Guilin Wen

CRASHWORTHINESS DESIGN FOR HONEYCOMB STRUCTURES UNDER AXIAL DYNAMIC LOADING

For a honeycomb structure used for absorbing crash energy and protecting the safety of human or instruments, the bigger the specific energy absorption (SEA) is, the more popular it would be when the peak crushing stress (σp) was retained small enough. In order to improve the energy absorption capacity, crashworthiness optimization for honeycomb structures with various cell specifications are studied in this paper. Detailed numerical models are established for those honeycomb structures by using an explicit finite element method code LS-DYNA. The numerical simulation results are then used as the design samples for constructing metamodels. The optimal Latin hypercube design (OLHD) method is employed for the selection of sampling design points in the design space, and the polynomial functions, radial basis functions (RBF), Kriging, multivariate adaptive regression splines (MARS), and support vector regression (SVR) are utilized to formulate the two optimal objectives SEA and σp. It is found that the polynomial function is the most efficient in constructing the crashworthiness metamodels of honeycombs among the above-mentioned methods. Then, the polynomial function models of SEA and σp are chosen as the surrogate models in the crashworthiness optimization. In order to further validate the polynomial function models, the polynomial function models of SEA and σp are compared with the analytical solutions based on Wierzbickis theory and Kunimoto and Yamadas theory, respectively. An excellent correlation has been established. As such, the multi-objective particle swarm optimization algorithm (MOPSOA) is applied to obtain the Pareto front of SEA with σp of the honeycomb structures with various cell specifications, which has resulted in a range of optimal designs of honeycomb structures by the multi-objective optimization.

An efficient method for topology optimization of continuum structures in the presence of uncertainty in loading direction

This paper presents a simple yet efficient method for the topology optimization of continuum structures considering interval uncertainties in loading directions. Interval mathematics is employed to equivalently transform the uncertain topology optimization problem into a deterministic one with multiple load cases. An efficient soft-kill bi-directional evolutionary structural optimization (BESO) method is proposed to solve the problem, which only requires two finite element analyses per iteration for each external load with directional uncertainty regardless of the number of the multiple load cases. The presented algorithm leads to significant computational savings when compared with Monte Carlo-based optimization (MCBO) algorithms. A series of numerical examples including symmetric and nonsymmetric loading variations demonstrate the considerable improvement of computational efficiency of the proposed approach as well as the significance of including uncertainties in topology optimization when to design a structure. Optimums obtained from the proposed algorithm are verified by MCBO method.

Design optimization of a new W-beam guardrail for enhanced highway safety performance

Abstract As one of the most widely used safety devices on highways, W-beam guardrail plays an important role in protecting errant vehicles from entering dangerous zones or colliding with oncoming vehicles. As one of the most widely used safety devices on highways, W-beam guardrails play an important role in protecting errant vehicles from entering dangerous zones or colliding with oncoming vehicles. One common issue with the traditional W-beam guardrails (TWG) is tire snagging which often occurred when the wheel of a striking vehicle entangled with a guardrail post. Tire snagging reduces the redirection performance of the guardrail and can result in serious injuries to the occupants. In this study, a new W-beam guardrail, named as “η-shaped W-beam guardrail (η-WG)”, was developed using nonlinear finite element simulations combined with metamodeling-based design optimization methodology. The simulation results showed that tire snagging did not occur on the η-WG and the optimum design of the η-WG had an improved safety performance in vehicular crashes.

A Novel Design Framework for Structures/Materials with Enhanced Mechanical Performance

Structure/material requires simultaneous consideration of both its design and manufacturing processes to dramatically enhance its manufacturability, assembly and maintainability. In this work, a novel design framework for structural/material with a desired mechanical performance and compelling topological design properties achieved using origami techniques is presented. The framework comprises four procedures, including topological design, unfold, reduction manufacturing, and fold. The topological design method, i.e., the solid isotropic material penalization (SIMP) method, serves to optimize the structure in order to achieve the preferred mechanical characteristics, and the origami technique is exploited to allow the structure to be rapidly and easily fabricated. Topological design and unfold procedures can be conveniently completed in a computer; then, reduction manufacturing, i.e., cutting, is performed to remove materials from the unfolded flat plate; the final structure is obtained by folding out the plate from the previous procedure. A series of cantilevers, consisting of origami parallel creases and Miura-ori (usually regarded as a metamaterial) and made of paperboard, are designed with the least weight and the required stiffness by using the proposed framework. The findings here furnish an alternative design framework for engineering structures that could be better than the 3D-printing technique, especially for large structures made of thin metal materials.

Optimisation for bending crashworthiness of functionally graded foam-filled cellular structure

ABSTRACT Due to extraordinary energy absorption capacity as well as light weight, functionally graded foam-filled cellular structure (FGFCS) has gained considerable attention. Using nonlinear finite element method through LS-DYNA, this work studied the bending crashworthiness of nine FGFCSs with different cross-sectional configurations. The results demonstrate that the bending crashworthiness of the FGFCSs is significantly affected by the design parameter of the graded functional parameter q. Thus, in order to find the optimal gradient exponential parameter, the FGFCSs with different cross sections were optimised using the radial basis function metamodel and the Non-dominated Sorting Genetic Algorithm II. Meanwhile, the corresponding uniform foam-filled cellular structures (UFCSs) with the same weight as above FGFCSs were also optimised in our study. In the optimisation process, the aim is to achieve maximum value of specific energy absorption and minimum value of peak crushing force. By comparing the Pareto fronts obtained by multi-objective optimisation, it can be found that FGFCSs have better crashworthiness than the corresponding UFCSs in most considered cases. Thus, the optimal design of FGFCS has exactly an excellent energy absorption capacity under lateral impact and can be used in the future vehicle body.