1.1.1 General Questions

 

 

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1. A cylindrical impression with a diameter of 10mm and a depth of 1mm has to be made on a tungsten carbide surface. The feed force is constant and equal to 5N. The average diameter of the grains in the abrasive slurry is 0.01mm. The tool oscillates with an amplitude of 30 micro m at 20 KHz. The slurry contains 1 part of abrasive to about 1 part of water. The fracture hardness of tungsten carbide workpiece may be taken as 7000 N/mm2. Estimate the machining time.

 

2. A square through hole of 5mm by 5mm has to be drilled in a 5mm thick tungsten carbide sheet. The slurry is made of 1 part of 10 micro m radius boron carbide grains mixed with 1.5 parts of water. The feed force is 4N. The tool oscillates with an amplitude of 0.015mm at 25KHz. Assuming that only 20% of the pulses are effective, calculate the time required to complete the job.

 

3. In an ECM operation, a pure copper block is being machined. If a current of 5000A is used, determine the volume rate of material removal from the copper block.

 

4. The composition of a Nimonic alloy turbine blade is 18% cobalt, 62% Ni, and 20% chromium. It is being machined electrochemically with a current of 1500A. Find out the volume removal rate if the density of the alloy is 8.3g/cm3. The dissolution valency of chromium is 6, whereas that for both nickel and cobalt is 2.

 

5. The composition of a monel alloy workpiece undergoing electrochemical machining is as given here:

63% Ni, 31.7% Cu, 2.5% Fe, 2% Mn, 0.5% Si, 0.3% C

if the machining current is 1000A, estimate the volume removal rate.

 

6. The equilibrium gap when machining (electrochemically) iron, using NaCl solution in water as the electrolyte, is found to be 0.2mm. The current density is 200A/cm2, the operating voltage being 12V. Iron dissolves at a valency 2, the density of iron is 7.8 g/cm3, and the specific resistance of the electrolyte is 2.8 ohm cm. Calculate the metal removal rate/unit work surface area. The overvoltage may be taken as 1.5V

 

7. In an electrochemical trepanning operation on a flat iron surface, an electrode in the form of a tube (with an outer diameter of 1cm). A laser beam with a power intensity of 2 * 105 W/mm2 is used to drill a 0.2mm diameter hole in a tungsten sheet of 0.4mm thickness. If the efficiency of the operation is only 10%, estimate the time required.

 

8. TRUE / FALSE - Water is the main cutting tool in Ultra Sonic machining.

 

9. Why are the vibrations in USM so small?

 

10. USM will be used to add the following pattern to an object, If the tool is Tungsten carbide, and the work is Cu, with an amplitude of oscillation of 10 μm, at 30KHz, how long will the operation take? (Note: the grain diameter is 20μm, and the head has a static force of 6N)

 

11. When is the abrasive added into the flow for the various abrasive jet machining processes?

 

12. Why is the depth of material removed by abrasive jet machining so variable?

 

13. Describe the ability of the abrasive processes to produce sharp corners.