This set of Materials Science Multiple Choice Questions & Answers (MCQs) focuses on “Ductile Fracture”.
1. Necking occurs in which of the following fractures?
a) Ductile fractures
b) Brittle fracture
d) It doesn’t occur during fracture
Explanation: Necking occurs when tensile force is applied on metals and it occurs when ductile failure is occurring. In brittle fracture the material just breaks before breaking.
2. In ductile fracture, at what angle to the tensile axis does the crack propagate outwardly to the surface of the material?
Explanation: The crack propagates outwardly to the surface of the material at an angle of 45° to the tensile axis and this type of fracture is called “cup and cone fracture”.
3. At the point of necking which of the following is false?
a) Strain hardening occurs at this point
b) Cross sectional area increases
c) Cross sectional area decreases
d) Strength increases
Explanation: At the point of the necking the strength increases due to strain hardening and the cross-sectional areas decreases at the same time. At the time where cross sectional area decreases faster than necking starts.
4. Ductile fracture happens after extensive plastic deformations.
Explanation: Unlike brittle fracture, ductile fracture happens after extensive plastic deformation and goes through multiple visible stages before the final fracture is observed.
5. Which of the following cannot be a reason for ductile failure?
a) Error in design
b) Improper material
c) Improper manufacturing techniques
d) Unforeseen operating condition
Explanation: Ductile fracture is a slow process with many steps and under unforeseen operating conditions if the fracture is going to occur it will be noticeable and can be avoidable.
6. After which point is necking observed?
a) Ultimate strength
b) Yield strength
c) Elastic point
d) Fracture point
Explanation: Necking in a ductile material is observed after the body crosses the point of ultimate strength on the stress-strain curve.
7. What is the amount of strain in a stable neck is called?
a) Natural draw ratio
b) Forced draw ratio
c) Poisson’s ratio
d) Physical activity ratio
Explanation: Natural draw ratio is the name given to the amount of strain in a stable neck during necking of a material under load.
8. Material subjected to only tensile force even during necking.
Explanation: Material during necking due to high dislocation density is subjected to a complex stress. At this point, the material isn’t subjected only a single tensile force.
Sanfoundry Global Education & Learning Series – Materials Science.
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