What approximate percentage area reduction occurs in a cast iron test specimen during tension testing_________________?
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Answer: E. negligible
Explanation
Cast iron is a brittle material that exhibits negligible plastic deformation during tension testing. Graphite flakes in its microstructure act as internal stress concentrators, causing sudden brittle fracture. Because it fractures with virtually no necking, cross-sectional area reduction remains practically zero. Cast iron contains high carbon percentages, resulting in a hard and brittle matrix structure. Tensile tests on gray cast iron show almost entirely elastic behavior up to the breaking point. Ductile materials exhibit significant necking and large area reductions before final tensile failure.
Engine block and machine bed castings utilize cast iron for its compressive strength and vibration damping. Engineers never rely on cast iron for structural components subjected to high tensile shock loads. Recognizing brittle fracture behavior prevents catastrophic failures in heavy industrial machinery design. More than 50% area reduction is typical for highly ductile metals like soft copper or aluminum. Moderate reductions of 25 to 50% occur in medium carbon structural steel tension tests. Lower ranges like 5 to 10% characterize semi-brittle materials rather than extremely brittle cast iron.
- Subject
- Engineering
- Category
- Mechanical Engineering
- Topic
- —
- Difficulty
- medium
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