Kinematics of Crossing Twins

Twins are commonly observed in crystalline solids that undergo martensitic phase transformation. In many materials the twins are also seen to cross each other. This is surprising in view of the severe kinematic restrictions that such crossings impose. This paper presents a sufficient condition for satisfying these restrictions. It turns out that this condition is automatically satisfied as a consequence of material symmetry in many common martensitic materials. This explains the common observation of crossing twins. The result is also applied to the magnetostrictive material Terfenol.