Understanding nanoindentation unloading curves
Understanding nanoindentation unloading curves
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DOI：
10.1557/jmr.2002.0386
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发表时间：
2002-10-01
影响因子：
2.7
通讯作者：
Bolshakov, A
中科院分区：
文献类型：
--
作者：
Pharr, GM;Bolshakov, A
实验表明，用布氏三角锥压头获得的纳米压痕卸载曲线通常由幂律关系P = alpha（h-h（f））（m）很好地描述，其中h（f）是完全卸载后的最终深度，alpha和m是材料常数。然而，幂律指数并不是固定在一个整数值，就像圆锥形压头（m = 2）或扁平圆形冲头（m = 1）的弹性接触的情况一样，而是在m = 1.2-1.6的范围内随材料而变化。一个简单的模型，开发的基础上观察从有限元模拟压痕的弹塑性材料的刚性锥，提供了一个物理解释的行为。该模型，这是基于一个“有效形状”，其几何形状是由压痕过程中形成的塑性硬度印象的形状确定的压头的概念，提供了一种手段，通过该材料常数的幂律关系可以涉及到更基本的材料性能，如弹性模量和硬度。简单的参数，提出了有效压头形状可以来自压头下的压力分布。
Experiments have shown that nanoindentation unloading curves obtained with Berkovich triangular pyramidal indenters are usually well-described by the power-law relation P = alpha(h - h(f))(m), where h(f) is the final depth after complete unloading and alpha and m are material constants. However, the power-law exponent is not fixed at an integral value, as would be the case for elastic contact by a conical indenter (m = 2) or a flat circular punch (m = 1), but varies from material to material in the range m = 1.2-1.6. A simple model is developed based on observations from finite element simulations of indentation of elastic-plastic materials by a rigid cone that provides a physical explanation for the behavior. The model, which is based on the concept of an indenter with an "effective shape" whose geometry is determined by the shape of the plastic hardness impression formed during indentation, provides a means by which the material constants in the power law relation can be related to more fundamental material properties such as the elastic modulus and hardness. Simple arguments are presented from which the effective indenter shape can be derived from the pressure distribution under the indenter.