What approximate percentage reduction in cross-sectional area occurs during a tensile test of cast iron__________________?
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Answer: C. 0%
Explanation
Cast iron is a brittle material that exhibits virtually zero percentage reduction in cross-sectional area during a tensile test. Brittle materials fracture suddenly under tensile loading without undergoing significant plastic deformation or necking. The lack of dislocation movement in the graphite flake microstructure prevents any measurable macroscopic elongation or area reduction. Cast iron contains a high percentage of carbon, primarily in the form of graphite flakes that act as internal stress concentrators. Ductile metals show large area reductions exceeding fifty percent, whereas brittle materials fail elastically with minimal permanent strain. Standard tensile tests on grey cast iron reveal brittle cleavage fracture surfaces perpendicular to the applied tensile load.
A fifty percent reduction in cross-sectional area is typical for highly ductile metals like low-carbon steel or aluminum alloys. A twenty-five percent reduction represents moderately ductile materials rather than brittle engineering cast irons. Suggesting higher percentage reductions ignores the fundamental brittle fracture mechanics governing gray and ductile cast irons.
- Subject
- Engineering
- Category
- Mechanical Engineering
- Topic
- —
- Difficulty
- medium
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