Numerical simulation of the roller hemming process based on pressure-viscosity effect

In the roller hemming process, the high-viscosity adhesive has affected the forming process of metal sheets, especially lightweight materials. However, the effect and mechanism are not clear. In this paper, the hemming adhesive is taken as a viscous Newtonian fluid. First of all, the pressure-viscosity effect in the model of parallel-panel squeeze is investigated, while the adhesive flow is simulated by smooth particle hydrodynamics (SPH) method, and the results are compared and verified by analytical solutions. Then, the roller hemming process of aluminum alloy sheet AA6106-T4 with adhesive is simulated by using the fluid-solid coupling method, while the adhesive is modeled by SPH and the aluminum alloy sheet is modeled by finite element method (FEM). The accuracy of the simulation model is verified by a comparison of roll-in/out in experiment and the effect and mechanism is studied based on the pressure-viscosity effect. The results show that adhesive thickness is the most important factor of the pressure-viscosity effect. The roll-in value of aluminum alloy sheet sample with 0.2-mm thick adhesive is relatively less than that without under the same conditions, and the roll-in of aluminum alloy sheet raises with an increase of the adhesive layer thickness. The evaluated roll-in/out of samples with different thickness of adhesive can obtain zero value theoretically after final hemming.