Biot-Savart law in the geometrical theory of dislocations.

Abstract

Universal mechanical principles may exist behind seemingly unrelated physical phenomena, providing novel insights into their underlying mechanisms. This study sheds light on the geometrical theory of dislocations through an analogy with electromagnetics. In this theory, solving Cartan's first structure equation is essential for connecting the dislocation density to the plastic deformation field of the dislocations. The additional constraint of a divergence-free condition, derived from the Helmholtz decomposition, forms the governing equations that mirror Ampère's and Gauss's law in electromagnetics. This allows for the analytical integration of the equations using the Biot-Savart law. The plastic deformation fields of screw and edge dislocations obtained through this process form both a vortex and an orthogonal coordinate system on the cross-section perpendicular to the dislocation line. This orthogonality is rooted in the conformal property of the corresponding complex function that satisfies the Cauchy-Riemann equations, leading to the complex potential of plastic deformation. We validate the results by comparing them with the classical dislocation theory. The incompatibility tensor is crucial in the generation of the mechanical field. These findings reveal a profound unification of dislocation theories, electromagnetics and complex functions through their underlying mathematical parallels.