A round bar, 20 mm in diameter, has a shallow circumferential notch with a depth with a root radius  .The bar is made of a low carbon steel with a yield strength of  . It is loaded axially with a nominal stress,  (the axial load divided by the un-notched area). At what value of will yield first commence at the root of the notch? Use the stress concentration estimate of Appendix B9 to find out.

Data From Appendix B9

c = 1 mm