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Unformatted text preview: Homework #6: Due on December 4th at midnight through the course web site. The solution will be posted the day after so that you can check your answers before the exam. • Chapter 18 problems: 18.2, 18.13 • Chapter 19 problems: 19.3, 19.19, 19.22, 19.30 (given rx =5.068) • Chapter 20 problems: 20.2, 20.5, 20.9, 20.10, 20.28 Chapter 18: 18.2 A metal has a flow curve with parameters: strength coefficient = 850 MPa and strainhardening exponent = 0.30. A tensile specimen of the metal with gage length = 100 mm is stretched to a length = 157 mm. Determine the flow stress at the new length and the average flow stress that the metal has been subjected to during the deformation. Solution : ε = ln (157/100) = ln 1.57 = 0.451 Flow stress Y f = 850(0.451) 0.30 = 669.4 MPa. Average flow stress f Y = 850(0.451) 0.30 /1.30 = 514.9 MPa. 18.13 A workpart with starting height h = 100 mm is compressed to a final height of 50 mm. During the deformation, the relative speed of the plattens compressing the part = 200 mm/s. Determine the strain rate at (a) h = 100 mm, (b) h = 75 mm, and (c) h = 51 mm. Solution : (a) strain rate ε1 = 200/100 = 2.0 s1 (b) strain rate ε1= 200/75 = 2.667 s1 (c) strain rate ε1= 200/51 = 3.922 s1 Chapter 19: 19.3 A series of cold rolling operations are to be used to reduce the thickness of a plate from 50 mm down to 25 mm in a reversing twohigh mill. Roll diameter = 700 mm and coefficient of friction between rolls and work = 0.15. The specification is that the draft is to be equal on each pass. Determine (a) minimum number of passes required, and (b) draft for each pass? number of passes required, and (b) draft for each pass?...
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This note was uploaded on 12/07/2009 for the course E ISE 515 taught by Professor Olaharryson during the Fall '09 term at N.C. State.
 Fall '09
 OlaHarryson
 Process Engineering

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