20015S 262 Hw 3 Solution

April 7, 2015
Bilkent University
Department of Industrial Engineering
IE 262
Homework 3
Due Date: April 17, 2015 (Friday)

1. A hydraulic forging press is capable of exerting a maximum force of 1,000,000 N. A cylindrical work part is to be cold upset forged. The starting part has a diameter of 30 mm and a height of 30 mm. The flow curve of the metal is defined by K=400 MPa and n=0.2.
Suppose that the coefficient of friction between the work part and the die is 0.1.
a. In Excel, plot a graph of forging force vs. work height for the values of work height from 20 mm to 15 mm.
b. Determine the maximum reduction in height to which the part can be compressed with this particular forging press. Again, use of a spreadsheet calculator is recommended. Solution: We first provide the solution of part b below.

In the solution above, you have calculated the value of forging force for hf = 20mm. You just need to repeat it for, say hf=19,18,17,16,15 and plot the values of forging force vs hf in a scatter plot in Excel. The plot should be an increasing function (remember, both the strength of the metal and the contact area increases as hf decreases from 20 to 15.

2. Watch http://www.youtube.com/watch?v=V7Y0zAzoggY to see how an aluminum beverage can is made. Identify each step in the whole manufacturing process, and present them in a flow chart using your own words. We learned many different types of

manufacturing processes in this course so far. Explicitly specify which one(s) of them are being shown in this video.
Blanking in punch press
Deep drawing

3. A series of cold rolling operations are to be used to reduce the thickness of a plate from 50 mm down to 25 mm in a reversing two-high mill. Roll diameter = 700 mm and coefficient of friction between rolls and work = 0.15. The specification is that the draft is to be equal on each pass. Determine (a) minimum number of passes required, and (b) draft for each pass? 4. An orthogonal cutting operation is performed using a rake angle of 15°, chip thickness before the cut = 0.012 mm and width of cut = 0.100 mm. The chip thickness ratio is measured after the cut to be 0.55. Determine
a.
b.
c.
d.
e.

the chip thickness after the cut, shear angle, friction angle, coefficient of friction, and shear strain.

5. The orthogonal cutting operation described in Problem1 involves a work material whose shear strength is 95 MPa. Based on your answers to the previous problem, compute
a. the shear force,
b. cutting force,
c. thrust force, and
d. friction force.

6. Tool life tests in turning yield the following data: (1) when cutting speed is 120 m/min, tool life is 7 min; (2) when cutting speed is 80 m/min, tool life is 28 min.
a. Determine the n and C values in the Taylor tool life equation.
b. Based on your equation, compute (i) the tool life for a speed of 110 m/min, and (ii) the speed corresponding to a tool life of 15 min.