Accession Number : AD0666187

Title :   SOME FRACTOGRAPHIC OBSERVATION OF FATIGUE CRACK GROWTH IN MARAGING STEEL,

Corporate Author : FRANKFORD ARSENAL PHILADELPHIA PA PITMAN-DUNN RESEARCH LABS

Personal Author(s) : Carman,Carl M. ; Schuler,Mary F.

Report Date : NOV 1967

Pagination or Media Count : 39

Abstract : The fatigue crack propagation rates of 250 and 300 grade maraging steel were determined using two programming techniques: (1) cycling at a constant stress, and (2) cycling at a constant value of K. The rate of fatigue crack propagation was determined using macroscopic and electron fractographic methods, and the results were plotted as a function of cyclic K. Test results, using both methods, exhibited a fourth power relationship, as proposed by Paris. Both techniques, macroscopic and microscopic, yielded the same propagation rate. Previously, fractographic studies of maraging steels have not revealed the presence of fatigue striations. However, this investigation has shown the presence of fatigue striations, fatigue steps and slopes, slip band cracks associated with fatigue striations, tire tracks, ductile rupture dimples, and cleaved particles. The various features observed on the fatigue surface are discussed in terms of the mechanisms which are responsible for their formation. (Author)

Descriptors :   (*MARAGING STEELS, FRACTURE(MECHANICS)), CRACK PROPAGATION, FATIGUE(MECHANICS), ELECTRON MICROSCOPY, STRESSES, FRACTOGRAPHY, RUPTURE, DUCTILITY, PLASTIC PROPERTIES, DEFORMATION, PHOTOMICROGRAPHY, SURFACE PROPERTIES, DEFECTS(MATERIALS)

Subject Categories : Metallurgy and Metallography

Distribution Statement : APPROVED FOR PUBLIC RELEASE