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日期：2022-08-01 10:22

Woodruff School of Mechanical Engineering

Liang CV.doc

Georgia Institute of Technology

ME 3210 Design, Materials, and Manufacture

1st Examination

(Shown here as an example test. Our test will be similar in format but different in scope)

If anything is unclear, make an assumption and proceed with it. However, only

reasonable assumptions receive credits.

1. [5 pts] Epoxy has 1.25 g/cm3 density and 4 GPa elastic modulus, while Kevlar–49 fiber has 1.5

g/cm3 density and 120 GPa elastic modulus. To make a Kevlar-49-reinforced epoxy composite with

6.5 GPa elastic modulus in transverse stretching, what should be its fiber volume fraction?

2. [5 pts] At 1,320oC, 10 g of solid and 5 g of liquid coexist in a pot of Cu-Ni alloy containing 60% Cu

by weight. If the Ni in the liquid weighs 3 g, how much is the weight (in g) of Cu in the solid?

3. [6 pts] In casting what is the maximum permissible H2 partial pressure (in atm) in liquid Ni if

the final part volumetric porosity should be less than 3.1% as liquid Ni saturated with H2

solidifies? Given that the specific weight of solid Ni is 1.6 g/cm3, and at 1 atm partial pressure

the solubility of H2 in Ni is 39 cm3H2 per 100 g liquid Ni and 18 cm3H2 per 100 g solid Ni.

4. [5 points] In a built-to-order case, a manufacturer has a 98% Process Capability (Cp)

associated with a maximum acceptable product length of 252.25mm and a minimum of

251.36mm. If another order requires a maximum acceptable product length of 252.45mm and a

minimum of 251.25mm, what would be the Cp of this manufacturer if nothing else is changed?

5. [2 points] What ONE is the primary reason for hot tearing in castings? (a) Melt pouring is

too fast; (b) Upon contraction during solidification, high tensile stress is developed; (c) Of melt

flow, fluidity is too low; (d) In filling mold cavity, air entrainment is too much; (e) Of castings,

solid thermal contraction is too large; (f) On sand-mold pattern, draft angle is insufficient.

6. [2 points] Which ONE of the following regarding SPC is incorrect? (a) If the measuring

resolution is 5% of the specified part tolerance, the measurement is capable; (b) If the average

of standard deviations of manufactured parts is 18% of the specified tolerance, the process is

capable; (c) If a process has 65% process capability index Cpk, it may be accurate; (d) If a

process has a process capability index Cpk of 78% along with a process capability Cp of 80%, it

is accurate; (e) There is no way a process is in control but is not capable; (f) A process with a

process capability Cp of 120% may be inaccurate.

Woodruff School of Mechanical Engineering

Georgia Institute of Technology

ME 3210 Design, Materials, and Manufacture

Solution for 1st Examination

3. Given that the volume of 100g solid Ni = 100/1.6 = 62.5 cm3

Porosity in solid = 3.1% = x/(62.5+x), x= released H2 upon solidification = 2 cm3 in 100g

casting. In liquid, permissible solubility = 18 + 2 = 20 cm3H2 per 100g liquid

g

G 39 20k y max permissible pressure = 0.26 atm

p 1 y

4. pp p

C 252.45 251.25As C tolerance C 132%

98% 252.25 251.36

Woodruff School of Mechanical Engineering

Georgia Institute of Technology

ME 3210 Design, Materials, and Manufacture

2nd Examination

(Shown here as an example test. Our test will be similar in format but different in scope)

If anything is unclear, make an assumption and proceed with it. However, only

reasonable assumptions receive credits.

1. [5 pts] With the use of powder metallurgy to make a solid copper cubical compact of 10mm

by 20mm by 30mm, how much (in volume, x103mm3) of loose, coarse copper powder is

needed? It is known that the full density of copper is 8.82x10-3 g/mm3 and the apparent density

of coarse copper powder is 3.49x10-3 g/mm3.

2. [5 pts] A 3”-diameter steel bar (of 1.2 hp-min/in3 specific cutting energy) is turned at 1,200

rpm spindle speed and 0.005” feed on a 13.5-hp lathe. What is the maximum depth of cut (in

inch) permissible at that cutting speed without stalling the motor?

3. [5 pts] It is observed that extruding a 3” diameter round bar to result in a round bar part of

1.5” diameter or smaller could cause cracking failure. To have a 1” diameter bar from extrusion

without cracking, what is the maximum allowable workpiece diameter (in inch) to begin with?

4. [6 pts] In using electron beam to drill a 2 mm diameter hole on silicon carbide part (with

80,000 J/mm3 specific burning energy) the volume removed per pulse should not exceed 1x10-5

mm3 to prevent workpiece overheating. If the equipment has a constant pulsing rate of 0.3x105

Hz, what is the maximum electron emission power (in Watt) that can be applied?

5. [2 points] The following 1~4 steps show the sequence to weld vertical bars, threaded rods, or

various fasteners on metal plates. Which one is the common terminology for this process: (a)

flash welding, (b) stud arc welding, (c) ferrule welding, (d) orthogonal arc welding, (e) press

welding, (f) impact welding.

6. [2 points] The following parts are designed to have internal openings as shown. Which

process is the one most suitable to create these internal features, after center holes are already

pre-made? (a) turning, (b) reaming, (c) tapping, (d) broaching, (e) drilling, (f) milling.