Folding is a common industry practice. In this work we have studied the influence of some parameters such as (the radius of curvature of the matrix, the coefficient of friction between the punch and the specimen, the play between matrix and punch, the thickness of the specimen and the mesh of the specimen) on the deformations of the different zones of the specimen, by a numerical simulation of U-bending using the ABAQUS calculation code.The studied parameters will prove to be of relevant use for the design of the parts from the metal sheets, through the bending forming process. Numerical simulation is a good decision support tool for parts manufacturing companies.For the continuation of this work, a phenomenological model developed by IWAMOTO has been selected and modified to include the evolution of the microstructure (from austenite to martensite) after deformation.