Depth-sensing Indentation Research Articles

Comparison of nanoindentation techniques for local mechanical quantification of aluminium alloy

Nanoindentation is widely used for the assessment of micromechanical behaviour of multiple phases within the material microstructure. Structural materials typically exhibit large variations in elastic modulus and hardness with increasing indentation depth during depth-sensing indentation experiments because the measured stiffness response is affected by its heterogeneity. In this study, the complicated microstructure of heterogeneous aluminium foam cell walls is described and related micromechanical analyses using various characterization modes performed. The paper compares the results of several nanoindentation approaches for the assessment of hardness and elastic parameters using both the quasi-static indentation and the dynamic modulus mapping method. The results of quasi-static indentation were performed for two different indenter geometries (Berkovich and spherical tips). The material phase properties were analysed with grid indentation method based on statistical evaluation of a large number of indentations (statistical deconvolution technique) as well as with isolated indentations by spherical indenter that revealed overall properties of the foam cell wall. Special attention was paid to the volume affected by the indenter and other factors influencing reliable evaluation of nanoindentation measurements. Intrinsic properties of the individual phases were also verified with modulus mapping technique. Results from the dynamic measurements were consistent with the values obtained in quasi-static measurements using the Berkovich indenter for both main microstructural phases.

Effect of Beta Low Irradiation Doses on the Filled PA66 Measured by Micro-Indentation Test

The presented article deals with the research of micro-mechanical properties in the surface layer of modified Polyamide 66 filled by 30% of glass fibers. These micro-mechanical properties were measured by the Depth Sensing Indentation - DSI method on samples which were non-irradiated and irradiated by different doses of the β - radiation. Radiation doses used were 0, 15, 30 and 45 kGy for filled Polyamide 66 with the 6% cross-linking agent (triallyl isocyanurate). Individual radiation doses caused structural and micro-mechanical changes which have a significant effect on the final properties of the polyamide 66 tested. The highest values of micro-mechanical properties were reached at radiation dose of 30 kGy, when the micro-hardness values increased by about 64%. The aim of the article is to find out the influence of the radiation on the micro-hardness of the modified glass fiber-filled Polyamide 66 (PA66).

Ionizing Radiation Effect of HDPE Measured by Nano-Hardness

This article deals with the influence of different doses of Beta radiation on nanomechanical properties of High-density polyethylene (HDPE). These nanomechanical properties were measured by the Depth Sensing Indentation - DSI method on samples which were non-irradiated and irradiated by different doses of the β - radiation. The highest values of nanomechanical properties were reached at radiation dose of 99 kGy, when the nanohardness values increased by about 23%. The purpose of the article is to consider to what extent the irradiation process influences the resulting nanomechanical properties measured by the Depth Sensing Indentation method.

Cylindrical lateral depth-sensing indentation testing of thin anisotropic elastic films

A two-dimensional frictionless contact problem for a parabolic indenter pressed against an orthotropic elastic strip resting on a frictionless rigid substrate is studied. The sixth-order asymptotic solution is obtained in the case of a relatively small contact zone with respect to the elastic strip thickness. The so-called cylindrical lateral indentation test, which utilizes lateral contact of a cylindrical indenter, is developed for indentation testing of a thin transversely isotropic film with the symmetry plane orthogonal to the contact plane under the assumption that the film thickness is small compared to the cylinder indenter length. The presented testing methodology is based on a least squares best fit of the second-order asymptotic model to the depth-sensing indentation data.

Deformation characteristics of WC micropillars

Abstract The mechanical response under nano-compression test of single crystal tungsten-carbide (WC) micropillars prepared by focused ion beam from oriented facets of WC grains in WC–Co system was investigated. Depth-sensing indentation and scanning electron microscopy were used for the micro-mechanical test and damage characterization, respectively. A strong influence of the orientation on Young's modulus, yield and rupture stress values was found, with higher values for pillars with axes orientated perpendicularly to the basal plane of the WC grains.

Effect of Different Production Methods on the Mechanical and Microstructural Properties of Hypereutectic Al-Si Alloys

In this study, the effects of different production methods like melt spinning, high-energy ball milling, and combined melt spinning and high-energy ball milling on the mechanical and microstructural properties of hypereutectic Al-20Si-5Fe alloys were investigated. While microstructural and spectroscopic analyses were performed using scanning electron microscopy and X-ray diffractometry, mechanical properties were measured using a depth-sensing indentation instrument with a Berkovich tip. Microstructural and spectroscopic analyses demonstrate that high-energy ball milling process applied on the melt-spun Al-20-Si-5Fe alloy for 10 minutes brings about a reduction in the size of silicon particles and intermetallic compounds. However, further increase in milling time does not yield any significant reduction in size. High-energy ball milling for 10 minutes on the starting powders is not enough to form any intermetallic phase. According to the depth-sensing indentation experiments, high-energy milling of melt-spun Al-20Si-5Fe alloys shows an incremental behavior in terms of hardness values. For the Al-20Si-5Fe alloys investigated in this study, the production technique remarkably influences their elastic–plastic response to the indentation process in terms of both magnitude and shape of P-h curves.

Deformation Behavior and Wear Resistance of Hard TiCN and TiCN/Ti Coatings on Ti6Al4V Alloy

Monolayer titanium carbide nitride (TiCN) and multilayer TiCN reinforced titanium (Ti) are coated on the surface of Ti6Al4V alloy by Filtered Arc Deposition System (FADS). Surface chemical composition has been characterized by an X-ray diffraction (XRD). Wear resistance of TiCN coating and TiCN/Ti coating have been detected by hommel tester T1000. Hardness and deformation mechanisms of the multilayer coatings are investigated using depth-sensing indentation comparison with the monolayer TiCN coatings. Focused Ion Beam (FIB) and Transmission Electron Microscopy (TEM) are used to identify the fracture modes of the coatings. The TEM image observations show that the inclined crack is the dominant crack in the monolayer TiCN coating while small bending crack is the dominant crack in the multilayer TiCN/Ti coating. The Ti layer with good ductility could efficiently suppress the crack propagation and absorb more indent energy.

Characterization of viscoelastic materials by quasi-static and dynamic indentation

This paper describes the experimental measurements of the elastic modulus and hardness of viscoelastic materials under quasi-static and dynamic depth-sensing indentation using a homemade tribology probe microscope (TPM). The indentation measurements were performed using a sapphire sphere tip under various conditions. Materials such as polytetrafluoroethylene, styrene rubber and nitrile rubber were tested in both quasi-static and dynamic experiments. In quasi-static mode, the loading and unloading force curves were obtained from these specimens, and the results show a significant load effect on the measured hardness and elastic modulus. The dynamic indentation tests were conducted under a range of loading forces with various frequencies. The values of storage modulus, loss modulus and damping factor were determined by dynamic indentation. To get an accurate measurement, the stiffness and damping of the instrument were rigorously analyzed. Using dynamic indentation, it was confirmed that the variation in the frequency of the oscillation force has a significant effect on the measured results of the materials. Comparing the results obtained from the quasi-static and dynamic indentations, for the viscoelastic properties, dynamic indentation offers an advantage over the quasi-static method. Collectively, these results clearly demonstrate the capability of our homemade TPM facility to determine the constitutive behavior of viscoelastic solids in the frequency domain.

Effect of Pile-Up on the Mechanical Characteristics of Steel by Depth Sensing Indentation

Mechanical properties by depth sensing indentation are derived from the indentation load-displacement data used a micromechanical model developed by Oliver & Pharr (O&P). However, O&P analysis on the indentation unloading curve is developed from a purely elastic contact mechanics (sink-in). The applicability of O&P analysis is limited by the materials pile-up. However, when it does, the contact area is larger than that predicted by elastic contact theory (material sinks-in during purely elastic contact), and both hardness H and Youngs modulus E are overestimated, because their evaluation depends on the contact area deduced from the load-displacement data. H can be overestimated by up to 60 % and E by up to 30 % depending on the extent of pile-up [1,2]. It is therefore important to determine the effect of pile-up on obtained mechanical characteristics of the material by depth sensing indentation. The work experimentally analyses the effect of pile-up height on mechanical characteristics H and E, which are determined by O&P analysis. Pile-up height was measured by atomic force microscopy (AFM).

Corelation of Results of Creep and Micro-Indentation Creep for PP-Copo

This article deals with the comparison of methods for measuring the creep behavior of filled polypropylene. Creep was measured by two methods, using the micro-indentation method (Depth Sensing Indentation - DSI) and the standard long-term creep test at elevated temperature. Results of this article show the feasibility of these two methods to replace each other and thus shorten the length of the testing material development with evaluation whether the test material is better or worse than the previous. Using the DSI method we can evaluated other material properties at the same time, which may be an important contributor in determining an appropriate application of the material. Mixtures of polypropylene with different kinds and levels of filling were selected for the comparison.

Micro-Hardness and Morphology of LDPE Influenced by Beta Radiation

This article deals with the influence of different doses of Beta radiation to the structure and mico-mechanical properties of Low-density polyethylene (LDPE). Hard surface layers of polymer materials, especially LDPE, can be formed by radiation cross-linking by β radiation with doses of 33, 66 and 99 kGy. Material properties created by β radiation are measured by micro-hardness test using the DSI method (Depth Sensing Indentation). Individual radiation doses caused structural and micro-mechanical changes which have a significant effect on the final properties of the LDPE tested. The highest values of micro-mechanical properties were reached at radiation dose of 66 and 99 kGy, when the micro-hardness values increased by about 21%. The changes were examined and confirmed by X-ray diffraction.

Energy Aspects of Concentrated Contact and Instrumented Indentation

The paper gives a brief overview of various energy approaches and possibilities they offer. Most of it is illustrated on examples from depth-sensing indentation. Components of contact work are listed, and the relationships between these components and material characteristics are given. Also the solution of impact problems is shown, based on the law of energy conservation. Finally, the role of surface energy and adhesion is mentioned.

Influence of the Microstructure on Macro/Micro<i> versus</i> Nanohardness of SiC Ceramics

The influence of microstructural variations on the macro/microhardness, nanohardness and Young`s modulus of liquid phase sintered silicon carbide (LPS SiC) has been observed. In order to modify the microstructures some samples were further heat treated at 1850°C for 5 hours to promote grain growth. The depth-sensing indentation tests of SiC materials were performed at several peak loads in the range 10-400 mN. For a better assessment, the indentation values of hardness and Young`s modulus modulus of SiC matrix were also compared to the hardness and Elastic modulus of individual SiC grains. The comparison of macro/micro and nanohardness showed that nanohardness was significantly higher, generally by 6-7 GPa. The nanohardness of individual plate-like SiC grains was around 2 GPa higher than nanohardness of SiC matrix.

Thermal stability and mechanical properties of the TiCuZrPd glasses with 10, 14 and 20 at.% Pd

Metallic glasses of the composition Ti40Zr10Cu40−xPd10+x with x=0, 4 and 10, were investigated from the point of view of the thermal stability, crystallization and hardness. The samples in the form of melt spun ribbons and rods 2.8mm in diameter, were characterized by differential scanning calorimetry (DSC), Thermo-Mechanical Analysis (TMA), macro-Vickers hardness (MHv10) and depth-sensing indentation measurements. The TMA experiments were performed on ribbons in the modulated constant load tensile mode. The processes of relaxation, glass transition and crystallization were observed with DSC and transmission electron microscopy (TEM). The relative length changes rates as a function of temperature (dL/dTL0) showed influence of the thermal stability of the amorphous phase on the materials ductility. High ductility was available in the wide range of temperature including primary crystallization range. Vickers-macrohardness of BMG was about 5500MPa and nanohardness was about 9300MPa, increasing after crystallization completion by about 18%. At small nanoindentation rates deformed amorphous phase revealed local plastic instability resulting from the shear bands formation.

The Material Mechanical Properties Reverse Calculation Method Bases on Depth-Sensing Indentation

It introduced the depth-sensing indentation principle,characteristics,and the major applications and advantages in micromechanical properties and damage research. It focused on analyzing the typical load-depth test curve from the material depth-sensing indentation experiment, then talked about how the curve was used in the reverse calculation process for material mechanics properties.It can provide the technology route reference for the other metal mechanical properties research in the future.

Microstructure-Related Scratch Resistance and Indentation Creep Behavior of PA6 and PA6 Nanocomposites

Instrumented scratch test was carried out to determine the scratch resistance of polyamide 6 (PA 6) nanocomposites, where two kinds of nanofillers were tested, both based on silicates: montmorillonite (MMT) and halloysite nanotubes (HNT). In this work the influence of the sliding velocity, normal applied load and time-dependent recovery on the penetration depth and scratch hardness was investigated. Optical microscopy was utilized to determine the width of the scratch grooves and scanning electron microscopy revealed the damage features of the scratched surfaces. Both MNT and HNT nanofillers improve the scratch resistance of PA 6 considerably. As a result of the microstructure of the polymer nanocomposites MNT gives PA 6 a better residual depth resistance while HNT raises its scratch hardness (i.e. reduces the scratch width). Furthermore, via different depth-sensing indentation techniques in the nano-, micro- and macro-range of loading the short-term performance (Martens hardness and indentation modulus) and the time-dependent creep behavior have been analyzed for PA 6 and the PA 6 nanocomposites as a function of applied load and temperature. Additionally, WAXS (wide-angle X-ray scattering) and DSC (differential scanning calorimetry) measurements to establish morphology–property relationships of the materials investigated considering the skin–core structure of the injection molded samples were made.

Evaluating the Reinforcement of Inorganic Fullerene-like Nanoparticles in Thermoplastic Matrices by Depth-Sensing Indentation

The reinforcing effect of inorganic fullerene-like tungsten disulfide (IF-WS2) nanoparticles in two different polymer matrices, isotactic polypropylene (iPP) and polyphenylene sulfide (PPS), has been investigated by means of dynamic depth-sensing indentation. The hardness and elastic modulus enhancement upon filler addition is analyzed in terms of two main contributions: changes in the polymer matrix nanostructure and intrinsic properties of the filler including matrix-particle load transfer. It is found that the latter mainly determines the overall mechanical improvement, whereas the nanostructural changes induced in the polymer matrix only contribute to a minor extent. Important differences are suggested between the mechanisms of deformation in the two nanocomposites, resulting in a moderate mechanical enhancement in case of iPP (20% for a filler loading of 1%), and a remarkable hardness increase in case of PPS (60% for the same filler content). The nature of the polymer amorphous phase, whether in the ...

Depth-sensing indentation applied to polymers: A comparison between standard methods of analysis in relation to the nature of the materials

Mechanical data (hardness and elastic modulus) from instrumented indentation testing are often extracted assuming linear elasticity in the initial portion of the unloading. The method is nowadays widely accepted as a convenient tool to interpret depth-sensing data, however it is a matter of controversy when applied to polymer materials due to their time-dependent behavior. More recently, Loubet and co-workers applied continuous stiffness measurements (CSM), consisting of superimposing a small oscillation to the quasi-static component of loading, to the study of the mechanical properties of polymers and proposed a new model to account for the apparent increase in the contact area detected at the first stages of contact. The present work offers a comparative study between the Loubet’s model using CSM and the procedure yielding a single reading from the onset of unloading. A wide range of thermoplastic polymer materials including glassy and semicrystalline polymers have been investigated. The most important equations employed for each method are summarized and the advantages and disadvantages of employing one procedure or the other are discussed. The differences found between the results obtained from both approaches are discussed in relation to the nature of the polymer material. A comparison between mechanical data extracted from indentation measurements and from classical dynamic mechanical analysis is offered.

Surface Engineering of the Hydrogenated DLC (a-C:H) Coatings with Optimized Mechanical Performance

The aim of this contribution is to present the properties of the hydrogenated DLC (a-C:H) films and to study their growth carried out in a special deposition technique based on Gaseous Thermionic Vacuum Arc (G-TVA) method. The mechanical properties were investigated on cross-sectional samples using the Fischerscope HM 2000 depth sensing indentation (DSI) tester.

Effect of Beta Irradiation on Microhardness of Polyamide 6

The polymer additional cross-linking influences the surface nano and micro layers in the way comparable to metals during the thermal and chemical-thermal treatments (e.g. surface hardening, cementation). Our research confirms the comparable properties of surface irradiated polyamide 6 (PA6) with high performance polymers. The surface layer of polymer material such as polyamide 6 is modified by β – radiation. Material properties of the surface layer created are measured by microhardness test using the DSI method (Depth Sensing Indentation). The influence of irradiation dose on mechanical properties (materials parameter) of PA6 is a subject of this research.