Members of uniform strength – definition in axial loading If, under axial loading, the stress at every cross-section of a bar is equal to the allowable (working) stress, the bar is referred to as a:
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ABody of equal (incomplete term)
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BBody of equal section
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CBody of equal strength (uniform strength)
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DBody of uniform section with varying stress
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EMechanism
Answer
Correct Answer: Body of equal strength (uniform strength)
Explanation
Introduction / Context:Bars can be shaped so that the maximum permissible stress is fully utilized along the entire length. This is important in weight-critical designs (e.g., ties, columns, connecting rods).
Given Data / Assumptions:
- Axial (tension/compression) loading only.
- Allowable working stress is the same everywhere.
- Bar geometry may vary to achieve uniform stress.
Concept / Approach:A body of equal (uniform) strength is one in which the cross-sectional area A(x) is adjusted along the length so that σ(x) = P/A(x) equals the allowable stress everywhere. For constant load P, this implies A(x) is constant; for members with self-weight or varying load, A(x) varies to keep σ constant.
Step-by-Step Solution:Define target: σ_allow = P/A(x) for all x.Solve for area profile: A(x) = P/σ_allow; if P varies with x (e.g., self-weight), A(x) changes accordingly.Name the concept: body of equal (uniform) strength.
Verification / Alternative check:Design texts show tapered bars under self-weight as classic examples where A increases toward the fixed end to maintain constant stress.
Why Other Options Are Wrong:
- Equal section does not guarantee equal stress unless load is constant and the bar is prismatic.
- “Body of equal (incomplete term)” is not a proper descriptor.
- “Mechanism” is unrelated.
Common Pitfalls:Confusing equal strength with equal section; the former is a stress condition, the latter is geometric.
Final Answer:Body of equal strength (uniform strength)