Modulus of Elasticity

•  Modulus of Elasticity ; The initial slope of the stress-strain diagram within the elastic  limit gives the modulus of elasticity .       

In finding this slope the tangent of the angle between the curve and the x-axis can be easily calculated by using a multiple of unity as the strain value . In material having a curved diagram the modulus of elasticity is taken as the tangent at the origin.

For material such as concrete the actual working stresses lie somewhat above the straight portion of the diagram; there will actually be a slight permanent set in such material under working loads. In such ta case it is desirable to consider the modulus of elasticity to be the slope of the secant line drawn from the origin to be the point curve corresponding to the unit stress.

Fig. Method of Finding 
the (secant) Modulus of 
Elasticity