ASTM E2884-13
使用整合传感器阵列的导电材料涡流检测的标准指南

Standard Guide for Eddy Current Testing of Electrically Conducting Materials Using Conformable Sensor Arrays

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标准号

ASTM E2884-13

发布

2013年

发布单位

美国材料与试验协会

替代标准

ASTM E2884-13e1

当前最新

ASTM E2884-22

 

 

适用范围

5.1 Eddy current methods are used for nondestructively locating and characterizing discontinuities 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 and/or a reference part. Responses measured from the sensor array may be converted into physical property values, such as lift-off, electrical conductivity, and/or magnetic permeability. Proper instrument operation is verified by ensuring that these measurement responses or property values are within a prescribed range. Performance verification on reference standards with known discontinuities is performed periodically.

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 frequencies, such as the size of the drive winding and the gap distance between the drive winding and sense element array. For surface-breaking discontinuities on the surface adjacent to the sensor array, high frequencies should be used where the penetration depth is less than the thickness of the material under examination. For subsurface discontinuities or wall thickness measurements, lower frequencies and larger sensor dimensions should be used so that the depth of penetration is comparable to the material thickness.

5.4 Insulating layers or coatings may be present between the sensor array and the surface of the electrically conducting material under examination. The sensitivity of a measurement to a discontinuity generally decreases as the coating thickness and/or lift-off increases. For eddy current sensor arrays having a linear drive conductor and a linear array of sense elements, the spacing between the drive conductor and the array of sense elements should be smaller than or comparable to the thickness of the insulating coating. For other array formats the depth of sensitivity should be verified empirically.

5.5 Models for the sensor response may be used to convert responses measured from the sensor array into physical property values, such as lift-off, electrical conductivity, magnetic permeability, coating thickness, and/or substrate thickness. For determining two property values, one operational frequency can be used. For nonmagnetic materials and examination for crack-like discontinuities, the lift-off and electrical conductivity should be determined. For magnetic materials, when the electrical conductivity can be measured or assumed constant, then the lift-off and magnetic permeability should be determined. The thickness can only be determined if a sufficiently low excitation frequency is used where the depth of sensitivity is greater than the material thickness of interest. For determining more than two property values, measurements at operating conditions having at least two depths of penetration should be used; these different de...........

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