Odhad tvaru čela únavové trhliny s pomocí exponentu singularity napětí

Fatigue crack shape prediction based on the stress singularity exponent

článek v časopise - ostatní, Jost

en

In many industrial applications it is necessary to predict fatigue lifetime of the structures, where the stress field near the crack front have a real three-dimensional nature. Due to the existence of vertex singularity in the point where the crack front touches free surface, crack propagation in 3D structures cannot be reduced to a series of plane strain or plane stress problems along the crack front. The paper describes the influence of the vertex singularity on crack shape for three-dimensional structure. The iterative process for estimation of a real crack front based on a stress singularity exponent is presented. The crack front was approximated by a spline curve. In each node defining the crack front the stress singularity exponent has been estimated and complete crack front shape was found. The methodology presented can help to estimate crack front shape in a linear elastic fracture mechanics framework and estimate fracture parameters of fatigue cracks more accurately.

V práci je numericky odhadnut skutečný tvar čela trhliny v inženýrských konstrukcí. Vlivem blízkosti volného povrchu dochází ke změně charakteru singulární napjatosti. Samotnou napjatost v okolí čela trhliny na volném povrchu pak nelze popsat klasicky pomocí součinitele intenzity napětí. V těchto případech je možné použít metodiku odhadu tvaru čela trhliny pomocí exponentu singularity napětí. Je zde ukázáno, že úhel mezi čelem trhliny a normálou k volnému povrchu, odhadnutý pomocí popsaného postupu, je ve velmi dobré shodě s daty dostupnými v literatuře.

In many industrial applications it is necessary to predict fatigue lifetime of the structures, where the stress field near the crack front have a real three-dimensional nature. Due to the existence of vertex singularity in the point where the crack front touches free surface, crack propagation in 3D structures cannot be reduced to a series of plane strain or plane stress problems along the crack front. The paper describes the influence of the vertex singularity on crack shape for three-dimensional structure. The iterative process for estimation of a real crack front based on a stress singularity exponent is presented. The crack front was approximated by a spline curve. In each node defining the crack front the stress singularity exponent has been estimated and complete crack front shape was found. The methodology presented can help to estimate crack front shape in a linear elastic fracture mechanics framework and estimate fracture parameters of fatigue cracks more accurately.

exponent singularity napětí; zakřivení čela trhliny; rohová singularita; vliv volného povrchu

stress singularity exponent; crack front curvature; vertex singularity; free surface effect

2012

02.01.2012

Trans Tech Publications

Switzerland

1013-9826

488-489

-

178–181

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