闭孔泡沫铝的孔隙结构及压缩变形过程研究

为研究压缩空气法制备的闭孔泡沫铝的孔隙结构对其力学性能的影响和压缩变形过程,测量了不同密度泡沫铝的孔隙结构参数,分析了孔径与密度关系,并通过单向压缩实验,分析了密度对破碎压力和杨氏模量的影响以及裂纹产生与扩展情况.研究结果表明：泡沫铝的孔径与密度的关系为ρ＊=0.108 5＋4.862 7exp（-0.608Φ）.在单向压缩时,随着压缩载荷的增加,孔壁在弹性变形后产生弯曲,裂纹首先在应力集中的缺陷处和孔壁强度低的位置产生向次薄弱的孔壁扩展.应力水平越高,裂纹扩展越快;当孔的壁面上存在强度差异时产生褶皱;裂纹贯穿孔壁后发生失稳断裂并可能发生转动,并导致塑性坍塌;应变继续增加,孔穴破碎进入致密化过程.

Study of Cell Structure and Compressive Deformation Process of A Closed Cell Aluminum Foam

Effect of cell structure on mechanical properties and compressive deformation process of a closed cell aluminum foam by air injection was studied. The parameters of cell structure with varied densities were measured,the relation of cell size,density and node size were explored,and uni-axial compressive experiment was conducted to analyze the effect of density on collapse strength,Young＇s modulus and crack initiation and propagation. The result show that the cell wall thickness and node size of aluminum foams decrease with increasing cell size,and the relation of the cell diameter and density is expressed as ρ＊= 0. 1085 ＋ 4. 8627exp（- 0. 608 Φ）.When foam density increase from 0. 12 to 0. 28 g / cm3,the collapse strength in uni-axial compression rises from 0. 26 to 1. 44 MPa,while Young＇s modulus of the closed cell aluminum foam increases from 0. 65 to 1. 51 GPa. The cell wall has some initial curvature after elastic deformation with increasing load,and the deformation is strongly localized to defects and the thinnest parts of the cell wall,where cracks initiate and propagate faster in higher stress. The corrugation is caused by incomparable strength in the cell wall membrane,and the cracks become unstable and rotate in their directions after running through the wall,which causes plastic collapse of the cells.The further increase in strain results in subsequent densification process.