mechanism of plastic deformation revealing itself in a discrete change of the orientation of a crystal lattice into that of twin in response to a shear stress (see: twinning, mechanical twin), üks plastse deformatsiooni mehhanismidest - kaksikkristallide moodustumine metallide plastsel deformeerimisel; kristall nihkub kaheks sümmeetriliseks osaks kahestumistasandi suhtes (vt kahestumine/kaksikkristallumine, mehaaniliskaksikkristall)