3. (15 pts) The S/N endurance curve for an A517 steel plate is shown below and it corresponds to50% survival rate. The tensile strength of the steel equals 700 MPa.

a. Determine the fatigue/endurance limit (place it also on the plot). b. If subjected to a cyclic stress featuring a mean stress of 200 MPa, calculate the maximum allowable stress amplitude (oa) corresponding to ơao as found in (a) above. c. For the life expectancy N (# of cycles to failure)stress when the stress amplitude is 240 MPa.= 105, calculate the allowable mean