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1

Plastic deformation mechanisms in BCC single crystals and equiatomic alloys: Insights from nanoindentation

Dominguez-Gutierrez Francisco Javier, Papanikolaou Stefanos, Bonfanti Silvia, Alava Mikko

Computer Methods in Materials Science

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2024

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Vol. 24, No. 1

37--49

EN

Deformation plasticity mechanisms in alloys and compounds may reveal the material’s capacity towards optimal mechanical properties. We conducted a series of molecular dynamics (MD) simulations to investigate plasticity mechanisms due to nanoindentation in pure tungsten, molybdenum, and vanadium body-centered cubic single crystals, as well as the body-centered cubic, equiatomic, random solid solutions (RSS) of tungsten–molybdenum and tungsten–vanadium alloys. Our analysis focuses on a thorough, side-by-side comparison of dynamic deformation processes, defect nucleation, and evolution, along with corresponding stress–strain curves. We also checked the surface morphology of indented samples through atomic shear strain mapping. As expected, the presence of Mo and V atoms in W matrices introduces lattice strain and distortion, increasing material resistance to deformation and slowing down dislocation mobility of dislocation loops with a Burgers vector of 1/2 〈111〉. Our side-by-side comparison displays a remarkable suppression of the plastic zone size in equiatomic W–V RSS, but not in equiatomic W–Mo RSS alloys, displaying a clear prediction for optimal hardening response of equiatomic W–V RSS alloys. If the small-depth nanoindentation plastic response is indicative of overall mechanical performance, it is possible to conceive a novel MD-based pathway towards material design for mechanical applications in complex, multi-component alloys.

2

Role of crystallographic orientation in material behaviour under nanoindentation: Molecular Dynamics study

Kurgan Aneta, Madej Lukasz

Materials Science Poland

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2023

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Vol. 41, No. 3

18--26

EN

The mechanical properties of materials can be analysed under deformation conditions by various laboratory tests. However, such experimental investigations become extremely complicated and often even impossible at the lower length scales where the arrangement of the atomic planes is considered. In this case, computational materials science is a robust alternative to extend the capabilities of laboratory tests. Therefore, the molecular dynamics technique was selected in the current work to evaluate the role of the local grain crystallographic orientation during nanoindentation testing. A pure aluminium sample was selected as a case study. For the sake of clarity, two distinctively different crystallographic orientations cube {100}<001> and hard {110}<011> were investigated in a set of arrangements: monocrystalline, bicrystalline, and polycrystalline. The influence of the substrate and the neighbouring grains on the material response to local deformation was evaluated. The research used two types of indenters: spherical and sharp-tipped. Results obtained were analysed with respect to the arrangement of atoms and load-displacement curves. This research proved that the role of crystallographic orientation in material behaviour under nanoindentation should not be neglected during the interpretation of data from this test.

3

Evaluating the bioactivity of endodontic sealers with respect to their thermo-nanomechanical properties

Marica Andreea, Fritea Luminita, Banica Florin, Hulka Iosif, Rusu Gerlinde, Sinescu Cosmin, Costea Traian Octavian, Cavalu Simona

Materials Science Poland

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2023

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Vol. 41, No. 3

126--139

EN

Physico-chemical and mechanical features of endodontic sealers are essential functional properties involved in their sealing ability, osteoconductivity, and biocompatibility. Four different root canal sealers (Ceraseal, MTA Fillapex, AH Plus and Sealapex) were investigated in this study in order to evaluate the thermal and nanomechanical features in relation to their bioactivity potential. The nano-hardness values respected the descendent trend: HCeraseal >HSealapex >HMTA >HAHPlus, being influenced by the percent of the inorganic component in the samples, identified as residual mass in TGA/DTG (Thermogravimetrical Analysis/ Derivative Thermogravimetry) thermograms. Based on electrochemical measurement in SBF (Simulated Body Fluid) and surface investigations by SEM/EDX, we found that the bioactivity potential decreased in the following order: Ceraseal > MTA Fillapex >AH Plus >Sealapex. The highest bioactivity in the case of Ceraseal was evidenced in terms of apatite-like spherulites observed to cover the surface after 28 days incubation in SBF, and Ca/P ratio 1.71, along with the dynamic release and consumption of Ca2+ and PO43− in SBF. On the opposite side, lack of mineralization was noticed on the surface of Sealapex sample. Knowledge about the proper thermo-mechanical, biological and physico-chemical properties of the root canal materials is important in order to allow a correct material selection, either as premixed or two-component formulation, requiring good sealing or immediate therapeutic effect.

4

Biological and mechanical research of titanium implants covered with bactericidal coating

Malisz Klaudia, Świeczko-Żurek Beata

Engineering of Biomaterials

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2022

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vol. 25, no. 165

17--22

EN

Materials used in bone implants should not only be non- -toxic to the surrounding tissues, but also should promote osseointegration and minimize the risk of infection. Infections are a serious problem contributing to implantation failure. They are associated with pain, immobilization, and the necessity of reoperation. In extreme cases, they can lead to significant inflammatory changes in the bones, which, in turn, can lead to amputation and even death. After implantation, the surrounding tissues are damaged. In addition, implants are susceptible to bacterial colonization due to the lack of microcirculation. Therefore, scientists are working on antibacterial coatings to prevent the adhesion of bacteria before tissue regeneration. The paper concerns the biological and mechanical properties of titanium implants with an antibacterial coating. The Ti13Zr13Nb alloy samples were coated with hydroxyapatite (HAp) coatings using the electrophoretic deposition technique (EPD). Subsequently, the surface of the samples was modified with silver, copper, and nickel nanoparticles by the immersion method. Different titanium sample types (i.e. HAp-only and nanometals-enriched coatings) were placed in a bacterial solution for a period of one month. Each sample was examined using scanning electron microscopy (SEM), nanoindentation, nanoscratch, and contact angle tests. The significant amount of dead biofilm on the surface proves the effectiveness of antibacterial activity. The wettability assessment showed that the samples were hydrophilic. The conducted tests of mechanical properties indicate the heterogeneity of the coatings.

5

Evaluation of capabilities of the nanoindentation test in the determination of flow stress characteristics of the matrix material in porous sinters

Madej Lukasz, Legwand Adam, Setty Mohan, Mojzeszko Mateusz, Perzyński Konrad, Roskosz Stanisław, Chrapoński Jacek

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 1

art. no. e21, 2022

EN

Herein, we evaluate the nanoindentation test capabilities in the determination of flow stress characteristics of the matrix material in porous sinters. The Distaloy AB sample with 15% porosity after the sintering operation is selected as a case study for the investigation. 2D and 3D imaging techniques are employed first to highlight difficulties in identifying reliable nano hardness measurement zones for further properties evaluation. Then, nanoindentation test results are acquired with Berkovich tip pressed under various loads at different locations in the sample. Systematic indentations in the quartz sample are used as a cleaning procedure to minimize the effect of the possible build-up around the indenter tip. The representative indentation load range is selected based on the extracted material characteristics. With that, the stress–strain response of the sinter matrix material is identified. The reliability of the determined flow stress curve is confirmed with the use of conical nanoindentation measurement results and finite element simulations. Obtained results show that it is possible to calculate reliable flow stress characteristics of the matrix in the porous samples, with the assumption that experiments under various loading conditions and from various locations in the matrix are performed. It is also pointed out that various indentation loads should be used to eliminate the influence of the pile-up or scale effects that affect the overall material response.

6

Effect of Nanoindentation Rate on Plastic Deformation in Cu Thin Films

Chocyk Dariusz, Zientarski Tomasz

Advances in Science and Technology. Research Journal

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2022

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Vol. 16, no 1

170--179

EN

The paper investigates the nanoindentation process with different rates in the Cu (001) of FCC system. The indentation process was done using molecular dynamics simulation based on the embedded atom method theory and Morse potential. Simulation process of indentation used a rigid spherical indenter with the diamond structure. To structure characterization we applied the adaptive common neighbour and the dislocation extraction analysis. It was found that the range of the linear change of the indentation force depends on the rate of response of the system. The initial range of the linear dependence of stress evolution also depends on the rate of indentation. Moreover, the average total normal stress in the system is only compressive. After linear changes, we observe oscillating changes in stress evolution. During indentation, for the range of linear changes of stress, dislocations aggregated only around the indenter surface. The creation of dislocations is directly connected with the structural changes. The structure analysis revealed the formation of HCP and BCC structure in the Cu (001) of FCC systems and a correlation with the creation of dislocations.

7

Wpływ obróbki termoplastycznej tytanu Grade 2 na właściwości nanoindentacyjne

Bańczerowski Jakub

Inżynieria Powierzchni

|

2021

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nr 2

17--21

PL

Czysty tytan jest materiałem pożądanym w biotechnologii ze względu na doskonalą biozgodność oraz brak toksycznych pierwiastków, takich jak wanad czy aluminium. Niestety w stosunku do powszechnie używanego stopu na protezy Ti6Al4V jest on materiałem o niskich właściwościach mechanicznych. Obróbka termoplastyczna tytanu miała na celu poprawę jego właściwości mechanicznych poprzez zredukowanie wielkości ziarna. Wykonano eksperyment polegający na ściskaniu próbek tytanu w podwyższonej temperaturze i przy różnych prędkościach odkształceń. Uzyskano krzywą naprężenie-odkształcenie oraz obrazy mikrostruktury tytanu, które wskazywały na redukcję ziarna. Następnie wykonano pomiary nanoindentacyjne twardości oraz modułu Younga. Wyniki wskazują na nieznaczny wzrost twardości i sztywności w większości przypadków. Dla wysokich prędkości odkształcenia zaobserwowano spadek tych wartości.

EN

Pure titanium is a desired material in biotechnology due to its excellent biocompatibility and the absence of toxic elements like vandium or aluminium. Unfortunately, in comparison to widely used Ti6Al4V alloy it has low strenght properties. Therefore, thermoplastic processing was used as means to improve its mechanical properties by the grain size reduction. An experiment of samples compression in raised temperature and various strain rates was conducted. The stress-strain curves and microstructure observations were made. Both indicated grain reduction. In the next step nanoindentation hardness and Young modulus measurements were made. The results indicate slight increase in hardness and stiffness in most cases. For the high strain rates a decrease in those values was observed.

8

Considering semi-crystallinity in molecular simulations of mechanical polymer properties : using nanoindentation of polyethylene as an example

Fritz Susanne

Computer Methods in Materials Science

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2021

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Vol. 21, No. 1

35--50

EN

Molecular dynamic (MD) simulations have been used to investigate the response of semi-crystalline polymers in nanoindentation tests, using polyethylene (PE) as an example. To that purpose, semi-crystalline simulation boxes of linear PE with various chain lengths up to C2000 were created by homogeneous nucleation during the non-isothermal cooling of melts. The final crystallinity depended on the chain length and the cooling rate used and could be estimated using various parameters like density, fraction of bonds in trans conformation, and energy terms. The simulation boxes were transferred into surface models and subjected to nanoindentation tests using non equilibrium MD. This allowed the deformation behaviour of the material to be analysed directly. Strong dependencies on the crystallinity of the PE were found, which underlines the importance of considering crystallinity when investigating the mechanical properties of semi-crystalline polymers by means of simulations.

9

The Influence of Copper Powder Morphology on Mechanical Properties of Low-Pressure Cold Sprayed Coatings

Grygier Dominika, Rutkowska-Gorczyca Małgorzata, Winnicki Marcin G., Wojdat Tomasz

Archives of Metallurgy and Materials

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2021

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Vol. 66, iss. 2

573--580

EN

Thermal spraying methods are commonly used to regenerate damaged surface or change materials surface properties. One of the newest methods is cold spraying, where coating is deposited of material in the solid state. Therefore shape and size of the powder particles are very important parameters. The article presents the influence of copper powder morphology on mechanical properties of the coatings (adhesion, hardness, Young’s modulus) deposited with the Low Pressure Cold spraying method on the AA1350 aluminium alloy substrate. The coatings were deposited using two commercially available copper powders with spherical and dendritic morphology and granulation of -40+10 μm. The bond strength of coatings was determined with the pull off method, the hardness with the Vickers method at load of 2.94 N, while the Young’s modulus through measurement of nanoindentation. Microstructure of the coatings was analysed using the light and scanning electron microscopy (SEM). Shape of the powder influences mechanical properties of the coating significantly. The coatings deposited with dendritic powder had low mechanical properties, hardness of the 81 HV0.3 order and adhesion of about 4 MPa. However changing powder morphology to spherical increased hardness of the coating to 180 HV0.3 and adhesion to 38.5 MPa.

10

The Effects of Grain Boundary Structures on Mechanical Properties in Nanocrystalline Al Alloy

Jang Jin Man, Lee Wonsik, Ko Se-Hyun

Archives of Metallurgy and Materials

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2021

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Vol. 66, iss. 4

971--975

EN

This study investigates the effects of grain boundary structures on mechanical properties of nanocrystalline Al-0.7Mg-1.0Cu alloy using nanoindentation system. Grain boundary structure transforms to high angle grain boundaries from low angle ones with increase of heat treatment temperature and the transformation temperature is about 400°C. Young’s modulus and hardness are higher in sample with low angle grain boundaries, while creep length is larger in sample with high angle ones. These results indicate that progress of plastic deformation at room temperature is more difficult in sample with low angle ones. During compression test at 200°C, strain softening occurs in all samples. However, yield strength in sample with low angle grain boundaries is higher twice than that with high angle ones due to higher activation energy for grain boundary sliding.

11

Identification of changes in mechanical properties of sandstone subjected to high temperature: meso-and micro-scale testing and analysis

Różański Adrian, Różańska Anna, Sobótka Maciej, Pachnicz Michał, Bukowska Mirosława

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 1

461--482

EN

Material properties largely depend on their structure, and are strongly dependent on the scale of observation. Under the influence of various processes, the structure of a material can undergo evolution, which leads to major changes in the mechanical parameters and morphology of the medium. To understand the behaviour of a given material exposed to the influence of various factors, e.g. loading and temperature treatment, and to be able to modify it appropriately, it is crucial to recognize its structure both in the scale of engineering applications and at the micro-scale. The article proposes a procedure for assessing changes in the structure of sandstone exposed to the temperature treatment. The presented procedure allows the morphology of the material to be evaluated and the influence of temperature treatment on mechanical parameters of rocks to be analysed, by combining use of different laboratory techniques. The changes in rock material have been characterized using three investigative techniques, i.e. a uniaxial compression test, nanoindentation and micro-computed tomography. The uniaxial compression tests were carried out for 11 different temperature values in the range of 23–1000 °C, which enabled the determination of the change in uniaxial compressive strength and Young’s modulus of the sandstone as a function of temperature. Micro-scale laboratory tests were utilised to identify changes in the mechanical and morphological parameters of the sandstone exposed to the temperature of 1000 °C. The results were referred to those obtained for the reference samples, i.e. not subjected to heating (T = 23 °C). Comparison of the results showed an evident relation between the microstructure changes and the mesoscopic properties.

12

Microstructure and mechanical properties of laser surface-treated Ti13Nb13Zr alloy with MWCNTs coatings

Majkowska-Marzec Beata, Sypniewska Joanna

Advances in Materials Science

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2021

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Vol. 21, nr 4(70)

5--18

EN

Laser surface modification of titanium alloys is one of the main methods of improving the properties of titanium alloys used in implantology. This study investigates the microstructural morphology of a laser-modified surface layer on a Ti13Nb13Zr alloy with and without a carbon nanotube coating deposited by electrophoretic deposition. Laser modification was performed for samples with and without carbon nanotube coating for two different laser powers of 800 W and 900 W and for different scan rates: 3 mm/s or 6 mm/s at 25 Hz, and the pulse duration was 2.25 ms or 3.25 ms. A scanning electron microscope SEM was used to evaluate the surface structure of the modified samples. To observe the heat-affected zones of the individual samples, metallographic samples were taken and observed under an optical microscope. Surface wettability tests were performed using a goniometer. A surface roughness test using a profilograph and a nanoindentation test by NanoTest™ Vantage was also performed. Observations of the microstructure allowed to state that for higher laser powers the surfaces of the samples are more homogeneous without defects, while for lower laser powers the path of the laser beam is clearer and more regular. Examination of the microstructure of the cross-sections indicated that the samples on which the carbon nanotube coating was deposited are characterized by a wider heat affected zone, and for the samples modified at 800 W and a feed rate of 3 mm/s the widest heat affected zone is observed. The wettability tests revealed that all the samples exhibit hydrophilic surfaces and the samples with deposited carbon nanotube coating increase it further. Surface roughness testing showed a significant increase in Ra for the laser-modified samples, and the presence of carbon nanotubes further increased this value. Nanoindentation studies showed that the laser modification and the presence of carbon coating improved the mechanical properties of the samples due to their strength.

13

Nanoindentation tests titanium alloy Ti-6Al-4V after interference laser treatment

Jażdżewska Magdalena, Trochonowska Dominika B., Bartmański Michał

Inżynieria Materiałowa

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2020

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Vol. 41, nr 4

9--12

EN

The study aimed was to assess selected mechanical properties of surface layers obtained after interference laser treatment – DLIL of titanium alloy Ti-6Al-4V used for implants. The samples were melted in still air at room temperature, for this purpose Nd:YAG laser was used, the number of laser shots was variable. Next, nanoindentation tests were performed, based on which Young’s modulus and nanohardness in the obtained surface layers were determined. An increase in nanohardness is observed in the surface layers after laser melting. An increase in the modulus of elasticity and higher hardness was observed for both the first and second areas on the sample surface. In the case of a sample for which three laser beam shots were used, hardness and Young’s modulus almost doubled. On the basis of the obtained results, it was found that the modified Ti-6Al-4V alloy can be used as an implant material, and the proposed method of modifying its surface may extend the life of such implants and improve their frictional properties.

PL

Celem pracy była ocena wybranych właściwości mechanicznych warstw powierzchniowych otrzymanych po laserowej obróbce interferencyjnej – DLIL stopu tytanu Ti-6Al-4V stosowanego na implanty. Próbki nadtopiono w spokojnym powietrzu w temperaturze pokojowej, w tym celu wykorzystano laser Nd:YAG, ilość strzałów lasera była zmienna. Następnie wykonano badania nanoindentacji, na podstawie których określono moduł Younga oraz nanotwardość w otrzymanych warstwach powierzchniowych. Obserwowano wzrost nanotwardości warstw powierzchniowych po obróbce laserowej. Zaobserwowano wzrost modułu sprężystości i większą twardość zarówno dla pierwszego, jak i drugiego obszaru na powierzchni próbki. W przypadku próbki, dla której zastosowano trzy strzały wiązki laserowej, twardość i moduł Younga wzrosły prawie dwukrotnie. Na podstawie uzyskanych wyników stwierdzono, że zmodyfikowany stop Ti-6Al-4V może być stosowany jako materiał implantologiczny, a proponowana metoda modyfikacji jego powierzchni może wpływać na wydłużenie żywotności takich implantów oraz poprawiać ich właściwości cierne.

14

Creep, shrinkage and permeation characteristics of geopolymer aggregate concrete: long-term performance

Seneviratne Charitha, Gunasekara Chamila, Law David W., Setunge Sujeeva, Robert Dilan

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 4

633--647

EN

The long-term impact on creep, drying shrinkage, and permeation characteristics of an innovative concrete produced with manufactured geopolymer coarse aggregate (GPA) has been investigated and compared with quarried Basalt aggregate concrete. Microstructure and pore-structure development up to 1 year were examined through scanning electron microscopy, nanoindentation, and X-ray computed tomography. Compressive strength and elastic modulus of GPA concrete varied from 34.6 to 50.8 and 18.5 to 20.5 GPa, respectively, between 28 and 365 days. The 1-year creep strain of GPA concrete was 747 microstrain while the calculated creep coefficient was 0.97, which is significantly lower than the creep coefficient predicted by AS 3600 and CEB-FIP models. Moreover, the 365-day drying shrinkage is 570 microstrain, which is also lower than the maximum permissible limit specified by AS3600. The GPA concrete displayed high water absorption, but lower air and water permeability compared to Basalt aggregate concrete. This is attributed to a porous surface layer with large number of capillaries increasing the water absorption of GPA concrete through capillary suction. The discontinuity in the pore network coupled with a condensed interfacial transition zone formed in GPA concrete could be the reason for lower permeability. Overall, the long-term performance of the GPA demonstrates a potential as a lightweight coarse aggregate for concrete, with the added advantage of reducing the environmental impact utilizing fly ash from coal-fired power generation.

15

Application of nanoindentation to evaluate the hardness and yield strength of brass joints produced by FSW: microstructural and strengthening mechanisms

Heidarzadeh A., Paidar M., Güleryüz G., Barenji R. Vatankhah

Archives of Civil and Mechanical Engineering

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2020

|

Vol. 20, no. 2

158--166

EN

Nanoindentation test was employed to measure the actual hardness and yield strength of the stir zone in the friction stir-welded single-phase brass joints. For this aim, different joints were prepared according to an experimental matrix based on the central composite rotatable design. In this design matrix, the tool rotational speed, tool traverse speed, and tool axial force were the input parameters. The outputs were the hardness and yield strength of the joints. To measure the hardness and tensile strength of the joints, the nanoindentation test was employed. Moreover, electron back scattered diffraction and transmission electron microscopy techniques were used to study the microstructural features. The results showed that by decreasing rotational speed and axial force, and by increasing the traverse speed, the hardness and yield strength of the joints were increased. In other words, lower heat inputs caused higher strength in the joints. Finer grain sizes, larger grain average misorientation amounts, i.e., existence of more dislocations, and greater Taylor factors in the lower heat input joints revealed that the influence of grain boundaries, dislocations, and texture were the origins of better mechanical properties.

16

Crystal plasticity finite element simulations of the indentation test

Frydrych Karol

Computer Methods in Materials Science

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2019

|

Vol. 19, No. 2

41--49

EN

The goal of the paper is to report the successful simulations of the nanoindentation problem. The finite-strain isotropicelasto-plasticity and crystal elasto-plasticity models used for the simulations are described. The developed contact formulation describing the contact with rigid surface approximating pyramidal indenter is presented. Both tensile stress-strain andindentation load-penetration curves obtained with a single set of material parameters are presented to be in the satisfactoryagreement with experimental data. It seems that such a result is presented for the first time.

PL

Celem pracy jest przedstawienie pomyślnego wyniku symulacji zadania nanoindentacji. Opisano wykorzystane w symulacjach modele izotropowej sprężysto-plastyczności oraz sprężysto-plastyczności kryształów. Przedstawiono również sformułowanie kontaktu ze sztywną powierzchnią przybliżającą końcówkę indentera o kształcie ostrosłupa. Zaprezentowano zarówno krzywe naprężenie-odkształcenie uzyskane w symulacji testu rozciągania, jak i siła-zagłębienie, które otrzymano przy użyciu pojedynczego zestawu parametrów materiałowych. Uzyskano zadowalająca zgodności z eksperymentem. Wydaje się, że tego typu wyniki zostały zaprezentowane po raz pierwszy.

17

The influence of laser alloying of Ti13Nb13Zr on surface topography and properties

Tęczar P., Majkowska-Marzec Beata, Bartmański Michał

Advances in Materials Science

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2019

|

Vol. 19, nr 1(59)

44--56

EN

The laser alloying is a continually developing surface treatment because of its significant and specific structuration of a surface. In particular, it is applied for Ti alloys, being now the most essential biomaterials` group for load-bearing implants. The present research was performed on the Ti13Nb13Zr alloy subject to laser modification in order to determine the treatment effects on surface topography and its some mechanical properties like nanohardness, Young's modulus, roughness. A pulse laser Nd:YAG was applied at three different laser pulse regimes: either 700 W, 1000 W or 1000 W treatment followed by 700 W modification at a pulse duration of 1 ms. The surface topography and morphology were examined using light microscopy and scanning electron microscopy with spectroscope of X-ray energy dispersion. The mechanical properties were determined by nanoindentation tests and surface roughness with a use of profilograph. The wettability was tested with a goniometer. The obtained results demonstrate complex behavior of the material surface: decrease in penetration distance and increase in hardness after first laser treatment, maintenance of this trend when machining using a higher laser pulse power, followed by an increase in penetration and decrease in hardness after additional laser treatment at lower power input, due to which a surface with fewer defects is obtained. The change in Young`s modulus follows the change in other mechanical properties, but not a change in roughness. Therefore, the observed hardening with the increase of the laser pulse power and then a small softening with the use of additional treatment with lower power can be attributed to some processes of remelting, diffusion and crystallization, sensitive to the previous surface state and heat energy flux. Despite that, the laser treatment always caused a significant hardening of the surface layer.

18

Surface characterization of the raw and cooked bovine cortical metatarsal bone

Petrovic Bojan B., Kojic Sanja, Peric Tamara O., Šipovac Milica, Lazarevic Jovana, Stefanovic Sofija, Stojanovic Goran

Acta of Bioengineering and Biomechanics

|

2019

|

Vol. 21, no. 1

13--21

EN

The purpose of this study was to quantify the elastic properties and evaluate microscopical features of raw and boiled metatarsal bovine bone. Methods: The elastic modulus, hardness and microscopic surface of raw and cooked bovine metatarsal bone have been investigated using nanoindentation, SEM/EDX and Panasis microscope. Results: Regarding raw bovine bone, the average elastic modulus was 30.515 ± 6,769 GPa, while the average hardness was 0.5683 ± 0.211 GPa. When it comes to boiled bone corresponding values were 22.298 ± 7.0303 GPa and 0.408 ± 0.199 GPa, respectively. The values for investigated parameters were significantly higher ( p < 0.05) in raw bone specimens. Elastic modulus significantly correlated with hardness ( p < 0.05). EDX analysis revealed significant decrease in wt% of oxygen in boiled samples ( p < 0.05) No significant differences could be observed in SEM images particularly when analysing in smaller magnifications. Using higher magnification, additional branching of the existing voids as well as discrete reorganization and smoother edges of nutrient canals could be observed. The surface of boiled specimens was without the presence of crusts and layering, and no microscopical evidence of structural damage could be observed. Conclusions: This study provides detailed analysis of hardness, elastic modulus of raw and cooked bovine bone and their relation and changes during exposure to temperature. These results of elastic moduli and hardness could be comparable to similar studies of bovine and human bone tissue, but the careful analysis of experimental design, type of the bone as well as limitations of the employed techniques must be carried out before interpolation of the results to other theoretical, clinical, biomaterial and archeological studies.

19

Influence of dental materials on hardness and Young’s modulus of the surface layers of tooth enamel formed as a result of friction

Wojda Sylwia, Sajewicz Eugeniusz

Acta of Bioengineering and Biomechanics

|

2019

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Vol. 21, no. 1

129--139

EN

The purpose of this work was to determine the influence of dental materials used as permanent fillings on the mechanical properties of the tooth enamel surface layer subjected to friction with these materials. Methods: Dental composite materials (five types) were differentiated in terms of size and shape of the filler particles and matrix type over the course of tests on the chewing simulator under two different loads set during friction. Next, it was measured values of wear and nanoindentation for the resulting friction rates on the enamel (3 different load ranges). Results: It was found that the enamel’s resistance to tribological wear is significantly higher than that of the tested dental materials. It is also important to note that, depending on the penetration depth of the indenter (depends on the indenter pressure), different hardness values and Young’s modulus of enamel were obtained after friction with different dental materials. This demonstrates the formation of a surface layer with different properties than the native material. Conclusions: Analysis of the obtained results suggests the existence of different tribological wear mechanisms, as evidenced by significant differences in the wear values of dental materials and enamel. The data show that the enamel surface layer modified by the contacting dental material is shaped to a certain depth, and different thickness ranges of the changed layer have different properties.

20

AFM and nanoindentation study of selected aluminium alloys

Barényi I., Eckert M., Majerík J., Bezecný J.

Zeszyty Naukowe Politechniki Rzeszowskiej. Mechanika

|

2018

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z. 90 [298], nr 2

143--152

EN

The structure of EN AW 6082 aluminium alloy is investigated in this paper. Atom force microscopy (AFM) is used to identify present phases and their morphology. AFM enabled to observe even the precipitates, their size and distribution. In the next step, some structure constituent described by AFM were evaluated by the nanoindentation process to determine their local mechanical properties, such as nanohardness and reduced modulus.

PL

W artykule opisano strukturę stopu aluminium AW 6082. Mikroskopia sił atomowych (AFM) służy do identyfikacji obecnych faz i ich morfologii. AFM umożliwił obserwację nawet wtrąceń, ich wielkości i rozmieszczenia. W następnym etapie niektóre składniki struktury opisane przez AFM zostały ocenione w procesie nanoindentacji w celu określenia ich lokalnych właściwości mechanicznych, takich jak nanotwardość i zredukowany moduł.