Stress-strain curve in Tension
Ductile materials undergo a large amount of
deformation before failing. The following figure
shows the stress-strain curve for a ductile
specimen:
Proportional Limit: This limit is represented by point A on the graph. Up to this limit, the
stress and the strain induced in the specimen are directly proportional to each other, i.e.
the specimen obeys Hooke’s law. Beyond this point, the stress is not proportional to the
strain.
Elastic Limit: This limit is represented by point B on the graph. Upto this limit, the material
is said to be elastic. This implies that the specimen regains its original shape and
dimensions after the removal of the external load. There are no residual deformations
seen in the specimen, on removal of the load. After this point, the material is said to
become plastic.
, Yield Point: Contrary to what the name suggests, this is a region rather than a point. It is
limited by the upper yield point ‘C’ and the lower yield point ‘D’. The stress – strain curve
in this part of the graph is almost horizontal, which implies that there is an appreciable
increase in strain for a negligible increase in stress. Yielding starts at ‘C’ and ends at ‘D’.
After the point ‘D’, the material, due to strain hardening again starts taking load and the
curve rises, as seen in the figure. The material now is said to be plastic and the
deformation is of nearly permanent nature.
Ultimate Stress: This is shown by the point ‘E’ on the graph. It represents the maximum
stress that a material can take before it fails. The specimen however does not fail at this
point. After this point, the curve starts dropping.
Fracture Point: This is the point at which the specimen fails. After the ultimate stress
point, necking of the specimen takes place, which causes a loss in the load carrying
capacity of the specimen and ultimately causes it to fail. This point is represented on the
curve, by point ‘F’.
Ductile materials undergo a large amount of
deformation before failing. The following figure
shows the stress-strain curve for a ductile
specimen:
Proportional Limit: This limit is represented by point A on the graph. Up to this limit, the
stress and the strain induced in the specimen are directly proportional to each other, i.e.
the specimen obeys Hooke’s law. Beyond this point, the stress is not proportional to the
strain.
Elastic Limit: This limit is represented by point B on the graph. Upto this limit, the material
is said to be elastic. This implies that the specimen regains its original shape and
dimensions after the removal of the external load. There are no residual deformations
seen in the specimen, on removal of the load. After this point, the material is said to
become plastic.
, Yield Point: Contrary to what the name suggests, this is a region rather than a point. It is
limited by the upper yield point ‘C’ and the lower yield point ‘D’. The stress – strain curve
in this part of the graph is almost horizontal, which implies that there is an appreciable
increase in strain for a negligible increase in stress. Yielding starts at ‘C’ and ends at ‘D’.
After the point ‘D’, the material, due to strain hardening again starts taking load and the
curve rises, as seen in the figure. The material now is said to be plastic and the
deformation is of nearly permanent nature.
Ultimate Stress: This is shown by the point ‘E’ on the graph. It represents the maximum
stress that a material can take before it fails. The specimen however does not fail at this
point. After this point, the curve starts dropping.
Fracture Point: This is the point at which the specimen fails. After the ultimate stress
point, necking of the specimen takes place, which causes a loss in the load carrying
capacity of the specimen and ultimately causes it to fail. This point is represented on the
curve, by point ‘F’.
