The Experts below are selected from a list of 16680 Experts worldwide ranked by ideXlab platform
W. L. Elban - One of the best experts on this subject based on the ideXlab platform.
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Crystal Indentation Hardness
Crystals, 2017Co-Authors: R. W. Armstrong, Stephen M. Walley, W. L. ElbanAbstract:There is expanded interest in the long-standing subject of the Hardness properties of materials. A major part of such interest is due to the advent of nanoIndentation Hardness testing systems which have made available orders of magnitude increases in load and displacement measuring capabilities achieved in a continuously recorded test procedure. The new results have been smoothly merged with other advances in conventional Hardness testing and with parallel developments in improved model descriptions of both elastic contact mechanics and dislocation mechanisms operative in the understanding of crystal plasticity and fracturing behaviors. No crystal is either too soft or too hard to prevent the determination of its elastic, plastic and cracking properties under a suitable probing indenter. A sampling of the wealth of measurements and reported analyses associated with the topic on a wide variety of materials are presented in the current Special Issue.
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Macro- to Nano-Indentation Hardness Stress–Strain Aspects of Crystal Elastic/Plastic/Cracking Behaviors
Experimental Mechanics, 2010Co-Authors: R. W. Armstrong, W. L. ElbanAbstract:Single crystal KCl and MgO Indentation Hardness test results spanning macroscopic, microstructural, and nanoscale measurements are brought together in a ball-indenter-based stress–strain description. For a significant range of Hardness measurements made on MgO (001) crystal surfaces, increasingly greater plastic flow stresses are determined at smaller loads applied to smaller effective ball sizes at the rounded tips of Berkovich indenters; and, at the smallest ball diameters of 3,200 nm and 400 nm, the plastic flow stresses are shown to approach the predicted Hertzian elastic loading stresses. The resultant Hardness stress–strain description, that is extended to cover the elastic, plastic, and cracking behaviors of MgO crystals, is usefully applied also to a comparison of Indentation test results reported for NaCl and RDX crystals. In general, the dislocation-induced cracking stress measurements are shown for MgO and RDX crystals to be lower than cracking stresses evaluated on an (elastic) Indentation fracture mechanics (IFM) basis. Comparison is made with metal nanoIndentation Hardness test results.
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Indentation Hardness Stress - Strain Aspects of Crystal Elastic/Plastic/Cracking Behaviors
2008Co-Authors: R. W. Armstrong, W. L. ElbanAbstract:Single crystal KCl and MgO Indentation Hardness test results spanning macroscopic, microstructural, and nanoscale measurements are brought together in a ball-indenterbased stress-strain description. For a significant range of Hardness measurements made on MgO (001) crystal surfaces, increasingly greater plastic flow stresses are determined at smaller loads applied to smaller effective ball sizes at the rounded tips of Berkovich indenters; and, at the smallest ball diameters of 3200 and 400 nm, the plastic flow stresses are shown to approach the predicted Hertzian elastic loading stresses. The resultant Hardness stress – strain description, that is extended to cover the elastic, plastic, and cracking behaviors of MgO crystals, is usefully applied also to a comparison of Indentation test results reported for NaCl and RDX crystals. In general, the dislocationinduced cracking stress measurements are shown for MgO and RDX crystals to be lower than cracking stresses evaluated on an (elastic) Indentation fracture mechanics (IFM) basis.
R. W. Armstrong - One of the best experts on this subject based on the ideXlab platform.
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Crystal Indentation Hardness
Crystals, 2017Co-Authors: R. W. Armstrong, Stephen M. Walley, W. L. ElbanAbstract:There is expanded interest in the long-standing subject of the Hardness properties of materials. A major part of such interest is due to the advent of nanoIndentation Hardness testing systems which have made available orders of magnitude increases in load and displacement measuring capabilities achieved in a continuously recorded test procedure. The new results have been smoothly merged with other advances in conventional Hardness testing and with parallel developments in improved model descriptions of both elastic contact mechanics and dislocation mechanisms operative in the understanding of crystal plasticity and fracturing behaviors. No crystal is either too soft or too hard to prevent the determination of its elastic, plastic and cracking properties under a suitable probing indenter. A sampling of the wealth of measurements and reported analyses associated with the topic on a wide variety of materials are presented in the current Special Issue.
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Macro- to Nano-Indentation Hardness Stress–Strain Aspects of Crystal Elastic/Plastic/Cracking Behaviors
Experimental Mechanics, 2010Co-Authors: R. W. Armstrong, W. L. ElbanAbstract:Single crystal KCl and MgO Indentation Hardness test results spanning macroscopic, microstructural, and nanoscale measurements are brought together in a ball-indenter-based stress–strain description. For a significant range of Hardness measurements made on MgO (001) crystal surfaces, increasingly greater plastic flow stresses are determined at smaller loads applied to smaller effective ball sizes at the rounded tips of Berkovich indenters; and, at the smallest ball diameters of 3,200 nm and 400 nm, the plastic flow stresses are shown to approach the predicted Hertzian elastic loading stresses. The resultant Hardness stress–strain description, that is extended to cover the elastic, plastic, and cracking behaviors of MgO crystals, is usefully applied also to a comparison of Indentation test results reported for NaCl and RDX crystals. In general, the dislocation-induced cracking stress measurements are shown for MgO and RDX crystals to be lower than cracking stresses evaluated on an (elastic) Indentation fracture mechanics (IFM) basis. Comparison is made with metal nanoIndentation Hardness test results.
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Indentation Hardness Stress - Strain Aspects of Crystal Elastic/Plastic/Cracking Behaviors
2008Co-Authors: R. W. Armstrong, W. L. ElbanAbstract:Single crystal KCl and MgO Indentation Hardness test results spanning macroscopic, microstructural, and nanoscale measurements are brought together in a ball-indenterbased stress-strain description. For a significant range of Hardness measurements made on MgO (001) crystal surfaces, increasingly greater plastic flow stresses are determined at smaller loads applied to smaller effective ball sizes at the rounded tips of Berkovich indenters; and, at the smallest ball diameters of 3200 and 400 nm, the plastic flow stresses are shown to approach the predicted Hertzian elastic loading stresses. The resultant Hardness stress – strain description, that is extended to cover the elastic, plastic, and cracking behaviors of MgO crystals, is usefully applied also to a comparison of Indentation test results reported for NaCl and RDX crystals. In general, the dislocationinduced cracking stress measurements are shown for MgO and RDX crystals to be lower than cracking stresses evaluated on an (elastic) Indentation fracture mechanics (IFM) basis.
D. J. - One of the best experts on this subject based on the ideXlab platform.
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the influence of crack forms on Indentation Hardness test results for ceramic materials
Journal of Materials Science, 2015Co-Authors: D. J.Abstract:In this work, the influence of crack forms [radial crack (RC) and half-penny crack (HPC)] on Indentation Hardness test results of ceramic materials (W e/W t = 0.3–0.7) was studied by finite element analysis and verified by experiments. Excluding the influence of size effect, the values of HPC and RC Indentation Hardness from instrumented Indentation tests on five ceramic materials (Si3N4, ZrO2, ZTA, Al2O3, and silica) were compared with that of “Non-Crack” Indentation Hardness. The results show that the influence of RC or HPC on Indentation Hardness test results of isotropic and homogeneous ceramic materials is verified to be negligible, both analytically and experimentally. But the “Pop-in phenomenon” is found to have a great impact on Indentation Hardness test results for ceramic materials. Therefore, in the absence of “Pop-in phenomenon,” the test results of Indentation Hardness of ceramic materials were practically reliable. This work provides a theoretical foundation for further study on instrumented Indentation for determining the elastic–plastic properties and fracture toughness of ceramic materials.
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the influence of crack forms on Indentation Hardness test results for ceramic materials
Journal of Materials Science, 2015Co-Authors: Jian Wang, D. J.Abstract:In this work, the influence of crack forms [radial crack (RC) and half-penny crack (HPC)] on Indentation Hardness test results of ceramic materials (W e/W t = 0.3–0.7) was studied by finite element analysis and verified by experiments. Excluding the influence of size effect, the values of HPC and RC Indentation Hardness from instrumented Indentation tests on five ceramic materials (Si3N4, ZrO2, ZTA, Al2O3, and silica) were compared with that of “Non-Crack” Indentation Hardness. The results show that the influence of RC or HPC on Indentation Hardness test results of isotropic and homogeneous ceramic materials is verified to be negligible, both analytically and experimentally. But the “Pop-in phenomenon” is found to have a great impact on Indentation Hardness test results for ceramic materials. Therefore, in the absence of “Pop-in phenomenon,” the test results of Indentation Hardness of ceramic materials were practically reliable. This work provides a theoretical foundation for further study on instrumented Indentation for determining the elastic–plastic properties and fracture toughness of ceramic materials.
Yingxue Yao - One of the best experts on this subject based on the ideXlab platform.
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Experimental Research on the Influence of Indenter Tip Radius to Indentation Hardness
Applied Mechanics and Materials, 2007Co-Authors: Liang Zhou, Yingxue Yao, Qiang LiuAbstract:Aiming at the influence law of indenter tip radius to Indentation Hardness, testing on the Hardness of single-crystal silicon was carried out based on nanoIndentation technique. Two kinds of Berkovich indenter with radius 40nm and 60nm separately were used in this experiment. According to the load-depth curve, the Hardness of single-crystal silicon was achieved by Oliver-Pharr method. Experimental results are presented which show that indenter tip radius influence the Hardness, the Hardness value increases and the Indentation size effect becomes obvious with the increasing of tip radius under same Indentation depth.
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Single crystal bulk material micro/nano Indentation Hardness testing by nanoIndentation instrument and AFM
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007Co-Authors: Liang Zhou, Yingxue YaoAbstract:Abstract The micro/nano Indentation Hardness of single crystal aluminium and single crystal silicon are investigated. Load–depth curves can be obtained by nanoIndentation instrument, and materials Indentation Hardness can be calculated by Oliver–Pharr method and work of Indentation method directly from these curves. The Hardness that obtained by Oliver–Pharr method is overestimate because of material pile-up effect, and the Hardness that obtained by work of Indentation method is not very correct because of its empirical equations inaccurate. The ‘true’ Hardness can be calculated by plastic work of Indentation and plastic volume that obtained by integrating fitted polynomial according to load–depth curves and atomic force microscopy, respectively. Comparison and analysis of the results that obtained by these methods are made.
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single crystal bulk material micro nano Indentation Hardness testing by nanoIndentation instrument and afm
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007Co-Authors: Liang Zhou, Yingxue YaoAbstract:Abstract The micro/nano Indentation Hardness of single crystal aluminium and single crystal silicon are investigated. Load–depth curves can be obtained by nanoIndentation instrument, and materials Indentation Hardness can be calculated by Oliver–Pharr method and work of Indentation method directly from these curves. The Hardness that obtained by Oliver–Pharr method is overestimate because of material pile-up effect, and the Hardness that obtained by work of Indentation method is not very correct because of its empirical equations inaccurate. The ‘true’ Hardness can be calculated by plastic work of Indentation and plastic volume that obtained by integrating fitted polynomial according to load–depth curves and atomic force microscopy, respectively. Comparison and analysis of the results that obtained by these methods are made.
Liang Zhou - One of the best experts on this subject based on the ideXlab platform.
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Experimental Research on the Influence of Indenter Tip Radius to Indentation Hardness
Applied Mechanics and Materials, 2007Co-Authors: Liang Zhou, Yingxue Yao, Qiang LiuAbstract:Aiming at the influence law of indenter tip radius to Indentation Hardness, testing on the Hardness of single-crystal silicon was carried out based on nanoIndentation technique. Two kinds of Berkovich indenter with radius 40nm and 60nm separately were used in this experiment. According to the load-depth curve, the Hardness of single-crystal silicon was achieved by Oliver-Pharr method. Experimental results are presented which show that indenter tip radius influence the Hardness, the Hardness value increases and the Indentation size effect becomes obvious with the increasing of tip radius under same Indentation depth.
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Single crystal bulk material micro/nano Indentation Hardness testing by nanoIndentation instrument and AFM
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007Co-Authors: Liang Zhou, Yingxue YaoAbstract:Abstract The micro/nano Indentation Hardness of single crystal aluminium and single crystal silicon are investigated. Load–depth curves can be obtained by nanoIndentation instrument, and materials Indentation Hardness can be calculated by Oliver–Pharr method and work of Indentation method directly from these curves. The Hardness that obtained by Oliver–Pharr method is overestimate because of material pile-up effect, and the Hardness that obtained by work of Indentation method is not very correct because of its empirical equations inaccurate. The ‘true’ Hardness can be calculated by plastic work of Indentation and plastic volume that obtained by integrating fitted polynomial according to load–depth curves and atomic force microscopy, respectively. Comparison and analysis of the results that obtained by these methods are made.
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single crystal bulk material micro nano Indentation Hardness testing by nanoIndentation instrument and afm
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007Co-Authors: Liang Zhou, Yingxue YaoAbstract:Abstract The micro/nano Indentation Hardness of single crystal aluminium and single crystal silicon are investigated. Load–depth curves can be obtained by nanoIndentation instrument, and materials Indentation Hardness can be calculated by Oliver–Pharr method and work of Indentation method directly from these curves. The Hardness that obtained by Oliver–Pharr method is overestimate because of material pile-up effect, and the Hardness that obtained by work of Indentation method is not very correct because of its empirical equations inaccurate. The ‘true’ Hardness can be calculated by plastic work of Indentation and plastic volume that obtained by integrating fitted polynomial according to load–depth curves and atomic force microscopy, respectively. Comparison and analysis of the results that obtained by these methods are made.
