Development of a Test Device Utilizing a Practical Nondestructive Test Technique to Detect Fatigue Damage in Metals and Alloys

摘要

Nondestructive magnetic field inspection techniques were evaluated for the detection of fatigue damage in steel tubing. Methods of magnetizing the specimens as well as methods for measuring magnetic field perturbations were investigated. Design and evaluation of an ultrasonically driven search coil type probe for measuring field perturbations are described. This probe and a solenoid type magnetizing coil were evaluated using a specimen containing manufactured defects as well as specimens which were stress cycled. A pronounced signal change was obtained on a stress cycled specimen prior to the propagation of a visible crack. A smooth increase of signal amplitude with increasing stress cycles was observed. Many examples of the inspection records and a discussion of the results obtained are given. The probe and magnetizing techniques were incorporated into the design of a semi-automatic experimental device for detecting fatigue damage in steel tubing. Fabrication, assembly, and initial operational evaluation of the device have been completed. A photograph and description of the device are presented. (Author)