1Printed name: On my honor, I pledge that I have neither received nor provided improper assistance in the completion of this quiz. Signature: GEORGIA INSTITUTE OF TECHNOLOGY George W. Woodruff School of Mechanical Engineering ME 4210 MANUFACTURING PROCESSES AND ENGINEERING Fall 2009 Quiz #1 September 28 Be sure to list all assumptions. Write legibly. One, two sided page of hand-written notes is allowed; it must be handed in with your worked solutions (put your name on your sheet of notes). Otherwise, the exam is closed book and notes. This exam is 50 minutes long. Use the data provided with the test for all calculations. Show your work and write your answers in the exam in the space after the questions. You may write on both sides of the paper.2Problem #1 (10 points; short answer) The Biot number is given by hl/k, where h is the heat transfer coefficient, l is the characteristic heat transfer length, and k is the conductivity of the metal being cast. Explain why and how the Biot number is used to determine whether or not a casting mold is considered conducting. Note: I am not interested in the limits of the value of the Biot number per se, but rather what those values tell you is happening - the physics of the situation. Your answer to Problem #1:3Problem #2 (10 points; short answer) Discuss why the recrystallization point is selected as the boundary between the use of strain hardening and strain rate material models. Your answer to Problem #2:Problem You are cbelow). basin is 2its meltinheat to th• C• IfthNote: I huse the c #3 (40 pointcasting a solThe cylinder25 cm in elevng temperatuhe mold. ThCalculate the f the bottom he diameter’have providedorrect ones. ts) lid aluminumr has a diamvation aboveure. You mahe atmospherconservativof the sprues maximum d separate m m cylinder inmeter of 10 cme the gate of ay assume thre’s temperave, allowablee, the runner value. material prop 4n a bottom-gm and a heigfthe mold. That the entireature is 35 C.e pouring timand the gateperties for roogated sand mght of 10 cmThe aluminue surface area. me as constrae each has thom and molt mold (see figum. The top ofum is poureda of the cylinained by heahe same diamten temperature and dataf the pouringd at 200 C abnder transferat transfer. meter, determtures; be surg bove rs mine re to5Material properties for Casting: Data for solid materials (room temperature) Material Specific heat (kJ/kg-oC) Density (kg/m3) Thermal conductivity (W/m-oC) Sand 1.16 1500 0.60 Aluminum 0.90 2700 222 Nickel 0.44 8910 92.1 Magnesium 1.03 1740 154 Copper 0.38 8960 394 Iron 0.46 7870 75.4 Steel 0.434 7832 59 Data for liquid materials at their melting points Material Melting point (oC) Density (kg/m3) Latent heat of solidification (fusion) (Hf) (kJ/kg) Thermal conductivity (W/m-oC) Specific heat (C) (kJ/kg-oC) Viscosity (m) (mPa-s) Aluminum 660 2390 396 94 1.05 4.5 Nickel 1453 7900 297 0.73 4.1 Magnesium 650 1585 384 139 1.38 1.24 Copper 1083 7960 220 49.4 0.52 3.36 Iron 1537 7150 211 0.34 2.26Your answer to Problem #3: (continue on back of sheet)7Problem #4 (40 points) You are open die forging a cylindrical part with an initial diameter of 200 cm and an initial height of 500 cm at 1100 C. The part has a final diameter of 258 cm and a final height of 300 cm. The coefficient of friction is 0.65. The metal being forged has a melting temperature of 1500 C. The metal has K = 960 MPa, n = 0.1, C = 160 MPa, and m = 0.07. The press closes at 18 m/min. • Determine which material model that you will use (strain hardening or strain rate). • For a safety factor of 3, determine the yield stress of the platens. Your answer to Problem #4: (continue on back of
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