(Solved): Show that the stress ratio, R=\sigma mi(n)/(\sigma )max, is uniquely defined if the mean stress an ...

Show that the stress ratio,

, is uniquely defined if the mean stress and stress amplitude are specified. And then plot the schematic of crack length-number of cycles relationship for a fixed

but for different values of the stress amplitude. Explain why. (You can refer to the following sample we discussed during lecture, which shows crack length-number of cycles relationship for a fixed stress amplitude but for different values of R.)