4. The resistance curve

The resistance curve of a brittle material fits the expression:

where K, and ß are material parameters. Consider the effects of small cracks in a body

designed to carry a fixed stress level o. Assume that the stress intensity factor is given

by:

(a) Obtain the critical crack size ac for initiation.

(b) Determine the relationship between Ko and B to ensure that this critical crack is

stable.

(c) Discuss the implication of increasing Ko.

(d) Discuss the implication of increasing B.

(e) Discuss the implication of increasing the design stress