Manufacturing Processes Multiple Choice Questions on “Abrasive Jet Micromachining – 11”.
1. Water Jet Machining (WJM) and Abrasive Jet Micromachining (AJMM or AWJM) can be achieved using how many different approaches?
a) 10
b) 5
c) 7
d) only one approach is there
Answer: c
Clarification: WJM and AWJM can be achieved using different approaches and methodologies as enumerated below:
WJM – Pure
WJM – with stabilizer
AWJM – entrained – three phase – abrasive, water and air
AWJM – suspended – two phase – abrasive and water
Direct pumping
Indirect pumping
Bypass pumping.
2. In AJMM, water at _____ MPa is pumped.
a) 100-150
b) 200-400
c) 200-300
d) 370-500
Answer: b
Clarification: Water is pumped at sufficiently high pressure, 200-400 MPa (2000-4000 bars) using intensifier technology. An intensifier works on the simple principle of pressure amplification using hydraulic cylinders of different cross-sections as used in jute bell presses.
3. In pure WJM, commercially pure water is used.
a) True
b) False
Answer: a
Clarification: In pure WJM, commercially pure water (tap water) is used for machining purpose. However as the high velocity water jet is discharged from the orifice, the jet tends to get dispersed in the atmosphere.
4. To stop the dispersion of the water jet in the atmosphere ______ is used.
a) sodium Carboxylate
b) acrylonitrile
c) long chain polymers
d) silica gel
Answer: c
Clarification: However as the high velocity water jet is discharged from the orifice, the jet tends to entrain atmospheric air and flares out decreasing its cutting ability. Hence, quite often stabilisers (long chain polymers) that hinder the fragmentation of water jet are added to the water.
5. In entrained type AWJM, abrasive water jet has a velocity of around _____ m/s.
a) 100
b) 220
c) 650
d) 800
Answer: d
Clarification: In entrained type AWJM, the abrasive particles are allowed to entrain in water jet to form abrasive water jet with a significant velocity of 800 m/s. Such high velocity abrasive jet can machine almost any material.
6. Which of the following materials, is not machined using abrasive water jet machining?
a) Diamond
b) Concrete
c) Stone – Granite
d) Reinforced plastics
Answer: a
Clarification: The materials which are generally machined using abrasive water jet machining, are given below:
Steels
Non-ferrous alloys
Ti alloys, Ni- alloys
Polymers
Honeycombs
Metal Matrix Composite
Ceramic Matrix Composite
Concrete
Stone – Granite
Wood
Reinforced plastics
Metal Polymer Laminates
Glass Fibre Metal Laminates.
7. For which of the following operations, abrasive water jet machining is not used?
a) Peening
b) Pocket milling
c) Mass immunization
d) Cutting hard materials
Answer: d
Clarification: The abrasive water jet machining can be used for:
Paint removal
Cleaning
Cutting soft materials
Cutting frozen meat
Textile, Leather industry
Mass Immunization
Surgery
Peening
Cutting
Pocket Milling
Drilling
Turning
Nuclear Plant Dismantling.
8. Assuming no losses, what will be the water jet velocity, when the water pressure is 4000 bar, being issued from an orifice of diameter 0.3 mm?
a) 212 m/s
b) 467 m/s
c) 592 m/s
d) 894 m/s
Answer: d
Clarification:
9. What will be the mass flow rate of water, when the water pressure is 4000 bar, being issued from an orifice of diameter 0.3 mm, assuming all related coefficients to be 1?
a) 1 kg/min
b) 2.89 kg/min
c) 3.26 kg/min
d) 3.79 kg/min
Answer: d
Clarification: Mass flow rate of water, mw = ρ*Q where, ρ = density of water and Q = discharge of the jet.
mw = ρ*Q
= ρ*(π*d2/4)*v
= 1000*3.14*0.00032*894
= 3.79 kg/min
Where, d= diameter of the orifice.
10. Addition of hard and sharp abrasive particles into the water jet can increase the cutting ability of the jet.
a) True
b) False
Answer: a
Clarification: The cutting ability of water jet machining can be improved drastically by adding hard and sharp abrasive particles into the water jet. Thus, WJM is typically used to cut so called softer materials and AWJM is used for relatively harder materials.