Use of Microelectromechanical Systems Technologies to Sensitively Measure and Monitor Stress Corrosion Crack Propagation, 18-9342Printer Friendly Version
Inclusive Dates: 08/01/02 - Current
Background - Many engineering structures are subjected to the simultaneous conditions of an applied stress (or load) and a corrosive environment. Under these conditions, numerous cases of structural failures from stress corrosion cracking (SCC) have been reported in boilers, pressure vessels, oil and gas production and transmission piping, components associated with nuclear power generation, bridges, sea craft, and aircraft. There are a number of experimental methods to determine SCC susceptibility and measure crack propagation rates. One of the main limitations of these methods is that the crack propagation rate detection limit of 10-11 m/s is often too high to gage if SCC may lead to component failure over the long term. Extending the test time to overcome this limitation can become prohibitively expensive. The second limitation with the existing methods is that they cannot easily be converted and implemented as sensors or monitoring methods. The goal of this project is to develop MEMS (Microelectromechanical Systems) devices using structural engineering materials for sensitive crack growth rate measurements and to do so in such a way as to facilitate SCC sensing and monitoring.
Approach - The operating principle of this project is to construct MEMS devices that utilize structural materials or analogues for the study of SCC. High sensitivity to low crack propagation rates is achieved using small SCC members in combination with traditional crack monitoring methods and microscopic examination.
Accomplishments - To date, SCC test members in the form of double cantilever beams (Figure 1) and notched single cantilever beams have been fabricated from engineering alloys (Cu-Zn) using the MEMS process. In addition, initiation and propagation of SCC have been observed in several devices. This marks the first successful attempt to fabricate such devices using structural engineering materials and inducing SCC.