Abstract Understanding and linking mechanical properties obtained by spherical indentation experiments to uniaxial data is extremely challenging. Since the first attempts in the early 20th century numerous advances gradually allowed to expand the output of indentation tests. Still, the extraction of flow curves from spherical nanoindentation has not yet been fully established, as tip shape problems and size effects impede a straight-forward implementation. Within this study, we show new calibration procedures originating from fundamental geometrical considerations to account for tip shape imperfections. This sets the base for strain-rate controlled tests, which in turn enables us to measure rate-dependent material properties either with constant strain-rate or by strain-rate jump tests. Finally, experimental evaluation of the constraint factor in consideration of the mechanical properties and induced strain enables the extraction of flow curves. Testing materials with refined microstructures ensures the absence of possible size-effects. This study contributes to a significant improvement of current experimental protocols and allows to move flow curve measurements from single spherical imprints one step closer to its implementation as a standard characterization technique for modern materials.

中文翻译：

---

用于可靠确定机械流动曲线的球形纳米压痕方案的基本改进

摘要 理解球形压痕实验获得的机械性能并将其与单轴数据联系起来极具挑战性。自 20 世纪初首次尝试以来，许多进步逐渐扩大了压痕测试的产量。尽管如此，尚未完全建立从球形纳米压痕中提取流动曲线的方法，因为尖端形状问题和尺寸效应阻碍了直接实施。在这项研究中，我们展示了源自基本几何考虑的新校准程序，以解决尖端形状缺陷。这为应变率控制测试奠定了基础，这反过来又使我们能够以恒定应变率或应变率跳跃测试来测量与速率相关的材料特性。最后，考虑到机械性能和诱导应变的约束因子的实验评估能够提取流动曲线。具有精细微观结构的测试材料可确保不存在可能的尺寸效应。这项研究有助于显着改进当前的实验协议，并允许将流动曲线测量从单个球形印记移动一步，使其成为现代材料的标准表征技术。