EMATs for Science and Industry

EMATs for Science and Industry
Author: Masahiko Hirao
Publisher: Springer Science & Business Media
Total Pages: 372
Release: 2013-04-17
Genre: Science
ISBN: 1475737432

EMATs for Science and Industry comprises the physical principles of electromagnetic acoustic transducers (EMATs) and the applications to scientific and industrial ultrasonic measurements on materials. The text is arranged in four parts: -PART I is intended to be a self-contained description of the basic elements of coupling mechanism along with practical designing of EMATs for various purposes. There are several implementations to compensate for the low transfer efficiency of the EMATs. Useful tips to make an EMAT are also presented. -PART II describes the principle of electromagnetic acoustic resonance (EMAR), which makes the most of contactless nature of EMATs and is the most successful amplification mechanism for precise velocity and attenuation measurements. -PART III applies EMAR to studying the physical acoustics. New measurements emerged on three major subjects; in situ monitoring of dislocation behavior, determination of anisotropic elastic constants, and acoustic nonlinearity evolution. -PART IV deals with a variety of individual topics encountered in industrial applications, for which the EMATs are believed to the best solutions.

Electromagnetic Acoustic Transducers

Electromagnetic Acoustic Transducers
Author: Masahiko Hirao
Publisher: Springer
Total Pages: 382
Release: 2016-10-25
Genre: Technology & Engineering
ISBN: 443156036X

This second edition provides comprehensive information on electromagnetic acoustic transducers (EMATs), from the theory and physical principles of EMATs to the construction of systems and their applications to scientific and industrial ultrasonic measurements on materials. The original version has been complemented with selected ideas on ultrasonic measurement that have emerged since the first edition was released. The book is divided into four parts: PART I offers a self-contained description of the basic elements of coupling mechanisms along with the practical designing of EMATs for various purposes. Several implementations to compensate for EMATs’ low transfer efficiency are provided, along with useful tips on how to make an EMAT. PART II describes the principle of electromagnetic acoustic resonance (EMAR), which makes the most of EMATs’ contactless nature and is the most successful amplification mechanism for precise measurements of velocity and attenuation. PART III applies EMAR to studying physical acoustics. New measurements have emerged with regard to four major subjects: in situ monitoring of dislocation behavior, determination of anisotropic elastic constants, pointwise elasticity mapping (RUM), and acoustic nonlinearity evolution. PART IV deals with a variety of individual issues encountered in industrial applications, for which the EMATs are believed to be the best solutions. This is proven by a number of field applications.

Electromagnetic Acoustic Transducer

Electromagnetic Acoustic Transducer
Author:
Publisher:
Total Pages:
Release: 1988
Genre:
ISBN:

A noncontact ultrasonic transducer for studying the acoustic properties of a metal workpiece includes a generally planar magnetizing coil positioned above the surface of the workpiece, and a generally planar eddy current coil between the magnetizing coil and the workpiece. When a large current is passed through the magnetizing coil, a large magnetic field is applied to the near-surface regions of the workpiece. The eddy current coil can then be operated as a transmitter by passing an alternating current therethrough to excite ultrasonic waves in the surface of the workpiece, or operated as a passive receiver to sense ultrasonic waves in the surface by measuring the output signal. The geometries of the two coils can be varied widely to be effective for different types of ultrasonic waves. The coils are preferably packaged in a housing which does not interfere with their operation, but protects them from a variety of adverse environmental conditions.

Electromagnetic Acoustic Transducer Analysis

Electromagnetic Acoustic Transducer Analysis
Author: Reza Jafari
Publisher: LAP Lambert Academic Publishing
Total Pages: 164
Release: 2011-10
Genre:
ISBN: 9783846532706

Electromagnetic acoustic transducers (EMATs) are non-contact, non-destructive testing devices for conducting specimens. The efficiency of EMATs is inherently low and methods for increasing it have been the subject of intense research. In publications, the finite element (FE) technique has been applied to the diffusion equation in order to model EMATs. However, electromagnetic theory indicates that the diffusion equation must be solved for the magnetic vector potential (MVP) in conjunction with an equation for the total current. An existing FE formulation considering the two equations becomes unstable when modeling transient inputs in EMAT transmitters. The limitation posed by the instability prompted the development of an improved FE formulation, which solves the two equations and is suitable for the modeling of EMATs.The objective of the research work described in this thesis is to properly and accurately model EMATs, so that their efficiency could be improved at the design stage. The thesis describes the governing equations of EMATs, improved techniques for their solution, and the application of these techniques to the analysis of such devices.

Electromagnetic-acoustic Transducers

Electromagnetic-acoustic Transducers
Author: R. E. Beissner
Publisher:
Total Pages: 43
Release: 1976
Genre: Electroacoustic transducers
ISBN:

This report is a brief review of those aspects of electromagnetic-acoustic generation and detection of interest in nondestructive evaluation (NDE). Since this is a developing technology, there are no standard transducer designs and practices. The principles of ultrasonic wave generation as related to electromagnetic-acoustic transducer (EMAT) design are emphasized. EMATs are of interest in NDE because they offer a completely noncontacting technique for generating and detecting ultrasonic waves. The report discusses theory, experimental studies, design, and applications of EMATs. (Author).

EMAT (Electromagnetic-Acoustic Transducer) System for Ultrasonic Velocity

EMAT (Electromagnetic-Acoustic Transducer) System for Ultrasonic Velocity
Author:
Publisher:
Total Pages: 45
Release: 1989
Genre:
ISBN:

An EMAT system has been designed and constructed which can be used for wall thickness measurements on steel tubes with surface temperatures up to 650 C and for measurements of residual stress near to the inner surface of a 120 mm gun barrel. The system consists of an EMUS (Electromagnetic-Ultrasonic) transmitter/receiver instrument, a high temperature Electromagnetic-Acoustic Transducer (EMAT) for wall thickness measurements with normally incident shear waves using the pulse-echo-technique and a device consisting of one transmitting EMAT and two receiving EMATs which are collinearly integrated into a mechanical support for the transduction of Rayleigh waves that are travelling along the circumferential direction on the inner surface of a 120 mm gun tube.