Energy absorption of an axially crushed square tube with a buckling initiator

Axially crushed thin-walled square tubes have been widely used as energy absorbers because of their high specific energy absorption capacity and long stroke. However, they render extremely high initial peak forces which may cause serious injury or damage to the people or structures being protected. This paper proposes a novel idea that by installing a buckling initiator near the impact end which is composed of a pre-hit column and pulling strips, the initial peak force of the square tube could be greatly reduced while its deformation mode and excellent energy absorption are retained. Both experimental and numerical investigations are conducted on aluminum alloy square tubes. The peak force, mean force and half-length of a fold of the tested specimens are examined. The results show that the mean crushing force and deformation mode are not affected by the buckling initiator, while the reduction of the peak force strongly depends on the pre-hit height. It is also found that the buckling initiator can ensure the deformation more stable and uniform. Finally, a simplified analytical model is developed to study the relationship between the reduction of the peak force and the geometric imperfections; and the model can successfully predict the effectiveness of the buckling initiator.     

Crushing analysis and multiobjective crashworthiness optimization of honeycomb-filled single and bitubular polygonal tubes

Honeycomb-filled tubes have recently gained attention for their enhanced energy absorption capacity. This paper firstly investigates the energy absorption characteristics of honeycomb-filled single and bitubular polygonal tubes (HSBPT) by nonlinear finite element analysis through LS-DYNA. By employing a six-level judgement method, we find that both of the honeycomb-filled single and honeycomb-filled bitubular tubes with enneagonal configuration have very excellent energy absorption characteristics among the considered cases. Next, the HSBPTs with enneagonal configuration are optimized by adopting multiobjective particle swarm optimization (MOPSO) algorithm to achieve maximum specific energy absorption (SEA) capacity and minimum peak crushing force (PCF). During the process of multiobjective optimization design (MOD), accurate metamodels of SEA and PCF of the HSBPTs with enneagonal configuration are established to reduce the computational cost of crash simulations by finite element method. Numerical experiments show that the quartic polynomial functions of SEA and PCF are the suitable metamodels for both honeycomb-filled single and bitubular enneagonal tubes.     

A numerical study on the quasi-static axial crush characteristics of square aluminum–composite hybrid tubes

In this paper, we describe a numerical investigation on the quasi-static axial crush performance of aluminum–composite hybrid tubes containing a filament-wound E-glass fiber-reinforced epoxy over-wrap around square aluminum tubes. The fiber orientation angle in the overwrap was varied between [±30°] and [90°] with respect to the tube’s axis. The quasi-static axial crush resistance of the hybrid tubes are compared in terms of the maximum load, mean crush load, crush energy and specific energy absorption. The deformation modes of these tubes are also described. An empirical equation is proposed for predicting the mean crush force of hybrid tubes.     

Lateral collapse of short‐length sandwich tubes compressed by different indenters and exposed to external constraints

In this paper, sandwich tube components which consist of thin‐walled circular tubes with aluminium foam core are proposed as energy absorption systems. The sandwich tubes were laterally crushed under quasi‐static loading conditions. The sandwich tubes were crushed under two types of indenters and exposed to three different types of external constraints. The collapsing behaviour and the energy absorption responses of these systems were investigated by nonlinear finite element analysis through ANSYS‐LS‐DYNA. Various indicators which describe the effectiveness of energy absorbing systems were used as a marker to compare the various systems. It was found that the sandwich tube systems compressed by cylindrical indenters particularly the unconstrained system and the system with inclined constraints offered a very desirable force‐deflection in which the force is almost constant in the post collapse stage. The employing of external constraints was noticed as a feasible method of increasing the SEA particularly when cylindrical indenter is used.     

Dynamic energy absorption characteristics of foam-filled conical tubes under oblique impact loading

This paper treats the crush behaviour and energy absorption response of foam-filled conical tubes subjected to oblique impact loading. Dynamic computer simulation techniques validated by experimental testing are used to carry out a parametric study of such devices. The study aims at quantifying the energy absorption of empty and foam-filled conical tubes under oblique impact loading, for variations in the load angle and geometry parameters of the tube. It is evident that foam-filled conical tubes are preferable as impact energy absorbers due to their ability to withstand oblique impact loads as effectively as axial impact loads. Furthermore, it is found that the energy absorption capacity of filled tubes is better maintained compared to that of empty tubes as the load orientation increases. The primary outcome of this study is design information for the use of foam-filled conical tubes as energy absorbers where oblique impact loading is expected.     

Energy Absorption Characteristics of Dual Phase Steel Tubes Under Static and Dynamic Loading

Abstract: Thin walled tubes are used as energy absorbing elements in automobile applications. The circular tube proves to be a popular energy absorber because it provides a reasonably constant operating force which is the prime characteristics of the energy absorber. Square and rectangular tubes are widely used in automobile structures as these cross sections are suitable for welding with other components in the structure and hence highly preferred. Advanced high strength steels can be utilised to absorb crash energy and minimise intrusion in the occupant zone. In this work circular, square and rectangular tubes made up of dual phase steel are tested in static and dynamic conditions. All the tubes are subjected to same amount of input impact energy but the specific energy absorption is higher in circular steel tubes. The results are compared with those for annealed tubes of same cross section. The effect of impact velocity is also studied by keeping the impact mass constant and varying the drop height. The experimental results are compared with the theoretical results and good agreement is found.     

蜂窝纸板异面动态冲击性能的实验分析

目的以六边形蜂窝纸板为研究对象,研究厚度对其异面冲击性能的影响。方法通过动态冲击实验来分析接触力、最大接触力、最大位移、最大应变、吸收能与单位厚度冲击能之间的关系,研究厚度为30,40,50和60 mm等4种蜂窝纸板的异面冲击力学性能。结果当冲击能一定时,随着蜂窝纸板厚度的增加,接触力逐渐减小,接触时间逐渐变长;当单位厚度冲击能一定时,厚度与最大位移和吸收能成正比例关系,厚度与接触力、最大接触力、最大应变成反比例关系;对于任一厚度的蜂窝纸板,最大接触力、最大位移、最大应变、吸收能随单位厚度冲击能的增加而增加,且与其呈线性关系。结论当冲击能相同时,不同厚度蜂窝纸板的吸收能几乎相同,可知蜂窝纸板吸收能量的能力与蜂窝纸板的厚度无关,取决于冲击能量的大小。     

圆-方异形截面复合材料管件物能量吸收机制

圆形截面复合材料管件物的能量吸收性能比方形截面管件物更加优越,但具有平整表面的方形管件物更容易与其他部件相装配,即方管在实际运用中更具优势。结合圆形与方形管件物的各自优势,以碳纤维为增强体,环氧树脂为基体,利用编织成型方法以及真空辅助树脂传递成型技术制备出编织角度为15°和60°的3类复合材料圆-方形管件物,编号为T15-15、T15-60及T60-60。通过准静态压缩实验研究了3类管件物的能量吸收性能,发现通过合理的编织角设计,可以利用周向纤维限制轴向中央裂纹的扩展,使复合材料内部更多的纤维发生断裂,从而提高纤维增强复合材料管件物的能量吸收性能。最终制备了集高能量吸收性能与易装配性于一身的圆-方异形截面复合材料管件物。     

An experimental investigation on crack effect on the mechanical behavior and energy absorption of thin-walled tubes

Energy absorption capacity and collapse of cylindrical and square thin-walled aluminum tubes with a crack shaped trigger under axial compression are studied in this paper. Furthermore, the effects of length, angle, location and situation of cracks on the mechanical behavior of tubes are investigated. The results of this research show that the cracks change the collapse processes and folding modes; this effects are greater for the cylindrical tubes; the maximum load is reduced between 4.92% and 31.33% for cylindrical and between 2.55% and 18.52% for square tubes; the cracks increase the crush force efficiency up to 67.03% and 31.06%, and absorbed energy up to 30.45% and 30.16% for cylindrical and square tubes, respectively. The maximum load for all of the cracked tubes is less than that of intact tubes and increasing the crack angle from 0° to 45° decreases the maximum load and from 45° to 60° increases it. Finally, parallel cracks are more effective than perpendicular cracks.     

Nonlinear finite element analysis of axially crushed cotton fibre composite corrugated tubes

It is proven experimentally that introducing corrugation along a shell generator together with a proper advanced composite material will enhance the crashworthiness performance of energy device units. This is because corrugation along the shell generator will force the initial crushing to occur at a predetermined region along the tube generator. On the other hand, a proper composite material offers vast potential for optimally tailoring a design to meet crashworthiness performance requirements. In this paper, the energy absorption characteristics of cotton fibre/propylene corrugated tubes are numerically studied. Finite element simulation using ABAQUS/Explicit was carried out to examine the effects of parametric modifications on the tube’s energy absorption capability. Results showed that the tube’s energy absorption capability was affected significantly by varying the number of corrugation and aspect ratios. It is found that as the number of corrugations increases, the amount of absorbed energy significantly increases.     

密度对聚丙烯泡沫材料动态冲击性能的影响

目的 以聚丙烯材料为研究对象,研究密度对其动态冲击性能的影响。方法 对4种不同密度的聚丙烯材料进行动态压缩试验,分析接触力、位移和应变以及吸收能、比吸能的变化,从而研究动态条件下不同密度的聚丙烯材料的动态冲击性能。结果 当密度一定时,最大接触力、最大位移、最大应变、比吸能随冲击能的增大而增大。当冲击能一定时,最大接触力随密度的增大而增大,最大位移、最大应变、比吸能随密度的增大而减小。结论 考虑到轻量化以及成本因素,在安全范围内,选择缓冲材料时可以选择密度较小的聚丙烯材料。     

薄壁圆锥管轴向压缩吸能特性研究

研究薄壁圆锥管轴向压缩吸能特性有助于其合理广泛应用于抗冲击、抗振动结构中。轴向倾角是使得圆锥管轴向压缩性能有别于直管的主要因素。当轴向倾角小于临界角度时,圆锥管平均轴向压缩力随倾角增加而变大但最大初始轴力会线性减小;吸能稳定因子随倾角增加而提高,但是比吸能却相应非线性降低。圆锥管在轴向压缩时过程中存在三种典型变形模式,分别为“钻石-堆叠”模式,“钻石-嵌套”模式及“环形-嵌套”模式,通过对“环形-嵌套”模式变形过程的观测及变形机理分析,建立了相应的理论模型,基于该理论模型给出了圆锥管“环形-嵌套”模式变形时吸能特性的预测方法。     

一种薄壁吸能结构的设计优化

研究了一种薄壁结构在耐撞指标下的轴向冲击吸能特性。采用非线性有限元软件ABAQUS对结构的冲击过程进行仿真,并结合径向基函数法(RBF),根据耐撞性指标优化了这种吸能结构的截面,得到了较为理想的结构形式。数值结果表明采用该方法可以精确地确定优化参数,使结构比吸能(Es)得到明显提高。     

Crushing analysis and multi-objective optimization design for bionic thin-walled structure

Thin-walled structure has gained increasing attention and been widely used in the field of mechanical engineering due to their extraordinary energy absorption capacity and light weight. In this paper, we introduced a new energy absorbed structure named as bionic thin-walled structure (BTS) based on the structural characteristics of horsetails. In this study, six kinds of BTSs with different cross-sectional configurations under lateral loading conditions were investigated using nonlinear finite element method through LS-DYNA. According to the numerical results, it can be found that the cell number, inner wall diameter and wall thickness of the BTS had significant effect on the crashworthiness of the structure. In order to obtain the optimal design among the six kinds of BTSs, the six BTSs were optimized using a metamodel-based multi-objective optimization method which was developed by employing polynomial regression (PR) metamodel and multi-objective particle swarm optimization (MOPSO) algorithm. In the optimization process, we aimed to achieve maximum value of specific energy absorption (SEA) and minimum value of maximum impact force (MIF). Meanwhile, we also optimized the traditional thin-walled structures, i.e., the circular and square tubes. Based on the comparison of the Pareto fronts obtained by the multi-objective optimizations, we found that the crashworthiness of the BTSs was better than that of the circular and square tubes and the best BTS among the six kinds of BTSs was different when the limit of MIF was different. And, the optimal designs of the BTSs were found to have excellent energy absorption capacity under lateral impact and could be used in the future vehicle body.     

内含气体对蜂窝纸板异面动态冲击性能的影响

目的以六边形蜂窝纸板为对象,研究内含气体对其异面冲击性能的影响。方法通过动态冲击实验分析内含气体对接触力、最大接触力、最大位移、最大应变和吸收能的影响,得出不同孔隙率时,蜂窝纸板的接触力-时间曲线,最大接触力、最大位移、最大应变、吸收能与冲击能曲线和吸收能-孔隙率曲线。结果在给定冲击能的情况下,最大接触力与吸收能随着孔隙率的增大而减小,最大位移及最大应变随着孔隙率的增大而增大。在孔隙率一定时,最大接触力、最大位移、最大应变和吸收能随冲击能线性增大。此外,冲击能越大,接触力达到峰值的时间越短,接触持续时间越长。结论在动态冲击实验中,内含气体使蜂窝纸板吸收冲击能的能力明显增强,并且当冲击能一定时,孔隙率越大,蜂窝纸板越容易被压变形,吸收能越少。     

Crushing response of foam-filled conical tubes under quasi-static axial loading

Foam-filled thin-walled tubes are considered to be desirable energy absorbers under axial loading due to their higher energy absorption compared with empty tubes. This paper treats the axial crushing and energy absorption response of foam-filled conical tubes under quasi-static axial loading, using non-linear finite element models. Influence of important parameters such as wall thickness, semi-apical angle and density of foam filler was investigated and the results highlight the advantages of using foam-filled conical tubes as energy absorber. Results also indicate that the crush and energy absorption performances of conical tubes are significantly enhanced by foam filling. The primary outcome of the study is new research information and development of empirical relations which will facilitate the design of foam-filled conical tubes as energy absorbers in impact applications.     

Numerical Study on Hybrid Tubes Subjected to Static and Dynamic Loading

The commercial finite element program LS-DYNA was employed to evaluate the response and energy absorbing capacity of cylindrical metal tubes that are externally wrapped with composite. The numerical simulation elucidated the crushing behaviors of these tubes under both quasi-static compression and axial dynamic impact loading. The effects of composite wall thickness, loading conditions and fiber ply orientation were examined. The stress–strain curves under different strain rates were used to determine the dynamic impact of strain rate effects on the metal. The results were compared with those of a simplified analytical model and the mean crushing force thus predicted agreed closely with the numerical simulations. The numerical results demonstrate that a wrapped composite can be utilized effectively to enhance the crushing characteristics and energy absorbing capacity of the tubes. Increasing the thickness of the composite increases the mean force and the specific energy absorption under both static and dynamic crushing. The ply pattern affects the energy absorption capacity and the failure mode of the metal tube and the composite material property is also significant in determining energy absorption efficiency.     

The Effects of Triggering Mechanisms on the Energy Absorption Capability of Circular Jute/Epoxy Composite Tubes under Quasi-Static Axial Loading

The usage of composite materials have been improving over the years due to its superior mechanical properties such as high tensile strength, high energy absorption capability, and corrosion resistance. In this present study, the energy absorption capability of circular jute/epoxy composite tubes were tested and evaluated. To induce the progressive crushing of the composite tubes, four different types of triggering mechanisms were used which were the non-trigger, single chamfered trigger, double chamfered trigger and tulip trigger. Quasi-static axial loading test was carried out to understand the deformation patterns and the load-displacement characteristics for each composite tube. Besides that, the influence of energy absorption, crush force efficiency, peak load, mean load and load-displacement history were examined and discussed. The primary results displayed a significant influence on the energy absorption capability provided that stable progressive crushing occurred mostly in the triggered tubes compared to the non-triggered tubes. Overall, the tulip trigger configuration attributed the highest energy absorption.     

泡沫填充多边形单锥管与双锥管斜向加载下耐撞性分析

锥形泡沫填充结构结合了泡沫填充结构与锥形结构的优势,具有优异的吸能性和抵抗失稳变形的能力。研究了具有不同横截面的泡沫填充多边形单锥管(FSPTTs)与泡沫填充多边形双锥管(FBPTTs)在四种冲击角度下的耐撞性。采用多准则评估方法(COPRAS)对不同横截面的泡沫填充单锥管与泡沫填充双锥管的综合耐撞性进行了评估。评估表明:综合考虑多种冲击角度时,圆形截面泡沫填充单锥管较其他截面泡沫填充单锥管具有更好的耐撞性;圆形截面泡沫填充双锥管较其他截面泡沫填充双锥管具有更好的耐撞性。最后,针对圆形截面泡沫填充单锥管与圆形截面泡沫填充双锥管,以最大比吸能和最小峰值力为目标,采用非支配遗传算法对这两种结构在四种冲击角度下进行了多目标优化。结果表明:当冲击角度从0°变化到10°时,两种结构的Pareto曲线变化不大,而当冲击角度从10°变化到30°时,冲击角度对Pareto曲线形状和位置有显著影响;在冲击角度为0°和10°时,圆形截面泡沫填充双锥管的耐撞性优于圆形截面泡沫填充单锥管,而在冲击角度为20°和30°时,圆形截面泡沫填充单锥管的耐撞性优于圆形截面泡沫填充双锥管。实际应用中,可以根据工程需要选择合适的结构。     

AZ31B镁合金挤压矩形管的轴向压溃试验与吸能特性分析

对AZ31B镁合金挤压矩形截面管进行准静态轴向压溃试验,研究其破坏模式和吸能特性,并探索管件长度、截面尺寸、倒角诱导因素等对吸能特性的影响。结果发现镁合金矩形管轴向压溃时存在两种破坏模式:整体破坏模式和渐进破坏模式,无倒角时管件发生整体破坏,而管端有倒角时主要从倒角端开始发生渐进破坏。渐进破坏模式有利于管件吸收能量。镁合金管件具有良好的吸能特性,其比吸能优于钢管、铝合金管和复合材料管。