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engineering
mechanical engineering
Questions and Answers of
Mechanical Engineering
Describe your thoughts on the processes that can be used to make (a) Small ceramic statues, (b) White-ware for bathrooms, (c) Common brick, and (d) Floor tile.
As described in this chapter, one method of producing superconducting wire or strip is by compacting powders of these materials, placing them into a tube, and drawing them through dies, or rolling
Review Fig. 11.18 and prepare a similar figure for constant-thickness parts, as opposed to the axisymmetric parts shown in the figure?
Explain the advantages of blending different metal powders in making P/M products?
Should green compacts be brought up to the sintering temperature slowly or rapidly? Explain.
What are the effects of using fine vs. coarse powders in making P/M parts? Explain.
Are the requirements for punch and die materials in powder metallurgy different than those for forging and extrusion, described in Chapter 6? Explain.
Describe the relative advantages and limitations of cold and hot isostatic pressing, respectively?
Why do mechanical and physical properties depend on the density of P/M parts? Explain.
Comment on the type of press required to compact powders using the set of punches shown in Fig. 11.7d?
Explain the difference between impregnation and infiltration. Give some applications for each?
What are the advantages of making tool steels by P/M techniques over traditional methods, such as casting and subsequent metalworking techniques? Explain.
Why do compacting pressure and sintering temperature depend on the type of powder metal used? Explain.
Name various methods of powder production and describe the morphology of powders produced by each method?
Green strength can be important in powder-metal processing? Explain why.
It was indicated that there are hazards involved in P/M processing. Describe their causes?
What is screening of metal powders? Why is it done?
Why are there density variations in compacted metal powders? How can they be reduced?
It has been stated that P/M can be competitive with other processes, such as casting and forging. Explain why this is so, commenting on technical and economic advantages?
Selective laser sintering was described in Section 10.12.4 as a rapid-prototyping technique. What similarities does this process have with the processes described in this chapter? Explain.
Prepare an illustration similar to Fig. 6.28, showing the variety of P/M manufacturing options?
Describe the major differences between ceramics, metals, thermoplastics, and thermosets?
Explain why ceramics are weaker in tension than in compression?
Why do the mechanical and physical properties of ceramics decrease with increasing porosity? Explain.
What engineering applications could benefit from the fact that, unlike metals, ceramics generally maintain their modulus of elasticity at elevated temperatures?
Give the reasons that injection molding of metal powders has become an important process?
Explain why the mechanical-property data given in Table 11.7 have such a broad range. What is the significance of this wide range in engineering applications? Explain.
List and explain the factors that you would consider when replacing a metal component with a ceramic component. Give examples of such possible substitutions, also commenting on their shape and size?
How are ceramics made tougher? Explain.
Describe situations and applications in which static fatigue can be important?
Explain the difficulties involved in making large ceramic components. What recommendations would you make to overcome these difficulties?
Explain why ceramics are effective cutting-tool materials, as described in Section 8.6. Would ceramics also be suitable as die materials for metal forming? Explain.
Describe applications in which the use of a ceramic material with a zero coefficient of thermal expansion would be desirable?
Give reasons for the development of ceramic-matrix components. Name some present and future possible applications?
List the factors that are important in drying ceramic components and explain why they are important?
It has been stated that the higher the coefficient of thermal expansion of glass and the lower its thermal conductivity, the higher is the level of residual stresses developed during processing?
Describe the events that occur during sintering?
What types of finishing operations are typically performed on ceramics? Why are they done?
What should be the property requirements for the metal balls used in a ball mill (see Fig. 11.26b)? Explain why these particular properties are important?
Explain the reasons that so many different welding processes have been developed?
Explain why the electroslag welding process is particularly suitable for thick plates and heavy structural sections?
Design a machine that can perform friction welding of two cylindrical pieces and be able to remove the flash from the welded joint. (See Fig. 12.30.)?
How would you modify your design in Problem 12.101 if one of the pieces to be welded has a noncircular cross section?
Describe part shapes that cannot be joined by any of the friction welding processes?
Make a comprehensive outline of joint designs relating to the processes described in this chapter. Give specific examples of engineering applications for each type of joint?
Review the two weld designs shown in Fig. 12.58a and based on the topics covered in courses on the strength of materials, show that the design on the right is capable of supporting a larger moment?
In the building of large ships, it is necessary to weld large sections of steel plates together to form a hull. For this application, consider each of the welding operations described in this chapter
Examine various household products and describe how they are joined and assembled. Explain why those particular processes are used for these particular applications?
A major cause of erratic behavior (hardware bugs) and failures of computer equipment is fatigue failure of the soldered joints, especially in surface-mount devices and those with bond wires. (See
What are the similarities and differences between consumable and non-consumable electrode arc welding processes? Explain.
Make an outline of the general guidelines for safety in welding operations. For each of the operations described in this chapter, prepare a poster which concisely and effectively gives specific
A common practice for repairing expensive broken or worn parts, such as may occur when, for example, a fragment is broken from a forging, is to fill the area with layers of weld bead and then to
In the roll bonding process shown in Fig. 12.28, how would you go about ensuring that the interfaces are clean and free of contaminants, so that a good bond is developed? Explain.
Alclad stock is made from 5182 aluminum alloy, both sides of which are coated with a thin layer of pure aluminum. The 5182 provides high strength, while the two outside layers of pure aluminum
Using the Internet, investigate the geometry of the heads of screws that are permanent fasteners, that is, ones that can be screwed in but not out?
Obtain an expression similar to Eq. (12.6) but for electron-beam and laser-beam welding?
In Table 12.2, there is a column on the distortion of welded components, ranging from lowest to highest. Explain why the degree of distortion varies among different welding processes?
Explain why the grains shown in Fig. 12.16 grow in the particular directions shown?
Prepare a table listing the processes described in this chapter and provide, for each process, the range of welding speeds as a function of work piece material and its thickness?
Explain what is meant by solid-state welding?
Describe your observations concerning Figs. 12.19, 12.20, and 12.21?
What advantages does friction welding have over the other joining methods described in this chapter? Explain.
Why is diffusion bonding, when combined with super plastic forming of sheet metals, an attractive fabrication process? Does it have any limitations? Explain.
Can roll bonding be applied to various part configurations? Explain.
List the advantages and limitations of mechanical fastening as compared with adhesive bonding.
Comment on your observations concerning Fig. 12.41?
If electrical components are to be mounted to both sides of a circuit board, what soldering process(es) would you use? Explain.
Discuss the factors that influence the strength of (a) a diffusion bonded component and (b) a cold welded component?
Describe the difficulties you might encounter in applying explosion welding in a factory environment in urban areas?
Inspect the periphery of a U.S. quarter and comment on your observations. Is the cross section, i.e., the thickness of individual layers, symmetrical? Explain.
What advantages do resistance welding processes have over others described in this chapter? Explain.
What does the strength of a weld nugget in resistance spot welding depend on? Why?
Explain the significance of the magnitude of the pressure applied through the electrodes during resistance welding operations?
Which materials can be friction stir welded, and which cannot? Explain.
List the joining methods that would be suitable for a joint that will encounter high stresses and will have to be disassembled several times during the product life, and rank the methods?
Describe the similarities and differences between consumable and non-consumable electrodes?
Inspect Fig. 12.31 and explain why those particular fusion-zone shapes are developed as a function of pressure and speed. Comment on the influence of the properties of the material?
Give several examples concerning the bulleted items listed at the beginning of Section 12.1?
Could the projection welded parts shown in Fig. 12.36 also be made by any of the processes described in other parts of this text? Explain.
Describe the factors that influence the flattening of the interface after resistance projection welding takes place?
What factors influence the shape of the upset joint in flash welding, as shown in Fig. 12.37b? Why?
Explain how you would fabricate the structures shown in Fig. 12.41b with methods other than diffusion bonding and super plastic forming?
Make a survey of metal containers for household products and foods and beverages. Identify those that have utilized any of the processes described in this chapter. Describe your observations?
Which process uses a solder paste? What are the advantages to this process?
Explain why some joints may have to be preheated prior to welding?
What determines whether a certain welding process can be used for work pieces in a horizontal, a vertical, or an upside-down position, or for all types of positions? Explain, giving appropriate
What are the similarities and differences between fusion welding and casting of metals, described in Chapter 5?
Explain the role of the excessive restraint (stiffness) of various components to be welded on possible weld defects?
Discuss the weldability of several metals and explain why some metals are easier to weld than others?
Does the filler metal have to be of the same composition as that of the base metal to be welded? Explain.
Describe the factors that contribute to the difference in properties across a welded joint?
How does the weldability of steel vary as its carbon content increases? Why?
Are there common factors among the weldability, solderability, castability, formability, and machin-ability of metals? Explain giving appropriate examples?
Describe the procedure you would follow in inspecting a weld for a critical application. If you find a flaw during your inspection, how would you go about determining whether or not this flaw is
Do you think it is acceptable to differentiate brazing and soldering arbitrarily by temperature of application? Explain.
Loctite® is an adhesive used to keep metal bolts from vibrating loose; it basically glues the bolt to the nut after the nut is inserted in the bolt. Explain how this adhesive works?
Comment on your observations regarding Fig. 12.5?
List the joining methods that would be suitable for a joint that will encounter high stresses and cyclic (fatigue) loading, and rank the methods in order of preference?
Why is surface preparation important in adhesive bonding? Explain.
Why have mechanical joining and fastening methods been developed? Give several specific examples of their applications?
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