ISSN 2594-5327
52º Congresso anual — Vol. 52 , num. 1 (1997)
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At the relatively low design stress levels permitted in initially cracked structural components, tensile overloads cause local yielding at the crack tip which increases the crack closure level and decreases the post overload crack growth rate. Underloads cause only a small decrease in crack closure and crack growth rate. However, at the much higher load stress levels associated with the initiation and growth of cracks from notches, both tensile and compressive overloads typically cause local stresses of the order of the yield stress. These stresses cause drastic reductions in the crack closure level and a large acceleration in crack growth. This paper examines the use of a modified "short crack fracture mechanics" together with a crack closure model to describe the growth of small cracks in notches. Analytical and experimental methods of determining steady-state and transient crack closure are reviewed together with empirical crack closure models. An alternate method of determining crack growth and crack closure parameters from fatigue test data is also described. Examples are given of the application of short crack fracture mechanics and crack closure models to describe the growth of cracks from notches under variable amplitude loading. They accurately predict the increased severity of small notches in variable amplitude fatigue compared to conventional predictions based on constant amplitude data. The prediction method is also shown to give good fatigue life predictions for service load histories applied to notched specimens.
At the relatively low design stress levels permitted in initially cracked structural components, tensile overloads cause local yielding at the crack tip which increases the crack closure level and decreases the post overload crack growth rate. Underloads cause only a small decrease in crack closure and crack growth rate. However, at the much higher load stress levels associated with the initiation and growth of cracks from notches, both tensile and compressive overloads typically cause local stresses of the order of the yield stress. These stresses cause drastic reductions in the crack closure level and a large acceleration in crack growth. This paper examines the use of a modified "short crack fracture mechanics" together with a crack closure model to describe the growth of small cracks in notches. Analytical and experimental methods of determining steady-state and transient crack closure are reviewed together with empirical crack closure models. An alternate method of determining crack growth and crack closure parameters from fatigue test data is also described. Examples are given of the application of short crack fracture mechanics and crack closure models to describe the growth of cracks from notches under variable amplitude loading. They accurately predict the increased severity of small notches in variable amplitude fatigue compared to conventional predictions based on constant amplitude data. The prediction method is also shown to give good fatigue life predictions for service load histories applied to notched specimens.
Palavras-chave
small cracks, crack closure, crack growth, overload, fatigue, notched specimens
small cracks, crack closure, crack growth, overload, fatigue, notched specimens
Como citar
Topper, T. H.; Dabayeh, A. A.; Lam, T. S..
The Effect of Overloads on Small Cracks, Crack Closure and Crack Growth,
p. 4335-4354.
In: 52º Congresso anual,
São Paulo, Brasil,
1997.
ISSN: 2594-5327, DOI 10.5151/2594-5327-C00276-4335-4354
