泡沫铝填充金属薄壁圆管的实验和理论研究

利用实验研究与理论分析相结合的方法研究了泡沫铝填充金属薄壁圆管在准静态侧向压缩下的力学响应.基于能量法,建立了泡沫铝填充圆管和金属薄壁圆管在侧向均匀压缩时的瞬时侧向力、平均侧向力和总吸能的理论公式.对泡沫铝填充管与金属薄壁圆管进行了准静态侧向压缩实验,并且将实验结果与理论公式进行了对比,结果表明理论预测值与实验结果吻合较好.基于建立的理论分析模型,研究了管的几何尺寸以及泡沫铝材料的密度对结构的瞬时侧向力、平均侧向力、总吸能和比吸能的影响.结果表明,在准静态侧向压缩下,泡沫铝填充管的总吸能大于对应的金属薄壁圆管;泡沫铝填充管的侧向压缩力和总吸能随管长度、壁厚和直径的增加而增大;当填充材料泡沫铝密度增大时,填充管的总吸能与侧向压缩力均增加.     

泡沫铝填充金属薄壁圆管侧向压缩的实验和理论

利用实验研究与理论分析相结合方法研究了泡沫铝填充金属薄壁圆管在准静态侧向压缩下的力学响应。基于能量法,建立了泡沫铝填充圆管和金属薄壁圆管在侧向均匀压缩时的瞬时侧向力、平均侧向力和总吸能的理论公式。对泡沫铝填充管与金属薄壁圆管进行了准静态侧向压缩实验,并且将实验结果与理论公式进行了对比,结果表明理论预测值与实验结果吻合较好。基于建立的理论分析模型,研究了管的几何尺寸以及泡沫铝材料的密度对结构的瞬时侧向力、平均侧向力、总吸能和比吸能的影响。结果表明,在准静态侧向压缩下,泡沫铝填充管的总吸能大于对应的金属薄壁圆管;泡沫铝填充管的侧向压缩力和总吸能随管长度、壁厚和直径的增加而增大;当填充材料泡沫铝密度增大时,填充管的总吸能与侧向压缩力均增加。     

低速冲击下泡沫金属填充薄壁圆管的弯曲行为

采用实验方法研究了低速冲击下泡沫金属填充薄壁圆管的弯曲行为,详细说明了实验方法和原 理。通过与准静态实验结果的比较发现,冲击加载使泡沫金属填充圆管跨中截面的局部压入变形增大,跨中 截面高度变小,结构下缘拉裂破坏延迟。由于结构的惯性效应,锤头总冲击力高于准静态加载时的对应值。     

泡沫铝填充薄壁圆管的三点弯曲实验的数值模拟

泡沫金属填充薄壁结构的应用日趋广泛,建立合理的数值计算模型对结构设计和工程应用非常重要.该文通过对泡沫铝填充薄壁铝合金圆管的三点弯曲实验的数值模拟,研究了它的力学行为.采用ABAQUS软件,建立了空管和泡沫铝全填充管的有限元模型,并对这两种结构在三点弯曲下的力学行为进行了数值模拟,所得结果与实验结果符合得较好.通过数值模拟分析了结构的承载机理和不同压头直径对结构承载能力的影响.此外,还研究了泡沫铝部分填充圆管的三点弯曲行为,分析了不同填充长度对结构承载能力的影响.     

带有圆弧形凹槽金属薄壁圆管抗撞性优化设计

在金属薄壁圆管的基础上,引入圆弧形凹槽诱导结构并以其为研究对象,建立以凹槽数量及其半径为优化参数,以比吸能和压溃力效率为评价指标的多目标优化模型。分析研究均布设置诱导凹槽对结构吸能、最大峰值压溃力及压溃力曲线平稳性的影响。采用有限元软件LS-DYNA得到不同几何参数模型的碰撞响应,结合径向基函数法构造近似函数,并采用理想点法进行优化设计,得出使结构最优时的凹槽数量和半径,从而得到了理想的诱导凹槽优化结构。     

闭孔泡沫铝动态材料参数的实验研究

泡沫金属在高速冲击下表现为变形局部化,采用传统的分离式Hopkinson杆技术进行动态实验测试可能存在问题。本文以动态、刚性-塑性硬化(D-R-PH)模型为理论基础,对闭孔泡沫铝开展Taylor-Hopkinson冲击实验,结合高速摄影技术和数字图像相关技术(DIC),获得了冲击速度的历史曲线。通过运用冲击波理论,提出了冲击速度与冲击时间的隐函数拟合方法,确定了动态初始压溃应力和应变硬化参数等两个动态材料参数。利用冲击端的应力历史曲线检验了结果的有效性,分析了动态材料参数对相对密度的敏感性,发现动态初始压溃应力和应变硬化参数均与相对密度近似呈幂函数关系。实验表明泡沫铝的应力-应变行为呈现明显的冲击速率敏感性。     

开孔泡沫铝填充圆管的准静态压缩行为

采用开孔结构泡沫铝填充到薄壁圆形铝管中,制备出开孔泡沫铝夹芯铝管,并进行压缩实验,研究了这种结构材料的压缩力学行为和变形特征以及材料的结构特征参数对压缩力学性能和能量吸收特性的影响。在压缩过程中,泡沫铝夹芯铝管的载荷-位移曲线呈现出弹性段、波动的屈服平台段和压实段3个阶段特征;铝管的径厚比及泡沫铝本身的参数和强度对填充管的屈服强度、平均压溃力和吸能特性均有着非常显著的影响。填充泡沫铝后铝管的压缩变形方式发生改变,管壁只发生向外翻折变形,产生的环状褶皱减少。     

薄壁管及其泡沫金属填充结构耐撞性的实验研究

对两种AA 6063T6铝合金薄壁空管(方/圆管)结构以及填充泡沫铝的5种不同几何截面的薄壁夹芯管(单方/圆管填充,双方/圆管填充,双方管四角填充结构)分别进行了准静态轴向压缩实验,研究了各种薄壁结构的变形模式和吸能性能,比较了反映不同结构耐撞性的各种参数,如比能量吸收和能量吸收效率因子等。同时,研究了各种填充结构的几何参数对结构耐撞性能的影响,发现填充结构内管的尺寸对结构的耐撞性影响显著。研究结果显示,圆管类型的结构平均压垮载荷、比质量能量吸收、单位行程能量吸收以及能量吸收效率因子都较方管类型结构高。泡沫填充单/双圆管结构由于其较高的压垮力效率和能量吸收效率,能够较平稳高效地吸能,作为耐撞性结构元件具有很大的优势。     

泡沫杆撞击刚性壁的动态压溃模型

针对泡沫杆撞击刚性壁的情形建立了2类动态压溃模型:一维冲击波模型和三维细观有限元模 型。以连续介质框架下的应力波理论为基础,并假定了刚性-非线性塑性硬化的加载和刚性卸载的本构关系, 建立了一维冲击波模型,给出了冲击波波后应变与冲击时间的隐式表达式。利用随机Voronoi技术构建了闭 孔泡沫金属结构的三维细观有限元模型,使用ABAQUS/Explicit有限元软件模拟了泡沫材料的动态压溃过 程,并基于最小二乘法计算局部变形梯度和局部应变得到了三维泡沫结构的应变场。通过理论解和数值解的 比较,发现该理论模型能够较好地预测泡沫金属杆撞击刚性壁的力学行为,得到了较为精确的结果。     

泡沫铝合金填充圆管三点弯曲实验研究

用实验方法研究了三种不同管壁厚度、两种跨径的泡沫铝合金填充圆管的三点弯曲力学性能,得到了泡沫铝合金填充管结构承载过程中的三种变形模式,即压入、压入弯曲和管壁下缘拉裂破坏。给出了空管和泡沫铝合金填充管的载荷位移曲线,并进行了比较。实验发现泡沫铝合金填充管结构的承载能力随泡沫铝合金密度的增大而增大,但破坏应变则随之减小。结构承载力的相对提高量随着管壁厚度的减小和跨径的增大而增大。此外,分析了泡沫铝合金提高填充管结构承载能力的机理。泡沫铝合金填充使管壁压入量和管截面抗弯刚度的损失显著减小,从而提高了结构的抗弯能力。     

泡沫铝夹芯双方管结构准静态轴压性能的实验研究

对几种泡沫铝夹芯方管结构的准静态轴压性能进行了实验研究。结果表明,较空管及泡沫铝夹芯单管结构,泡沫铝夹芯双管结构的承载能力及能量吸收效率明显得到增强。双管夹芯结构中外管撕裂模式的结构行程利用率和能量吸收效率高于相应的外管周期折叠模式。而泡沫铝四角填充方式提高了双管夹芯结构相同变形模式下的能量吸收效率和结构变形的稳定性。同时研究了内管管壁及材料强度对泡沫铝夹芯双管结构的影响。随着内管壁厚增大,双管夹芯结构的能量吸收效率提高,而内管材料强度影响不明显。     

A theoretical analysis for the dynamic axial crushing behaviour of aluminium foam-filled hat sections

A theoretical analysis was performed to predict the dynamic axial crushing behaviour of aluminium foam-filled top hat and double hat sections made from mild steel material. The deformation mode from the test results was used to create a deformation model for the theoretical analysis. According to the energy method and the superfolding element theory, the mean dynamic crushing loads of the aluminium foam-filled hat sections and the interactive effect between the aluminium foam and hat sections were theoretically predicted. The mean dynamic crushing loads and the interactive effect predicted by this theoretical analysis were in good agreement with the experimental results. The theoretical prediction results showed that the interactive effect was mainly from the aluminium foam.     

Aluminum foam-filled extrusions subjected to oblique loading: experimental and numerical study

The behavior of empty and foam-filled square thin-walled aluminum columns in alloy AA6060 subjected to quasi-static oblique loading was examined. Previous studies have shown that by introducing a load angle, the energy absorption decreases drastically compared to axial loading. One of the main objectives of the present investigation was to study the effect of introducing aluminum foam filler on the energy absorption. The square columns were clamped at one end and oblique load conditions were realized at the other end by applying a force with different angles to the centerline of the column. An experimental program was carried out where the main parameters were load angle, foam density and heat treatment of the extrusion material. Additionally, numerical analyses of the experiments were performed, mainly to verify a numerical model of the obliquely loaded foam-filled columns. The foam was modeled with the foam model of Deshpande and Fleck, together with a simple fracture criterion, which previously has been implemented as a user subroutine in LS-DYNA. The study shows that high-density aluminum foam filler increases the energy absorption considerably, but the specific energy absorption is lowered compared to the empty cross sections. Furthermore, the numerical analyses were able to predict the experimental results with reasonable accuracy.     

Partition energy absorption of axially crushed aluminum foam-filled hat sections

The “interaction effect” between aluminum foam and metal column that takes place when foam-filled hat sections (top-hats and double-hats) are axially crushed was investigated in this paper. Based on experimental examination, numerical simulation and analytical models, a systemic approach was developed to partition the energy absorption quantitatively into the foam filler component and the hat section component, and the relative contribution of each component to the overall interaction effect was therefore evaluated. Careful observation of the collapse profile found that the crushed foam filler could be further divided into two main energy-dissipation regions: densified region and extremely densified region. The volume reduction and volumetric strain of each region were empirically estimated. An analytical model pertinent to the collapse profile was thereafter proposed to find the more precise relationship between the volume reduction and volumetric strain of the foam filler. Combined the superfolding element model for hat sections with the current model according to the coupled method, each component energy absorption was subsequently derived, and the influence of some controlling factors was discussed. According to the finite element analysis and the theoretical modeling, when filled with foam, energy absorption was found to be increased both in the hat section and the foam filler, whereas the latter contributes predominantly to the interaction effect. The formation of the extremely densified region in the foam filler accounts for this effect.     

填充式泡沫铝防护结构的弹道极限

为了探索泡沫材料在空间防护上的应用,结合实验和数值模拟,绘制了弹速0.5~7.0km/s范围 内填充式泡沫铝防护结构的弹道极限曲线,并与Whipple结构进行了比较。结果表明:填充式泡沫铝防护结 构的防护性能优于同等面密度、总厚度的Whipple结构;孔隙率对填充式泡沫铝防护结构防护性能影响较小。     

Energy absorption of foam-filled circular tubes with braided composite walls

Braided glass-fibre/epoxy circular tubes with polymer foam cores are loaded in tension and in compression, and the energy of deformation is measured. Theoretical models of tube deformation are developed, and are used to predict the energy absorption as a function of tube wall strength, the ratio of tube wall thickness to tube diameter, and the density of the foam. The energy per unit mass and energy per unit volume are optimised with respect to the relative density and geometry. It is found that foam-filled braided circular tubes exhibit promising energy absorbing characteristics, due to a combination of energy absorption by the polymeric foam core and by the glass/epoxy braided tube.     

内部填充泡沫铝的柱壳力学响应数值模拟

针对泡沫铝及其填充圆柱壳的变形模式复杂、理论分析困难的问题,在分析泡沫金属唯象本构模型的基础上,用Bilkhu/Dubois可压缩泡沫模型描述泡沫铝的力学行为,用随机几何缺陷描述结构的可能缺陷形式,采用有限元法对内部填充泡沫铝的圆柱壳结构在轴向载荷作用下的静、动态力学响应进行了数值模拟.数值模拟结果与实验结果较一致,表...