Electronic Journal of Differential Equations, Vol. 2011 (2011), No. 27, pp. 1-19. Title: Existence and stability of solutions for nonlinear Mecking-Lucke-Grilhe equations Authors: Ali Alriyabi (Univ. de Poitiers, Cedex, France) Said Hilout (Univ. de Poitiers, Cedex, France) Abstract: In this article, we present the nonlinear Mecking-Lucke-Grilhe model describing the temporal evolution for simple and multi-instabilities of plastic deformation of stressed monocristal. This model extends the linear problem considered in [9, 13, 14]. Using a nonlinear analysis, we present some results of existence and stability of the solution with respect to the characteristics of the material and the retarded times. Numerical examples validating the theoretical results are also investigated in this study. Submitted July 18, 2010 Published February 15, 2011. Math Subject Classifications: 34A34, 34D05, 34D20, 34A45. Key Words: Mecking-Lucke-Grilhe equation; plastic deformation; delay differential equations; characteristic equation; dislocation; asymptotic stability.