Multiple choice question for engineering
1. The tendency of a ductile material to act as brittle is known as __________
d) Notch sensitivity
Answer: d [Reason:] Some ductile materials are likely to behave as a brittle material in the presence of notches. This behavior is termed as notch sensitivity of the material.
2. What is the V-notch angle found on an impact testing machine?
a) 30 degrees
b) 45 degrees
c) 60 degrees
d) 90 degrees
Answer: b [Reason:] Both Izod and Charpy tests are conducted on the same machine with only a minor change. Both tests share the V-notch angle characteristic which is 45 degrees.
3. What is the size of the specimen used Charpy test?
Answer: c [Reason:] Charpy and Izod are the two impact testing methods used for impact testing of materials. The Charpy test employs the usage of a test specimen of size 55 mm * 10 mm * 10 mm.
4. The specified fixed in the vise signifies a ________ form.
b) Fixed beam
c) Simply supported beam
d) Overhanging beam
Answer: a [Reason:] Izod test uses a cantilever specimen of size 75*10*10 (mm) for impact testing. The specimen is placed in the vise such that it is a cantilever.
5. What is the depth of notch seen in impact testing methods?
a) 2 mm
b) 5 mm
c) 9 mm
d) 12 mm
Answer: a [Reason:] Charpy and Izod are the two impact testing methods used for impact testing of materials. Both the methods share a V-notch angle of 45 degrees and same depth of notch of 2 mm.
6. Which of the following is not applicable for fatigue fracture?
a) Loss of strength
b) Loss of ductility
c) Loss of electrical conductance
d) Uncertainty in strength and service life
Answer: c [Reason:] Fatigue fracture is defined as the fracture that takes place under repeatedly applied fatigue stresses. It results in loss of strength, ductility, and increased underinsured strength and service life.
7. The fatigue fracture occurs __________
a) Below yield stress
b) Below tensile stress
c) At stress-strain point
d) Above tensile stress
Answer: b [Reason:] Fatigue fracture is defined as the fracture that takes place under repeatedly applied fatigue stresses. It generally occurs at stress well below the tensile stress of the materials.
8. What kind of stress does this graph show?
a) Reversed stress
b) Fluctuating stress
c) Irregular stress
d) Constant stress
Answer: b [Reason:] There are basically three kinds of stress cycles of fatigue loading. The graph in the question illustrates that of a fluctuating stress. Reversed stress is similar to fluctuating stress but it travels in both quadrants of the graph. Irregular stress is the third kind of stress cycle observed.
9. Fatigue of materials is characterized by ________ curve.
Answer: c [Reason:] In case of high-cycle fatigue, a Wohner curve is used to depict its performance. This is also known as an S-N curve. This curve plots of the stress applied to the number of cycles till failure occurs.
10. How can the mean stress of fatigue be evaluated?
a) Pascal’s equation
b) Soderberg equation
c) Heisenberg’s equation
d) Goodman relation
Answer: d [Reason:] The Goodman diagram is used to plot the mean stress against the alternating stress. This is used to show when a material fails under a number of cycles. This is also known as the Haigh diagram or Haigh-Soderberg diagram.
11. The stress below which the material does not fail is called _________
a) Fatigue stress
b) Endurance limit
c) Fatigue life
d) Total stress
Answer: b [Reason:] Fatigue limit or endurance limit is defined as the value of stress below which the material does not fail even as it is loaded for infinite number of cycles. The total number of cycles required go bring about the final fracture is called fatigue life.
1. Which of the following is an application of asbestos?
b) Conduction of heat
c) X-ray tubes
d) Optical glass
Answer: a [Reason:] Asbestos is a common insulation material used for fireproofing and in buildings or industrial applications. Natural asbestos is found in rocks and has a density equal to that of the rock.
2. What kind of mineral is Chrysotile?
Answer: b [Reason:] Chrysotile is the most important mineral type of asbestos, accounting for close to 93% of the asbestos production. It is a hydrated magnesium silicate formed from a group of serpentine mineral. They have good fire resistance, are flexible, and tough.
3. Which of the following is a characteristic of asbestos minerals?
a) Poor strength
b) Heat resistance
c) Poor bonding
d) Reacts with acids
Answer: b [Reason:] Asbestos minerals are highly preferred in their fibrous form. They possess high strength, surface area, and good bonding characteristics. They are also resistant to heat, acids, and moisture.
4. What is the specific heat of Chrysotile?
Answer: b [Reason:] Chrysotile is the most preferred mineral of asbestos. However, it has a poor resistance to acids and alkalies. Its specific heat is 0.266 BTU/lb/F.
5. Which is of following is not an asbestos mineral?
Answer: d [Reason:] Asbestos is a term used to describe a list of minerals. These fibrous minerals are chrysotile, amosite, crocidolite, actinolite, tremolite, and anthophyllite. Pyroceram, on the other hand, is a type of glass.
6. What makes up the primary composition of glass?
Answer: c [Reason:] Glass is primarily composed of SiO2 with over 70% in bulb and bottle glass, and over 80% in Pyrex. K2O Is generally found having a composition of less than or around 1%. MgO and BaO aren’t found in Pyrex but are available in bottle and bulb glass having less than 4%.
7. Pyrex glass is otherwise known as _________ glass.
a) soda lime
b) fused silica
Answer: c [Reason:] Pyrex is a glass mainly used for manufacturing laboratory equipment. It is more commonly known by the name of borosilicate glass. This glass has a low expansion coefficient and a good spalling resistance.
8. Pyroceram glass softens above ______
Answer: b [Reason:] Pyroceram is a common glass type of crystalline glass. This crystalline glass softens above 2000oC and has a low specific heat of about 0.1.
9. Cork is composed of _____ air.
Answer: d [Reason:] Cork is an insulating material made from the outer bark of oak trees. It is composed of at least 50% air, which makes it one of the lightest solids. It has a specific gravity of around 0.25.
1. Which of the following varnishes is oxidizing in nature?
c) Heat-reactive baking
Answer: a [Reason:] Varnishes are films of protective covering over particular materials. The three types of varnishes are air-drying, heat reactive baking (polymerization), and solventless. The air-drying type of varnishes is oxidizing and non-heat reactive in nature.
2. Dissolved resins in alcohol produce ______ varnishes.
Answer: c [Reason:] Spirit varnishes, either clear or black, are created by dissolving natural and synthetic resins in alcohol. These turn into a hard surface which acts as an excellent coating.
3. Which of the following is not a property of insulating varnishes?
a) Moisture resistance
b) Abrasion resistance
c) Electric strength
d) Oil receptive
Answer: d [Reason:] Insulating varnishes are used to protect a material with a film. These are mainly used in electrical units which contain magnet wire, which need to be protected. These insulating varnishes possess resistance against insulation, moisture, chemical, abrasion, and thermal resistance, as well as being oil proof.
4. Silicone varnishes have a ______ operation.
a) Class A
b) Class B
c) Class F
d) Class H
Answer: d [Reason:] Silicone varnishes are available as either 100% silicones or alkyd-modified silicones. The 100% silicones are operated in Class H. The Class H operations are carried out at 180oC.
5. Acrylic varnishes are generally used in _______ gases.
Answer: c [Reason:] Acrylic varnishes are dispersions of acrylonitrile polymers. These are used with refrigerant gases like R-12 and R-22. When they come in contact with moisture, the dielectric strength is lowered.
6. What kind of varnishes are used for most temperatures or classes?
Answer: b [Reason:] Polyester varnishes are high-temperature insulators. They are used in three classes at 105oC, 130oC, and 155oC. Silicone varnishes are used at 180oC.
7. At what temperature is Class F operation carried out?
Answer: b [Reason:] Insulating varnishes are used for high-temperature insulation. The Class F operation is carried out at 155oC. Class A, Class B, and Class H are operated at 105oC, 130oC, and 180oC in that order.
8. Which of the following is not a coating method for varnishes?
a) Dip impregnation
b) Vacuum impregnation
c) Thick coat
d) Flow coat
Answer: c [Reason:] Insulating varnishes must be coated for protection against adverse effects. Dip impregnation is used for electrical gear, vacuum impregnation is used for solventless varnishes, and flow coat is used in bulky transformers.
1. Quenching of austenite steel for martempering is done using __________
b) Still air
c) Cooling tower
d) Hot oil
Answer: d [Reason:] For martempering, the steel is first heated above its critical range to make it austenitic. Then it is quenched in hot oil or molten salt above martensite start temperature.
2. How can temperature differences between center and surface be prevented?
a) Refined grain structure
b) Cooling to room temperature
c) Hot working
d) Addition of silicon
Answer: b [Reason:] Cooling the steel at moderate to room temperature prevents temperature differences between center and surface. This is usually done in air. The resulting microstructure of martempered steel is untempered martensite.
3. Martempering process is usually employed in _________
a) Alloy steels
b) Cast irons
Answer: a [Reason:] Martempering is an interrupted quenching process which eliminates some disadvantages of rapid cooling. It is used to minimize stresses, distortion, and cracking of steels. This process is usually used in alloy steels.
4. Martempering is otherwise known as __________
a) Interrupted quenching
d) Isothermal quenching
Answer: b [Reason:] Interrupted quenching is a technique of eliminating the disadvantages caused by rapid cooling. This consists of two methods, martempering and austempering. Martempering is also known as marquenching, and austempering is also known as isothermal quenching.
5. Austempering forms a _________ structure.
Answer: b [Reason:] Austempering is an isothermal heat treatment process used to reduce distortion caused by quenching and to make tough and strong steels. It forms a bainite structure and is otherwise known as isothermal quenching.
6. It is necessary to carry out _________ after martempering.
c) Surface hardening
Answer: b [Reason:] Untempered martensite structure is transformed into tempered martensite structure by conventional tempering heat treatment processing rapid quenching. This is rarely needed in austempering.
7. Which of the following is not a disadvantage of austempering?
a) Needs to be cold worked
b) Needs special bath
c) Can be used for limited steels
d) Can only be used for small sections
Answer: a [Reason:] Austempering experiences a number of disadvantages compared to quenching and tempering. It needs a special molten salt bath and can be used only for a limited number of steels. Furthermore, only small sections up to 9 mm thickness can be used.
8. Why are bigger sections not used in austempering?
a) Unable to cool
b) Does not fit in working apparatus
c) Decreased strength
d) Cannot be cut
Answer: a [Reason:] Big sections cannot be used for austempering as they cannot be cooled rapidly to avoid the formation of pearlite. As a result, only small sections up to 9 mm thickness are suitable for this operation.
1. Alloys containing 2.0-6.7% carbon are considered as __________
Answer: b [Reason:] Due to availability, low-cost, and their properties, iron and steel are used in more than 90% of the total usage of metals in the world. Steels are those alloys containing 0.06-2.0% carbon, whereas cast-irons contain 2.0-6.7% carbon.
2. The existence of two or more crystal structures for any substance, depending on temperature, is known as _________
Answer: a [Reason:] Allotropy is defined as the possibility of the existence of two or more different crystal structures for a substance depending on temperature. This phenomenon is known as polymorphism. Pure iron is an allotropic metal.
3. Pure iron exists in ________ allotropic forms.
Answer: c [Reason:] Allotropy is defined as the possibility of the existence of two or more different crystal structures for a substance depending on temperature. Pure iron is an allotropic metal that exists in three forms. These allotropic forms are α iron, ϒ iron, and δ iron.
4. What is the crystal structure of ϒ iron?
a) Body-centered cubic
b) Face-centered cubic
c) Hexagonal closely packed
d) Body-centered tetrahedral
Answer: b [Reason:] Pure iron exists in three allotropic phases of α iron, ϒ iron, and δ iron. α iron and δ iron appear as body-centered cubic, whereas ϒ iron is a face-centered cubic that is stable between 908oC and 1535oC.
5. At what temperature range is δ iron stable?
a) Up to 908oC
Answer: c [Reason:] Pure iron exists in three allotropic phases of α iron, ϒ iron, and δ iron. δ iron is a body-centered cubic that is stable around 1388-1535oC. α iron and δ iron are stable up to 908oC and between 908-1535oC respectively.
6. Which of the following is applicable to α iron?
d) Can be hot worked
Answer: d [Reason:] α iron is one of the three available allotropic forms of pure iron. It is also known as a ferrite. This form of iron is soft, ductile, highly magnetic, and can be extensively cold worked.
7. Which of the following is a nonmagnetic iron?
Answer: b [Reason:] Austenite, commonly known as ϒ iron, is an allotropic form of pure iron. It is soft, tough ductile, and nonmagnetic (paramagnetic), but has a better electrical resistance and coefficient of expansion than that of ferrite.
8. Cementite is magnetic up to ________
Answer: b [Reason:] Cementite (Fe3C) is an intermetallic compound of iron containing 6.69% of carbon. It is hard, brittle, and is magnetic below 250oC.
9. What microconstituent of iron-carbon alloys does this diagram illustrate?
Answer: d [Reason:] Sorbite is the microstructure containing ferrite and cementite. This is produced by tempering martensite above 450oC. Sorbite steels are also known as toughened steels owing to their tensile and yield strengths being high.
10. ___________ is a mixture of radial lamellae of ferrite and cementite.
Answer: a [Reason:] Troostite is a microstructure containing ferrite and finely divided cementite. This is produced by tempering martensite below 450oC. In other words, it is a mixture of radial lamellae of ferrite and cementite. It differs from pearlite only due to the degree of fineness.
11. Which microconstituent of iron-carbon alloys does this figure demonstrate?
Answer: a [Reason:] Pearlite is the eutectoid mixture containing ferrite in 87.5% and cementite in 12.5%. It forms due to the decomposition of austenite during cooling. This pearlite is strong, hard, and brittle.
12. ___________ is a eutectic mixture of α iron and Fe3C.
Answer: c [Reason:] Ledeburite is known as the eutectic mixture of α iron (austenite) and Fe3C (cementite) containing 4.3% carbon. It forms at 1140oC in the pure iron-carbon alloy.