ME or MEng Master of Engineering Structural Analysis and Materials Science 2 — Questions and Answers
Question 1: Face-centered cubic (FCC) crystal structures are generally:
- Brittle and hard
- Ductile and have many slip systems (Correct answer)
- Magnetic and high-strength only
- Found only in ceramics
Correct answer: Ductile and have many slip systems
FCC metals (Al, Cu, Au, Ni) have 12 slip systems, enabling significant plastic deformation and high ductility.
Question 2: The stress intensity factor K_I in fracture mechanics represents:
- Average stress across the cross section
- Stress amplification at a crack tip under Mode I (opening) loading (Correct answer)
- The yield strength reduction factor
- Impact energy absorbed per unit area
Correct answer: Stress amplification at a crack tip under Mode I (opening) loading
K_I = σ√(πa)·Y quantifies the stress field magnitude at a Mode I crack tip; fracture occurs when K_I reaches the material's fracture toughness K_IC.
Question 3: Fatigue failure in metals typically initiates at:
- The center of the cross section under tension
- Grain boundaries in the bulk material
- Surface stress concentrations or defects (Correct answer)
- The neutral axis of a bending member
Correct answer: Surface stress concentrations or defects
Fatigue cracks nucleate at surface irregularities, notches, or stress concentrators where cyclic stresses are locally amplified.
Question 4: In a simply supported beam with a central point load P and span L, the maximum bending moment is:
- PL/4 (Correct answer)
- PL/8
- PL/2
- PL
Correct answer: PL/4
For a simply supported beam with central load P, M_max = PL/4 at midspan, derived from the bending moment diagram.
Question 5: Which heat treatment process diffuses carbon into the surface of low-carbon steel to increase surface hardness?
- Annealing
- Quenching
- Carburizing (Correct answer)
- Normalizing
Correct answer: Carburizing
Carburizing exposes low-carbon steel to a carbon-rich atmosphere at elevated temperature, enriching the surface layer with carbon for increased hardness.
Question 6: The modulus of resilience for a material is defined as:
- Area under the stress-strain curve up to fracture
- Stress at the proportional limit squared divided by twice the elastic modulus (Correct answer)
- Ultimate strength times elongation to fracture
- Yield strength divided by Young's modulus
Correct answer: Stress at the proportional limit squared divided by twice the elastic modulus
Modulus of resilience U_r = σ_y²/(2E) is the energy per unit volume that a material can absorb elastically without permanent deformation.
ME or MEng Master of Engineering Structural Analysis and Materials Science 2
Face-centered cubic (FCC) crystal structures are generally: