In 1957, Drucker, Gibson and Henkel were the first to introduce the concept of work-hardening theories of plasticity into the soil mechanics, and using the hardening cap to control dilatancy. This cap model and all of the recent ones are based on Drucker’s stability postulates. Good results have been found using cap models. Most of these versions of cap models have been implemented in many specialized finite element codes, as well as general purpose finite element codes, such as DYNA-3D.  A cap  model is included in DYNA-3D, but there are problems modeling certain materials. The cap model is considered as a complicated material model due to the fact that it consists of three surfaces (the yield surface, the hardening cap, and the tension cutoff), which are intersecting in an nonsmooth fashion. In this paper, a modified cap model based on Hofstetter et al. 1993 implemented in DYNA-3D is presented. The modified cap model incorporates a return mapping algorithm of Simo et al, 1988 and Simo and Taylor, 1985. Koiter’s generalized flow rule,  Koiter, 1960. Kuhn-Tucker optimization conditions are also applied to the modified cap model. The Newton iteration technique for solving the nonlinear equations is used. This makes the convergence quadratic, i.e. faster and less computer time consuming. Finally, evaluation of the model is presented by comparing the results to the original DYNA-3D cap model which was developed by Simo et al., 1988, and to test results.