| Manufacturing Processes - Tutorial Questions |
These questions are primarily for students studying MFRG 318
1. Question on powder metallurgy
2. Briefly summarise the methods of manufacturing powder that can used in powder metallurgy products.
Briefly describe the key features, advantages and disadvantages of these methods.
3. Explain the stages in the manufacture of a product (such as a simple bush) by a powder metallurgy route.
4. What is meant by 'machinability' and what factors affect the machinability of a workpiece?
5. A HSS tool when cutting a plain carbon steel at a speed of 45.766 m/min has a life of 15 minutes. If C = 60
for this combination of tool material and workpiece, determine 'n' and the tool life at a cutting speed of 35 m/min.
6. Show with the aid of a sketch the location of the two zones where heat is generated in a single point
orthogonal cutting process. State the common assumption about where the heat goes to and the effect of speed on this.
7. A carbide cutting tool has a life of 1 minute when cutting at a speed of 1000 m/minute. If the tool life
is 10 minutes at a cutting speed of 500 m/minute, what is the Taylor tool life exponent 'n'.
8. What are the advantages and disadvantages of the following materials when used as cutting tools:
9. Describe with the aid of sketches how the process of chip formation changes with cutting speed
when machining steel.
10. Sketch Mohrs Circle to represent the state of stress in the following:
11. What are the approximate temperature ranges where hot and cold working are
carried out? What are the relative merits of these 2 types of processing?
12. Why do the yield strength and UTS of metals increase with increasing amounts
of cold work? How can the effects of cold work be removed?
13. What is meant by the term 'friction hill' and what causes it? - Choose an
example carry out a simple analysis to determine the form of the 'friction hill'.
14. What is meant by redundant work? - show with the aid of an example the effect
it has in metal forming operations.
15. What defects may occur in an extrusion process?
16. Explain, with the aid of Mohrs Circle diagrams why applying back tension
can be beneficial in rolling and wire drawing.
17. Show that during a cold tension test the maximum load occurs at the point
when n (the strain hardening exponent) is approximately equal the true strain, epsilon.
18. A pure copper plate 500 mm wide and 60 mm thick is being hot rolled at 900oC down to 50 mm
thickness in a single pass at a speed of 0.5 m/s. The rolls have a diameter of 800 mm and the coefficient of
friction (mu) = 0.2. Sketch the process, determine the average roll pressure, the roll separation force and
the power required.
19. A company proposes to manufacture barbecue spits by locally flattening 5 mm
diameter mild steel wire. The process is to be done cold with a lubricant which gives a
friction coefficient between the die and the workpiece of 0.1. The flattened portions
are 50 mm long and 2 mm thick. For steel: K = 620 MPa and n = 0.18.
a) Sketch the feature after manufacture
b) Identify the strain category, with justification.
c) Estimate the force required (use chart supplied).
(plane strain, 448 kN).
20. A cylindrical copper billet 50 mm in diameter and 100 mm high is to be upset at
900oC to a 15 mm thick disc. The speed of the press is 2.4 m/minute and
a lubricant reduces the coefficient of friction between the tools and workpiece to 0.2.
Sketch the process, calculate the average die pressure and the force needed to achieve
this operation (C = 41 MPa, m = 0.2).
21. A Ti6Al4V titanium billet, 1.5 m long x 100 mm diameter is being forged at
900oC and reduced to a rectangular slab with a thickness of 30 mm.
22. A steel strip 2 mm thick is cold rolled through a 4 stand tandem mill. A
reduction of 40% is taken at each pass. The strip speed into the first pass
is 3 m /s. Calculate the strip thickness and strip speed after each stand.
23. A stainless steel billet 80 mm diameter and 160 mm high is upset at
1000oC to a 20 mm high 'pancake'. The press speed is 3 m/minute
and a graphite lubricant reduces the friction coefficient to 0.2. Sketch
the process and calculate the average die pressure and total force. For the
material, C = 170 MPa and m = 0.1 (see chart from appropriate text).
24. Determine the maximum theoretical reduction possible in wire drawing,
without back tension, neglecting friction and assuming no work hardening.
25. The initial stage in the manufacture of a knife blade made from grade 410
stainless steel involves forging a 90 mm length of 8mm dia. bar at 1000oC
in a press with a speed of 0.005 m/s. You may assume that the frictional shear factor
is 0.2.
26. Describe with the aid of a sketch what is meant by a forming limit diagram and explain how such
a diagram is obtained.
27. Describe the defects that can occur during sheet metal processes and how
they may be overcome.
28. What is meant by anisotropy in sheet metal, what causes it and how and in
what process might its presence be observed?
29. Why is the clearance between the punch and die important in sheet metal
blanking / punching operations. Briefly describe some of the disadvantages and
problems that may occur if working with non-optimum clearance. Use simple
sketches if appropriate.
30. What shearing force is required to shear a 1m width by 3mm thick sheet
of SAE 1015 steel and what is the total energy required?
31. Circular blanks, do = 200 mm, are to be cut from 3 mm thick
AISI 1008 steel sheet. What press force is needed and what energy is needed to
cut each blank?
32. Deep drawing quality 2mm thick steel sheet with a LDR of 2.4 is to be drawn into
100 mm diameter cups with a 5 mm radius at the base.
33. A low carbon steel, AISI 1008, steel container with an internal diameter of 56 mm and
an internal depth of 80 mm and an internal bottom corner radius of 8 mm, is to be made by
deep drawing 1.5 mm thick sheet. Assuming that the average thickness of the container equals
the average blank thickness, calculate:
34. What force is required to put a 90o bend in a 600mm width of
4 mm thick cartridge brass when the width of the die opening is 40mm?
35. What are the key features of:
David J Grieve, 17th March 2009.
If this tool was cutting a chip 3 mm wide with an undeformed chip thickness of 1.5 mm, what machine power is required
assuming the specific cutting energy, E1 = 1.5 W.s/mm3 and the machine tool has an efficiency of 70%
(n = 0.1, 219 minutes, click here for solution and 5 kW).
(n = 0.301).
High speed steel (HSS), carbides, ceramics and cubic boron nitride?
(56.5 N/mm2, 1.78 MN, 141 kW, click here for solution
What would you expect to happen if no lubricant was used?
(89.8 MPa, 1.18 MN).
Sketch the process.
Can this process be described as plane strain and if so why, or if not, why not?
Determine the press force required, assume the press has a constant speed of
0.05 m/s and the coefficient of friction is 0.2
Briefly state why it is important to complete the operation in the minimum time.
Solution
1.2, 0.72, 0.432, 0.26; 5, 8.33, 13.9, 23.15 m/s.
Solution
17.2 MN
Solution
(do / d1) = 1.65
Solution
Sketch the process, determine the maximum mean platen pressure and the
force required to carry out the operation.
Soln: Pp = 214.3 MPa, force = 323000N. click here
(Assuming the tensile strength is 450 MPa: 1146 kN and 1719 Nm)
(Assuming tensile strength = 320 MPa [k=600, n=0.25] Ps = 513 kN, Es = 769 Nm)
(Click here for: solution).
a) Sketch the process.
b) Estimate the maximum possible blank diameter that can be drawn.
c) Estimate the maximum depth of cup that can be drawn, stating your assumptions.
(Click here for solution).
a) The starting blank diameter.
b) The draw sequence, assuming the first draw is made with a blank holder.
c) Estimate the press force for the first draw.
(Click here for solution: page 1,
page 2, page 3).
(Assuming the tensile strength is 310 MPa: 74.4 kN)
