John Conway explores new techniques in nondestructive testing through ASNT fellowship

Emily Scott

Graduate student John Conway is pursuing new areas of research in nondestructive testing and evaluation through a prestigious fellowship from the American Society for Nondestructive Testing (ASNT).

Conway, who is completing his master’s degree in systems and entrepreneurial engineering, is working on using nondestructive methods to detect high temperature hydrogen attack in carbon steel pressure vessels, an important problem in the industry.

Some carbon steel pressure vessels hold hydrogen gas at high partial pressures and at high temperatures. Hydrogen can diffuse into the steel and bond with carbon in the steel, which creates methane — this is the problem known as high temperature hydrogen attack.

Because methane can’t diffuse out of the steel, small microbubbles of high pressure methane become stuck within the steel. The high pressure environment can cause these high-pressure microbubbles to grow and combine with each other to form larger cracks in the vessel.

Conway’s research, which continues previous research by Professor Henrique Reis and ISE Ph.D. graduate Megan McGovern, is focusing on using new techniques to detect these microbubbles before they become a problem.

Traditionally, a method called linear ultrasonics is used to detect the location of cracks in the vessel after they are formed. This method involves sending a sound wave through the vessel that then reflects off the crack, pinpointing the crack’s location based on the speed of sound.

Conway’s research proposes using nonlinear ultrasonics instead — sending in two sound waves that interact with each other to produce a third wave whose amplitude is proportional to the non-linearity of the material and the methane microbubbles that form before large cracks develop.

“The idea is to detect these microbubbles before they become problematic cracks,” Conway said. “If you can measure these non-linear waves at varying points along the thickness of a steel pressure vessel, you can characterize the damage within the pressure vessel wall based upon the received nonlinear scattered wave.”

Conway said this method has previously not been used in this way to detect high temperature hydrogen attack.

“No one is really doing this, which is interesting in itself, just to be doing something unique,” he said.

He hopes his research can be a part of potential solutions to what is a real and serious problem in industry.

“You could have a steel vessel with high temperature and high pressure hydrogen, which could catastrophically fail without much warning,” Conway said. “There’s certainly a risk there, and companies need to be aware of this mode of failure because it could lead to loss of property and life.”

Additionally, he hopes his research could contribute to future applications — perhaps an all-encompassing device that could quickly assess damage in vessels before it becomes a problem.

“The idea that your research could lead somewhere is interesting,” he said.

As part of his ASNT fellowship, Conway will produce a publication for the society, which is funding his work.

“It’s nice to be recognized by a national society for my research,” he said.

Conway plans to complete his graduate studies this year, and hopes to someday work in an industrial research position in systems engineering.

“I’m looking at a wide range,” he said. “That’s part of the benefit of this department — it gives you a wide breadth in terms of your career options.”

He said working with Professor Reis, his advisor, and fellow students in his lab have made for a beneficial experience in his studies.

“I’ve been surrounded by intelligent people and I’ve been able to benefit from that, and that’s why I like it.”

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