This diagram represents a face-centered cubic crystal with a rectangular cross-section. The crystal has twinned on three planes and the twin traces have been measured with respect to a vertical edge, or the stress axis of the crystal. The angles thus obtained are shown in the figure. Orient this crystal by the two-surface technique following the steps listed below.
(a) Lay out a stereographic projection on a sheet of tracing paper with the front face of the crystal as the basic cirde and the top of this circle the stress axis.
(b) Around the basic circle, plot the twin trace orientations corresponding to the front face.
(c) Draw in the great circle corresponding to the side of the crystal and plot on the circle the corresponding twin trace orientations.
(d) Draw in the three great circles representing the three twinning planes. Plot the poles of these three planes.
(e) From the geometry of the fcc crystal structure, determine the orientation of a cube pole; that is, \{100). Plot this on the figure.
(f) Rotate the stereographic projection thus obtained into a standard (100) projection, making sure that the stress axis is also rotated. In order to simplify the result, this last step is best performed on a second sheet of tracing paper.
(g) Draw in the boundaries of the standard stereographic triangle that surrounds the stress axis, thus defining the stress axis orientation.