A tension member made of 2014-T651 aluminium has a dimensions of b= 30 and t=4mm. A safety factor of 3.0 against failure by either brittle fracture or fully plastic yielding is required.
(A) if there is a through-thickness crack in one edge of length a=6mm, what is the highest tension force P that can be permitted in service.
(B) if the force in service is P=6.0 KN, what is the largest crack length that can safely exist in the member ?