Even though the curve is not linear between the proportionality limit and the elastic limit, the material is still elastic in this region and if the load is removed at or below this point the specimen will return to its original length. P: This is the proportionality limit, which represents the maximum value of stress at which the stress-strain curve is linear.Į: This is the elastic limit, which represents the maximum value of stress at which there is no permanent set. There are several points of interest in the diagram above: The values of stress and strain determined from the tensile test can be plotted as a stress-strain curve, as shown below:Ĭheck out our Stress-Strain Curve calculator based on the methodology described here. In the equation for strain, L is the current length of the specimen and L 0 is the original length.

In the equation for stress, P is the load and A 0 is the original cross-sectional area of the test specimen. This is done by converting the load values to stress values and converting the deflection values to strain values: Since we are interested material behavior without regard to geometry, it is useful to generalize the data to remove the effect of geometry. The deflection in the test specimen is dependent on both the material's elastic modulus as well as the geometry of the specimen (area and length). These values can be plotted as a load-deflection curve.

In this test, a steadily increasing axial force is applied to a test specimen, and the deflection is measured as the load is increased. The relationship between stress and strain in a material is determined by subjecting a material specimen to a tension or compression test.

Modulus of elasticity of aluminum