泡沫金属材料的孔径效应

在分离式霍普金森压杆(SHPB)和MTS 810材料试验机上分别对泡沫纯铝材料和铝硅合金泡沫材料进行了动态与准静态压缩实验研究.实验结果表明:孔径的大小对泡沫铝的弹性变形包括弹性模量没有影响,但对泡沫铝的屈服强度和塑性硬化模量有影响,且这种影响主要取决于泡沫铝基体材料的韧脆特性,泡沫铝的相对密度也会影响这种孔径效应.  

泡沫铝泡孔动态变形特性研究

在SHPB实验中采用"应变冻结法"将试件"冻结"于设定的压缩应变,然后观察内部泡孔的变形情况并讨论其变形机理.分别对同一相对密度(40%)、不同基体材料的两种泡沫铝以及两种相对密度(19%和8%)、相同基体材料的泡沫铝进行实验,讨论了基体材料的本构关系、泡沫的相对密度对变形模式的影响.利用ANSYS/LS-DYNA软件对泡沫铝在动态压缩时泡孔的变形进行数值模拟计算,进一步说明泡沫铝泡孔变形的模式与基体材料本构关系及相对密度的关系.  

Dense packing properties of mineral admixtures in cementitious material

The effect of ultra-fine fly ash （UFFA）, steel slag （SS） and silica fume （SF） on packing density of binary, ternary and quaternary cementitious materials was studied in this paper in terms of minimum water requirement of cement. The influence of mineral admixtures on the relative density of pastes with low water/hinder ratios was analyzed and the relationship between paste density and compressive strength of the corresponding hardened mortars was discussed. The results indicate that the incorporation of mineral admixtures can effectively improve the packing density ofcementitious materials; the increase in packing density of a composite with incorporation of two or three kinds of mineral admixtures is even more obvious than that with only one mineral admixture. Moreover, an optimal amount of mineral admixture imparts to the mixture maximum packing density. The dense packing effect of a mineral admixture can increase the packing density of the resulting cementitious material and also the density of paste with low water/binder ratio, which evidently enhances the compressive strength of the hardened mortar.