2007 ENMF417 Final exam final

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ID ________________________________ ENMF417 2007 Pg. 1/11 The University of Calgary Faculty of Engineering Final Examination ENMF 417: Manufacturing Process and Engineering Instructor: Dr. Simon Park Date: December 14, 2007 Duration: 3 hours Location: KN Auxiliary Gym Instructions: • This exam is 50% of the total grade. • The exam is “closed book” and “closed notes”. • Turn off all your electronic devices including MP3 players, cell phones, etc. • The use of a non-programmable calculator is permitted. • Write the answers in the separate examination booklets (including the multiple choice questions) • Write neatly as possible and underline the answers. • A – Multiple Choice questions (1 point x 30 questions = 30 points) • B – Short Answer questions (35 points) (point forms are acceptable) • C – Calculation questions (35 points) Name ________________________________

ID ________________________________ ENMF417 2007 Pg. 2/11 Score for Part I__________________/30 Score for Part II__________________/35 Score for Part III__________________/35 Total ________________ PART I. Multiple Choice Questions (Choose the most appropriate answer) 1 How do you distinguish tubings from pipes? a. Tubings are measured by the thickness b. Tubings are measured by the width c. Tubings are measured from the internal diameters d. Tubings are measured from the external diameters 2 Which of the following forging operation types will generally produce the best accuracy? a. open die forging b. impression die forging c. closed die forging d. roll forging 3 The geometry of an extrusion die can influence the effectiveness of extrusion in a number of ways. Which of the following is not a consequence of the geometry of the die? a. extrusion pressure b. die life c. residual stress d. none of the above 4 Redundant work in any bulk deformation process is a function of which of the following factors? a. tool or die geometry b. friction c. resistance to deformation d. ductility 5 Which of the following factors is not a consideration when determining fluidity of a material for casting purposes? a. thermal conductivity b. specific heat c. viscosity d. density 6 Which of the following process is most susceptible to porosity? a. die casting b. sand casting c. investment casting d. shell casting

ID ________________________________ ENMF417 2007 Pg. 3/11 7 Which of the following factors is not a justification for using a surface grinder to finish a particular surface? a. specific energy for grinding is better than for milling or turning b. the workpiece material is very hard c. an accurate tolerance can be easily achieved d. a very low roughness surface finish can be produced 8 Which of the following is not a justification for using a pilot hole before drilling a given size of hole? a. a straighter hole is possible b. ‘grabbing’ by the twist drill can be prevented c. the forces required to move the drill are reduced d. location of the hole can be more accurate e. none of the above 9 What is the maximum reduction of thickness in rolling when the Radius is 1 m, the friction coefficient is 0.1? a. 0.1 b. 0.01 c. 0.001 d. 0 10 Chevron cracking is an example of what kind of defects? a. oxidation defects b. temperature gradient thermal shock defects c. excessive surface residual stress defects d. hydrostatic tensile stress defects 11 Which of the followings is not a factor affecting sheet metal deformation? a. elongation b. grain size c. isotropy d. residual stress 12 Which of the following describes a cutting operation where shearing a closed outline of desired sheet metal parts? a. punching b. blanking c. shearing d. none of the above 13 Which of the following is not a method in refining the grain size in a cast component? a. Inoculate the melt with nuclei to promote heterogeneous nucleation b. Use low mold temp c. Use mold with high heat conductivity d. None of the above 14 How would you compensate for spring back of sheet metal bending? a. over bending b. coining c. stretch bending d. all of the above

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ID ________________________________ ENMF417 2007 Pg. 4/11 15 Which of the following phrases is correct about the Weldability? a. Worker’s skills to be considered b. Lubrication is relevant to the weldability c. Physical properties of the base metal are not relevant to the weldability d. Metallurgical structure to be examined 16 Where is the Z axis in Lathes? a. Parallel to the cutting tool b. Parallel to the Spindle c. Perpendicular to the center axis of Chuck d. Perpendicular to Dead center 17 When you use a CNC machine, which information do you need to provide? a. Surface model of parts b. Solid model of parts c. The properties of materials d. G-Codes 18 MIG welding is similar to TIG welding in which of the following way? a. Inert gas shield b. Consumable electrode c. High productivity rates d. Low HAZ 19 Which of the following work is independent of the die angle during drawing practices? a. redundant work b. frictional work c. ideal work d. total work 20 Which is the greatest advantage of forging a vehicle engine's crankshaft? a. Improved tolerances and surface finish b. Higher strength c. Size and geometry d. None of the above 21 In a set of metal cutting experiments, the following is reported: if the cutting speed is doubled while keeping all other parameters, the tool life is decreased by ____________. a. Factor of 2 b. Factor of 3 c. Factor of 4 d. No change

ID ________________________________ ENMF417 2007 Pg. 5/11 22 For non-ferrous metals, which tool material will provide the most accurate finish? a. Cermets b. WC c. PCD d. CBN 23 In PM processes, density is important. Which statement is incorrect about density? a. Density is affected by pressure b. Density determines strength c. Density is uniform in the die due to friction d. For complex dies, additional compactions are needed to achieve uniform density 24 When the springback factor is 1, it represents … a. Total plasticity b. Total elastic recovery c. Both elastic and plastic deformation d. None of the above 25 Which of following processes has minimal Residual stress during fabrication? a. casting b. machining c. welding d. rolling 26 When temperature increases, which of the following happens? a. ductility decreases but toughness increases b. Young’s modulus increases and ductility increases c. Toughness increases and UTS decreases d. Strength and UTS increases 27 In order to avoid chatter in milling of the Aluminum workpiece, what should be the spindle speed when the resonance frequency of the machine is 300 Hz and the number of flutes is 4? a. 18000 rpm b. 4500 rpm c. 20 rpm d. None of the above 28 A rectangular cantilever beam of 100 mm in height, 10 mm in width and 1 m in length is subjected to a concentrated load of 50 kg at its end. How much (approximately) would the ABS beam deflect compared with the steel beam? a. 10 times b. 20 times c. 100 times d. 1000 times

ID ________________________________ ENMF417 2007 Pg. 6/11 29 Which of the following is not a reason for the large specific energies involved in grinding compared to machining? a. size effects b. small particle sizes c. large negative rake angle d. shearing, plowing, and rubbing 30 Guest lecture: Which of the following is not a process(es) involved in electronics manufacturing? a. PCB, SMT, and PTH b. Silk screening, drilling c. Wave soldering d. None of the above _______________________________________________________________________ PART II. Short Answer Problems (35 pts) Q1[4 pts] Explain the causes for the following defects ( a to d ) and provide remedies to prevent the defects. Q2 [9 pts] Describe and explain the following processes ( select three ). a. Explain why thermoplastics are easier to recycle than thermosets. b. Vulcanization and why would you perform vulcanization? c. Why would you perform diffusion welding over other fusion welding processes? Explain the process of diffusion welding. d. Describe the differences between Tresca vs. Von Mises Criteria. e. Describe cause and phenomena of chatter in milling operations. How would you prevent or minimize chatter? Q3 [3 pts] Why would you use bulk deformation processes over other manufacturing processes? Provide three reasons.

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ID ________________________________ ENMF417 2007 Pg. 7/11 Q4 [10 pts] Discuss the manufacturing processes most suitable for making the products listed below (be specific) . In addition, provide the reasons for your choice of process. (Include at least 2 factors such as cost, quantities, finish, strengths, defects, dimensional accuracies, etc. for each answer.) a. Aluminum Cans (Qty: 10 millions) b. Golf Iron Head (Qty: 5,000) c. Carbide Inserts for Turning Bars (Qty: 100,000) d. Aluminum foams (Qty: 10,000) e. 1000L Plastic Water Tank (Qty: 1,000)

ID ________________________________ ENMF417 2007 Pg. 8/11 Q5 [4 pts] In an attempt to improve the life of cutting tool for a particular turning operation, the front rake angle of the tool is changed from +35 o to +25 o . Describe the likely impact on the following performance variables: (increase, decrease, unchanged) a. cutting force b. specific energy c. deformed chip thickness d. power consumption Q6 [5 pts] Design for Manufacturing and Assembly. Select the better design and explain why. a. Assembly (i) (ii) b. Casting (i) (ii) c. Injection Molding (i) (ii) d. Injection Molding (i) (ii) e. Sheet Metal (i) (ii)

ID ________________________________ ENMF417 2007 Pg. 9/11 PART III. Calculation Problems (35 pts) State all your assumptions and put UNITS. Underline your answer. Q7 [10 pts] In an effort to reduce the weight of the sprocket/shaft assembly, it is proposed that an integrated design could be manufactured by cold forging (upsetting) an aluminum shaft (shown in the upper view) to form the finished shaft and sprocket blank (shown in the lower diagram) followed by machining of the sprocket teeth in the enlarged disc. The lower view shows a cross section of the forging (upsetting) dies and the upset shaft. The dimensions of the workpiece are as follows: Initial length: 180 mm Initial diameter: 20 mm The enlarged disc should have a final diameter of 40 mm and a thickness of 8 mm. The proposed workpiece is the Aluminum alloy with σ = Κ ε n ; K = 205 MPa and n = 0.2. The following question assumes that the process proposed is viable. a. How far do the dies need to move (in mm) during a complete loading stroke? b. What is the true strain imposed upon the workpiece? c. What is the flow stress at the end of the deformation? d. What force would be required to complete the deformation? sprocket Side view

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ID ________________________________ ENMF417 2007 Pg. 10/11 Q8 [10 pts] An orthogonal turning operation is being carried out under the following conditions: feed = 0.1 mm/rev, width of cut = 5 mm, deformed chip thickness = 0.1 mm, cutting speed = 60 m/min, rake angle = 20 o , tangential force = 300 N, and friction angle is = 40 o . Calculate the percentage of the total energy that is dissipated in the shear plane during cutting. Q9 [7 pts] In a stretch forming, a thin sheet metal, whose thickness is 3 mm, the width of 2 m and the length of 3 m, is stretched with a force F until the angle α is 30 0 as shown in the figure below. The material has a true stress-true strain where the metal has a strength coefficient of 965 MPa and a strain-hardening exponent of 0.14 (1045 hot rolled steel). Find the work done if frictional and redundant work contributes to 30%. 2 m F Q10 [8 pts] In plain milling (see the following figure) the tool diameter is D = 120 mm, and wheel rotation speed is N = 100 rpm. The width to be cut is w = 60 mm, the length of the workpiece to be cut is L = 500 mm. The thickness of the surface layer to be removed is d = 3 mm. The tool feeding speed of V = 0.6 m/min is relative to the workpiece, and the cutter has 10 inserts. The workpiece material is a high strength aluminum alloy with the unit power of cut as 1.1 W-s/mm 3 . Calculate (a) the material removal rate, (b) cutting time, (c) feed per tooth, and (d) estimate the power required (in kW) . ************** SSP/SSP α

ID ________________________________ ENMF417 2007 Pg. 11/11 s s s A F = τ c c h h r = a v u a F F µ β = = tan c s bh A φ sin = ) cos( cos r c r s V V α φ α − = c f c t r a c s F F F F φ φ α β φ sin cos ) cos( − = − + = ) cos( ) sin( ) cos( ) cos( r a c c r a s r a t bh F F α β φ φ α β τ α β − + − = − = ; r c r c c r r α α φ sin 1 cos tan 1 − = − ) cos( sin r c c c c h h L α φ φ − = = t f r a F F = − ) tan( α β ) ( r s s s s s T T C MRR V F P − ⋅ = = V r V c c = c u u V F P = u MRR P P V F P u s t tot ⋅ = + = = Theoretical shear angle (Min. Energy Principle) 2 ) ( 4 r a c α β π φ − − = nN f c = ) sin( φ c h = π 2 60 n = Ω t Ω = φ q t t C V C T − = -p Rt I H 2 = 2 / 1 − + = kd Y Y i l a d c L D p q η π 128 4 = Plane Strain (Von Mises): ' 15 . 1 3 2 3 1 Y y y = = = − σ σ σ σ ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ + ≈ h a Y p avg µ 1 ' ; ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ − = h x a Y P ) ( 2 exp ' µ ; Rolling: R h h f 2 0 µ = − Extrusion f A A R 0 = ; ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ = = f A A k u p 0 ln ; [ ] 1 tan 1 cot − ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ + = α µ µ α R Y p Drawing ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎣ ⎡ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ − ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ + = α µ µ α σ cot 0 1 tan 1 A A Y f d ; ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ = f f A A YA F 0 ln Sheet Metal: Lb = a (R + k*t) 1 3 4 ; 1 ) / 2 ( 1 ) / 2 ( ; 2 2 , 3 + ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ − ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ = + + = = ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ + = ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ + = Et Y R Et Y R R R t R t R Ks t R t R allowance Bend L i i f i f i i f f f i i b α α α α