Thickness-Independent Ultrasonic Imaging Applied To Abrasive Cut-Off Wheels: An Advanced Aerospace Materials Characterization Method For the Abrasives Industry A Nasa Lewis Research Center Technology Transfer Case History

摘要

Abrasive cut-off wheels are at times unintentionally manufactured with nonuniformity that is difficult to identify and sufficiently characterize without time-consuming, destructive examination. One particular nonuniformity is a density variation condition occurring around the wheel circumference or along the radius, or both. This density variation, depending on tis severity, can cause wheel warpage and wheel vibration resulting in unacceptable performance and perhaps premature failure of the wheel. Conventional nondestructive evaluation methods usch as ultrasonic c-scan imaging and film radiography are inaccurate in their attempts at characterizing the density variation because a superimposing thickness varition exists as well in the wheel. As shown in figure 1 and explained in detail in ref. 1., the single transducer thickness-independent ultrasonic imaging method ref.2), developed specifically to allow more accurate characterization of aerospace components, is shown to precisely characterize the extent of hte density variation in a cut-off wheel having a superimposing thickness variation. Figure 1 compares for hte cut-off wheel a conventional pulse-echo ultrasonic c-scan peak amplitude image (B1 gated), an apparent velocity image, a film radiograph, and a thickness-independent ultrasonic velocity image. All figures also show line profiles of the NDE property at a horizontal position near the center of the corresponding image of the wheel. Also shown is the edge-to-edge thickness profile of the wheel at a lien through a center portion of the wheel.