The Naval Ship Systems Engineering Station, Naval Surface Warfare Center Carderock Division (NAVSSES) in Philadelphia recently began a new testing process that drastically speeds up the aging of ship components, allowing engineers to test the long-term effects of a shipboard environment, saving both time and money.
The Material Conditioning Test Site uses pressure and heat to speed the aging process of polymers from years or decades down to potentially just a few months. The test site can emulate environmental factors such as heat, pressure or exposure to chemicals such as the chemical composition of seawater or hydraulic fluid that can cause unwanted cracking, fluid absorption or chemical disintegration of the polymer.
“The general ‘rule-of-thumb’ is for every 10-degree Celsius temperature increase of the polymer in the liquid, the aging time is doubled,” said Dr. Debbie Kenney, mechanical engineer and test site manager from Machinery Technology Research and Development Branch at NAVSSES.
If a polymer normally operates in a liquid at 50 degrees Celsius – during one hour of normal operation the polymer will age one hour. If instead the polymer is held at 60 degrees Celsius for one hour, the polymer will “age” roughly two hours during the one-hour time span. If the polymer is held at 70 degrees Celsius (a 20 degree Celsius elevation above normal operating temperature) for one hour, the polymer “ages” roughly four hours during the one hour.
In the Carderock Division’s Non-Metallic Materials Research and Engineering Branch in West Bethesda, Maryland, mechanical engineer Joe Korczynski ages sample ship material for evaluation to help understand the actual accelerated aging relationship with the polymer he is testing.
“There is a limitation on how fast we can accelerate the aging of the polymer material at elevated temperature if the exposure temperature and pressure damage the microstructure of the polymer,” said Korczynski.
The process helps engineers take the guesswork out of when a component may fail, allowing them to replace an aging component proactively without having to wait for it to fail or break.
“This test site will help us determine the service life of many components aboard Navy vessels. We can then be prepared to replace ship components when, and even before, failures occur,” said Kenney.
[mappress] Press Release, May 30, 2014; Image: navsea.navy.mil