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Indentation

About: Indentation is a research topic. Over the lifetime, 13002 publications have been published within this topic receiving 340476 citations.


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TL;DR: A fundamental understanding of basic tribological processes such as surface indentation and scraping was provided by Gane and Bowden as mentioned in this paper, who related this critical yielding to the theoretical shear strength in the metal, the strength required to create dislocations.
Abstract: The precision machining of metal surfaces and the ductile-regime grinding of ceramic surfaces are examples of fundamental cutting processes used in fabricating high-tolerance parts. Components with dimensional tolerances of a few tens of nanometers are currently being produced by direct machining with single-point diamond tools. Despite the ability to fabricate these parts, little is understood of the basic deformation mechanisms that determine how material is removed and deformed, how a tool-tip interacts with a workpiece, how induced surface and subsurface damage occurs, and how cutting tools wear.The key to solving these problems is a fundamental understanding of basic tribological processes such as surface indentation and scraping. Indentation experiments measure the mechanical response of a surface, the onset of plastic deformation, and material hardness. Macroscopic hardness measurements have been shown to correlate well with observed tensile yield strengths. Microscopic indentation studies, where the indentation size is smaller than the material grain size, show new and interesting phenomena. In the pioneering work of Gane and Bowden, no permanent penetration occurred until a critical load was achieved. They related this critical yielding to the theoretical shear strength in the metal, the strength required to create dislocations. Yielding of this sort has since been observed by many investigators.

75 citations

Journal ArticleDOI
TL;DR: A strong mechanical anisotropy of white matter in large strain is confirmed and the proposed asymmetric indentation technique is demonstrated to have the potential to characterize other soft biological tissues with transversely isotropic properties.
Abstract: Characterizing the mechanical properties of white matter is important to understand and model brain development and injury. With embedded aligned axonal fibers, white matter is typically modeled as a transversely isotropic material. However, most studies characterize the white matter tissue using models with a single anisotropic invariant or in a small-strain regime. In this study, we combined a single experimental procedure - asymmetric indentation - with inverse finite element (FE) modeling to estimate the nearly incompressible transversely isotropic material parameters of white matter. A minimal form comprising three parameters was employed to simulate indentation responses in the large-strain regime. The parameters were estimated using a global optimization procedure based on a genetic algorithm (GA). Experimental data from two indentation configurations of porcine white matter, parallel and perpendicular to the axonal fiber direction, were utilized to estimate model parameters. Results in this study confirmed a strong mechanical anisotropy of white matter in large strain. Further, our results suggested that both indentation configurations are needed to estimate the parameters with sufficient accuracy, and that the indenter-sample friction is important. Finally, we also showed that the estimated parameters were consistent with those previously obtained via a trial-and-error forward FE method in the small-strain regime. These findings are useful in modeling and parameterization of white matter, especially under large deformation, and demonstrate the potential of the proposed asymmetric indentation technique to characterize other soft biological tissues with transversely isotropic properties.

75 citations

Journal ArticleDOI
TL;DR: In this paper, a nonlinear force-indentation equation based on the Mooney-Rivlin model is derived and used to fit data from the indentation of lightly crosslinked poly(vinyl alcohol) gels in equilibrium with water.
Abstract: We exploit the force spectroscopy capabilities of the atomic force microscope in characterizing the local elastic- ity of rubber-like materials. Extraction of elastic properties from force curves usually relies on the linear theory pioneered by Hertz. While the Hertzian force-indentation relationships have been shown to be accurate in modeling the contact mechanics at sufficiently shallow indentation depths, the linear deformation regime of the probed material is exceeded in many practical applications of nanoindentation. In this article, a simple, nonlinear force-indentation equation based on the Mooney-Rivlin model is derived and used to fit data from the indentation of lightly crosslinked poly(vinyl alcohol) gels in equilibrium with water. The extracted values of Young's modulus show good agreement with those obtained by both macroscopic compression testing and by fitting truncated portions of the force curves with the Hertz equation.

75 citations

Journal ArticleDOI
TL;DR: In this paper, the authors examined the time-dependent deformation and flow for an axisymmetric indenter (flat-ended, spherical or conical indenter) penetrating into a viscoelastic body.
Abstract: The time-dependent deformation and flow are examined for an axisymmetric indenter (flat-ended, spherical or conical indenter) penetrating into a viscoelastic body. The analytical solutions for elastic contact combined with the Boltzmann hereditary integral lead to the constitutive equations for linear viscoelastic indentation. Some numerical analyses for simple models of viscoelastic liquid and solid are conducted to gain further rheological insights into indentation viscoelasticity. Indentation techniques provide the most efficient microprobes and nanoprobes for examining the time-dependent viscoelastic deformation and flow; testing specimens with extremely small dimensions and thin films with no special preparation, as well as compressive loading makes the test easier at elevated temperatures and in hostile environments.

75 citations

Journal ArticleDOI
TL;DR: In this paper, a one-dimensional constitutive relation between the change of the excessive free volume and the flow stress was proposed to explain the indentation-size effect as observed in the nanoindentation tests.

75 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023517
20221,124
2021457
2020510
2019566
2018526