Fracture Mechanics

FE-model of a crack on a bearing shell
FE-model of a crack on a bearing shell 		Beside static strength and fatigue analyses, also fracture mechanical play problems an important role in a component assessment. For instance, cracks arising within the material during the manufacturing process can lead to fracture of the component under specific load conditions.

Using the J-integral concept is one at ASD‘s practised methods for estimation of crack propagation. The J-integral, a line integral with closed integration path around the crack tip, is used as the fracture criterion. Commercial FE-software packages provide the possibility to calculate the J-integral along the crack tip considering the stress concentration factors for the different crack opening modes, Young‘s modulus and Poisson‘s ratio.
The critical J-integral value can be calculated from experimentally determined material property values for fracture toughness and can be compared with the numerically calculated value of the specific problem. If this value is smaller than the critical J-integral value it can be assumed that there is no crack growth under static load.
The practise for estimation of dynamic crack propagation is very similar. The range of J-integral, hence the difference between minimum and maximum value of a dynamic load is compared with the critical material value for the dynamic load. Calculated J-integral value along the crack tip
Calculated J-integral value along the crack tip
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