Tensile Test, Part Two

Please read the previous part of this article here

The typical stress strain curve for ductile material is given here: 

The points to note from this picture are:

Elastic Limit

  The material is elastic till this point in the curve. The stress strain ratio is constant when the curve is linear within this zone. The material deforms in this zone but regains original shape and size once the load is removed. The working stress is always much below the Elastic Limit

Yield Point:

   Plastic deformation happens at this point. The deformation is permanent in nature and the original shape and size are not restored once the load is removed.

Creep:

   A small amount of creep may come into play due to sudden elongation of material. This effect of creep is not shown in this picture. Creep usually appears for negligible time and is not taken into account.

Ultimate Strength:

    Stress is necessary to obtain stain from the yield point onwards. Ultimate tensile strength (UTS), is the maximum stress that a material can withstand while being stretched or pulled before necking, which is when the specimen's cross-section starts to significantly contract. This is the highest point in the curve

Fracture Point:

    Once the Ultimate stress is crossed, the material starts necking (i.e. non-uniform reduction in area of cross section in specimen). The material then breaks apart.

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