In tensile testing of ductile materials, how does ductility vary with the percentage reduction in area measured at fracture?
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AIncreases
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BDecreases
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CRemains the same
Answer
Correct Answer: Increases
Explanation
Introduction / Context:Ductility quantifies a material’s ability to undergo plastic deformation before fracture. Common measures include percentage elongation and percentage reduction in area (%RA) of the fractured specimen.
Given Data / Assumptions:
- Ductile material under a standard tensile test.
- % reduction in area = (A0 − Af) / A0 * 100% at the necked fracture section.
- Question asks the relation between ductility and %RA.
Concept / Approach:A higher percentage reduction in area indicates greater plastic flow and necking before failure, which is the hallmark of higher ductility. Thus, ductility correlates positively with %RA.
Step-by-Step Solution:
Record initial cross-sectional area A0.After fracture, measure minimum area Af at the neck.Compute %RA = (A0 − Af) / A0 * 100%.Interpretation: larger %RA → more plastic deformation → higher ductility.Verification / Alternative check:Comparing specimens: one with greater necking (smaller Af) displays higher ductility as observed by both % elongation and %RA.
Why Other Options Are Wrong:“Decreases” or “remains the same” contradict the definition of %RA as a ductility measure.
Common Pitfalls:Confusing %RA with strength; %RA is not a strength metric but a plasticity indicator.
Final Answer:
Increases