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Special Issue "Advanced Nanoindentation in Materials"

A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: closed (30 May 2017)

Special Issue Editors

Guest Editor
Prof. Ting Tsui

Department of Chemical Engineering, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada
Website | E-Mail
Interests: nanoindentation; sub-micron fabrication; nanomechanics; thin film delaminations; integrate circuits; cell immobilization; morphology control of cells
Guest Editor
Prof. Matt Pharr

College of Engineering, Texas A&M University
Website | E-Mail

Special Issue Information

Dear Colleagues,

Over the past three decades, nanoindentation has emerged as an indispensable tool to characterize small-scale mechanical properties of a wide range of materials and nanostructures, such as integrated circuits, biological tissues, and porous materials. Considerable progress has been made since the mid-1980s to expand the capabilities of nanoindenter hardware and experiment methods. This enables investigators to measure thin film adhesion strength, fracture toughness, strain rate sensitivity, viscoelasticity, and creep deformation behaviors. Researchers also used nanoindentation techniques to examine deformation behaviors that are specimen size-dependent, such as dislocation starvation hardening in single-crystal pillars and the softening effect in nano-crystalline pillars. Furthermore, in situ SEM and TEM nanoindenters allow researchers to visualize mechanical deformations in real time. This Special Issue on Advanced Nanoindentation in Materials will provide a forum for researchers from the academic and industrial community to present the latest advances in the field of nanoindentation and small-scale mechanical properties of materials. In addition to metal, glass, and ceramic, this issue will include manuscripts focused on biological specimens. Topics of interest include, but are not limited to, the following:

  • Small scale facture
  • Nanoscale plasticity and creep
  • Size-dependent deformation phenomena
  • Deformation of biological cells
  • Mechanical properties of cellular and sub-cellular components
  • Novel mechanical property characterization techniques
  • New modeling methods
  • Environmentally controlled nanoindentation
  • In situ SEM and TEM indentation

Prof. Ting Tsui
Prof. Matt Pharr
Guest Editor

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1500 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • nanoindentation
  • creep
  • plasticity
  • instrumented indentation
  • hardness
  • modulus
  • strain rate sensitivity
  • fracture toughness
  • cells
  • viscoelasticity
  • soft materials

Published Papers (16 papers)

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Research

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Open AccessArticle A Novel Approach to Estimate the Plastic Anisotropy of Metallic Materials Using Cross-Sectional Indentation Applied to Extruded Magnesium Alloy AZ31B
Materials 2017, 10(9), 1065; doi:10.3390/ma10091065
Received: 21 July 2017 / Revised: 3 September 2017 / Accepted: 7 September 2017 / Published: 11 September 2017
Cited by 1 | PDF Full-text (7886 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, a methodology is presented for obtaining the plastic anisotropy of bulk metallic materials using cross-sectional indentation. This method relies on spherical indentation on the free edge of a specimen, and examining the out-of-plane residual deformation contour persisting on the cross-section
[...] Read more.
In this paper, a methodology is presented for obtaining the plastic anisotropy of bulk metallic materials using cross-sectional indentation. This method relies on spherical indentation on the free edge of a specimen, and examining the out-of-plane residual deformation contour persisting on the cross-section after unloading. Results obtained from numerical simulation revealed that some important aspects of the out-of-plane residual deformation field are only sensitive to the extent of the material plastic anisotropy, and insensitive to strain hardening, yield strain, elastic anisotropy, and the selected displacement threshold value. An explicit equation is presented to correlate the plastic anisotropy with the characteristic parameter of the bottom shape of residual deformation contour, and it is used to uniquely determine the material plastic anisotropy in cross-sectional indentation. Effectiveness of the proposed method is verified by application on magnesium alloy AZ31B, and the plastic anisotropy parameter obtained from indentation and uniaxial tests show good agreement. Full article
(This article belongs to the Special Issue Advanced Nanoindentation in Materials)
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Open AccessArticle Mechanical Contact Characteristics of PC3 Human Prostate Cancer Cells on Complex-Shaped Silicon Micropillars
Materials 2017, 10(8), 892; doi:10.3390/ma10080892
Received: 16 May 2017 / Revised: 17 July 2017 / Accepted: 26 July 2017 / Published: 2 August 2017
PDF Full-text (3098 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In this study we investigated the contact characteristics of human prostate cancer cells (PC3) on silicon micropillar arrays with complex shapes by using high-resolution confocal fluorescence microscopy techniques. These arrays consist of micropillars that are of various cross-sectional geometries which produce different deformation
[...] Read more.
In this study we investigated the contact characteristics of human prostate cancer cells (PC3) on silicon micropillar arrays with complex shapes by using high-resolution confocal fluorescence microscopy techniques. These arrays consist of micropillars that are of various cross-sectional geometries which produce different deformation profiles in adherent cells. Fluorescence micrographs reveal that some DAPI (4′,6-diamidino-2-phenylindole)-stained nuclei from cells attached to the pillars develop nanometer scale slits and contain low concentrations of DNA. The lengths of these slits, and their frequency of occurrence, were characterized for various cross-sectional geometries. These DNA-depleted features are only observed in locations below the pillar’s top surfaces. Results produced in this study indicate that surface topography can induce unique nanometer scale features in the PC3 cell. Full article
(This article belongs to the Special Issue Advanced Nanoindentation in Materials)
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Open AccessCommunication Micro-Mechanical Viscoelastic Properties of Crosslinked Hydrogels Using the Nano-Epsilon Dot Method
Materials 2017, 10(8), 889; doi:10.3390/ma10080889
Received: 6 July 2017 / Revised: 22 July 2017 / Accepted: 31 July 2017 / Published: 2 August 2017
PDF Full-text (1120 KB) | HTML Full-text | XML Full-text
Abstract
Engineering materials that recapitulate pathophysiological mechanical properties of native tissues in vitro is of interest for the development of biomimetic organ models. To date, the majority of studies have focused on designing hydrogels for cell cultures which mimic native tissue stiffness or quasi-static
[...] Read more.
Engineering materials that recapitulate pathophysiological mechanical properties of native tissues in vitro is of interest for the development of biomimetic organ models. To date, the majority of studies have focused on designing hydrogels for cell cultures which mimic native tissue stiffness or quasi-static elastic moduli through a variety of crosslinking strategies, while their viscoelastic (time-dependent) behavior has been largely ignored. To provide a more complete description of the biomechanical environment felt by cells, we focused on characterizing the micro-mechanical viscoelastic properties of crosslinked hydrogels at typical cell length scales. In particular, gelatin hydrogels crosslinked with different glutaraldehyde (GTA) concentrations were analyzed via nano-indentation tests using the nano-epsilon dot method. The experimental data were fitted to a Maxwell Standard Linear Solid model, showing that increasing GTA concentration results in increased instantaneous and equilibrium elastic moduli and in a higher characteristic relaxation time. Therefore, not only do gelatin hydrogels become stiffer with increasing crosslinker concentration (as reported in the literature), but there is also a concomitant change in their viscoelastic behavior towards a more elastic one. As the degree of crosslinking alters both the elastic and viscous behavior of hydrogels, caution should be taken when attributing cell response merely to substrate stiffness, as the two effects cannot be decoupled. Full article
(This article belongs to the Special Issue Advanced Nanoindentation in Materials)
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Open AccessArticle Influence of Microencapsulated Phase Change Material (PCM) Addition on (Micro) Mechanical Properties of Cement Paste
Materials 2017, 10(8), 863; doi:10.3390/ma10080863
Received: 10 July 2017 / Revised: 18 July 2017 / Accepted: 24 July 2017 / Published: 27 July 2017
Cited by 2 | PDF Full-text (5237 KB) | HTML Full-text | XML Full-text
Abstract
Excessive cracking can be a serious durability problem for reinforced concrete structures. In recent years, addition of microencapsulated phase change materials (PCMs) to concrete has been proposed as a possible solution to crack formation related to temperature gradients. However, the addition of PCM
[...] Read more.
Excessive cracking can be a serious durability problem for reinforced concrete structures. In recent years, addition of microencapsulated phase change materials (PCMs) to concrete has been proposed as a possible solution to crack formation related to temperature gradients. However, the addition of PCM microcapsules to cementitious materials can have some drawbacks, mainly related to strength reduction. In this work, a range of experimental techniques has been used to characterize the microcapsules and their effect on properties of composite cement pastes. On the capsule level, it was shown that they are spherical, enabling good distribution in the material during the mixing process. Force needed to break the microcapsules was shown to depend on the capsule diameter and the temperature, i.e., whether it is below or above the phase change temperature. On the cement paste level, a marked drop of compressive strength with increasing PCM inclusion level was observed. The indentation modulus has also shown to decrease, probably due to the capsules themselves, and to a lesser extent due to changes in porosity caused by their inclusion. Finally, a novel micro-cube splitting technique was used to characterize the tensile strength of the material on the micro-meter length scale. It was shown that the strength decreases with increasing PCM inclusion percentage, but this is accompanied by a decrease in measurement variability. This study will contribute to future developments of cementitious composites incorporating phase change materials for a variety of applications. Full article
(This article belongs to the Special Issue Advanced Nanoindentation in Materials)
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Open AccessArticle Characterisation of Asphalt Concrete Using Nanoindentation
Materials 2017, 10(7), 823; doi:10.3390/ma10070823
Received: 30 June 2017 / Revised: 13 July 2017 / Accepted: 17 July 2017 / Published: 18 July 2017
PDF Full-text (3107 KB) | HTML Full-text | XML Full-text
Abstract
In this study, nanoindentation was conducted to extract the load-displacement behaviour and the nanomechanical properties of asphalt concrete across the mastic, matrix, and aggregate phases. Further, the performance of hydrated lime as an additive was assessed across the three phases. The hydrated lime
[...] Read more.
In this study, nanoindentation was conducted to extract the load-displacement behaviour and the nanomechanical properties of asphalt concrete across the mastic, matrix, and aggregate phases. Further, the performance of hydrated lime as an additive was assessed across the three phases. The hydrated lime containing samples have greater resistance to deformation in the mastic and matrix phases, in particular, the mastic. There is strong evidence suggesting that hydrated lime has the most potent effect on the mastic phase, with significant increase in hardness and stiffness. Full article
(This article belongs to the Special Issue Advanced Nanoindentation in Materials)
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Open AccessArticle Using Biotechnology to Solve Engineering Problems: Non-Destructive Testing of Microfabrication Components
Materials 2017, 10(7), 788; doi:10.3390/ma10070788
Received: 31 May 2017 / Revised: 4 July 2017 / Accepted: 8 July 2017 / Published: 12 July 2017
PDF Full-text (4214 KB) | HTML Full-text | XML Full-text
Abstract
In an increasingly miniaturised technological world, non-destructive testing (NDT) methodologies able to detect defects at the micro scale are necessary to prevent failures. Although several existing methods allow the detection of defects at that scale, their application may be hindered by the small
[...] Read more.
In an increasingly miniaturised technological world, non-destructive testing (NDT) methodologies able to detect defects at the micro scale are necessary to prevent failures. Although several existing methods allow the detection of defects at that scale, their application may be hindered by the small size of the samples to examine. In this study, the application of bacterial cells to help the detection of fissures, cracks, and voids on the surface of metals is proposed. The application of magnetic and electric fields after deposition of the cells ensured the distribution of the cells over the entire surfaces and helped the penetration of the cells inside the defects. The use of fluorophores to stain the cells allowed their visualisation and the identification of the defects. Furthermore, the size and zeta potential of the cells and their production of siderophores and biosurfactants could be influenced to detect smaller defects. Micro and nano surface defects made in aluminium, steel, and copper alloys could be readily identified by two Staphylococcus strains and Rhodococcus erythropolis cells. Full article
(This article belongs to the Special Issue Advanced Nanoindentation in Materials)
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Open AccessArticle Full-Field Indentation Damage Measurement Using Digital Image Correlation
Materials 2017, 10(7), 774; doi:10.3390/ma10070774
Received: 2 June 2017 / Revised: 5 July 2017 / Accepted: 6 July 2017 / Published: 10 July 2017
PDF Full-text (6053 KB) | HTML Full-text | XML Full-text
Abstract
A novel approach based on full-field indentation measurements to characterize and quantify the effect of contact in thin plates is presented. The proposed method has been employed to evaluate the indentation damage generated in the presence of bending deformation, resulting from the contact
[...] Read more.
A novel approach based on full-field indentation measurements to characterize and quantify the effect of contact in thin plates is presented. The proposed method has been employed to evaluate the indentation damage generated in the presence of bending deformation, resulting from the contact between a thin plate and a rigid sphere. For this purpose, the 3D Digital Image Correlation (3D-DIC) technique has been adopted to quantify the out of plane displacements at the back face of the plate. Tests were conducted using aluminum thin plates and a rigid bearing sphere to evaluate the influence of the thickness and the material behavior during contact. Information provided by the 3D-DIC technique has been employed to perform an indirect measurement of the contact area during the loading and unloading path of the test. A symmetrical distribution in the contact damage region due to the symmetry of the indenter was always observed. In the case of aluminum plates, the presence of a high level of plasticity caused shearing deformation as the load increased. Results show the full-field contact damage area for different plates’ thicknesses at different loads. The contact damage region was bigger when the thickness of the specimen increased, and therefore, bending deformation was reduced. With the proposed approach, the elastic recovery at the contact location was quantified during the unloading, as well as the remaining permanent indentation damage after releasing the load. Results show the information obtained by full-field measurements at the contact location during the test, which implies a substantial improvement compared with pointwise techniques. Full article
(This article belongs to the Special Issue Advanced Nanoindentation in Materials)
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Open AccessArticle A Validation Approach for Quasistatic Numerical/Experimental Indentation Analysis in Soft Materials Using 3D Digital Image Correlation
Materials 2017, 10(7), 722; doi:10.3390/ma10070722
Received: 29 May 2017 / Revised: 20 June 2017 / Accepted: 23 June 2017 / Published: 28 June 2017
PDF Full-text (4684 KB) | HTML Full-text | XML Full-text
Abstract
A quasistatic indentation numerical analysis in a round section specimen made of soft material has been performed and validated with a full field experimental technique, i.e., Digital Image Correlation 3D. The contact experiment specifically consisted of loading a 25 mm diameter rubber cylinder
[...] Read more.
A quasistatic indentation numerical analysis in a round section specimen made of soft material has been performed and validated with a full field experimental technique, i.e., Digital Image Correlation 3D. The contact experiment specifically consisted of loading a 25 mm diameter rubber cylinder of up to a 5 mm indentation and then unloading. Experimental strains fields measured at the surface of the specimen during the experiment were compared with those obtained by performing two numerical analyses employing two different hyperplastic material models. The comparison was performed using an Image Decomposition new methodology that makes a direct comparison of full-field data independently of their scale or orientation possible. Numerical results show a good level of agreement with those measured during the experiments. However, since image decomposition allows for the differences to be quantified, it was observed that one of the adopted material models reproduces lower differences compared to experimental results. Full article
(This article belongs to the Special Issue Advanced Nanoindentation in Materials)
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Open AccessArticle Effect of Applied Stress on the Mechanical Properties of a Zr-Cu-Ag-Al Bulk Metallic Glass with Two Different Structure States
Materials 2017, 10(7), 711; doi:10.3390/ma10070711
Received: 5 June 2017 / Revised: 16 June 2017 / Accepted: 21 June 2017 / Published: 27 June 2017
Cited by 1 | PDF Full-text (3989 KB) | HTML Full-text | XML Full-text
Abstract
In order to investigate the effect of applied stress on mechanical properties in metallic glasses, nanoindentation tests were conducted on elastically bent Zr-Cu-Ag-Al metallic glasses with two different structure states. From spherical P-h curves, elastic modulus was found to be independent on applied
[...] Read more.
In order to investigate the effect of applied stress on mechanical properties in metallic glasses, nanoindentation tests were conducted on elastically bent Zr-Cu-Ag-Al metallic glasses with two different structure states. From spherical P-h curves, elastic modulus was found to be independent on applied stress. Hardness decreased by ~8% and ~14% with the application of 1.5% tensile strain for as-cast and 650 K annealed specimens, while it was slightly increased at the compressive side. Yield stress could be obtained from the contact pressure at first pop-in position with a conversion coefficient. The experimental result showed a symmetrical effect of applied stress on strengthening and a reduction of the contact pressure at compressive and tensile sides. It was observed that the applied stress plays a negligible effect on creep deformation in as-cast specimen. While for the annealed specimen, creep deformation was facilitated by applied tensile stress and suppressed by applied compressive stress. Strain rate sensitivities (SRS) were calculated from steady-state creep, which were constant for as-cast specimen and strongly correlated with applied stress for the annealed one. The more pronounced effect of applied stress in the 650 K annealed metallic glass could be qualitatively explained through the variation of the shear transformation zone (STZ) size. Full article
(This article belongs to the Special Issue Advanced Nanoindentation in Materials)
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Open AccessArticle Material Flow Analysis in Indentation by Two-Dimensional Digital Image Correlation and Finite Elements Method
Materials 2017, 10(6), 674; doi:10.3390/ma10060674
Received: 15 May 2017 / Revised: 14 June 2017 / Accepted: 16 June 2017 / Published: 21 June 2017
PDF Full-text (11282 KB) | HTML Full-text | XML Full-text
Abstract
The present work shows the material flow analysis in indentation by the numerical two dimensional Finite Elements (FEM) method and the experimental two-dimensional Digital Image Correlation (DIC) method. To achieve deep indentation without cracking, a ductile material, 99% tin, is used. The results
[...] Read more.
The present work shows the material flow analysis in indentation by the numerical two dimensional Finite Elements (FEM) method and the experimental two-dimensional Digital Image Correlation (DIC) method. To achieve deep indentation without cracking, a ductile material, 99% tin, is used. The results obtained from the DIC technique depend predominantly on the pattern conferred to the samples. Due to the absence of a natural pattern, black and white spray painting is used for greater contrast. The stress-strain curve of the material has been obtained and introduced in the Finite Element simulation code used, DEFORM™, allowing for accurate simulations. Two different 2D models have been used: a plain strain model to obtain the load curve and a plain stress model to evaluate the strain maps on the workpiece surface. The indentation displacement load curve has been compared between the FEM and the experimental results, showing a good correlation. Additionally, the strain maps obtained from the material surface with FEM and DIC are compared in order to validate the numerical model. The Von Mises strain results between both of them present a 10–20% difference. The results show that FEM is a good tool for simulating indentation processes, allowing for the evaluation of the maximum forces and deformations involved in the forming process. Additionally, the non-contact DIC technique shows its potential by measuring the superficial strain maps, validating the FEM results. Full article
(This article belongs to the Special Issue Advanced Nanoindentation in Materials)
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Open AccessFeature PaperArticle Ultra High Strain Rate Nanoindentation Testing
Materials 2017, 10(6), 663; doi:10.3390/ma10060663
Received: 20 May 2017 / Revised: 13 June 2017 / Accepted: 14 June 2017 / Published: 17 June 2017
Cited by 2 | PDF Full-text (4005 KB) | HTML Full-text | XML Full-text
Abstract
Strain rate dependence of indentation hardness has been widely used to study time-dependent plasticity. However, the currently available techniques limit the range of strain rates that can be achieved during indentation testing. Recent advances in electronics have enabled nanomechanical measurements with very low
[...] Read more.
Strain rate dependence of indentation hardness has been widely used to study time-dependent plasticity. However, the currently available techniques limit the range of strain rates that can be achieved during indentation testing. Recent advances in electronics have enabled nanomechanical measurements with very low noise levels (sub nanometer) at fast time constants (20 µs) and high data acquisition rates (100 KHz). These capabilities open the doors for a wide range of ultra-fast nanomechanical testing, for instance, indentation testing at very high strain rates. With an accurate dynamic model and an instrument with fast time constants, step load tests can be performed which enable access to indentation strain rates approaching ballistic levels (i.e., 4000 1/s). A novel indentation based testing technique involving a combination of step load and constant load and hold tests that enables measurement of strain rate dependence of hardness spanning over seven orders of magnitude in strain rate is presented. A simple analysis is used to calculate the equivalent uniaxial response from indentation data and compared to the conventional uniaxial data for commercial purity aluminum. Excellent agreement is found between the indentation and uniaxial data over several orders of magnitude of strain rate. Full article
(This article belongs to the Special Issue Advanced Nanoindentation in Materials)
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Open AccessArticle Hardening Effect Analysis by Modular Upper Bound and Finite Element Methods in Indentation of Aluminum, Steel, Titanium and Superalloys
Materials 2017, 10(5), 556; doi:10.3390/ma10050556
Received: 29 March 2017 / Revised: 9 May 2017 / Accepted: 17 May 2017 / Published: 19 May 2017
PDF Full-text (7990 KB) | HTML Full-text | XML Full-text
Abstract
The application of incremental processes in the manufacturing industry is having a great development in recent years. The first stage of an Incremental Forming Process can be defined as an indentation. Because of this, the indentation process is starting to be widely studied,
[...] Read more.
The application of incremental processes in the manufacturing industry is having a great development in recent years. The first stage of an Incremental Forming Process can be defined as an indentation. Because of this, the indentation process is starting to be widely studied, not only as a hardening test but also as a forming process. Thus, in this work, an analysis of the indentation process under the new Modular Upper Bound perspective has been performed. The modular implementation has several advantages, including the possibility of the introduction of different parameters to extend the study, such as the friction effect, the temperature or the hardening effect studied in this paper. The main objective of the present work is to analyze the three hardening models developed depending on the material characteristics. In order to support the validation of the hardening models, finite element analyses of diverse materials under an indentation are carried out. Results obtained from the Modular Upper Bound are in concordance with the results obtained from the numerical analyses. In addition, the numerical and analytical methods are in concordance with the results previously obtained in the experimental indentation of annealed aluminum A92030. Due to the introduction of the hardening factor, the new modular distribution is a suitable option for the analysis of indentation process. Full article
(This article belongs to the Special Issue Advanced Nanoindentation in Materials)
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Open AccessArticle Investigation on Indentation Cracking-Based Approaches for Residual Stress Evaluation
Materials 2017, 10(4), 404; doi:10.3390/ma10040404
Received: 14 March 2017 / Revised: 5 April 2017 / Accepted: 6 April 2017 / Published: 12 April 2017
PDF Full-text (3785 KB) | HTML Full-text | XML Full-text
Abstract
Vickers indentation fracture can be used to estimate equibiaxial residual stresses (RS) in brittle materials. Previous, conceptually-equal, analytical models were established on the assumptions that (i) the crack be of a semi-circular shape and (ii) that the shape not be affected by RS.
[...] Read more.
Vickers indentation fracture can be used to estimate equibiaxial residual stresses (RS) in brittle materials. Previous, conceptually-equal, analytical models were established on the assumptions that (i) the crack be of a semi-circular shape and (ii) that the shape not be affected by RS. A generalized analytical model that accounts for the crack shape and its change is presented. To assess these analytical models and to gain detailed insight into the crack evolution, an extended finite element (XFE) model is established. XFE analysis results show that the crack shape is generally not semi-circular and affected by RS and that tensile and compressive RS have different effects on the crack evolution. Parameter studies are performed to calibrate the generalized analytical model. Comparison of the results calculated by the analytical models with XFE results reveals the inaccuracy inherent in the previous analytical models, namely the neglect of (the change of) the crack aspect-ratio, in particular for tensile RS. Previous models should therefore be treated with caution and, if at all, used only for compressive RS. The generalized model, on the other hand, gives a more accurate description of the RS, but requires the crack depth. Full article
(This article belongs to the Special Issue Advanced Nanoindentation in Materials)
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Open AccessArticle A Comparison of Microscale Techniques for Determining Fracture Toughness of LiMn2O4 Particles
Materials 2017, 10(4), 403; doi:10.3390/ma10040403
Received: 14 March 2017 / Revised: 4 April 2017 / Accepted: 7 April 2017 / Published: 12 April 2017
Cited by 1 | PDF Full-text (4436 KB) | HTML Full-text | XML Full-text
Abstract
Accurate estimation of fracture behavior of commercial LiMn2O4 particles is of great importance to predict the performance and lifetime of a battery. The present study compares two different microscale techniques to quantify the fracture toughness of LiMn2O4
[...] Read more.
Accurate estimation of fracture behavior of commercial LiMn2O4 particles is of great importance to predict the performance and lifetime of a battery. The present study compares two different microscale techniques to quantify the fracture toughness of LiMn2O4 particles embedded in an epoxy matrix. The first technique uses focused ion beam (FIB) milled micro pillars that are subsequently tested using the nanoindentation technique. The pillar geometry, critical load at pillar failure, and cohesive FEM simulations are then used to compute the fracture toughness. The second technique relies on the use of atomic force microscopy (AFM) to measure the crack opening displacement (COD) and subsequent application of Irwin’s near field theory to measure the mode-I crack tip toughness of the material. Results show pillar splitting method provides a fracture toughness value of ~0.24 MPa.m1/2, while COD measurements give a crack tip toughness of ~0.81 MPa.m1/2. The comparison of fracture toughness values with the estimated value on the reference LiMn2O4 wafer reveals that micro pillar technique provides measurements that are more reliable than the COD method. The difference is associated with ease of experimental setup, calculation simplicity, and little or no influence of external factors as associated with the COD measurements. Full article
(This article belongs to the Special Issue Advanced Nanoindentation in Materials)
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Open AccessArticle Effect of the Elastic Deformation of a Point-Sharp Indenter on Nanoindentation Behavior
Materials 2017, 10(3), 270; doi:10.3390/ma10030270
Received: 25 January 2017 / Accepted: 2 March 2017 / Published: 7 March 2017
Cited by 2 | PDF Full-text (2935 KB) | HTML Full-text | XML Full-text
Abstract
The effect of the elastic deformation of a point-sharp indenter on the relationship between the indentation load P and penetration depth h (P-h curve) is examined through the numerical analysis of conical indentations simulated with the finite element method [...] Full article
(This article belongs to the Special Issue Advanced Nanoindentation in Materials)
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Review

Jump to: Research

Open AccessFeature PaperReview Micro-Mechanical Response of an Al-Mg Hybrid System Synthesized by High-Pressure Torsion
Materials 2017, 10(6), 596; doi:10.3390/ma10060596
Received: 10 May 2017 / Revised: 26 May 2017 / Accepted: 27 May 2017 / Published: 30 May 2017
PDF Full-text (4363 KB) | HTML Full-text | XML Full-text
Abstract
This paper summarizes recent efforts to evaluate the potential for the formation of a metal matrix nanocomposite (MMNC) by processing two commercial bulk metals of aluminum and magnesium alloy through high-pressure torsion (HPT) at room temperature. After significant evolutions in microstructures, successful fabrication
[...] Read more.
This paper summarizes recent efforts to evaluate the potential for the formation of a metal matrix nanocomposite (MMNC) by processing two commercial bulk metals of aluminum and magnesium alloy through high-pressure torsion (HPT) at room temperature. After significant evolutions in microstructures, successful fabrication of an Al-Mg hybrid system was demonstrated by observing unique microstructures consisting of a multi-layered structure and MMNC. Moreover, the evolution of small-scale mechanical properties was examined through the novel technique of nanoindentation and the improvement in plasticity was estimated by calculating the strain rate sensitivity of the Al-Mg hybrid system after HPT. The present paper demonstrates that, in addition to conventional tensile testing, the nanoindentation technique is exceptionally promising for ultrafine-grained materials processed by HPT, where the samples may have small overall dimensions and include heterogeneity in the microstructure. Full article
(This article belongs to the Special Issue Advanced Nanoindentation in Materials)
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