Manufacturing Processes - MFRG 317 - Course Work Assignments

The course work for this module which carries 30% of the module mark consists of two parts, which each carry equal marks. Students should write individual reports on each assignment. Reports should contain in the region of 1000 to 1800 words, plus diagrams, calculations and graphs.

Assignment 1 - Strain Hardening of Aluminium
This will be done in the Structures Laboratory - Room 1, Smeaton Building at the University of Plymouth.

Equipment You will be given a short cylinder of aluminium which you will compress axially using the Instron machine (which has a capacity of 100,000N).

Method Using a vernier, measure the height and diameter of the cylinder. Set the machine cross head to a nominal speed of 1 mm/minute (it appears in practice to be rather slower than the nominal setting). Set the load range to the maximum (100kN).

Carry out a hardness test on one end of the cylinder and from this determine the UTS of the aluminium.

1) Apply some grease to the ends of the cylinder and place the upright cylinder between the platens and move the cross head till it is almost in contact with the top of the cylinder. Start the cross head moving and as soon as the indicator on the chart starts to move start the stopwatch After one minute stop the watch and the machine. Remove the cylinder and measure its height and diameter.

2.) Repeat procedure 1. Check the cylinder diameter for uniformity, if the middle starts barrelling, note the maximum diameter as well as the diameter of the ends. Continue with the procedure 1 until the capacity of the machine is reached.

Results to be Calculated
You are to calculate the natural stain and true stress at each load increment. Plot a curve so that you are able to determine the values of K and n in the equation:

Take ln of the true stress and ln of the true strain and plot a graph with the ln(true stress) on the vertical axis and ln(true strain) on the horizontal axis. If you use Excel then you can fit a trend line to the graph. From the graph determine K and n.

Comment on the coefficient of friction between the platens and the cylinder - by using the barrelling measurements.

Comment on the accuracy of the experiment and how the flow stress relates to the yield strength of the aluminium.

What do the results tell you about the formability of this particular aluminium?

Assignment 2
Surface Roughness Produced During Milling
Method
Load a rectangular bar of medium carbon steel into the Bridgeport milling machine along with the Coromill 245, five tooth, insert tip cutter. Machine the four faces of the block with the feed rates indicated in the table below, using a spindle speed of 2500 rpm.

Results

Using the tactile roughness standards,compare the machined specimens and estimate their roughness values.

Use the Talysurf instrument to accurately measure the roughnesses of the four surfaces.

Examine the recorded chart profiles and using the stated vertical magnification of the charts, estimate the Ra values.

Compare the results and discuss possible reasons why they differ.

Confirmed Due Dates:
Assignment 1 is due in by 11.00am on Wednesday 17th December 2008.
Assignment 2 is due in by 11.00am on Thursday 26th March 2009.

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