Question

Describe the Diagrammatic Stress Displacement Curve and which strength should be used and when.

Answer 1

Stress-Displacement/ strain curve for elastic and plastic ragion shown below. Stress-strain curve is basically relation between the load applied to a component/ specimen and the resulting displacement of that component under the load. A stress-strain curve is made of up two main parts: the elastic region and the plastic region. Elastic means that when the load is released, the geometry will return to its initial position. Once a load is large enough to cause a stress higher than the yield strength, then it enters the plastic region of the stress-strain curve. In the plastic region, the material deforms in such a way that when the load is removed, the material does not return to its initial shape. The point at which the component was loaded up to now becomes the new yield point of the material.

Once a load is large enough to cause a stress higher than the yield strength, then it enters the plastic region of the stress-strain curve. In the plastic region, the material deforms in such a way that when the load is removed, the material does not return to its initial shape. The point at which the component was loaded up and becomes the new yield point of the material.

This occurs up until the point on the curve where the material no longer experiences strain hardening and it begins to "neck." "Necking" is where we begin to differentiate between an engineering and logarithmic (true) stress-strain curve.

Yeild strength shall be used in elastic regin which is nothing but maximum stress before plastic deformation.

Ultimate tensile strength shall be used in plastic region, which could be the maximum tress any where in the plastic region.