HW3 Sol (corrected)

HW3 Sol (corrected) - UCLA MAE 183 HW#3 Solutions Fall 2010...

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1 UCLA MAE 183 HW#3 Solutions – Fall 2010 Review Q 10.1: Identify some of the important advantages of shape casting processes. Answer . (1) Complex part geometries are possible; (2) some casting operations are net shape processes, meaning that no further manufacturing operations are needed to accomplish the final part shape; (3) very large parts are possible; (4) they are applicable to any metal that can be melted; and (5) some casting processes are suited to mass production. Review Q 10.2: What are some of the limitations and disadvantages of casting? Answer . (1) Limitations on mechanical strength properties; (2) porosity; (3) poor dimensional accuracy; (4) safety hazards due to handling of hot metals; and (5) environmental problems. Review Q 10.13: How does solidification of alloys differ from solidification of pure metals? Answer . Pure metals solidify at a single temperature equal to the melting point. Most alloys (exceptions are eutectic alloys) start to solidify at the liquidus and complete solidification occurs at the solidus, where the liquidus is a higher temperature than the solidus. Review Q 10.16: Identify the three sources of contraction in a metal casting after pouring. Answer . (1) Contraction of the molten metal after pouring, (2) solidification shrinkage during transformation of state from liquid to solid, and (3) thermal contraction in the solid state. Multiple Choice Q 10.7: During solidification of an alloy when a mixture of solid and liquid metals is present, the solid-liquid mixture is referred to as which one of the following: (a) eutectic composition, (b) ingot segregation, (c) liquidus, (d) mushy zone, or (e) solidus? Answer . (d). Multiple Choice Q 10.8: Chvorinov's Rule states that total solidification time is proportional to which one of the following quantities: (a) ( A / V ) n , (b) H f , (c) T m , (d) V , (e) V / A , or (f) ( V / A ) 2 ; where A = surface area of casting, H f = heat of fusion, T m = melting temperature, and V = volume of casting? Answer . (f). Prob. 10.1: A disk 40 cm in diameter and 5 cm thick is to be cast of pure aluminum in an open mold casting operation. The melting temperature of aluminum = 660 ° C and the pouring temperature will be 800 ° C. Assume that the amount of aluminum heated will be 5% more than what is needed to fill the mold cavity. Compute the amount of heat that must be added to the metal to heat it to the pouring temperature,
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This note was uploaded on 02/11/2011 for the course MAE 183 taught by Professor Cjkim during the Fall '10 term at UCLA.

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HW3 Sol (corrected) - UCLA MAE 183 HW#3 Solutions Fall 2010...

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