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0.5432 (4.11)
d[111] = 12 + 12 + 12 = 0.3135nm

This equation provides lattice spacing value,d[111] =
0.3135nm, The diffraction pattern from Si crystalline

material at neutron wavelength 0.0251 nm has peak-

ing at diffraction angle, 2θ[111], given in Equation 4.12.

0.0251nm (4.12)
2θ[111] = 0.3135nm = 80.0mrad

4.4.2 Measurement of Residual Stress

Neutron diffraction is one of the widely used technique
for measuring a residual stress remain in the materials
of an engineering component. Fabrication process in
making an engineering component plays crucial role
determined the amount of stresses remained in the
materials. Heating and cooling for example will induce
stress in the materials. Heating will expand the lattice
size while cooling will reduce the unit cell.

The changes in lattice constant will change the lat-
tice spacing as well. Each element forms the material
has distinctive thermal expansion where can affects
the way of unit cell expand or shrink under thermal
stresses. Miss match in a thermal expansion coeffi-
cient of materials causes different response by a unit
cell of different element. This will results in changes in

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