FRACTURES SET 04

FRACTURES SET 04

1. Fracture always occurs above yield stress.
a) True
b) False

Answer: b

2. In ____ fracture, crack is unstable and propagates rapidly.
a) Ductile
b) Brittle
c) Shear
d) Tensile

Answer: b

3. Brittle fracture is a break in a brittle piece of metal that failed because stress exceeds _____
a) Cohesion
b) Adhesion
c) Yield stress
d) Tensile stress

Answer: a

4. Which of the followings is not a type of fracture in brittle materials?
a) Bright granular
b) Flat type
c) Neck
d) Chevron patterns

Answer: c

5. The crack may be __________ and ____________ depending on strength of grain boundaries.
a) Brittle, ductile
b) Trans granular, intergranular
c) Shear, cleavage
d) Fibrous, granular

Answer: b

6. In intergranular fracture, crack travels along grain boundaries.
a) True
b) False

Answer: a

7. In which type of brittle fracture, crack travels through grain boundaries?
a) Trans granular
b) Intra granular
c) Intergranular
d) Fibrous

Answer: c

8. Which theory explains brittle fracture?
a) Griffith
b) Cottrell
c) Taylor
d) Dislocation

Answer: a

9. What is the expression for maximum stress at the tip of crack?
a) σmax = 2 σ (ar)1/2
b) σmax = 2 σ (a/r) 1/2
c) σmax = 2 σar
d) σmax = 2 (σar)1/2

Answer: b

10. Elastic strain energy is proportional to ____________
a) (a)1/2
b) a
c) a2
d) a3

Answer: c