[en] Based on recent dislocation dynamics simulations investigations, a set of constitutive equations and model parameters for the description of plasticity of body-centered cubic materials is proposed. Assuming the flow stress to be controlled at low temperatures by the mobility of screw dislocations and by forest interactions at high temperatures, this model allows for the prediction of the mechanical behavior in monotonic loading over a large range of temperatures and strain rates. The consideration of the difference in mobility between screw and non-screw dislocations is found to affect strain hardening in a complex manner. The constitutive equations are implemented in a finite-element method to simulate tensile tests on iron single crystal at different temperatures. The use of finite transformation formalism enables the computation of crystal rotations which affect slip system activities. The calculated critical resolved shear stress and crystal rotations are in good agreement with existing experimental results. (authors)