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Aerospace Engineering

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Oct 30, 2023

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MAE 183A: Spring Quarter 2023 Last Name First Name Page 1 of 2 Homework Assignment #02: Due Tuesday, April 18, 2023 Multiple Choice: MC6.1: A binary phase diagram indicates the phases of two elements (at least one of which is metallic) as a function of composition and temperature at atmospheric pressure? (a) true (b) false MC6.2: The inverse lever rule is used to determine which of the following in a binary phase diagram? (a) the compositions of the solid and liquid phases, (b) the proportions of each phase present at a given temperature, (c) the temperatures of the solidus and liquidus for a given composition MC6.3: As the carbon content of plain carbon steel is increased, its strength and hardness (a) decreases, (b) increases, or (c) stays the same? MC7.1: Which of the following are properties associated with ceramic materials? (a) chemical stability, (b) electrically conductive, (c) good ductility, (d) high hardness, (e) soluble in water, (f) thermally insulating MC7.2: Which of the following properties and characteristics of glass ceramics are important? (a) efficiency in processing, (b) electrical conductor, (c) high thermal expansion, (d) strong relative to other glasses MC8.1: The long-chain molecules in a polymer such as polyethylene are held together by which type(s) of bonding? (a) covalent, (b) ionic, (c) metallic, (d) van der Waals and other secondary bonding MC8.2: Which of the following methods are used for the synthesis of polymers (a) addition polymerization, (b) copolymerization, (c) cross polymerization, (d) natural polymerization, (e) step polymerization, (f) synthetic polymerization, (g) thermoplastic polymerization, (h) thermosetting polymerization MC8.3: As the degree of crystallinity in a polymer increases, its properties are affected in which of the following ways? (a) density decreases, (b) density increases, (c) melting temperature decreases, (d) melting temperature increases, (e) stiffness decreases, (f) stiffness increases MC9.1: Anisotropy is defined by which of the following? (a) composite materials with compositions consisting of more than two materials, (b) properties are the same in every direction, (c) properties vary depending on the direction in which they are measured, (d) strength and other properties are a function of curing temperature MC9.2: Which of the following metals are used as matrix metals in tungsten carbide and titanium carbide cermets: (a) aluminum, (b) chromium, (c) cobalt, (d) lead, (e) nickel, (f) vanadium MC9.3: Ceramic matrix composites are designed to overcome which weaknesses of ceramics? (a) compressive strength, (b) hardness, (c) hot hardness, (d) modulus of elasticity, (e) tensile strength, (f) toughness MC5.1: Which of the following best describes a tolerance? (a) clearance between a shaft and a mating hole, (b) measurement error, (c) total permissible variation from a specified dimension, (d) variation in manufacturing MC5.2: When a tolerance is specified in both positive and negative directions from a nominal dimension, what it is called? (a) bidirectional tolerance, (b) bifurcated tolerance, (c) bilateral tolerance, (d) limit tolerance, (e) symmetrical tolerance MC5.3: Which of the following manufacturing processes is likely to result in the best surface finish? (a) arc welding, (b) grinding, (c) milling, (d) sand casting, (e) sawing MC10.1 To allow for shrinkage that occurs in during solidification, the mold cavity must be: (a) oversized or (b) undersized? MC10.2 What is total solidification time defined as? (a) time between pouring and complete solidification, (b) time between pouring and cooling to room temperature, (c) time between solidification and cooling to room temperature, (d) time to give up heat of fusion

MAE 183A: Spring Quarter 2023 Last Name First Name Page 2 of 2 MC11.1 Why is a green mold called “green”? (a) green is the color of the mold, (b) moisture is contained in the mold, (c) the mold is cured, (d) the mold is dry MC11.2 The power generated by a certain heating furnace is 200 kW and its thermal efficiency = 40%. The unit energy for melting and pouring for the casting metal = 800 J/g, and the total weight of the metal to be heated in the furnace = 50 kg. The time required to heat the metal for pouring is closest to which one of the following? (a) 6 min, (b) 8 min, (c) 10 min, (d) 25 min, (e) 50 min MC12.1 Besides helping to preserve the environment, the use of recycled glass as an ingredient of the starting material in glassmaking serves what other purpose(s)? (a) adds coloring variations to the glass for aesthetic value, (b) makes the glass easier to melt, (c) makes the glass stronger, (d) reduces odors in the plant MC12.2 The name of the process used to produce flat plate glass in which molten glass flows onto the surface of molten tin is which of the following? (a) casting, (b) Danner process, (c) float process, (d) molten-tin process, (e) rolling Review Questions: Chapter 6: 6.22, 6.25, 6.31, 6.38 Chapter 7: 7.3, 7.8, 7.16 Chapter 8: 8.15, 8.27 Chapter 9: 9.2, 9.10 Chapter 5: 5.1, 5.3, 5.4, 5.11 Chapter 10: 10.4, 10.17 Chapter 11: 11.2, 11.25 Chapter 12: 12.7, 12.12, 12.16 Problems: Chapter 6: 6.2, 6.4, 6.6, 6.7 Chapter 9: 9.3 Chapter 10: 10.3, 10.14 Chapter 11: 11.2, 11.9

6.22 What are the two main types of high-speed steel? The two main types of high-speed steel are tungsten and molybdenum 6.25 Identify some of the properties for which aluminum is noted? Some of aluminum’s properties noted are its high electrical & thermal conductivity, it is easily formable, light, abundant, and corrosion resistant. 6.31 What are some of the important applications of nickel? Nickel’s corrosion-resistant characteristics are why it is often used as an alloying element in steel, such as stainless steel, and as a plating metal on other metals such as plain carbon steel. Its alloys are commercially important because of their corrosion resistance and performance in high temperatures. 6.38 What is so special about the superalloys? What distinguishes them from other alloys? Superalloys are a type of high-performance alloys that are designed for high strength requirements and resistance to surface degradation, including corrosion and oxidation) at high temperatures. 7.3 What is the feature that distinguishes glass from the traditional and new ceramics? The feature that distinguishes glass from the traditional and new ceramics is that glass does not have a crystalline structure. 7.8 Thermal cracking is more likely in ceramics with high or low thermal expansion coefficients? Thermal cracking is more likely in ceramics with high thermal expansion coefficients. 7.16 What are some of the functions of the ingredients that are added to glass in addition to silica? Name at least three.

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The other ingredients reduce the thermal expansion in the final product, improve the chemical resistance against attacks from acids, bases, or water, add color to the glass itself, and alter the index of refraction for optical applications, such as lenses. 8.15 What are some of the factors that influence a polymer’s tendency to crystallize? Some of the factors that influence a polymer’s tendency to crystallize are the geometry of the structure the stereo regularity of the molecule-cooling rate, and the mechanical deformation. 8.27 What happens to an elastomer when it is below its glass-transition temperature? An elastomer below its glass-transition temperature becomes hard and brittle. 9.2 Identify some of the characteristic properties of composite materials. Composite materials have high strenght-to-weight ratios, good fatigue properties, and are corrosion resistant. 9.10 What is the rule of mixtures in the context of composite materials? The rule of mixtures states that certain properties of a composite material are calculable by taking a weighted average of the constituent materials’ properties. 5.1 What is a dimension? A dimension is a linear or angular size of a component that is explicitly on the part’s drawing. 5.3 What is accuracy in measurement? Accuracy is the degree to which a measured value agrees with the true value.

5.4 What is precision in measurement? Precision is the degree of repeatability in the measurement process 5.11 What are some of the advantages of electronic gages over mechanical measuring devices? Some of the advantages of electronic gages over mechanical measuring devices are its good speed of response, ability to determine very small dimensions, easy to operate, and reducing human error. 10.4 What are some of the disadvantages of casting? Some of the disadvantages of casting are the limitations on mechanical properties porosity, poor surface finish, and poor dimensional accuracy. 10.17 Why must the cross-sectional area at the bottom of the sprue be less than the cross- sectional area at the top of the sprue during pouring? The cross-sectional area at the bottom must be less when the metal is poured into the sprue opening. As the metal flows down, it accelerates resulting in a higher velocity. In order to maintain the same volumetric flow rate at the entrance and exit, the higher speed must be accounted for with a smaller cross sectional area further down the length of the sprue, thus resulting in a smaller cross-sectional area at the bottom. 11.2 Which of the two categories of casting processes have a natural advantage in terms of higher production rates, and why? Expendable mold and permanent mold casting have a natural advantage in terms of higher production rates because the molds can be made cheaply and relatively quickly, and the molds can be reused, respectively. 11.25 What are some of the general defects encountered in casting processes? Name and briefly describe three. Misruns are castings where the molten medal solidifies prior to filling the mold cavity entirely. Cold shuts is where two portions of the metal flow together, but they do not fuse, causing them to freeze too early. Cold shots is when splattering occurs during pouring, which leads to solid globules of metal trapped in the encasing.

12.7 Describe the spinning process in glassworking. The spinning process in glassworking is used to produce funnel-shaped components. A god of molten glass is dropped in the center of the cone shaped mold that is made of steel. Once it is spun around, the centrifugal force forces the glass to flow upwards along the mold. 12.12 What is the purpose of annealing in glassworking? Annealing in glassworking relieves unwanted internal stresses after forming, which can help increase the strength of the glass. 12.16 What are some of the design recommendations for glass parts? Glass is much stronger in tension rather than in compression. It is very brittle, so it would not be used in applications with impact loading or high stress environments. Outside edges and corners on glass parts should have large radii or chamfers, so inside corners should also have large radii because corners on the outside and inside are potential places for stresses to occur.

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