【作者】 曾嵩；

【导师】 刘金强； 朱荣；

【作者基本信息】 南京理工大学 ， 材料学， 2012， 硕士

【摘要】 本文采用拼装工艺制备6061铝合金四棱锥点阵夹芯材料,将带有插针插孔的基本拼装单元按一定顺序拼装成四棱锥点阵夹芯体,并采用钎焊工艺互连芯体与面板,通过选择不同的芯体杆元宽度制备不同相对密度(0.052～0.068)的四棱锥点阵夹芯材料。通过准静态压缩性能测试,研究不同相对密度的四棱锥点阵夹芯材料的准静态压缩性能以及能量吸收性能。根据压缩结果结合三个力学模型进行峰值压缩强度的分析比较,并提出力学性能强化方案,从形状优化、拓扑优化两方面进行四棱锥点阵夹芯材料的设计、制备及力学性能研究。研究表明四棱锥点阵夹芯材料的压缩过程包括线弹性变形、塑性屈服、致密化三个阶段。随着芯体相对密度的增加,其峰值压缩强度也在增加。非弹性屈曲模型根据相对密度、基体材料屈服强度、应变硬化能力成功预测了铝合金四棱锥点阵夹芯结构的峰值压缩强度,预测值与测量值有良好的一致性。四棱锥点阵夹芯材料的能量吸收能力在整个压缩过程中单调增加,随着夹芯相对密度的增加,能量吸收能力也在增加。不同相对密度的四棱锥点阵夹芯材料能量吸收效率曲线形状相似,呈现先升后降的现象,均在应变0.25左右达到峰值,能量吸收效率很高,在一个宽应变范围内(0.15～0.35)维持在70%以上。形状优化中将四棱锥点阵结构的开孔角度由30°减少为15°,使得四棱锥点阵夹芯材料力学性能得到进一步的改善,其比强度和单位质量能量吸收相较于之前未优化的点阵夹芯材料分别提高了25%和30%左右；拓扑结构优化在减轻四棱锥点阵夹芯材料质量的同时,进一步的提高了峰值压缩强度,结构的比强度、单位质量能量吸收均有较大的提高,为未优化设计前的点阵夹芯材料的2倍左右,也高于形状优化后的点阵夹芯材料。更多还原

【Abstract】 A pyramidal lattice truss structure of 6061 aluminum alloy has been fabricated by assembly of slotted metal sheets, followed by air brazing to join the structure with aluminum plates on top-and-bottom making a sandwich structure. Structures with different cellular core relative densities ranging between 0.052 and 0.068 were obtained by changing the widths of the lattice truss. The static compressive mechanical behaviors and energy absorption performance of the fabricated pyramidal lattice truss sandwich samples were studied by the quasi-static compression tests. According to the results of the measured static compressive properties and theoretical estimates based on three mechanical analytical models, optimizing schemes were proposed to strengthen the mechanical properties of pyramid lattice truss sandwich structures from three aspects including shape optimization and topology optimization.The result shows that pyramidal lattice truss cores exhibited similar compressive stress strain to those of many cellular metals, their compression process included three stages:linear elastic stage, softening stage and densification stage. With the adding of core relative density, the measured peak compressive strengths have increased obviously. A model based on inelastic column-buckling theory incorporating strain hardening was able to predict the pyramidal lattice core’s compressive peak strength over a range of relative densities, parent alloy yield strengths, and strain hardening capacities. The energy absorption capacity in the compression process increased monotonically with the adding of core relative density, while the energy absorption efficiency exhibited a rising and descending curve with a peak at the strain of 0.25. In a wide range of strain (varied from 0.15 to 0.35), the energy absorption efficiency of the pyramidal lattice truss sandwich structures maintained in 70% above. After decreasing the opening angle of the pyramid lattice cores from 30°to 15°, the mechanical properties of pyramidal lattice truss sandwich structures were well strengthened. The specific strength was enhanced about 25%, while the energy absorbed per unit mass was improved about 20%. An innovative topology structure provided a further strengthen of the pyramidal lattice truss sandwich structures. The value of their specific strength and energy absorbed per unit mass were both about twice of the pyramidal lattice truss sandwich structures without optimization, and higher than the shape-optimized sandwich structures also.更多还原