Multiple choice question for engineering
1. The eutectic point in the iron-iron carbide phase diagram occurs at __________ weight % composition of carbon.
Answer: d [Reason:] The iron-iron carbide equilibrium diagram is constructed by plotting the composition of carbon against the temperature. At 4.3 weight % of carbon, eutectic point is formed.
2. At what temperature does δ ferrite melt?
a) 1674 F
b) 1990 F
c) 2541 F
d) 2800 F
Answer: d [Reason:] δ ferrite is formed as a BCC phase due to heating of austenite at 2541 F. This δ ferrite finally melts at 2800 F and these changes are plotted on the iron-iron carbide equilibrium diagram.
3. What is the solubility of α ferrite at 0oC?
Answer: c [Reason:] α ferrite is an interstitial solid solution of carbon in a BCC crystal lattice. It has a solubility of 0.02% at 723oC and decreases to 0.005% at 0oC.
4. What is the crystal structure of austenite upon heating?
a) Body-centered cubic
b) Face-centered cubic
c) Hexagonal closely packed
d) Body-centered tetrahedral
Answer: b [Reason:] At room temperature, ferrite exists as a BCC crystal as seen on the iron-iron carbide equilibrium diagram. Upon heating, this changes into austenite in FCC form at 1674 F.
5. How much iron does cementite contain?
Answer: d [Reason:] Cementite is an intermetallic compound of iron-carbon (Fe3C). It has a solubility that is negligible with a composition of 6.67% C and 93.3% Fe.
6. What is the maximum solubility of carbon in austenite at 1148oC?
Answer: c [Reason:] Austenite is an FCC crystal with a solubility of 2.08% at 1148oC which decreases to 0.8% at 723oC. δ ferrite has a maximum solid solubility of 0.09% at 1465.
7. At what temperature does peritectic reaction occur?
Answer: b [Reason:] In a peritectic reaction, 0.53% C of liquid combines with 0.09% C of ferrite at 1495oC. This results in the formation of ϒ austenite (0.17% of C).
8. Peritectic reactions are applicable for carbon contents up to _________
Answer: c [Reason:] In a peritectic reaction, 0.53% C of liquid combines with 0.09% C of ferrite at 1495oC. This results in the formation of ϒ austenite (0.17% of C). This reaction affects only solidification of steels with less than 0.55% carbon.
9. How much austenite does eutectic reaction form?
Answer: a [Reason:] In a eutectic reaction, 4.7% C of liquid at 1148oC forms ϒ austenite (2.08% of C) and Fe3C (6.67% of C). This reaction holds great importance for cast irons.
10. At what temperature does eutectoid reaction occur?
Answer: c [Reason:] In a eutectoid reaction, 0.8% C of ϒ austenite at 723oC forms α ferrite (0.02% of C) and Fe3C (6.67% of C). This reaction holds great importance for heat treatment of steels.
1. What is the specific gravity of magnesium?
Answer: a [Reason:] Magnesium is a silvery-white metal which has a specific gravity of only 1.74. It also has a low weight of 1.73 gm/cu cm. The specific gravities of aluminum and copper are 2.7 and 8.9 respectively.
2. What is the melting point of magnesium?
Answer: b [Reason:] Magnesium is a common element which has a melting point of 650oC and a boiling point of 1091oC. It weighs less than aluminum, iron, and steel. It has the lowest density among common structural elements.
3. Which of the following is not a property of magnesium?
a) Low strength
b) Vulnerable to corrosion
Answer: d [Reason:] Pure magnesium is not used due to its low strength. It is also prone to corrosion, due to which it is usually painted on. Since magnesium is costly, it is used only in cases where weight is a priority. This comes to use due to its low weight.
4. Magnalium is an alloy of magnesium, ________
a) Nickel and Tin
b) Zinc and Tin
c) Nickel and Zinc
d) Zirconium and Zinc
Answer: a [Reason:] Magnalium, although considered an aluminum alloy, may contain over 50% magnesium and small amounts of nickel and tin. They are commonly used for engineering applications and pyrotechnics.
5. How does a high amount of magnesium affect alloys?
a) Increases strength
b) Increases corrosion resistance
c) Lowers density
d) Becomes brittle
Answer: d [Reason:] Alloys with around 50% magnesium are more brittle and prone to corrosion. However, lesser quantities (5%) result in increased strength, corrosion resistance, low density, and weldability.
6.Dow metal contains ______ of magnesium.
Answer: d [Reason:] Dow metal is an alloy of magnesium which contains 90% magnesium, 10% aluminum, and a small amount of manganese. It is extremely lightweight and easy to weld and machine. They are commonly employed in automobile and aircraft applications.
7. Which of the following is a type of aluminum alloy with magnesium?
Answer: c [Reason:] Birmabright is an aluminum alloy containing 1-7% magnesium and less than 1% manganese. They have good weldability, and corrosion resistance to seawater. The leftover choices are a few magnesium alloys.
8. A magnesium alloy containing 3% rare earth metal exhibits which of the following characteristics?
a) Creep resistance up to 250oC
b) Good founding properties
c) Die-casting alloy
d) Good overall properties
Answer: a [Reason:] A magnesium alloy containing rare earth metal (3%) is a type of cast alloy. It also contains 2.5% of zinc and 0.6% zirconium. It has a creep resistance up to 250oC. It is also pressure tight, weldable, and has excellent castability.
9. Which of the following alloys is used in nuclear reactors?
Answer: b [Reason:] Magnox is a magnesium alloy used for which is used to contain fission products in nuclear reactors. It stands for Magnesium Non-Oxidising. Elektron is mainly used in aerospace and race car applications, whereas Mag-Thor is used in aerospace industry. Megnelium is used in pyrotechnics.
1. The continuous phase of a composite material is known as its _______
a) dispersed phase
b) surrounding phase
c) matrix phase
d) fiber phase
Answer: c [Reason:] Composite materials contain mostly two phases: matrix and dispersed phase. Matrix phase is a continuous phase which tends to bind the fibers together. It also protects them from damage and is used to transmit the load.
2. Which of the following structures represents that of a fiber composite?
Answer: c [Reason:] Fiber-reinforced composites are those which contain fiber form in its dispersed phase. When these fibers are parallel to each other, they exhibit high strength.
3. How is the critical length or a composite material defined?
Answer: b [Reason:] The critical length of a material is determined using the diameter of the fiber, ultimate strength, and its yield strength. The critical length of the fiber is required for strengthening of the composite materials.
4. The classification of fibers having thin crystals is known as _______
Answer: a [Reason:] Whiskers are thin single crystals having an extremely large length-to-diameter ratio. Due to their small size, they have high crystalline perfection. Fibers are polycrystalline materials of small diameters, whereas wires have large diameters.
5. Which of the following materials are common for whiskers?
a) Graphite, silicon carbide
b) Glass, boron
c) Steel, tungsten
d) Polymers, ceramics
Answer: a [Reason:] Whiskers are single crystals having large ratios of length to diameter. The common materials are graphite, silicon nitride, aluminum oxide etc. Glass and boron fall under the category of polymers of fibers. Steel, tungsten, and molybdenum are commonly used as wires.
6. Kevlar is a ______ type of material
Answer: d [Reason:] Kevlar is a polymer type of fiber material. Kevlar-epoxy and Kevlar-polyester are common fiber reinforced composites commonly used in aerospace applications, sports goods, flak jackets etc.
7. Which of the following is not a characteristic trait of composite materials?
a) High strength, toughness, modulus
c) Easy to assemble
d) Sensitive to temperature change
Answer: d [Reason:] Composite materials have great mechanical properties, corrosion resistance, are easy to assemble, and light in weight in case of fiber composites. They aren’t very sensitive to thermal shocks and temperature changes. However, they are more expensive than conventional materials.
8. How much SiO2 is present in the glass which is drawn into fibers?
Answer: a [Reason:] Glass which is rolled into thin fibers is known as E-glass. This glass contains 55% of SiO2 and Al2O3(15%), B2O32 (10%), and MgO (4%). It is quite the preferred type of fiber-reinforcement material.
9. Fiberglass materials have a usable temperature up to ______
Answer: c [Reason:] Fiberglass materials have a low service temperature which is below 200oC. This is despite the fact that they usually have high strength. These materials also have a great impact resistance and are extremely flexible.
10. What is the purpose of a fiberglass that is made as a thread?
a) Insulating material
b) Conductive material
c) Heat resistant
Answer: d [Reason:] Fiberglass is either made into a staple or thread. The thread type is used to make cloth for various applications. It is also colored and can be manufactured by a continuous process. Staple type (up to 15 inches long), on the other hand, is used as an insulating material.
11. The below figure depicts the structure of ________ composite materials.
Answer: c [Reason:] A laminar composite is a subcategory type of structural composites with a varying orientation for each layer. These composite materials are used for their high strength.
12. The below figure is an example of ______ type of structural composites.
b) Sandwich panel
d) Randomly oriented
Answer: b [Reason:] Sandwich panels are a type of structural composites having a low-density material covered by layers of high-density material on its faces. Aluminum alloys and fiber-reinforced plastics are commonly used as face materials which bear the load. Randomly oriented composite is a type of discontinuous composite, which itself is a type of fiber-reinforced composite.
13. Manufacturing of components having continuous lengths and constant cross-sectional shape is done by _____ process.
Answer: b [Reason:] Pultrusion is a process used to fabricate continuous fiber-reinforced plastics. By this method, they can work at high production rates, thereby making it less expensive. It is also easily automated.
14. What amount of principle reinforcement materials is used in pultrusion process?
Answer: c [Reason:] The principle reinforcements used in pultrusion process are glass, carbon and aramid fibers. These are added in concentrations between 40 to 70%. The matrix materials used are polyesters, vinyl esters, and epoxy resins.
1. The tendency of a deformed solid to regain its actual proportions instantly upon unloading known as
a) Perfectly elastic
b) Delayed elasticity
c) Inelastic effect
Answer: a [Reason:] If the recovery of the solid is instantaneous and complete, it is known as perfectly elastic. Delayed elasticity is defined as the steady mode of solid recuperation, while the inelastic effect is when the recuperation of deformed solid is partial. Plasticity is the contradictory occurrence of elasticity.
2. How is Young’s modulus of elasticity defined?
Answer: c [Reason:] The ratio of load to the area
is the description of stress on the solid. The ratio of alteration in length to its original length
is the description of strain on the solid. Young’s modulus of elasticity is defined as the ratio of stress on the solid to the strain of the solid
The ratio of the mass of the solid to its volume
is defined as density.
3. The permanent mode of deformation of a material known as _____________
c) Slip deformation
d) Twinning deformation
Answer: b [Reason:] Plasticity is defined as the property of a material due to which it is permanently deformed due to loading. Elasticity is the temporary form of deformation. Twinning and Slip are mechanisms of Plastic deformation.
4. The ability of materials to develop a characteristic behavior under repeated loading known as ___________
Answer: d [Reason:] Toughness is the ability of a material to absorb energy during deformation, while resilience is its capacity to absorb the energy. Hardness is the knack of a material to defy indentation. The ability of a material to develop a characteristic behavior under repeated loading is known as fatigue.
5. What is the unit of tensile strength of a material?
Answer: b [Reason:] Tensile strength is defined as the ratio of maximum load (kg) applied to its cross-sectional area (cm2). Young’s modulus of elasticity is defined as the ratio of stress on the solid to the strain of the solid. The remaining choices given are reciprocals of same.
6. Which of the following factors affect the mechanical properties of a material under applied loads?
a) Content of alloys
b) Grain size
c) Imperfection and defects
d) Shape of material
Answer: d [Reason:] Contents of alloys improve or decrease the hardness and strength of materials. Finer grain sizes improve the strength of the material. Imperfection and defects reduce the strength of the material. Shape, however, has little or no effect on the material.
7. The ability of a material to resist plastic deformation known as _____________
a) Tensile strength
b) Yield strength
c) Modulus of elasticity
d) Impact strength
Answer: b [Reason:] The point of stretching where it increases suddenly is known as yield strength, i.e. the region where the stretch is elastic. Tensile strength is the force needed to fracture the material. Impact strength is the capacity of a material to resist shock energy before a fracture.
8. The ability of a material to be formed by hammering or rolling is known as _________
Answer: a [Reason:] The capacity of a material to withstand deformation under compression, i.e. hammering is known as malleability. The capacity of a material to withstand deformation under tension, i.e. wire drawing is known as ductility. Hardness is the knack of a material to oppose indentation. Brittleness is the tendency to fracture without deformation of the material.
9. What type of wear occurs due to an interaction of surfaces due to adhesion of the metals?
a) Adhesive wear
b) Abrasive wear
c) Fretting wear
d) Erosive wear
Answer: a [Reason:] Adhesive wear occurs due to frictional contact between metals. Abrasive wear occurs due to the descending of the surface of the material over a different harder surface. Fretting wear is the wear which causes the deduction of material from both the surfaces in contact over an extended period of time. Erosive wear causes wear of the material due to the effect of solid or liquid particles over a short period of time.
10. Deformation that occurs due to stress over a period of time is known as ____________
a) Wear resistance
Answer: c [Reason:] Creep is the time-dependent deformation of the material under stress. Wear resistance, fatigue, and fracture deal with deformation under stress without a time factor, i.e. they are time-independent.
1. Creep occurs at a temperature above ________
a) 0.16 Tm
b) 0.22 Tm
c) 0.4 Tm
d) 0.91 Tm
Answer: c [Reason:] Creep is defined as the permanent deformation of a material due to the application of steady load. It is appreciable only at temperatures above 0.4 Tm.
2. __________ experiences creep at room temperature.
Answer: d [Reason:] Room temperature is about the same as that of the melting point of lead. Therefore, nickel experiences creep at that temperature under its own load. The room temperature of iron and copper is 0.16 Tm and 0.22 Tm respectively, at which creep does not occur.
3. _______ is known as steady-state creep.
a) Primary creep
b) Secondary creep
c) Tertiary creep
d) Quaternary creep
Answer: b [Reason:] Creep occurs in three stages known as primary, secondary, and tertiary creep. Secondary creep is also known as steady-state creep since the rate of work and recoveries are equal.
4. Which of the following does not affect creep?
a) Grain size
b) Thermal stability
c) Chemical reactions
d) Crystal structure
Answer: d [Reason:] Coarse-grained materials and those having higher thermal stability generally affect creep resistance of a material. The chemical reaction involved and work hardening also influence the creep resistance.
5. The time required for occurrence of creep is known as _________
a) Creep resistance
b) Creep life
c) Creep limit
d) Creep recurrence
Answer: b [Reason:] Creep life is defined as the time required for the occurrence of creep fracture in a material under static load. Creep limit is defined as the maximum static stress that will result in creep. Creep resistance is known as the resistance offered by the material over creep.
6. Which of the following will be rendered useless for prevention of creep?
a) Coarse-grained material
b) Strain hardening
c) Precipitation hardening
Answer: d [Reason:] Creep fracture can be prevented by using coarse-grained materials and treatment by strain hardening a precipitation hardening. The material must be free from residual stresses and can also be heat treated.
7. MgO and Al2O3 can be used at high temperature creep resistance due to _________
a) High melting point
b) High oxygen concentration
c) Low density
d) Chemical stability
Answer: a [Reason:] Creep starts to occur at a temperature higher than 0.4 Tm. Therefore, high melting point materials like MgO and Al2O3 are used for high-temperature operations.
8. Iron base alloys have melting point around __________
Answer: b [Reason:] The most commonly used high-temperature alloys are iron base, nickel base, and cobalt base alloys. Each of these alloys possesses a high melting point temperature of around 1500oC.
9. Strengthening of iron base, nickel bade, and cobalt base alloys is done by __________
a) Precipitation hardening
b) Grain boundary hardening
c) Dispersion hardening
d) Transformation hardening
Answer: c [Reason:] Iron base, nickel base, and cobalt base alloys have creep resistance around a temperature of 0.5 Tm. Their creep resistance can be improved by a heat treatment process known as dispersion hardening.
10. Why can’t cold working be used for strengthening in case of plastic deformation?
b) Thermal instability
c) Lowers tensile strength
d) Introduces coarsening
Answer: a [Reason:] At temperatures above 0.4 Tm, recrystallization occurs readily. This results in loss of strength of the cold-worked material. Therefore, for plastic deformation, cold working is generally avoided for creep resistance.