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

1. In transverse stretching f f f f f
c m f
(1 V ) V (1 V ) V1 1 V 40%
E E E 6.5 4 120
       

2. L O S
L S S
C CS 10 (1 3 / 5) 0.6 C 0.7
S L C C 10+5 (1 3 / 5) C
          .  Cu in solid=10(0.7)=7g

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
    

5. (b)

6. (b)




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.







Woodruff School of Mechanical Engineering
Georgia Institute of Technology
ME 3210 Design, Materials, and Manufacture
Solution for 2nd Examination

1. The initial powder volume should be 3 3s s
a
V 8.82(10 20 30)V 15.16 10 mm
3.49
     

2. P Ddf 13.5 (1.2) (3)d(0.005)(1200) d 0.2"      

3.
2 2
max 2 2
3 xln =ln x=2"
1.5 1
  

4.    5 5e a b pI V K volume removed per pulse f 80,000(1 10 ) 0.3 10 24,000W    

5. (b)

6. (d).




Woodruff School of Mechanical Engineering
Georgia Institute of Technology
ME 3210 Design, Materials, and Manufacture
Final 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. [4 pts] A company is considering 2 machine purchase options. Option #1 is a $550,000
machine that makes 50 parts/day, with a 60% load factor. Option #2 is a $770,000 machine
that can deliver a higher production rate, thus leading to a 70% load factor by attracting more
customers. All machines have 3 years write-off and $127/hour energy charge. What has to be
the minimum production rate (in parts/day) of Option #2 for this option to make sense in view of
unit product cost? Consider 24 working hours per day and 365 working days per year.

2. [4 pts] A metal has 58 g/cm3 full density. A square cubical green compact of this metal has a
volumetric porosity of 30% and a side dimension of 20 cm. After the green compact is sintered
to a product of 56 g/cm3 density, what is the product’s side dimension (in cm)?

3. [4 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 13.3% 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. [4 pts] A steel bar is turned with a tungsten carbide cutter costing $80 per piece, which
cannot be re-sharpened. It typically takes 10 minutes to replace a tool. The operation cost is
$240 per hour, excluding tool purchase cost. Estimate the lowest possible total specific cost
(that is the total cost per unit material removed, in $/in3) at 0.01” radial depth of cut and 0.01”
feed. Note that Taylor’s tool life model with n = 0.125 and k = 300 fpm works well in this case.

5. [4 pts] A 0.75”-diameter drill is operating at a rotational speed of 1,400 rpm and a feed of
0.005 inch/rev. If the drill diameter is doubled while the rotational speed is reduced to 350 rpm,
what should be the feed (in inch/rev) so that the same material removal rate can be maintained?

6. [4 pts] An electron beam machine, with a constant emission current of 100 mA and constant
emission voltage of 120 KV, is used to drill a 1.25 mm diameter and 6 mm depth through hole
on silicon carbide part (with 80,000 J/mm3 specific burning energy). While the volume removed
per pulse is desired to be 1x10-5 mm3 in the interest of productivity and workpiece quality,
determine the required beam pulsing rate (in Hz).

7. [2 pts] On statistical process control, which of the following is correct? (a) If Cp is 135% and
Cpk 90%, the process is capable and is in control; (b) If Cp is 180% and Cpk 105%, the process
is precise and accurate; (c) If Cp is 120% and Cpk 90%, the process is not precise and not
accurate; (d) If Cp is 110% and Cpk 108%, the process is precise but is not accurate; (e) If Cp is
90% and Cpk 90%, the process is not precise but is accurate; (f) If Cp is 87% and Cpk is 60%,
the process is repeatable but is not correct.

8. [2 pts] Shown below is a sheet flexing in opposite directions as it passes through a series of
rollers, each driven separately with motors. What is most likely the purpose of this operation for
the sheet? (a) elongating, (b) strengthening by successive deformation, (c) corrugating, (d)
strengthening by imparting compressive residual stress, (e) flattening, (f) surface finishing.





Woodruff School of Mechanical Engineering
Georgia Institute of Technology
ME 3210 Design, Materials, and Manufacture
Solution for Final Examination

1.
c c
oh oh
wo wo
C C '1 1C C'
n L t n ' L ' t '
1 550,000 1 770,000127 24 127 24 n' 52
50 60% 3 365 n' 70% 3 365
            
                   
 
 



2.
  3green 58 1 30% 40.6 g/cm     ;
3 3
green 3sintered sintered
sin tered
green sintered
40.6 18 g/cm
20 56
                
  

3. Given that the volume of 100g solid Ni = 100/1.6 = 62.5 cm3
Porosity in solid = 13.3% = x/(62.5+x), x= released H2 upon solidification = 9.6 cm3 in 100g
casting. In liquid, permissible solubility = 18 + 9.6 = 27.6 cm3H2 per 100g liquid
g
G 39 27.6k y max permissible pressure = 0.5 atm
p 1 y
    

4. For least total specific cost, the optimal cutting speed is
 
 
0.125n
c
c
240 0.125
R n 60v k (300) 152 fpm
c 240R t (1 n) 80 10 1 0.125
N 60
                                   

total specific cost is then
   1/0.125 1/0.1251/n 1/nc
3
t 1/n 1 (1/n) 1/0.125 1 (1/0.125)
o
240c 300 152 10 80R k v t
60Nc $297.4 / in
k v t b 300 152 0.01 0.01

 
   
    

5. The MRR for drilling is  2MRR D fN / 4  , so the doubling of D will completely counter the 4-
fold reduction of N, thus the feed should be still be 0.005 inch/rev to keep the same MRR.

6.   5e a b p f fI V K volume removed per pulse f 100(120) 80,000(1 10 )f f 15,000 Hz     

7. (e)

8. (e)