A methodology for obtaining primary and secondary creep characteristics from indentation experiments, using a recess
A methodology for obtaining primary and secondary creep characteristics from indentation experiments, using a recess
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DOI：
10.1016/j.ijmecsci.2020.105577
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发表时间：
2020-06-15
影响因子：
7.3
通讯作者：
Clyne, T. W.
中科院分区：
文献类型：
--
作者：
Burley, M.;Campbell, J. E.;Clyne, T. W.
描述了一种压痕蠕变塑性测量方法(使用球形压头)，该方法类似于以前发展的压痕塑性测量方法。在这种情况下，它是基于压痕过程的迭代数值模拟，在实验结果和相应的模型预测之间反复比较，系统地改变本构定律中的参数值，直到达到最佳一致。这里使用的本构关系是Miller-Norton关系，它涵盖了一次蠕变和二次蠕变(尽管它们之间的转变并不是很明确)。实验结果表明，在恒定载荷作用下，侵彻深度随时间变化。该过程的一个重要特征是在样品中预先创建球形凹槽，该凹槽具有预先选择的深度和等于压痕的曲率半径。这允许控制在压痕蠕变测试期间产生的应力水平，并可用于确保在测试期间不会刺激(与时间无关的)塑性变形。在没有这种凹槽的情况下，这几乎是不可避免的，因为在球形压头和平面之间的初始接触期间产生的应力水平往往非常高。这种可塑性给蠕变测试带来了不必要的复杂情况。通过比较用这种方法获得的纯镍样品在750℃下的蠕变特性和通过常规单轴拉伸试验获得的蠕变特性，证实了该方法的可行性。
A procedure is described for Indentation Creep Plastometery (using a spherical indenter), which is analogous to that developed previously for Indentation Plastometry. As in that case, it is based on iterative numerical simulation of the indentation process, with repeated comparison between an experimental outcome and the corresponding model prediction, systematically varying the values of parameters in a constitutive law until optimal agreement is achieved. The constitutive law used here is the Miller-Norton relationship, which covers both primary and secondary creep regimes (although the transition between them is not well-defined). The experimental outcome is the penetration depth as a function of time, under a constant applied load. An important feature of the procedure is the prior creation of a spherical recess in the sample, having a pre-selected depth and a curvature radius equal to that of the indenter. This allows control over the stress levels created during the indentation creep testing and can be used to ensure that no (time-independent) plastic deformation is stimulated during the test. In the absence of such a recess, this is virtually unavoidable, since the stress levels created during initial contact between a spherical indenter and a flat surface tend to be very high. Such plasticity introduces unwanted complications into creep testing. Confirmation of the viability of the procedure is provided via comparisons between the creep characteristics of pure nickel samples at 750 degrees C, obtained in this way and via conventional uniaxial tensile testing.