ASTM E1816-12
Standard Practice for Ultrasonic Testing Using Electromagnetic Acoustic Transducer (EMAT) Techniques

Standard No.

ASTM E1816-12

Release Date

2012

Published By

American Society for Testing and Materials (ASTM)

Status

Be replaced

Replace By

ASTM E1816-18

Latest

ASTM E1816-18(2022)

Scope

5. Significance and UseTop Bottom

5.1 Since EMAT techniques are noncontacting, they should be considered for ultrasonic examinations in which applications involve automation, high-speed examinations, moving objects, applications in remote or hazardous locations, and applications to objects at elevated temperatures or objects with rough surfaces. This practice describes procedures for using EMAT techniques as associated with the ultrasonic method to detect flaws for both surface and volumetric examinations as well as to measure thickness.

5.2 The uniqueness of the electromagnetic acoustic transducer technique for ultrasonic examination basically lies in the generation and reception of the ultrasonic waves. Otherwise, conventional ultrasonic techniques and methodologies generally apply.

5.3 An EMAT generates and receives acoustic waves in a material by electromagnetic means; electrically conductive or ferromagnetic materials can be examined. In its simplest form, an EMAT as a generator of ultrasonic waves is basically a coil of wire, excited by an alternating current, and placed in a uniform magnetic field near the surface of a material. For conductive materials, eddy currents are induced as a result of the alternating current. Due to the magnetic field, these eddy currents experience Lorentz forces that in turn are transmitted to the solid by collisions with the lattice or other microscopic processes. These forces are alternating at the frequency of the driving current and act as a source of ultrasonic waves. If the material is ferromagnetic, additional coupling mechanisms play a part in the generation of ultrasonic waves. Interactions between the dynamic magnetic field generated by the alternating currents and the magnetization associated with the material offer a source of coupling, as do the associated magnetostrictive influences. Reciprocal processes exist whereby all of these mechanisms lead to detection. Fig. 3 depicts the mechanisms (forces), along with associated direction, for electromagnetic ultrasound generation.

Note 1???j8201;=8201;current in a single conductor, Bo8201;=8201;magnetization from external magnet, Fm8201;=8201;magnetic force (ferromagnetic material), Fms8201;=8201;magnetostrictive force (ferromagnetic material), and FL8201;=8201;Lorentz force (conductive material).

FIG. 3 Mechanisms of Electromagnetic Ultrasound Generation

5.4 The EMAT can be used to generate all ultrasonic modes of vibration. As with conventional ultrasonic techniques, material types, probable flaw locations, and flaw orientations determine the selection of beam directions and modes of vibration. The use of EMATs and selection of the proper wave mode presuppose a knowledge of the geometry of the object; the probable location, size, orientation, and reflectivity of the expected flaws; the allowable range of EMAT lift-off; and the laws of physics governing the propagation of ......

ASTM E1816-12 Referenced Document

• ASTM E114 Standard Practice for Ultrasonic Pulse-Echo Straight-Beam Examination by the Contact Method
• ASTM E1316 Standard Terminology for Nondestructive Examinations
• ASTM E1774 Standard Guide for Electromagnetic Acoustic Transducers (EMATs)
• ASTM E494 Standard Practice for Measuring Ultrasonic Velocity in Materials
• ASTM E543 Standard Practice for Agencies Performing Nondestructive Testing
• ASTM E587 Standard Practice for Ultrasonic Angle-Beam Contact Testing
• ASTM E797 Standard Practice for Measuring Thickness by Manual Ultrasonic Pulse-Echo Contact Method

ASTM E1816-12 history

• 2022 ASTM E1816-18(2022) Standard Practice for Measuring thickness by Pulse-Echo Electromagnetic Acoustic Transducer (EMAT) Methods
• 2018 ASTM E1816-18 Standard Practice for Measuring thickness by Pulse-Echo Electromagnetic Acoustic Transducer (EMAT) Methods
• 2012 ASTM E1816-12 Standard Practice for Ultrasonic Testing Using Electromagnetic Acoustic Transducer (EMAT) Techniques
• 2007 ASTM E1816-07 Standard Practice for Ultrasonic Testing Using Electromagnetic Acoustic Transducer (EMAT) Techniques
• 1996 ASTM E1816-96(2002) Standard Practice for Ultrasonic Examinations Using Electromagnetic Acoustic Transducer (EMAT) Techniques
• 1996 ASTM E1816-96 Standard Practice for Ultrasonic Examinations Using Electromagnetic Acoustic Transducer (EMAT) Techniques