## Elastic Properties of Solids

Cause ==> Effect

Cause ==> Deformation

"Force" ==> Deformation What

kindsof deformations will we encounter?Length deformationCompressionTensile / stretch

Shear

Bulk compression

Length deformation as an exampleBut how can we describe the

materialitself--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 / m ^{2}]

Strain is "effect" or "result".

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

Length deformationWhat 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 linefor theelastic regionof this Stress / Strain graph.Click herefor anEXAMPLE.

Shear Modulus

Bulk ModulusBut F/A is just the

pressurewhich we will talk about later. Therefore, we can also write the definition of the Bulk Modulus asNotice the minus sign. This is necessary because an

increase in pressure causes adecrease in volume.

Second Condition of EquilibriumSummaryReturn ToC, Static Equilibrium(c) Doug Davis, 2001; all rights reserved