Nanoindentation and the indentation size effect: Kinetics of deformation and strain gradient plasticity
Nanoindentation and the indentation size effect: Kinetics of deformation and strain gradient plasticity
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DOI：
10.1016/s0022-5096(02)00033-9
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发表时间：
2003-02-01
影响因子：
5.3
通讯作者：
Stone, DS
中科院分区：
文献类型：
--
作者：
Elmustafa, AA;Stone, DS
本文研究了铝和α黄铜的压痕尺寸效应。该研究采用率效应来研究负责伊势的基本机制。这些速率效应的特征在于硬度的速率敏感性，偏导数H/偏导数ln（λ）over-dot（eff），其中H是硬度，（λ）over-dot（eff）是压头下方塑性体积中的有效应变速率。偏导数H/偏导数ln（eff）过点（eff）可以使用压痕蠕变、载荷松弛或速率变化实验来测量。计算基于偏导数H/偏导数ln（eff）over-dot（eff）计算的活化体积V*，偏导数H/偏导数ln（eff）over-dot（eff）传统上可用于比较来自硬度测试的速率敏感性数据与常规单轴测试。使用不同的堆垛层错能和不同水平的加工硬化的试样的材料，我们演示了如何增加位错密度的影响V*，这些效果可以被视为位错强化机制的动力学签名。我们注意到H和偏导数H/偏导数ln（λ）over-dot（eff）（V*）都表现出伊势。作为伊势结果的V* 与H的过程与具有不同加工硬化水平的试样的测试过程一致。在两种材料中均观察到该结果。这表明，位错机制是负责伊势。当结果拟合到应变梯度塑性模型时，在深压痕处的数据（显微硬度和大纳米压痕）表现出与文献数据紧密相同的直线行为。然而，对于浅压痕（纳米压痕数据），线的斜率严重变化，减少了10倍，导致“双线性行为”。(C)2003爱思唯尔科技有限公司版权所有。
A study of the indentation size effect (ISE) in aluminum and alpha brass is presented. The study employs rate effects to examine the fundamental mechanisms responsible for the ISE. These rate effects are characterized in terms of the rate sensitivity of the hardness, partial derivativeH/partial derivative ln (epsilon)over-dot(eff), where H is the hardness and (epsilon)over-dot(eff) is an effective strain rate in the plastic volume beneath the indenter. partial derivativeH/partial derivative ln (epsilon)over-dot(eff) can be measured using indentation creep, load relaxation, or rate change experiments. The activation volume V*, calculated based on partial derivativeH/partial derivative ln (epsilon)over-dot(eff) which can traditionally be used to compare rate sensitivity data from a hardness test to conventional uniaxial testing, is calculated. Using materials with different stacking fault energy and specimens with different levels of work hardening, we demonstrate how increasing the dislocation density affects V*; these effects may be taken as a kinetic signature of dislocation strengthening mechanisms. We noticed both H and partial derivativeH/partial derivative ln (epsilon)over-dot(eff) (V*) exhibit an ISE. The course of V* vs. H as a result of the ISE is consistent with the course of testing specimens with different level of work hardening. This result was observed in both materials. This suggests that a dislocation mechanism is responsible for the ISE. When the results are fitted to a strain gradient plasticity model, the data at deep indents (microhardness and large nanoindentation) exhibit a straight-line behavior closely identical to literature data. However, for shallow indents (nanoindentation data), the slope of the line severely changes, decreasing by a factor of 10, resulting in a "bilinear behavior". (C) 2003 Elsevier Science Ltd. All rights reserved.