梯度泡沫铝的各向异性压溃力学行为

功能梯度泡沫金属因其密度连续变化,在轴向受压时可提供稳定增长的反馈载荷。然而当前研究多局限于其纵向压缩力学响应,考虑到实际应用中可能出现的横向冲击,基于低速冲击实验,考察梯度泡沫铝轴向和横向压缩力学响应的异同,并采用数字图像相关技术和数值模拟方法研究其宏细观压溃机制。结果表明:(1)在力学性能上,相比于纵向压缩加载的梯度泡沫铝,横向压缩加载下具有更高的抗压强度,而平台应力、致密化应变和能量吸收效果低于纵向压缩;(2)在失效变形模式上,纵向压缩变形模式为变形带渐进式压缩,而横向压缩变形模式的变形带则随机出现在试样的各个位置;(3)横向压缩下梯度泡沫铝致密化应变和比吸能的减小是由高孔隙率区的胞孔利用率降低导致的;(4)构建的弹性-塑性硬化-刚性模型能够较准确地描述梯度泡沫铝的纵向压缩力学行为。研究结果可为梯度泡沫金属在爆炸冲击结构防护工程中的设计提供理论参考。

Study on Anisotropic Crushing Behavior of the Functionally Gradient Aluminum Foam

Due to the continuous variation of material density in functionally gradient aluminum foams,a feedback load gradually increases within the compression process.Currently,most of the researches have been focused on the longitudinal compression mechanical response.However,considering the possible transverse impact in practical application,we investigated functionally gradient aluminum foams in terms of the axial and transverse compressive mechanical responses based on low-speed impact experiments,and also studied their macro and mesoscopic crushing mechanism via the digital image correlation and numerical simulation technology.The results were shown that:(1)Compared with that under longitudinal compression,the functional gradient aluminum under transverse compression has higher compressive strength and lower platform stress,densification strain and energy absorption.(2)In the aspect of failure deformation mode,the longitudinal compression deformation mode is progressive compression of deformation band,while the deformation band of transverse compression appears randomly at each position of the sample.(3)Under transverse compression,the densification strain and specific energy absorption of the functionally gradient aluminum foam get decreased by the reduction of cellular utilization in the higher porosity zone.(4)The established elastic-plastic hardening-locking(E-PH-L)constitutive model can well capture the longitude compression response of the functionally gradient aluminum foam.This study therefore can provide a reference for the theoretical design of functionally gradient aluminum foam in the protection engineering of explosive impact structures.