Describe the behaviour of a wire under gradually increasing load.

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> [!TLDR]
> As load increases, a wire shows: proportional region (Hooke's law) -> elastic limit -> yield point (permanent set begins) -> ultimate stress (maximum) -> fracture point (wire breaks). This is described by the stress-strain curve.
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> When a wire is subjected to a gradually increasing load (tension), its behaviour is described by the stress-strain curve, which passes through the following stages:
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> 1. Proportional region (O to A):
> For small loads, the stress is directly proportional to the strain - the wire obeys Hooke's law. The graph is a straight line. The point A up to which this holds is called the proportional limit.
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> 2. Elastic limit (A to B):
> Slightly beyond the proportional limit, up to a point B (the elastic limit), the wire is still elastic - it returns exactly to its original length when the load is removed, though stress is no longer strictly proportional to strain.
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> 3. Yield point (B to C):
> If the load is increased beyond the elastic limit, the wire reaches the yield point. Beyond this, the wire does not return to its original length even after removing the load - it acquires a permanent set (plastic deformation). Strain now increases rapidly for little increase in stress.
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> 4. Plastic region and ultimate (maximum) stress (up to D):
> With further loading the wire deforms plastically and reaches the point of maximum stress it can bear, called the ultimate tensile strength (or breaking stress), at point D.
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> 5. Fracture (breaking) point (E): …

Q.Describe the behaviour of a wire under gradually increasing load.

Concept understanding — Youngs Modulus

Young’s Modulus: The Stretchiness of a Solid

The Intuition: Stiffness per Unit Size

The Precise Definition

What the Number Tells You

A Worked Example

Q.Describe the behaviour of a wire under gradually increasing load.

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