共查询到20条相似文献,搜索用时 15 毫秒
1.
Sheng-Chung Tzeng Wei-Ping Ma 《The International Journal of Advanced Manufacturing Technology》2007,32(5-6):473-479
This investigation proposes a modified technique for manufacturing closed-cell aluminum (Al) foams to reduce the cost of the
foaming agents during the casting and foaming processes. The addition of foaming agents promotes the uniformity of cell sizes
and controls the viscosity of the melting aluminum alloy. This work elucidates the mechanical characteristics of closed-cell
aluminum foams under compressive loading. The discussions in this paper cover the compressive stress–strain curve and the
densification strain and energy absorption effects of various specimens with various porosities. The thermal conductivity
of the aluminum foams is determined, and the results are compared with some theoretical predictions. The optimum parameters
for meeting some practical design requirements, such as impact absorption and thermal insulation design applications, are
discussed. Finally, an empirical correlation between the normalized yield strength and the relative densities is obtained. 相似文献
2.
闭孔泡沫铝力学特性及其在汽车碰撞吸能中的应用研究进展 总被引:8,自引:0,他引:8
汽车低能耗、安全和轻量化已经成为汽车领域研究的热点问题,闭孔泡沫铝作为一种轻质吸能金属材料,在低密度下具有良好的比刚度和比强度,同时具有良好的抗冲击性和能量吸收性,已逐渐引起汽车产业界地重视。简述泡沫铝单轴压缩试验中弹性模量、抗压强度、屈服强度、平台应力、致密化应变等参数的定义和试验标准;综述闭孔泡沫铝的本构方程的研究现状,重点讨论屈服面模型;总结泡沫铝的微观结构有限元建模方法,比较商业软件中集成的宏观材料模型。归纳吸能材料的特点,分析闭孔泡沫铝的吸能能力和抗冲击能力;综述应变率和冲击速度对泡沫铝吸能特性有无影响的研究进展,并对可能存在的影响进行解释。总结闭孔泡沫铝在汽车轻量化和碰撞安全性领域的应用,具体分析典型的案例。指出当前闭孔泡沫铝的力学特性及其在汽车结构中应用存在的问题与难点,总结并提出本研究领域可以借鉴的研究方向。 相似文献
3.
泡沫铝结构对其拉伸力学性能的影响 总被引:1,自引:0,他引:1
研究了开孔与闭孔两种胞孔结构的泡沫铝在不同相对密度下的准静态拉伸力学性能,并与单向压缩性能进行了对比.结果表明:开孔和闭孔泡沫铝的拉伸曲线由线弹性变形段和塑性变形段组成,线弹性变形段很短,塑性屈服中没有出现明显的屈服点;高密度的开孔泡沫铝的杨氏模量、抗拉强度较低密度的闭孔泡沫铝要大;随着相对密度的增大,两种结构泡沫铝的力学性能均明显增强,符合Gibson和Ashby关系式,泡沫铝在准静态下的抗拉强度比抗压强度略低,而拉伸杨氏模量比压缩杨氏模量大得多. 相似文献
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用熔体发泡法制备了碳化硅颗粒增强泡沫铝样品,分析了碳化硅增强泡沫铝在准静态压缩条件下的变形行为。用不锈钢圆管为面板,碳化硅颗粒增强泡沫铝为夹芯制备层合圆管,研究了层合圆管在准静态压缩条件下的变形行为和能量吸收性能。研究表明:碳化硅颗粒增强泡沫铝的屈服强度在5~12MPa之间,对泡沫铝材料的力学性能有明显的增强作用;层合圆管在保持泡沫铝轻质、高吸能效率的同时,大幅度提高了吸能能力;碳化硅增强泡沫铝层合圆管的压缩屈服应力达到45MPa,平台应力达到40MPa,具有优良的吸能性能。 相似文献
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采用压力渗透法制备出了铝基复合泡沫材料,填充材料是以粉煤灰漂珠为主要组分、硬质聚氨酯泡沫为粘结剂的复合泡沫材料.通过准静态实验和分离式霍普金森压杆(Split Hopkinson pressure bar,SHPB)动态压缩的方法研究了复合泡沫铝的压缩力学响应,然后建立了动态本构关系.研究表明,复合泡沫铝的压缩应力-应变曲线与其它泡沫材料的应力-应变曲线类似,文中的两种铝基复合泡沫具有应变率效应,复合泡沫铝较密度相近未填充前的泡沫铝基具有更高的压缩强度与能量吸收能力.但由于漂珠尺寸的不同,导致两种复合泡沫铝的动态压缩结果不尽相同,且小颗粒复合泡沫铝在动态冲击下吸能效果最好.在本研究实验的应变率和密度范围内,本文建立的本构模型曲线与实验曲线吻合较好. 相似文献
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采用压力渗透法制备出了铝基复合泡沫材料,填充材料是以粉煤灰漂珠为主要组分、硬质聚氨酯泡沫为粘结剂的复合泡沫材料.通过准静态实验和分离式霍普金森压杆(Split Hopkinson pressure bar,SHPB)动态压缩的方法研究了复合泡沫铝的压缩力学响应,然后建立了动态本构关系.研究表明,复合泡沫铝的压缩应力-应变曲线与其它泡沫材料的应力-应变曲线类似,文中的两种铝基复合泡沫具有应变率效应,复合泡沫铝较密度相近未填充前的泡沫铝基具有更高的压缩强度与能量吸收能力.但由于漂珠尺寸的不同,导致两种复合泡沫铝的动态压缩结果不尽相同,且小颗粒复合泡沫铝在动态冲击下吸能效果最好.在本研究实验的应变率和密度范围内,本文建立的本构模型曲线与实验曲线吻合较好. 相似文献
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采用隔热测试仪研究了闭孔泡沫纯铝的孔隙率和孔径对其导热性能(导热系数)的影响.结果表明:闭孔泡沫纯铝的导热性能受传导、对流、辐射三者的综合影响;孔隙率为83.2%~91.0%的闭孔泡沫纯铝的导热系数随孔隙率的增大而减小,而孔径对导热系数的影响没有一定规律;在孔隙率为83.2%~91.0%、孔径为2.5~5.3 mm时,闭孔泡沫纯铝的导热系数在常温下为0.297~0.752 W/(m·K). 相似文献
9.
Graphite foams consist of a network of interconnected graphite ligaments and are beginning to be applied to thermal management
of electronics. The thermal conductivity of the bulk graphite foam is similar to aluminum, but graphite foam has one-fifth
the density of aluminum. This combination of high thermal conductivity and low density results in a specific thermal conductivity
about five times higher than that of aluminum, allowing heat to rapidly propagate into the foam. This heat is spread out over
the very large surface area within the foam, enabling large amounts of energy to be transferred with relatively low temperature
difference. For the purpose of graphite foam thermosyphon design in electronics cooling, various effects such as graphite
foam geometry, sub-cooling, working fluid effect, and liquid level were investigated in this study. The best thermal performance
was achieved with the large graphite foam, working fluid with the lowest boiling point, a liquid level with the exact height
of the graphite foam, and at the lowest sub-cooling temperature. 相似文献
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The stiffness of closed-cell low-density cellular solids, or solid foams, is affected by “imperfections” such as non-uniform cell shape and size, wavy distortions of cell walls, variations in cell wall thickness, etc. The present paper focuses on the influence of non-uniform cell wall thickness on stiffness. Calculations are performed on one model with different degrees of thickness variations. The model used is the flat-faced Kelvin structure, which consists of 14-sided polyhedra in a bcc arrangement. The results indicate that the stiffness of closed-cell cellular solids is not very sensitive to thickness variations. 相似文献
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采用熔体发泡法制备了孔结构均匀、孔隙率高的泡沫铝材料,系统研究了铝粉(增粘剂)含量、增粘搅拌时间、保温时间和发泡剂的含量对孔隙率和孔结构的影响。对铝粉在铝熔体中的增粘机理以及在发泡过程中对气泡的稳定作用进行了讨论。结果表明:加入质量分数5%铝粉,搅拌时间7 min,发泡剂TiH2质量分数1.5%,保温5 min的条件下,可以得到孔结构均匀、孔隙率约75%的泡沫铝硅合金材料。 相似文献
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沥青发泡本质特征解析下的腔体设计与评价 总被引:1,自引:0,他引:1
一定条件下沥青产生泡沫现象即为沥青发泡过程,是在特定容积的腔体中多物理场和流场耦合效应的结果。发泡性能受控制参数(压力、温度、流量),沥青物理性质(针入度、粘度)以及装备中关键部件结构参数(发泡腔体的结构形式、各喷嘴的尺寸、位置)的影响。为制备高品质(膨胀率大,半衰期长)泡沫沥青,必须遵循沥青发泡行为的本质特征,在多参数条件下对多相流的耦合场进行精确的过程控制。为此,以沥青发泡装置的关键部件为研究对象,总结国内外典型发泡腔的结构形式,并提出一种新型发泡腔结构形式。采用理论与试验并行的研究方法,分析沥青发泡的本质特征,并在强模糊性的多相流耦合场中探寻沥青发泡效果的评价指标,最终构建出沥青发泡本质特征与发泡腔体设计之间的映射规律。 相似文献
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Metallic foams as a filler in thin-walled structures can improve their crashworthiness characteristics. In this article, nonlinear parametric finite element simulations of FGF foam-filled conical tube are developed and the effect of various design parameters such as density grading, number of grading layers and the total mass of FGF tube on resulting mode shapes, specific energy absorption and initial peak load is investigated. Multi design optimization (MDO) technique and the geometrical average method, both are based on FE model are applied to maximize the specific energy absorption and minimize the impact peak force by estimating the best wall thickness and gradient exponential parameter “m” that controls the variation of foam density. The results obtained from the optimizations indicated that functionally graded foam material, with graded density, is a suitable candidate for enhancing the crashworthiness characteristics of the structure compared to uniform density foam. 相似文献
15.
闭孔泡沫铝在圆柱形平压头下的压痕性能 总被引:1,自引:0,他引:1
采用圆柱形平压头对闭孔泡沫铝进行了压痕试验,研究了压头直径、泡沫铝相对密度及边界条件对压痕响应、压痕硬度、吸能特性等的影响,并与单向压缩试验结果进行了对比.结果表明:闭孔泡沫铝压痕试验的应力-应变曲线与其单向压缩时的相似,但压痕试验时的屈服强度显著高于单向压缩时的;压痕试验时泡沫铝的变形被严格限制在压头之下,并且是局部的不均匀变形;压痕试验时泡沫铝的撕裂能和能量吸收效率不随压头直径和泡沫铝相对密度的变化而变化;压痕硬度随压头直径的增加而线性减小,随相对密度的增加而线性增大;其吸能能力分别随压头直径及相对密度的增加而线性增大;压痕深度在一定范围内(小于6 mm),刚性基础和筒支边界条件对泡沫铝在圆柱形平压头作用下压痕响应的影响可以忽略不计. 相似文献
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基于三类单胞模型的开、闭孔泡沫材料弹性性能的有限元分析 总被引:1,自引:0,他引:1
在对发泡过程进行假设的基础上,根据泡沫材料微结构的特点,建立开孔和闭孔泡沫材料的简单立方、面心立方和体心立方单胞模型,导出相对密度和胞体结构参数的定量关系.由这三类单胞模型描述的泡沫材料均具有周期性的特点,且单胞还具有结构对称性.文中利用有限元方法,在适当的边界条件下计算整个密度范围内泡沫材料的弹性模量和泊松比,数值拟合模量计算公式.通过与已有的实验资料和理论预测结果的比较,说明有限元数值计算的有效性. 相似文献
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