11.5 STRESS STRAIN CURVES

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For low carbon steel,

While necking, the cross section at one point decreases, thus increasing the stress. In turn this continues rapidly until fracture.

The strain hardening of some materials occurs as they are stretched, the Ultimate Tensile Strength increases, but Young's modulus remains the same.

Each material will have it's own stress-strain curve and these are determined experimentally, and found in abundance in handbooks.

If a material is brittle, it does not deform much and simply breaks. Or simply the ultimate and rupture strengths are the same.

Ductile materials deform quite a bit before the ultimate stress, necking typically occurs before rupture.

The area under the stress strain curve indicates toughness. A larger area under a stress strain curve will make a material that must be extensively deformed before it will fail.

Creep is an effect that can lead to permanently elongated specimens,