Biomedical Engineering Reference
In-Depth Information
Z, draw direction
α
y
x
β
2.9
Coordinate axes used to defi ne orientation.
z
hk
1
α
ϕ
y
α
/2
x
2.10
Stereographic projections - defi nition of the poles.
Texture on a microscopic scale, microtexture, is determined by transmis-
sion and scanning electron microscopy (TEM and SEM), and more recently
by micro-IR and micro-Raman and by microbeam X-ray diffraction tech-
niques. Orientation distribution in polymers is usually broad, and in any
one pole fi gure only the orientation of one set of crystallographic planes is
drawn, such as a (200), (020) or a (110) pole fi gure.
25
These pole fi gures are
essentially orientation probability contours. Representative pole fi gures of
some simple orientation modes are given in Fig. 2.11.
An alternative to pole fi gures is to describe the orientation of the one
of the crystal axes (chain-axis) with a reference axis (draw direction).
This description, the orientation distribution function (ODF), is widely
used because it can be used across several techniques. In a specimen with
