Fatigue crack closure

W. Elber, The Significance of Fatigue Crack Closure , Damage Tolerance in Aircraft Structures, ASTM STP 486, 1971, pp. 230 242. 

S. Suresh and R. O. Ritchie, A Geometric Model for Fatigue Crack Closure Induced by Fracture Surface Morphology , Metallurgical Transactions, 13A, 1982, pp. 1627 1631. 

N. Walker and C. J. Beevers, A Fatigue Crack Closure Mechanism in Titanium , Fatigue of Engineering Materials and Structures, Wo[. 1, 1979, pp. 135 148. 

C. J. Beevers, R. L. Carlson, K. Bell and E. A. Starke, A Model for Fatigue Crack Closure , Engineering Fracture Mechanics. 

Thompson, R. B., Fiedler, C. J., and Buck, O. (1984). Inference of fatigue crack closure stresses from ultrasonic transmission measurements. In Nondestructive methods for materials property determination (ed. C. O. Ruud and R. B. Thompson), pp. 161-70. Plenum Press, New York. [278]... 

The mechanisms of fatigue crack closure have been identified for metals. These are illustrated by Anderson [16], who has also expanded upon the effects of crack closure on the fatigue properties of metals. The phenomenon can also manifest itself in polymer-based materials because of the plastic deformation, viscoelasticity, residual stresses, and environmental conditions. 

Mechanics of Fatigue Crack Closure, ASTM STP 982, J. C. Nevraran and W. Elber, Eds., ASTM International, West Conshohocken, PA, 1988. 

Fiber, W. The significance of fatigue crack closure. ASTM STP 486, 230-242 (1971)... 

One aspect of pressure vessel design which has received considerable attention in recent years is the design of threaded closures where, due to the high stress concentration at the root of the first active thread, a fatigue crack may quickly initiate and propagate in the radial—circumferential plane. Stress intensity factors for this type of crack are difficult to compute (112,113), and more geometries need to be examined before the factors can be used with confidence. 

Crack extension is often observed to vary significantly at the same nominal value of AK (= Y AOpos Tta) for different values of R-ratio. Elber [26] was the first to explain this observation for metals in terms of the crack closure phenomenon. He determined, by measuring specimen compliance, that fatigue cracks open and close at the crack tip at positive values of stress due to contact between crack surfaces behind the crack tip. For elastic fatigue conditions it is generally found that P p = P, and Kop = K, where P is the applied load. 

Several criticisms of these parameters have recently been pointed out. First, they have no specific association with a material plane (i.e., they are scalar parameters), despite the fact that cracks are known to nucleate on specific material planes. With traditional parameters it is difficult to account for the effects of crack closure under compressive loading. Traditional parameters have not been successful at unifying experimental results for simple tension and equibiaxial tension fatigue tests. Finally, a nonproportional loading history can always be constmcted for a given scalar equivalence parameter that holds constant the value of the scalar parameter, but which results in cyclic loading of material planes. For such histories, scalar parameters incorrectly predict infinite fatigue life. 

In order to accurately model the fatigue behavior of rubber, fatigue analysis methods must account for various effects observed for rubber during constant amplitude testing. Effects associated with load level, 7 -ratio (ratio of minimum to maximum loading level), and crack closure are presented in this section. 

Bardal E, Eggen TG, Grovlen MK. A quantitative determination of crack closure effects on fatigue properties of cathodically protected steel in sea water. In Scott P, Cottis RA, editors. Environment-assisted Fatigue. EGF Publication 7, London Mech Eng Publ, 1990. 

Dauskardt, R.K., Yu, W., and Ritchie, R.O. (1997) Mechanism of cyclic fatigue crack propagation in a flne grained alumina ceramic the role of crack closure. Fatigue Fract. Eng. Mater. Struct., 20, 1453-1466. 

Fig. 7.27 Experimental techniques used to measure cyclic fatigue-crack growth rates showing a compact C(T) specimen and procedures used to monitor crack length and the stress intensity, Kq, at crack closure for long cracks, and b cantilever-beam specimen and semi-elliptical surface crack configuration for corresponding tests on small cracks [5]. With kind permission of John Wiley and Sons...

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