Egon Orowan developed the dislocation account of plastic deformation in crystals. Motion of a dislocation permits successive local rearrangements instead of simultaneous sliding of an entire atomic plane, helping explain why measured strengths can be much lower than ideal-crystal estimates. The National Academy memoir traces his 1934 contribution and later work on deformation and failure.[ref]
https://www.nasonline.org/wp-content/uploads/2024/06/orowan-egon.pdf. biographical memoir, early dislocation work
