Evaluation of MFS Electrochemical Fatigue Sensor System by Iowa State University
The electrochemical fatigue sensor (EFS) was developed to detect very small fatigue cracks that are actively growing. To evaluate the fatigue crack capabilities and gain a better understanding of implementation needs, a laboratory test and a field monitoring program were developed to evaluate the EFS system using the CrackChek and FatigueWatch sensors, respectively. The laboratory test program consisted of evaluating the adequacy of CrackChek sensors for crack detection. The CrackChek sensors were installed on a standard steel plate specimen. An electrical discharge machining (EDM) notch was induced in the mid-length of the steel plate and a pair of sensors (i.e., crack and reference sensors) were installed adjacent to the notch tip. The field monitoring program consisted of evaluating the adequacy of the FatigueWatch sensors for crack detection and the general capabilities of the system for use in field applications. The sensors were installed on the Cherry Creek Bridge near Newton, Iowa, on a sacrificial specimen and on a bridge girder web in a known fatigue-sensitive location. The sacrificial specimen was a standard steel plate exactly the same as the one used for evaluating the CrackChek sensors. The EDM notch was also generated in the edge and mid-length of the specimen and a pair of sensors were installed near the notch tip. After a 13-month data collection and analysis period, no crack formed in either the sacrificial specimen or the bridge girder web where the sensors were installed. In summary, the CrackChek and FatigueWatch sensors perform well for crack detection.