Elastic Properties of Solids

Cause ==> Effect

Cause ==> Deformation

"Force" ==> Deformation

What kinds of deformations will we encounter?

Length deformation

Tensile / stretch


Bulk compression

Length deformation as an example

But how can we describe the material itself--independent of the geometry?

Stress is "cause".

Stress is measured in newtons per square meters; this is known as a pascal, Pa.

1 pascal = 1 Pa = 1 [ N / m2 ]

Strain is "effect" or "result".

A modulus describes a material's behavior with regard to stress and strain. How easily is it deformed?

Length deformation

What does all this mean for length deformation -- stretching or compressing?

The "length deformation modulus" is known as Young's Modulus,


Young's Modulus is the slope of the line for the elastic region of this Stress / Strain graph.

Click here for an EXAMPLE.

Shear Modulus

Bulk Modulus

But F/A is just the pressure which we will talk about later. Therefore, we can also write the definition of the Bulk Modulus as

Notice the minus sign. This is necessary because an increase in pressure causes a decrease in volume.

Second Condition of Equilibrium

Return ToC, Static Equilibrium

(c) Doug Davis, 2001; all rights reserved