Engineering Questions with Answers - Multiple Choice Questions
Manufacturing Processes – Abrasive Jet Micromachining – 11
1 - Question
Water Jet Machining (WJM) and Abrasive Jet Micromachining (AJMM or AWJM) can be achieved using how many different approaches?
d) only one approach is there
Explanation: 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 - Question
In AJMM, water at _____ MPa is pumped.
Explanation: 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 - Question
In pure WJM, commercially pure water is used.
Explanation: 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 - Question
To stop the dispersion of the water jet in the atmosphere ______ is used.
a) sodium Carboxylate
c) long chain polymers
d) silica gel
Explanation: 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 - Question
In entrained type AWJM, abrasive water jet has a velocity of around _____ m/s.
Explanation: 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 - Question
Which of the following materials, is not machined using abrasive water jet machining?
c) Stone – Granite
d) Reinforced plastics
Explanation: 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 - Question
For which of the following operations, abrasive water jet machining is not used?
b) Pocket milling
c) Mass immunization
d) Cutting hard materials
Explanation: 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 - Question
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
9 - Question
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
Explanation: 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 - Question
Addition of hard and sharp abrasive particles into the water jet can increase the cutting ability of the jet.
Explanation: 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.