The effect of microstructure on the mode of monotonie fracture, fatigue crack initiation, and stage i crack growth in an
- PDF / 3,917,044 Bytes
- 10 Pages / 594 x 774 pts Page_size
- 25 Downloads / 220 Views
I.
INTRODUCTION
STRUCTURAL alloys suitable for high temperature application are varied, but austenitic stainless steels are extensively used because of their good heat resisting properties. These steels when used as structural components undergo microstructural change over a period of time at temperature and when subjected to monotonic or cyclic loading may fail prematurely. Under cyclic stresses or strains fatigue damage results from the localized continuous to and fro dislocation motion] part of which is nonreversible. The extent of this motion and the nonreversibility depend on the monotonic strength and ductility of the material. It is now generally accepted that fatigue damage initially occurs in the surface layers2'3'4 and leads subsequently to initiation of a fatigue crack(s). One method of assessing the fatigue damage sustained by a material is to generate a cyclic response curve (Figure 1). Under the strain control mode of cyclic deformation, this curve is a plot of changing stress amplitude vs number of applied cycles. The two common cyclic responses observed in materials are cyclic hardening and cyclic softening. During cyclic hardening, the stress amplitude increases as the number of cycles increases, whereas the opposite effect occurs during cyclic softening. It is not uncommon for a M Z. SHAH KHAN, formerly a Postgraduate Student, School of Materials Science and Engineering, University of New South Wales, Kensington, New South Wales 2033, is Research Scientist, Australian Defence Science and Technology Organlsation, Materials Research Laboratories, P.O. Box 50, Ascot Vale, Victoria 3032, Australia K. R L THOMPSON is Senior Lecturer, School of Materials Science and Engineering, University of New South Wales, Kensington. New South Wales 2033, Austraha. Manuscript submitted July 4, 1986 METALLURGICAL TRANSACTIONS A
i
Data Loading...
