诱导结构对泡沫铝填充薄壁方管轴向压溃特性影响的研究

建立了泡沫铝填充薄壁方管的有限元模型,利用试验对泡沫铝填充薄壁方管的有限元模型的准确性进行了验证。研究了诱导结构的类型和数量对泡沫铝填充薄壁方管的轴向压溃变形模式、初始峰值力、压溃力效率和能量吸收能力的影响,结果表明:设计诱导结构可以提高能量吸收能力、减小初始峰值力、增加压溃力效率,甚至可以改变压溃变形模式。沿薄壁方管的轴向方向合理地增加诱导结构的数量,可以进一步的减小初始峰值力、增加压溃力效率、提高结构的能量吸收能力。通过等级评价方法,确定沿薄壁方管的轴向方向设计4组诱导四角方孔可以使泡沫铝填充薄壁方管获得最佳的综合吸能特性。     

石膏型渗流制备泡沫铝填充圆管压缩行为研究

采用石膏型渗流制备开孔泡沫铝并填充到薄壁圆管,制成泡沫铝夹心管.通过准静态压缩试验研究了泡沫铝夹心管的压缩行为.结果表明:采用石膏型渗流法制备的泡沫铝孔隙率在85％左右,其压缩变形阶段可分为弹性段、塑性平台段和致密化段;空心圆管的压缩行为与其本身的结构参数有关;泡沫铝夹心管的力学性能与吸能能力比空心圆管和泡沫铝有了一定...     

颗粒增强铝合金基泡沫铝材料压缩性能的研究

利用熔体发泡法制备了颗粒增强铝合金基闭孔泡沫铝,进行了准静态压缩和动态压缩实验,并且与铝合金基泡沫铝的相关性能进行了比较.研究了不同相对密度的泡沫铝准静态压缩和动态压缩性能.添加颗粒能增强基体合金性能,改善泡沫压缩效果.结果表明,在动态压缩和准静态压缩中,随着密度增加,颗粒增强基泡沫铝的平台应力和弹性模量逐渐增大;动态情形下的能量吸收能力要高于准静态情形下的能量吸收能力.向熔体中添加适当比例的粉煤灰颗粒可产生显著的基体增强效果,有效提高泡沫铝的压缩性能.     

泡沫铝填充管的研究进展

泡沫铝填充管是在一个或多个不同横截面形状的薄壁金属管内填充泡沫铝而形成的一种结构功能一体化材料。泡沫铝的填充不仅提高了薄壁金属管的轴向压缩性能和抗弯曲性能,也避免了泡沫铝本身强度不高的劣势。从泡沫铝填充管的制备、结构及性能方面综述了其研究现状,从泡沫铝单管、双管与多管填充的角度分析了结构对泡沫铝填充管压缩和弯曲性能的影响。单管填充泡沫铝改变了薄壁管压缩及弯曲的失效形式,提高了薄壁管的吸能性;双管填充泡沫铝的内管多数以同心管形式排列,在管内部所填充的泡沫铝支撑的基础上,内管进一步支撑起泡沫铝填充管的承载和吸能作用,其压缩及弯曲性能较单管填充更为突出;多管填充泡沫铝在双管基础上进行拓展,可以同心或并列排布,对薄壁管性能的提升各有不同,平行排列的多管结构能量吸收效率高于泡沫铝填充单管,但低于相应的薄壁空管结构。泡沫铝填充管的制备技术通常是分别制取泡沫铝和管材再进行填充,尽管过于单一且工艺复杂,但由于其具有优异的承载和吸能能力,仍然在交通运输、航空航天等领域极具应用潜力。     

填充泡沫铝的多层铝管动态压溃吸能特性研究

采用数值模拟的方法研究和分析了无填充物的多层铝管结构的吸能特性,结果发现多层铝管相比单层铝管,不但具有较大的吸能量,而且还具有较高的比吸能率;在此基础上,设计了不同层数的多层管泡沫铝填充结构,研究发现泡沫铝不但受轴向压溃变形,同时也受到了铝管层之间的相互作用力使其在径向发生了变形;之后对多层管填充3种不同密度的泡沫铝,采用变参分析的方法研究了多层管层数和泡沫铝密度对整个结构吸能特性的影响;研究结果表明:填充泡沫铝的多层管,随着层数的增加,其比吸能率和吸能量也随之有所增加,随着泡沫铝密度的提高,比吸能率的提高量开始下降,但仍高于填充相同泡沫铝的单层管。     

高速冲击泡沫铝填充管的瞬态分析

泡沫铝具有减震和吸收冲击能量的良好特性。但由于泡沫铝自身强度较低,单独作为承载和吸能构件实用意义不大。将泡沫铝作为填充材料能充分发挥泡沫铝的优良性能。采用数值模拟方法研究低密度Duocel泡沫铝填充薄壁方钛管和圆钛管在30m/s的匀速冲击载荷作用下的瞬态吸能特性。提出柱壳比(R)作为比较不同截面形状的泡沫铝填充结构的依据。研究发现泡沫铝填充方钛管的比吸能为ES(F+P)A=0.438J;圆钛管的比吸能为EC(F+P)A=0.344J。泡沫铝填充方钛管的吸能效果好于圆钛管,前者是后者的1.273倍。在相互作用和影响下,泡沫铝柱和管的变形模式和力学性能都发生了较大的改变,被泡沫铝填充的方管的屈曲波长变短,圆管则与之相反。粘合后,泡沫铝柱和管具有类似的力—位移曲线和相似的力学性质。     

CFRP复合材料层合圆筒轴向压缩试验与数值模拟

制备了端部带有加强箍的三种不同高度的碳纤维增强复合材料(CFRP)厚壁圆筒和层合板试样;对圆筒试样进行了准静态轴向压缩性能实验和速度在7.67～12.01 m·s-1范围内的轴向冲击压缩试验,分别研究了长径比、冲击速率、端部加强等因素对轴向抗压强度、失效模式的影响规律;对CFRP层合板试样进行了不同应变率下的面内压缩试验.运用ANSYS/LS-DYNA软件对落锤加载下复合材料圆筒的响应过程进行了数值模拟.结果表明:采用端部加强方式不仅可以避免CFRP圆筒出现端部“开花式”渐进破坏的失效模式,而且能有效提高轴向抗压强度;层合板和圆筒试样的抗压强度均具有明显的正应变率效应;数值模拟结果与实验数据具有较好的一致性.     

泡沫铝夹芯双管构件横向压缩吸能性能研究

目的 研究截面构型及几何参数对泡沫铝夹芯双管结构在横向载荷作用下变形失效机制和吸能性能的影响。方法 运用有限元软件Abaqus/Explicit对泡沫铝夹芯双管构件受横向载荷作用进行数值仿真分析。结果 泡沫铝夹芯双管构件在横向压缩过程中表现出3个阶段:初始压缩阶段、塑性变形阶段和致密化阶段,并发现外方内圆双管夹芯结构的耐撞性能显著强于双方管夹芯结构。随着外管径的增大、内管径的减小,外方内圆双管夹芯结构的承载力和吸能能力越高;内管壁厚的增加使外方内圆双管夹芯结构的能量吸收、比吸能、平均压溃载荷和压溃力效率均表现出增大趋势。结论 泡沫铝芯材的变形失效模式受内管截面形状的影响,与传统双方管夹芯结构相比,外方内圆双管夹芯结构是一种更优秀的吸能构件,在横向碰撞安全防护中展现出更大的应用潜力。通过增加内外管间距和内管壁厚,可以提高外方内圆双管夹芯结构的吸能性能。     

CFRP复合材料层合圆筒轴向压缩试验与数值模拟

制备了端部带有加强箍的三种不同高度的碳纤维增强复合材料(CFRP)厚壁圆筒和层合板试样; 对圆筒试样进行了准静态轴向压缩性能实验和速度在7.67~12.01 m·s^-1范围内的轴向冲击压缩试验, 分别研究了长径比、 冲击速率、 端部加强等因素对轴向抗压强度、 失效模式的影响规律; 对CFRP层合板试样进行了不同应变率下的面内压缩试验。运用ANSYS/LS-DYNA软件对落锤加载下复合材料圆筒的响应过程进行了数值模拟。结果表明: 采用端部加强方式不仅可以避免CFRP圆筒出现端部\"开花式\"渐进破坏的失效模式, 而且能有效提高轴向抗压强度; 层合板和圆筒试样的抗压强度均具有明显的正应变率效应; 数值模拟结果与实验数据具有较好的一致性。     

具有诱导结构的铝合金薄壁方管轴向压缩吸能性能试验研究

该文提出了三种新型的诱导结构设计方案来降低薄壁方管结构在轴向载荷作用下的初始屈曲载荷峰值。诱导结构设计在方管的加载端,在压缩开始的时候起作用,并且不会显著影响结构在正常工作时的强度和刚度。利用AA 6063 T6 铝合金薄壁方管进行了一系列准静态和动态试验来研究了具有诱导结构的方管在轴向压缩时的能量吸收性能,给出了完整薄壁铝方管和具有诱导结构的薄壁铝方管的载荷位移曲线,并进行了比较。实验发现,三种诱导结构均可有效降低屈曲时的初始载荷峰值、提高方管承载吸能平稳性。     

Experimental studies on the quasi-static bending behavior of double square tubes filled with aluminum foam

Quasi-static experiments were performed on empty tubes and aluminum foam-filled single and double tubes to study the effects of different filler arrangements on their three-point bending behavior. The load-carrying capacity and energy absorption of different structures are compared. The results confirm the advantage of the foam-filled structures. In particular, the double tube structure with aluminum foam filler enhances the load-carrying capacity, crashworthiness, and total and specific energy absorptions of the structure, in comparison with the foam-filled single tube. It was also found that increasing the wall thickness of the inner tube improves the performance of the structure within the experimental range, and adhesion between foam and tube has a negative effect.     

Dynamic bending response of double cylindrical tubes filled with aluminum foam

The dynamic three-point bending behavior of double cylindrical tubes filled with closed-cell aluminum foam core was studied experimentally and numerically. It is found that the deformation mode of this new structure under impact loading is different to that under quasi-static loading. The load carrying capacity of the structure subjected to impact remains at the level of that in the quasi-static situation. Compared with traditional foam-filled single tubes, the specific energy absorption efficiency of this new structure is much higher, and that of both foam-filled structures in the dynamic situation are higher than that in static situation. A preliminary experimental study on the effect of profiles and span of the structure were performed, and the result shows that these parameters affect the structure together. Numerical simulation of the bending behavior was also executed with the explicit finite element method. The mechanism of the dynamic response is revealed by comparison of the maximum strain history in the simulation.     

Crushing of axially compressed steel tubes filled with aluminium foam

Summary This study, with the emphasis on experiments, investigates the applicability of aluminium foam as filler material in tubes made of mild steel having square or circular cross sections, which are crushed axially at low loading velocities. In addition to the experiments finite element studies are performed to simulate the crushing behaviour of the tested square tubes, were a crushable foam material model is shown to be suitable for describing the inelastic response of aluminium foam with respect to the considered problems. The experimental results for the square tubes reveal efficiency improvements with respect to energy absorption of up to 60%, resulting from changed buckling modes of the tubes and energy dissipation during the compression of the foam material itself. The principal features as well as the changes of the crushing process due to filling can also be studied by the numerical simulations. A global failure mechanism due to a high foam density can be observed for filled circular tubes. Aluminium foam is shown to be a suitable material for filling thin-walled tubular steel structures, holding the potential of enhancing the energy absorption capacity considerably, provided the plastic buckling remains characterized by local modes.Dedicated to Prof. Dr. Dr. h. c. Franz Ziegler on the occasion of his 60th birthday     

Electrical,mechanical and thermal properties of polyvinyl chloride composites filled with aluminum powder

In this work, the electrical, mechanical and thermal properties of polyvinyl chloride (PVC) composites filled with different content of aluminum powder varying from 0 to 40 wt.% have been prepared. The dielectric properties of these composites were investigated in the frequency range 100 Hz–100 kHz at temperature range from 30 to 98 °C. The percolation threshold concentration, which is the concentration after which the conductivity increases many orders of magnitude with very little increase in the filler content for PVC/Al composites depends upon the measuring temperature, whether it is below or above the glass transition of the polymer matrix. The highest value of the electrical conductivity, σ, of the composites was found to be in the order of 10⁻⁸ S cm⁻¹, this value recommend such composites to be used in electrostatic dissipation applications as the range of conductivity for such application should be in the range of 10⁻⁵–10⁻⁹ S cm⁻¹.     

Experimental investigation of interaction effects in foam-filled thin-walled aluminum tubes

The interaction coefficients of polystyrene foam filling of thin-walled aluminum cylindrical tubes were investigated experimentally through compression testing of partially foam-filled tubes with and without adhesive. The experimental load-displacement curves and observation of the crushed sections of filled tubes have shown that partial foam filling reduced the fold length and hence increased the average crushing loads of tubes, proving the interaction effect between tube wall and filler. The interaction coefficients for the partial foam filling were further calculated to be in the level and/or higher than that of the foam plateau load of transverse direction.     

短纤维对泡沫铝压缩力学性能与吸能特性的影响研究

为探索闭孔泡沫铝加入短纤维后的力学性能和吸能特性变化规律.利用熔体发泡法在铝熔体中加入短碳纤维后制作得到纤维增强泡沫铝,通过万能材料试验机和高速液压伺服材料试验机在常温下分别对泡沫铝、纤维增强泡沫铝进行准静态和中应变率下(0.001～100s-1)的动态力学性能测试,分析了纤维长度、纤维含量对泡沫铝力学性能和吸能特性变...     

Axial crushing of hollow and foam filled tubes: An overview

Herein, a detailed review of the past studies carried out on crushing and energy absorption behaviour of hollow and foam filled tubes under axial compression is presented. Importance of such investigation is discussed for understanding the research need and to develop suitable alternatives. The focus of review is the deformation mechanism and energy absorption of hollow circular and square tubes, foam filled circular and square tubes notably. Comprehensive review on the various deformation modes for these tubes under axial impact load and effect of foam filling is presented. The review includes the various parameters affecting the peak load and energy absorption. Although various other forms of energy absorbing materials and structures exist such as composites, multi-wall tubes and honeycombs, these are not within the scope of present review. This paper intends to provide assistance in design and development of empty and foam filled tubes as effective energy absorbers. Further, this paper provides the necessary information for designers to understand the deformation of such tubes.     

Design and manufacturing of anti-intrusion bars made of aluminium foam filled tubes

The role of an anti-intrusion bar for automotive use is to absorb the kinetic energy of the colliding vehicles that is partially converted into internal work of the members involved in the crash. The aim of this paper is to investigate the performances of anti-intrusion bars, made by tubes filled with aluminium foams. The reason for using a cellular material as a filler deals with its capacity to absorb energy during plastic deformation, while being lightweight. The study is mainly conducted by evaluating some key technical issues of the manufacturing problem and by running experimental and numerical analyses. The evaluation of materials and shapes of the closed sections to be filled is made in the perspective of a car manufacturer (production costs, weight reduction, space availability in a car door, etc.). Experimentally, foams are produced starting from an industrial aluminium precursor with a TiH₂ blowing agent. Empty and foam filled tubes are tested in three point bending, in order to evaluate their performances in terms of several performance parameters. Different manufacturing conditions, geometries and tube materials are investigated. The option of using hydroformed tubes, with non constant cross section, for the production of foam filled side structures id also discussed.     

Crashworthy characteristics of axially statically compressed thin-walled square CFRP composite tubes: experimental

In this paper the results of experimental works pertaining to the crash behaviour, collapse modes and crashworthiness characteristics of carbon fibre reinforced plastic (CFRP) tubes that were subjected to static axial compressive loading are presented in detail. The tested specimens were featured by a material combination of carbon fibres in the form of reinforcing woven fabric in thermosetting epoxy resin, and they were cut at various lengths from three CFRP tubes of the same square cross-section but different thickness, laminate stacking sequence and fibre volume content. CFRP tubes were compressed in a hydraulic press of 1000 kN loading capacity at very low-strain rate typical for static testing. The influence of the most important specimen geometric features such as the tube axial length, aspect ratio and wall thickness on the compressive response and collapse modes of the tested tubes is thoroughly analysed. In addition, the effect of the laminate material properties such as the fibre volume content and stacking sequence on the energy absorbing capability of the thin-wall tubes is also examined. Particular attention is paid on the analysis of the mechanics of the tube axial collapse modes from macroscopic and microscopic point of view, emphasizing on the mechanisms related to the crash energy absorption during the compression of the composite tubes.