On the usage of the effectively shaped indenter concept for analysis of yield strength
On the usage of the effectively shaped indenter concept for analysis of yield strength
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DOI：
10.1557/jmr.2009.0125
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发表时间：
2009-03
影响因子：
2.7
通讯作者：
M. Herrmann;F. Richter
中科院分区：
文献类型：
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作者：
M. Herrmann;F. Richter
利用扩展赫兹法（EHA），用参数集d _0， d _2, d _4， d _6来描述符合法尔概念的“有效成形压头”，该参数集可通过压痕试验卸载曲线的拟合程序确定。由于测量精度有限，一个给定的实验曲线原则上可以对应多个这样的参数集。在用伯氏压头对熔融石英进行压痕实验的基础上，我们研究了拟合过程本身对结果的影响。我们建议采用某种人工拟合程序，该程序与最大载荷无关，可获得屈服强度Y =(7.1±0.1)GPa。手工拟合总是包含一定程度的主观性，然而，Y和弹性场作为一个整体被证明对参数集的修改是相对稳健的。我们还建议一个初步的客观程序，其交付Y = 6.8−7.1 GPa。此外，我们还对屈服强度为Y = 7.0 GPa的von Mises固体中锥形压头的弹塑性压痕进行了有限元模拟。采用与试验曲线相同的EHA方法对模拟卸载曲线进行分析，得到的屈服强度为6.95 GPa，与有限元输入值非常接近。
Using the extended Hertzian approach (EHA), the “effectively shaped indenter” corresponding to Pharr’s concept is described in terms of a parameter set d _0, d _2, d _4, d _6, which can be determined by a fitting procedure from the unloading curve of an indentation experiment. Owing to the limited accuracy of measurement, a given experimental curve may in principle correspond to more than one such parameter set. Based on indentation experiments with a Berkovich indenter into fused silica, we have investigated the influence of the fitting procedure itself on the results. We suggest a certain manual fitting procedure, which delivered a yield strength Y = (7.1 ± 0.1) GPa independent of the maximum load. Manual fitting always includes some degree of subjectivity, however, both Y and the elastic field as a whole proved to be relatively robust against modifications of the parameter set. We also suggest a preliminary objective procedure, which delivered Y = 6.8 − 7.1 GPa. In addition, we have performed finite element method (FEM) simulations of elastic–plastic indentations of a conical indenter into a von Mises solid with a yield strength of Y = 7.0 GPa. The simulated unloading curve was analyzed using the EHA in the same manner as the experimental curves, and yield strength of 6.95 GPa was obtained being very close to the input value of the FEM.