金属泡沫材料压缩响应模式转变分析

Transition of Deformation Mechanism in Compressed Metal Foam

金属泡沫材料的压缩响应是微结构相关的,低无序时以单一塌缩带的形核和扩展为主,高无序度时,主要是扩展能力很弱的弥散塌缩带形核所控制。基于考虑材料微结构Weibull分布的应变梯度塑性模型,探究了胞孔塑性屈曲时,相对强度改变和相对密度改变对变形模式转捩的影响。研究发现:当相对密度改变量为定值时,随相对强度改变量的增大,变形模式的转变在较低的无序度下发生。而强度改变量为定值时,相对密度改变量的变化对多孔材料压缩变形模式转变的临界无序度无确定的影响规律,但变形模式转捩点的应力水平随相对密度改变量的减小而下降。

Based on the compressive strain gradient plasticity model, numerical simulation was implemented to investigate the effects of relative strength reduction and relative density change on the intersection of the curves of yield stress and plateau stress, which means the effects on the transition of deformation mode. The sample of solid foam was discretized into finite elements and the yield stresses of all the elements were assumed to fall into the Weibull distribution. With the increase of relative strength change, the results reveal that the plateau stress increases apparently while the yield stress rises slightly, and that the intersection of the curves of the yield stress and plateau stress appears in lower disorder. Whereas with the decrease of the relative density change, there is no significant change of critical disorder in which the intersection occurs, but both the yield stress and plateau stress corresponding to the intersection become smaller.