Theory Of Stage II Fatigue Crack Propagation

Item

Title
Theory Of Stage II Fatigue Crack Propagation
Date
1965
Index Abstract
Not Available
Photo Quality
Not Needed
Report Number
AFML TR 64-415
Creator
Grosskreutz, J. C.
Corporate Author
Midwest Research Inst Kansas City MO
Laboratory
AF Materials Laboratory
Extent
21
Identifier
AD0464816
Access Rights
Export Control
Distribution Classification
1
Contract
AF 33(657)-10883
DoD Project
7353 - Characterization of Solid Phase and Interphase Phenomena in Crystalline Structures
DoD Task
735301
DTIC Record Exists
Yes
Distribution Change Authority Correspondence
AFML LTR
Abstract
A continuum model of crack extension is used to derive a crack propagation law for the case of constant plastic strain amplitude fatigue. The rate of crack growth is found to be proportional to the square root of the crack length. Integration over the total number of cycles to failure, N sub f, yields an expression of the form N sub f(delta epsilon sub p bar to the n+1 power = f(delta epsilon sub p bar), where delta epsilon sub p bar is the applied plastic strain range, and f is a function which varies rapidly in the region of large strains, but approaches a constant as delta epsilon sub p bar becomes small. The strain hardening coefficient, n, and the fracture strain enter as material constants. Comparison with experimental data gives good agreement for delta epsilon sub p bar > or = 0.01, which is consistent with the assumptions used in the theory. A discussion is given which interprets the well known power law N sub f to the 1/2 power times delta epsilon sub p bar = const. in terms of crack propagation.
Report Availability
Full text available
Date Issued
1965-03
Provenance
Lockheed Martin Missiles & Fire Control
Type
report
Format
1 online resource
Media
AFMLTR64-415.pdf