Hasan Kurtaran

Ballistic impact simulation of GT model vehicle door using finite element method

Abstract Penetration performance of GT model military vehicle door subjected to the ballistic impact of a bullet with semispherical nose shape is investigated using 3-D nonlinear dynamic explicit finite element code LS-DYNA. Finite element simulations of the door for the bullet impact velocities of 500, 1000 and 1500 m/s are carried out using plastic kinematic and Johnson–Cook material models that can characterize strain and strain rate hardening, thermal softening effects and fracture at high velocity impacts. To reduce the computational cost of the bullet-door impact analysis, only a part of the door subjected to the impact of the bullet is considered. The part of the door is idealized as a single layer circular thin plate. Finite element analysis of the single layer plate of 2 mm thickness showed full penetration of the bullet. Analysis of the plate with existing layer backed by another layer of higher thickness prevented complete penetration. Simulations with both material models also indicated a noticeable difference in the deformation of the plate and particularly the bullet upon impact indicating the thermal softening effect.

Design optimization of multi-body systems under impact loading by response surface methodology

Abstract Design optimization of multi-body systems is challenged by the highly non-linear and computationally expensive (for large-scale systems) nature of many multi-body responses. In this paper, a sequential approximate optimization method is presented in order to achieve accurate and efficient design optimization of multi-body systems under impact loads. The sequential approximate optimization method is obtained by coupling a conventional optimization algorithm with a statistical model building technique, response surface methodology (RSM). In this method, a multi-body optimization problem is approximated as a series of simpler subproblems, using RSM and a genetic algorithm, before it is solved by a numerical optimization algorithm. The approximate optimization method is applied to several multi-body impact problems. These include a linear impact absorber and lumped-mass systems representing simplified vehicle-barrier and vehicle-vehicle frontal impacts. The effect of the choice of various approximation methods is also addressed. The results demonstrate that the use of RSM coupled with conventional optimization methods leads to efficient and effective design tools for multi-body systems under impacts.

Approximate Optimization Method as an Efficient Design Methodology for Armors under Ballistic Impacts

Design optimization of armors under impacts generally follows many computationally costly analyses with predefined design parameters until design objectives and constraints are satisfied. In this paper, an approximate optimization method is proposed as an efficient and effective design optimization methodology for armors. The proposed approximate optimization method, which is implemented in ANSYS Design Optimization Module, is based on coupling of ANSYS parametric preprocessor, 3-D explicit finite element code ANSYS/LS-DYNA and a numerical optimization algorithm over response surface approximations. The power of the approximate optimization method is demonstrated on a laminated armor design problem. A three-layer laminated armor under the high-velocity impact of a projectile is designed to satisfy the minimum penetration of the projectile using the approximate optimization method. The method is systematically able to yield the optimum design with only limited number of finite element analyses.