纳米压痕试验中圆柱形压头尺寸效应

针对薄膜材料在纳米压痕试验时出现的压痕尺寸效应,运用准连续介质法模拟单晶铝膜纳米压痕试验初始塑性变形过程。分析了不同直径的刚性圆柱形压头分别压入同一深度时弹性和塑性变形特点,并获得了相应的载荷—压深曲线。基于Oliver-Pharr法,预测了纳米硬度值和弹性模量。研究数据表明:纳米硬度值随着压头直径的增加而减小,呈现出明显的压头尺寸效应;当压头直径达到或超过80时纳米硬度值趋于稳定值,即压头尺寸效应消失。同时表明弹性模量不存在尺寸效应。表明材料的弹性模量本质上仅依赖原子间的结合能,而和压头尺寸基本无关。

Cylinder indenter size effect in Nanoindentation test

The initial plastic deformation of single crystal aluminium was simulated to study the indentation size effect in the nanoindentation test by using quasicontinuum method, The feature of elastic and initial plastic deformation in the indentation tests in case of rigid cylinder indenters with different diameter was investigated. The corresponding load - depth curves were obtained. The nanohardness and elastic modulus were estimated based on the Oliver - Pharr method. The simulated results show that nanohardness decreases significantly with the increase of the indenter size, i. e. , there exists strong indentation size effect on nanoberdness. However, the size effect phenomenon vanishes for a larger indenter size more than 80A. The results also show that size effect on elastic modulus may be ignored. It indicates that the elastic modulus is dependent on the binding energy of the atoms, whereas it is independent on the indenter size.