This preview shows pages 1–3. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Unformatted text preview: Bonus Homework Assignment 5 points Metal Forming 18.11 A tensile test is carried out to determine the strength constant C and strain rate sensitivity exponent m for a certain metal at 1000 F. At a strain rate = 10/sec, the stress is measured at 23,000 lb/in 2 ; and at a strain rate = 300/sec, the stress = 45,000 lb/in 2 . (a) Determine C and m . (b) If the temperature were 900 F, what changes would you expect in the values of C and m ? Solution : (a) Two equations: (1) 23,000 = C (10) m and (2) 45,000 = C (300) m 45,000/23,000 = 1.9565 = (300/10) m = (30) m ln 1.9656 = m ln 30 0.67117 = 3.4012 m m = 0.1973 (1) C = 23000/10 0.1973 = 23000/1.5752 = 14,601.4 (2) C = 45000/300 0.1973 = 45000/3.0819 = 14,601.4 C = 14,601.4 (b) If temperature were decreased to 900 F, the strength constant C would increase and the strainrate sensitivity exponent m would decrease. 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 = 200/100 = 2.0 s1 (b) strain rate = 200/75 = 2.667 s1 (c) strain rate = 200/51 = 3.922 s1 Bulk Deformation 19.20 A hydraulic forging press is capable of exerting a maximum force = 1,000,000 N. A cylindrical workpart is to be cold upset forged. The starting part has diameter = 30 mm and height = 30 mm. The flow curve of the metal is defined by K = 400 MPa and n = 0.2. Determine the maximum reduction in height to which the part can be compressed with this forging press, if the coefficient of friction = 0.1. Use of a spreadsheet with this forging press, if the coefficient of friction = 0....
View Full
Document
 Fall '08
 Groover

Click to edit the document details