Measurement of Diffraction elastic constants after prestrains can be measured from a miniature tensile bar. Below is a miniature tensile bar cut from the top of deformed specimen using Marciniak flat tooling.

Diffraction elastic constants are defined as constants that correlate macroscopic stress and the diffraction strain such that

\[F_{ij}^{\phi,\psi,\{hkl\}} \bar{\sigma}_{ij}=\varepsilon^{\phi,\psi,\{hkl\}}\]

The angular term \(\phi\) and \(\psi\) are defined as planar rotation and tilting angles. Find the illustration in