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pa3_Sept30_09 - stress free B A large ceramic component...

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AERO3700 PA 3 September Introductory Material and Quiz Wednesday September 30, 238 TB Quiz in last 30 minutes Purpose: Familiarization and review of properties, behaviour and fracture using notes and textbook. Callister 6.29 a,b,c,d,f : a (plot), b (E = 50 GPa), c (0.2% offset is about 140 MPa), d (UTS is about 230 MPa), f (%El is about 10.7%), 6.35 (derive), 6.37 (true strain is .311), 8.4 (a= 0.79 mm), 8.5 (critical stress is 1380 MPa), read 8.6 and note how Y can be different in certain cases, 8.7 (134 MPa), 8.9 (2a = 0.0041 m) A . The coefficient of linear thermal expansion for Al is 23.6 x10 -6 o C -1 . If an initially stress free rod, 200 mm long, 10 mm diameter rod is heated from 20 to 120 o C, what are the length and diameter of the rod at 120 o C? What is the stress state of the rod at 120 o C (Ans . lf= 200.47 mm, df = 10.02 mm, if the expansion is free expansion the rod will be
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Unformatted text preview: stress free) B. A large ceramic component with E = 300 GPa and K IC = 2.5 MPa m 1/2 is a candidate for an application in which it must be cooled quickly from 900 o C to 25 o C. There is a central crack (through-thickness) of 2a =5 mm in the component (assume Y = 1). Using your knowledge of fracture mechanics and thermal stress, thermal strain and thermal shock, estimate the coefficient of thermal expansion that the ceramic must have to survive this cooling. (Ans . About 0.1x10-6 o C-1 ) Using the Properties Table B.6 (p. A19) in Callister, determine if it is likely that a ceramic with the estimated coefficient of thermal expansion exists? (Ans . Fused silica is the closest but the other commercial ceramics do not qualify) C . Why does the engineering stress-strain curve drop off after the UTS? M. McDill September 2009 AERO3700 - PA3...
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