Indenter Penetration Depth Research Articles

Interaction of Mechanical Characteristics in Workpiece Subsurface Layers with Drilling Process Energy Characteristics

The performance properties of various types of parts are predominantly determined by the subsurface layer forming methods of these parts. In this regard, cutting processes, which are the final stage in the manufacturing process of these parts and, of course, their subsurface layers, play a critical role in the formation of the performance properties of these parts. Such cutting processes undoubtedly include the drilling process, the effect of which on the mechanical characteristics of the drill holes subsurface layers is evaluated in this study. This effect was evaluated by analyzing the coincidence of the energy characteristics of the short hole drilling process with the mechanical characteristics of the drilled holes’ subsurface layers. The energy characteristics of the short-hole drilling process were the total drilling power and the cutting work in the tertiary cutting zone, which is predominantly responsible for the generation of mechanical characteristics in the subsurface layers. As mechanical characteristics of the drill holes’ subsurface layers were used, the microhardness of machined surfaces and total indenter penetration work determined by the instrumented nanoindentation method, as well as maximal indenter penetration depth, were determined by the sclerometry method. Through an analysis of the coincidence between the energy characteristics of the drilling process and the mechanical characteristics of the subsurface layers, patterns of the effect of drilling process modes, drill feed, and cutting speed, which essentially determine these energy characteristics, on the studied mechanical characteristics have been established. At the same time, the increase in the energy characteristics of the short-hole drilling process leads to a decrease in the total indenter penetration work and the maximum indenter penetration depth simultaneously with an increase in the microhardness of the drilled holes’ subsurface layers.

Effect of plasma-electrolytic oxidation on mechanical properties of titanium coatings

The process of plasma electrolytic oxidation (PEO) allows to obtain multifunctional coatings with unique properties, including wear-resistant, corrosion-resistant, heat-resistant, electrical insulating and decorative. Therefore, the field of application of these coatings is quite wide: medicine, aircraft construction, shipbuilding, instrumentation, automotive and other industries. The technology is based on the phenomenon of micro-arc discharges promoting the formation of oxide layers on metal surfaces. In this review the technologies of obtaining coatings by plasma electrolytic oxidation on titanium are considered. The experiment on PEO of VT1-0 titanium substrate under anodic treatment with the addition of TiO2 nanoparticles to the electrolyte was carried out. Dense, uniform oxide coatings that do not require additional surface grinding were obtained. The coating thickness values were 18.5-62.4 μm. The influence of PEO on the microhardness of calcium-phosphate coatings formed as a result of this treatment was studied. With a satisfactory thickness of the formed layer (62.4 μm), the surface microhardness value (4.04 GPa) was found to be the highest among all the treatment modes compared, simultaneously with a high elastic modulus value (348 GPa) and a small value of the indenter penetration depth on the coating (968.99 nm). These coatings were formed in an electrolyte containing calcium phosphate with the addition of 0.75g of titanium oxide nanoparticles. The increase of microhardness in comparison with the sample without coating is in 2,5 times. As a result of the carried out researches optimum modes and parameters of calcium-phosphate coatings receiving have been established and defined. It is shown that by changing the composition of the electrolyte of the micro-arc treatment process it is possible to influence significantly the structure, thickness and surface properties of the obtained coatings.

Mechanical Characteristics Generation in the Workpiece Subsurface Layers through Cutting

The cutting process generates specific mechanical characteristics in the subsurface layers of the shaped parts. These characteristics have a decisive influence on the working properties and product durability of these parts. The orthogonal cutting process of structural heat-treated steel’s effect on the mechanical properties of the machined subsurface layers was evaluated by instrumented the nanoindentation method and sclerometry (scratch) method. As a result of this study, the relationship between the specific work in the tertiary cutting zone and the total deformation work during indenter penetration during the instrumented nanoindentation was established. The dependence of the indenter penetration depth during sclerometry of the machined subsurface layers of the workpiece was also studied. The orthogonal cutting process was carried out at different cutting speeds and tool rake angles. The cutting speed increase and the increase in the tool rake angle cause an increase in the indenter penetration work during the instrumented nanoindentation and an increase in the maximum indenter penetration depth during sclerometry. Simultaneously, the measured microhardness of the machined surfaces decreases with both an increase in cutting speed and an increase in the tool rake angle.

Identification of the elastic-plastic properties of CrN coating on elastic-plastic substrate by nanoindentation using finite element method-reverse algorithm

This paper proposes an identification methodology based on nanoindentation analysis of coating/substrate system to extract the elastic-plastic properties of coating materials on elastic-plastic substrate when the indenter penetration depth is greater than the film thickness. In order to accurately predict the elastic-plastic properties of the coating materials, a trust-region reflective optimization algorithm is integrated with the finite element analysis, in cooperation with the Jönsson and Hogmark model. The proposed reverse analysis algorithm modifies a predicted load-displacement (P-h) curve by changing the elastic-plastic properties of the coating and the substrate until it fits the experimental nanoindentation (P-h) curve. Numerical and instrumental indentations tests were carried out on a CrN film/Martensitic stainless steel substrate system to verify the proposed reverse method, by which Young's modulus (E), yield stress (σy), and work hardening exponent of the film were obtained. A sensitivity analysis is conducted to study the effect of the elastic-plastic properties of the CrN film/substrate on the (P-h) curve. The results showed a high impact to the loading and unloading part of the (P-h) curve due to variations in (E) and (σy) of the steel substrate compared to those of the CrN coating.

Fracture behaviour of microwave-heated granite under indentation: Experimental and numerical investigation

Microwave-assisted rock breakage is a promising solution for drilling and crushing hard-rock formations. The fundamental mechanical and thermophysical properties of microwave-treated granite were obtained, and the factors affecting the fracture behaviour under indentation were investigated using experimental and numerical methods. The results show that the uniaxial compressive strength, tensile strength, brittleness index, thermal conductivity, and thermal diffusivity of microwave-heated granite are negatively correlated with temperature, whereas the specific heat capacity of treated granite is positively correlated with temperature. The fracture process of microwave-heated granite under indentation can be divided into three stages: elastic deformation, fluctuating penetration, and post-peak. The indentation damage zone near the indenter consists mainly of tensile cracks. Meanwhile, regression analysis shows that the peak indentation force, penetration depth, and consumed energy of the microwave-heated sample are linearly correlated with the brittleness index. In addition, microwave treatment can weaken the inhibitory effect of a high confining stress on the damage zone and is conducive to reducing the indentation force and penetration depth of rock fragmentation. The specific energy is more sensitive to temperature under high confining stress conditions, and the relationship between the specific energy, temperature, and confining stress can be described by a 2D poly function.

Damage Accumulation Phenomena in Multilayer (TiAlCrSiY)N/(TiAlCr)N, Monolayer (TiAlCrSiY)N Coatings and Silicon upon Deformation by Cyclic Nanoindentation.

The micromechanism of the low-cycle fatigue of mono- and multilayer PVD coatings on cutting tools was investigated. Multilayer nanolaminate (TiAlCrSiY)N/(TiAlCr)N and monolayer (TiAlCrSiY)N PVD coatings were deposited on the cemented carbide ball nose end mills. Low-cycle fatigue resistance was studied using the cyclic nanoindentation technique. The obtained results were compared with the behaviour of the polycrystalline silicon reference sample. The fractal analysis of time-resolved curves for indenter penetration depth demonstrated regularities of damage accumulation in the coatings at the early stage of wear. The difference in low-cycle fatigue of the brittle silicon and nitride wear-resistant coatings is shown. It is demonstrated that when distinguished from the single layer (TiAlCrSiY)N coating, the nucleation and growth of microcracks in the multilayer (TiAlCrSiY)N/(TiAlCr)N coating is accompanied by acts of microplastic deformation providing a higher fracture toughness of the multilayer nanolaminate (TiAlCrSiY)N/(TiAlCr)N.

Modification of the Leeb Impact Device for Measuring Hardness by the Dynamic Instrumented Indentation Method

The article is devoted to modification of the impact devices of Leeb hardness testers for the implementation of the dynamic instrumented indentation method. The results obtained made it possible to construct a load–displacement curve using primary EMF signals and made it possible to determine the values of the dissipated and elastic impact body energy, the maximal load of indentation, the maximal and residual penetration depth and the geometric parameters of the indentation region, namely the contact area of the indenter with the surface and the volume of the displaced material. The listed parameters of the indentation process allow us to measure the contact and volume hardness, the elastic modulus and the yield strength of test objects with portable hardness testers.

FEM Simulation of Sclerometric Test of Nickel Aluminide Layered Coatings

3D simulation by the finite element method (FEM) using MSC.Marc of sclerometric test with a conical indenter of a nickel aluminide intermetallic coating has been determined. The effect of the coating thickness and composition on the strain distribution has been determined. It is shown that an increase in the thickness of the coating makes it possible to reduce the magnitude of the maximum plastic strain. NiAl and Ni3Al coatings reduce maximum value of plastic strain and the penetration depth of indenter by 40% compared to a coating made of Ni2Al3.

Room temperature nanoindentation creep behavior of detonation sprayed Fe-based amorphous coating

The Fe-based amorphous amorphous coating with a thickness of 150 μm was prepared by detonation spraying. Under a constant strain rate (0.01 s−1 and 0.50 s−1) and a holding time of 50 s, the Fe-based amorphous coatings were subjected to room temperature nanoindentation creep tests with the penetration depth varying from 50 nm to 500 nm, then the depth-dependent creep deformation mechanism of Fe-based amorphous coating during nanoindentation tests were investigated in detail. The results show that the creep responses of coating obviously depend on the indentation penetration depth (hp) and the indentation load rate, i.e., the creep displacement of coating increases with the increase of hp and loading strain rate. This is mainly due to the rapid increase in the shear transition zone volume of the coating as the hp increases, making it easier for the shear band to be excited to nucleate, and results in an obvious creep deformation. Moreover, at high strain rates, the initiation rate of the free volume in the amorphous coating far exceeds its annihilation rate, resulting in a large amount of excess free volume in the amorphous coating, which makes it easier to excite multiple shear bands in the amorphous coating and cause creep plastic deformation.

Mechanical properties of α-quartz using nanoindentation tests and molecular dynamics simulations

Understanding the mechanical properties of α-quartz is of vital importance to rock engineering because α-quartz is the main component of igneous, metamorphic and sedimentary rocks. Molecular dynamics simulations (MDs) of nanoindentation tests on α-quartz were performed to investigate the effects of indenter tip radius and penetration depth on the mechanical properties of α-quartz. Indentation load-penetration depth (P-h) curves were plotted, from which Reduced Young’s modulus ( E r ) , hardness ( H ) were obtained and these mechanical parameters were then compared with the laboratory nanoindentation results. The mechanical results obtained from MDs are in good agreement with the experimental values. It can be found that E r and H increase with indentation depth at shallow contact depth while they decrease with indenter tip size. To the authors’ knowledge, this is the first MDs of nanoindentation test of hard rock-forming minerals reported and we believe that this study can shed light on the precise measurement of the mechanical properties of rock minerals at micro- and nano-scales.

Low temperature micromechanical properties of nanocrystalline CoCrFeNiMn high entropy alloy

In the temperature range 77–290 K, the microhardness of high entropy alloy CoCrFeNiMn (Сantor alloy) samples in three structural states was measured: (i) initial coarse-grained samples (ii) nanocrystalline samples obtained by high pressure torsion (HPT) at room temperature and (iii) nanocrystalline samples processed by HPT at liquid nitrogen temperature. With a decrease in temperature from 290 K to 77 K, the microhardness of all types of samples monotonically increased by about 40–60% which indicates the thermally activated nature of plastic deformation under the indenter. The highest microhardness was observed in nanocrystalline samples obtained by the torsion at room temperature. It is shown that the ratio of Vickers microhardness to the conventional yield strength remains constant in the range of 77–290 K, and that the ratio value depends on the microstructure of samples. In the coarse-grained Cantor alloy samples the normal indentation size effect was observed: the microhardness increased with a decrease of the indenter penetration depth; the obtained dependence is discussed in the framework of geometrically necessary dislocations model. In the HPT-nanocrystallized samples in the low load range, an essential microhardness drop with the load decreasing was observed, being a result of mechanical polishing of the sample surface, which destroys the microstructure created under the torsion and weakens the surface layer.

Novel approach to characterize the deformation under Berkovich and spherical indentations: Study on magnesium single crystals

In this work, we have developed a mathematical framework to investigate the deformation response under Berkovich and spherical indenters. Nanoindentation experiments are carried out on two single-crystal magnesium (Mg) samples oriented for basal slip and tensile twinning. The indentation load vs penetration depth curves are then analyzed to explain the pop-in events with the help of Schmid factor analysis and to identify the favorable deformation modes directly beneath and around the indentation. These results explain why there is only a small difference in the values of hardness between the two orientations despite having a significant difference in their crystallographic orientations. In addition to this, the role of indenter tip radius on the formation of extension twins when indented along the crystallographic $c$ axis is analyzed with the help of a simple analytical model.

Effect of Strain Rate on the Deformation Characteristic of AlN Ceramics under Scratching.

To clarify the influence mechanism of strain rate effect on deformation characteristics of aluminum nitride (AlN) ceramics, some varied-velocity nanoscratching tests were carried out using a Berkovich indenter in this paper. The deformation characteristics of the scratched grooves were observed using the scanning electron microscope. The experimental results showed higher scratch speed would lead to shallower penetration depth, fewer cracks, and indenter fewer slipping, which was more conducive to the plastic deformation of AlN ceramics. Considering the strain rate effect and the elastic recovery of material, a model for predicting the Berkovich indenter penetration depth under edge-forward mode was established. The prediction results were consistent with the experimental data, and the error was less than 5%, indicating that the model is effective. Based on the Boussinesq field, the Cerruti field, and the Sliding bubble field, a strain rate dependent scratch stress field model was established. The stress field revealed higher scratch speed may significantly reduce the maximum principal stress in the stress field under the indenter, which is the fundamental reason for reducing the crack damage and promoting the plastic deformation. The above study can provide theoretical guidance for reducing the processing damage of AlN ceramics.

Atomistic Investigation of Material Deformation Behavior of Polystyrene in Nanoimprint Lithography

This research investigates deformation behavior of polystyrene (PS) as a thermoplastic resist material for the thermal nanoimprint lithography (T-NIL) process. Molecular dynamics modeling was conducted on a PS substrate with dimensions 58 × 65 × 61 Å that was imprinted with a rigid, spherical indenter. The effect of indenter size, force, and imprinting duration were evaluated in terms of indentation depth, penetration depth, recovery depth, and recovery percentage of the polymer. The results show that the largest indenter, regardless of force, has the most significant impact on deformation behavior. The 40 Å indenter with a 1 µN of force caused the surface molecules to descend to the lowest point compared to the other indenters. An increase in indenter size resulted in higher penetration depth, recovery depth, and recovery percentage. Higher durations of imprint cycle (400 fs) resulted in plastic deformation of the PS material with minimal recovery (4 Å). The results of this research lay the foundation for explaining the effect of several T-NIL process parameters on virgin PS thermoplastic resist material.

Extended Applications of the Depth-Sensing Indentation Method.

The depth-sensing indentation method has been applied for almost 30 years. In this review, a survey of several extended applications developed during the last three decades is provided. In depth-sensing indentation measurements, the load and penetration depth data are detected as a function of time, in most cases at controlled loading rates. Therefore, beside the determination of hardness and Young’s modulus, different deformation mechanisms and many other dynamic characteristics and phenomena, such as the dynamic elastic modulus, load-induced phase transition, strain rate sensitivity, etc. can be studied. These extended applications of depth-sensing indentation measurements are briefly described and reviewed.

Determination of the optimal strength of contact interaction of the tool and the part during finishing-hardening treatment by diamond smoothing

The main factors of the process of diamond smoothing are considered in the work: the force of the contact interaction of the tool and the part in the deformation zone and the friction on the contact surface of the part and the smoother. The technique of analytical determination of the optimal smoothing force for the finishing-hardening treatment mode is presented. The calculated values were obtained for some characteristic grades of materials of small and medium hardness (≤ 210 HB, indenter radius 3.4 mm) and a number of hardened steels of high hardness (indenter radius 2.0 mm). The force values are also determined using expressions for the deformation component of the friction coefficient. A comparative analysis of the results indicates that the calculation options are adequate for practical purposes. On specific examples of processed materials, graphical dependencies are shown, which reflect the relationship between the coefficient of friction, including its deformation component, and the smoothing force. With an increase in the leveling force, the friction coefficient increases, this is explained by an increase in the depth of penetration of the diamond tip and, consequently, an increase in the deformation component. The depth of penetration of the indenter into the surface to be treated, and therefore the coefficient of friction during ironing, depends on the hardness of the material being processed. With increasing hardness, the penetration depth decreases, which leads to a decrease in the deformation component and in general the coefficient of friction. The friction coefficient is also affected by the radius of the working part of the tool, since the indenter penetration depth also depends on its value. The research results can be used in the development of technology for finishing and hardening diamond smoothing, the development of the process and its introduction into production.

Molecular dynamics investigation of material deformation behavior of PMMA in nanoimprint lithography

Computational analysis of polymeric materials plays a key role in defining their tribological characteristics. This research investigates the deformation behavior of poly(methylmethacrylate) (PMMA) as a thermoplastic resist material for the thermal nanoimprint lithography (T-NIL) process. Molecular dynamics modeling was conducted on a PMMA substrate imprinted with a rigid spherical indenter. The effect of indenter size, force, and imprinting duration on the indentation depth, penetration depth, recovery depth, and recovery percentage of the polymer was evaluated. The results showed that the largest indenter, regardless of force, had the most significant impact on deformation behavior. The 40-Å indenter with a 1 μN of force caused the surface molecules to descend to the lowest point compared to the other indenters. An increase in the indenter size resulted in a higher penetration depth, recovery depth, and recovery percentage. Higher durations of imprint cycle (400 fs) resulted in plastic deformation of the PMMA material with minimal recovery (30 Å). The results of this research lay foundation for explaining the effect of several T-NIL process parameters on the virgin PMMA thermoplastic resist material.

Polyamide Surface Layer Nano-Indentation and Thermal Properties Modified by Irradiation.

This study describes the effect of electron radiation on the nano-mechanical properties of surface layers of selected polyamide (PA) types. Electron radiation initiates the cross-linking of macromolecules in the polyamide structure, leading to the creation of a 3D network which fundamentally changes the properties of the tested polymers. Selected types of polyamide (PA 6, PA 66 and PA 9T) were exposed to various intensities of electron radiation (33 kGy, 66 kGy, 99 kGy, 132 kGy, 165 kGy and 198 kGy). The cross-linked polyamides’ surface properties were measured by means of the modern nano-indentation technique (Depth Sensing Indentation; DSI), which operates on the principle of the immediate detection of indenter penetration depth in dependence on the applied load. The evaluation was preformed using the Oliver–Pharr method. The effect of electron radiation on the tested polyamides manifested itself in the creation of a 3D network, which led to an increase of surface layer properties, such as indentation hardness, elastic modulus, creep and temperature resistance, by up to 93%. The increase of temperature and mechanical properties substantially broadens the field of application of these materials in technical practice, especially when higher temperature resistance is required. The positive changes to the nano-mechanical properties as well as mechanical and temperature capabilities instigated by the cross-linking process were confirmed by the gel volume test. These measurements lay the foundation for a detailed study of this topic, as well as for a more effective means of modifying chosen properties of technical polyamide products by radiation.

BENEFITS OF USE OF ACOUSTIC EMISSION IN SCRATCH TESTING

Scratch test is regularly used for assessment of cohesive and adhesive strength of thin films and coatings. By default, its evaluation is based on analysis of depth-load-time record and microscopic observation of residual scratch groove. The visual analysis of the residual groove provides the most detailed description of the final damage of the surface (crack patterns, extent of plastic deformation, delamination, etc.), but it may be a time demanding approach. Although the continuous recording of indenter penetration depth and applied load offers instantaneous information about the performance of the tested material, it may not provide sufficient description of the sample’s deformation behaviour. Therefore, other complementary techniques for description of the deformation response to scratch loading are desirable. Continuous recording of acoustic emissions (AE) generated during the test could be a possible solution. It is especially the ability of AE method to detect the very first and even subsurface failures of the material that is of the most importance and otherwise inaccessible by standardly used techniques. What is more, it is a non-destructive and real-time method. In principle, AE method can be beneficially employed for a wide range of materials explored via scratch test. The strength of the AE analysis of the nano/micro scratch test will be demonstrated on various types of materials including optical thin films, durable metal and hard ceramic films as well as bulk laser cladding. Selected phenomena and features of the use of AE during scratch testing will be presented, including effect of scratch load on character of AE records (burst vs. continuous) for TiO2 on glass, subsurface damage of SiC films on silicon and selective failure of hard carbide phase embedded in a metal matrix in case of laser re-melted layers.

Temperature dependence of indentation behavior of Ti-6Al-4V alloy for bio medical applications

Numerical analysis of spherical indentation was carried out to study temperature dependence (300-673K) of elasto-plastic deformation behavior of Ti-6Al-4V alloy. Flow stress and strain hardening exponent ‘n’ were determined from load versus indenter penetration depth profiles generated through FE model using Dao’s reverse analysis approach. The upward flow around the residual impression as a function of average strain, which describes the strain hardening behaviour of the alloys was also investigated. The simulated values of CF have been used to predict high strain-rate plastic flow behavior considering indentation data. It was observed that there is a good correlation between data from simulation and experimental results in the literature. The FE model developed in the current investigation can be used for simulating the flow behavior of Ti-6Al-4V alloy. The temperature dependent CF value in the fully plastic regime from the current study is approximately 2.69 against experimentally evaluated value of 2.95. Meyer’s hardness is generally high due to the presence of cold layer resulting from grinding and polishing of the test specimen. Absence of such effects in simulation of spherical indentation resulted in reduced value of CF.