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37. Identify the three sources of contraction in a metal casting after pouring. 38. Why should turbulent flow of molten metal into the mold be avoided? 39. What are some of the factors that affect the fluidity of a molten metal during pouring into a mold cavity? 40. How does solidification of alloys differ from solidification of pure metals? 41. What is a chill in casting? What are the differences between bulk deforma- tion processes and sheet metal processes? Extrusion is a fundamental shaping process. De- scribe it. 42. Why is the term pressworking often used for sheet metal processes? 43. What is the difference between deep drawing and bar drawing? 44. How does increasing temperature affect the pa- rameters in the flow curve equation? 45. Indicate some of the advantages of cold working relative to warm and hot working. 46. Describe the effect of strain rate in metal forming. 47. Why is friction generally undesirable in metal forming operations? 48. What are the reasons why the bulk deformation processes are important commercially and technologically? 49. Name the four basic bulk deformation processes. 50. What is rolling in the context of the bulk deforma- tion processes?