Experimental and computational issues for automated extraction of plasticity parameters from spherical indentation
Experimental and computational issues for automated extraction of plasticity parameters from spherical indentation
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DOI：
10.1016/j.mechmat.2018.06.004
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发表时间：
2018-09-01
影响因子：
3.9
通讯作者：
Clyne, T. W.
中科院分区：
文献类型：
--
作者：
Campbell, J. E.;Thompson, R. P.;Clyne, T. W.
正在开发用于从压痕数据自动提取塑性参数的软件包（主要是载荷-位移曲线，尽管剩余的压痕尺寸数据也可能是有用的）。它们的设计必须与相关的实验测量紧密结合。该过程涉及到迭代有限元模拟的球形压头到样品的渗透，与自动收敛的最佳拟合的参数值的特征屈服和加工硬化的材料响应（在本构关系）。本文概述了实验条件和模型制定的优化所涉及的主要问题。说明性的实验数据，从5种金属材料的挤压棒。实验问题包括压头半径R和穿透深度5的尺寸尺度，其中delta/R（“穿透比”）具有特别重要的意义。一个简短的研究提出了潜在的冲突的要求，变形的体积足够大，以代表响应的散装和有一个值的delta/R，创建塑性应变的范围内，将充分捕获的加工硬化响应。这项研究的一个关键结论是，一个“中档”压痕设施可能是最佳的，至少有几千牛的负载能力，能够创建delta/R值高达40%，与R类似0.5-2毫米。其他实验问题包括位移测量技术，校准机器的顺应性和材料各向异性的可能性（由于晶体结构）。与有限元模型的制定有关的问题包括区域和网格的指定，本构塑性定律的选择和界面摩擦的模拟。还描述了所使用的收敛算法。
Software packages are being developed for automated extraction of plasticity parameters from indentation data (primarily load-displacement plots, although residual indent dimension data are also likely to be useful). Their design must be closely integrated with the associated experimental measurements. The procedure involves iterative FE simulation of the penetration of a spherical indenter into a sample, with automated convergence on a best-fit set of parameter values characterizing the yielding and work hardening response of the material (in a constitutive law). This paper outlines the main issues involved in optimization of experimental conditions and model formulation. Illustrative experimental data are presented from extruded rods of 5 metallic materials. Experimental issues include the dimensional scales of the indenter radius, R, and the depth of penetration, 5, with delta/R (the "penetration ratio") being of particular significance. A brief study is presented of the potentially conflicting requirements of deforming a volume large enough to represent the response of the bulk and having a value of delta/R that creates plastic strains in a range that will adequately capture the work hardening response. A key conclusion of this study is that a "mid-range" indentation facility is likely to be optimal, with a load capability of at least a few kN, able to create delta/R values up to similar to 40%, with R similar to 0.5-2 mm. Other experimental issues include displacement measurement techniques, calibration of machine compliance and the possibility of material anisotropy (due to crystallographic texture). Issues related to formulation of the FE model include specification of the domain and mesh, selection of the constitutive plasticity law and simulation of interfacial friction. The convergence algorithm used is also described.