The Burgers Vector

When a material is stretched beyond its elastic limit, the atoms and molecules begin to slide over each other. This is called plasticity, and is dominated by the motion of defects in the crystal structure of the material, notably line defects called dislocations. The structure and magnitude of a dislocation is defined by its Burgers vector, which is a topological constant for a given dislocation line in a given material, so there is an effective Burgers equation: b = constant. This chapter describes: the structure of edge; screw and mixed dislocations and their associated line energy; the way in which dislocations are generated and interact under stress, leading to the yield point, work hardening and a permanent set in the material; and the use during manufacturing of deformation processing, annealing, recovery and recrystallisation. Jan Burgers’ early life in Arnhem at the beginning of the 20th century is described, as are: his time as a student with the charismatic but depressive Paul Ehrenfest, who later committed suicide; his appointment as the first Professor of Aerodynamics at Technische Universiteit Delft at a time of massive growth in the aviation industry; his contributions to aerodynamic and hydrodynamic flow as well as major Dutch engineering projects such as the Zuiderzee dams and the Maas river tunnel; his growing disaffection with the commercialisation of science and its use in warfare; and his philosophical dalliance with Soviet communism and then American capitalism.