低应变率荷载作用下梯度泡沫铝力学性能研究

Study on Mechanical Properties of Gradient Aluminum Foam Under Low Strain Rate Loading

泡沫铝在工作状态下受到偶然低速荷载冲击作用会降低其吸能特性。本工作研究了匀质和梯度泡沫铝的准静态力学性能,测试了不同应变率(4×10^(-4)s^(-1)、3×10^(-3)s^(-1)、1×10^(-2)s^(-1))下梯度泡沫铝的压缩性能变化规律,同时采用X射线计算机断层扫描(X-CT)测定其压缩变形失效模式,探明了应变率及相对密度对梯度泡沫铝压缩吸能的影响规律。实验结果表明:在低速荷载作用下,匀质泡沫铝沿壁厚最薄弱区域开始变形,直至破坏;梯度泡沫铝则逐层压溃,直至失效破坏。相同应变率条件下,泡沫铝的强化倾向能力随相对密度提高而逐渐增强,梯度和匀质泡沫铝的应变率敏感系数分别最高可达0.235和0.210。泡沫铝初始压溃应力、平台应力随应变率提高而增大,梯度(MMH型)和匀质(H型)泡沫铝的初始压溃应力、平台应力分别最高可达10.02 MPa、10.7 MPa和12.89 MPa、10.19 MPa。相比匀质泡沫铝,梯度泡沫铝单位体积能量吸收值最多降低9%。本工作提出了以提高泡沫铝能量吸收效率为目标的最佳设计应力和能量吸收点的设计方法,可为泡沫铝夹芯结构防护面板的设计提供一定的参考。

The energy absorption characteristics of foamed aluminum will be deteriorated,when it is subjected to occasional low-speed loads.In this work,the quasi-static mechanical properties of single-layer and gradient foamed aluminums were studied.The compressive properties of gradient foamed aluminums were tested at different strain rates(4×10^(-4)s^(-1),3×10^(-3)s^(-1),1×10^(-2)s^(-1)),and the failure modes of compressive deformation were measured by X-ray computed tomography(X-CT).The effects of strain rate and relative density on the compression and energy absorption of gradient foamed aluminums were investigated.The experimental results showed that under low speed loads,uniform foamed aluminum deformed along the weakest area of wall thickness till failure,while gradient foamed aluminum collapsed layer by layer.At the same strain rate,the strengthening tendency ability of foamed aluminums increased gradually with the increase in relative density,and the strain rates sensitivity coefficients of gradient and single-layer foamed aluminums were up to 0.235 and 0.210,respectively.The initial collapses stress and pla-teau stress of foamed aluminums increased with the strain rate.The initial collapses stress and plateau stress of gradient(MMH)and single-layer(H)foamed aluminums increased to 10.02 MPa,10.7 MPa and 12.89 MPa,10.19 MPa,respectively.Compared with the uniform foamed aluminum,the energy absorption maximum value of gradient foamed aluminum decreased by 9%.In this work,the design method of optimal design stress and energy absorption point was proposed,aiming to improve the energy absorption efficiency of foamed aluminum.We expect to provide a certain reference for the design of the protective panel of the foamed aluminum sandwich structure.