Analysis on influence of grid density on element failure strain in penetration numerical simulation

  Objectives  In order to solve the problem of numerical simulation of flat-nosed projectile penetration into metal plates, the influence of mesh size on element failure strain value and residual velocity of projectiles was studied.

  Methods  The finite element software LS-DYNA was used to simulate the process of uniaxial tensile test of Q235 steel sample, and the failure strain of the element under the grid density is obtained by the elongation of the tensile sample during fracture. In the meantime, the correction curve of the failure strain with the grid density was plotted and dynamically corrected. Then, the numerical simulation of flat-nosed projectile penetrating Q235 steel plate was carried out with the target plate meshed with different sizes. The failure strain of Q235 steel material was selected according to the correction curve. Finally, the residual velocity of the projectile is compared with the experimental results to analyze the influence of mesh size on the simulation results of the penetration resistance problem of the metal plate in the numerical simulation.

  Results  The results show that the element failure strain selected in the numerical simulation should increase with the increase in grid density, and in the case of the metal plate anti-penetration problem, it should increase with the increase of the grid density. In the problem of penetration resistance of metal plates, the simulation results of residual velocity prediction gradually converge with the experimental results. With the increase of mesh density, when the grid size is 0.5 mm, the average relative error of the numerical simulation and the test fitting curve in the velocity section is 5.13%, and the error between the numerical simulation and the test is larger in the low-speed section. Moreover, the residual velocity of the projectile body is more sensitive to mesh density in the low velocity range.

  Conclusions  The related calculation methods and research results have a certain reference value for the selection of mesh size and material failure strain in the projectile penetration problem.