Exam2A_10pages - Do all Probfems (1 05/1 00 Total Points)...

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Unformatted text preview: Do all Probfems (1 05/1 00 Total Points) (1 extra credit for 10 points) Write your answers below the question on this paper. lf extra room is required use the back of the page on which a specific question resides. 8-1 (1 0 pts) a) Using a stress-strain hardening means. diagram, xplain what "strain Exam 2a Name: f{ .v MSEG 302 IA v) Q) t{ (h o (n I cn (e) (d) . tjgr* .$ . Development of strain hardening from the stress_strain diagram. (a) A specimen is stressed beyond th" ri"1d,_r!lg,ngtl, before th-e .ii.r. L iurirro tb) Now the specimen has a h igher yield strength and tensi te-strength, Ori f"*"i O,.iiiiiy. rc, by repeatt ng the procedure, the strength continues to increase.and ttri or.iiritv.ontin-ri.io o""r""r. untir the aloy becomes very brittle' (d) Note the-total^strain ano ttr-e ttjitrc itiii-n-L.ou"rv read to remnant prastic strain and (e) if tustration of sprin-gback. fsor*, n"giiiJ iiffineering Matriats t, S&ond Edition, M.F. Ashbey, and D.R.H. Jone, ti . cowtjst?t:t:) l6xiii"dElln"r*"rn. Reprin4d with pemision frcm Elsevier Science.) b) Explain why many metallic materials exhibit strain hardening. We obtain strengthening during deformation of a metallic material by increasing the number of dislocations. Before deformation, the dislocation density is about 106 cm of dislocation line per cubic centimeter of metal - a relatively small concentration of dislocations. When stress that is greater than the yield strength is applied dislocations begin to slip. The dislocation density may increase to about 10" cm of dislocation line per cubic centimeter of metal during strain hardening. The result is an increased strength, but reduced ductility, for metallic materials that have undergone cold working or work hardening. grotat Permanent plastic detbrmation 9-2 (10 pts) Suppose that liquid nickel is undercooled until homogeneous nucleation occurs. Calculate (a) the critical radius of the nucleus required, and (b) the number of nickel atoms in the nucleus....
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This note was uploaded on 02/01/2012 for the course MSEG 302 taught by Professor Snively during the Spring '08 term at University of Delaware.

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Exam2A_10pages - Do all Probfems (1 05/1 00 Total Points)...

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