two steels are being considered for manufacture of as-forged connecting rods subjected to bending loads. one is aisi 4340 cr-mo-ni steel capable of being heat-treated to a tensile strength of 260 kpsi. the other is a plain carbon steel aisi 1040 with an attainable sut of 113 kpsi. each rod is to have a size giving an equivalent diameter de of 0.75 in. determine the endurance limit for each material. is there any advantage to using the alloy steel (i.e. aisi 4340) for this fatigue application?