Material testing and characterization Quiz-1

Answer: b
Explanation: TS = 3.45 × HBN
TS = 3.45 × 149
= 514.05
~ 514 MPa
Here, HBN = Brinell hardness, TS = tensile strength of material in MPa.

Answer: b
Explanation: Equation Δσ_y = Gb√ρ shows the relation between dislocation density generated through work hardening and yield stress. Here, Δσ_y is changed in yield strength, b is a magnitude of burgers vector, G is the shear elastic modulus and ρ is a density of dislocations after work hardening. This equation shows that as dislocation density increases yield strength of material increases.

Answer: b
Explanation: Elastic energy of dislocation is proportional to the square of Burgers vector. It is given by E_elastic = lGb². Here l is length, G is shear modulus and E is an elastic energy of dislocation.

Answer: a
Explanation: A Burgers vector represents the extent of slip. The extent of slip may also be referred as an extent of plastic deformation. Burgers vector represents a magnitude of slip.

Answer: b
Explanation: Bulk modulus is reciprocal of compressibility of material. It is expressed as K = E/3(1 – 2v). Here E is elastic modulus and v is Poisson’s ratio

Answer: a
Explanation: The atomic density is 4/√3a² on {1 1 1} plane in fcc. √2/a² is on {1 1 0} plane. While 2/a² is on {1 0 0} plane.

Answer: c
Explanation: Lowest elastic modulus is of Lead and its alloys of 14-18 GPa. Ni and Mo alloys have elastic modulus of 180-214 and 330-360 GPa respectively. Al₂O₃ has highest E among the four of 415 GPa.

Answer: a
Explanation: Ductility is calculated by percentage elongation. It is the ability of a material to undergo plastic deformation. It is opposite of brittleness.

Answer: c
Explanation: Steels with UTS 1500 MPa or above are high strength steels. Steels which have UTS lesser than 1500 MPa are not high strength alloys.

Answer: d
Explanation: Transient creep is the predominate process below 0.5 T_m. Above 0.5 T_m, diffusion starts taking place and recovery determines work hardening.