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Oct 22nd 2013, 00:33, by bootslive

作者bootslive (liveboots)

看板ask

標題[請問] 材料動力學題目

時間Tue Oct 22 00:33:11 2013

※ [本文轉錄自 Grad-ProbAsk 看板 #1IPL980L ] 作者: bootslive (liveboots) 看板: Grad-ProbAsk 標題: [理工] 材料動力學 時間: Tue Oct 22 00:11:49 2013 有沒有學過材料動力學的高手可以幫忙解題！ 想了很久還是解不出來啊，萬分感謝！ A steel bar, 25 cm long and 1 cm in diameter contains carbon in the amount of 0.15 wt%. A thin layer of carbon, 10^-4 moles/cm^2, is deposited upon one end of the bar which is then annealed at a temperature of 1200K. (1) How long will it take for the composition of the bar to reach 0.25 wt% at a depth of 150 *10^-6m from the carbon coated end, the first time? (10 wt%) (2) Derive an expression for the velocity of the concentration front = 0.25%. Comment on the direction of motion of this front at short time and long time. ( 5 wt %) (3) How long will it take for the composition of the bar to drop back down to 0.25 % carbon at a depth of 150*10^-6m from the carbon coated end? 再次感謝大大Q_Q -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 220.137.85.52 ※ 發信站: 批踢踢實業坊(ptt.cc) ※ 轉錄者: bootslive (220.137.85.52), 時間: 10/22/2013 00:33:11

→ mautshic0218:連diffusivity、density都沒有給 當然解不出來XD 10/22 01:07

→ mautshic0218:這題滿經典的 幫你補充data:Dc=2x10^-7 (cm^2 s^-1) 10/22 01:10

→ mautshic0218:ρ=0.25 (g cm^-3) 10/22 01:11

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