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The deformation modes and energy absorption performances of thin-walled concave profile tubes subjected to axial crash were investigated, and the advantages of concave tubes over conventional convex polygonal tubes in improving energy absorption performances were demonstrated. The classification of axial deformation modes of concave tubes and their variations with cross-section parameters were studied with the finite element method, and the concave tubes under oblique impact loads were also investigated. The concave tubes show dramatic improvements of energy absorption performances over the conventional square tubes. [ABSTRACT FROM AUTHOR] more...

AbstractIt is widely known that thin-walled structures are expected for numerous engineering devices, due to lightweight, high specific strength, and excellent energy absorption capacity. Thus, the new high-efficiency energy absorbing (EA) device is the eternal pursuit goal of designers. A novel high-efficiency energy-absorbing device of the metal square origami foam-filled tube (MSOFT) under axial compression is designed in this article, and axial crushing of the MSOFT is investigated analytically and numerically. An analytical model for axial crushing of MSOFT is established based on the conservation of energy and the hyper-folded unit theory, considering the energy absorbed by the deformation of metal origami tube, foam compression, and the interaction between foam and origami tube. Then, the finite element (FE) simulation of MSOFTs under axial compression are conducted by Abaqus/Explicit software, and found that theoretical results are in good consistency with the FE results. Then, the influences of yield strength, wall thickness, height and cross-section width of the tube, and foam strength of MSOFT under axial compression are discussed, and found that the force and energy increases when the above parameters increase. Finally, the mean crushing force (MCF) and the crushing force efficiency (CFE) among MSOFT, origami tube and square tube are compared. Compare with the origami tube and square tube, the MCF of MSOFT increases by 40.8–106.9% and 12.1–49.8%, and the CFE of MSOFT increases by 101.2–266.3% and 1.1–12.4%. It is indicated that for a wide range of geometric and material parameters the MSOFT exhibits predictable and stable collapse behavior. [ABSTRACT FROM AUTHOR] more...

The concept of both hierarchy and gradient are incorporated into thin-walled hexagonal tubes for a configuration with optimum crashworthiness and energy absorption. Graded hierarchical hexagonal (GHH) tubes are developed by replacing the corners of an original hexagonal tube with a series of micro hexagonal cells. The total net cross-sectional area as well as the mass are kept the same for all the GHH tubes. The axial crushing behavior of the GHH tubes is investigated in terms of deformation modes, crushing forces and energy absorption. Theoretical solutions are also derived to predict the mean crushing forces (MCFs) of the GHH tubes. Two deformation modes have been identified, a locally layer-by-layer folding deformation (Mode-L) and a globally buckling-like deformation (Mode-G). The hierarchical and graded parameters have significant but quite different influences on the crushing behavior of GHH tubes. The MCF and the specific energy absorption (SEA) can be significantly improved with reasonably hierarchical and graded arrangements, while the initial peak force (PF) remains almost constant. A type of new class of graded hierarchical hexagonal (GHH) tubes are constructed. Two deformation modes have been identified, a locally layer-by-layer folding deformation (Mode-L) and a globally buckling-like deformation (Mode-G). The hierarchical and graded parameters have significant but quite different influences on the crushing behavior of GHH tubes. The crashworthiness in terms of mean crushing force and specific energy absorption can be significantly improved by choosing reasonable configurations [ABSTRACT FROM AUTHOR] more...

The foldcore of an origami structure made up of rigid triangular units is suggested. This foldcore has two stable states: contraction and expansion. The suggested foldcore's peak stress, average stress, and densification strain were numerically analyzed at different cutting heights and varied parameters n, and the damage modes were analyzed. Finally, the impact of strain rate on the proposed foldcore's structural response and energy absorption capacity is investigated. The contraction stable state foldcore with a cutting 1/5 height was discovered to have the best energy absorption capacity. Increasing n improves its energy absorption performance, but decreases its dense strain. [ABSTRACT FROM AUTHOR] more...

AbstractA kind of five-cell tube with the characteristic of multi-corner was proposed and named as multi-corner five-cell tube. Quasi-static compression tests were carried out to validate the finite element model which was used to simulate the crushing of the multi-corner five-cell tubes with different configurations. The fold wavelengths of every single wall of the tubes were analyzed and compared with their natural wavelengths—a newly proposed concept in this article. Theoretical method dealing with deformation incompatibility was developed using the natural wavelengths. Configuration effect on the energy absorption performance of the multi-corner five-cell tube was discussed. [ABSTRACT FROM AUTHOR] more...

Metal/CFRP hybrid structures have been increasingly applied in the automotive industry due to their favorable weight-saving and crashworthiness. In this article, a nonlinear finite element (FE) model is established to study the axial crushing behavior of aluminum/CFRP thin-walled tube structures. A progressive damage constitutive model is employed to capture the intra-laminar response of composites; Johnson-Cook model is used to describe the crushing process of aluminum layers and a bilinear cohesive zone model is applied for modeling the inter-layer delamination during the collapse process. A user material subroutine VUMAT involving these damage models is coded and executed to attain the numerical solution based on ABAQUS/Explicit solver. The axial crushing processes of thin-walled tubes with different configurations are simulated, and the corresponding damage characteristics are analyzed thoroughly. The influence of aluminum layer arrangement and cross-sectional shape on the crashworthiness and energy absorption of thin-walled tubes is discussed, which provides a design basis for the application of energy absorption elements. [ABSTRACT FROM AUTHOR] more...

AbstractThis study proposes two innovative thin-walled structures: the spiral tube (ST) and the multi-cell spiral tube (MCST), with MCST demonstrating better energy absorption performance. Through numerical simulation, geometric parameters of MCST are analyzed for their effect on crashworthiness performance. MCST with inner diameter of 15 mm, rotating angle of 4π, pitch of 18 mm and 6 ribs has the best energy absorption performance, and the SEA of MCST increases by up to 16.2% compared to the multi-cell circular tube, indicating superior energy absorption performance. The findings promote the optimization and application of structures in automotive energy absorption components. [ABSTRACT FROM AUTHOR] more...

Longitudinal corrugated tubes (LCTs) exhibit stable platform force under axial compression but have low specific energy absorption. Conversely, circumferential corrugated tubes (CCTs) offer higher specific energy absorption but with unstable platform force. To overcome these limitations, this paper introduces a novel bi-directional corrugated tube (BCT) that amalgamates the strengths of both the CCT and LCT while mitigating their weaknesses. The BCT is formed by rolling a bi-directional corrugated structure into a circular tubular form. Numerical simulations of the BCT closely align with experimental results. The study further examines the influence of discrete parameters on the BCT's performance through simulations and identifies the tube's optimal design using the integral entropy TOPSIS method. A full factorial experimental approach is then employed to investigate the impact of radial amplitude, axial amplitude, and neutral surface diameter on the crushing behavior of the BCT, comparing it with the CCT and LCT. The results reveal that increasing A i enhances the axial resistance of the structure, while increasing A j reduces the buckling effect, resulting in a higher specific energy absorption and lower ultimate load capacity for the BCT compared to the CCT and LCT. A simultaneous multi-objective optimization of the CCT, LCT, and BCT confirms that the BCT offers superior specific energy absorption and ultimate load capacity. The optimal configuration parameters for the BCT have been determined, providing significant insights for practical applications in crashworthiness engineering. [ABSTRACT FROM AUTHOR] more...

Composite thin‐walled tubes made of glass fiber reinforced plastics (GFRP) are attracting great attention due to their lightweight and outstanding crashworthiness capacity. Implementing triggers to the design of GFRP composite tubes enables a further increase in specific energy absorption while simultaneously reducing peak crushing force. Motivated by these facts, a notch‐type triggering mechanism is suggested in this work to enhance the energy absorption capabilities of circular GFRP composite tubes. GFRP tube samples with (0°/90°)8 layups are manufactured using the roll wrapping process. Subsequently, these samples are triggered and subjected to quasi‐static axial compression tests. The diameter, quantity and placement of the triggering notches are selected as design parameters, and experiments are carried out using Taguchi's L9 orthogonal array. Each of these parameters has three levels to identify the optimal combination of design parameters. To optimize multiple responses, the weighted aggregated sum product assessment, a multiple criteria decision‐making technique, is employed in conjunction with mono‐criteria optimization. The findings indicated that substantial enhancements can be realized in all parameters related to energy absorption performance by triggering progressive crushing modes in a controlled manner using a notch‐type triggering mechanism. In particular, the findings indicated that the specific energy absorption and the crush force efficiency of the intact GFRP composite tubes could be improved up to 18% and 68.3%, respectively, by the selection of appropriate triggering parameters. Highlights: Axial crushing and optimal design of triggered GFRP tubes are investigatedNumber, diameter, and center distance of the notches are chosen as parametersTaguchi experimental design is used for the best configuration of parametersThe optimum configurations are investigated using the entropy‐WASPASSignificant improvements are achieved using the trigger mechanism [ABSTRACT FROM AUTHOR] more...

The sandwich corrugated square tubes (SCSTs), which includes outer square tube (OST), inner square tube (IST) and middle corrugated square tube (CST), have been has been proved to have excellent energy absorption performances. In order to further increase its performance and obtain the optimal structural parameters, multi-objective optimization of SCSTs is carried out. The surrogate modals for the SCSTs were constructed, and the main effects and the interaction effects were analyzed in detail. Finally, multi-objective particle swarm (MOPSO) optimization was used for multi-objective optimization of the SCSTs. The optimization results show that Pareto frontier of the SCSTs can reach a larger range than the SCSTs with A = 0 mm. Due to the coupling effect, energy absorption (EA) and initial peak force (Fmax) of the optimal design solution of the SCSTs are increased by 13.76% and decreased by 8.76% respectively compared to the sum of IST, OST and CST crushing alone. Two key indicators, including Fmax and EA, have been improved at the same time. more...

There is accelerating demand for energy-absorbing structures fabricated from lightweight materials with idealized, near-constant force responses to simultaneously resolve the engineering challenges of vehicle mass reduction and improved occupant safety. A novel compounded energy dissipation system composed of AA6061-T6 and AA6061-T4 tubing subjected to hybrid cutting/clamping and H130, H200 and H250 PVC foam compression was investigated utilizing quasi-static experiments, finite element simulations and theoretical modeling. Identical structures were also subjected to axial crushing to compare with the current state of the art. The novel cutting/foam crushing system exhibited highly stable collapse mechanisms that were uniquely insensitive to the tube/foam material configuration, despite the disparate material properties, and exceeded the energy-absorbing capacity and compressive force efficiency of the axial crushing mode by 14% and 44%, respectively. The simulated deformation profiles and force responses were consistent with the experiments and were predicted with an average error of 12.4%. The validated analytical models identified numerous geometric/material configurations with superior performance for the compounded AA6061/PVC foam cutting/foam crushing system compared to axial crushing. An Ashby plot comparing the newly obtained results to several findings from the open literature highlighted the potential for the compounded cutting/foam crushing system to significantly outperform several alternative lightweight safety systems. [ABSTRACT FROM AUTHOR] more...

Origami crash tubes have concerned nowadays due to their superior crashworthiness behaviour by controlling the initial buckling force and collapse modes. In this paper, a new multi-layered origami pattern is proposed and fabricated, and a numerical study is performed under quasi-static axial compressive loading and validated by the experimental result of the fabricated origami crash box. To compare the energy absorption efficiency of this proposed origami tube, its mechanical responses are normalised with the conventional octagonal tube. Moreover, the crashworthiness behaviour of 64 samples is investigated for the dihedral angle 2θ, outer layer height e, and module number M in the parametric study. It is demonstrated that by increasing M for tubes with a constant value of e, the critical angle of θ decreases. By increasing the value of e for tubes; while, considering the values of M and θ constant, the mechanical responses of the tubes increase, and these trends are valid as long as θ is below the critical angle. The number of modules M, angle θ, and outer layer height e have the highest effect on the mechanical responses. Finally, the results show that by maintaining the specific energy absorption of the conventional octagonal tube, the initial peak force can be reduced about 55%. In consequence, the proposed pattern reduces the initial peak force while maintaining the specific energy absorption. [ABSTRACT FROM AUTHOR] more...

The sandwich corrugated square tubes (SCSTs), which includes outer square tube (OST), inner square tube (IST) and middle corrugated square tube (CST), have been has been proved to have excellent energy absorption performances. In order to further increase its performance and obtain the optimal structural parameters, multi-objective optimization of SCSTs is carried out. The surrogate modals for the SCSTs were constructed, and the main effects and the interaction effects were analyzed in detail. Finally, multi-objective particle swarm (MOPSO) optimization was used for multi-objective optimization of the SCSTs. The optimization results show that Pareto frontier of the SCSTs can reach a larger range than the SCSTs with A = 0 mm. Due to the coupling effect, energy absorption (EA) and initial peak force (F max) of the optimal design solution of the SCSTs are increased by 13.76% and decreased by 8.76% respectively compared to the sum of IST, OST and CST crushing alone. Two key indicators, including F max and EA, have been improved at the same time. [ABSTRACT FROM AUTHOR] more...

The axial crumpling of frusta in the axisymmetric "concertina" mode is examined. A new theoretical model is developed in which the inward folding in both cylinders and frusta is addressed. The results were compared with previous relevant models as well as experimental findings. The flexibility of the model was substantiated by its capability of describing and estimating the inward folding in frusta in general as well as in cylinders as a special case. A declining trend of the eccentricity dependence with the D/t ratio was found in contrast with a previous theory which suggests total independency. ABAQUS 14-2 finite element software was employed to simulate the thin tube as a 3-D thin shell part. Numerical simulations of the process were found to, firstly, underestimate the theoretical values of inward folding in general, secondly anticipate more underestimations as the tubes become thinner and/or have larger apex angle, and finally anticipate as low as 300 apical angle frusta to revert its mode of deformation to global inversion. more...

The crushing of crash boxes is a complex phenomenon characterized by a strong interaction of structural and material properties. Many attempts to improve their energy absorption by adopting one aspect resulted in unacceptable unprogressive bucking. Thus, special considerations are required for crash box optimization including both material and structural effects. In this study, the structural behavior of the crash box is analyzed and a new design approach is introduced to fulfill these requirements. Currently, components, processes, and materials are mainly developed independently. However, to exploit the full potential of modern materials in component design, integrative development work is necessary. Component performance-based requirements and corresponding local material properties must be taken into account concurrently. In this work, a component-driven material design approach is presented, in which local-material-property requirements are derived from component simulations. This new approach is demonstrated by the use case of a quasistatically deformed crash box produced out of steel DP600 for the optimization target "energy absorption". The finite element simulations were carried out on the crash box, and required material properties for improving the crash box performance were derived based on the simulations. Heat treatment strategies were developed afterwards and experimentally validated to fulfill these requirements. The finite element (FE) simulations based on the experimentally extracted material properties reveal the potential of the component-driven material design approach to improve the crash box performance. The introduced approach enables exploiting the full energy-absorption capacity of the material while ensuring the desired service behavior of the component. [ABSTRACT FROM AUTHOR] more...

In this study, the axial crushing behavior of aluminum/carbon fiber reinforced plastic (CFRP) hybrid tubes are systematically investigated numerically based on a three‐dimensional (3D) progressive damage model. Experiments concerning hybrid tubes with 1/1 and 2/1 lay‐up configurations are performed first to validate the numerical model. Then, the effects of chamfer at the end, stacking configuration, aluminum‐CFRP bonding state and thickness ratio of individual layers on the energy absorption characteristics of aluminum/CFRP tubes are further numerically analyzed. The simulation results suggest that the 3D progressive damage model can effectively simulate the crushing failure process and reveal the energy dissipation mechanism of aluminum/CFRP hybrid tube under crushing. It is observed that increasing the thickness of the CFRP layer does not promote the energy absorption, but the best energy absorption effect can be obtained by using a 1:1 ratio for the thicknesses of the inner and outer aluminum alloy layers in 2/1 hybrid tube. Finally, the economic performance of 2/1 hybrid tube, 1/1 hybrid tube, and aluminum alloy tube as energy‐absorbing structures is theoretically examined. The balance between mass and cost of the 2/1 hybrid tube is proven to be evidently better than that of the conventional 1/1 hybrid tube. [ABSTRACT FROM AUTHOR] more...

A type of tube with corrugated patterns, aiming at inducing extension deformation, was proposed in this paper. Fifteen patterned tubes and one conventional square tube were simulated using the finite element model which was validated by an axial quasi-static compression experiment. The numerical results show that four deformation modes generated, which are closely related to the patterns number and the pattern angle. Tubes deform in D mode has the highest energy absorption. The influence of geometric parameters and wall thickness on energy absorption performance was also investigated. A geometric optimization was carried out as well. Deformation mechanism of two of the four modes, EF mode and E mode, were established and theoretical predictions of mean force were derived. The energy absorptions of different deformation forms were analyzed, and the results show that half of the energy is dissipated by extension deformation in E mode but little in EF mode. [ABSTRACT FROM AUTHOR] more...

This research, which is a continuation of the previously published paper, develops the idea for estimating the behavior of axially crushed multicell thin walled structures. This approach employs new crushing mechanisms or simply crushing modes for different configurations of multiweb corner elements based on simulation, geometric, and kinematic observations. Furthermore, a new model is introduced named as "Induced Curvature Model" or ICM which includes the curvature of the sheet during progressive crumpling and also the hardening effect of the material under plastic deformation, instead of simple assumptions of perfect plastic material and hinge lines for the folds in case of previously offered plastic hinge model (PHM). Both ICM and PHM are employed to capture crushing properties based on the offered crushing modes and the results suggested by them are compared to each other. Different aspects of crushing behavior were studied and discussed. To show the validity of the proposed models, FE simulation studies were also conducted. Results show an average error around 7% which indicates a good agreement between theoretical and simulation findings and the applicability of the proposed novel model to a wide range of thin walled structures. [ABSTRACT FROM AUTHOR] more...

This paper presents an experimental investigation about the effect of the hole on the crushing force of thin tubes with the square cross-section under axial impact with a high strain rate. To this end, 24 absorbers were studied and their crushing properties were extracted and compared with a simple absorber. The effect of different parameters, including hole diameter, sample length, sample cross-section size, and impact speed were also evaluated. It was found that in hole square thin-wall tubes with high strain rates, an increase in tube length did not affect the maximum force. The results showed that considering cylindrical tubes, average and maximum force in square thinwall tubes without a hole are less than those with holes; this difference in force was not significant but collapse force efficiency (CFE) decreased to 46%. Moreover, by the increase of hole diameter, the maximum force to square thin wall decreased. [ABSTRACT FROM AUTHOR] more...

The axial crumpling of frusta in the axisymmetric "concertina" mode is examined. A new theoretical model is developed in which the inward folding in both cylinders and frusta is addressed. The results were compared with previous relevant models as well as experimental findings. The flexibility of the model was substantiated by its capability of describing and estimating the inward folding in frusta in general as well as in cylinders as a special case. A declining trend of the eccentricity dependence with the D/t ratio was found in contrast with a previous theory which suggests total independency. ABAQUS 14-2 finite element software was employed to simulate the thin tube as a 3-D thin shell part. Numerical simulations of the process were found to, firstly, underestimate the theoretical values of inward folding in general, secondly anticipate more underestimations as the tubes become thinner and/or have larger apex angle, and finally anticipate as low as 300 apical angle frusta to revert its mode of deformation to global inversion. [ABSTRACT FROM AUTHOR] more...

Active adaptive energy dissipation systems can receive and interpret data from onboard vehicle sensors to respond to external stimuli by modifying their geometries and corresponding load bearing capacities. This is a highly promising subfield in structural crashworthiness since these devices possess multiple potential configurations, thus allowing them to achieve the preferred balance between high-capacity energy absorption and mitigation of human injury for a broad and disparate range of loading conditions. A novel cutting-based active adaptive energy absorber was conceptualized, design and theoretically assessed in this investigation with guidance from previous experimental observations and extensively validated modeling approaches. The proposed, hydraulically-driven active adaptive cutter (HAAC) was capable of transitioning between 4, 6, 8 and 12-bladed cutting deformation modes in either direction (e.g., from 6 to 12-bladed cutting or vice versa) and in a nondestructive manner. The steady-state force capacity could be varied by an average factor of 2.6, quantifying the significant range available to the HAAC regardless of extrusion material or geometry. A broad scale analytical study revealed that the proposed HAAC could eclipse the energy absorbing performance of the traditional axial crushing deformation mode for AA6061-T6 extrusions with 50.80 mm to 76.20 mm diameters and 1.59 mm to 3.18 mm wall thicknesses, with an average enhancement of 73 % calculated for the 12-bladed cutting mode. The newly proposed active adaptive capabilities allow the system to carefully balance energy absorption requirements and mitigation of occupant/pedestrian injury in a manner which the current state-of-the-art cannot achieve. more...

• A novel polygonal asymmetric origami tube (PAT) is designed to produce more traveling plastic hinge lines. • The deformation process of the PAT is verified through axial crushing experiments, numerical models, and impact experiments, and the deformation mechanism is summarized. • The deformation theory analysis demonstrates that the PAT can realize hierarchical deformation and avoid stress concentration at sharp corners. • The average crushing force of PAT is analyzed and predicted by theoretical analysis. Origami tubes have attracted widespread attention because it is inclined to deform in the complete diamond mode (DM) with a low initial peak force F max and high average crushing force F ave. Although conventional origami tubes can improve crashworthiness, there are still many areas that fail to generate traveling plastic hinge lines, and the crashworthiness can be further improved. This paper presents a novel polygonal asymmetric origami tube (PAT) with origami patterns that can trigger more traveling plastic hinge lines compared to those of conventional origami patterns. The theoretical analysis of the deformation mechanism suggests that the PAT can realize hierarchical deformation and avoid stress concentration at sharp corners. The quasi-static experiments and numerical simulations reveal that the novel origami pattern can successfully trigger up to four times more traveling plastic hinge lines than the conventional square box (CSB) under the premise that each plastic hinge line is similar in length. Compared with the CSB, the PAT can deform in DM with a 56.0 % reduction of F max and a 59.1 % increase of F ave. Notably, the stableness of load-carrying capacity SLC is 90.2 %, which is 260.8 % higher than the CSB. A series of parametric studies reveal that the dihedral angle ratio α / β and the width-to-thickness ratio c / t of the PAT have a significant effect on crashworthiness. A smaller ratio of α / β and c / t provides the PAT with superior crashworthiness. Comparing the PAT with other types of origami tubes and multi-cell tubes indicates that the PAT also exhibits outstanding crashworthiness. The impact experiments also unveil a significantly enhanced crashworthiness of the PAT. Compared with the CSB, the F max decreases by approximately 46.4 %, while the F ave increases by around 92.7 %. The SLC and SEA values for the PAT surpass those of the CSB by about 260.8 % and 93.1 %, respectively. Furthermore, the theoretical analysis for predicting the F ave of the PAT is developed, with a maximum error not exceeding 8.5 %. [Display omitted] [ABSTRACT FROM AUTHOR] more...

Multi-wall profile as one of the most widely approaches can enhance the crashworthiness properties in thin-walled tubular structures. In actual application process as energy absorbers, there may be a variety of circumstances including axial crushing and lateral crushing. However, the crashworthiness in the multi-wall tubular structure considering both axial crushing and lateral crushing circumstances has rarely been evaluated in the existing literature. In the study, a new tailored-property multi-wall thin-walled structure (TMTS) is put forward to increase the ultimate strength of this material in the region of corner to accommodate two conditions including lateral and axial crushing conditions. Finite element models verified from experiments were established in PAM-CRASH to analyse the crashworthiness performance for this structure. Under lateral and axial crushing, it was revealed that TMTSs exhibited obvious superiority to the corresponding traditional structures. It was concluded that wall thickness, tailoring length and other geometry parameters could effectively influence the crushing performance of the TMTSs. In addition, the progressive deformation mode could be exhibited by the well-designed TMTSs under axial impact. Furthermore, the theoretical model of the TMTS was proposed according to the Super-folding Element Theory. Theoretical analysis is consistent with simulation results, which proves that the deformation formula and the analytical model are all correct. Finally, according to the multi-objective optimisation method, the thicknesses of tailored and non-tailored regions of the TMTS were reasonably configured to further enhance crashworthiness. The research results provide good guidance and theoretical support for the development of novel lightweight energy-absorbing structures under various loading circumstances. [ABSTRACT FROM AUTHOR] more...

This work reports the performance of energy absorbers made in mild-steel and aluminum thin-walled square tubes under quasi-static compression tests. They have circular holes discontinuities laterally drilled on two or four opposing faces of the tube, according to three different distances based on the effective crushing distance, resulting in 23, 36, and 46 mm, as well as two diameters 8 and 12 mm. The tubes are 300 mm in effective length, 50 mm wide, and thickness varies. A substantial variation at performance parameters occurs with wall thickness and material changes. Failure initiators with 12 mm in diameter distant from each other 23 and 36 mm lead to better performance for aluminum and steel absorbers, respectively. Von Mises equivalent stress reaffirms that failure initiator influences stress distribution; consequently, the deformation process and; eigenvalue buckling analysis highlights the relation of buckling effect with the peak force and the stiffness of the tube face. [ABSTRACT FROM AUTHOR] more...

A new prefolded tube is proposed by introducing web into a thin-walled tube based on "Miura origami". The quasi-static compression analysis of this tube shows that the web has an important influence on deformation mode and energy absorption. Compared with a circular tube, the new thin-walled tube not only maintains the superior performance of low initial peak force and induced deformation mode, but also has a better energy absorption capacity. The influences of the number of units, edges, and prefolding angle on the deformation process of the new thin-walled tube are determined through parameter analysis. An optimized structure is designed, and the initial peak force is reduced. The energy absorption of the new structure under quasi-static compression is also theoretically analyzed, and the theoretical results are in good agreement with the numerical simulation results. [ABSTRACT FROM AUTHOR] more...

Energy absorption characteristics of polygonal multi-cell tubes with different cross-sectional shapes under quasi-static axial crushing are investigated systematically. Based on the SSFE theory and CE method, theoretical models for predicting mean crushing force of tubes are proposed, and theoretical expressions of normalized mean crushing force (NFm) and normalized special energy absorption (NSEA) of tubes are derived. Numerical models for predicting the energy absorption characteristics also are established using the software ABAQUS/Explicit. The results of theoretical predictions and numerical simulations about 36 design conditions are in good agreement with experimental results those obtained by previous authors. Adding inner panels can improve the energy absorption characteristics of thin-walled tubes. And adding Cross-type inner panels in S, H and O single-cell tubes has more remarkable improvement than that of adding X-type and Y-type inner panels. The NFm increases with the increase of wide-thickness ratio, and NSEA decreases with the increase of wide-thickness ratio. [ABSTRACT FROM AUTHOR] more...

The axial crushing of thin-walled metal circular tubes was addressed in this work for its importance in many engineering applications especially when failed in concertina mode. Theoretical estimates of the peak load were formulated for lower and upper bounds based on Rankine-Gordon principle and the elastic-plastic criterion of buckling, respectively. Numerical simulations were also made to validate these estimates using ABAQUS 14-2 finite element software. Previous findings were compared with both the theoretical and numerical results of the present work. It is found that the peak load is unique for a particular specimen, while the lower bound stress can be equal for different values of D, t and L, as long as the D/t ratio is the same. Moreover, the upper bound stress requires both D/t and L/D ratios. It was also found that all numerical results agree favorably with the theoretical predictions, but not with all of the experimental findings. This partial disagreement was proved to be attributed to the questionable data extracted from one of the cited work. Empirical relations for the available experimental findings were established to confirm the source of disagreement as well as to afford a unified relation which might represent data of different materials, and finally to offer an alternative prediction of experimental peak load. [ABSTRACT FROM AUTHOR] more...

The crushing of crash boxes is a complex phenomenon characterized by a strong interaction of structural and material properties. Many attempts to improve their energy absorption by adopting one aspect resulted in unacceptable unprogressive bucking. Thus, special considerations are required for crash box optimization including both material and structural effects. In this study, the structural behavior of the crash box is analyzed and a new design approach is introduced to fulfill these requirements. Currently, components, processes, and materials are mainly developed independently. However, to exploit the full potential of modern materials in component design, integrative development work is necessary. Component performance-based requirements and corresponding local material properties must be taken into account concurrently. In this work, a component-driven material design approach is presented, in which local-material-property requirements are derived from component simulations. This new approach is demonstrated by the use case of a quasistatically deformed crash box produced out of steel DP600 for the optimization target “energy absorption”. The finite element simulations were carried out on the crash box, and required material properties for improving the crash box performance were derived based on the simulations. Heat treatment strategies were developed afterwards and experimentally validated to fulfill these requirements. The finite element (FE) simulations based on the experimentally extracted material properties reveal the potential of the component-driven material design approach to improve the crash box performance. The introduced approach enables exploiting the full energy-absorption capacity of the material while ensuring the desired service behavior of the component. more...

In this study, a type of tube with an open-hole AL alloy tube nested outside the CFRP tube is designed and fabricated, and the energy absorbing characteristics and failure mechanism under quasi-static axial compression are discussed. It is found that the summing tube composed of two single tubes has less energy absorption than the hybrid tube. Numerical simulation and theoretical models are used to evaluate the influence of the hybrid tube in terms of cost and weight, and it is found that under the same energy absorption, the hybrid tube has a weight reduction of 39.2% compared to the open-hole AL tube, which was 25.7% of the cost of the CFRP tube. This hybrid structure has potential as the load-carrying and energy absorption tube. more...

This paper focuses on the energy absorption of additively manufactured or 3D printed lattice-core sandwich structures of different configurations. The compressive behavior of 3D lattice structures with rhombic dodecahedron unit cells is investigated at Quasi-static loading. A parametric analysis was performed, using a Box-Behnken design (BBD), as a method for design of experiments (DOE). Then, the influence of the angle between struts and their diameter were investigated. It was observed from experimental data that the angle between struts had the highest degree of influence on the specific energy absorption. The results showed that the diameter of struts has been the most influential parameter to increase mean and peak forces. The results from using the design expert software showed the optimal specific energy absorption and peak force to be 2.1014 J/gr and 2224.87 N, respectively. [ABSTRACT FROM AUTHOR] more...

This study aims to investigate the crashworthiness performance of thin-walled tapered tubes with hybrid geometry (HG-tubes) both experimentally and numerically (finite element code LS–DYNA) under quasi-static axial compression. The HG-tube cross section progressively changes along the axial length from circular to square. First, axial crushing tests of mild steel specimens were conducted. Then, two numerical models were designed to simulate the crushing behaviour of each specimen: one considering the boundary geometrical imperfections (in order to examine their effect on the crashworthiness performance) and the other considering a perfect geometrical structure. Lastly, a numerical parametric study was carried out, where new series of tapered HG-tubes models were crushed. The varying parameter was the perimeter of the small base of the tube, while the perimeter of the large base, the wall thickness, and the axial length remained constant. Introducing the boundary geometrical imperfections into the numerical models did not essentially impact the energy absorption. The HG-tubes outperformed the tubes with square cross section but not the tubes with circular cross section in terms of energy absorption. [ABSTRACT FROM AUTHOR] more...

Hybrid tubular members consisting of a metal tube externally reinforced with carbon fibre have been shown to be efficient energy absorbers. Several studies have used filament winding techniques to fabricate hybrid tubes, principally with circular cross-sections. Filament winding allows for a wide range of discrete fibre orientations. The present study develops an analytical technique to predict the mean crushing force of hybrid square tubes with arbitrary metal tube material and arbitrary carbon fibre orientations. Initially, an experimental study of the quasi-static axial crushing of 40 hybrid square tubes with a variety of metals (steel, aluminium and stainless steel), and a variety of filament winding angles (45°, 67° and 90°) and plies, is described. Comparisons of filament wound tubes are made with previous studies by the author and co-workers of nominally identical hybrid tubes fabricated with the hand-layup method. Previous crushing mechanism theories of bonded metal-fibre square tubes are extended to consider the different metals and fibre orientations. Based on the observations in the experimental program, a new theory is developed for the case where the metal and fibre become unbonded, and is shown to compare well with the experimental data. The analytical model indicates that when the carbon fibre remains bonded to the metal throughout the crushing process, the mean crush load is on average 54% higher than when the fibre becomes unbonded. This indicates the importance of the metal-fibre bond for optimum performance of hybrid tubes. more...

In the present research, the axial crushing behaviors of foam-filled holed tube are investigated by performing quasi-static compression tests. The possible deformation modes are obtained. The experimental results show that the energy absorption performance of empty holed tube can be greatly enhanced by filling aluminum foam. Furthermore, a novel theoretical model for concertina mode of foam-filled holed tube is proposed based on super folding element method, and validated by present and previous experimental results. The interaction between the tube wall and foam filler, normalized mean crushing force and specific energy absorption are obtained theoretically and discussed in detail. [ABSTRACT FROM AUTHOR] more...

• The anisotropy, tension-compression asymmetry and differential hardening behavior of AA6061-T6 are experimentally investigated. • Axial crushing behaviors of AA6061-T6 thin-walled rectangular tube with circular hole geometric discontinuity are experimentally analyzed. • The axial crushing, oblique crushing and three-point bending of AA6061-T6 thin-walled rectangular tubes are numerically studied. • Differential hardening behavior is crucial for the simulation accuracy of energy absorption. In this study, the energy absorption characteristics and deformation modes of AA6061-T6 thin-walled rectangular tube are investigated experimentally and numerically under different crushing conditions, including axial crushing, three-point bending and oblique crushing. Mechanical tests are carried out on four specimens of uniaxial tension, uniaxial compression, shear and plane strain tension along different loading directions for AA6061-T6. Besides, the effect of differential hardening behavior on the energy absorption prediction of AA6061-T6 rectangular tubes is illustrated by comparing Lou2022, von Mises and SY2009 functions. The mechanical experiment results indicate that AA6061-T6 shows obvious anisotropy, differential hardening behavior and tension-compression asymmetry, and its plastic evolution is accurately characterized by the Lou2022 model. The axial crushing properties show that the AA6061-T6 thin-walled rectangular tube undergoes the progressive symmetrical folding deformation mode. The introduction of geometric discontinuity can obviously reduce the peak force and improve the crashworthiness performances under the axial load. The main crushing mode is bending with a small amount of indentation for three-point bending. Moreover, the three-point bending simulation shows that the Lou2022 function considering differential hardening behavior has the highest simulation accuracy. Three different oblique crushing simulations of 10 ∘ , 20 ∘ and 30 ∘ illustrate that the AA6061-T6 rectangular tube at 10 ∘ mainly occurs progressive folding deformation. while the other two oblique crushing angles undergo global buckling deformation. The total energy absorption at 10 ∘ is 1.87 and 2.43 times of that at 20 ∘ and 30 ∘ , respectively. The crushing force efficiency of 20 ∘ and 30 ∘ is 41.28 % and 31.8 % lower than that of 10 ∘ , respectively. A comprehensive understanding of the energy absorption performance of AA6061-T6 thin-walled rectangular tube under different crushing conditions is helpful to determine its position and shape as a vehicle safety structure, and to exert its optimal plastic deformation potential to dissipate the collision energy and ensure passenger safety. [Display omitted] [ABSTRACT FROM AUTHOR] more...

This investigation focuses on the interaction effect during the quasi-static axial crushing of circular and square thin-walled aluminium extrusions filled with polymeric foam or cork. The increment in the absorbed energy due to interactions between materials was assessed using a validated numerical model calibrated with experimental material data. Simulations were run with variable cross-section dimensions, thickness, and foam density. The results were used to adjust the parameters of design formulas to predict the average crush forces of foam- and cork-filled thin-walled tubes. The analysis of the energy dissipation per unit volume revealed that the highest increments due to the interaction between materials appeared in the foam-filled square extrusions. Energy dissipation increased with higher density foams for both cross-sections due to a stronger constraint of the aluminium walls, and thus a reduction of the folding length. Thinner tube walls also delivered a higher improvement in the energy dissipation per unit volume than those with thicker walls. The contribution of friction was also quantified and investigated. [ABSTRACT FROM AUTHOR] more...

As an energy absorber, circular tube with wide external circumferential grooves has excellent mechanical properties, and it has been defined as 'Type B' grooved tube. In the present work, a novel analytical model of 'Type B' grooved tube is proposed by considering the curvature of plastic hinge. In addition, the fitting equation of the maximum angular displacement of a thin-walled section is obtained. The theoretical methodology indicated that both the total energy absorption and mean crushing force depend on the geometric ratios R/h and h/t. Based on axisymmetric assumption, a numerical model is established and the corresponding results are validated by a previous research. The theoretical and simulation results of total energy absorption and mean crushing force are compared with research results of previous studies. The conclusion shows that the present analytical model is more accurate to predict the energy absorption and mean crushing force of 'Type B' grooved tube under quasi-static condition. The energy absorption performance of 'Type B' grooved tube under quasi-static crushing can be improved by designing the thin-walled section as a stocky shape. Moreover, the model can also predict the response of 'Type B' grooved tube under dynamic condition when the strain rate sensitivity of material is introduced. [ABSTRACT FROM AUTHOR] more...

Metallic tubes are preferred in many different fields due to their energy absorbing efficiency. In order to increase the ability to absorb energy, foam filling by using different types of foam is still up to date. In this study, the energy absorbing capability of 6063-T5 aluminum tubes which were filled by using three different foam densities (60, 80 and 100 kg/m³) were investigated experimentally. Base tubes were filled by using three different foam filling models such as uniform density, functionally graded and sandwich model. In addition, in each foam filling models, different sample combinations were obtained by changing the thickness of the foam layers. The highest energy value absorbed in the uniform density foam filling model was obtained in the combination of 80 kg/m³ density foam, which is 37% higher than the base tube. Considering all specimen combinations, the increase in the absorbed energy value is between 18% and 43%, while the highest value was obtained in the sandwich model. In the examination of the test results, the specific energy absorption values of each specimen were also taken into consideration. The specific energy values for some sample combinations were lower than the base tube, while the highest value was obtained in the sandwich model with the value of 27.71 J/g which is about 11% higher compared to the base tube. In contrast, the specific energy absorption values of some specimens were lower than the base tube. [ABSTRACT FROM AUTHOR] more...

To design crash structures for disruptive aircraft designs, it is required to have fast and accurate methods that can predict crashworthiness of aircraft structures early in the design phase. Axial crushing is one of the key energy absorbing mechanisms during a crash event. In this study, various analytical models proposed for calculation of mean crushing force for thin-walled tubular structures are compared with a database of numerical and experimental values to ascertain their accuracy. Improvements to some of the models have also been proposed. Finally a generalized model based on the studied and improved analytical models for prediction of mean crushing force for closed section thin-walled tubular structures is introduced. The generalized model demonstrates high accuracy when compared against experimental/numerical dataset as evidenced by a high coefficient of determination (R 2) value of 0.97 and can therefore be used to estimate the mean crushing force for closed-section thin-walled metallic tubular structures with various cross-sectional shapes and crushing modes early in the design phase. • Evaluation of analytical models to predict mean crushing force • Analysis of both extensional and inextensional analytical crushing models. • Use of numerical and experimental dataset to improve existing analytical models. • Generalized expression for predicting mean crushing force [ABSTRACT FROM AUTHOR] more...

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