AN ELECTRIC-POTENTIAL DROP TECHNIQUE FOR CHARACTERIZING PART-THROUGH SURFACE CRACKS

The development and verification of fracture criteria - including catastrophic failure and leak-before-break phenomena - are important to the assessment of fusion reactor structural integrity. Reliable assessments will require appropriate measures to characterize the initiation, stable growth and instability of part-through surface cracks in thin-walled structures. This paper describes procedures we are developing for monitoring the evolution of part-through cracks using electropotential drop techniques. A calibration between potential drops across multiple probes placed across the crack plane and crack size and shape was developed for aluminum and 410 steel specimens. The calibration technique was then successfully applied to monitor surface crack growth in an HT-9 specimen.