【作者】 余为；

【导师】 李慧剑；

【作者基本信息】 燕山大学 ， 工程力学， 2011， 博士

【摘要】 工业技术、交通运输及航空航天科技的发展对轻质、高强材料的设计和制备提出了更高的要求。金属空心球多孔材料即是在此要求下发展起来的超轻多孔金属材料中的一种类型,对单球和多球组元力学性能的研究是研究金属空心球多孔材料整体力学性能和构成设计的一项十分重要的工作。本文对金属空心球多孔材料的单球、多球组元、金属空心球/环氧树脂复合材料进行了深入的理论分析、实验研究及数值模拟分析。研究金属空心球壳受刚性板压缩的理论结果具有重要意义,本文将球壳分为薄壁壳和中厚壁壳,分别导出了薄壁球壳压缩时的屈曲临界载荷和中厚壁球壳压缩的名义应力-应变关系,并进一步给出了球壳相对厚度的明确划分界限。为进一步研究金属空心球单球压缩性能,本文对由两个半球焊接而成的薄壁金属空心球单球和中厚壁金属空心球单球进行了准静态压缩实验,得出了其屈服/屈曲临界载荷、弹性模量及名义应力-应变关系,同时研究了焊缝摆放位置和焊接出现孔洞等因素对空心球力学性能的影响。多球组元的力学性能是金属空心球多孔材料设计的重要参考,本文设计了多种不同的多球组元堆积形式,分别对其进行了大量的准静态压缩实验,观察了其屈服/屈曲变形规律,并分析了其原因。通过分析载荷-位移曲线和有效应力-应变曲线,讨论了其屈服/屈曲极限、有效弹性模量、比刚度及能量吸收等力学性能,然后讨论了最优的堆积模式。金属空心球复合材料是多孔金属复合材料的一种形式,本文对薄壁金属空心球/环氧树脂复合材料、环氧树脂及复合泡沫材料进行了准静态压缩实验,研究了作为基体材料的环氧树脂和复合泡沫的力学性能,对比分析了复合材料的屈服极限和有效弹性模量。同时,通过改变金属空心球壁厚对三种堆积模式的复合材料进行了数值模拟,分析了其有效弹性模量、有效泊松比的变化规律,提出了复合材料中金属空心球的最佳堆积模式。为了进一步分析得出规律,本文对金属空心球半球壳进行了数值模拟,验证了实验结果,并分析了影响球壳屈曲的相对厚度临界值。通过对多球组元的数值模拟,验证了实验现象,给出了有效弹性模量,分析了三种堆积模式的力学性能。最后,根据理论和实验分析,提出了金属空心球多孔材料的多种构成形式,预测了其压缩过程中的垮塌规律,针对实际中可能的应用,提出了合理的结构设计。更多还原

【Abstract】 The development of industrial technology, communication, transportation and scientific & technical aerospace require development of lighter, stiffer, stronger and tougher structural materials and its preparation method. Metallic hollow sphere structural material is a type of the super-light cellular metallic material. Studies on the mechanical properties of single sphere and multi-sphere components are important work for the studies of mechanical behavior and form design of whole metallic hollow sphere cellular material. In this paper, the theoretic, experimental and numerical studies of mechanical properties of single sphere, multi-spheres component and metallic hollow sphere composite were carried out.In this paper, the mechanical properties of single sphere shell compressed between two rigid plates were studied. The theoretic critical force of thin-wall sphere shell under compression and the nominal stress-strain relationship of medium thick-walled sphere under compression were derived respectively. The dividing limit different from traditional theory of relative thickness of sphere shell was provided.Then, a series of quasi-static compressive experiments of thin-walled spheres and medium thick-walled spheres welded with two hemispheres were conducted. The deformation behaviors of it were observed, and its critical force of buckling or yield limit, Young’s modulus and effective stress-strain curves were obtained. And the influence of the change of angle between welding line and horizontal line was analyzed. The influence of cracks produced by welding was analyzed too.The mechanical properties of multi-spheres components are the basic reference for the design of metallic hollow sphere materials. In this paper, many packing models of multi-spheres components were devised and its quasi-static compressive experiments were carried out. The buckling or collapse behavior were observed and analyzed, and its load-displacement curves and effective stress-strain curves were obtained. The buckling or yield limit, effective elastic modulus, specific stiffness and specific energy absorb were discussed, and the optimal packing model was provided.Epoxy filled with one or many thin-walled metallic hollow spheres is a new style composite, and its quasi-static compressive experiments were conducted. The compressive experiments of epoxy and syntactic foam were also conducted for the comparative analysis. The yield limit and effective elastic modulus were discussed. Then, the numerical simulations of composite with three types of packing models were conducted by considering of the change of shell thick. The change laws of effective elastic modulus and effective Poisson’s ratio were discussed, and an optimal packing model of metallic hollow spheres in composite was provided.To analyse the laws, the numerical simulations of half sphere shells were conducted by changing the thick and radius of shell. The critical thick of buckling was gained and the deformation behavior agreed with the experiment. Then, the numerical simulations of multi-spheres components with three types of packing models were conducted too, and its effective yield limit and elastic modulus were provided. The mechanical behavior of the three types of packing models was analyzed.Finally, many type forms of metallic hollow sphere structure were provided. The laws of collapse in the process of compression were forecasted. And the reasonable structural designs for the actual applications were presented.更多还原