tomograms was described step by step. The results obtained by the current and previous tomograph variants were given. The tomograms of concrete specimens with specified model flaws and without them were obtained. Results with a lower noise level were obtained using the current tomograph variant. The need for the processing of a set of signals for the diagnostics and monitoring of concrete objects was shown.     

小型化星载被动型氢原子钟研制* .txt

摘要：被动型氢原子钟在具有较好中长期频率稳定度和频率漂移率的同时,体积和重量较小,可作为高精度频率标准应用于卫星导航、频率计量等领域。下一代卫星导航系统的重要特点是高密度高集成度,对包含被动型氢原子钟在内的卫星负载载荷提出了更高要求。为此,降低体积重量的同时进一步提高性能指标是被动型氢原子钟的重要发展方向。经过长期理论探索和实验验证,在小型化星载氢原子钟研制方面取得了较好进展。通过小型化腔泡系统、小型化吸附泵、高均匀度C场和高性能磁屏蔽系统的设计,以及电路部分的紧凑优化,研制了小型化星载被动型氢原子钟工程样机。在压缩重量至135 kg以内的同时,频率稳定度提升至8×10-13 t-1/2的水平,可满足当前卫星导航系统的时频信号需求,也可更好地服务下一代北斗卫星导航系统。 .txt     

Evaluation of the health of riveted joints with active and passive structural health monitoring techniques

Many active and passive structural health monitoring (SHM) techniques have been developed for detection of the defects of plates. Generally, riveted joints hold the plates together and their failure may create accidents. In this study, well known active and passive methods were modified for the evaluation of the health of the riveted joints between the plates. The active method generated Lamb waves and monitored their propagation by using lead zirconate titanate (PZT) disks. The signal was analyzed by using the wavelet transformations. The passive method used the Fiber Bragg Grating (FBG) sensors and evaluated the spectral characteristics of the signals by using Fast Fourier Transformation (FFT). The results indicated that the existing methods designed for the evaluation of the health of individual plates may be used for inspection of riveted joints with software modifications.     

On the possibility of a priori validation of ultrasonic inspection techniques without using specimens

A test for the validation of ultrasonic inspection techniques was proposed that excludes the human factor, which is generally present when detecting artificial discontinuity flaws in an object under inspection by an inspector. The results of the proposed test are a criterion for the estimation of inspection techniques. The test is based on the data that are presented in the literature and research results obtained at the TsNIITMASH. It enables a formalized estimation of the reliability of techniques with numerically expressed type 1 and type 2 errors.     

Nonlinear ultrasonic techniques for nondestructive assessment of micro damage in material: A review

The nondestructive assessment of the damage that occurs in components during service plays a key role for condition monitoring and residual life estimation of in-service components/structures. Ultrasound has been widely utilized for this; however most of these conventional methods using ultrasonic characteristics in the linear elastic region are only sensitive to gross defects but much less sensitive to micro-damage. Recently, the nonlinear ultrasonic technique, which uses nonlinear ultrasonic behavior such as higher-harmonic generation, subharmonic generation, nonlinear resonance, or mixed frequency response, has been studied as a positive method for overcoming this limitation. In this paper, overall progress in this technique is reviewed with the brief introduction of basic principle in the application of each nonlinear ultrasonic phenomenon.