Design optimization of a novel NPR crash box based on multi-objective genetic algorithm

Zhou G., Ma Z., Cheng A., Li G., Huang J.

Runflat structure plays an important role in determining the sustainable mileage after the tire is shot. Lightweight, stiffness and strength are highly relevant to the overall performance of the structure. A parameterized model was built based on the full study of the structure, and a new adaptive meshing method is proposed to ensure the quality of the model. The accuracy of the new model was verified by comparing to the traditional finite element model. The parameter study was carried out to investigate the response of the performance and mass. Multi-objective optimization model was established by applying optimal Latin square design method and response surface model approach. Non-dominated sorting genetic algorithm-II (NSGA-II) was applied to obtain the optimization design. The results indicate that the combination of parameterized model and multi-objective genetic algorithms successfully achieve the goal of multi-objective optimization for mass and displacement while ensuring the stress. Meanwhile, the optimal topology, shape and thickness optimization for the runflat structure have been achieved at the same time.

Djamaluddin F., Abdullah S., Ariffin A.K., Nopiah Z.M.

This paper presents the multi objective optimization of foam-filled tubular tubes under pure axial and oblique impact loadings. In this work, the double circular tubes, whose bottom is the boundary condition, while at the top, is the impacted rigid wall; with respect to the axis of the tubes. The optimal crash parameter solutions, namely the minimum peak crushing force and the maximum specific energy absorption, are constructed by the Non-dominated Sorting Genetic Algorithm-II and the Radial Basis Function. Different configurations of structures, such as empty empty double tube (EET), foam filled empty double tube (FET), and foam filled foam filled double tube (FFT), are identified for their crashworthiness performance indicators. The results show that the optimal foam filled foam filled tube (FFT) had better crashworthiness than the others under pure axial loading. However, the foam filled empty tube (FET) was the best choice for structures under an oblique loading.

Li Z., Yu J., Guo L.

Research to quantify the energy absorption of empty and foam-filled tubes under oblique loading with different loading angles and geometry parameters was carried out. Tests on circular tubes made of aluminum alloy AA6063 under quasi-static axial or oblique loading were performed. The collapse behavior of empty, foam-filled single and double tubes was investigated at loading angles of 0°, 5°, 10° and 15° with respect to the longitudinal direction of the tube. The tubes were fixed at both ends and oblique load was realized by applying a load at the upper end of a pair of specimens. When the foam-filled tubular structures subjected to oblique quasi-static loading, some new deformation modes, such as spiral folding mode, irregular extensional folding mode and irregular axi-symmetric or diamond deformation mode, were identified and ascribed to the bending of tubes and shearing of foam filler, as well as the interaction between the tubes and the foam. The energy absorption characteristics of empty and foam-filled single and double tube structures with respect to the load angle and wall thickness are determined. It is found that the energy-absorbing effectiveness factors of the circular tube structures with aluminum foam core are significant higher than those of the empty tubes and the energy absorption capacity of the foam-filled double tubes is better than that of the empty and foam-filled single tubes.

Zhao W., Wang C.

In view of the existence of uncertainties such as system model and disturbance signal in the electric power steering (EPS) system, and the demand for system dynamic performance, the mixed H2/H∞ controller based on genetic algorithm is proposed. In order to obtain satisfactory steering feel, robust performance and steering stability, models of EPS system and a two-degree-of-freedom car are set up, then the state space model and the augmented matrixes are built. The H∞ method is introduced to minimize the effect of disturbances on the outputs, and the H2 method is applied to optimizing the system performance based on genetic algorithm. The simulation results show that the modified mixed H2/H∞ controller, which synthesizes the advantage of H2 control and H∞ control, has better robust performance and robust stability. The designed controller can attenuate the noises and disturbances caused by road random motivation, torque sensor measurement and model parameter uncertainty, enabling the driver to obtain satisfactory road feel.

Yoshino T., Xu T., Xu T.S., Cheng P.

The crash box of vehicle plays an important role in absorbing energy during collision. However, the crashworthiness optimization problem is nonlinear which means the relationship between the response and design variables is implicit. This paper constructed a response surface model instead of original model. Meanwhile, uniform design has been taken to select sampling points uniformly. Then PSO method was used to optimize the approximate model with high precision. Finally, the optimization results show that the crashworthiness of structure has enhanced and provide a guide for practical application of crashworthiness design.

Murugan P., Kannan S., Baskar S.

This paper presents an application of Elitist Non-dominated Sorting Genetic Algorithm version II (NSGA-II), to multi-objective generation expansion planning (GEP) problem. The GEP problem is considered as a two-objective problem. The first objective is the minimization of investment cost and the second objective is the minimization of outage cost (or maximization of reliability). To improve the performance of NSGA-II, two modifications are proposed. One modification is incorporation of Virtual Mapping Procedure (VMP), and the other is introduction of controlled elitism in NSGA-II. A synthetic test system having 5 types of candidate units is considered here for GEP for a 6-year planning horizon. The effectiveness of the proposed modifications is illustrated in detail.

Liefvendahl M., Stocki R.

A crucial component in the statistical simulation of a computationally expensive model is a good design of experiments. In this paper we compare the efficiency of the columnwise–pairwise (CP) and genetic algorithms for the optimization of Latin hypercubes (LH) for the purpose of sampling in statistical investigations. The performed experiments indicate, among other results, that CP methods are most efficient for small and medium size LH, while an adopted genetic algorithm performs better for large LH. Two optimality criteria suggested in the literature are evaluated with respect to statistical properties and efficiency. The obtained results lead us to favor a criterion based on the physical analogy of minimization of forces between charged particles suggested in Audze and Eglais (1977. Problems Dyn. Strength 35, 104–107) over a ‘maximin distance’ criterion from Johnson et al. (1990. J. Statist. Plann. Inference 26, 131–148).

Lanzi L., Castelletti L.M., Anghileri M.

Moving from a validated finite element model of composite cylindrical absorbers, this work aims to optimise the shape of conical absorbers with elliptical cross-sections considering simultaneously different impact conditions. Since the use of non-linear finite element analyses to directly evaluate objectives and constraints during the optimisations would be unaffordable from a computational standpoint, a global approximation strategy is used. The crash capabilities of the absorbers are approximated with a system of Radial Basis Functions built by means of a minimum number of finite element analyses. The response surfaces are coupled with Genetic Algorithms to perform both constrained single- and multi-objective optimisations. The results prove that moderate eccentricity and conicity lead to high efficiency structures characterised by stable crush fronts and good absorption capabilities with also associated mass reduction up to the 7% considering vertical impacts and at least of the 20% considering 20° impacts with respect to ideal cylinders.

Hosseinipour S.J., Daneshi G.H.

In the present study, crashworthiness characteristics of thin-walled steel tubes containing annular grooves are studied. For this purpose, the grooves are introduced in the tube to force the plastic deformation to occur at predetermined intervals along the tube. The aims are controlling the buckling mode and predicting energy absorption capacity of the tubes. To do so, circumferential grooves are cut alternately inside and outside of the tubes at predetermined intervals. Quasi-static axial crushing tests are performed and the load-displacement curves are studied. Theoretical formulations are presented for predicting the energy absorption and mean crushing load. It is found a good agreement between the theoretical results and experimental findings. The results indicate that the load-displacement curve and energy absorbed by the axial crushing of tubes could be controlled by the introduction of grooves with different distances. Also, grooves can stabilize the deformation behavior and thus, the proposed method could be a good candidate as a controllable energy absorption element.

Fu Z., Mao H., Yin B.

Zhang L., Yan S., Liu W., Liu Y., Cai W., Zhang Z., Zhou J.

Deng W., Song Z., Lei J., Luo K., Zhang Y., Yu M.

Chikkanna N., Krishnapillai S., Amirthalingam M., Ramachandran V.

Deng Y., Jin Y.

Bagewadi S.S., Bhagchandani R.K., Sinha M.K., Sugavaneswaran M.

Auxetic structures are prominently identified for their outstanding energy absorption capability by the spatial arrangement of the unit cell. In this investigation, the mechanical performance of auxetic structures is improved by distributing the material at the stress concentration regions. Further, two well-known unit cells such as honeycomb and re-entrant honeycomb are combined to understand the effect on mechanical performance. The proposed designs are fabricated by additive manufacturing methods and the samples are subjected to tensile loading. Moreover, a finite element model is created, and the numerical findings are compared with experimental data.

dos Reis M.Q., Carbas R.J., Marques E.A., da Silva L.F.

ABSTRACTAutomotive collisions are one of the major causes of death in the European Union, especially in childhood and adolescence. However, improvements in vehicle safety cannot be achieved only by increasing the size and dimensions of the structures, as this demands more materials and more costly manufacturing processes, which leads to an increased resource expenditure and lowered sustainability. Moreover, the increase of the structure size raises the vehicle's weight, leading to added fuel consumption, which cannot be accepted considering modern environmental regulations. To solve these issues, the application of bonded joints using the combination of several adherends materials, such as steel and aluminium alloys and fibber‐reinforced polymers with crash‐resistant adhesives presents itself as a novel solution, allowing to attain enhanced joint strength, energy absorption and weight reduction. The present works introduce a novel concept of an impact attenuator using bonded, geometrically optimized using the concept of functionally graded adherends to maximize energy absorption by ensuring that a load‐bearing path is kept during impact, converting the impact energy into the plastic deformation of panels with variable mechanical properties, tailored to withstand specific load cases, fulfilling a gap in the literature regarding impact absorption devices that combines graded materials and bonded construction. The results obtained present an increase in the energy absorption values of the graded impact attenuators above 200% when compared to the homogenous materials.

Vitalis T., Gross A., Tzortzinis G., Schagen B., Gerasimidis S.

Bogahawaththa M., Mohotti D., Hazell P.J., Wang H., Wijesooriya K., Lee C.K.

Wang S., Peng F., Liang M.

Shao Q., Ding C., Ji X., Mu J., Wang X., Xue Y.

In this study, a 3D re-entrant anti-trichiral honeycomb (RATH) structure with the combination of various deformation mechanisms was proposed and formed through SLM additive manufacturing. It was found that the samples exhibited a good formability with less internal porosity and fine forming accuracy through the macroscopic and microscopic analyse. The microstructure of the fabricated sample present typical characteristics of the SLM-fabricated materials, which includes coarse grain zone, fine grain zone, and heat affected zone. The grains of the as-fabricated sample mainly exhibit the characteristics of columnar grains and the grains with a length up to 41∼86 μm grow from the boundary of one melt pool to another, which are predominantly oriented in the [001] direction and parallel to the forming direction. The quasi-static compression behavior, auxeticity and energy absorption capabilities of the 3D RATH structures with varied geometric parameters are comprehensively investigated through FEA method verified by the experimental results. The numerical results exhibited a good agreement with the experimental results with regard to stress strain behavior, deformation mode and Poisson's ratio. It was found that the compression performance and auxetic behavior of the 3D RATH structures can be tailored by varying the geometrical parameters. The 3D RATH structures exhibit the simultaneous re-entrant and rotating deformations throughout the whole compression process, thereby producing the auxeticity in large strain range. Moreover, the results exhibit that the proposed 3D RATH structures can significantly enhance the compression stress and auxetic behavior by the combination of different structures compared with conventional re-entrant honeycomb structures.

Rostro-González H., Puigoriol-Forcada J.M., Pérez-Peña A., Menacho J., Garcia-Granada A.

AbstractThe design of a deformation element or crash box that meets a given injury criterion based on deceleration requires careful consideration of physical properties and space requirements. Variations in material yield stress or geometry can result in statistical variations in the injury criterion output. Optimizing the crash box to fulfil two different injury criteria and two different energy levels may require more space than initially specified. In this study, we propose a protocol where the crash box is collapsed, and force–displacement is fitted to an equation. This fit is carried out with just two simulations and compared to 30 possible scenarios, obtaining a maximum error of 38.9%. With this initial fit, the appropriate thickness and yield stress can be chosen to perform crashes with two energy levels and monitor four injury values. With the ideal yield stress and sheet metal thickness, we introduce real statistical distributions using Monte Carlo design to perform 200 simulations and obtain 400 injury values for each design proposal. This technique ensures that the design will meet injury requirements for any possible combination of thickness and yield stress accepted by quality inspection. If only one simulation is performed, all designs meet the requirements, but only the last proposed design decreased the average injury to 9.2 g with a standard deviation of 2.68 g and a maximum value of 14.4 g, which is less than the required 15 g. This technique minimizes the risk of finding combinations of yield stress and thickness that produce an undesirable injury criterion.

Vitalis T., Gross A.J., Gerasimidis S.

Abstract Auxetic architected materials present a novel class of damage-tolerant materials with tunable mechanical characteristics and high energy absorption due to their unique ability to laterally contract and densify when subjected to axial compressive loading. The current state of research on negative Poisson's ratio materials mainly focuses on 2D geometries and a few families of 3D geometries with limited experimental comparisons between different architectures and various geometrical features. Furthermore, when manufactured via laser powder bed fusion, the influence of as-built deviations of geometrical and material properties inherently present due to the melt pool solidification process for thin features is relatively unexplored in the case of metal architected materials. The authors aim to study the elastic properties, peak characteristics, and failure modes of steel auxetic truss lattices subjected to axial compression while also addressing the uncertainties inherent to the metal laser powder bed fusion additive manufacturing of architected materials. This work presents an experimental and computational exploration and comparison of two promising three-dimensional auxetic truss lattice families of low relative densities. A comprehensive investigation of metal negative Poisson's ratio mechanical metamaterials is presented, including the selection of the architectures, modeling, laser powder bed fusion additive manufacturing, as-built part characterization, material testing, and mechanical testing under axial compression. The study of such architectures can unlock their potential in making them readily adaptable to a wide variety of engineering applications.

Zhang L., Yang D., Li Q., Qiu J.

The conventional impact process is a quintessential impulse process that causes substantial damage due to the high initial impact force. However, the impact effect can be significantly diminished by making the impulse process quasi-statically by using a three-dimensional negative Poisson's ratio corrugated metamaterial (3D-NPRCM) structure. This paper proposes a novel 3D-NPRCM obtained by folding the 2D-NPRCM. This study examines the crashworthiness properties and impact force of 3D-NPRCM subjected to impact using the finite element method (FEM). The results reveal that the sequential matrix structure has the ability to make impact impulse processes quasi-statically. The effects of various folding angles, arrangements, and geometrical parameters on the properties are also explored. Finally, the 3D-NPRCM is employed in an automobile crash box design. Through axial quasi-static compression simulation, the peak crushing force of the 3D-NPRCM crash box is reduced by 25.374% from 211.652 kN to 157.946 kN, and the energy absorbed is increased by 23.830% from 11.259kJ to 13.942kJ, compared to the conventional crash box. Through cart lateral impact simulation, the peak crushing force of the 3D-NPRCM crash box is reduced by 18.076% from 206.9 kN to 169.5 kN, and the compressive displacement is decreased by 9.457% from 235.8 mm to 213.5 mm. This work presents a novel design proposition for a crash box in vehicle engineering and demonstrates a fresh approach to expand the design of three-dimensional mechanical metamaterials.

Zhang C., Lu F., Wei T., Ling X., Lin B., Zhu Y.

In the contemporary landscape of engineering, escalating demands for advanced material and structural performance have brought metamaterials to the forefront. Among them, the enhanced anti-tetra-missing rib structure has gained prominence owing to its auxetic behavior under significant strain. However, the lack of research on its quasi-static and dynamic mechanical performance have hindered its practical application. To address this, we introduce the tubular enhanced anti-tetra-missing rib structure (TEATMRS) and derive its collapse stress expression under various conditions. Through extensive simulations and experiments, we explore its deformation mechanisms and assess the influence of the structural geometric parameters and impact velocity on collapse stress. The results demonstrate excellent agreement among theoretical description, numerical analysis, and experimental tests, establishing the feasibility of the proposed collapse stress expression. These findings provide a theoretical foundation and design guidance for TEATMRS in engineering applications.