2. A bar with rectangular cross-section is loaded in three-point bending (as shown in (i)) with a central load of P = 8000 lb. The crack length is 2 inch. a. Determine the stress intensity factor K, for this configuration. b. If the same bar is subjected to four-point-bending with P = 8000 lb as shown in (ii), what would be the stress intensity factor K, for this configuration. c. By drawing the shear force and bending moment diagrams for the two beams, show that the crack in four-point-bending is under pure bending while that in three-point-bending is under bending and shear. d. For the four-point-bending case, the exact location of the crack (on the bottom surface) is immaterial (i.e., we get the same SIF) as long as it is within the inner loading points A and B. Explain why? (i) (ii) A P 30 in 10 in B 5 in 2 in 5 in 2 in