Nanoindentation Device Research Articles

Machine learning approach to predicting the macro-mechanical properties of rock from the meso-mechanical parameters

The determination of fundamental rock mechanical properties, uniaxial compression strength (UCS) and elastic modulus (E), constitutes a pivotal facet of rock engineering design. However, deriving these properties directly from standard laboratory tests on rock core samples can be challenging, especially when dealing with deep high-stress rock formations and weak fractured strata. Thus, it is crucial to establish a cost-effective and practical approach for predicting the macro-mechanical properties of rocks in situ. In this study, a machine learning approach was proposed to predict UCS and E by upscaling meso-mechanical parameters at particle scale in low-porosity crystalline rocks. To expand the correlation database of rock meso-macro mechanical properties, the meso-mechanical parameters, including the fracture toughness, tensile strength of the rock crystal interface, and the elastic modulus of rock crystal, were accurately measured, using a newly designed mechanical apparatus and a nanoindentation device. The grain-based models implemented in the combined finite discrete element method (FDEM-GBM) were developed based on these experimental results, and their reliability was validated though standard tests. Subsequently, a database, including 225 groups of data, was established using the numerical method. Five machine learning algorithms were applied to develop prediction models for UCS and E through data training in the database. Excellent performance improvement was achieved through the application of the grid-search method. The results indicate the optimized kernel ridge regression (KRR) and gaussian process regression (GPR) models demonstrated excellent performance with relative average errors of 4.9% and 1.1% in predicting UCS and E, respectively. Finally, the predicted values of UCS and E were compared with the experimental results, validating the feasibility of the optimized KRR and GPR models.

Characteristics of TiN Thin Films Deposited by Substrate Temperature Variables Using Scanning Acoustic Microscopy

In this study, TiN thin films fabricated based on the substrate temperature process parameters of a DC magnetron sputtering device and their characteristics are analyzed. TiN thin films are deposited on Si wafer (100) substrates by setting the substrate temperatures to ambient temperature, 100, 200, and 300 °C. The residual stress measurement using the XRD method, adhesion characteristic analysis performed using a nanoscratch test to measure the critical load of the nanoindentation device, and leaky surface acoustic wave (LSAW) measurement were conducted using the V(z) technique of the ultrasonic microscope; the correlations between each measurement were analyzed. The residual stress of the TiN thin film was relieved by up to approximately 48% and adhesion properties enhanced by approximately 10% with an increase in the substrate temperature. In addition, the velocity of the LSAW presented a tendency to increase by up to approximately 5%. The residual stress and velocity of the LSAW were found to be inversely proportional, while the critical load and velocity of the LSAW were directly proportional.

Correlation between thermo-mechanical properties and network structure in Pb-As2S3 quasibinar chalcogenides

This paper is concerned with establishing the correlation between some mechanical, thermal and structural properties of Pbx(As2S3)100-x glassy samples, x = 1, 2 and 3 at.%. Measurements of mechanical parameters were performed using a Fischerscope HM2000 S nanoindentation device. The obtained results indicated decrease in the microhardness as a function of the doping element content, as well as a pronounced normal indentation size effect (ISE) phenomenon in the range of lower indentation loads. In order to describe the microhardness data in the ISE regime and to determine the load independent microhardness value, the MPRS model was used. The increase in glass transition temperature with heating rate observed in DSC curves was described according to the Lasocka equation. The activation energy of softening process was evaluated using the Kissinger?s method. The KAS model was applied to estimate the activation energy as a function of the conversion rate. Raman measurements were employed to investigate structural changes due to Pb doping.

Hollow Microcapsules with Controlled Mechanical Properties Templated from Pickering Emulsion Droplets

AbstractHollow microcapsules with controlled mechanical strength are obtained from Pickering emulsion templates. The shell of the hollow microcapsules comprising UV‐curable resin and reactive silica nanoparticles enables tuning of the mechanical properties in a controlled manner. The results show that the particle stabilizer can be packed regularly on the oil–water interface and the shell thickness of microcapsules can be increased to 1–2 µm compared with traditional preparation methods. Hollow particles with thicker walls can prevent collapse and breakage. In this work, a nanoindentation device is used to measure the mechanical properties of hollow particles, and the results show a clear trend of reduced modulus and hardness decreases with increasing ratio of prepolymers in the reaction mixture. When the mass of PUA varies from 10% to 30%, the hardness decreases from 0.09 to 0.04 GPa, while the reduced modulus decreases from 0.17 to 0.06 GPa. The control of mechanical properties of the microcapsule can enhance its uses in conventional areas as well as in new fields such as precise micro force sensors etc.

Mechanical characterization of diesel soot nanoparticles: in situ compression in a transmission electron microscope and simulations

Incomplete fuel burning inside an internal combustion engine results in the creation of soot in the form of nanoparticles. Some of these soot nanoparticles (SNP) become adsorbed into the lubricating oil film present on the cylinder walls, which adversely affects the tribological performance of the lubricant. In order to better understand the mechanisms underlying the wear caused by SNPs, it is important to understand the behavior of SNPs and to characterize potential changes in their mechanical properties (e.g. hardness) caused by (or during) mechanical stress. In this study, the behavior of individual SNPs originating from diesel engines was studied under compression. The experiments were performed in a transmission electron microscope using a nanoindentation device. The nanoparticles exhibited elasto-plastic behavior in response to consecutive compression cycles. From the experimental data, the Young’s modulus and hardness of the SNPs were calculated. The Young’s modulus and hardness of the nanoparticles increased with the number of compression cycles. Using an electron energy loss spectroscopy technique, it was shown that the sp2/sp3 ratio within the compressed nanoparticle decreases, which is suggested to be the cause of the increase in elasticity and hardness. In order to corroborate the experimental findings, molecular dynamics simulations of a model SNP were performed. The SNP model was constructed using carbon and hydrogen atoms with morphology and composition comparable to those observed in the experiment. The model SNP was subjected to repeated compressions between two virtual rigid walls. During the simulation, the nanoparticle exhibited elasto-plastic behavior like that in the experiments. The results of the simulations confirm that the increase in the elastic modulus and hardness is associated with a decrease in the sp2/sp3 ratio.

High temperature impact testing of a thin hard coating using a novel high-frequency in situ micromechanical device

High-impact applications such as forging, punching or fine blanking often utilise hard-coating systems to improve wear and lifetime performance. For rational design of such systems, evaluation after repeated impacts at the application temperature is critical. However, such investigations are time-consuming and costly to perform in-line on an industrial scale. Small-scale impact testing allows for rapid and inexpensive investigation of attractive thin coating designs, which can be performed over a range of controlled temperatures. Here, a novel in situ nanoindentation device was developed, able to perform precise displacement cycles to 1kHz at temperatures up to 500°C within a scanning electron microscope. The system is based on a piezoelectric driving tip containing four discrete piezo devices, allowing for the collection of load-displacement data for each individual cycle. Operation of the device at 500Hz was demonstrated on arc-PVD chromium nitride coated nitrided steel with a diamond flat-punch counter-body, and the effects of temperature and impact number on fatigue deformation studied using electron microscopy techniques. It was found that as the impact number increased as did the residual plastic damage from the impact force. Additionally, the deformation of the tooling was highly dependent on the temperature, which became more strongly apparent with an increased number of impacts. Such testing will be useful for evaluating the lifetime and fatigue properties of potential new thin films and coatings for high-impact operations, where understanding the influence of temperature is crucial.

Comparison of the mechanical properties of the anterior lens capsule in senile cataract, senile cataract with trypan blue application, and pseudoexfoliation syndrome

To evaluate the elastic modulus, hardness, and mechanicalproperties of the anterior lens capsule in different typesof cataract and to assess the correlation with age. Baskent University Hospital, Department of Ophthalmology, Ankara, Turkey. Prospective comparative study. Patients were divided into 3 groups. Group 1 comprised patients with senile cataract, Group 2 patients had pseudoexfoliation (PXF) syndrome, and Group 3 patients had dye-enhanced cataract surgery. The capsules were analyzed using a nanoindentation device. Young's modulus of elasticity was measured by the Oliver-Pharr method and capsule hardness by the Martens method. The study comprised 72 patients, 24 per group. The mean Young's modulus was 7.53GPa±1.07 (SD) in Group 1, 6.01±1.25GPa in Group 2, and 8.12±0.98GPa in Group3.The capsules in Group 2 were more elastic than in Group 1 and Group 3 (P<.001). The capsules in Group 3 had lower elasticity than in Group 1, although the difference was not significant (P=.94). The mean capsule stiffness was 326.41±98.40MPa in Group 1, 210.5±52.32MPa in Group 2, and 315.54±163.15MPa in Group 3. The lens capsules in Group 2 were less stiff than those in Group 1 and Group 3 (P<.001). Capsule thickness was positively correlated with increasing age in all groups. The anterior lens capsules of patients with PXF had more elasticity and less stiffness than the other groups. Intracameral trypan blue application had no effect on capsule elasticity and stiffness.

Friction Coefficient Measured on a Single $$\mathbf{WS}_\mathbf{2}$$ WS 2 Nanoparticle: An In Situ Transmission Electron Microscope Experiment

An in situ friction test was carried out on a single $$\hbox {WS}_{2}$$ nanoparticle in a transmission electron microscope (TEM) using a nanoindentation device able to measure normal and lateral forces independently. For the first time, quantitative results are reported: friction forces were recorded during the test, and thus, friction coefficient values were calculated. The exfoliation of the particle was observed during the experiment, and it was linked to the friction coefficient modification. The success of using this technique opens many possibilities of doing in situ friction tests in a TEM, especially for revealing and studying lubrication mechanisms.

Comparative Evaluation of Mechanical Properties of Dental Nanomaterials

This study examines the properties of nanobased dental restorative materials with nanoindentation method in a precise, repeatable, and comparable way. Microhybrid and nanohybrid composites, conventional glass ionomer materials, and light cured nanoionomer materials were utilised for the study. Specimen discs (r=10 mm,h=2 mm) were prepared to test the hardness, modulus of elasticity, yield strength, and fracture toughness values for each sample in a nanoindentation device with an atomic force microscopy add-on (n=25). Comparative analyses were performed by one-way ANOVA and post hoc Tukey tests. The hardness and modulus of elasticity values of nanocomposite were higher (2.58 GPa and 32.86 GPa, resp.) than those of other dental materials. Although glass ionomer exhibited a hardness that was similar to a nanoionomer (0.81 versus 0.87 GPa), glass ionomer had the lowest fracture toughness value (Kc=0.83 MPa/mm0.5). The mechanical properties of resin composites improve with additional nanoscale fillers, unlike the glass ionomer material.

Mechanical Anisotropy and Pressure Induced Structural Changes in Piroxicam Crystals Probed by In Situ Indentation and Raman Spectroscopy

The ability to correlate mechanical and chemical characterization techniques in real time is both lacking and powerful tool for gaining insights into material behavior. This is demonstrated through use of a novel nanoindentation device equipped with Raman spectroscopy to explore the deformation-induced structural changes in piroxicam crystals. Mechanical anisotropy was observed in two major faces (\( 0\bar{1}1 \)) and (011), which are correlated to changes in the interlayer interaction from in situ Raman spectra recorded during indentation. The results of this study demonstrate the considerable potential of an in situ Raman nanoindentation instrument for studying a variety of topics, including stress-induced phase transformation mechanisms, mechanochemistry, and solid state reactivity under mechanical forces that occur in molecular and pharmaceutical solids.

Mechanical Characteristics of As2S3Glasses Induced by Doping with Bismuth

This paper presents and discusses the results of the instrumented indentation test of the samples of the system Bix(As2S3)100 x, x = 1:5, 3, 5, and 7 at.%. Measurements of mechanical parameters were performed using a Fischerscope HM2000 S nanoindentation device. The experimental data obtained by measuring the microhardness parameters were used to determine some other mechanical quantities that are important for the characterization of the examined materials in terms of their potential applications. For the first three compositions, the results indicated an increase in the microhardness with the increase in the content of doping atoms, which can be interpreted as an enhancement of the strength and stiness of the structural network. The lower value of microhardness of the sample with the maximum content of Bi can BE associated with the specific structure of this composition. The pronounced indentation size eect was also detected on the indentation curve in the range of smaller loads. According to the model of elastic-plastic deformation, applied for the description of indentation size eect measured for the investigated chalcogenides, the largest value of the elastic recovery was observed for the sample Bi7(As2S3)93. The calculated values of the elasticity modulus show that the glass with x = 5 at.% Bi is characterized with the highest atomic packing density.

Two-body abrasion resistance of cementite containing different chromium concentrations

Abstract

Fundamental limitations at the determination of initial yield stress using nano-indentation with spherical tips

Abstract Nano-indentation with spherical indenters can be used to determine the local initial yield stress with an approach consisting of i) detection of the onset of plastic deformation applying a loading-partial-unloading (LPU) procedure and ii) calculation of the spatial distribution of the von Mises stress in the sample for the state of the system where plastic deformation just starts. The spatial maximum of the von Mises stress is taken as a measure of the initial yield stress. This approach, however, is subject to a fundamental restriction due to the fact that the plastic deformation starts within the volume of the sample and only limited information about this is available at the specimen surface. Since the displacement resolution of the indentation device is always limited, this leads to a fundamental overestimation of the initial yield stress. In this paper, the limitation of the approach is investigated by using finite element simulations of spherical LPU experiments for various sample parameters and sphere radii. With reference to the displacement resolution of the used nano-indentation device, the overestimation of the initial yield has been quantified and used to correct experimental results. The comparison of these corrected yield stresses to reference values clearly shows that the initially obtained dependence on the sphere radius was due to the fundamental overestimation of the yield stresses determined via spherical nano-indentation (Fig. 5).

The local strength of microscopic alumina reinforcements

We measure, using an adaptation of a method designed for ceramic ball bearings, the local strength of a brittle second phase that serves to reinforce a metal. The method uses focused ion beam milling and a nanoindentation device, and is free of artifacts commonly present in micromachined specimens. It is demonstrated on Nextel 610™ nanocrystalline alumina fibers embedded in an aluminum matrix composite. Results reveal a size effect that does not follow, across size scales, usual Weibull statistics: the fiber strength distribution differs between measurements at the microscale and macroscopic tensile testing. This implies that, in micromechanical analysis of multiphase materials, highly localized events such as the propagation of internal damage require input data that must be measured at the same, local, microscale as the event; the present work opens a path to this end.

Strengthening mechanisms of iron micropillars

We examine the size effect and strengthening mechanisms of bcc iron pillars. The single-crystal pillars were machined with focused ion beam and tested with a nanoindentation device with the compression axis along the crystallographic direction. We compare our test results with both older literature on whiskers and micro/macro specimens, and recent results from atomistic modelling. We find that the obtained results can be explained on the basis of current theories based on small-scale plasticity.

Nanoindentation Derived Mechanical Properties of the Corneoscleral Rim of the Human Eye

The corneoscleral rim of the eye represents a region with unique anatomical properties due to its location between the cornea and sclera / conjunctiva. It further has unique functional properties due to the location of adult corneal epithelial stem cells in the rim structure (limbus) itself. These stem cells are essential for the regeneration of the corneal epithelium and for preventing the conjunctival epithelium from growing onto the corneal surface, which could result in blindness. Survival and self-renewal properties of stem cells are known to depend on specific biological and biomechanical properties of its niche environment. We therefore aimed to measure the local mechanical properties of the human corneoscleral rim using a novel nanoindentation device (Bioindenter CSM Instruments, Neuchâtel, Switzerland) developed for soft tissues evaluation. Nanoindentation was performed using a spherical indenter of 0,5mm radius, a maximal load ranging between 20 μN to 30 μN and a penetration depth of several μm to 60μm. The hold period at maximum load was 180 seconds. Youngs modulus (E) was calculated using a Hertzian fit to the loading data. E of the central cornea was in the range of 19 kPa, while in the scleral region we found 17 kPa and the limbal rim region 10 kPa. Considerable creep relaxation occurred during the hold period at maximum load, which scaled with the elastic modulus of the different structures. These results reveal biomechanical properties of the corneoscleral rim with distinct mechanical properties for the three anatomical regions.

Nanoindentation Derived Mechanical Properties of the Corneascleral Rim of the Human Eye

The corneoscleral rim of the eye represents a region with unique anatomical properties due to its location between the cornea and sclera / conjunctiva. It further has unique functional properties due to the location of adult corneal epithelial stem cells in the rim structure (limbus) itself. These stem cells are essential for the regeneration of the corneal epithelium and for preventing the conjunctival epithelium from growing onto the corneal surface, which could result in blindness. Survival and self-renewal properties of stem cells are known to depend on specific biological and biomechanical properties of its niche environment. We therefore aimed to measure the local mechanical properties of the human corneoscleral rim using a novel nanoindentation device (Bioindenter CSM Instruments, Neuchâtel, Switzerland) developed for soft tissues evaluation. Nanoindentation was performed using a spherical indenter of 0,5mm radius, a maximal load ranging between 20 μN to 30 μN and a penetration depth of several μm to 60μm. The hold period at maximum load was 180 seconds. Youngs modulus (E) was calculated using a Hertzian fit to the loading data. E of the central cornea was in the range of 19 kPa, while in the scleral region we found 17 kPa and the limbal rim region 10 kPa. Considerable creep relaxation occurred during the hold period at maximum load, which scaled with the elastic modulus of the different structures. These results reveal biomechanical properties of the corneoscleral rim with distinct mechanical properties for the three anatomical regions.

Microstructure evolution and mechanical properties in VC/SiC nanomultilayers

A series of VC/SiC nanomultilayers were synthesized by magnetron sputtering techniques at a substrate temperature of 450°C. The microstructure and mechanical properties of the multilayers were studied by X-ray diffractometer, high-resolution transmission electron microscopy and nanoindentation device. The results showed that when the SiC layer thickness was below 0.7nm, the as-deposited amorphous SiC layers were crystallized and grew coherently with VC layers under the template effect of VC layers, accompanied by a remarkable increase in hardness. Further increasing SiC layer thickness, however, the epitaxial growth structure of the multilayers has been disrupted leading to the decrease of hardness.

Nano-Indentation Device for Investigating the Mechanics of Compliant Materials

Indentation testing has long been used to measure the mechanical properties of a wide range of materials from metals and ceramics to brain tissue and hydrogels. The purpose of this study was to build and validate a Nano-Tissue Indenter (NTI) capable of performing indentation testing on micro-scale structures within the liver’s extracellular matrix. Two silicone-based tissue simulant materials were selected with elastic properties similar to hydrogels used for liver cell cultures. Samples of each material formulation, EcoFlex0030 (EF30) and EcoFlex0010 (EF10), were indented with NTI and also tested in unconfined compression to provide benchmark shear moduli. The resulting force and displacement measurements from NTI with resolutions of 300 nN and 700 nm respectively were analyzed using the Pietrement-Troyon model of adhesive contact. Using this method, NTI was able to distinguish a 10 kPa difference in shear modulus between EF30 and EF10 with comparable significance as unconfined compression (p < 0.001). General agreement between the results of the two test methods is evidenced by the overlapping of the mean ± S.D. range for the NTI-indentation and benchmark unconfined compression shear moduli measured for both formulations. NTI was used successfully to perform nano-indentation tests on samples of compliant material undergoing adhesive contact, similar to the extracellular matrix of organs such as the liver.

Nanoindentation Measurements of Biomechanical Properties in Mature and Newly Formed Bone Tissue Surrounding an Implant

The characterization of the biomechanical properties of newly formed bone tissue around implants is important to understand the osseointegration process. The objective of this study is to investigate the evolution of the hardness and indentation modulus of newly formed bone tissue as a function of healing time. To do so, a nanoindentation device is employed following a multimodality approach using histological analysis. Coin-shaped implants were placed in vivo at a distance of 200 μm from the cortical bone surface, leading to an initially empty cavity of 200 μm * 4.4 mm. Three New Zealand White rabbits were sacrificed after 4, 7, and 13 weeks of healing time. The bone samples were embedded and analyzed using histological analyses, allowing to distinguish mature and newly formed bone tissue. The bone mechanical properties were then measured in mature and newly formed bone tissue. The results are within the range of hardness and apparent Young's modulus values reported in previous literature. One-way ANOVA test revealed a significant effect of healing time on the indentation modulus (p < 0.001, F = 111.24) and hardness (p < 0.02, F = 3.47) of bone tissue. A Tukey-Kramer analysis revealed that the biomechanical properties of newly formed bone tissue (4 weeks) were significantly different from those of mature bone tissue. The comparison with the results obtained in Mathieu et al. (2011, "Micro-Brillouin Scattering Measurements in Mature and Newly Formed Bone Tissue Surrounding an Implant," J. Biomech. Eng., 133, 021006). shows that bone mass density increases by approximately 13.5% between newly formed bone (7 weeks) and mature bone tissue.