ON THE CALIBRATION, OPTIMIZATION AND USE OF d.c. ELECTRICAL POTENTIAL METHODS FOR MONITORING MODE III CRACK GROWTH IN TORSIONALLY‐LOADED SAMPLES

— The use of d.c. electrical potential methods is described for the monitoring of Mode III (anti‐plane shear) fatigue cracks in circumferentially‐notched cylindrical specimens subjected to cyclic torsion. Calibration of potential change with crack depth and optimization of current input and potential measurement probe locations are achieved using simple finite element procedures, and are verified experimentally. The use of the method for Mode III crack growth studies is described in the light of crack face electrical shorting problems associated with torsional crack closure.