Question

Question 8 (1 point) Which of the following best describes the physical conditions that determine if a crack will propagate as described by the Griffith criterion? O A crack will propagate if the strain is larger than the necking strain. O A crack will propagate if the strain energy released is smaller than the free surface energy created by the crack opening. O A crack will not propagate unless the stress applied is greater than the yield strength of the material. O A crack will propagate if the strain energy released is larger than the free surface energy created by the crack opening

Answer 1

The best description is option (B). Answer(B)

I am pretty sure of the answer. Please dear thumpsup for the answer. Thank you.

According to Griffith's criterion, the crack will propagate under a constant applied stress o if an incremental increase in crack length produces no change in the total energy of the system; i.e. the increased surface energy is compensated by a decrease in elastic strain energy. DAU de =0 AU = total change in potential energy resulting from the AU - U + UE creation of the crack which is equal to U = the surface energy due to presence of the crack is → U, 407, Ur= the elastic strain energy per unit of the plate thickness is equal to Where o is the tensile stress acting normal to the crack of the length and a negative sign is used because growth of the crack releases elastic strain energy → de-o-lev. - ) → --(267)