This set of Manufacturing Processes Multiple Choice Questions & Answers (MCQs) focuses on “Ultrasonic Machining – 4”.
1. Which of the following is true about USM?
a) In USM, tool needs to be changed frequently
b) USM consumes less power
c) USM can be used for soft materials
d) In USM, workpiece is vibrated at ultrasonic frequency
Explanation: In USM tool needs to be replaced more frequently because;
• the tool end is susceptible for wear during the process
• soft corners of the tool get rounded off quickly
Due to these reasons, generally hard material like steel is used for the tool.
2. In USM, the bottom surfaces of blind holes tend to become concave due to _____
a) insufficient slurry circulation
b) resistance to abrasive particles
c) ineffective slurry circulation
d) high frequency of the vibrations
Explanation: The holes produced in ultrasonic machining have a tendency to break out at the bottom owing to the static load and high amplitudes. While producing deeper holes through USM method, there is ineffective slurry circulation leading to the presence of the fewer active grains under the tool face. Due to this, the bottom surfaces of the blind holes tend to become slightly concave.
3. Which of the following pumps is used in USM?
a) Re-circulating pump
b) Centrifugal pump
c) Vane pump
d) Reciprocating pump
Explanation: In USM, A re-circulating pump forces abrasive suspended in a liquid medium between the vibrating tool face and work piece. Then the tool shaped like the cavity to be produced oscillates at amplitude of about 0.013 to 0.062 mm at 19 to 40 kilo hertz. The tool vibrates abrasive grains against the surface of the work piece, thus removing the material.
4. Which of the following is not a part of the ultrasonic machine used in USM?
b) Acoustic head
c) Slurry pump
Explanation: The basic ultrasonic equipment consists of, a generator for high frequency oscillations; an acoustic head, consisting of a transducer and a horn also known as shank or trunk; also, tool and abrasive slurry elements like pump and tank for slurry.
5. The primary purpose of the transducer is _____
a) to make uniform mixture of the slurry and the abrasive particles
b) to take filter the slurry after the operation
c) to convert energy
d) to cool the tool
Explanation: The generator is responsible for transmitting electrical power to the transducer, which creates energy impulses in the ultrasonic range. That is sometimes starting from 18 kilo hertz onwards. The energy pluses are then converted into mechanical vibrations. The primary function of the transducer is to convert these electrical impulses into vertical and two dimensional strokes. Sometimes it can be horizontal as well, depending on the configuration of the machine.
6. The acoustic head consists of how many parts?
Explanation: The acoustic head is considered as the heart of the whole equipment and this mainly consists of two parts. The transducer, which converts the high frequency output of the generator into linear vibrations, the number two the horn or the trunk, which mechanically amplifies the linear vibrations.
7. Which of the following is not the alternative name for the trunk in USM?
Explanation: It is a critical link in the ultrasonic machining system. This is known by several names such as shank, horn, concentrator and amplifier as well. The trunk amplifies and focuses vibration of the transducer to require the intensity, necessary enough for driving the tool.
8. Tool in USM is subjected to vibratory loads.
Explanation: The tools are designed to provide the maximum amplitude of vibration at the free end, the selection of the tool material is very important as the tool tip is subjected to vibration and it must not fail due to wear.
9. The tool is joined to the trunk by _____
a) riveted joint
b) welded joint
Explanation: The tool is attached to the trunk or the horn by silver brazing process. At times it is fasten or the screwed to the trunk also. The commonly used tool materials are brass, high speed steel, mild steel, silver, stainless steel, tungsten carbide and monel metal.
10. Tool geometry does not affect the performance of the USM process.
Explanation: The shape of the tool (solid or hollow), mechanical properties of the materials used in tool making are some of the parameters that may affect the performance of the USM process significantly.
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