Nanoindentation Research Papers - Academia.edu (original) (raw)

Corrosion induced failure of buried ferrous pipelines causes significant economic losses to the world. Many of the existing buried water pipelines are made of ductile iron in most of the developed countries. Literature shows that the... more

Corrosion induced failure of buried ferrous pipelines causes significant economic losses to the world. Many of the existing buried water pipelines are made of ductile iron in most of the developed countries. Literature shows that the research on the corrosion-induced degradation assessments of ductile iron pipelines is limited and mostly deals with the physical deterioration i. e., loss of wall thickness determined by short-term research. This paper addresses this gap and presents a comparatively long-term study on the corrosion and its subsequent effect on the composition and nanomechanical properties of buried ductile iron pipelines in the accelerated corrosive environment. For experimentation, ductile iron specimens were immersed in the acidic simulated soil solution for 365 days. Physical deterioration assessment over the time was carried out in terms of corrosion rates measured at intervals of 180 and 365 days. A significant change in the percentage composition of key elements and phases were quantified. Furthermore, the mechanical properties of the grains were found to be considerably reduced after 365 days of immersion in the acidic environment by the nanoindentation technique. The results revealed an alarming increase of structural degradation at nano scale for some of the grains due to chloride induced localised corrosion. The significance of the current research is its in-depth analysis of the corrosion-induced degradation of ductile iron pipes which enhances the knowledge related to the failure of these pipelines.

Porous pre-sintered zirconia is subject to white machining during which its elasticity, plasticity and resistance to machining-induced damage determine its machinability and final quality. This study used nanoindentation techniques and... more

Porous pre-sintered zirconia is subject to white machining during which its elasticity, plasticity and resistance to machining-induced damage determine its machinability and final quality. This study used nanoindentation techniques and the Sakai's series elastic and plastic deformation model to extract the resistance to plastic deformation from the plane strain modulus and the contact hardness for pre-sintered zirconia. The modulus and the resistance to plasticity were used to calculate the relative amount of elasticity and plasticity. The fracture energy and the normalized indentation absorbed energy were used to deconvolute the resistance to machining-induced cracking based on the Sakai–Nowak model. All properties were extracted at a 10 mN peak load and loading rates of 0.1–2 mN/s to determine the loading rate effects on these properties. We found that the resistance to plasticity and the resistance to machining-induced cracking were independent of the loading rate (ANOVA, p > 0.05). The elastic and plastic displacements depended on the loading rate through power laws. This loading rate-dependent deformation behaviour was explained by the maximum shear stress generated underneath the indenter and the indentation energy. The plastic deformation components and the indentation absorbed energy at all loading rates were higher than the elastic deformation components and the elastic strain energy, respectively. Finally, we established the linkage among the pore structure, indentation behaviour and machinability of pre-sintered zirconia.

Similar and dissimilar welds of dual-phase (DP) and high strength low alloy (HSLA) steels were made by fiber laser welding (FLW). The welds were characterized with respect to microstructure, micro- and nano-hardness, and tensile... more

Similar and dissimilar welds of dual-phase (DP) and high strength low alloy (HSLA) steels were made by fiber laser welding (FLW). The welds were characterized with respect to microstructure, micro- and nano-hardness, and tensile properties. The fusion zone (FZ) in the DP welds consisted of fully martensitic structure; whereas HSLA and dissimilar weld FZ microstructure were mixture of martensite and bainite. Analytical transmission electron microscopy (TEM) confirmed bainite structures containing bainitic ferrite laths with intralath and interlath cementite. Precipitation of single variant carbides inside the bainitic ferrite laths were confirmed by measuring the interplanar spacing. The cooling rate in the FZ, estimated using Rosenthal equation, and continuous-cooling-transformation diagrams corroborated the microstructure formed. Nanoindentation was used to verify the hardness of these individual microconstituents, since a much lower nano-hardness for bainite (4.11 GPa) was observed compared to martensite (6.57 GPa) phase. Tensile failure occurred in the tempered area of the heat affected zone (HAZ) in the DP steel welded, which was confirmed by typical cup-like dimple fracture; likewise failure in the HSLA base metal, which occurred in dissimilar and HSLA welds, indicated distinctive dimple and shear dimple ductile morphology.

The global demand for lightweight design is increasing to provide sustainable solutions to counteract climate change. We developed a novel Ti-bearing lightweight steel (8% lower mass density than general steels), which exhibits an... more

The global demand for lightweight design is increasing to provide sustainable solutions to counteract climate change. We developed a novel Ti-bearing lightweight steel (8% lower mass density than general steels), which exhibits an excellent combination of strength (491 MPa ultimate tensile strength) and tensile ductility (31%) at elevated temperature (600 • C). The developed steel is suitable for parts subjected to high temperature at reduced dynamical load. The composition of the developed steel (Fe-20Mn-6Ti-3Al-0.06C-NbNi (wt%)) lends the alloy a multiphase structure with austenite matrix, partially ordered ferrite, Fe 2 Ti Laves phase, and fine MC carbides. At elevated temperature (600 • C), the ductility of the new material is at least 2.5 times higher than that of conventional lightweight steels based on the Fe-Mn-Al system, which become brittle at elevated temperatures due to the inter/intragranular precipitation of κ-carbides. This is achieved by the high thermal stability of its microstructure and the avoidance of brittle κ-carbides in this temperature range.

The pop-in behavior and mechanical properties of sapphire crystal vertically indented to its rhombohedral R (10 12) plane were investigated by nanoindentation using a Berkovich indenter. Effect of loading rate on pop-in load and pop-in... more

The pop-in behavior and mechanical properties of sapphire
crystal vertically indented to its rhombohedral R (10 12) plane
were investigated by nanoindentation using a Berkovich indenter. Effect of loading rate on pop-in load and pop-in extension width was observed within the indentation depth of
h < 120 nm. The indentation size effect (ISE) of hardness
within an indentation depth of 60 nm was systematically analyzed using Nix-Gao and Al-Rub models. Our experiments provided the consistent evaluations of hardness (H = 27.5 GPa),
true hardness (Htrue = 68.9 GPa) at the non-ISE region and
effective indentation modulus (M = 423 GPa) for the contact
depth of hc > 20 nm. Using the Hertzian contact theory, Schmid’s law, and energy principle of indentation, the possible
dominant slip system, which mainly contributed to the first
pop-in event when indented normal to the (10 12) plane, was
estimated as {10 11} < 12 10>. The distributions of corresponding resolved shear stress and principal stresses at the slip plane were also estimated.

Ti-Al-N coatings were deposited on high-speed steel substrates by filtered vacuum arc deposition (FVAD) during evaporation of aluminum and titanium cathodes. Distribution of elements, phase composition, and mechanical properties of... more

Ti-Al-N coatings were deposited on high-speed steel substrates by filtered vacuum arc deposition (FVAD) during evaporation of aluminum and titanium cathodes. Distribution of elements, phase composition, and mechanical properties of Ti-Al-N coatings were investigated using Auger electron spectroscopy (AES), X-ray diffraction (XRD), transmission electron microscopy (TEM) and nanoindentation, respectively. Additionally, tribological tests and scratch tests of the coatings were performed. The stoichiometry of the coating changes from Ti 0.6 Al 0.4 N to Ti 0.48 Al 0.52 N with increasing aluminum arc current from 70 A to 90 A, respectively. XRD and TEM showed only face-centered cubic Ti-Al-N phase with preferred orientation of the crystallites in (220) direction with respect to the sample normal and without precipitates of AlN or intermetallics inside the coatings. Incorporation of Al into the TiN lattice caused shifting of the (220) reflex to a higher 2θ angle with increasing Al content. Low content and size of microdroplets were obtained using coaxial plasma filters, which provides good mechanical and tribological properties of the coatings. The highest value of microhardness (36 GPa) and the best wear-resistance were achieved for the coating with higher Al content, thus for Ti 0.48 Al 0.52 N. These coatings exhibit good adhesive properties up to 30 N load in the scratch tests.

Effects of Mn and Ti additives on the microstructure and solidification behavior of Sn–1.0Ag–0.5Cu alloys (SAC105), as well as mechanical properties, were investigated in this study. Results show that alloying of Mn and Ti resulted in... more

Effects of Mn and Ti additives on the microstructure and solidification behavior of Sn–1.0Ag–0.5Cu alloys (SAC105), as well as mechanical properties, were investigated in this study. Results show that alloying of Mn and Ti resulted in dramatically reduced undercooling, coarse eutectic structure and extended volume fraction of proeutectic Sn of which the dendritic size was refined. Those thermal and microstructural changes might be ascribed to the formation of MnSn2 and Ti2Sn3 intermetallic compounds (IMCs) which appeared respectively in the Mn-doped and Ti-doped samples. Nanoindentation tests demonstrated that the heterogeneous IMCs produced by alloying were harder and stiffer than the inherent IMCs, Ag3Sn and Cu6Sn5. Worthy of notice is that the elastic modulus of SAC105 alloys decreased with only a minor alloying addition due to the shrunken eutectic regions and coarsened eutectic microconstituents. With a larger quantity of additives, an ascending elastic modulus could be obtained because of the strengthening effect by hard heterogeneous compounds.

Coating growth and mechanical properties of nanolamellar Cr 2 AlC coatings at various sputtering power were investigated in the present study. Cr 2 AlC coating was deposited on the IN 718 superalloy and (100) Si wafers by DC magnetron... more

Coating growth and mechanical properties of nanolamellar Cr 2 AlC coatings at various sputtering power were investigated in the present study. Cr 2 AlC coating was deposited on the IN 718 superalloy and (100) Si wafers by DC magnetron sputtering at different sputtering powers. The structure and properties were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nanoindentation. It was found that coatings had columnar structure with nanocrystalline substructure. Deposition rate increased with the sputtering power. XRD results showed the presence of the Cr 2 AlC MAX phase, intermetallic AlCr 2 and Cr 7 C 3 carbide phases, along with the change in preferential coating growth orientation. TEM observations confirmed the occurrence of these phases, and the SAED patterns demonstrated significant texture of the coatings. Hardness values were measured in the range between 11–14 GPa, showing a slight increase with the sputtering power.

The pH of an aqueous solution of a low molecular weight gelator can be adjusted through the hydrolysis of a number of anhydrides to the corresponding acids. The rate of hydrolysis and hence of pH change can be used to control the rate of... more

The pH of an aqueous solution of a low molecular weight gelator can be adjusted through the hydrolysis of a number of anhydrides to the corresponding acids. The rate of hydrolysis and hence of pH change can be used to control the rate of gel formation. This rate does not affect the primary assembly of the low molecular weight gelator, but does affect the mechanical properties of the resulting gels, as well as the homogeneity and reproducibility of the gels. The mechanical properties are compared by both rheology and dynamic nanoindentation.

Densely crosslinked glassy epoxies such as SU-8, are increasingly being used as thin films and micro-sized and nano-sized cantilevers for sensing applications. Hence, there is a need to develop a robust understanding of localized and... more

Densely crosslinked glassy epoxies such as SU-8, are
increasingly being used as thin films and micro-sized and
nano-sized cantilevers for sensing applications. Hence,
there is a need to develop a robust understanding of
localized and contextual mechanical response of such
epoxies. Nanoindentation experiments, and their
appropriate data interpretation, can provide for such an
understanding. However, refinements are necessary to the
conventionally employed Oliver-Pharr method, to
estimate accurately the elastic modulus and hardness; e.g.,
accurate estimates of the time-varying contact area, or
direct modeling of the load-displacement relationship. We
propose here preliminary development of a constitutive
model, containing direct load-displacement (instead of
stress, strain and strain rate) mechanical elements: springs,
dashpots, and slider. This model aims to capture the functional form as well as the multiple nonlinear, time dependent phenomena occurring during SU-8 nanoindentation. We also report here preliminary DSC, XRD, and Laser-Raman spectroscopy characterization of our samples.

In this paper, a developed three-dimensional Molecular Dynamics (MD) model for AFM-based nanomachining is applied to study mechanical indentation and scratching at the nanoscale. The correlation between the machining conditions, including... more

In this paper, a developed three-dimensional Molecular Dynamics (MD) model for AFM-based nanomachining is applied to study mechanical indentation and scratching at the nanoscale. The correlation between the machining conditions, including applied force, depth, tip speed, and defect mechanism in substrate/workpiece is investigeted. The simulations of nanoscratching process are performed on different crystal orientations of single-crystal gold substrate, Au(100), Au(110), and Au(111). The material deformation and deformed geometry are extracted from the final locations of atoms, which are displaced by the rigid indenter. The simulation also allows for the prediction of forces at the interface between the indenter and substrate. Material properties including modulus of elasticity and hardness are estimated. It is found that properties vary significantly at the nanoscale. In addition to the modeling, an AFM is used to conduct actual indentation and scratching at the nanoscale, and provide measurements to which the MD simulation predictions are compared. Due to computational time limitation, the predicted forces obtained from MD simulation only compares well qualitatively with the experimental results.

INTRODUCTION: Bone is a highly intricate material with a complex hierarchical fabrication from the cellular level to the networks to bone tissues which are pronominally made up of collagen. In this study, mice bone specimens from the tm1a... more

INTRODUCTION: Bone is a highly intricate material with a complex hierarchical fabrication from the cellular level to the networks to bone tissues which are pronominally made up of collagen. In this study, mice bone specimens from the tm1a Col1a2 null line were tested to investigate the micromechanical properties of bone. Three genotypes of bone specimen samples were used in this study: (‘Wild type’ (WT) which is made from normal collagen, Knock Out’ (KO) which is made from abnormal collagen and heterozygous (HET), which is made of normal and abnormal collagen).
AIM: The aim of this project was to investigate the role of collagen mutation on bone micromechanics.
METHODOLOGY: Using the materialographic specimen preparation for mammalian bone, the preparation of bone specimen samples (WT, KO and HET) was done in a step by step approach. The G200 Nanoindenter was used to obtain elastic modulus (EM) and hardness (H) data using the Berkovich tip and the Oliver-Pharr method. Optical images were also obtained from the same machine using the live-feed optical microscope embedded in the Nanoindenter. Measurements of the cortical thickness of each specimen samples were obtained using ‘image J’ software. SEM was used to investigate the micro and nanostructure of the specimen samples; and statistical analysis was done for raw data obtained from nanoindentation using ‘OriginPro’ software to examine trends in EM and H data.
RESULTS: There is a direct correlation between the elastic modulus (EM) and hardness (H) of the specimen samples used in this study. With an R2 value of 0.73, the correlation between EM and H are statistically significant. The combined ♂ and ♀ data indicates that the EM of WT is lower than KO in both 10s and 100s hold periods and Het has a lower EM compared to WT and KO in both hold periods. The combined ♂ and ♀ H data indicates KO having the highest H data and Het genotype having the lowest H data. When separated by gender, for male EM, the correlation between all different comparisons observed were statistically significant except in the comparison between WT and KO. The H data for all comparisons does not show any statistically significant difference. The female EM data showed statistically different comparison between the WT vs KO vs Het and WT vs Het data. However, there was no significant difference between WT vs KO and KO vs Het. The H data also indicates that only the 100s hold period for WT vs Het comparison was significant.
CONCLUSION: Data from nanoindentation indicates that the EM data for Het genotype in ♂ and ♀ (for both 10s and 100s hold periods) is affected by collagen mutation. The imaging experiments also indicate a similar trend.