The manufacturer of a product that is subjected to repetitiv

The manufacturer of a product that is subjected to repetitive cycles has specified that the product should be removed from service when any crack reaches 15% of the critical crack length required to cause fracture. Consider a crack that is initially 0.02 mm long in a material with a fracture toughness of 55 MPa m. The product is continuously cycled between compressive and tensile stresses of 300 MPa at a constant frequency. Assume external cracks for which f = 1.12. The materials constants for these units are n = 3.4 and C = 2 × 10–11. What is the critical crack length required to cause fracture

Solution

solution

critical crack length = 1 / ( K / Y )²

= 0.00853 m

= 8.53 mm