Find Complete and recently updated Correct Question and answers of Material Engineering. All Answers updated regularly with new questions. Upwork Material Engineering test answers of 2016.

Question:* True or False: Interstitial diffusion occurs more rapidly than vacancy diffusion.

Answer: • True

Question:* Given a material with yield strength 310 MPa and a factor of saftey 5, what is the working stress

Answer: • 62 MPa

Question:* How can the diffusion velocity be quantified?

Answer: • Fick's law

Question:* On tensile test,does the plane of rupture says anything about the mechanical nature of the materials?

Answer: • Yes, if the material is brittle or ductile

Question:* Does the geometry have an influence on the critical failure modes that may occur on a material upon mechanical loading?

Answer: • Yes

Question:* The eutectic alloy is the alloy with lowest melting point on an eutectic system. True or false?

Answer: • True

Question:* A rod of initial length 10 cm is placed under load. The rod's new length is measured at 10.5 cm. What is the engineering strain of the material under this load?

Answer: • 0.05

Question:* Which mechanical properties can be determined from tensile test?

Answer: • Young’s Modulus, Yield strength, Rupture strength

Question:* On the martensitic transformation, the ratio between the height of the tetragonal structure in relation to the other dimensions, which are equal, depend on the carbon content. True or False?

Answer: • True

Question:* How is materials selection usually performed?

Answer: • Materials selection charts

Question:* What are the main characteristics of metals?

Answer: • High Young’s Modulus, high density, high toughness

Question:* Which one of these can be considered as defects if they exist on a material

Answer: • Gaps and dislocations

Question:* How would you determine the material properties obtained from a tensile test?

Answer: • By means of a stress-strain chart

Question:* What is the stable form of pure iron at room temperature?

Answer: • ferrite

Question:* When a metal is cooled, what happens at a microstructural level?

Answer: • Formation of Nuclei and then the growth of nuclei originating crystals

Question:* Is the material cost always the most important factor for materials selection?

Answer: • No, not always

Question:* The aim of steel quenching is to give to the material

Answer: • The maximum hardness

Question:* How are the [100] direction and the (100) plane oriented with respect to each other?

Answer: • perpendicular

Question:* An identical amount of liquid metal is poured into two moulds, one with smooth walls and one with rough walls, which are then cooled. Which batch will begin solidification at a higher temperature?

Answer: • The batch in the rough-walled mould

Question:* True or False: appreciable solid solubility requires that the solvent and the solute share a crystal structure.

Answer: • True

Question:* Which of the following is NOT a characteristic of aluminum and aluminum alloys?

Answer: • high melting temperature

Question:* Why do materials get oxidated?

Answer: • Because the reactions originating the oxidated compounds lower the energy of the system, and, this tendency depends strongly of the material

Question:* Which of the following is a typical application of low-carbon steel?

Answer: • structural steel componenets

Question:* Is it possible to determine Poisson coefficient experimentally?

Answer: • Yes, by doing a tensile test on the elastic domain

Question:* Which of the following factors does not influence diffusion?

Answer: • The electrical conductivity of the material

Question:* What is the maximum carbon content of steels?

Answer: • 2%

Question:* A copper wire or radius 3 mm is to offer no more than 10 ohms resistance. What is the maximum length of the wire, given σ = 6.0×10^7 (Ω•m)^-1 for copper?

Answer: • 17 m

Question:* Given a <2% contentration of carbon (atomic radius 0.071 nm) in iron (atomic radius (0.124 nm), will the solid solution formed be substitutional or interstitial, or will second phase form instead?

Answer: • interstitial

Question:* In non-equilibrium cooling of a binary system, what happens to the distribution of the two elements in the final grains?

Answer: • There will be a concentration gradient, with the center of the grain rich in the higher-melting element and the grain boundaries rich in the lower-melting element.

Question:* In steady-state diffusion, increasing the area across which the diffusion occurs will have what effect on the concentration profile?

Answer: • The concentration profile will have a steeper slope

Question:* What are the main characteristics of polymers?

Answer: • Low Young’s Modulus, low density, low strength

Question:* When Luders bands occur

Answer: • They can be effectively treated with a procedure which creates free dislocations

Question:* In general, at any given temperature which of the following diffusions paths is fastest?

Answer: • Diffusion along surfaces

Question:* True or False: Hardness is an absolute material property.

Answer: • False

Question:* What is the relationship between the rate of solidification and the time required for solidification to proceed to some degree of completion (e.g. time to 50% solidification comlpetion)?

Answer: • They are inversely proportional.

Question:* On crystalline solids, the dislocations :

Answer: • May be formed during solidification, but also by plastic deformation

Question:* In order to form a substitutional solid solution what must be true of the relationship between the atomic radii of the solute and solvent atoms?

Answer: • The atomic radii of the solute and solvent atoms must be close to each other

Question:* Consider two materials, with the exact same properties except the yield strength, which is higher in one of them. The material with higher yield strength:

Answer: • Yields at a higher load intensity

Question:* During heat treatment, shape distortions can occur. What is a possible solution to minimize shape distortions that occur during austenitization?

Answer: • Decrease the maximum temperature and phase time during the constant temperature phase

Question:* Which of the following iron-carbon phase is formed by a diffusionless transformation?

Answer: • martensite

Question:* Two samples of a ceramic are formed from a powdered precusor material. Subsequent to compaction and forming, sample A has 0.2 volume fraction porosity, while sample B has 0.4 volume fraction porosity. Which sample has a higher modulus of elasticity?

Answer: • A

Question:* For structural applications, what shall be the offset for the determination of the yield stress?

Answer: • 0,20%

Question:* Which will have a higher surgface free energy: a solid nucleus surrounded by liquid phase or a nucleus on a solid surface?

Answer: • a nucleus on a solid surface

Question:* If electroneutrality is to be preserved, which of the following point defects is not possible in NaCl when a Ca2+ ion substitutes for an Na+ ion?

Answer: • one Cl- substitutional

Question:* In graphite, the carbon atoms are arainged in sheets. What type of bond exists between the atoms in a sheet and what type between sheets?

Answer: • covalent, van der Waals

Question:* When a material is plastically deformed:

Answer: • The dislocations move

Question:* Plastic deformation in metals is accomplished by what process?

Answer: • slip

Question:* An increase in temperature will have what effect on the diffusion coefficient of a material

Answer: • The diffusion coefficient will increase exponenetially

Question:* On a steel, what is the effect of increasing the carbon content?

Answer: • The ductility decreases, so as the elongation

Question:* Which of the following is not a bulk property of a material?

Answer: • resistance

Question:* What happens when excess solute is added so a solution above the solution's solubility limit?

Answer: • The additional solute forms a new phase.

Question:* What happens over time to the microscruture of an alloy of two elements A and Bquenched into a spinodal region of its phase diagram?

Answer: • The initial uniform phase segregates over time into A-rich and B-rich regions.

Question:* For tools made of steel, if the part suffers fracture, the carbon content shall:

Answer: • Be decreased

Question:* What is the driving force for solidification?

Answer: • A negative change in Gibb's free energy

Question:* After steel quenching, a tempering is usually performed. The aim of the tempering is:

Answer: • To increase the toughness

Question:* The Luders bands:

Answer: • Are a characteristic of the steels with low carbon content (<0,2% wt)

Question:* When ceramics are sintered:

Answer: • Both structural strength and density increase

Question:* In a binary isomorphous system the liquidus line seperates what two phases?

Answer: • The liquid phase and a phase consisting of a mixture of liquid and solid.

Question:* When nickel is added as an alloying element to steel what is the effect?

Answer: • Decreased eutectoid temperature and eutectoid composition (wt% C).

Question:* What are auxetic geometries?

Answer: • Are geometries that stretch in the transversal direction while loaded in tension in the longitudinal direction

Question:* What is the Elasticity Modulus and what does it represent?

Answer: • It represents the stiffness of the material, without accounting the geometry, on the elastic domain only

Question:* which one of these is the material with the highest Elasticity Modulus: Low-alloy steel, Stainless steel,Titanium,Tungsten or Copper

Answer: • Tungsten

Question:* In general, which of the following orderings best describes the typical values for linear coefficient of thermal expansion for different classes of materials?

Answer: • polymers > metals > ceramics

Question:* What is The crystallographic structure of Gamma, Delta and Alpha irons?

Answer: • Delta and Alpha are body centered cubic and Gamma is face centered cubic

Question:* In a typical engineering strees-strain curve, the tensile strength of the material under test is the stress measured at what point?

Answer: • The maximum point of the curve.

Question:* Imagine that for a part subjected to mechanical loads, the aim is to have the lightest material but with the best mechanical behavior in terms of deflections. Which approach is the most effective?

Answer: • Design improvements with the aim of maximizing Inertia moment

Question:* The steels which will be plastically deformed and used to produce sheet have carbon content:

Answer: • Lower than 0,1%

Question:* Grain boundaries are defects. True or False?

Answer: • True

Question:* What kind of composite best describes concrete?

Answer: • Large-particle composite

Question:* As a solid nucleus grows, where are atoms arriving from the liquid phase most likely to attach?

Answer: • At an atomic ledge

Question:* In a sample under tensile stress the maximum stress corresponds to what phenomenon in the sample?

Answer: • The onset of necking in the deformed sample.

Question:* Vulcanization of rubber is an example of changing a thermoset to a thermoplastic via what mechanism?

Answer: • crosslinking

Question:* What effect is to be expected on the thermal conductivity of a material with a unit cell having a high degree of vibrational freedom?

Answer: • The material will have low thermal conductivity.

Question:* On an eutectic reaction, when the material is cooled:

Answer: • 1 liquid phase originates 2 solid phases

Question:* The purpose of annealing worked steel is to convert the pearlite grains that are the result of plastic deformation into what phase and microsctructure?

Answer: • Fine-grained autenite.

Question:* When a material is heated above its Curie temperature what happens to its saturation magnetization?

Answer: • The saturation magnetization drops abrubtly to 0.

Question:* For structural applications including mobile parts, what pair of properties would you consider to be most relevant for materials selection?

Answer: • Young’s Modulus, density

Question:* The temperature of an extrinsic semiconductor is raised within its extrinsic region. What is the effect on carrier concentration?

Answer: • There is no effect on carrier concentration.

Question:* How does work hardening alter the stress-strain curve of a material under tensile load?

Answer: • The slope of the stress-strain curve decreases as the material undergoes work hardening

Question:* In a cubic crystal with side length 1 what is the coordinate of the of end point of a vector in the [120] direction?

Answer: • (1/2, 1, 0)

Question:* For tools made of steel that will be working at high temperatures, shall be selected a steel that:

Answer: • May suffer secondary hardening

Question:* Equilibrium cooling of an alloy of eutectic composition results in what final composition?

Answer: • two solid phases with compositions corresponding to the ends of the eutectic isotherm

Question:* An iron-carbon alloy of eutectoid composition (0.76 wt% C) is cooled from a temperature in the γ phase region into the α + Fe3C region. What is the resultant microstructure?

Answer: • Thin alernating layers of α and Fe3C.

Question:* The coordination number for the face-centered cubic (FCC) crystal structure is:

Answer: • 12

Question:* Of these, which material would you expect the highest extension on rupture obtained on a tensile test: Magnesium, Steel-nickel, Stainless steel, Structural steel, Aluminum

Answer: • Structural steel

Question:* The diffusion of matter:

Answer: • Occurs to minimize the free energy of the system

Question:* The solid solubility of silicon in aluminum is 1.25 atomic % at 550¡C (823K) and 0.46 atomic % at 450¡C (723K). What solubility would be expected at 200¡C? (R=8.314)

Answer: • 0.006 atomic %

Question:* Copper has an FCC crystal structure. Given an atomic radius of 0.128 nm and and atomicweight of 63.54 g/mol, what is copper's theroretical density in g/cm^3?

Answer: • 8.89 g/cm^3

Question:* An increase in a material's yield strength will have what effect on its plane strain fracture toughness KIc?

Answer: • KIc will decrease.

Saturday, December 19, 2015

Material Engineering test answers of 2016

Question:* True or False: Interstitial diffusion occurs more rapidly than vacancy diffusion.

Answer: • True

Question:* Given a material with yield strength 310 MPa and a factor of saftey 5, what is the working stress

Answer: • 62 MPa

Question:* How can the diffusion velocity be quantified?

Answer: • Fick's law

Question:* On tensile test,does the plane of rupture says anything about the mechanical nature of the materials?

Answer: • Yes, if the material is brittle or ductile

Question:* Does the geometry have an influence on the critical failure modes that may occur on a material upon mechanical loading?

Answer: • Yes

Question:* The eutectic alloy is the alloy with lowest melting point on an eutectic system. True or false?

Answer: • True

Question:* A rod of initial length 10 cm is placed under load. The rod's new length is measured at 10.5 cm. What is the engineering strain of the material under this load?

Answer: • 0.05

Question:* Which mechanical properties can be determined from tensile test?

Answer: • Young’s Modulus, Yield strength, Rupture strength

Question:* On the martensitic transformation, the ratio between the height of the tetragonal structure in relation to the other dimensions, which are equal, depend on the carbon content. True or False?

Answer: • True

Question:* How is materials selection usually performed?

Answer: • Materials selection charts

Question:* What are the main characteristics of metals?

Answer: • High Young’s Modulus, high density, high toughness

Question:* Which one of these can be considered as defects if they exist on a material

Answer: • Gaps and dislocations

Question:* How would you determine the material properties obtained from a tensile test?

Answer: • By means of a stress-strain chart

Question:* What is the stable form of pure iron at room temperature?

Answer: • ferrite

Question:* When a metal is cooled, what happens at a microstructural level?

Answer: • Formation of Nuclei and then the growth of nuclei originating crystals

Question:* Is the material cost always the most important factor for materials selection?

Answer: • No, not always

Question:* The aim of steel quenching is to give to the material

Answer: • The maximum hardness

Question:* How are the [100] direction and the (100) plane oriented with respect to each other?

Answer: • perpendicular

Question:* An identical amount of liquid metal is poured into two moulds, one with smooth walls and one with rough walls, which are then cooled. Which batch will begin solidification at a higher temperature?

Answer: • The batch in the rough-walled mould

Question:* True or False: appreciable solid solubility requires that the solvent and the solute share a crystal structure.

Answer: • True

Question:* Which of the following is NOT a characteristic of aluminum and aluminum alloys?

Answer: • high melting temperature

Question:* Why do materials get oxidated?

Answer: • Because the reactions originating the oxidated compounds lower the energy of the system, and, this tendency depends strongly of the material

Question:* Which of the following is a typical application of low-carbon steel?

Answer: • structural steel componenets

Question:* Is it possible to determine Poisson coefficient experimentally?

Answer: • Yes, by doing a tensile test on the elastic domain

Question:* Which of the following factors does not influence diffusion?

Answer: • The electrical conductivity of the material

Question:* What is the maximum carbon content of steels?

Answer: • 2%

Question:* A copper wire or radius 3 mm is to offer no more than 10 ohms resistance. What is the maximum length of the wire, given σ = 6.0×10^7 (Ω•m)^-1 for copper?

Answer: • 17 m

Question:* Given a <2% contentration of carbon (atomic radius 0.071 nm) in iron (atomic radius (0.124 nm), will the solid solution formed be substitutional or interstitial, or will second phase form instead?

Answer: • interstitial

Question:* In non-equilibrium cooling of a binary system, what happens to the distribution of the two elements in the final grains?

Answer: • There will be a concentration gradient, with the center of the grain rich in the higher-melting element and the grain boundaries rich in the lower-melting element.

Question:* In steady-state diffusion, increasing the area across which the diffusion occurs will have what effect on the concentration profile?

Answer: • The concentration profile will have a steeper slope

Question:* What are the main characteristics of polymers?

Answer: • Low Young’s Modulus, low density, low strength

Question:* When Luders bands occur

Answer: • They can be effectively treated with a procedure which creates free dislocations

Question:* In general, at any given temperature which of the following diffusions paths is fastest?

Answer: • Diffusion along surfaces

Question:* True or False: Hardness is an absolute material property.

Answer: • False

Question:* What is the relationship between the rate of solidification and the time required for solidification to proceed to some degree of completion (e.g. time to 50% solidification comlpetion)?

Answer: • They are inversely proportional.

Question:* On crystalline solids, the dislocations :

Answer: • May be formed during solidification, but also by plastic deformation

Question:* In order to form a substitutional solid solution what must be true of the relationship between the atomic radii of the solute and solvent atoms?

Answer: • The atomic radii of the solute and solvent atoms must be close to each other

Question:* Consider two materials, with the exact same properties except the yield strength, which is higher in one of them. The material with higher yield strength:

Answer: • Yields at a higher load intensity

Question:* During heat treatment, shape distortions can occur. What is a possible solution to minimize shape distortions that occur during austenitization?

Answer: • Decrease the maximum temperature and phase time during the constant temperature phase