The capacities of modern EMA thickness gages

The literature concerned with the problem of studies and development of thickness gages based on the EMA method of exciting and detecting ultrasound pulses is analyzed. A new approach to the design of EMA thickness gages is developed. A prototype of the manual EMA thickness gage is designed and tested. It is shown that the EMA device offers considerable benefits when using the correlational data processing.Translated from Defektoskopiya, Vol. 40, No. 12, 2004, pp. 16–25.Original Russian Text Copyright © 2004 by Suchkov.This revised version was published online in April 2005 with a corrected cover date.     

The main advantage of electromagnetic-acoustic testing technique

From the analysis of previously published and new experimental data follows the conclusion that flaw detection data obtained with the help of electromagnetic-acoustic (EMA) transducers have better reproducibility than measurements by direct-contact transducers. The EMA technique has considerable advantages over the contact techniques when objects with “rough” surfaces are tested in the automatic mode. The advantages of the EMA technique are due to the features of its electromagnetic channel and feasibility of tuning its parameters in real time.     

基于贝叶斯更新的机电作动器健康因子构建方法

机电作动器(EMA)由于重量轻、体积小、可靠性高等优势成为多电/全电飞机的核心部件,逐步广泛应用于各类多电/全电飞机中。然而,EMA动态变化的运行模式和载荷工况给其退化建模和健康因子(HI)估计带来较大挑战。因此,提出一种基于贝叶斯更新的EMA HI构建方法。首先基于历史监测数据构建HI先验模型,在此基础上,结合贝叶斯更新理论和实时监测数据对EMA HI先验模型参数分布进行迭代更新,最终实现不同运行模式和载荷工况下EMA退化状态的准确表征。为解决变工况条件下EMA HI构建模型失配问题提供了一种新颖的思路,并基于NASA公开数据集进行了实验验证。结果表明,与基于模型辨识的EMA HI构建方法相比,基于贝叶斯更新的EMA HI构建方法具有更强的工况适应能力,能够在变工况条件下有效地构建出EMA HI。     

A universal attachment for standard ultrasonic flaw detectors and thickness gages

A brief analysis of facilities for nondestructive testing with the use of a contactless EMA method of exciting and detecting ultrasonic vibrations has been performed. A universal electromagnetic-acoustic (EMA) attachment for standard ultrasonic flaw detectors and thickness gages is described. The characteristics of the attachment and its main components—devices for generating radio signals, a generator of probe pulses, a preamplifier, a generator of biasing pulses, and EMA transducers—are presented. Examples of the use of this attachment are given.     

Investigation of the technique of ultrasonic thickness control using the EMA method

Experimental studies of the electromagnetic-acoustic (EMA) method for controlling the thickness of sheets, metalware, equipment, and pipelines were performed. New methods for the measurement of ultrasonic thickness that provide thickness control without cleaning the contact surface of a tested object and without using contact greases, as is required when using conventional contact ultrasonic transducers, are shown. On the basis of these studies and the experience of ultrasonic thickness gauging (USTG) by the contact and EMA methods, a USTG technology that uses the EMA method has been developed.     

Diagnostics of the predestruction state based on amplitude and time invariants of the flow of acoustic-emission acts

The method and results of diagnostics of the predestruction state are described based on deviations of the amplitude and time invariant relationships between the parameters of the flow of acoustic- emission (AE) acts and their stable values. The relationship of the AE invariant method with the methodology of the synergetic approach to the destruction of solids is shown. Amplitude invariant relationships of AE have been estimated both by tests of standard specimens of 15Kh2NMFA hull-plate steel and by the previous results of AE tests of a VVER-1000 reactor vessel.Translated from Defektoskopiya, Vol. 40, No. 8, 2004, pp. 79–83. Original Russian Text Copyright © 2004 by Builo.     

Increasing the sensitivity of EMA devices

It has been established that, at the present stage, it is advisable to increase the sensitivity of EMA devices via an increase in the power of the probing-pulse generator. New types of generators that allow a substantial enhancement in the sensitivity of EMA instruments have been developed. The characteristics and potential of EMA devices with a new generator have been studied. An example of detecting a model of a flaw in the form of a 1-mm-diameter flat-bottom reflector is used to show that the detection sensitivity has increased by a factor of several with an increased gap between the electromagnetic-acoustic transducer and the surface of the inspected metal.     

Energy efficient electromagnetic actuated CVT system

A continuously variable transmission (CVT) system transmits the engine/battery power to the car driving wheel smoothly and efficiently. Several types of CVT already been developed to improve the transmission losses while maintaining acceleration time. However, most of the CVT has some constraints in the actuation mechanism which led us to develop an innovative electromagnetic actuator for CVT. Simplified mathematical equations have been developed for the kinematics analysis of clamping forces of the CVT and electromagnetic forces of EMA. The EMA has been developed for ¼ scale car with two sets of solenoid. Each of the two sets has been equipped with primary and secondary pulleys for pushing and pulling the movable sheave. The solenoid is operated by controlling the supply current with a fuzzy logic controller. A simulation based fuzzy logic controller has been introduced here for identifying the desired current of the EMA actuation. The experimental results show that the EMA develops electromagnetic forces 301 N for the supply current of 3.37 amp, which makes the acceleration time of the car in the range of 2.5～3.5 sec and electromagnetic actuated CVT system highly energy efficient.     

Experimental study of sensitivity of electromagnetic-acoustic transducers for flaw detection by nondestructive echo testing using bulk shear waves

Results of experimental studies of sensitivity of electromagnetic-acoustic (EMA) transducers in the echo-testing mode are given. Flaws equivalent to reflectors shaped as disks and side surfaces of cylinders with diameters of 1 mm and more have been detected with a high probability in samples of rails, round and square blanks, and metal sheets. We have concluded that nondestructive echo testing of metals using EMA transducers can be performed with a sensitivity close to that of piezoelectric transducers.     

Optimization of Parameters of Electromagnetic-Acoustic Thickness Gauges for Thin-Wall Structures

Operation of ultrasonic thickness gauges with electromagnetic-acoustic (EMA) detection and excitation has been studied. The mode of operation using testing signals in the form of trains of two to four acoustic shear oscillations is preferable to the impact excitation in tests of thin-wall pieces (pipes, sheets, T-bars, etc.). The carrier frequency can be up to 8 MHz. The results of the reported study have been used in designing EMA thickness gauges for pipes.     

Double electrodynamic electromagnetic-acoustic transformation in a normal polarizing field

n the basis of analytical expressions obtained earlier, a numerical study of the frequency dependences of the amplitudes of the central and peripheral EMF peaks induced in measuring coils of electromagnetic-acoustic (EMA) devices (in particular, thickness gauges) after a double EMA transformation has been studied. The EMF recorded near these peaks is used as the basis for obtaining information on the time of passage of ultrasonic shear vibrations through a specimen and, in particular, on its thickness. These studies were aimed at the determination of regularities during formation of EMF pulses in EMA devices using attachable inductive transducers. The amplitude-frequency characteristics (spectra) of these EMF peaks have been obtained and the influence of the geometries of the transmitter and receiver on these characteristics has been studied. The factors related to the physics of the phenomenon and the design features of actual devices with a spatially bounded polarizing field and forming a shift of the received-pulse frequency spectrum toward higher frequencies have been revealed. It has been shown that, as the measured article thickness changes, the position of the peripheral EMF peak in the high-frequency region stabilizes.     

A physical model for detecting penetrating flaws and methods for determining the parameters of acoustic fields generated by acoustic radiation

Recently a method of noncontact acoustic inspection has been used in practice for testing the tightness of 3D metal structures. This method makes is possible to detect penetrating microleaks by recording the acoustic field generated by a special source. The source generating acoustic waves is located inside a 3D structure and the acoustic radiation propagating through channels of penetrating microleaks is recorded outside of it.Translated from Defektoskopiya, Vol. 40, No. 11, 2004, pp. 22–27.Original Russian Text Copyright © 2004 by Rozinov.     

State-of-the-art capabilities of EMA flaw detection

The literature sources devoted to studies and development of flaw detectors based on the EMA method of exciting and receiving ultrasound pulses are analyzed. A new EMA flaw detector with capabilities comparable with those of state-of-the-art contact ultrasonic flaw detectors is developed on the basis of analysis and studies performed.     

Sensitivity of the Electromagnetic Acoustical Technique for Testing Railway Rails by the Mirror-Shadow Method

A study of the sensitivity of the electromagnetic acoustical (EMA) technique for detecting manufacturing defects of railway rails by a mirror-shadow method (MSM) has been carried out. It has been found that the sensitivity of the MSM with the EMA technique using bulk shear ultrasonic waves is, in certain cases, considerably higher than the sensitivity of the traditional wet echo-pulse method or mirror-shadow method with the use of longitudinal waves. Therefore, in order to renovate or design new technical means of ultrasonic acceptance testing of rails in factories, it is advisable to use the mirror-shadow method of testing with bulk elastic shear waves polarized normally to the direction of rail rolling. This would make it possible to reduce the acceptance of intolerable internal flaws of manufacturing origin.     

Real sensitivity of EMA instruments

Results of experimental investigation into the detection of internal, surface, and subsurface flaws by ultrasonic vibration pulses that are excited and received via different types of EMATs are reported. The sensitivity of the EMA instruments developed is shown to be close to the sensitivity of modern contact flaw detectors. An EMAT and a flaw detector that take advantage of the EMA flaw-detection method for the inspection of surface and near-surface zones of metal products are developed.     

基于模态柔度曲率差的弯管结构损伤识别

为对弯管结构进行无损检测,结合有限元模拟和实验模态分析方法,对具有不同位置和程度的损伤弯管结构进行研究,计算和分析其模态柔度曲率差,探讨模态分析方法在弯管结构损伤检测中的适用性。研究结果表明：弯管结构的模态柔度具有方向性,弯管所在平面x,y方向柔度求解的模态柔度曲率差不能对弯管进行损伤识别;垂直弯管所在平面z方向柔度不仅可以对弯管进行单处、多处的损伤定位,而且可以对同一位置的损伤程度进行定量分析。     

An M-503 magnetic-field strength gage

The main concepts of a method for calculating gages for magnetic-field strengths no higher than 500 kA/m are considered. This method is intended for calibrating nondestructive-testing instruments. The M-503 gage can be both ac- and dc-operated. The gage error is within the range from 0.5 to 1.5%.Translated from Defektoskopiya, Vol. 40, No. 11, 2004, pp. 79–86.Original Russian Text Copyright © 2004 by Veksler, Gagaev, Shanaurin, Shcherbinin.     

Production and quality control of optical elements for the end cap hadron calorimeter of the CMS setup

An end cap hadron calorimeter, in which scintillators with wavelength-shifting fibers are used as the active elements, has been designed for the compact muon spectrometer (CMS) now under construction at CERN. A total of 1368 optical elements containing 21 096 scintillators have already been manufactured. The production and quality control procedures for these optical elements are described.Translated from Pribory i Tekhnika Eksperimenta, No. 1, 2005, pp. 36–45.Original Russian Text Copyright ¢ 2004 by Abramov, Volkov, Goncharov, Zaichenko, Korablev, Korneev, Krinitsyn, Kryshkin, Markov, Talov, Turchanovich.     

The ΠC-219 instrument for testing the tightness of bearing races

This instrument is based on a new method for testing the quality of fitting the inner bearing race on a wheelset axle of a railway car. The operating principle of this instrument is described, and its performance characteristics are presented.Translated from Defektoskopiya, Vol. 40, No. 7, 2004, pp. 90–92.Original Russian Text Copyright © 2004 by Belonogov, Rodionov, Shanaurin.     

Modeling and Configuration Design of Electromagnetic Actuation Coil for a Magnetically Controlled Microrobot

Non-contact actuated microbeads have attracted a lot of attention in recent years because of its enormous potential in medical, biological, and industrial applications. Researchers have proposed a multitude of electromagnetic actuation(EMA) systems consisting of a variety of coil pairs. However, a unified method to design and optimize a coil pair according to technical specifications still does not exist. Initially, this paper presented the modeling of an untethered ferromagnetic particle actuated by externally applied magnetic field. Based on the models, a simple method of designing and optimizing the EMA coil pair according to technical specifications, was proposed. A loop-shaped coil pair generating uniform magnetic and gradient fields was chosen to demonstrate this method clearly and practically. The results of the optimization showed that the best distance to radius ratio of a loop-shaped coil pair is 1.02 for a uniform magnetic field and 1.75 for a uniform gradient field. The applicability of the method to other shapes of coil configuration was also illustrated. The best width to distance ratio for a square-shaped coil pair is 0.558 and 0.958 for uniform magnetic and gradient fields, respectively. The best height to width ratio and distance to width ratio for a rectangle-shaped coil pair is h/w = [0.9,1.1], d/w = [0.5,0.6] for uniform magnetic field and h/w = [1.0,1.2], d/w = [0.9,1.1] for uniform gradient field. Furthermore, simulations of a microparticle tracking the targeted trajectory were conducted to analyze the performance of the newly designed coils. The simulations suggested the ability of manipulating microparticles via the coils designed by our proposed method. The research mainly proposed a unified design and optimization method for a coil pair, which can support researchers while designing a specific coil pair according to the technical requirements. This study is aimed at researchers who are interested in EMA system and microrobots.