Validation of a method for generating controlled fatigue cracks for calibration of non‐destructive test techniques

Increased reliability of results obtained in defect detection by non‐destructive testing (mainly ultrasonic) can only be achieved by using, for calibration and approval procedures, steel blocks of specified geometric shapes similar to the shapes submitted for examination, containing defects perfectly defined with respect to size and location (PISC Programme III). The present article describes some applications to real situations in which defects of different size and geometric shape were generated in testpieces with different shapes and materials. The method used to obtain these defects was crack propagation by fatigue starting from a machined notch. Crack growth was monitored by continuous measurement of testpiece compliance, which can be unambiguously related to crack depth.