【作者】 刘伟明；

【导师】 程和法；

【作者基本信息】 合肥工业大学 ， 材料加工工程， 2009， 硕士

【摘要】 泡沫金属具有轻质、高比强度及优异的吸能特性等特点,以泡沫金属为填充材料制备而成的夹芯结构材料是一种新型的轻质的结构功能材料,其压缩和弯曲等力学行为及变形失效的形式和机理已经成为材料科学、力学等领域中的热点课题之一。本文采用渗流法制备开孔泡沫纯铝和铝硅合金,将其加工后填充到铝合金圆管和不锈钢方管中,制成开孔泡沫铝夹芯圆管及夹芯方管,分别进行压缩和弯曲实验,研究泡沫铝力学性能及结构参数对开孔泡沫铝夹芯圆管轴向压缩的力学性能和吸能特性的影响,以及对夹芯不锈钢方管的弯曲力学行为和变形特征的影响。所制备结构的主要参数为:泡沫铝的孔径为0.65~2.3mm,相对密度为0.399～0.524;夹芯圆管:径厚比为5~30.4;夹芯方管:t/b为0.012~0.032。首先,对开孔泡沫铝夹芯铝管进行准静态单轴向压缩实验,研究了泡沫铝夹芯圆管的压缩应力-应变行为和变形特征,并研究泡沫铝基体性能和孔径等特征参数以及夹芯管的结构特征参数对其压缩行为、力学性能和吸量特性的影响规律。结果表明: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三阶段特征;铝管的径厚比以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。由于泡沫铝与管壁间相互作用使得夹芯管的抗变形能力显著提高,且管壁的变形模式发生改变,管壁只发生向外翻折变形,并且所产生的环状褶皱减少。其次,对开孔泡沫铝夹芯不锈钢方管进行准静态三点弯曲实验,重点研究不锈钢方管的t/b比值,泡沫铝的结构参数以及泡沫铝的填充方式对夹芯方管弯曲行为及变形模式的影响规律。结果表明:填充泡沫铝后,由于泡沫铝的支持抑制作用,不锈钢方管的局部弯曲变形模式发生改变,管壁由空管时的单一褶皱变为夹芯方管的多重褶皱模式,形成更多的塑性铰,褶皱长度减小,显著提高不锈钢方管的弯曲承载能力,且夹芯方管弯曲变形模式与方管的t/b比值相关。另外,对不同填充方式的泡沫铝夹芯方管进行弯曲实验,结果表明:夹芯方管填充的泡沫铝必需达到一定的长度,即最小有效长度L f ,eff,夹芯方管才能在较大范围的转角内依然保持较高的抗弯强度。最小有效长度的确定对制备部分填充泡沫铝的轻质夹芯结构有着重要的指导意义,有利于结构轻量化设计。更多还原

【Abstract】 Metallic foams are ultralight materials which possess high specific strength and energy absorption capacity. The metallic sandwich structure material is a new kind of ultralight structural and functional material which is prepared by filling metallic foams core into thin-walled structure. The mechanical behaviors and the deformation failure of sandwich structure have become one of the research hotspots in the material science, mechanics and other fields.In this paper, the aluminum foam-filled tubes are prepared by filling open-cell aluminum foams into thin-walled tubes. The open-cell aluminum foams are prepared by means of infiltrating process. The influence of the structural characteristic parameters both of the aluminum foam and the hollow tube on mechanical behaviors, energy absorption and yield behavior of the aluminum foam-filled tubes are explored. The main parameters of the samples are the relative density and pore diameter of the foam ranging form 0.399～0.524and 0.65~2.3mm respectively. The foam filled cylindrical tube diameter thickness ratio is between 5~30.4, and the foam-filled square tubes have the thickness width ratio (t/b) ranging form 0.012~0.032.Firstly, the static compression experiments have been conducted to investigate the compressive mechanical behavior of the circularity 6063 aluminum tubes filled with aluminum foams, The results show that the compressive load-displacement curves of aluminum tubes with foam filler exhibit a distinct characteristic of three deformation regions, i.e. elasticity region,serrated plastic plateau region and densification region. The factors such as the diameter thickness ratio of aluminum tube, the density and property of aluminum foam have remarkable effect on the mean crushing load and energy absorption characteristics of the foam-filled tube. Additionally, the compressive deformation pattern of the aluminum tube is also modified by the aluminum foam core, as compared with the non-filled tube. The wall of the tube with foam filler just folded outward during compression deformation.Secondly, the quasi-static three-point bending behavior of square 202 stainless steel tubes filled with aluminum foams is producted. The influence of aluminum foam relative density, t/b ratio and partially foam filled on bending behavior of the foam-filled tubes are mainly studied. The experimental results showed that the foams filler changes the local deformation mode of the tube, causes localized folding to propagate to the adjacent sections, and forces the tubes to form more plastic hinge lines, shorts the folding length. Therefore the foam filling improves the bending resistance of stainless steel tubes. Meanwhile,t/b ratio is the mainly influence parameter for deformation mode of the tube.Finally, It is also indicated that the length of the foam filling must reach a certain length, just the effective foam length L f ,eff, can the foam-filled tubes maintain higher crushing resistance under large scale rotation. The effective foam length L f ,eff offers significant reduction of the foam weight and should be used as a guideline for designing the ultralight foam-filled tubes.更多还原