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the lattice constants which finally left compression or
tension in the unit cell and finally residual stress build
up. This is common in ceramic or ceramic-composite
materials, where heat treatment is one process during
the fabrication of the components.

Residual stress also build-up on in service engi-
neering component, such as in the steel of the rail
track. Under repeating loading of the train travel and
pressing the rail track will change the geometry of unit
cell of each element forms the rail track component.
Large deformation of rail track component can be seen
macroscopically, while changes also happened at mi-
croscopic level where deform unit cell geometry. Se-
quentially, this process allow the stress to build up and
remained internally and can cause the initiation of micro-
cracks. The internal stress is know residual stress re-
sulting from repeating load of trains weight.

Both approach of loading condition can cause the
stress in the material and it is developed and remained
inside the materials. This internal stress will weaken
the engineering component. Therefore, actual load
apply on the engineering component should put in con-
sideration of residual stress. In this case, residual stress
of engineering component need to be determined. So
that, the life of the component itself and be longer with-
out problems.

The measurement of residual stress required at least
four measurement. First experiment is the measure-

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