In the construction of a large reactor pressure vessel, a new steel alloy with a plane strain fracture toughness of 55 MPa-m1/2 and a Y value of 1.0. An in-service stress level of 200 MPa has been calculated. What is the length of a surface crack (in mm) that will lead to fracture

A200-mm wide strip 25 mm thick is fed through a rolling mill w/two powered rolls each of radius = 250 mm. the work thickness is to be reduced to 22 mm in one pass at a roll speed of 60 rev/min. the average flow stress of the work material, as it passes through the rolls is 175 mpa. the friction coefficient between rolls and work material is 0.20. 1, determine a)-if friction is sufficient for rolling. b)- if friction is sufficient: c)- calculate roll force i calculate roll torque. d)- calculate roll power.