This set of Basic Engineering Materials and Metallurgy Questions and Answers focuses on “Mechanical Tests on Metals, Protection Against Wear”.
1. Tensile testing of metals is done using _________
a) Universal Testing Machine
d) Uniaxial Testing Machine
Explanation: The tensile test is one of the most widely used of the mechanical tests. This can be performed by using a Universal Testing Machine. The UTM can not only perform the tensile test, but also compressive tests.
Explanation: Various mechanical properties of materials are calculated using the stress-strain curve. The module of toughness is defined as the product of ultimate tensile strength and the percentage elongation.
3. The compressive test is done on which of the following materials?
a) Cast iron
Explanation: Since brittle materials are unsuitable for tension test, they are checked using a compressive test. Brittle materials such as cast iron, concrete, mortar, brick, and ceramics are commonly tested in compression.
4. Which of the following is not a method of shear test?
a) Double sheer system for round bar
b) Double knife shear system for rectangular section
c) Double shear system for conical surfaces
d) Shearing of disc using punch and die
Explanation: There are basically three main systems for shear tests. First is a double shear system for round bar test-pieces using a fork and eye device. Second is a double knife shear system for a specimen of rectangular section. Lastly, the shearing of a disc from sheet materials using a punch and die.
5. ________ plating is used for protection against wear in lead bearings.
Explanation: The wear resistance of a metal part can be improved by electroplating a harder metal on its surface. The metals often plated on base metals are chromium, nickel, and rhodium. Indium plating is used to reduce wear of lead bearings.
6. What are the applications of chromium plating?
b) Wheel and rims
c) IC engine parts
Explanation: The high corrosion-resistance of chromium is useful for reducing wear under corrosive conditions. Chromium plating is used in the cylinders and piston rings of internal combustion engines. The two types of chromium plating used are hard chromium and porous chromium.
7. What is the hardness of a rhodium plate?
a) 140-425 Vickers
b) 540-640 Vickers
c) 720-880 Vickers
d) 950-1050 Vickers
Explanation: The hardness of rhodium plate is between 540 and 640 Vickers and it has a wear resistance between that of nickel plate and chromium plate. The hardness of chromium plate is 950-1050 Vickers, whereas that of nickel plate is 140-425 Vickers.
8. The alumilite process uses ________ as an electrolyte for anodizing.
a) Sulfuric acid
b) Hydrogen peroxide
c) Nitric acid
d) Ammonium sulfate
Explanation: The anodizing process is usually applied to aluminum, magnesium, zinc, and their alloys. The alumilite process was developed by the Aluminum Company of America. This process uses sulfuric acid as an electrolyte for anodizing.
9. Which of the following is a use for flash anodic coatings?
a) Cartridge cases
b) Airplane propeller
c) Paint adherence
d) Hydraulic pistons
Explanation: The production of the hard wear-resistant surface by anodizing has greatly extended the uses of magnesium and its alloys. Flash anodic coatings are often used as a base for paint adherence. Anodizing of zinc produces a coating which has a greater resistance to wear than chromite films.
10. Chromizing is carried out at a temperature of __________
a) 400-600 F
b) 800-1200 F
c) 1650-2000 F
d) 2250-2750 F
Explanation: The chromizing process employs the principle of transfer of chromium through the gas phase at elevated temperatures. This temperature ranges between 1650 and 2000 F. This process is used on drop-forging dies, tools, hydraulic rams, pistons, and pump shafts.
11. Siliconizing is otherwise known as _________
Explanation: Siliconizing consists of impregnation of an iron-base material with silicon. Siliconizing is a diffusion process done to improve wear resistance. It is otherwise also known as Ihrigizing.
12. __________ is used as a catalyst in siliconizing.
a) Hydrogen peroxide
b) Chlorine gas
c) Sulfuric acid
d) Magnesium sulfate
Explanation: In siliconizing, the work is heated in contact with a silicon-bearing material such as silicon carbide. Here, chlorine gas is used as a catalyst. This process is carried out at a temperature of 1700-1850 F.
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