Accession Number : AD0762608

Title :   Nondestructive Evaluation of Metal Fatigue.

Descriptive Note : Scientific rept. 1972-1973,

Corporate Author : SOUTHWEST RESEARCH INST SAN ANTONIO TEX DEPT OF INSTRUMENTATION RESEARCH

Personal Author(s) : Kusenberger,F. N. ; Ko,W. L. ; Lankford,J. , Jr. ; Francis,P. H. ; Barton,John R.

Report Date : APR 1973

Pagination or Media Count : 58

Abstract : The complementary role of nondestructive evaluation (NDE) methods in the application of fracture mechanics approaches for preventing catastrophic failures in engineering structures and extending the useful life of critical components is discussed. Observations via metallurgical investigations of the early stages of macrocrack propagation at inclusions in AISI 4340 steel are described. A model is proposed which is consistent with the early phases of crack front propagation observed and the dormant period in surface crack-extension heretofore observed in steels by others. Precycle magnetic signatures from inclusions are analyzed and the results presented show a functional relationship between signal amplitude and life to crack initiation. Experiments in the local removal of fatigue cracks show that significant extensions in fatigue life are possible through such 'rework' and that subsequent crack initiation occurs at a location different from that corresponding to prior crack removal. Magnetic signatures from a fatigue crack at several intervals during propagation are presented. (Modified author abstract)

Descriptors :   (*STEEL, *NONDESTRUCTIVE TESTING), MAGNETIC PROPERTIES, FRACTURE(MECHANICS), CRACK PROPAGATION, ULTRASONIC RADIATION, RAYLEIGH WAVES, FATIGUE(MECHANICS)

Subject Categories : Metallurgy and Metallography

Distribution Statement : APPROVED FOR PUBLIC RELEASE