Multi-cell Structure Research Articles

Dynamic response and failure characteristics of the fluid-filled concave multicell structure under combined blast and fragments loading

The deformation and damage characteristics of the fluid-filled concave multicell structure under the charge explosion with preset fragments are investigated to assess its performance against combined blast and fragments loading. The failure characteristics of the structure, the propagation process of loads, and the dynamic response characteristics of the structure are analyzed using experimental research and SPH-ALE numerical simulation. The results indicate that the deformation of the structure, caused by the explosion of a charge with preset fragments, is 400% greater than the deformation caused by the explosion alone. The propagation of the load is influenced by the panels of the structure and the irregular regions where fluid is filled. The deformation and failure of the fluid-filled concave multicell structure occur in two stages. The failure mode of this structure can be seen as a combination of the failure modes of individual single-cell structures, based on the method of fluid filling. The strength distribution of the structure plays a crucial role in determining the failure of the fluid-filled concave multicell structure.

Design of hierarchical multi-cell double circular tubes thin-walled structures for energy absorption

This study aims to investigate the crashworthiness performance of a novel hierarchical multi-cell double circular tubes (HMDC) structure under axial impact. Various dual-tube structures of different cross-sections were designed. The effects of hierarchical order, peak number of the core column, and inner circle diameter on the structure were analyzed using Abaqus finite element analysis. The results indicate that in dual-tube structures, replacing the traditional multi-cell structure with a hierarchical multi-cell structure in the interlayer significantly improves energy absorption (EA) characteristics. With the inner circle diameter of the HMDC fixed at 20 mm, the ratio of mean crushing force (MCF) to peak crushing force at the third order increased by 70.70% and 35.68% compared to the first and second orders, respectively. Experimental results and finite element results show that the initial peak value differed by 1.47%, indicating a close match between the experimental and simulation results. The parametric study shows that the inner circle diameter and the peak number of the core column significantly affect EA. The findings of this study provide effective guidance for designing multi-cell dual circular tubes with high EA efficiency.

Efficient energy absorption of bio-inspired bi-directional gradient hierarchical multi-cell structure

This research proposes a novel bio-inspired bi-directional gradient hierarchical multi-cell (BGHM) structure for efficient energy absorption. Its dynamic crushing performance and energy absorption behaviours are comprehensively investigated through numerical simulations and theoretical analysis. Extensive numerical simulations are conducted on the proposed BGHM structure with varying hierarchical orders and masses. The obtained results demonstrate that the specific energy absorption of the third-order BGHM tube is significantly improved, exhibiting a 110% increase compared to the zero-order BGHM tube. Additionally, the undulation of the loading resistance of the third-order BGHM tube decreased by up to 93.0% when compared to a conventional square tube, highlighting the tremendous potential of BGHM tubes for the development of highly effective energy absorbers. In addition, a new trigger mechanism using the pre-crushing method can eliminate the initial peak crushing force of the BGHM, demonstrating the promising potential of triggers in optimizing the crashworthiness of energy absorbers. Furthermore, a comparative analysis reveals that the specific energy absorption of the BGHM outperforms other existing hierarchical multi-cell square tubes in literature. This underscores the superior energy absorption capabilities of the proposed BGHM. To complement the numerical findings, a theoretical study on the proposed BGHM's mean crushing force is carried out. The results from this theoretical study show excellent agreement with the numerical results and further validate the efficacy of the proposed design. The findings indicate that the bio-inspired bi-directional gradient hierarchy incorporated in the BGHM structure offers promising prospects for advancements in energy absorption technology across various industries.

Experimental and numerical investigation of crashworthiness of multicell metal/CFRP tubes

Metal/CFRP hybrid thin-walled structures combine low-density and high-strength carbon fibre reinforced plastics (CFRP) with low-cost and stable failure form aluminium, which have drawn increasing attention in the transportation industry. A theoretical model was developed to predict the average crushing force of a hybrid multicell under axial compression. The model captures the main energy dissipation mechanism of the hybrid tube under axial compression, and the average crushing force is determined by a quasi-static compression test. The obtained results show that the average crushing force predicted by the theoretical model is in good agreement with the experimental results. However, the geometry size and configuration of multicell thin-walled structures have important effects on crashworthiness. Therefore, it is necessary to study the parametrization of hybrid multicell tubes. First, the simulation model of the multicell tube is established, and quasi-static experiments verify its accuracy. Second, finite element analysis was used to compare the effects of the geometric size of the cell and the multicell structure of different configurations on the energy absorption characteristics. It is clear that with the increase in the thickness of the large aluminium tube, the specific energy absorption (SEA) and crush force efficiency (CFE) both show an upward trend. In addition, with the increase in the ply number of the CFRP tubes, the SEA also shows a minor monotonic increasing trend. Finally, various hybrid tubes with different configurations are designed, and the C-C4-AL tube (the aluminium tube surrounded by four small-size CFRP tubes being placed inside a CFRP tube.) configuration has the most significant energy absorption (EA) and peak crushing force (PCF).

Crashworthiness behavior of multi-cell structures reinforced with small tubes under axial and inclined loading

In this paper, a novel design for the cross-sectional shapes of square, hexagonal, octagonal, and decagonal structures has been proposed for the development of energy-absorbing devices. The deformation behavior of these structures, which contain multiple small tubes, was analyzed under axial and inclined loads (0°, 10°, 20°, and 30°) using a validated finite element model in LS-DYNA, supported by experimental and analytical data. Various crushing metrics such as specific energy absorption (SEA), peak crushing force (PCF), mean crushing force (MCF), crush force efficiency (CFE), and undulation of load-carrying capacity (ULC) were evaluated for the structures. The results indicated an optimal size for the small tubes that maximizes energy absorption capability. Through the TOPSIS method considering 12 criteria, the multi-cell octagonal structure O5, which includes the highest number of small tubes, was identified as the most effective energy absorber. It demonstrated significantly higher Specific Energy Absorption (SEA) values compared to simpler structures S1, H1, O1, and D1, with improvements of 89%, 65%, 53%, and 46%, respectively. Therefore, it could be utilized in automotive structures for crashworthiness applications.

SiC Super-Junction MOSFET robustness assessment and method to improve avalanche capability

In this paper, the reliability of super-junction MOSFET under single-pulse Unclamped Inductive Switching (UIS) was simulated using Sentaurus TCAD software. Through simulation of etching source metal, it was proved that the conduction of parasitic bipolar transistor in parallel multi-cell structure is the main cause of temperature concentration leading to burnout. The method of reinforcing super-junction MOSFET is proposed by using the conduction of parasitic transistors as the criterion for evaluating UIS performance. In the proposed two-layer alternating PN column stack structure, the upper PN columns have a charge imbalance structure with a higher p-column concentration than the n-column. The simulation results show that the improved structure has higher avalanche energy and wider process variation range compared to the traditional structure. Compared with the traditional device, the improved device achieves a continuous avalanche duration of 1.3 × 10−3 s and an avalanche robustness of 8.24 joules (J) when the parasitic bipolar transistor is non-conductive, significantly reducing the process difficulty by increasing the P-base concentration deviation to 5.8 × 1017 cm−3 under the same avalanche duration range.

Energy absorption characteristics of novel bionic H-type whip restraints for nuclear power plants

To enhance the efficiency of energy absorption in H-type whip restraints for nuclear power plants, this study takes inspiration from the asymmetric twisted lines observed in the Nautilus shell, introducing the Nautilus Bionic Hierarchical Multi-Cell (NBHMC) structure. For different high-energy pipeline sizes and energy absorption quantities, the proposed structures are miniaturized and can be combined into H-type whip restraint by multiple tubes to meet the requirements. The NBHMC structures are investigated based on the validated finite element method, the results demonstrate that the energy absorption per unit mass of the new structure can reach up to 180% of that of the hollow tube, with the maximum enhancement in energy absorption efficiency being 47%. Through parameter analysis of the cross-sectional wall thickness, the highest energy absorption efficiency obtained is 99.62%, with a specific energy absorption of 31.29J/g. Furthermore, utilizing the TOPSIS method, all proposed parameter combinations are ranked, leading to the determination of the optimal parameter combination. Additionally, a theoretical model predicting the mean crushing force is introduced, exhibiting good agreement with numerical simulations. The results presented in this work provide innovative insights for the design of efficient pipe whip restraints.

Theoretical analysis and crashworthiness optimization of multi-cell Al-CFRP hybrid tube

In this paper, a hybrid thin-walled tube with multiple cells and multiple materials is proposed to achieve lightweight, high energy absorption efficiency, and low cost of structures. Energy absorption characteristics and crushing deformation of the hybrid structures are investigated by experimental testing and numerical analysis. Meanwhile, theoretical prediction models of the mean crushing force for hybrid structures are developed and its accuracy was verified. It is found from the sensitivity analysis that the parameters of the multi-cell structure have significant effects on energy absorption. Furthermore, the multi-objective optimization including surrogate models is performed to obtain optimal crashworthiness of the multi-cell hybrid tube. The same optimal results were obtained using the full factor response mapping optimization algorithm and the non-dominated sorting genetic algorithm with elite strategy algorithm for multi-objective optimization solution. Compared with the original multi-cell hybrid tube and multi-cell pure aluminum (Al) tube, the optimized structure showed an increase of 0.25% and 25.31% in specific energy absorption, an increase of 16% and 77.34% in average crushing force, and an increase of 3.89% and 23.08% in energy absorption efficiency, respectively.

Bayesian optimization of origami multi-cell tubes for energy absorption considering mixed categorical-continuous variables

Multi-cell structures have been widely utilized in energy-absorbing applications for their lightweight and superior mechanical properties. However, they may produce high peak forces that are harmful to occupant safety during a vehicle collision. In addition, the naturally formed folding and global bending modes under axial loads can significantly restrict their energy-absorbing capability. In this study, a novel origami multi-cell structure is proposed to avoid excessive peak loads and at the same time to guide the deformation mode to improve the energy-absorbing capability. Four cross-sectional types of origami multi-cell structures are investigated experimentally and numerically. The results indicated that the web-to-web (W2W) type origami multi-cell structures are most promising for energy absorption, while web-to-corner (W2C) structures yield low peak forces and excellent deformation modes in our study cases. To further exploit the potential of these structures, multi-objective optimization is required to consider the conflicting objectives of maximizing energy-absorbing capability and minimizing the peak force. However, it is challenging for traditional optimization to deal with continuous, integer, and categorical variables simultaneously. Therefore, the Bayesian optimization method based on the Hamming distance is utilized to handle mixed categorical-continuous variables to optimize origami multi-cell tubes. The optimization results indicated that the optimal origami W2C can decrease the peak force by 30 % while keeping a similar level of specific energy-absorbing capability compared with the conventional W2C structure. Moreover, the optimal origami W2C structure can improve the energy absorption by 40 % compared with the origami W2C baseline design.

Node-locked multi-cell honeycomb for efficient energy absorption

Material reconfiguration at node positions is currently a prominent method for enhancing the energy absorption capability of honeycomb structures. However, the complexity of cellar configuration poses challenges in the manufacture with cost-efficiency due to intricate preparation processes, which limits its widespread application. In this work, an innovative approach was proposed to fabricate the multi-cell honeycomb structure by nesting and assembling node-locked components with a specific shape. The stable energy absorption of multi-cell structure with node-locked design strategy was preliminarily validated by the numerical and experimental results. Additionally, the effect of the bent panels number and the cell size ratio were investigated numerically and theoretically to reveal the energy absorption mechanism of node-locked multi-cell honeycomb (NMH). It is demonstrated that the strategy by assembling node-locked components can significantly simplify preparation processes of multi-cell structure while maintaining excellent energy absorption capabilities, this offers a better balance between the cost-efficiency and superb energy absorption for multi-cell structures.

Modular assembly for multicell structures with designable energy absorption characteristics

In this study, a novel modular multicell structure was proposed to achieve tunable energy absorption characteristics. Dovetail grooves and protrusions were designed on square thin-walled tubes as interfaces to realize the modular assembly. The quasi-static compression experimental results showed that single thin-walled tubes made of thermoplastic polyurethanes and short carbon-fiber-reinforced polyamide exhibited high elasticity and high compressive strength, respectively. Due to the different mechanical properties of the two materials, energy absorption performance of modular structures reached different levels with the variation of cell materials. The concept of modular multicell structure provided possibility to customize energy absorbers with desired properties.

Crashworthiness analysis and optimization of a novel thin-walled multi-cell structure inspired by bamboo

The sophistication and regularity of natural materials continuously provide inspiration for mankind. Mimicking biological materials to devise advanced energy absorption structures remains grand challenges. Herein, we demonstrate a new type of thin-walled multi-cell structure, based on the shape and distribution characteristics of bamboo cross-sections. Numerical simulations of the proposed structure under quasi-static axial compression, lateral compression, and three-point bending are conducted through the finite element method. The crashworthiness of the new structure is compared with that of two other classic bamboo-inspired structures and an ordinary circular tube, and the results show that the present has superior specific energy absorption (SEA), compression efficiency, and deformation mode. Besides, our study also investigates the effects of the wall thickness of bamboo-inspired cell elements and the bio-inspired inner shell on the axial crashworthiness of the proposed structure. An optimal design of the bamboo-inspired structure was obtained by particle swarm optimization and the results reveal that, with the initial peak force (IPF)/SEA almost unchanged, the associated performance in SEA/IPF is significantly improved. Along with this guideline, it may provide a meaningful avenue towards the design of new bio-inspired energy absorption structures.

Buffering energy-absorbing performance of multi-cell octagonal biomimetic structure with cylinder and sinusoidal guide line

In order to explore the bionic buffering energy-absorbing structure with better development and research performance, two bionic structural models (called EBETS or MBETS) with sinusoidal guide line and cylinder located at the end or center of the octagonal side are designed in this paper. In comparison between these two models and models without sinusoidal guide line (EBET, MBET), we use the finite element method and study the crashworthiness and its mechanism of influence under different amplitudes (A) and wavenumber (N): (1) The trend characteristics of change of crashworthiness indicators of EBETS and MBETS with the increase of N or A were discovered in this paper. On this basis, new buffering energy-absorbing structure with better performance ( A = 0.5, N = 20) were proposed. (2) Compared to common multi-cell and single-cell buffering energy-absorbing structures, we can safely confirm that the structure has better energy-absorption performance and have its superiority as well. (3) Based on the advantages of 3D printing technology, it is proposed to replace the single-cell structure with appropriate EBETS or MBETS, and the selection method is given in this paper.

Analysis of Single Event Response and Hardening Methods in 1.2 kV SiC Power MOSFET With Multicell and Termination Structure

Analysis of Single Event Response and Hardening Methods in 1.2 kV SiC Power MOSFET With Multicell and Termination Structure

Crashworthiness performance and optimization of multi-cell aluminum tubes under axial loading

Multi-cell thin-walled tubes have been proven to be an efficient energy absorber with well-controlled deformation stability and high energy absorption capability. Nevertheless, research on multi-cell tube energy absorbing structures mainly focused on the fields of small size and light energy absorption. The high cost and low crushing force significantly restrict their applications in practical engineering, especially for large-size equipment, such as train crashworthiness protection. To address this limitation, this paper presents a novel multi-cell tube energy absorption structure made of aluminum alloy for ultra-large energy absorption field with features of low cost (extrusion and welding processing), large size (450 mm × 280 mm × 280 mm), light weight (∼9 kg), high energy absorption capacity (>200 kJ) and large crushing force (>600 kN). The proposed multi-cell structure is composed of four extruded square tubes connected by welding. To demonstrate the feasibility of the proposed structure, the sample is fabricated and dynamic impact test is performed. Experimental results show that the tube buckles progressively and forms plastic folding lobes with a total absorbed energy of 235.6 kJ and a mean impact force of 668.7 kN, which are about 500% higher than that of previous reported multi-cell structures. Finite element simulation and theoretical model are developed and well-capture the experimental deformation process. The relative errors of theoretical and simulation mean crushing force, Effective crushing distance coefficient, energy absorption and maximum crushing distance in comparison experimental results are all within 10%. Based on the validated finite element model, the effect of geometrical parameters of the proposed structure on its crashworthiness performance is analyzed. Finally, we construct the response surface models of the multi-cell tube and optimize the absorbed energy under a mass constraint by Multi-objective Non-dominated Sorting Genetic Algorithm (NSGA-II). The Pareto front of structure energy absorption and mass is obtained. In particular, under the constraint of total mass M = 9 kg, the optimal solution with maxing energy absorption is t = 4.999 mm, α = 0.342 mm, and w = 281.5 mm. The proposed structure can be applied to ultra-large energy absorption fields such as train crashworthiness protection.

A comparative study on dynamic compression response of multi-cell thin-walled structures with filling foams and connecting ribs

In order to comparatively study effect of foam filling and connecting ribs on dynamic response of multi-cell thin-walled structure (MTS), high velocity (30–70 m/s) mass block impact tests were performed on empty MTS, polyurethane foam (PUR) filled MTS (FMTS) and 2nd order MTS (MTS-2nd) with connecting ribs between sub-cells. The dynamic enhancement mechanism of energy absorption of three kinds of thin-walled structures was discussed based on experimental and numerical results. The results indicate that the dynamic enhancement coefficient (DEC) of the mean crushing force (MCF) is 1.07–1.23 and 1.08–1.33 for empty MTS and FMTS, respectively. The dynamic enhancement of total energy absorption (EA) is 11.4–26.32% for MTS, 13.83–32.52% for FMTS and 4.3–9.68% for MTS-2nd, compared to the quasi-static compression. The multi-cellularization tends to degenerate the crushing force sensitivity of MTS to the loading rate, while the foam filling increases the sensitivity. The inertia effect is the main reason for the dynamic enhancement of crushing force of thin-walled structures. The coupling effect of FMTS is related to the dimensions of sub-cells, the impact velocity and the foam strength. The folding pattern and deformation stability of MTS can be improved by filling foams and increasing impact velocity. The multi-cellularization by using connecting ribs is still the most effective method to improve the specific energy absorption of thin-walled structures, although it causes a size effect and reduces the robustness of deformation modes.

Dynamic response and protection effectiveness of fluid filled concave multicell structure under air blast

To harness the mechanical properties of concave multicell structures under explosive loading, a fluid filled concave multicell structure that combined the concave multicell pattern with a fluid filled structure was designed. The dynamic response and protective effectiveness of the designed structure under air blast loading were studied through experimental and numerical simulations, and their relationships with wave propagation process, structural deformation mode, protection effectiveness, and energy absorption were analyzed. The impact of fluid filling configuration and blast distance on the structure was also investigated. The results showed that the designed multicell structure had five typical deformation modes, and that changes in fluid filling configuration affected the stiffness distribution and local constraints of the concave multicell structure, altering wave propagation process, deformation, and energy absorption. It was also found that an increase in fluid filling caused a fluctuating decline in protective effectiveness, with the front plate and front core being the main energy absorbing parts. An alternative arrangement of fluid-filled and unfilled cells, which created a compound load propagation path combining solid, liquid, and gas media in various directions, effectively reduced the loading intensity, induced the structure to undergo horizontal compatible deformation and horizontal compatible-bulging deformation, and improved its protection effectiveness.

Mechanical performance of multi-cell thin-walled tubes under static and dynamic axial loading

In this paper, the mechanical performance of multi-cell thin-walled tubes with small aspect ratio and diameter thickness ratio and the same weight was studied theoretically, numerically and experimentally. The lightweight devices impact test was designed to get a higher velocity than the drop-weight crashing test or impacting trolley test and the experimental tests were carried out under static and dynamic axial loading. The theoretical mean crushing force (MCF) was obtained according to the simplified super folding element (SSFE) theory, and structural coefficient of the homoeomorphic structure was obtained. Then the numerical models were conducted to investigate the strain hardening on the matrix material. The results showed that the dynamic amplification factor (DAF) for the multi-cell tube to predict the MCF precisely could be ignored at or below the impact velocity 50 m/s. In addition, the experimental results indicated the initial peak forces (IPF) of the tubes were sensitive to the total length of all flanges of the cross-section. The multi-cell partitioning could improve the energy absorption of the thin-walled structures and relieve the increment of the dynamic axial loads. The energy absorption efficiency of multi-cell structure with circular tube is higher than that of multi-cell structure with square tube. The numerical model indicated the dynamic axial impact could lead to the strain hardening of the matrix material. The significant strain hardening could lead to more increment of the force.

Bio-inspired multi-cell tubular structures approaching ideal energy absorption performance

The energy absorption potential of conventional thin-walled tubes is compromised by the long-wavelength folding lobes, which result in a mean crushing force that is much smaller than their yield strength. Here, inspired by the characteristics of the skeletal of the glass sponge, a new thin-walled multi-cell tubular structure with modified face-centered cubic (MFCS) cross section is proposed. The compression behaviors and energy absorbing capacity of the proposed structure were compared with those of the traditional multi-cell tube through finite element simulation and experimental tests. Compared with the traditional multi-cell tubes, the proposed MFCS structure exhibits micro-folding lobes with shorter wavelength, resulting in larger energy absorption, higher energy absorption efficiency and a more stable and controllable deformation mode, with the mean crushing force almost reaching that of an ideal energy absorber. Moreover, the effects of the geometric coefficient of MFCS multi-cell tube on the energy absorption performance and deformation pattern were studied parametrically. Through the bionic design, extraordinary energy absorbing performance is achieved, providing guidance for future design of lightweight structures with unprecedented mechanical properties.

A Few-Shot Learning-Based Crashworthiness Analysis and Optimization for Multi-Cell Structure of High-Speed Train

Due to the requirement of significant manpower and material resources for the crashworthiness tests, various modelling approaches are utilized to reduce these costs. Despite being informative, finite element models still have the disadvantage of being time-consuming. A data-driven model has recently demonstrated potential in terms of computational efficiency, but it is also accompanied by challenges in collecting an amount of data. Few-shot learning is a perspective approach in addressing the problem of insufficient data in engineering. In this paper, using a novel hybrid data augmentation method, we investigate a deep-learning-based few-shot learning approach to evaluate and optimize the crashworthiness of multi-cell structures. Innovatively, we employ wide and deep neural networks to develop a surrogate model for multi-objective optimization. In comparison with the original results, the optimized result of the multi-cell structure demonstrates that the mean crushing force (Fm) and specific energy absorption (SEA) are increased by 17.1% and 30.1%, respectively, the mass decreases by 4.0%, and the optimized structure offers a significant improvement in design space. Overall, this proposed method exhibits great potential in relation to the crashworthiness analysis and optimization for multi-cell structures of the high-speed train.