Ultrasonic Measurement of Crack Depth in Thick-Walled Cylinders

摘要

Fatigue testing of heavy-walled cylinders by cyclic internal pressure produces cracks in the bore. A program to study the propagation of these cracks required a non-destructive inspection technique to locate cracks and measure their depth at frequent intervals during testing. Watervliet Arsenal has developed an unusual method of ultrasonic inspection to perform this function using the sound energy reflected from a crack tip. An evaluation of the sensitivity of detection and accuracy of measurement of cracks is presented. Scanning the outside diameter of the cylinder with an ultrasonic normal-probe produces a response that can be readily interpreted in terms of crack depth, location, length and orientation. The method has also been successfully applied in the inspection of cannon tubes. Experience to date is limited to high strength steel cylinders with cracks 0.050 to 2.000 in. deep. However, with additional development, the technique offers possible application to other materials and configurations. At present all inspections are made and data recorded manually but an automatic system appears feasible and is currently under development. (Author)