ASTM E2884-22 PDF

SIGNIFICANCE AND USE 5.1 Eddy current methods are used for nondestructively locating and characterizing discontinuities and geometric property variations in magnetic or nonmagnetic electrically conducting materials. Conformable eddy current sensor arrays permit examination of planar and non-planar materials but usually require suitable fixtures to hold the sensor array near the surface of the material of interest, such as a layer of foam behind the sensor array along with a rigid support structure. 5.2 In operation, the sensor arrays are standardized with measurements in air or a reference part, or both. Responses measured from the sensor array may be converted into physical property values, such as lift-off, electrical conductivity, or magnetic permeability, or a combination thereof. Proper instrument operation is verified by ensuring that these measurement responses or property values are within a prescribed range. Performance verification is performed periodically. Performance verification on a discontinuity-free reference standard or regions of the material being examined that do not contain discontinuities ensures that the electrical and geometric properties, such as electrical conductivity, layer thickness, or lift-off, or a combination thereof, are appropriate for the sensor array. Performance verification on a discontinuity-containing reference standard ensures that the sensor array response to the discontinuity is appropriate. 5.3 The sensor array dimensions, including the size and number of sense elements, and the operating frequency are selected based on the type of examination being performed. The depth of penetration of eddy currents into the material under examination depends upon the frequency of the signal, the electrical conductivity and magnetic permeability of the material, and some dimensions of the sensor array. The depth of penetration is equal to the conventional skin depth at high frequencies but is also related to the sensor array dimensions at low frequen... SCOPE 1.1 This guide covers the use of conformable eddy current sensor arrays for nondestructive examination of electrically conducting materials for discontinuities and material quality. The discontinuities include surface breaking and subsurface cracks and pitting as well as near-surface and hidden-surface material loss. The material quality includes coating or layer thickness, electrical conductivity, magnetic permeability, surface roughness, and other properties that vary with the electrical conductivity or magnetic permeability. 1.2 This guide is intended for use on nonmagnetic and magnetic metals as well as composite materials with an electrically conducting component, such as reinforced carbon-carbon composite or polymer matrix composites with carbon fibers. 1.3 This guide applies to planar as well as non-planar materials with and without insulating coating layers. 1.4 Units—The values stated in SI units are to be regarded as standard. The values given in parentheses are mathematical conversions to inch-pound units that are provided for information only and are not considered standard. 1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.