Digital Wave Corporation | Company Profile

Digital Wave Corporation - Company Profile

Dr. Michael Gorman, after spending several years at the rocket motor manufacturer Hercules (now Alliant Tech) and having used conventional AE to monitor composite rocket motor proof tests, realized that the narrowband filtering and resonant sensors used in conventional AE were eliminating the wave mode characteristics needed to identify sources. He left Hercules to pursue research into the improvement of acoustic emission technology.

In 1985 he began first principles research into the relationship between source orientation and the wave mode excited in typical engineering structures. He later published the results in the seminal paper "Acoustic Emission Orientation by Plate Wave Analysis,"¹ for which he was awarded the Acoustic Emission Working Group's (AEWG) publication award in 1997. His place as the discoverer of the relationship between the source orientation and the wave modes produced was cemented in 1999 by the AEWG's highest discovery and invention award, the Joseph Kaiser Achievement Award, for the discovery of modal AE.

In 1992 he formed Digital Wave Corporation, designing modal AE equipment around the research results obtained over the prior seven years. This resulted in the development of the highly successful Fracture Wave Detector line of equipment. Digital Wave equipment could now discriminate between noise sources and flaw growth events using Newton's laws. This idea was further elucidated by Dr. Ulf Goranson, former Head of Structures at Boeing, in his paper titled "Jet Transport Structures Performance Monitoring,"² wherein he states:

'Classical' AE data consists of various parameters intended to represent the AE waveform. The parameters characterizing a given waveform are not necessarily unique to that waveform and could be the same for other waves generated by other types of sources.

Modal AE is much like seismology, where the wave modes produced by earthquakes are used to determine the source of the earthquake; thus, the modal AE approach eliminates the non-uniqueness problem pointed out by Dr. Goranson.

Digital Wave Corporation takes great pride in being the only true practitioner of modal acoustic emission. Our analysts are highly trained in wave propagation theory and have extensive experience in testing and modal AE data analysis. They understand the subtle, yet important relationships between structure, source orientation, signal frequency content, and wave mode to identify flaw growth signals and eliminate noise. While other AE companies are still performing "research" into the use of modal AE, Digital Wave has been successfully implementing the technique for more than 12 years.

In addition to the modal AE technology developed by Digital Wave, the company also began designing and manufacturing ultrasonic scanning systems for the examination of DOT high-pressure gas cylinders in 2001. The UE-1 cylinder scanner is the most capable system on the market for requalifying DOT cylinders. The system is a full-immersion scanner with a high degree of accuracy and repeatability. Unlike scanners that contact the cylinder, the non-contact nature of Digital Wave's patented immersion system allows for more efficient and persistent calibration.

Please email or call Digital Wave for more detailed look at how modal AE can be applied to your specific inspection needs or if you would like further information about the UE-1 cylinder scanner. Customer references are enthusiastically supplied.

Notes

1. M.R. Gorman and W.H. Prosser, Journal of Acoustic Emission 9 (1990) (4): 283-288.

2. U.G. Goranson, Structural Health Monitoring: Current Status and Perspectives, Proceedings of the International Workshop on Structural Health Monitoring, Stanford University, ed. F.K. Chang, Boca Raton, FL: CRC Press (1997): 3-17.