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In this study, the design and optimization of a honeycomb energy absorber is performed using genetic algorithm. The main design goal is to absorb almost whole impact energy. Simultaneously, the reducing of the shock force level is also considered as a main objective. In the first part, the crashworthiness behavior of honeycomb structure is parametrically studied. The results are utilized in the second part to optimize shock absorber design. In this part, aluminum honeycomb structure under dynamic loading is investigated using simulation in LS-dyna finite element code. Parametric studies are invoked to identify the influence of different model parameters on crashworthiness characteristics of honeycomb structure. Reducing the computational cost, a repeatable model of 'Y' cross section column is numerically simulated. The effects of changes in material properties including Young's modulus, yield stress, tangent modulus, geometrical properties such as cell size, foil thickness, as well as the effects of impact velocity on the deformation behavior of the structure were investigated. A number of 25 different geometries with same height and various cell sizes and thicknesses are studied and effects of thickness and cell size on the energy absorption properties is investigated. Results showed that crashworthiness parameters such as mean and peak stress depend mainly on cell size and thickness values, while the friction coefficient and young's modulus are of less importance. Any change in absorber’s geometry affects the mean collapse stress more severe than the peak stress. In the meantime, thickness change is more effective in comparison with cell size change.

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In this study, honeycomb energy absorber is optimized using genetic algorithm. The design goal is to absorb whole impact energy within a ‎limited shock load level. First the crashworthiness and parameter sensitivity of honeycomb structure is extracted as explicit functions that ‎are utilized to find optimized shock absorber configuration. Energy absorber must depreciate the impact kinetic energy and mitigate its ‎defects on the structure and aboard. So the energy absorption capacity while the shock load is kept limited are the main design objectives. ‎The volume and mass restrictions are also important objectives from an application point of view. Based on the simulation results ‎available in the article Part I, the honeycomb response surfaces of crashworthiness parameters including the mean and peak crushing ‎stresses are extracted. Utilizing the genetic algorithm based on response functions, the multi-objective optimized energy absorber is ‎investigated. The main objective of the optimization problem is set to minimization of mass or volume while the maximum allowable shock ‎and minimum energy absorption capacity are included as the problem constraints. The geometric specifications of honeycomb structure ‎including cell-size, foil thickness, height and absorber face area are among the design variables with optimization outputs of energy ‎absorption capacity, volume, mass, and shock level. Some optimization results are compared with those available in the literature and a ‎typical problem is handled. Results show that mass and volume optimized geometries are almost similar and reduction of acceptable shock ‎level makes the optimized geometry height to rise.‎

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