1. Scope
1.1 This practice provides guidelines for acoustic emission (AE) examinations of nonpressure paper machine rolls. 1.2 This practice uses a slow rotation of the roll to produce a full load cycle in which load is provided by the weight of the roll suspended from its bearings or other journal support mechanism(s). 1.3 The desired source of the acoustic emission (AE) is frictional crack face rubbing associated with opening and closing of existing cracks. 1.4 The AE measurements are used to detect or locate or both emission sources. Other nondestructive test (NDT) methods shall be used to evaluate the significance of AE sources. Procedures for other NDT techniques are beyond the scope of this practice. See NOTE 1. NOTE 1-Traditional AE examination, magnetic particle examination, shear wave ultrasonic examination, and radiography are commonly used to establish circumferential position and dimensions of flaws that produce AE. 1.5 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with the standards. 1.6 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 and health practices and determine the applicability of regulatory limitations prior to use. Specific precautionary statements are given in Section 8.
Fatigue crack growth, if undetected, can lead to catastrophic failure of a paper machine roll within a matter of weeks. Roll failure can cause extensive damage to the paper machine and physical harm to personnel. Removal of rolls for traditional NDT examination may be impractical and may not be sensitive enough to locate small fatigue cracks. If the roll cannot be removed or follow-up NDT examination cannot confirm an AE indication or both, this procedure may be repeated to confirm the existence of the indication. Traditional AE examination, whereby the roll is subjected to load greater than service load to detect crack extension, risks damage to the roll and is best used as a follow-up NDT examination. Unlike traditional AE examination, which is subject to the Kaiser effect, the crack closure technique is repeatable.
Keywords
acoustic emission; paper machine rolls; fatigue crack growth
The title and scope are in draft form and are under development within this ASTM Committee.
Citing ASTM Standards
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