This set of Manufacturing Processes Questions and Answers for Entrance exams focuses on “Ultrasonic Machining – 3”.
1. USM is a material removal process used to _____ material.
Explanation: It is a material removal process, used to erode material in the form of fine holes and cavities in hard or brittle workpieces. It uses formed tools, vibrations of high frequency and suitable abrasive slurry-mix.
2. During USM, the workpiece is thermally affected.
Explanation: USM is a non-thermal and non-chemical process which creates no change in the chemical, physical or metallurgical properties of the work piece. It is therefore, widely used in the manufacturing of hard and brittle materials, which are commonly infeasible to a machine by other non-traditional methods.
3. In USM, material removal occurs due to _____
a) abrading action
b) corroding action
c) chemical action
d) chip formation
Explanation: Ultrasonic machining accomplishes the material removal through the abrading action of the grit-loaded slurry which is kept circulated between the tool and the workpiece. The cutting is actually performed by the abrasive particles which are suspended in the slurry.
4. During USM, which of the following vibrates at ultrasonic frequency?
a) Slurry mix
d) Abrasive particles only
Explanation: The tool is vibrated at ultrasonic frequency and this will be in the range of 20 kHz. The slurry is made to flow through this in this zone so that the abrasive particles will come in contact with the workpiece.
5. Material removal in USM can be attributed to _____ mechanisms.
Explanation: Following are the mechanisms that could be attributed to the material removal in USM;
• Hammering, that causes brittle fracturing of the work material
• Impact action of abrasives
6. The development of USM was started in _____
Explanation: The development of USM was started in 1927. It was accidentally discovered during investigating the ultrasonic grinding of abrasive powders.
7. The abrasive grains are driven by the reciprocations across the gap in between the tool and the work piece.
Explanation: The abrasive grains are driven by the high speed reciprocations across the small gap in between the tool and the work piece, as already discussed. Uniform force is used to gradually feed the tool. The impact of the abrasive is the energy source that is mainly responsible for material removal. Due to the impact of abrasives, the material removal takes place in the form of small particles, which are carried away by the abrasives slurry.
8. Which of the following is true about USM?
a) There is direct contact between the tool and the workpiece
b) There is no direct contact between the tool and the workpiece
c) This process is not suitable for machining of brittle materials
d) This process consumes very less power
Explanation: There is no direct contact of the tool and the work piece due to the slurry used and it makes it a wet cutting process the surfaces so produced are free from stress and damages. This process is free from burrs and distortions. However, the process is very much suitable for machining brittle materials.
9. Which of the following materials is not suitable for USM?
Explanation: Soft materials like lead and plastics are not suitable for machining by this process, since that they tend to absorb the abrasive particles rather than the chip under the impact.
10. During USM __________ is converted into mechanical vibrations.
a) pressure energy of the slurry
b) electrical energy
c) chemical energy of the chemical used for the slurry
d) mechanical energy of the tool
Explanation: During USM, high frequency electrical energy is converted into mechanical vibrations through a transducer. The high frequency vibrations are transmitted to the abrasive particles in the slurry via an energy focusing device called horn or tool assembly.
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