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Difficulty: HardTypes of Stress and Strain

As long as the applied tensile stress on a structural steel tie-rod remains below its ultimate tensile strength, the rod will undergo only elastic deformation and will completely return to its original length when the load is removed.

Answer: Answer

Answer

False
The correct answer is False. A material only returns completely to its original dimensions if the applied stress stays below its yield strength (or elastic limit). If the applied stress exceeds the yield strength but remains below the ultimate tensile strength, the material undergoes plastic deformation, resulting in a permanent physical change.

Step-by-Step Solution

1
Analyze the mechanical properties mentioned in the statement.
The statement asserts that keeping stress below the 'ultimate tensile strength' guarantees 'elastic deformation' (returning to original length).
Identifying the specific mechanical thresholds is necessary to evaluate material deformation.
2
Compare the definitions of ultimate tensile strength and yield strength.
Yield strength marks the end of the elastic region where deformation is reversible. Ultimate tensile strength is the maximum stress the material can handle before breaking, which occurs well into the plastic (irreversible) region.
The stress-strain curve defines distinct zones of material behavior based on applied load.
3
Evaluate the statement's conclusion based on material mechanics.
If stress exceeds the yield strength but stays below the ultimate tensile strength, the tie-rod experiences plastic deformation and will not completely return to its original length.
Therefore, using ultimate tensile strength as the boundary for elastic deformation is factually incorrect.

Key Concept

Yield Strength vs. Ultimate Tensile Strength in Elastic and Plastic Deformation
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Topics

Types of Stress and Strain

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