This set of Mechanical Metallurgy Multiple Choice Questions & Answers (MCQs) focuses on “Extrusion Equipments”.
1. In the forward extrusion process, the speed of the extruded product is __________ the speed of the ram.
a) lower than
b) greater than
c) same as
d) depends upon the material softness
Explanation: By the volume consistency in the rule:
-> So if the area of the final product is lower, its speed should be higher and vice versa.
2. In the indirect extrusion process, the ram and extruded product both travel in the same direction.
Explanation: In the case of indirect extrusion, the ram and extruded product both travel in opposite directions. In the die there is hole, so there is a limitation in allowable stress on the workpiece.
3. For very thin diameter wire, the lubricant used is in the form of ___________
b) molten glass
c) electrolyte coating of copper
d) phosphate coating of manganese
Explanation: To draw wires of very thin diameters, the electrolyte coating of copper is used. The dry and aqueous soap solution is used for low and high-speed thick wire drawing.
4. The production of the toothpaste tube is made by which of the following process?
b) Tube extrusion
c) Impact extrusion
d) Sheet metal forming
Explanation: The toothpaste tube is manufactured by impact extrusion method. It is an indirect extrusion method. For thinner polymer-based sample, extrusion serves optimum load and shape property.
5. The nozzle for the extrusion process is manufactured using which of the following material?
c) White cast iron
d) Grey cast iron
Explanation: The white cast iron has martensite in its matrix. The martensite provides optimum strength to die and provides high wear resistance against the extruding material.
6. Nature of force in wire drawing process is ___________
c) both tensile and compressive
d) tensile, compressive and shear-type
Explanation: In wire drawing, the main force is the only tensile force on the material. While in forging, it is compression and in blanking, it is pure shear in nature.
7. The brittle material is extruded in the hydrostatic pressure extrusion process. Whereas ductile metal can be extruded through normal operations.
Explanation: The hydrostatic pressure extrusion does not apply excessive force on any one side of the component, so it increases the ductility of the material. Therefore, the brittle material can be extruded without breaking the workpiece.
8. The force required for in direct extrusion is ____________ direct extrusion process.
a) greater than
b) lesser than
c) same as
d) depends upon the material
Explanation: The force required for indirect extrusion is lesser than direct extrusion because there is a relative movement between the workpiece and chamber in direct extrusion while in indirect extrusion there is no relative movement, so the force required to overcome the friction is saved.
9. The total capacity of a hammer in forging is not dependent of _____________
a) weight of hammer
b) velocity of hammer
c) height of falling
d) type of power supply
Explanation: The power supply is dependent on the different type of machines, but in the end, the capacity of forging hammer is decided by weight of hammer, velocity of hammer, height of falling hammer.
10. The sticking between the workpiece and the die occurs when the feed rate is very high, and there is a significant difference between static and dynamic friction.
Explanation: The statement is false. There should be a considerable difference between the static and dynamic friction, but the feed rate should be very low to cause sticking of the material.
11. If the initial temperature of the billet is high, the extrusion pressure will be __________ as compared to billet having a lower temperature.
d) cannot predict
Explanation: If the initial billet temperature is high, the required stress to cause the plastic deformation will be lower. This is because of lower stress for dislocation movement. That is why billet is heated before practicing extrusion.
12. For an extruded material like a rod, the outer surface of the product will be _______ while the inner surface will be __________ and surfaces appearance is also _______
a) hard, soft, smooth
b) soft, hard, smooth
c) hard, soft, rough
d) soft, hard, rough
Explanation: In the extrusion process, the extruded product such as the rod will have a hard outer surface because of thermal quenching, while the inner surface remains relatively soft. The appearance of the surface is better than rolling in this case.
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