Acylindrical part is warm upset forged in an open die. the starting work piece is 50 mm in diameter, and 40 mm in hieght. the final height=20mm. coefficent of friction at the die-work interface =0.2. the work material has a flow curve defined by k=600 mpa, and n=0.12. determine the force in the operation at process begins, at intermediate height of 30 mm, and at the final height of 20 mm.