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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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

Axial crushing behaviour of the polyurethane foam-filled aluminum cylindrical tubes with shallow spherical caps (combined thin-walled structures) is studied both experimentally and numerically. Non-linear dynamic finite element analyses were carried out to simulate the quasi-static tests. Satisfactory agreements were generally achieved between the finite element model and experimental deformed shapes, load–displacements, fold lengths and specific energy absorptions. Influence of important parameters such as semi-apical angle, length of cylindrical and spherical caps, diameter and density of foam filler was discussed and the results highlight the advantages of using foam-filled shell of the combined geometry as energy absorber. [ABSTRACT FROM AUTHOR]

In this paper, crushing characteristics of small-sized conical tubes called miniature frusta under axial loading have been studied. Finite-element model is developed using non-linear explicit code LS_DYNA to investigate the non-symmetrical fold patterns as well as material and geometrical non-linearity of frusta. Numerical simulation is first validated by confirming the results using experimental test data. Effects of shell thickness, semi-epical angle of cone and frusta's length on energy absorption characteristics are then studied by carrying out a parametric study. Based on the crushing parameters of numerous examples, a simplified analytical model as a meta-model for the mean crushing force of miniature frusta is presented using a Genetic Algorithm optimization for finding the meta-model coefficients. Miniature frusta show promising behaviour in lightweight design and crash analysis as their response results in low peak force and efficient-specific energy absorption. Obtained results from the developed meta-model showed good concurrence with finite elements method (FEM) model. [ABSTRACT FROM AUTHOR]

This paper presents the behaviour of empty and foam-filled aluminium alloy (AA6061-T6) tubes under dynamic axial loading. The influence of geometrical and various densities of fillers was investigated by employing a finite element code, LS-DYNA. The critical effective point for fillers of different densities is identified in a foam-filled tube based on a specific energy absorption value at which the weight effectiveness of a foam-filled tube exceeds that of the empty tube. The combination of an aluminium tube and an aluminium foam filler successfully induced significant increase in specific energy absorption, proving that the assessment of critical effective point is vital in identifying proper combination of tube-filler on the effectiveness of foam-filled tubes. [ABSTRACT FROM AUTHOR]

This research deals with experimental and numerical axial quasi-static crash tests on end-capped cylindrical and conical tubes. Axial quasi-static crush tests have been generated for end-capped cylindrical and conical tubes. Furthermore, in order to gain more detailed knowledge about the crash process, finite element (FE) simulations of the experiments have been performed. The explicit FE code Abaqus/explicit was used and the results have been validated by experimental data. The elastic–plastic material model was used for the aluminium tubes. In terms of finding more efficient (higher energy absorption) and lighter crash absorbers particularly, the energy absorption, E, and specific energy absorption, SEA, have been considered. The influences of geometrical parameters of the tubes on their collapse response have also been investigated. Finally, a multiobjective optimisation method is used to find the tube geometry which has the maximum energy absorption and specific energy absorption. [ABSTRACT FROM PUBLISHER]