E 127 reference standards

The ASTM E 127 "Standard Practice for Fabricating and Checking Aluminum Alloy Ultrasonic Standard Reference Blocks" was developed to assure consistent ultrasonic measurement of suspected discontinuities in wrought aluminium alloy product. The E127 practice established a consensus methodology for the manufacture, metrological limits and ultrasonic response limits from flat bottom hole (FBH) references manufactured in accordance with the practice. This paper will present a brief history of the development of the standard along with problems encountered in the earliest publications. The early issues were resolved, but as instrumentation and materials changed, problems have again arisen with the consistency of the results. Over the past 20+ years the authors have uncovered the causes of many of the inconsistencies associated with establishing measurement that match the original values prescribed in the practice. Over the years, a multitude of measurements were made on various reference standards covering a ma...