Dimensioning pre-cracked components under static loads

3 Dimensioning pre-cracked components under static loads 

In sections 3.3.1 to 3.3.3 and 3.5.2, failure criteria for plastic deformation and cleavage fracture were introduced. If a component contains a crack, it has to be designed to avoid crack propagation as well. A component with a known crack length a can resist a given stress a only if 

If the component is loaded cyclically or at elevated temperatures, further failure criteria have to be considered that will be discussed in chapters 10 and 11. 

If the crack length is larger than the critical crack length, the material can be expected to fail by crack propagation. The critical crack length is thus given by 

Although the critical crack length is an indicator of the crack sensitivity of a material, it is not a material parameter. This can be seen directly from equation (5.28) which contains the geometry factor Y. For this reason, analytically calculating Oc is frequently impossible. 

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