Indentation Method Research Articles

The effect of the amount and size of alumina sintering aid particles on some mechanical properties and microstructure of silicon carbide bulky pieces via spark plasma sintering

Abstract In this paper, for sintering silicon carbide nanopowders via the spark plasma sintering method, nano-and micro-sized alumina sintering aids were used separately at 3 vol.%, 5 vol.%, and 7 vol.%. The sintering process was undertaken at 1900 °C for 10 min. To investigate some mechanical and physical properties of the resulting samples, density was obtained via the Archimedean method, and hardness was taken by the Vickers indenter method. The microstructure of the samples was examined through scanning electron microscopy. The results indicated that in the samples containing nano-alumina, the largest percentage of density and hardness was related to the sample containing 5 vol.% nano-alumina as a sintering aid and were obtained as 99% of theoretical density and 31.3 GPa, respectively. For the samples containing micro-alumina, the highest percentage of density and hardness was related to the sample containing 7 vol.% micro-alumina and obtained 93% of theoretical density and 20.1 GPa, respectively. By investigating the fractured surfaces of the samples and via the linear intercept method, the largest mean grain size was associated with the densest sample at 3.7 µm.

Spatially resolved Raman piezospectroscopy for nondestructive evaluation of residual stress in β-Ga2O3 films

In this paper, the piezospectroscopic effect for β-Ga2O3, i.e. the spectral band shift in response to strain/stress, has been calibrated by the indentation method using spatially resolved Raman spectroscopy for quantitative stress evaluation of Ga2O3 devices, taking advantage of the crack-tip tensile stress field and the spatial probe deconvolution. A series of Vickers indentation prints were introduced on (010) and () Ga2O3 single crystals, and the relationships between observed band shifts and residual stresses were clarified to determine the phonon deformation potentials of the Raman bands. Accordingly, a quantitative analysis of the residual stress field in a Ga2O3 thin film grown on (0001) sapphire by plasma-assisted pulsed laser deposition, which revealed the presence of a gradient of incompletely released stress in the depth direction of the film, is shown as an example.

Investigation the effect of Co3O4 doping on structural and mechanical properties of ZnO pallets synthesized by powder metallurgy method and their biological evaluation

ZnO is an important semiconductor due to its unique structural, mechanical and optical properties. In this study pure ZnO pallets and Co3O4 doped ZnO pallets with varying molar concentration of dopant i.e 2% 4% 6% 8% and 10% were prepared by using hydraulic press. X-ray diffraction (XRD), FTIR and Vickers indentation method is used for pallets characterization. The XRD analysis revealed that the pure ZnO and doped ZnO pallet samples have hexagonal wurtzite structure. Vickers Hardness test showed that pure ZnO pallet has maximum hardness as compared to the Co3O4 doped ZnO pallets. FTIR analysis used to examine the bonding properties of synthesized Co doped ZnO. Doped materials with varying concentration were applied against different gram positive and gram negative bacterial strains. A considerable increase in antibacterial activity was observed by increasing the concentration of Co3O4 dopant.

Influence of substrate bias voltage on microstructure and mechanical characteristics of TiAlSiN coating deposited by High Power Impulse Magnetron Sputtering (HiPIMS)

Substrate bias voltage has a presumably predominant and significant influence on the microstructural morphology and mechanical properties of HiPIMS deposited coatings. In the present investigation, it has been investigated in depth for a quaternary coating, TiAlSiN coating, which was deposited on the cemented carbide (WC-10 wt% Co) substrates. In this HiPIMS process, a pair of TiAl60 and a pair of TiSi34 targets were used. Four different substrate biases were set, i.e., −60, −90, −120, and −150 V to explore the difference in the coating characteristics. In every case, the substrate bias was also applied in pulsed mode but with an offset of 40 μs to the cathode pulse. Both cathode current and bias current were observed to increase from 87 to 98 A and 19 to 23 A, respectively, with increase of substrate bias voltage. As the bias voltage increased, the surface morphology became finer, and the cross-section morphology turned to be highly denser. The minimum and maximum grain sizes were estimated to be 7.23 nm and 9.90 nm at a substrate bias of −60 V and −150 V, respectively. Variation of Ti content (at.%) was noticed in the range of 28.35 to 30.71 with the increase of bias voltage. The maximum hardness of the coating was recorded to be 42.95 GPa at the bias voltage of −150 V. The adhesion level has been classified under HF1 in all deposition cases, as investigated by Rockwell indentation method, whereas the scratch test results suggest that a load range between 154 and 161 N is required for the complete delamination of the coating. Spallation and edge-chipping were the primary failure mechanisms during the scratching of the TiAlSiN coating.

Improving the precision of Vickers indentation measurements in soda-lime glass with increased dwell time

Vickers indentation methods are popular techniques for the determination of hardness, indentation fracture toughness, and crack initiation resistance in silicate glasses, predominantly due to the simplicity and efficiency of the technique. Despite the method's popularity, it is challenging to obtain consistent and repeatable results from these measurements. Here, we perform a systematic investigation of the effects of applied load, dwell time, and post-indentation observation time on the precision of hardness and indentation fracture toughness values for soda-lime silicate glass measured via Vickers microindentation. The data suggests that low applied loads (≤ 1.06 N) in combination with short dwell times (≤ 15 s) lead to low precision in the measurements and that a longer dwell time of 30 s leads to higher precision and load-independent indentation fracture toughness. The increased repeatability of these measurements at higher dwell time could make Vickers microindentation a reliable technique for silicate glass mechanical property measurement.

Analisis Kerusakan Pada Permukaan Roda Kereta Rel Listrik

The wheels of electric rail cars are an essential component of rail transportation when they are in use. At the time of inspection, the technician discovered damage to the wheel's surface. This is due to the hardening of the brake block, which damages the wheel's surface. This research was conducted with the purpose of analyzing the causes of damage to the tread surface of the wheels and identifying a suitable replacement for the original brake block, which is no longer manufactured and has been replaced by imitation block brakes. so that further action can be taken to prevent similar occurrences in the future. Using the Vickers hardness test indentation method, the purpose of this study is to examine various heat treatments for determining a material's hardness level. The test results indicate that the VHN value increases with increasing heating temperature. The original specimen produced 99.5 VHN in the first test without heat treatment, while the X block brake produced 26.9 VHN and the Y brake produced 136.0 VHN. The second test with 200°C heat treatment on the original specimen yielded 96.8 VHN, 73.1 VHN from the X block, and 152.9 VHN from the Y block. In addition, the third test with 400°C heat treatment on the original specimen produced 92.4 VHN, 47.8 VHN for the X block brake, and 268.3 VHN for the Y block brake. The Vickers Hardness Test (VHN) hardness value is affected by heat treatment; the higher the heating value, the higher the hardness value of the remolok specimen.

Mechanical Properties of Structural Components in Hastelloy X Joints Brazed with Ni-Pd-Cr-B-Si Alloy.

The brazing of structural high-temperature-resistant nickel alloys is a predominant method in manufacturing jet engines in the aircraft industry. Ni-Cr-base brazing filler metals (BFMs) containing B and Si as the melting point depressants are used for this purpose. The presence of the latter can lead to the formation of brittle constituents in the joints, decreasing their strength, toughness and creep resistance. The structures of Hastelloy X nickel superalloy joints brazed with Palnicro 36M BFM are presented in this paper along with the mechanical properties of their particular phases as a function of brazing time. Indentation hardness, Martens hardness, reduced modulus and creep coefficient were measured using the instrumented indentation method. The elastic part of the indentation work was also calculated. Pd forms an unlimited solution with Ni, but its high content in BFM does not fundamentally change the general joint structure known from other Ni-superalloy-Ni-BFM systems. However, new Pd-containing phases are emerging. The hardest components were Ni-B and Cr-B boride phases and Pd-Ni-Si phase in MZ and the boundary of DAZ and BM. MZ reduces the plasticity of a joint to the highest extent. The hardness of particular parts in the joints and the elastic portion of the indentation work decreased with the increase in brazing time, while the reduced modulus of the indentation contact and indentation creep increased. The results of indentation creep measurements indicate that all structural components of the joints were less susceptible to creep than the parent material at room temperature.

3D AFM Nanomechanical Characterization of Biological Materials.

Atomic Force Microscopy (AFM) is a powerful tool enabling the mechanical characterization of biological materials at the nanoscale. Since biological materials are highly heterogeneous, their mechanical characterization is still considered to be a challenging procedure. In this paper, a new approach that leads to a 3-dimensional (3D) nanomechanical characterization is presented based on the average Young's modulus and the AFM indentation method. The proposed method can contribute to the clarification of the variability of the mechanical properties of biological samples in the 3-dimensional space (variability at the x-y plane and depth-dependent behavior). The method was applied to agarose gels, fibroblasts, and breast cancer cells. Moreover, new mathematical methods towards a quantitative mechanical characterization are also proposed. The presented approach is a step forward to a more accurate and complete characterization of biological materials and could contribute to an accurate user-independent diagnosis of various diseases such as cancer in the future.

Characterization of mechanical properties of in-service nickel-based alloy by continuous indentation

Accurate acquisition local material mechanical properties of key structures material plays a key role in equipment safety evaluation and life prediction. In this study, the method for the mechanical properties of nickel-based alloy 600 before and after creep based on continuous indentation test combined with numerical simulation was established, and the high stress creep constitutive equation of nickel-based alloy 600 in autoclave environment was obtained, then the influencing factors of mechanical properties are analyzed. Results show that with the increase of the creep time of alloy 600, the microstructure and macroscopic deformation become more obvious. Simultaneously, the strain strengthening caused by creep increases gradually, and the mechanical properties of nickel-base alloy 600 increase. The indentation test model verified by numerical simulation can carry out the continuous indentation test and accurately obtain the indentation load-depth curve of alloy 600 before and after creep, and the characteristic stress–strain points obtained agreement with the stress–strain curve obtained by uniaxial tensile test. The established indentation test system platform can obtain the mechanical property parameters of nickel-based alloy by using indentation method. Compared with the traditional uniaxial tensile test, the relative strength error is less than 5% and nondestructive, which provides a theoretical basis for the safety evaluation and residual life analysis of in-service structural materials.

Effect of Equibiaxial Pre-Stress on Mechanical Properties Evaluated Using Depth-Sensing Indentation with a Point-Sharp Indenter.

This study examined the effect of an imposed equibiaxial pre-stress (EBPS) on the evaluation of mechanical properties, using the depth-sensing indentation method with a point-sharp indenter, through a numerical analysis of indentations simulated with the 3D finite element method. The predicted elastic modulus, E*, and yield stress, Y*, were used as elastic and plastic deformation resistances under the indentation, respectively. It was found that both increased nominally with the increase in compressive EBPS and decreased with the increase in tensile EBPS, even though the induced change in the piling-up or sinking-in around the indentations was not significant. The effect of EBPS on E* was described by the Hooke's law for an isotropic elastoplastic material, whereas that on Y* was accounted for by the change in the von Mises stress due to EBPS.

AN INDENTATION METHOD FOR ADHESIVE STRENGTH EVALUATION OF POLYMER COATINGS

An indentation method was developed for adhesive strength evaluation of a polymer coating using the example of an epoxy composition with titanium alkoxide deposited on the surface of low-carbon steel. The method is based on the numerical implementation of the fracture mechanics approach in experimental data processing. It was found that the penetration of a Rockwell indenter perpendicular to the coating surface causes annular delamination buckling of the coating around the indentation, which is due to adhesive bond breaking as a result of radial shear when the coating material is forced out from under the indenter. A controlled parameter in finite element modeling was the experimentally determined width of the coating delamination zone at a fixed indentation depth at which delamination occurred. The adhesive contact conditions were set using the bilinear law of the cohesive zone model, which describes the relationship between the adhesive shear stress and adhesive bond stretching during shear of interacting surfaces in the contact plane. The limiting specific surface energy of adhesive failure was used as a quantitative evaluation criterion for adhesive strength. The optimal value of the limiting specific surface energy of adhesive coating failure was determined for the cohesive zone model parameters that provide the best convergence of the numerical and experimental data.

Investigation of elastic properties of solid polymer materials by indentation method

The mechanical properties of solid (crystalline) polymer materials are proposed to be investigated simultaneously using two complementary methods based on controlled indentation of a spherical indenter. The first method consists in the direct analysis of the load curve without using the concept of contact stiffness; the second method is based on measurements of the size of prints depending on the magnitude of the static load. The study shows that the reinforcement of a solid polymer with carbon fibers can lead to a significant increase in its elastic-strength properties. Keywords: polymer composite materials, indentation, Hertz contact theory, spherical stamp, reduced modulus of elasticity, Brinell hardness, ultimate strength.

STRUCTURAL-PHASE STATE AND MECHANICAL PROPERTIES OF A TITANIUM MATRIX COMPOSITE BASED ON TI64 ALLOY AND TIB2 CERAMICS OBTAINED BY LASER CLADDING

The paper presents experimental studies on the synthesis of a titanium matrix composite based on Ti64 titanium alloy and TiB2 ceramic particles by laser surface cladding. The weight percentage of TiB2 ceramics in the composite was 5, 10, and 15%. The phase composition of the resulting materials was analyzed by standard X-ray diffraction and synchrotron X-ray diffraction. It was found that the structure of the titanium matrix composite with 5 wt % ceramics consists of TiB nanowhiskers, and that of samples with higher ceramics content exhibits TiB whiskers with a width of several micrometers. The addition of TiB2 ceramics leads to an increase in Young’s modulus and nano-/microhardness of composite samples compared to Ti64 alloy. The indentation method was used to study the formation of a phase that does not correspond to TiB2 ceramics and microscale TiB whiskers and has elastic properties exceeding the elastic properties of the original Ti64 matrix phase. Analytical predictions showed an increase in the effective elastic properties of the formed heterogeneous material with the predicted new phase. It was also found that a lower friction coefficient can be achieved by forming a structure with nanowhiskers, while higher Young’s modulus and microhardness can be obtained by forming a structure with microwhiskers.

APPLICABILITY ASSESSMENT OF THE VICKERS INDENTATION FOR DETERMINING THE FRACTURE TOUGHNESS OF YTTRIA-STABILIZED ZIRCONIA

Crack growth resistance of ZrO2-(3-8) mol% Y2O3 ceramics was investigated. Young's modulus by the ultrasonic flaw detection method were determined. Vickers hardness and parameters of cracks after Vickers indentation were obtained. Based on the Young's modulus values, Vickers hardness, and parameters of cracks, the fracture toughness of the investigated ceramics was calculated using 9 different equations of the Vickers indentation method. A comparative analysis of the calculated fracture toughness values with those obtained by the single-edge notch beam method was carried out. It was found that choosing the optimal equation for calculating fracture toughness by the Vickers indentation method is quite difficult and requires comparison with the results of standardized tests. It was shown that to determine crack resistance characteristics of the yttria-stabilized zirconia ceramics, the use of only the Vickers indentation method without comparison with other methods of fracture mechanics is incorrect.

A new method for measuring magnetorheological fluid redispersibility by testing yield stresses of sediments at different depths.

Magnetorheological fluid (MRF) is a widely used smart material that suffers from sedimentation. Since sedimentation is unavoidable, it is crucial to study and improve the redispersibility of MRFs. However, previous redispersibility testing methods have problems, such as complicated operation and low precision. Simultaneously, a simple and effective method is urgently needed for high-precision modeling of MRF sedimentation to test the rheological properties of settled MRFs at different depths. After systematically analyzing the redispersion problem, this paper proposes decoupling the energy required for redispersing settled MRFs into two parts, which are related to different factors. These two parts are the energy required to separate the agglomerated particles (related to the MRF formula) and that to redisperse the settled MRF uniformly vertically against gravity (related to the solid concentration and packing limit). The energy that separates the agglomerated particles is proportional to the shear stress of slowly shearing the corresponding agglomerated samples, i.e., the yield stress. Thus, this paper proposes a simple microdamage quasi-static indentation method to measure the yield stresses of settled MRFs at different depths to characterize the redispersibility of the corresponding MRFs. Herein, this method is applied to study the mechanisms of the influences of surfactants, thixotropic agents, and their networks on the redispersibility of MRFs. The results indicate that a well-dispersed plate-like thixotropic agent network can effectively improve redispersibility, while surfactants with poor compatibility degrade redispersibility. In summary, this redispersibility test method will greatly facilitate studies of MRFs, such as optimizing the formulas and establishing sedimentation models.

Влияние фрикционной обработки и жидкостной цементации на сопротивление общей коррозии хромоникелевых аустенитных сталей

Currently, to increase the hardness, strength and wear resistance of thermally non-hardenable austenitic chromium-nickel steels, such methods as frictional treatment with a sliding indenter and liquid carburizing have been used. However, along with an effective increase in mechanical characteristics, the application of these types of treatment may be accompanied by a decrease in the corrosion resistance of austenitic steels. Therefore, it is reasonable to study the influence of frictional treatment and liquid carburizing on the general corrosion resistance of Cr–Ni austenitic steels. In this work, the surface microhardness of the 12Cr18Ni10Ti and AISI 321 steels was determined using the recovered indentation method after electropolishing, mechanical grinding, frictional treatment, and liquid carburizing at a temperature of 780 °C. Using scanning electron microscopy and optical profilometry, the authors studied steel surfaces subjected to the specified types of treatment and determined their roughness. The corrosion resistance of steel was studied by testing for general corrosion using the gravimetric method. When testing for general corrosion, it was found that hardening (up to 710 HV 0.025) frictional treatment leads to an increase in the corrosion rate of the 12Cr18Ni10Ti austenitic steel compared to the electropolished state (from km=0.35 g/(m2·h) to km=0.53–0.54 g/(m2·h)). The corrosion rate of the ground steel is km=0.58 g/(m2∙h), while mechanical grinding does not provide a significant increase in the microhardness of the steel under study (from 220 to 240 HV 0.025). It is shown that the corrosion behavior of 12Cr18Ni10Ti steel subjected to various types of treatment is determined by the following factors: the presence/absence of strain-induced α'-martensite in the structure, the quality of the formed surface and, apparently, the dispersion of the formed structure. Liquid carburizing of the AISI 321 austenitic steel leads simultaneously to an increase in its microhardness to 890 HV 0.025 and a certain increase in corrosion resistance compared to fine mechanical grinding. This is related to the fact that carbon embedding atoms stabilize the electronic structure of iron (austenite and martensite), thereby increasing its corrosion resistance.

Solving the Bonding Problem of the Ni Thin Coating with the Ultrasonic Assisted Electrochemical Potential Activation Method.

Electroplating nanocrystallite Ni coating can improve the mechanical properties of the metal structure surface, which is widely used in fabricating metal MEMS devices. Because of the large internal compressive stress caused by the oxidation layer of the substrate surface, the Ni coating easily falls off from the substrate surface. To solve this bonding problem, the ultrasonic assisted electrochemical potential activation method was applied. The ultrasonic experiments have been carried out. The bonding strength was measured by the indentation method. The substrate surface oxygen element was tested by the X-ray photoelectron spectroscopy (XPS) method. The dislocation was observed by the TEM method. The compressive stress was tested by the XRD method. The coating surface roughness Ra was investigated by the contact profilometer method. The results indicated that the ultrasonic activation method can remove the oxygen content of the substrate surface and reduce the dislocation density of the electroplating Ni coating. Then, the compressive stress of the electroplated Ni coating has been reduced and the bonding strength has been improved. From the viewpoint of the compressive stress caused by the oxygen element of the substrate surface, mechanisms of the ultrasonic activation method to improve the bonding strength were researched originally. This work may contribute to enhancing the interfacial bonding strength of metal MEMS devices.

Indentation fracture toughness of boronized unalloyed and alloyed ductile iron

This study was carried out to investigate the fracture toughness of boride layers in ductile irons using a Vickers indentation method and to demonstrate the method's reliability. For this purpose, alloyed (Cu, Ni, and Mo) and unalloyed ductile cast irons were borided for 2, 4, 6, and 8 h at 900 and 950 °C temperatures. The morphology of the boride layer was studied using an optical microscope. The hardness profiles and thicknesses of the boride layers were measured. Boron compounds were discovered using the X-ray diffraction method. The fracture toughness of the boride layer was tested using the Vickers indentation method under a 300g load. In unalloyed cast iron, the surface hardnesses obtained by boriding were 5, 45-6, 69 times higher than that of the unboronized iron hardness. In general, alloyed iron produces thicker boride layers under the same boriding parameters. Depending on the boriding time, the fracture toughness increased at 900 °C and decreased at 950 °C in both types of cast iron.

Determining the elastic modulus of film/substrate materials from instrumented indentation testing based on machine learning

<p indent="0mm">Instrumented indentation testing has been widely used to determine the mechanical properties of materials. However, due to the substrate effect, the mechanical properties of each layer of film/substrate material becomes complicated to determine using this method. Through the finite element simulation, combined with a classic neural network method of multi-output multilayer perceptron (MLP), the relationship between the film/substrate material parameters (elastic modulus of film and substrate), normalized indentation depth (indentation depth/film thickness), and composite modulus is established. This established relationship is used to develop an indentation method to determine the elastic modulus of film/substrate. Prediction results through deep learning and the finite element simulation results are compared. The comparison results indicate that the predicted values of hard film/soft and soft film/hard substrate materials obtained from MLP are in good agreement with the simulation results. Indentation tests of Ni/304 and Cu/304 stainless steel were conducted to verify the trained neural network. The results indicate that elastic modulus of each layer predicted using the MLP is close to those obtained in the test. The results of this study can provide alternative research methods for evaluating the properties of film/substrate materials.

Method of the Mechanical Properties Evaluation of Polyethylene Gas Pipelines with Portable Hardness Testers

This article is devoted to the study of means and methods for non-destructive testing mechanical properties of polyethylene gas pipelines that have been in operation for 25–55 years. In order to assess mechanical properties, stress at yield was chosen as a key parameter. Stress at yield is determined from the results of tensile tests and is associated with the limiting circumferential (hoop) stress, determined from the results of tests for short-term pressure. Tensile tests require sample cutting and the shutdown of pipelines’ service. To solve this problem of nondestructive testing of pipelines, tests were carried out using the methods of Shore, Leeb and dynamic instrumental indentation. According to the test results, it was revealed that the correlation coefficient between the values of stress at yield and hardness, obtained by the method of dynamic instrumental indentation, is 0.98 which confirms the possibility of the evaluation of the mechanical properties of pipelines by the method of dynamic instrumental indentation.