Previous: 5.1(b) The Elastic Solid and Elastic Boundary Value Problems
If
is
Cauchy tensor and
is
small strain tensor, then in general,
where
is
the fourth order elasticity tensor, since
is
a tensor,
However,
we know that
then
We have
symmetric
matrix with 36 constants,
If
elasticity is a unique scalar function of stress and strain, strain energy is
given by
Now
consider that there is one plane of symmetry (monoclinic) material, then
One
plane of symmetry
13
If
there are 3 planes of symmetry, it is called an ORTHOTROPIC material, then
orthotropy
3
planes of symmetry
9
Where
there is isotropy in a single plane, then
Planar
isotropy
5
When the material is completely isotropic (no dependence on orientation)
Isotropic
2
Crystal
structure |
Rotational
symmetry |
Number
of independent elastic constants |
Triclinic Monoclinic Orthorhombic Tetragonal Hexagonal Cubic Isotropic |
None 1
twofold rotation 2
perpendicular twofold rotations 1
fourfold rotation 1
six fold rotation 4
threefold rotations |
21 13 9 6 5 3 2 |
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Chapter 5 Overview