Journal articles: 'Conventional nanoindentation'

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Mueller, Johannes, Karsten Durst, Dorothea Amberger, and Matthias Göken. "Local Investigations of the Mechanical Properties of Ultrafine Grained Metals by Nanoindentations." Materials Science Forum 503-504 (January 2006): 31–36. http://dx.doi.org/10.4028/www.scientific.net/msf.503-504.31.

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The mechanical properties of ultrafine-grained metals processed by equal channel angular pressing is investigated by nanoindentations in comparison with measurements on nanocrystalline nickel with a grain size between 20 and 400 nm produced by pulsed electrodeposition. Besides hardness and Young’s modulus measurements, the nanoindentation method allows also controlled experiments on the strain rate sensitivity, which are discussed in detail in this paper. Nanoindentation measurements can be performed at indentation strain rates between 10-3 s-1 and 0.1 s-1. Nanocrystalline and ultrafine-grained fcc metals as Al and Ni show a significant strain rate sensitivity at room temperature in comparison with conventional grain sized materials. In ultrafine-grained bcc Fe the strain rate sensitivity does not change significantly after severe plastic deformation. Inelastic effects are found during repeated unloading-loading experiments in nanoindentations.

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Randall, Nicholas X., Matthieu Vandamme, and Franz-Josef Ulm. "Nanoindentation analysis as a two-dimensional tool for mapping the mechanical properties of complex surfaces." Journal of Materials Research 24, no. 3 (March 2009): 679–90. http://dx.doi.org/10.1557/jmr.2009.0149.

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Instrumented indentation (referred to as nanoindentation at low loads and low depths) has now become established for the single point characterization of hardness and elastic modulus of both bulk and coated materials. This makes it a good technique for measuring mechanical properties of homogeneous materials. However, many composite materials are composed of material phases that cannot be examined in bulk form ex situ (e.g., carbides in a ferrous matrix, calcium silicate hydrates in cements, etc.). The requirement for in situ analysis and characterization of chemically complex phases obviates conventional mechanical testing of large specimens representative of these material components. This paper will focus on new developments in the way that nanoindentation can be used as a two-dimensional mapping tool for examining the properties of constituent phases independently of each other. This approach relies on large arrays of nanoindentations (known as grid indentation) and statistical analysis of the resulting data.

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Costelle, Leila, Liina Lind, Pasi Jalkanen, Minna T. Räisänen, Roman Nowak, and Jyrki Räisänen. "Conventional Nanoindentation in Self-Assembled Monolayers Deposited on Gold and Silver Substrates." Journal of Nanomaterials 2012 (2012): 1–5. http://dx.doi.org/10.1155/2012/585123.

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Self-assembled monolayers (SAMs) are promising materials for micromechanical applications. However, characterization of mechanical properties of monolayers is challenging for standard nanoindentation, and new efficient analysis techniques are needed. Hereby, a conventional nanoindentation method has been combined in a unique way with efficient data analysis based on consumed energy calculation and load-displacement data. The procedure has been applied on SAMs of 4,4′-biphenyldithiol (BPDT) on Au, 1-tetradecanethiol (TDT), and 1-hexadecanethiol (HDT) on Au and Ag substrates being the first study where SAMs of the same thiols on different substrates are analyzed by nanoindentation providing a new insight into the substrate effects. Unlike TDT and HDT SAMs, which are found to strongly enhance the homogeneity and stiffness of the underlying substrate, the BPDT covered Au substrate appears softer in mechanical response. In the case of TDT and HDT SAMs on Ag the structures are softer showing also faster relaxation than the corresponding structures on Au substrate. The proposed procedure enables a fast and efficient way of assessing the complex behaviour of SAM modified substrates. As a consequence, the results are relevant to practical issues dependent on layer activity and toughness.

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KUMAR, AMIT, and KAIYANG ZENG. "ALTERNATIVE METHODS TO EXTRACT THE HARDNESS AND ELASTIC MODULUS OF THIN FILMS FROM NANOINDENTATION LOAD-DISPLACEMENT DATA." International Journal of Applied Mechanics 02, no. 01 (March 2010): 41–68. http://dx.doi.org/10.1142/s1758825110000445.

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This paper presents alternative analysis methodologies to extract the elastic modulus and hardness of the ultra-thin films from nanoindentation load-displacement data, especially when the film thickness is only few hundred nanometers or less. At such film thickness, the conventional analysis methods for nanoindentation usually do not give accurate film properties due to the substrate effect. The new methods are capable to show how to determine the film-only properties and how the substrates affect the nanoindentation measurement, especially for ultra thin films. These methods give accurate results for nanoindentation of various metallic, ceramic and polymeric films. It also reveals the differences between the use of high-resolution nanoindentation set-up and normal nanoindentation set-up on the same films. The relationships between the mechanical properties and film thickness are also discussed.

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Long, Xu, Xiaodi Zhang, Wenbin Tang, Shaobin Wang, Yihui Feng, and Chao Chang. "Calibration of a Constitutive Model from Tension and Nanoindentation for Lead-Free Solder." Micromachines 9, no. 11 (November 20, 2018): 608. http://dx.doi.org/10.3390/mi9110608.

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It is challenging to evaluate constitutive behaviour by using conventional uniaxial tests for materials with limited sizes, considering the miniaturization trend of integrated circuits in electronic devices. An instrumented nanoindentation approach is appealing to obtain local properties as the function of penetration depth. In this paper, both conventional tensile and nanoindentation experiments are performed on samples of a lead-free Sn–3.0Ag–0.5Cu (SAC305) solder alloy. In order to align the material behaviour, thermal treatments were performed at different temperatures and durations for all specimens, for both tensile experiments and nanoindentation experiments. Based on the self-similarity of the used Berkovich indenter, a power-law model is adopted to describe the stress–strain relationship by means of analytical dimensionless analysis on the applied load-penetration depth responses from nanoindentation experiments. In light of the significant difference of applied strain rates in the tensile and nanoindentation experiments, two “rate factors” are proposed by multiplying the representative stress and stress exponent in the adopted analytical model, and the corresponding values are determined for the best predictions of nanoindentation responses in the form of an applied load–indentation depth relationship. Eventually, good agreement is achieved when comparing the stress–strain responses measured from tensile experiments and estimated from the applied load–indentation depth responses of nanoindentation experiments. The rate factors ψ σ and ψ n are calibrated to be about 0.52 and 0.10, respectively, which facilitate the conversion of constitutive behaviour from nanoindentation experiments for material sample with a limited size.

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Ahn, Byung, R. Mitra, A. M. Hodge, Enrique J. Lavernia, and S. R. Nutt. "Strain Rate Sensitivity Studies of Cryomilled Al Alloy Performed by Nanoindentation." Materials Science Forum 584-586 (June 2008): 221–26. http://dx.doi.org/10.4028/www.scientific.net/msf.584-586.221.

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Al 5083 alloy powder was mechanically milled in liquid nitrogen to achieve a nanocrystalline (NC) structure having an average grain size of 50 nm with high thermal stability, and then consolidated by quasi-isostatic (QI) forging. The consolidation resulted in ultrafine grains (UFG) of about 250 nm, and the bulk material exhibited enhanced strength compared to conventionally processed Al 5083. The hardness of as-cryomilled powder and the UFG material was measured by nanoindentation using loading rates in the range of 50−50,000 /N/s, and results were compared with the conventional grain size alloy. Negative strain rate sensitivity was observed in the cryomilled NC powder and the forged UFG plate, while the conventional alloy was relatively strain rate insensitive.

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Tsui, T. Y., W. C. Oliver, and G. M. Pharr. "Influences of stress on the measurement of mechanical properties using nanoindentation: Part I. Experimental studies in an aluminum alloy." Journal of Materials Research 11, no. 3 (March 1996): 752–59. http://dx.doi.org/10.1557/jmr.1996.0091.

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The influence of applied stress on the measurement of hardness and elastic modulus using nanoindentation methods has been experimentally investigated using special specimens of aluminum alloy 8009 to which controlled stresses could be applied by bending. When analyzed according to standard methods, the nanoindentation data reveal changes in hardness with stress similar to those observed in conventional hardness tests. However, the same analysis shows that the elastic modulus changes with stress by as much as 10%, thus suggesting that the analysis procedure is somehow deficient. Comparison of the real indentation contact areas measured optically to those determined from the nanoindentation data shows that the apparent stress dependence of the modulus results from an underestimation of the contact area by the nanoindentation analysis procedures.

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Sousa, Bryer C., Kristin L. Sundberg, Matthew A. Gleason, and Danielle L. Cote. "Understanding the Antipathogenic Performance of Nanostructured and Conventional Copper Cold Spray Material Consolidations and Coated Surfaces." Crystals 10, no. 6 (June 12, 2020): 504. http://dx.doi.org/10.3390/cryst10060504.

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The role of high strain rate and severe plastic deformation, microstructure, electrochemical behavior, surface chemistry and surface roughness were characterized for two copper cold spray material consolidations, which were produced from conventionally gas-atomized copper powder as well as spray-dried copper feedstock, during the course of this work. The motivation underpinning this work centers upon the development of a more robust understanding of the microstructural features and properties of the conventional copper and nanostructured copper coatings as they relate to antipathogenic contact killing and inactivation applications. Prior work has demonstrated greater antipathogenic efficacy with respect to the nanostructured coating versus the conventional coating. Thus, microstructural analysis was performed in order to establish differences between the two coatings that their respective pathogen kill rates could be attributed to. Results from advanced laser-induced projectile impact testing, X-ray diffraction, scanning electron microscopy, electron backscatter diffraction, scanning transmission microscopy, nanoindentation, energy-dispersive X-ray spectroscopy, nanoindentation, confocal microscopy, atomic force microscopy, linear polarization, X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy and copper ion release assaying were performed during the course of this research.

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Minor, A. M., E. T. Lilleodden, E. A. Stach, and J. W. Morris. "Direct observations of incipient plasticity during nanoindentation of Al." Journal of Materials Research 19, no. 1 (January 2004): 176–82. http://dx.doi.org/10.1557/jmr.2004.19.1.176.

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The mechanical testing technique for in situ nanoindentation in a transmission electron microscope is described and is shown to provide real-time observations of the mechanisms of plastic deformation that occur during nanoindentation. Here, the importance of this technique was demonstrated on an aluminum thin film deposited on a single-crystalline silicon substrate. Significant results include direct observation of dislocation nucleation, characterization of the dislocation distribution created by indentation, and the observation of indentation-induced grain boundary motion. The observations achieved by this technique provide unique insight into mechanical behavior studied with conventional instrumented nanoindentation techniques and also provide microstructural-level understanding of the mechanics of ultrasmall volumes.

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Fischer-Cripps, A. C. "Multiple-frequency dynamic nanoindentation testing." Journal of Materials Research 19, no. 10 (October 1, 2004): 2981–88. http://dx.doi.org/10.1557/jmr.2004.0368.

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A new method of dynamic nanoindentation testing is introduced in this paper. Conventional dynamic nanoindentation testing involves the superposition of a single frequency sinusoidal force or displacement onto the quasi-static load–displacement curve. However, the viscoelastic response of many materials depends upon the frequency of the deformation of the material. This paper describes a method whereby the storage and loss modulus of viscoelastic solids can be determined using a multi-frequency dynamic oscillatory motion mode of deformation. In this method, the applied load is modulated by a pseudo-random force signal comprising multiple frequencies. A Fourier analysis is then used to deconvolute the signal into frequency-dependent values of storage and loss modulus for the specimen material as a function of frequency. The instrument response is cancelled by the use of a reference transfer function using an equalization process. Established modeling equations can then be used to extract the modulus of elasticity and the viscosity of the specimen material.

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Bushby, A. J., and D. J. Dunstan. "Plasticity size effects in nanoindentation." Journal of Materials Research 19, no. 1 (January 2004): 137–42. http://dx.doi.org/10.1557/jmr.2004.19.1.137.

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In conventional continuum mechanics, the yield behavior of a material is size independent. However, in nanoindentation, plasticity size effects have been observed for many years, where a higher hardness is measured for smaller indentation size. In this paper we show that there was a size effect in the initiation of plasticity, by using spherical indenters with different radii, and that the length scale at which the size effect became significant depended on the mechanism of plastic deformation. For yield by densification (fused silica), there was no size effect in the nanoindentation regime. For phase transition (silicon), the length scale was of the order tens of nanometers. For materials that deform by dislocations (InGaAs/InP), the length scale was of the order a micrometer, to provide the space required for a dislocation to operate. We show that these size effects are the result of yield initiating over a finite volume and predict the length scale over which each mechanism should become significant.

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Cinar, Eyup, Ferat Sahin, and Dalia Yablon. "Development of a novel nanoindentation technique by utilizing a dual-probe AFM system." Beilstein Journal of Nanotechnology 6 (October 12, 2015): 2015–27. http://dx.doi.org/10.3762/bjnano.6.205.

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A novel instrumentation approach to nanoindentation is described that exhibits improved resolution and depth sensing. The approach is based on a multi-probe scanning probe microscopy (SPM) tool that utilizes tuning-fork based probes for both indentation and depth sensing. Unlike nanoindentation experiments performed with conventional AFM systems using beam-bounce technology, this technique incorporates a second probe system with an ultra-high resolution for depth sensing. The additional second probe measures only the vertical movement of the straight indenter attached to a tuning-fork probe with a high spring constant and it can also be used for AFM scanning to obtain an accurate profiling. Nanoindentation results are demonstrated on silicon, fused silica, and Corning Eagle Glass. The results show that this new approach is viable in terms of accurately characterizing mechanical properties of materials through nanoindentation with high accuracy, and it opens doors to many other exciting applications in the field of nanomechanical characterization.

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Hayes, S. A., A. A. Goruppa, and F. R. Jones. "Dynamic nanoindentation as a tool for the examination of polymeric materials." Journal of Materials Research 19, no. 11 (November 1, 2004): 3298–306. http://dx.doi.org/10.1557/jmr.2004.0437.

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The determination of the mechanical properties of polymers is more complex than that of many other structural materials, because they display time-dependence in their response to load. Generally, dynamic analysis techniques, such as dynamic mechanical thermal analysis (DMTA), are used to characterize the viscoelastic properties of bulk polymers. However, polymers are increasingly being used as thin films, the properties of which are not readily determined using conventional techniques. Nanoindentation offers the possibility of determining the properties of thin films but has generally only been used to measure static properties. Dynamic nanoindentation equipment has recently become available, but its accuracy with soft polymers is unproven. This paper presents results of a comparison between dynamic nanoindentation, DMTA, and differential scanning calorimetry (DSC) for the determination of the thermal response of four different polymers. A favorable comparison is shown, indicating that dynamic nanoindentation is capable of measuring the time-dependent properties of small samples of polymers.

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Lee, Yun Hee, Dongil Kwon, and Jae Il Jang. "Evaluation of Thin-Film Residual Stress Using Nano-Indentation Combined with an Atomic Force Microscope." International Journal of Modern Physics B 17, no. 08n09 (April 10, 2003): 1141–46. http://dx.doi.org/10.1142/s0217979203018648.

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Thin-film stress changes the shape of nanoindentation loading curve. The change in the indentation load is treated as the effect of the residual stress on the indenting deformation. A residual-stress-induced normal load is defined as a multiple of contact area and plastic deformation-sensitive deviator stress component extracted from the equi-biaxial thin-film stress. A final equation for the residual stress is derived from the residual-stress-induced normal load by considering an integration along a depth-controlled stress-relaxation route. This proposed model is applied to the analyses of the nanoindentation curves for diamond-like carbon thin films. The residual stresses from the nanoindentation analyses were consistent with the values obtained by the conventional curvature method.

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Schuh, Christopher A., Corinne E. Packard, and Alan C. Lund. "Nanoindentation and contact-mode imaging at high temperatures." Journal of Materials Research 21, no. 3 (March 1, 2006): 725–36. http://dx.doi.org/10.1557/jmr.2006.0080.

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Technical issues surrounding the use of nanoindentation at elevated temperatures are discussed, including heat management, thermal equilibration, instrumental drift, and temperature-induced changes to the shape and properties of the indenter tip. After characterizing and managing these complexities, quantitative mechanical property measurements are performed on a specimen of standard fused silica at temperatures up to 405 °C. The extracted values of hardness and Young's modulus are validated against independent experimental data from conventional mechanical tests, and accuracy comparable to that obtained in standard room-temperature nanoindentation is demonstrated. In situ contact-mode images of the surface at temperature are also presented.

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Morse, K., T. P. Weihs, A. V. Hamza, M. Balooch, Z. Jiang, and D. B. Bogy. "Nanomechanical Properties of SiC Films Grown From C60 Precursors Using Atomic Force Microscopy." Journal of Tribology 119, no. 1 (January 1, 1997): 26–30. http://dx.doi.org/10.1115/1.2832475.

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The mechanical properties of SiC films grown via C60 precursors were determined using atomic force microscopy (AFM). Conventional silicon nitride and diamond-tipped steel AFM cantilevers were employed to determine the film hardness, friction coefficient, and elastic modulus. The hardness is found to be 26 GPa by nanoindentation of the film with a Berkovich diamond tip. The friction coefficient for the silicon nitride tip on the SiC film is about one half to one third that for silicon nitride sliding on a silicon substrate. By combining nanoindentation and AFM measurements an elastic modulus of ~300 GPa is estimated for these SiC films.

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Král, Petr, Jiří Dvořák, Marie Kvapilová, Jaroslav Lukeš, and Vaclav Sklenička. "Constant Load Testing of Materials Using Nanoindentation Technique." Key Engineering Materials 606 (March 2014): 69–72. http://dx.doi.org/10.4028/www.scientific.net/kem.606.69.

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Experiments were conducted to evaluate creep behavior of conventional and ultrafine-grained metallic materials using nanoindentation technique. The polished surface of samples was loaded up to 5 mN. The load was held constant to examine the creep behavior. Nanoindentation tests were performed at room temperature. Strain rate was evaluated from load and displacement data. The stress exponents of strain rates n were determined from loading stress dependences of creep rate. The values of stress exponents of the indentation strain rate indicate that creep behavior of investigated materials is influenced in particular by slip of intragranular dislocations. By contrast, deformation mechanisms like grain boundary sliding and diffusion processes seem to be improbable.

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Liao, Jin Zhi, Jian Jun Pang, and Ming Jen Tan. "Nanoindentation of Multi-Wall CNT Reinforced Al Composites." Key Engineering Materials 447-448 (September 2010): 549–53. http://dx.doi.org/10.4028/www.scientific.net/kem.447-448.549.

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This work used nanoindentation to characterize the local mechanical properties of the multi-wall carbon nanotube (MWCNT) reinforced aluminum (Al) composites. The Al-MWCNT (0.5, 1.0 and 2.0 wt.%) specimens were fabricated by spark plasma sintering (SPS) followed by hot extrusion. Different local regions of the as-extruded and tensile-fractured specimen over the longitudinal and transverse section were studied by nanoindentation. The nanoindentation results were compared with the conventional macro- and mircoscopic mechanical tests, and were found in good agreement. The values of hardness (H) and elastic modulus (E) obtained reached maximum at the 0.5 wt.% MWCNT adding Al samples. E was highest in the necking region then decreased with increasing distance from the localized deformed region; while H varied in different regions. In the same region, H and V were higher in the longitudinal than those in the transverse direction, due to the texture hardening and alignment of CNT.

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Trivedi, R., and V. Cech. "Mechanical properties of plasma polymer film evaluated by conventional and alternative nanoindentation techniques." Surface and Coatings Technology 205 (December 2010): S286—S289. http://dx.doi.org/10.1016/j.surfcoat.2010.08.002.

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Qu, S., Y. Huang, W. D. Nix, H. Jiang, F. Zhang, and K. C. Hwang. "Indenter tip radius effect on the Nix–Gao relation in micro- and nanoindentation hardness experiments." Journal of Materials Research 19, no. 11 (November 1, 2004): 3423–34. http://dx.doi.org/10.1557/jmr.2004.0441.

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Nix and Gao established an important relation between microindentation hardnessand indentation depth. Such a relation has been verified by many microindentation experiments (indentation depths in the micrometer range), but it does not always hold in nanoindentation experiments (indentation depths approaching the nanometer range). We have developed a unified computational model for both micro- and nanoindentation in an effort to understand the breakdown of the Nix–Gao relation at indentation depths approaching the nanometer scale. The unified computational model for indentation accounts for various indenter shapes, including a sharp, conical indenter, a spherical indenter, and a conical indenter with a spherical tip. It is based on the conventional theory of mechanism-based strain gradient plasticity established from the Taylor dislocation model to account for the effect of geometrically necessary dislocations. The unified computational model for indentation indeed shows that the Nix–Gao relation holds in microindentation with a sharp indenter, but it does not hold in nanoindentation due to the indenter tip radius effect.

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Thom, Christopher, and David Goldsby. "Nanoindentation Studies of Plasticity and Dislocation Creep in Halite." Geosciences 9, no. 2 (February 6, 2019): 79. http://dx.doi.org/10.3390/geosciences9020079.

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Previous deformation experiments on halite have collectively explored different creep mechanisms, including dislocation creep and pressure solution. Here, we use an alternative to conventional uniaxial or triaxial deformation experiments—nanoindentation tests—to measure the hardness and creep behavior of single crystals of halite at room temperature. The hardness tests reveal two key phenomena: (1) strain rate-dependent hardness characterized by a value of the stress exponent of ~25, and (2) an indentation size effect, whereby hardness decreases with increasing size of the indents. Indentation creep tests were performed for hold times ranging from 3600 to 106 s, with a constant load of 100 mN. For hold times longer than 3 × 104 s, a transition from plasticity to power-law creep is observed as the stress decreases during the hold, with the latter characterized by a value of the stress exponent of 4.87 ± 0.91. An existing theoretical analysis allows us to directly compare our indentation creep data with dislocation creep flow laws for halite derived from triaxial experiments on polycrystalline samples. Using this analysis, we show an excellent agreement between our data and the flow laws, with the strain rate at a given stress varying by less than 5% for a commonly used flow law. Our results underscore the utility of using nanoindentation as an alternative to more conventional methods to measure the creep behavior of geological materials.

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Wright, Wendelin J., and W. D. Nix. "Storage and loss stiffnesses and moduli as determined by dynamic nanoindentation." Journal of Materials Research 24, no. 3 (March 2009): 863–71. http://dx.doi.org/10.1557/jmr.2009.0112.

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The storage and loss stiffnesses for the composite response of the sample, indenter, and load frame during dynamic nanoindentation are derived. In the first part of the analysis, no physical model is assigned to the composite system. It is shown that this case is equivalent to the conventional nanoindentation analysis. In the second part of the analysis, the sample is modeled as a standard linear solid in series with the indenter and load frame. The results for the storage and loss stiffnesses as computed by the two methods differ by at most ∼3% for the elastomeric system under consideration. Results for the storage and loss moduli are also similar. The relative merits and weaknesses of each analysis are discussed.

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Backes, B., Y. Y. Huang, M. Göken, and K. Durst. "The correlation between the internal material length scale and the microstructure in nanoindentation experiments and simulations using the conventional mechanism-based strain gradient plasticity theory." Journal of Materials Research 24, no. 3 (March 2009): 1197–207. http://dx.doi.org/10.1557/jmr.2009.0123.

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In the present work a new equation to determine the internal material length scale for strain gradient plasticity theories from two independent experiments (uniaxial and nanoindentation tests) is introduced. The applicability of the presented equation is verified for conventional grained as well as for ultrafine-grained copper and brass with different amounts of prestraining. A significant decrease of the experimentally determined internal material length scale is found for increasing dislocation densities due to prestraining. Conventional mechanism strain gradient plasticity theory is used for simulating the indentation response, using experimentally determined material input data as the yield stress, the work-hardening behavior and the internal material length scale. The work-hardening behavior and the yield stress were taken from the uniaxial experiments, whereas the internal material length scale was calculated using the yield stress from the uniaxial experiment, the macroscopic hardness H0 and the length scale parameter h* following from the nanoindentation experiment. A good agreement between the measured and calculated load–displacement curve and the hardness is found independent of the material and the microstructure.

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Li, Xiaobao, and Changwen Mi. "Nanoindentation hardness of a Steigmann–Ogden surface bounding an elastic half-space." Mathematics and Mechanics of Solids 24, no. 9 (October 5, 2018): 2754–66. http://dx.doi.org/10.1177/1081286518799795.

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Previous studies demonstrate that, for nanostructures under transverse bending, the effective Young modulus is appreciably greater (in magnitude) than that of the same elements under axial loads. Therefore, in addition to the conventional residual surface tension and membrane stiffness, the curvature dependence of surface energy is desired for inhomogeneously strained nanostructures. In this paper, we aim to reevaluate the size-dependent nanoindentation hardness of an elastic half-space subjected to nanosized frictionless traction, through the use of both the curvature-independent Gurtin–Murdoch and the curvature-dependent Steigmann–Ogden models of surface elasticity. The nanoindentation problem is solved by the integration of Boussinesq’s method of displacement potentials and Hankel integral transforms. As examples, the effects of residual surface tension, membrane stiffness, and bending rigidity of the half-space boundary are parametrically analyzed in detail for a uniform circular pressure and a concentrated normal force. The observations in semianalytical calculations suggest a significant difference in the nanoindentation hardnesses predicted from the two popular models of surface mechanics. In most cases, the inclusion of bending rigidity results in smaller displacements and stresses, and therefore higher indentation hardness. Based on physically interpretable numerical values of surface material properties, we show that a curvature-dependent model of surface elasticity is required in order to characterize the size-dependent feature of nanoindentation problems correctly.

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Gupta, Shikha, Fernando Carrillo, Medhi Balooch, Lisa Pruitt, and Christian Puttlitz. "Simulated Soft Tissue Nanoindentation: A Finite Element Study." Journal of Materials Research 20, no. 8 (August 1, 2005): 1979–94. http://dx.doi.org/10.1557/jmr.2005.0247.

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To address the growing interest in nanoindentation for biomaterials, the following finite element study investigated the influence of indentation testing protocol and substrate geometry on quasi-static and dynamic load-displacement behavior of linear viscoelastic materials. For a standard linear solid, the conventional quasi-static indentation modulus, EQS, fell between the instantaneous and equilibrium modulus of the model. EQS approached the equilibrium modulus only for indentation unloading times 1000 times greater than the characteristic relaxation time of the model. It was nearly insensitive to other changes in the indentation testing protocol, such as tip radius and penetration depth, exhibiting variations of only 5–10%. Dynamic nanoindentation provided a quantitatively accurate assessment of the complex dynamic modulus (within ±12%) for a range material of parameters at physiologically relevant testing parameters. Both quasi-static and dynamic moduli calculated from the irregular surfaces varied with the size and shape of the irregularities but were still within 10% of the smooth surface values for penetration depths larger than the dimensions of the surface irregularities.

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Tang, Chak Yin, P. S. Uskoković, Chi Pong Tsui, K. C. Chan, S. C. L. Lo, and Xiao Lin Xie. "Nanotribological Properties of UHMWPE/Quartz Composites." Materials Science Forum 494 (September 2005): 469–74. http://dx.doi.org/10.4028/www.scientific.net/msf.494.469.

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Wear of ultra-high molecular weight polyethylene (UHMWPE) and its composites is one of the main obstacles that limit the longevity of total joint replacements. Compression molded UHMWPE/quartz composites with organosiloxane as a cross-linking agent for UHMWPE matrix, were tested in nanoindentation and nanowear. The nanomechanical properties of the composite were examined in the light of nanoindentation experiments performed with a diamond tip of nominal radius of curvature of about 150 nm under conditions of various contact loads. Results from nanowear tests show that, in addition to the nanohardness and elastic modulus, the crosslinking procedure has the most pronounced effect on the tribological properties and at 0.5 phr organosiloxane, composites reache their maximum nanowear resistance. These findings are in agreement with the results of conventional mechanical and wear tests performed on these materials.

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Zhang, Yong, Ning Hou, Liang-Chi Zhang, and Qi Wang. "Elastic-plastic-brittle transitions of potassium dihydrogen phosphate crystals: characterization by nanoindentation." Advances in Manufacturing 8, no. 4 (September 2, 2020): 447–56. http://dx.doi.org/10.1007/s40436-020-00320-3.

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AbstractPotassium dihydrogen phosphate (KDP) crystals are widely used in laser ignition facilities as optical switching and frequency conversion components. These crystals are soft, brittle, and sensitive to external conditions (e.g., humidity, temperature, and applied stress). Hence, conventional characterization methods, such as transmission electron microscopy, cannot be used to study the mechanisms of material deformation. Nevertheless, understanding the mechanism of plastic-brittle transition in KDP crystals is important to prevent the fracture damage during the machining process. This study explores the plastic deformation and brittle fracture mechanisms of KDP crystals through nanoindentation experiments and theoretical calculations. The results show that dislocation nucleation and propagation are the main mechanisms of plastic deformation in KDP crystals, and dislocation pileup leads to brittle fracture during nanoindentation. Nanoindentation experiments using various indenters indicate that the external stress fields influence the plastic deformation of KDP crystals, and plastic deformation and brittle fracture are related to the material’s anisotropy. However, the effect of loading rate on the KDP crystal deformation is practically negligible. The results of this research provide important information on reducing machining-induced damage and further improving the optical performance of KDP crystal components.

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Carvalho, N. J. M., and J. Th M. De Hosson. "Characterization of mechanical properties of tungsten carbide/carbon multilayers: Cross-sectional electron microscopy and nanoindentation observations." Journal of Materials Research 16, no. 8 (August 2001): 2213–22. http://dx.doi.org/10.1557/jmr.2001.0304.

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Multilayers of tungsten carbide/carbon (WC/C) deposited by physical vapor deposition onto steel substrates were subjected to depth-sensing indentation testing. The investigation aimed at probing the influence of dissimilarities between the microstructure of the multilayers and substrate on the system mechanical properties. The resultant load-displacement data were analyzed both by conventional load-displacement (P-δ) and load-displacement squared (P-δ2) plots. Furthermore, it was demonstrated that the occurrence of annular through-thickness cracks around the indentation sites can be identified from the load-displacement curve. Also, analysis of the lower part of the unloading curve permitted us to identify whether the coating had popped up by localized fracture. The cracking mechanism was characterized using a new technique for cross-sectional electron microscopy of the nanoindentations. The information retrieved with this technique eliminates the problems, inherent in assessing at this small contact scales, whether the fracture is by coating decohesion or by interfacial failure. In our case, it was demonstrated that the failure mechanism was decohesion of the carbon lamellae within the multilayers. The mechanical properties (hardness and effective Young's modulus) were also assessed by nanoindentation. The hysteresis loops were analyzed and discussed in terms of the method developed by Oliver and Pharr [J. Mater. Res. 7, 1564 (1992)].

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Mayo, M. J., R. W. Siegel, A. Narayanasamy, and W. D. Nix. "Mechanical properties of nanophase TiO2 as determined by nanoindentation." Journal of Materials Research 5, no. 5 (May 1990): 1073–82. http://dx.doi.org/10.1557/jmr.1990.1073.

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Nanoindenter techniques have been used to determine the hardness. Young's modulus, and strain rate sensitivity of nanophase TiO2, which is currently available only in very small quantities and which cannot be tested by most conventional techniques. Hardness and Young's modulus both increase linearly with sintering temperature over the range 25–900°C but come to within only 50–70% of the single crystal values. Strain rate sensitivity, on the other hand, is measurably greater for this material than for single crystal rutile, and the value of strain rate sensitivity increases as the grain size and the sintering temperature are decreased. In its as-compacted form, the strain rate sensitivity of nanophase TiO2 is approximately a quarter that of lead at room temperature, indicating a potential for significant ductility in these ceramic materials. Finally, a significant scatter in hardness values has been detected within individual nanophase samples. This is interpreted as arising from microstructural inhomogeneity in these materials.

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Zhang, Xuan, Yan Li Zhong, Xiao Wen Zhang, Lei Li, and Yue Yan. "Assessment of Aging Properties of Anti-Scratch Coatings by Nanoindentation." Applied Mechanics and Materials 456 (October 2013): 378–81. http://dx.doi.org/10.4028/www.scientific.net/amm.456.378.

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The assessment of aging properties of organic coatings on plastics is critical to the using safety and service life evaluation. This paper was dedicated to evaluate the aging properties, including humidity-heat and temperature shock tests, of various anti-scratch silicon coatings deposited on polycarbonate (PC) by adhesion and nanoindentation measurements. Adhesion behaviors through conventional cross-cut and tap peel tests reveal that there are no obvious changes of these coatings after aging experiments, all ranked as 5B. However, the changes of nanomechanical properties (elastic modulus and hardness) of coatings on PC after aging tests are obvious different for these coatings. Base on these results, it is proved that nanoindetation technique could be an available method to assess aging behaviors of thin coatings.

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Desmarest, S. Godard, C. Johnston, and P. S. Grant. "Determination of the Creep Properties of Pb-free Solders for Harsh Environments Using Meso-scale Testing." Additional Conferences (Device Packaging, HiTEC, HiTEN, and CICMT) 2012, HITEC (January 1, 2012): 000117–27. http://dx.doi.org/10.4071/hitec-2012-tp23.

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Solder joints in electronic packages are prone to failure due to the evolution of thermal expansion mismatch strains during thermal cycling. The comparatively wide operating temperature range and long lifetimes of aerospace electronics require high reliability solder joints. Since 2006, high reliability industries (aerospace and military amongst others) that are exempt from lead-free RoHS regulation on account of concerns over the reliability of Pb-free solders have found it increasingly difficult and expensive to continue using traditional Sn-Pb-based solders. Hence there is a pressing need to find a suitable alternative that can match the manufacturing and reliability performance of Sn-Pb. There remains a dearth of data for the constitutive behaviour of Pb-free solders under harsh environment scenarios. Unfortunately, conventional test approaches, particularly in the case of creep behaviour which is critical to solder lifetimes, are expensive and time-consuming. High temperature nanoindentation has been recently developed as a quick method for the determination of creep properties of solder alloys. This paper compares and contrasts nanoindentation creep results for bulk Pb-Sn and lead-free solders. However, there are limits to nanoindentation creep, in particular the load-dependence of the technique. A new meso-scale test approach that lies between nanoindentation and bulk creep testing has been developed. Real ball grid arrays using Pb-free solders have been creep tested in the temperature and stress ranges of operating solder joints. High temperature creep constitutive data has been obtained. The technique offers promising time and materials savings in obtaining important mechanical property data for subsequent use in life-prediction models.

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Hloch, Sergej, Peter Monka, Pavol Hvizdos, Dagmar Jakubeczyová, Drazan Kozak, Katarina Colic, Ján Kľoc, and Dagmar Magurová. "Thermal manifestations and nanoindentation of bone cements for orthopaedic surgery." Thermal Science 18, suppl.1 (2014): 251–58. http://dx.doi.org/10.2298/tsci130901186h.

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Improving of bone cements properties is possible by research of variables influencing exothermal behaviour and mechanical properties. Paper deals with exothermal behaviour experimental evaluation of bone cements used for medical purposes. Specimens were prepared by a conventional manual mixing technique. The work addresses primary risk factor associated with application of bone cement to femoral canal. Different size samples of bone cement has been created with diameter d = 2; 5;12,5 mm fixed in dentacryl. As an experimental material, Palacos R+G high viscosity, radiopaque bone cement containing Gentamicin and Radiopaque bone cement Antibiotic Simplex with Tobramycin, was used. Thermal effect during exothermic polymerisation was measured with period 1 minute. Evaluated factors were mass and thickness of bone cement. Significant influence of bone cement mass on temperature has been found.

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Phillips, J. R., K. F. Jarausch, T. J. Stark, J. E. Houston, D. P. Griffis, and P. E. Russell. "Diamond Indenter Shaping Using Focused Ion Beam." Microscopy and Microanalysis 4, S2 (July 1998): 320–21. http://dx.doi.org/10.1017/s1431927600021723.

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Nanoindentation is becoming an increasingly important tool for the characterization of the mechanical properties of materials on the nanometer scale. The mechanical response of a material is measured by recording the force acting between an indenter and the material while displacing the indenter into the material. The shape of the recorded load displacement curves is not only dependent on the mechanical properties of the material, but also strongly dependent on indenter geometry. To minimize difficulties in the extraction of quantitative material mechanical property information from the force curve, indenter geometry must be controlled and characterized on the same scale as the indentation, i.e. on the nanometer scale. Diamond, the hardest naturally occurring material, is an obvious choice as the indenter material. Conventional lapping techniques4 do not provide sufficient control to produce indenter geometries of the shapes and to the precision required for optimal nanoindentation measurements.

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Henžel, M., Peter Zimovčák, Ján Dusza, András Juhász, and Janos Lendvai. "Indentation Testing of MoSi₂." Key Engineering Materials 290 (July 2005): 288–91. http://dx.doi.org/10.4028/www.scientific.net/kem.290.288.

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Indentation methods have been used for the study of the hardness and deformation characteristics MoSi2. Micro-nanoindentation tests at loads from 10 mN to 2000 mN were carried out using the depth-sensing method. Measurements of the microhardness using conventional Vickers method was carried out at loads of 500 mN, 1000 mN and 2000 mN. The Universal (Martens), Plastic and conventional Vickers hardness values were calculated at different indentation loads. Evident indentation load - size effect was found in both materials. According to the results, the pre-strain reduces the micro-nano hardness values, probably due to the activation of slip systems during the high-temperature deformation.

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Nikolov, N., T. Avdjieva, and I. Altaparmakov. "Length-Scale Effects and Material Models at Numerical Simulations of Nanoindentation of A Metallic Alloy." Journal of Theoretical and Applied Mechanics 44, no. 2 (June 1, 2014): 25–40. http://dx.doi.org/10.2478/jtam-2014-0008.

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Abstract Some specially designed metallic alloys crystallize during process of rapid quenching which aims their amorphization. Nevertheless, change in their mechanical properties could be seen compared to these obtained during conventional technological regimes of cooling. That attracts the attention in this elaboration. Full 3-D numerical simulations of nanoindentation process of two material models are performed. The models reflect equivalent elastic and different plastic material properties. The plastic behaviour of the first one is subjected to yield criterion of Dracker-Prager and this of the second one to yield criterion of Mises. The reported numerical results depending on the nanoindentation scale length of 1000 nanometers, suggest different adequacy of the two yield criteria to the data obtained experimentally with a Zr-Al-Cu-Ni-Mo alloy. It could be speculated that the different effects developed depending on the indenter travel of 1000 nanometers and taken into account in the two yield criteria stand behind this fact and determinate three structural levels of plastic deformation.

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Peskersoy, Cem, and Osman Culha. "Comparative Evaluation of Mechanical Properties of Dental Nanomaterials." Journal of Nanomaterials 2017 (2017): 1–8. http://dx.doi.org/10.1155/2017/6171578.

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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.

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37

Zimmermann, Katrin, and Gerold A. Schneider. "Elastic to elastic–plastic transition of Al2O3/TiC ceramics studied by nanoindentation." Journal of Materials Research 24, no. 6 (June 2009): 1960–66. http://dx.doi.org/10.1557/jmr.2009.0234.

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In this work load–penetration curves obtained by nanoindentation were analyzed, using a spherical tip approximation and applying the stress/strain concept by Tabor. Nanoindentation experiments were done on sapphire, pure TiC, and a mixed ceramic with in situ formed TiCx layer, using a sharp cube-corner indenter at very low loads and penetration depths. With the implemented method it is possible to display the elastic to elastic–plastic transition of each investigated phase, and much more information can be extracted than by conventional analysis. Regarding the mixed ceramic, it was found that the present TiC phases exhibit slightly lower hardness than the alumina phase, but they can sustain much higher stresses during the transition from the elastic to the elastic–plastic regime. This is considered to be beneficial for the application as cutting material. No correlation was found between the nanomechanical behavior of the model materials sapphire and TiC and the corresponding phases of the mixed ceramic.

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38

Ishimoto, Takuya, and Takayoshi Nakano. "Evaluation of Mechanical Properties of Regenerated Bone by Nanoindentation Technique." Materials Science Forum 654-656 (June 2010): 2220–24. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.2220.

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To evaluate the material parameters of regenerated bone, it is important to clarify the mechanical performance of the regenerated portion. In general, the shape and size of regenerated bone tissue is heterogeneous. It is often difficult to elucidate material properties by means of conventional mechanical tests such as compressive and/or tensile tests and bending tests. The nanoindentation technique has been utilized to evaluate the material properties of small or microstructured materials because they do not necessarily require a large well-designed specimen. Thus, this technique may be useful for the evaluation of the material properties of regenerated bone tissue. In this study, this technique was applied for the assessment of the Young’s modulus and hardness of regenerated and intact long bones of a rabbit. The regenerated bone exhibited a significantly lower Young’s modulus and hardness than the intact bone. The regenerated long bone also exhibited impaired mechanical properties, which may have been caused by the difference in the nano-organization of its collagen fibers and mineral crystals (the main components of bone tissue), from that of the intact bone.

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Dey, Arjun, and Anoop Kumar Mukhopadhyay. "Nanoindentation Study of Phase-pure Highly Crystalline Hydroxyapatite Coatings Deposited by Microplasma Spraying." Open Biomedical Engineering Journal 9, no. 1 (February 27, 2015): 65–74. http://dx.doi.org/10.2174/1874120701509010065.

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The present contribution has originated from a critical biomedical engineering issue e.g., loosening of metallic prostheses fixed with poly(methylmethylacrylate) (PMMA) bone cement especially in the case of hip joint replacement which ultimately forces the patient to undergo a revision surgery. Subsequently surgeons invented a cementless fixation technology introducing a bioactive hydroxyapatite (HAp) coating to the metallic implant surface. A wide variety of different coating methods have been developed to make the HAp coating on metallic implants more reliable; of which ultimately the plasma spraying method has been commercially accepted. However, the story was not yet finished at all, as many questions were raised regarding coating adherence, stability and bio-functionality in bothin vitroandin vivoenvironments. Moreover, it has been now realized that the conventional high power plasma spraying (i.e. conventional atmospheric plasma spraying, CAPS) coating method creates many disadvantages in terms of phase impurity; reduced porosity limiting osseointegration and residual stresses which ultimately lead to inadequate mechanical properties and delamination of the coating. Further, poor crystallinity of HAp deposited by CAPS accelerates the rate of bioresorption, which may cause poor adhesion due to quick mass loss of HAp coatings. Therefore, in the present work a very recently developed method e.g., low power microplasma spraying method was utilized to coat HAp on SS316L substrates to minimize the aforementioned problems associated with commercial CAPS HAp coatings. Surgical grade SS316L has been chosen as the substrate material because it is more cost effective than Ti6Al4V and CoCrMo alloys.

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Wang, Hao, Abhijeet Dhiman, Halsey E. Ostergaard, Yang Zhang, Thomas Siegmund, Jamie J. Kruzic, and Vikas Tomar. "Nanoindentation based properties of Inconel 718 at elevated temperatures: A comparison of conventional versus additively manufactured samples." International Journal of Plasticity 120 (September 2019): 380–94. http://dx.doi.org/10.1016/j.ijplas.2019.04.018.

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Nikaeen, Peyman, Dilip Depan, and Ahmed Khattab. "Surface Mechanical Characterization of Carbon Nanofiber Reinforced Low-Density Polyethylene by Nanoindentation and Comparison with Bulk Properties." Nanomaterials 9, no. 10 (September 22, 2019): 1357. http://dx.doi.org/10.3390/nano9101357.

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Surface mechanical properties of low-density polyethylene (LDPE) reinforced by carbon nanofibers (CNFs) up to 3% weight load were investigated using nanoindentation (NI). Surface preparation of the nanocomposite was thoroughly investigated and atomic force microscopy (AFM) was used to analyze the surface roughness of the polished surfaces. The dispersion of nanofillers in the LDPE matrix was examined using scanning electron microscopy (SEM). The effect of various penetration loads on the results and scattering of the data points was discussed. It was found by NI results that the addition of 3% weight CNF increased the elastic modulus of LDPE by 59% and its hardness up to 12%. The nano/micro-scale results were compared with macro-scale results obtained by the conventional tensile test as well as the theoretical results calculated by the Halpin-Tsai (HT) model. It was found that the modulus calculated by nanoindentation was twice that obtained by the conventional tensile test which was shown to be in excellent agreement with the HT model. Experimental results indicated that the addition of CNF to LDPE reduced its wear resistance property by reducing the hardness to modulus ratio. SEM micrographs of the semicrystalline microstructure of the CNF/LDPE nanocomposite along with the calculated NI imprints volume were examined to elaborate on how increasing the penetration depth resulted in a reduction of the coefficient of variation of the NI data/more statistically reliable data.

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42

Kim, Am Kee, Md Anwarul Hasan, Hak Joo Lee, and Seong Seock Cho. "Characterization of Submicron Mechanical Properties of Al-Alloy Foam Using Nanoindentation Technique." Materials Science Forum 475-479 (January 2005): 4199–202. http://dx.doi.org/10.4028/www.scientific.net/msf.475-479.4199.

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Nanoindentation test has been performed to characterize the mechanical properties of aluminium alloy foam cell wall. Two of the mechanical properties: hardness and Young’s modulus of cell wall material were evaluated using the stiffness of contact during both loading and unloading. Properties obtained from unloading stiffness were in better agreement with the conventional test result than those obtained from loading stiffness. The finite element analysis using nonlinear finite element code ABAQUS was performed to characterize the yield strength and the stress-strain curve of the cell wall material of the foam. Properties of foam cell wall material were found to be substantially different from the properties of the material before foaming. The methodology used in this paper can be effectively used to characterize the mechanical properties of cell wall of any cellular material.

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Natova, Margarita, Ivan Ivanov, Sabina Cherneva, Maria Datcheva, and Roumen Iankov. "Evaluation by nanoindentation of technological products manufactured by pulse injection molding process." MATEC Web of Conferences 145 (2018): 02006. http://dx.doi.org/10.1051/matecconf/201814502006.

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During conventional polymer injection molding, flow- and weld lines can arise at the molded parts caused by disturbed polymer melt flow when it crosses different parts of the equipment. Such processed plastic goods have discrete zones of inhomogeneities of very small dimensions. In order to stabilize the melt flow and to equalize dimensions of such defective products, an approach for pulse injection molding is applied during production of polymer packagings. Testing methods used for evaluation of macromechanical performance of processed polymer products are not readily applicable to estimate the changes in visual surface obtained during pulse injecting. To overcome this testing inconvenience the performance of processed packagings is evaluated by nanoindentation. Using this method, a quantitative assessment of the polymer properties is obtained from different parts of technological products.

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Fu, Kun Kun, Yuan Chang, Li Chang, and Bai Lin Zheng. "An Improved Indentation Method for Estimating Limits of Fracture Toughness in Brittle Films." Advanced Materials Research 1095 (March 2015): 598–602. http://dx.doi.org/10.4028/www.scientific.net/amr.1095.598.

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We previously presented an energy method for predicting the bounds of fracture toughness of brittle films on a soft substrate from nanoindentation. The method is now further improved by minimizing elastic-plastic work from the measured energy during ring crack formation. Then, we applied this method to determine the limits of fracture toughness of alumina films with a thickness of 100 nm. It was found that fracture toughness of the films is in the range of 1.8-2.2 MPa.m0.5, which is consistent with those measured by the conventional method.

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Li, Jia, QiHong Fang, Bin Liu, YouWen Liu, and Yong Liu. "Atomic-scale analysis of nanoindentation behavior of high-entropy alloy." Journal of Micromechanics and Molecular Physics 01, no. 01 (April 2016): 1650001. http://dx.doi.org/10.1142/s2424913016500016.

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Using molecular dynamics simulations, we study the elastic and plastic deformations of indentation in FeCrCuAlNi high-entropy alloy (HEA). The indentation tests are carried out using spherical rigid indenter to investigate the effects of high-entropy and severe lattice distortion in terms of shear strain, indentation force, surface morphology, defect structure, dislocation evolution and radial distribution function on the deformation processes. It can be found that when the indentation depth increases, the shear stress requires for the occurrence of the contact area between the indenter and the substrate increased, which is attributable to a higher probability to observe the dislocation evolution under a large indentation depth. The indentation test also shows that the equal element addition can significantly improve the mechanical properties of HEA compared with the conventional alloy. Based on the Hertzian fitting, the FeCrCuAlNi HEA has the Young’s modulus of 161[Formula: see text]GPa and hardness of 15.4[Formula: see text]GPa, respectively. These values are higher than that of traditional metal materials, due to the low stacking fault energy and the dense atomic arrangement in the slip plane of HEA. In the plastic region, the Fe element causes the more stable crystal structure, much stronger than the Cu element, presumably resulted from a variety of crystal structures for Fe in the multicomponent FeCrCuAlNi alloy. Further, this effective strategy is used to accelerate the discovery of excellent mechanical properties of HEAs.

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Quinn, George D. "Fractographic Analysis of Very Small Theta Specimens." Key Engineering Materials 409 (March 2009): 201–8. http://dx.doi.org/10.4028/www.scientific.net/kem.409.201.

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The theta test specimen is a versatile tool for evaluating the strength of extremely small structures. Round and hexagonal rings are compressed vertically on their ends creating a uniform tension stress in the middle gauge section. The simple compression loading scheme eliminates the need for special grips. A conventional nanoindentation hardness machine with a flat indenter applied load, monitored displacement, and recorded fracture loads. Prototype miniature specimens with web sections as thin as 7.5 m were fabricated by deep reactive ion etching (DRIE) of single crystal silicon wafers. The strength limiting flaws were 200 nm to 500 nm deep surface etch pits.

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Khlifi, Kaouthar, Hafedh Dhifelaoui, Lassaad Zoghlami, and Ahmed Ben Cheikh Larbi. "Multi-Cycle Nanoindentation Studies on TiN/TiAlN Nano-Multilayer Coating: Effects of Mechanical Properties and Coating Structure." Applied Mechanics and Materials 798 (October 2015): 367–71. http://dx.doi.org/10.4028/www.scientific.net/amm.798.367.

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TiAlN/TiN nanomultilayer coating was deposited on 100C6 steel (AISI 52100) substrate with the PVD technique using magnetron sputtering. Morphological examination showed the presence of domes and craters which are uniformly distributed over the entire surface.Microstructural observations revealed a columnar structure. Mechanical properties, plastic and elastic deformation resistance of TiAlN/TiN multilayer coating were studied using conventional indentation method. Multi-cycle nanoindentation technique, with variation of loading rate, was used to analyze the failure modes and mechanical behavior of TiN/TiAlN 200 cycles were performed and when the loading rate was increased from 200mN/mn to 600mN/mn, the mechanical proprieties were decreased.

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Kawasaki, Megumi, and Terence G. Langdon. "Superplasticity in Ultrafine-Grained Materials." REVIEWS ON ADVANCED MATERIALS SCIENCE 54, no. 1 (March 1, 2018): 46–55. http://dx.doi.org/10.1515/rams-2018-0019.

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Abstract Superplasticity refers to the ability of a polycrystalline solid to exhibit a high elongation, of at least 400% or more, when testing in tension. The basic characteristics of superplastic flow are now understood and a theoretical model is available to describe the flow process both in conventional superplastic materials where the grain sizes are a few micrometers and in ultrafinegrained materials processed by severe plastic deformation where the grain sizes are in the submicrometer range. This report describes the basic characteristics of superplastic metals, gives examples of flow in ultrafine-grained materials, demonstrates the use of deformation mechanism mapping for providing a visual display of the flow processes and provides a direct comparison with the conventional model for superplastic flow. The report also describes the potential for using nanoindentation to obtain detailed information on the flow properties using only exceptionally small samples.

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Konstantopoulos, Georgios, Elias P. Koumoulos, and Costas A. Charitidis. "Testing Novel Portland Cement Formulations with Carbon Nanotubes and Intrinsic Properties Revelation: Nanoindentation Analysis with Machine Learning on Microstructure Identification." Nanomaterials 10, no. 4 (March 30, 2020): 645. http://dx.doi.org/10.3390/nano10040645.

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Nanoindentation was utilized as a non-destructive technique to identify Portland Cement hydration phases. Artificial Intelligence (AI) and semi-supervised Machine Learning (ML) were used for knowledge gain on the effect of carbon nanotubes to nanomechanics in novel cement formulations. Data labelling is performed with unsupervised ML with k-means clustering. Supervised ML classification is used in order to predict the hydration products composition and 97.6% accuracy was achieved. Analysis included multiple nanoindentation raw data variables, and required less time to execute than conventional single component probability density analysis (PDA). Also, PDA was less informative than ML regarding information exchange and re-usability of input in design predictions. In principle, ML is the appropriate science for predictive modeling, such as cement phase identification and facilitates the acquisition of precise results. This study introduces unbiased structure-property relations with ML to monitor cement durability based on cement phases nanomechanics compared to PDA, which offers a solution based on local optima of a multidimensional space solution. Evaluation of nanomaterials inclusion in composite reinforcement using semi-supervised ML was proved feasible. This methodology is expected to contribute to design informatics due to the high prediction metrics, which holds promise for the transfer learning potential of these models for studying other novel cement formulations.

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Pierson, Gaël, M’Barek Taghite, Pierre Bravetti, and Richard Kouitat Njiwa. "Spherical Indentation of a Micropolar Solid: A Numerical Investigation Using the Local Point Interpolation–Boundary Element Method." Applied Mechanics 2, no. 3 (August 21, 2021): 581–90. http://dx.doi.org/10.3390/applmech2030033.

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The load-penetration curve in elastic nanoindentation of an elastic micropolar flat by a diamond spherical punch is analyzed. The presented results are obtained by a specifically developed numerical tool based on a judicious combination of the conventional boundary element method and strong form local point interpolation method. The results show that the usual linear relationship between the material depression and the square of the radius of the contact area is also valid in this case of micropolar elastic material. It is also shown that the relation between the indentation stress (applied load over the contact surface) and the indentation strain (ratio of contact radius by the punch radius) is linear. The proportionality coefficient which is none other than the indentation stiffness varies with the coupling factor of the micropolar elastic medium. A relation between the indentation stiffness of a micropolar solid and that of a conventional solid with the same Young modulus and Poisson ratio is derived.

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Journal articles on the topic 'Conventional nanoindentation'

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