18.15. (USCS units) A cylindrical work part with diameter 2.5 in, and height = 2,5 in is upset forged in an open die to a height -1.5 in. Coefficient of

friction at the die-work interface = 0.10. The work metal has a strength coefficient - 40,000 lb/in' and strain hardening exponent - 0.15. Yield strength-15,750 lb/in',Determine the instantaneous force in the operation (a) just as the yield point is reached (yield at strain -0.002), (b) at height h- 2.3 in, (c) h= 2.1 in,