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1
Abdullah, Izhan, Muhammad Nubli Zulkifli, Azman Jalar e R. Ismail. "Deformation behavior relationship between tensile and nanoindentation tests of SAC305 lead-free solder wire". Soldering & Surface Mount Technology 30, n. 3 (4 giugno 2018): 194–202. http://dx.doi.org/10.1108/ssmt-07-2017-0020.
Testo completoAbstract (sommario):
PurposeThe relationship between the bulk and localized mechanical properties is critically needed, especially to understand the mechanical performance of solder alloy because of smaller sizing trend of solder joint. The purpose of this paper is to investigate the relationship between tensile and nanoindentation tests toward the mechanical properties and deformation behavior of Sn-3.0Ag-0.5Cu (SAC305) lead-free solder wire at room temperature.Design/methodology/approachTensile test with different strain rates of 1.5 × 10-4 s-1, 1.5 × 10-3 s-1, 1.5 × 10-2 s-1 and 1.5 × 10-1 s-1 at room temperature of 25°C were carried out on lead-free Sn-3.0Ag-0.5Cu (SAC305) solder wire. Stress–strain curves and mechanical properties such as yield strength (YS), ultimate tensile strength (UTS) and elongation were determined from the tensile test. Load-depth (P-h) profiles and micromechanical properties, namely, hardness and reduced modulus, were obtained from nanoindentation test. In addition, the deformation mechanisms of SAC305 lead-free solder wire were obtained by measuring the range of creep parameters, namely, stress exponent and strain rate sensitivity, using both of tensile and nanoindentation data.FindingsIt was observed that qualitative results obtained from tensile and nanoindentation tests can be used to identify the changes of the microstructure. The occurrence of dynamic recrystallization and the increase of ductility obtained from tensile test can be used to indicate the increment of grain refinement or dislocation density. Similarly, the occurrence of earliest pop-in event and the highest occurrence of pop-in event observed from nanoindentation also can be used to identify the increase of grain refinement and dislocation density. An increment of strain rates increases the YS and ultimate UTS of SAC305 solder wire. Similarly, the variation of hardness of SAC305 solder wire has the similar trend or linear relationship with the variation of YS and UTS, following the Tabor relation. In contrast, the variation of reduced modulus has a different trend compared to that of hardness. The deformation behavior analysis based on the Holomon’s relation for tensile test and constant load method for nanoindentation test showed the same trend but with different deformation mechanisms. The transition of responsible deformation mechanism was obtained from both tensile and nanoindentation tests which from grain boundary sliding (GBS) to grain boundary diffusion and dislocation climb to grain boundary slide, respectively.Originality/valueFor the current analysis, the relationship between tensile and nanoindentation test was analyzed specifically for the SAC305 lead-free solder wire, which is still lacking. The findings provide a valuable data, especially when comparing the trend and mechanism involved in bulk (tensile) and localized (nanoindentation) methods of testing.
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Němeček, Jiří, e Jiří Němeček. "Microscale Tests of Cement Paste Performed with FIB and Nanoindentation". Key Engineering Materials 760 (gennaio 2018): 239–44. http://dx.doi.org/10.4028/www.scientific.net/kem.760.239.
Testo completoAbstract (sommario):
This study deals with experimental determination of tensile properties of cement paste hydration products at micro-scale. Cantilever micro-beams with length of about 16 µm and pentagon cross section with micrometer dimensions were fabricated by focused ion beam milling on hydrated cement paste samples. Nanoindentation was used for evaluating elastic properties while tensile properties were derived from beam bending tests. Displacement controlled micro-scale tests give access to both tensile strength and estimates of fracture energy based on the load-displacement curves measured with the nanoindenter. The mean tensile strength and the fracture energy of inner hydration product were assessed as 791 MPa and 16.7 J/m2, respectively. The huge difference of the micro-scale properties when compared to macroscopic values comes from the scaling properties of concrete.
3
Bencomo-Cisneros, J. A., A. Tejeda-Ochoa, J. A. García-Estrada, C. A. Herrera-Ramírez, A. Hurtado-Macías, R. Martínez-Sánchez e J. M. Herrera-Ramírez. "Characterization of Kevlar-29 fibers by tensile tests and nanoindentation". Journal of Alloys and Compounds 536 (settembre 2012): S456—S459. http://dx.doi.org/10.1016/j.jallcom.2011.11.031.
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Němeček, Jiří. "Nanoindentation Applied to Materials with an Inner Structure". Key Engineering Materials 586 (settembre 2013): 55–58. http://dx.doi.org/10.4028/www.scientific.net/kem.586.55.
Testo completoAbstract (sommario):
Nowadays, nanoindentation is commonly applied to various materials to assess micromechanical properties. Often, exact microstructure of the material building blocks is not properly analyzed which may introduce large discrepancies in the data obtained from different tests. It is shown in the paper, that different deformation mechanisms in tension and compression take place for the tested materials which is demonstrated by large differences between the measured nanoindentation moduli and macroscopic tensile elastic moduli. The situation is illustrated on several types of biological and man-made fibers. Differences ~44-57% in elastic moduli evaluated from the two tests appear in case of biological fibers, ~68% difference was found for high strength PVA fibers and 767% (!) for carbon fibers.
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Long, Xu, Xiaodi Zhang, Wenbin Tang, Shaobin Wang, Yihui Feng e Chao Chang. "Calibration of a Constitutive Model from Tension and Nanoindentation for Lead-Free Solder". Micromachines 9, n. 11 (20 novembre 2018): 608. http://dx.doi.org/10.3390/mi9110608.
Testo completoAbstract (sommario):
It is challenging to evaluate constitutive behaviour by using conventional uniaxial tests for materials with limited sizes, considering the miniaturization trend of integrated circuits in electronic devices. An instrumented nanoindentation approach is appealing to obtain local properties as the function of penetration depth. In this paper, both conventional tensile and nanoindentation experiments are performed on samples of a lead-free Sn–3.0Ag–0.5Cu (SAC305) solder alloy. In order to align the material behaviour, thermal treatments were performed at different temperatures and durations for all specimens, for both tensile experiments and nanoindentation experiments. Based on the self-similarity of the used Berkovich indenter, a power-law model is adopted to describe the stress–strain relationship by means of analytical dimensionless analysis on the applied load-penetration depth responses from nanoindentation experiments. In light of the significant difference of applied strain rates in the tensile and nanoindentation experiments, two “rate factors” are proposed by multiplying the representative stress and stress exponent in the adopted analytical model, and the corresponding values are determined for the best predictions of nanoindentation responses in the form of an applied load–indentation depth relationship. Eventually, good agreement is achieved when comparing the stress–strain responses measured from tensile experiments and estimated from the applied load–indentation depth responses of nanoindentation experiments. The rate factors ψ σ and ψ n are calibrated to be about 0.52 and 0.10, respectively, which facilitate the conversion of constitutive behaviour from nanoindentation experiments for material sample with a limited size.
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Li, Cong, Hongwei Zhao, Linlin Sun e Xiujuan Yu. "In situ nanoindentation method for characterizing tensile properties of AISI 1045 steel based on mesomechanical analysis". Advances in Mechanical Engineering 11, n. 7 (luglio 2019): 168781401986291. http://dx.doi.org/10.1177/1687814019862919.
Testo completoAbstract (sommario):
A novel method for characterizing the tensile properties of AISI 1045 steel is proposed by combining the method of in situ nanoindentation test and the theory of mesomechanical analysis. First, the load–depth curves of exact location of ferrite, pearlite and grain boundary on the surface of AISI 1045 steel are obtained by 30 groups of in situ nanoindentation tests. The constitutive equation (stress–strain function) of the real-time metallographic structure is obtained by nanoindentation analysis of the above curves. Then, based on the principle of mesomechanical analysis, the computational representative volume element models are reconstructed according to the three metallographic images of AISI 1045 steel surface collected by the test equipment. Finally, taking the constitutive equation of the real-time metallographic structure as the input condition, the finite element analysis of the above representative volume element models are carried out. The data resulted from finite element analysis are taken as the tensile mechanical properties of AISI 1045 steel. The elastic modulus of AISI 1045 steel calculated is as the same as that by the traditional nanoindentation method. And, the error is less than 6% compared with the tensile test, which is within the range of the elastic modulus of the material. The error between the yield strength calculated and tensile test results is 3.4%. Due to the influence of surface cracks on the plastic deformation ability of AISI 1045 steel during tension, the error between the strain hardening index calculated and tensile test results is 7.4%. The results show that it is a more accurate nondestructive testing method in the point of material damage mechanism. On the premise of using more accurate representative volume element modelling way, this method is suitable for testing more materials.
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Lofaj, Frantisek, e Dušan Németh. "FEM of Cracking during Nanoindentation and Scratch Testing in the Hard W-C Coating/Steel Substrate System". Key Engineering Materials 784 (ottobre 2018): 127–34. http://dx.doi.org/10.4028/www.scientific.net/kem.784.127.
Testo completoAbstract (sommario):
Finite element modelling (FEM) and eXtended FEM (XFEM) combined with the experimental nanoindentation and scratch tests have been used to simulate the process of cohesive cracking in W-C coating on softer and more ductile steel substrate during nanoindentation and scratch testing. The formation of single and multiple circular “frame” cohesive cracks in the sink-in zone during nanoindentation were explained by the development of high local tensile stresses in the coatings controlled by the plastic deformation of the substrate. Analogous mechanisms were successfully applied to the simulation of multiple Chevron type cracking during scratch testing. Thus, the ability of XFEM to predict the formation of different types of cohesive cracks was confirmed. It was also demonstrated that both nanoindentation and scratch tests in combination with XFEM can be used as the methods to determine the strength and fracture toughness of thin coatings.
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Němeček, Jiří, Jan Maňák, Tomáš Krejčí e Jiří Němeček. "Small scale tests of cement with focused ion beam and nanoindentation". MATEC Web of Conferences 310 (2020): 00053. http://dx.doi.org/10.1051/matecconf/202031000053.
Testo completoAbstract (sommario):
Nanoindentation is used for characterization of small scale material properties of hydrated cement. It is employed as a precise loading tool on samples fabricated with Focused Ion Beam milling (FIB). The effect of heat on the microstructure of cement during different FIB energy loads is studied. Milling currents as low as 0.1 nA can be considered as save and not damaging. Micrometer sized beams were bent to reveal strength and fracture characteristics. Small scale elastic properties, tensile strength and fracture energy of individual low scale microstructural constituents of cement paste like C-S-H rich phases and Portlandite were assessed. Very high tensile strengths at the micrometer scale were observed for cement paste hydration products (200-700 MPa) with fracture energies 4-20 J/m2 The results are consistent with atomistic simulations and multi-scale modeling from available literature.
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Veleva, Lyubomira, Peter Hähner, Andrii Dubinko, Tymofii Khvan, Dmitry Terentyev e Ana Ruiz-Moreno. "Depth-Sensing Hardness Measurements to Probe Hardening Behaviour and Dynamic Strain Ageing Effects of Iron during Tensile Pre-Deformation". Nanomaterials 11, n. 1 (30 dicembre 2020): 71. http://dx.doi.org/10.3390/nano11010071.
Testo completoAbstract (sommario):
This work reports results from quasi-static nanoindentation measurements of iron, in the un-strained state and subjected to 15% tensile pre-straining at room temperature, 125 °C and 300 °C, in order to extract room temperature hardness and elastic modulus as a function of indentation depth. The material is found to exhibit increased disposition for pile-up formation due to the pre-straining, affecting the evaluation of the mechanical properties of the material. Nanoindentation data obtained with and without pre-straining are compared with bulk tensile properties derived from the tensile pre-straining tests at various temperatures. A significant mismatch between the hardness of the material and the tensile test results is observed and attributed to increased pile-up behaviour of the material after pre-straining, as evidenced by atomic force microscopy. The observations can be quantitatively reconciled by an elastic modulus correction applied to the nanoindentation data, and the remaining discrepancies explained by taking into account that strain hardening behaviour and nano-hardness results are closely affected by dynamic strain ageing caused by carbon interstitial impurities, which is clearly manifested at the intermediate temperature of 125 °C.
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Lofaj, František, Dušan Németh, Rudolf Podoba e Michal Novák. "Cracking in Brittle Coatings during Nanoindentation". Key Engineering Materials 662 (settembre 2015): 103–6. http://dx.doi.org/10.4028/www.scientific.net/kem.662.103.
Testo completoAbstract (sommario):
The FIB/SEM investigations of the microstructure changes in the hard brittle W-C based coating deposited on softer steel substrate after nanoindentation tests revealed that a set of approximately equidistant circular cracks forms in the coating in a sink-in zone around the indent and single cracks appear under the indenter tip. Finite element modeling (FEM) indicated development and concentration of the highest principal tensile stresses in the sink-in zone and in the zone below the indenter, which are considered to be the reason for the experimentally observed cracking. The distance from the indenter tip to the first circular crack combined with the calibration curve obtained from the FEM of the location of tensile stress maxima in sink-in zone can be used as a simple method for the determination of the strength of the studied coatings.
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Müller, Wolfgang H., Holger Worrack e Jens Sterthaus. "Experimental Setup for the Determination of Mechanical Solder Materials Properties at Elevated Temperatures". Materials Science Forum 638-642 (gennaio 2010): 3793–98. http://dx.doi.org/10.4028/www.scientific.net/msf.638-642.3793.
Testo completoAbstract (sommario):
The fabrication of microelectronic and micromechanical devices leads to the use of only very small amounts of matter, which can behave quite differently than the corresponding bulk. Clearly, the materials will age and it is important to gather information on the (changing) material characteristics. In particular, Young’s modulus, yield stress, and hardness are of great interest. Moreover, a complete stress-strain curve is desirable for a detailed material characterization and simulation of a component, e.g., by Finite Elements (FE). However, since the amount of matter is so small and it is the intention to describe its behavior as realistic as possible, miniature tests are used for measuring the mechanical properties. In this paper two miniature tests are presented for this purpose, a mini-uniaxial-tension-test and a nanoindenter experiment. In the tensile test the axial load is prescribed and the corresponding extension of the specimen length is recorded, both of which determines the stress-strain- curve directly. The stress-strain curves are analyzed by assuming a non-linear relationship between stress and strain of the Ramberg-Osgood type and by fitting the corresponding parameters to the experimental data (obtained for various microelectronic solders) by means of a non-linear optimization routine. For a detailed analysis of very local mechanical properties nanoindentation is used, resulting primarily in load vs. indentation-depth data. According to the procedure of Oliver and Pharr this data can be used to obtain hardness and Young’s modulus but not a complete stress-strain curve, at least not directly. In order to obtain such a stress-strain-curve, the nanoindentation experiment is combined with FE and the coefficients involved in the corresponding constitutive equations for stress and strain are obtained by means of the inverse method. The stress-strain curves from nanoindentation and tensile tests are compared for two mate-rials (aluminum and steel). Differences are explained in terms of the locality of the measurement. Finally, material properties at elevated temperature are of particular interest in order to characterize the materials even more completely. We describe the setup for hot stage nanoindentation tests in context with first results for selected materials.
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Rodríguez Pozo, Francisco Ramón, Daiana Ianev, Tomás Martínez Rodríguez, José L. Arias, Fátima Linares, Carlos Miguel Gutiérrez Ariza, Caterina Valentino et al. "Development of Halloysite Nanohybrids-Based Films: Enhancing Mechanical and Hydrophilic Properties for Wound Healing". Pharmaceutics 16, n. 10 (27 settembre 2024): 1258. http://dx.doi.org/10.3390/pharmaceutics16101258.
Testo completoAbstract (sommario):
Most of the therapeutic systems developed for managing chronic skin wounds lack adequate mechanical and hydration properties, primarily because they rely on a single component. This study addresses this issue by combining organic and inorganic materials to obtain hybrid films with enhanced mechanical behavior, adhesion, and fluid absorption properties. To that aim, chitosan/hydrolyzed collagen blends were mixed with halloysite/antimicrobial nanohybrids at 10% and 20% (w/w) using glycerin or glycerin/polyethylene glycol-1500 as plasticizers. The films were characterized through the use of Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and electron microscopy. The mechanical properties were evaluated macroscopically using tensile tests, and at a nanoscale through atomic force microscopy (AFM) and nanoindentation. Thermodynamic studies were conducted to assess their hydrophilic or hydrophobic character. Additionally, in vitro cytocompatibility tests were performed on human keratinocytes. Results from FTIR, TGA, AFM and electron microscopy confirmed the hybrid nature of the films. Both tensile tests and nanomechanical measurements postulated that the nanohybrids improved the films’ toughness and adhesion and optimized the nanoindentation properties. All nanohybrid-loaded films were hydrophilic and non-cytotoxic, showcasing their potential for skin wound applications given their enhanced performance at the macro- and nanoscale.
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Srivastava, Ashish Kumar, Nagendra Kumar Maurya, Manish Maurya, Shashi Prakash Dwivedi e Ambuj Saxena. "Effect of Multiple Passes on Microstructural and Mechanical Properties of Surface Composite Al 2024/SiC Produced by Friction Stir Processing". Annales de Chimie - Science des Matériaux 44, n. 6 (30 dicembre 2020): 421–26. http://dx.doi.org/10.18280/acsm.440608.
Testo completoAbstract (sommario):
The application range in defense, aerospace and automotive sectors have enabled aluminium metal matrix composites to emerge in different technological fields due to enhanced micro structural and mechanical characteristics. In the present study, friction stir processing is used to fabricate Al2024/SiC composite with one, two and three passes of the cylindrical tool. Optical microscopy and scanning electronic microscope (SEM) were used to validate the processed sample and to justify the morphological aspects. Energy dispersive spectroscopy (EDS) analysis has also performed to confirm the presence of SiC particles in the composite. It also includes the analysis of mechanical properties such as tensile strength, Rockwell hardness test and nanoindentation to characterize the prepared samples. Improvement in tensile strength with a maximum of 443 MPa, the hardness of 121 HRB and nanoindentation of the specimen was depicted through the mechanical tests.
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Němeček, Jiří, Jiří Němeček e Jan Maňák. "Fracture Properties of Cement Studied by Nanoindentation and FIB". Key Engineering Materials 784 (ottobre 2018): 3–8. http://dx.doi.org/10.4028/www.scientific.net/kem.784.3.
Testo completoAbstract (sommario):
The paper shows results of microscale experimental tests performed on cement paste specimens fabricated by focused ion beam milling. The specimens are prepared in the form of cantilever beams and loaded in bending by nanoindenter. The dimensions of specimens are in the order of a few micrometers which corresponds to the single phase size. Intact and notched specimens with a stress concentrator are tested. Tensile strength and fracture energy are derived for the hydration product by analyzing the nanoindentation data and with the aid of analytical and numerical modeling. Although small number of tests is performed good correlation of the results is reached with respect to the available literature and molecular dynamic simulations.
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Němeček, J., V. Králík, V. Šmilauer, L. Polívka e A. Jäger. "Tensile strength of hydrated cement paste phases assessed by micro-bending tests and nanoindentation". Cement and Concrete Composites 73 (ottobre 2016): 164–73. http://dx.doi.org/10.1016/j.cemconcomp.2016.07.010.
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Liović, David, Marina Franulović, Nenad Gubeljak, Ervin Kamenar, Dražan Kozak e Emanuele Vaglio. "Tensile and nanoindentation tests analysis of Ti6Al4V alloy manufactured by laser powder bed fusion". Procedia Structural Integrity 53 (2024): 37–43. http://dx.doi.org/10.1016/j.prostr.2024.01.005.
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Yan, Shuogeng, Kun Wang e Zhengzhi Wang. "A Comparative Study on the Microscale and Macroscale Mechanical Properties of Dental Resin Composites". Polymers 15, n. 5 (23 febbraio 2023): 1129. http://dx.doi.org/10.3390/polym15051129.
Testo completoAbstract (sommario):
Dental resin composites are universal restorative materials, and various kinds of fillers are used to reinforce their mechanical properties. However, a combined study on the microscale and macroscale mechanical properties of dental resin composites is missing, and the reinforcing mechanism of the composites is still not fully clarified. In this work, the effects of the nano-silica particle on the mechanical properties of dental resin composites were studied by combined dynamic nanoindentation tests and macroscale tensile tests. The reinforcing mechanism of the composites was explored by combining near-infrared spectroscopy, scanning electron microscope, and atomic force microscope characterizations. It was found that the tensile modulus increased from 2.47 GPa to 3.17 GPa, and the ultimate tensile strength increased from 36.22 MPa to 51.75 MPa, with the particle contents increasing from 0% to 10%. From the nanoindentation tests, the storage modulus and hardness of the composites increased by 36.27% and 40.90%, respectively. The storage modulus and hardness were also found to increase by 44.11% and 46.46% when the testing frequency increased from 1 Hz to 210 Hz. Moreover, based on a modulus mapping technique, we found a boundary layer in which the modulus gradually decreased from the edge of the nanoparticle to the resin matrix. Finite element modeling was adopted to illustrate the role of this gradient boundary layer in alleviating the shear stress concentration on the filler–matrix interface. The present study validates mechanical reinforcement and provides a potential new insight for understanding the reinforcing mechanism of dental resin composites.
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Liao, Jin Zhi, Jian Jun Pang e Ming Jen Tan. "Nanoindentation of Multi-Wall CNT Reinforced Al Composites". Key Engineering Materials 447-448 (settembre 2010): 549–53. http://dx.doi.org/10.4028/www.scientific.net/kem.447-448.549.
Testo completoAbstract (sommario):
This work used nanoindentation to characterize the local mechanical properties of the multi-wall carbon nanotube (MWCNT) reinforced aluminum (Al) composites. The Al-MWCNT (0.5, 1.0 and 2.0 wt.%) specimens were fabricated by spark plasma sintering (SPS) followed by hot extrusion. Different local regions of the as-extruded and tensile-fractured specimen over the longitudinal and transverse section were studied by nanoindentation. The nanoindentation results were compared with the conventional macro- and mircoscopic mechanical tests, and were found in good agreement. The values of hardness (H) and elastic modulus (E) obtained reached maximum at the 0.5 wt.% MWCNT adding Al samples. E was highest in the necking region then decreased with increasing distance from the localized deformed region; while H varied in different regions. In the same region, H and V were higher in the longitudinal than those in the transverse direction, due to the texture hardening and alignment of CNT.
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Waltz, Laurent, Delphine Retraint, Arjen Roos, Patrick Olier e Jian Lu. "High Strength Nanocrystallized Multilayered Structure Obtained by SMAT and Co-Rolling". Materials Science Forum 614 (marzo 2009): 249–54. http://dx.doi.org/10.4028/www.scientific.net/msf.614.249.
Testo completoAbstract (sommario):
. In the present study, a method is presented combining surface nanocrystalline treatment (SMAT) and the co-rolling process. The aim of this duplex treatment is the development of a 316L stainless steel semi-massive multilayered bulk structure with improved yield and ultimate tensile strengths, while conserving an acceptable elongation to failure by optimizing the volume fraction and distribution of the nano-grains in the laminate. To characterize this composite structure, tensile tests as well as sharp nanoindentation tests were carried out to follow the local hardness evolution through the cross-section of the laminate. Furthermore, transmission electron microscope (TEM) observations were carried out to determine the correlation between the microstructure, the local hardness and the mechanical response of the structure.
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Laurent-Brocq, M., L. Perrière, R. Pirès, G. Bracq, T. Rieger, Y. Danard e I. Guillot. "Combining tensile tests and nanoindentation to explore the strengthening of high and medium entropy alloys". Materialia 7 (settembre 2019): 100404. http://dx.doi.org/10.1016/j.mtla.2019.100404.
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Gu, Yu Li, Chun Hu Tao, Nan Li, Zhen Wei Wei e Pu Liu. "Effect of Two Heat Treatment Processes on Microstructures and Tensile Behaviors of Ni-Based Superalloy K465". Materials Science Forum 789 (aprile 2014): 647–52. http://dx.doi.org/10.4028/www.scientific.net/msf.789.647.
Testo completoAbstract (sommario):
The effect of two heat treatment processes on microstructures and tensile behaviors of K465 superalloy was investigated and compared. The results show that hot isostatic pressing (HIP) process partly or completely eliminated the micro-porosity to densify K465 alloy, and can effectively reduce the size of γ′ phase and improve the tensile strength and plasticity of K465 alloy. Electron probe micro-analysis (EPMA) studies revealed that the element segregation ratio was smaller in the HIP process alloy than that in the ordinary process alloy. nanoindentation tests revealed that elastic modulus and the hardness in the interdendrite of K465 alloy for HIP process were higher than that for the ordinary process.
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Mayo, Unai, Nerea Isasti, José M. Rodríguez-Ibabe e Pello Uranga. "Analysis of Strain Partitioning in Intercritically Deformed Microstructures via Interrupted Tensile Tests". Metals 11, n. 1 (8 gennaio 2021): 112. http://dx.doi.org/10.3390/met11010112.
Testo completoAbstract (sommario):
Intercritically deformed steels present combinations of different types of ferrite, such as deformed ferrite (DF) and non-deformed ferrite (NDF) grains, which are transformed during the final deformation passes and final cooling step. Recently, a grain identification and correlation technique based on EBSD has been employed together with a discretization methodology, enabling a distinction to be drawn between different ferrite populations (NDF and DF grains). This paper presents a combination of interrupted tensile tests with crystallographic characterization performed by means of Electron Backscatter Diffraction (EBSD), by analyzing the evolution of an intercritically deformed micro-alloyed steel. In addition to this, and using the nanoindentation technique, both ferrite families were characterized micromechanically and the nanohardness was quantified for each population. NDF grains are softer than DF ones, which is related to the presence of a lower fraction of low-angle grain boundaries. The interrupted tensile tests show the different behavior of low- and high-angle grain boundary evolution as well as the strain partitioning in each ferrite family. NDF population accommodates most of the deformation at initial strain intervals, since strain reaches 10%. For higher strains, NDF and DF grains behave similarly to the strain applied.
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Mayo, Unai, Nerea Isasti, José M. Rodríguez-Ibabe e Pello Uranga. "Analysis of Strain Partitioning in Intercritically Deformed Microstructures via Interrupted Tensile Tests". Metals 11, n. 1 (8 gennaio 2021): 112. http://dx.doi.org/10.3390/met11010112.
Testo completoAbstract (sommario):
Intercritically deformed steels present combinations of different types of ferrite, such as deformed ferrite (DF) and non-deformed ferrite (NDF) grains, which are transformed during the final deformation passes and final cooling step. Recently, a grain identification and correlation technique based on EBSD has been employed together with a discretization methodology, enabling a distinction to be drawn between different ferrite populations (NDF and DF grains). This paper presents a combination of interrupted tensile tests with crystallographic characterization performed by means of Electron Backscatter Diffraction (EBSD), by analyzing the evolution of an intercritically deformed micro-alloyed steel. In addition to this, and using the nanoindentation technique, both ferrite families were characterized micromechanically and the nanohardness was quantified for each population. NDF grains are softer than DF ones, which is related to the presence of a lower fraction of low-angle grain boundaries. The interrupted tensile tests show the different behavior of low- and high-angle grain boundary evolution as well as the strain partitioning in each ferrite family. NDF population accommodates most of the deformation at initial strain intervals, since strain reaches 10%. For higher strains, NDF and DF grains behave similarly to the strain applied.
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Ishimoto, Takuya, e Takayoshi Nakano. "Evaluation of Mechanical Properties of Regenerated Bone by Nanoindentation Technique". Materials Science Forum 654-656 (giugno 2010): 2220–24. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.2220.
Testo completoAbstract (sommario):
To evaluate the material parameters of regenerated bone, it is important to clarify the mechanical performance of the regenerated portion. In general, the shape and size of regenerated bone tissue is heterogeneous. It is often difficult to elucidate material properties by means of conventional mechanical tests such as compressive and/or tensile tests and bending tests. The nanoindentation technique has been utilized to evaluate the material properties of small or microstructured materials because they do not necessarily require a large well-designed specimen. Thus, this technique may be useful for the evaluation of the material properties of regenerated bone tissue. In this study, this technique was applied for the assessment of the Young’s modulus and hardness of regenerated and intact long bones of a rabbit. The regenerated bone exhibited a significantly lower Young’s modulus and hardness than the intact bone. The regenerated long bone also exhibited impaired mechanical properties, which may have been caused by the difference in the nano-organization of its collagen fibers and mineral crystals (the main components of bone tissue), from that of the intact bone.
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Wang, Wei, Xiang Fang, Xuanguo Wang, Michel Andrieux e Vincent Ji. "Mechanism of Blunt Punching Tools’ Influence on Deformation and Residual Stress Distribution". Metals 11, n. 12 (14 dicembre 2021): 2029. http://dx.doi.org/10.3390/met11122029.
Testo completoAbstract (sommario):
Punching is the main manufacturing process with high efficiency and machining accuracy used to produce the iron cores of motors. However, it usually introduces residual stress at the cutting edge and affects the magnetic properties of the iron core. Further studies show that the tensile residual stress (TRS) has a negligible effect on the magnetic properties, compared with the compressive stress. The blunt punch tools cause local TRS and the formation of local large plastic deformation (PD) at the cutting edge as the cost. The PD has a more serious effect on the magnetic properties of materials than TRS. Therefore, this study mainly focused on local deformation distribution and the associated microstructure evolution using EBSD (Electron Backscatter Diffraction) and finite element analysis; and the formation mechanism of tensile residual stress during the punching process at the cutting edge of a non-oriented silicon steel after punching with blunt tools, by using nanoindentation and a numerical simulation. The experimental results showed the existence of a specific bending area, a highly deformed area and a large burr at the cutting edge. These direct observations were confirmed with those obtained by the simulation model. Furthermore, the tensile residual stress on the surface was verified through nanoindentation tests and by a numerical simulation. The results indicate also that the formation of a tensile residual stress zone depends especially on the bending area formed during punching with blunt tools.
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Hu, Wei Ping, Si Yuan Zhang, Xiao Yu He, Zhen Yang Liu, Rolf Berghammer e Günter Gottstein. "Investigations on Microstructure Evolution and Deformation Behavior of Aged and Ultrafine Grained Al-Zn-Mg Alloy Subjected to Severe Plastic Deformation". Materials Science Forum 667-669 (dicembre 2010): 253–58. http://dx.doi.org/10.4028/www.scientific.net/msf.667-669.253.
Testo completoAbstract (sommario):
An aged Al-5Zn-1.6Mg alloy with fine η' precipitates was grain refined to ~100 nm grain size by severe plastic deformation (SPD). Microstructure evolution during SPD and mechanical behaviour after SPD of the alloy were characterized by electron microscopy and tensile, compression as well as nanoindentation tests. The influence of η' precipitates on microstructure and mechanical properties of ultrafine grained Al-Zn-Mg alloy is discussed with respect to their effect on dislocation configurations and deformation mechanisms during processing of the alloy.
27
Hwang, Tae Kyung, e Soon Bok Lee. "Effects of Microstructure on Material Behaviors of Solder Alloys". Key Engineering Materials 297-300 (novembre 2005): 825–30. http://dx.doi.org/10.4028/www.scientific.net/kem.297-300.825.
Testo completoAbstract (sommario):
The leading candidates for replacing lead-contained solders are near ternary eutectic Sn/Ag/Cu alloys. The electronic industry has begun to study both the process behavior and the reliability assessment of these alloys in detail to figure out their applicability to electronic devices and products. In recent publications, the solidification behavior and the fatigue life of the accelerated thermal cycle test have been reported in terms of microstructure variations such as the formation of large Ag3Sn plates and their effects. In this study, coupon type bulk specimens have been made for uniaxial tensile test by casting. To consider the effects of microstructure, casting cooling rates were controlled to 0.02-2.0 oC/sec. Eutectic Sn/Pb and near eutectic lead-free solder materials – Sn/Ag/Cu and Sn/Cu alloys – were used in mechanical testing. Also, nanoindentation tests were performed to measure Young’s modulus of materials having different microstructures. Tensile tests were performed at 3 different strain rates and then acquired 0.2% offset proof stress, ultimate tensile strength and elongation to failure.
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Müller, W. H., H. Worrack, J. Sterthaus, J. Villain, J. Wilden e A. Juritza. "How to extract continuum materials properties for (lead-free) solders from tensile tests and nanoindentation experiments". Microsystem Technologies 15, n. 1 (22 agosto 2008): 45–55. http://dx.doi.org/10.1007/s00542-008-0688-y.
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Clauß, Sebastian, Joseph Gabriel, Alexander Karbach, Mathias Matner e Peter Niemz. "Influence of the adhesive formulation on the mechanical properties and bonding performance of polyurethane prepolymers". Holzforschung 65, n. 6 (1 ottobre 2011): 835–44. http://dx.doi.org/10.1515/hf.2011.095.
Testo completoAbstract (sommario):
Abstract Only small amounts of additives are needed to formulate one-component polyurethane (1C PUR) adhesives for various applications. The current study illuminates the effects of the formulation on the mechanical properties of pure adhesives, on the one hand, and their performance in bonded wood joints on the other. Tensile shear tests on bonded wood joints, tensile tests on adhesive films, and nanoindentation measurements in the interphase region of the bond were performed. Analyses by means of infrared, atomic force, and electron microscopy provided the explanatory basis for the results obtained. Additionally to laboratory made 1C PUR, unmodified commercial 1C PUR, melamine-urea-formaldehyde (MUF), and phenol-resorcinol-formaldehyde (PRF) were tested for comparison. The results obtained confirm that the mechanical properties of 1C PUR adhesives are significantly affected by their prepolymer composition. The adhesive formulation by means of additives, on the other hand, does not affect the mechanical properties but is to a large extent responsible for the bonding performance.
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Gajowiec, Grzegorz, Michał Bartmański, Beata Majkowska-Marzec, Andrzej Zieliński, Bartosz Chmiela e Marek Derezulko. "Hydrogen Embrittlement and Oxide Layer Effect in the Cathodically Charged Zircaloy-2". Materials 13, n. 8 (18 aprile 2020): 1913. http://dx.doi.org/10.3390/ma13081913.
Testo completoAbstract (sommario):
The present paper is aimed at determining the less investigated effects of hydrogen uptake on the microstructure and the mechanical behavior of the oxidized Zircaloy-2 alloy. The specimens were oxidized and charged with hydrogen. The different oxidation temperatures and cathodic current densities were applied. The scanning electron microscopy, X-ray electron diffraction spectroscopy, hydrogen absorption assessment, tensile, and nanoindentation tests were performed. At low oxidation temperatures, an appearance of numerous hydrides and cracks, and a slight change of mechanical properties were noticed. At high-temperature oxidation, the oxide layer prevented the hydrogen deterioration of the alloy. For nonoxidized samples, charged at different current density, nanoindentation tests showed that both hardness and Young’s modulus revealed the minims at specific current value and the stepwise decrease in hardness during hydrogen desorption. The obtained results are explained by the barrier effect of the oxide layer against hydrogen uptake, softening due to the interaction of hydrogen and dislocations nucleated by indentation test, and hardening caused by the decomposition of hydrides. The last phenomena may appear together and result in hydrogen embrittlement in forms of simultaneous hydrogen-enhanced localized plasticity and delayed hydride cracking.
31
Wu, N. Q., Cedrix Xia, Ming Li, N. Perrusquia e Scott X. Mao. "Interfacial Structure and Micro and Nano-Mechanical Behavior of Laser-Welded 6061 Aluminum Alloy Blank". Journal of Engineering Materials and Technology 126, n. 1 (1 gennaio 2004): 8–13. http://dx.doi.org/10.1115/1.1631023.
Testo completoAbstract (sommario):
1 mm thick tailor-welded blank of 6061 alloy has been fabricated by Nd:YAG laser welding. The microstructure and the failure mechanism of the welded blank are investigated using optical microscope, atomic force microscope, energy dispersive spectroscopy, microindentation, and nanomechanical tester. The dendrite structure exists at the fusion zone. The partially melted zone is found near the fusion line. The tensile tests show that the welded alloy exhibits lower strength and ductility than the base alloy, and failure occurs at the partially melted zone during tensile testing. Combined nanoindentation with in-situ AFM imaging reveal that the hardness at the partially melted zone is distributed inhomogeneously on the microscopic scale. The hardness at the area adjacent to the grain boundary is lower than that at the center of grain. This is responsible for the failure upon tensile loading, and attributed to the loss of strength and ductility of the welded blank on a macroscopic scale.
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Jacob, Anaïs, e Ali Mehmanparast. "Sensitivity Analysis of Material Microstructure Effects on Predicted Crack Paths Using Finite Element Simulations". Journal of Multiscale Modelling 07, n. 02 (giugno 2016): 1650003. http://dx.doi.org/10.1142/s1756973716500037.
Testo completoAbstract (sommario):
The effects of microstructure, grain and grain boundary (GB) properties on predicted damage paths and indicative crack propagation direction have been examined for a polycrystalline material using mesoscale finite element simulations. Numerical analyses were carried out on a compact tension specimen geometry containing granular mesh structures with random grain shapes and sizes of average diameter 100[Formula: see text][Formula: see text]m. Nanoindentation tests were performed to investigate the dependency of mesoscale hardness measurements on the indentation location with respect to grain and GB regions. Finite element results have shown that under tensile loading conditions, the predicted damage paths are very sensitive to the granular mesh structure, GB properties and individual grain properties. Furthermore, finite element results have revealed that the cracking mode (i.e., transgranular/intergranular) and maximum crack deviation angle are strongly dependent on the material microstructures employed in simulations.
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Rauter, Natalie. "A computational modeling approach based on random fields for short fiber-reinforced composites with experimental verification by nanoindentation and tensile tests". Computational Mechanics 67, n. 2 (18 gennaio 2021): 699–722. http://dx.doi.org/10.1007/s00466-020-01958-3.
Testo completoAbstract (sommario):
AbstractIn this study a modeling approach for short fiber-reinforced composites is presented which allows one to consider information from the microstructure of the compound while modeling on the component level. The proposed technique is based on the determination of correlation functions by the moving window method. Using these correlation functions random fields are generated by the Karhunen–Loève expansion. Linear elastic numerical simulations are conducted on the mesoscale and component level based on the probabilistic characteristics of the microstructure derived from a two-dimensional micrograph. The experimental validation by nanoindentation on the mesoscale shows good conformity with the numerical simulations. For the numerical modeling on the component level the comparison of experimentally obtained Young’s modulus by tensile tests with numerical simulations indicate that the presented approach requires three-dimensional information of the probabilistic characteristics of the microstructure. Using this information not only the overall material properties are approximated sufficiently, but also the local distribution of the material properties shows the same trend as the results of conducted tensile tests.
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Dutta, A. K., D. Penumadu e B. Files. "Nanoindentation testing for evaluating modulus and hardness of single-walled carbon nanotube–reinforced epoxy composites". Journal of Materials Research 19, n. 1 (gennaio 2004): 158–64. http://dx.doi.org/10.1557/jmr.2004.19.1.158.
Testo completoAbstract (sommario):
Instrumented indentation testing was used to evaluate the changes in mechanical properties of single-walled carbon nanotube composite specimens with varying weight percentage (0, 0.1, 0.5, and 1.0 wt%) of nanotubes using a low-viscosity liquid epoxy resin. The nanotubes were prepared using laser ablation technique. Reference tensile tests were also performed on the same samples, and relevant comparisons with indentation results were made. The variations in modulus and hardness obtained using nanoindentation (considering time effects) showed quantifiable differences between the various composite specimens, but differed from tensile test data. The small changes in the observed stiffness and breaking strength of carbon nanotube composites was due to the formation of bundles, their curvy morphology, and microporosity in the specimens. Interesting fluctuations obtained from the interpreted values of modulus with depth of indentation is attributed to varying degrees of the local confining effect of nanotube bundles. Creep exponents for these nanocomposites were also evaluated and indicate considerable improvements.
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Her, Shiuh-Chuan, e Wei-Chun Hsu. "Strain and Temperature Sensitivities Along with Mechanical Properties of CNT Buckypaper Sensors". Sensors 20, n. 11 (28 maggio 2020): 3067. http://dx.doi.org/10.3390/s20113067.
Testo completoAbstract (sommario):
In this work, buckypaper composed of multi-walled carbon nanotubes (MWCNT) was prepared through a vacuum filtration process. The effect of MWCNT aspect ratio on the buckypaper performance was investigated. The freestanding and highly flexible buckypaper can be used as a sensor to attach on a complex surface monitoring the strain and temperature at the critical area. The mechanical properties of the buckypaper were examined using the tensile and nanoindentation tests. The strain and temperature sensitivities of the buckypaper were evaluated through the four-point bending and thermal chamber tests, respectively. In addition, the microstructure and thermal stability of the buckypaper were studied by scanning electron microscopy (SEM) and thermogravimetric analyzer (TGA), respectively. Experimental results showed that the mechanical properties such as Young’s modulus, tensile strength, fracture strain, and hardness of the buckypaper made of high aspect ratio MWCNTs were significantly superior to the buckypaper consisted of low aspect ratio MWCNTs, while the strain and temperature sensitivities of the buckypaper composed of low aspect ratio MWCNTs were better than that of the buckypaper made of high aspect ratio MWCNTs.
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Mansour, Djamel Eddine, Christoph Herzog, Petra Christöfl, Luciana Pitta Bauermann, Gernot Oreski, Andreas Schuler, Daniel Philipp e Paul Gebhardt. "Nanoindentation Reveals Crosslinking Behavior of Solar Encapsulants—The Methodological Advantages over Bulk Methods". Polymers 13, n. 19 (29 settembre 2021): 3328. http://dx.doi.org/10.3390/polym13193328.
Testo completoAbstract (sommario):
The power degradation and failure of photovoltaic (PV) modules can be caused by changes in the mechanical properties of the polymeric components during the module lifetime. This paper introduces instrumented nanoindentation as a method to investigate the mechanical properties of module materials such as polymeric encapsulants. To this end, nanoindentation tests were carried out on ethylene vinyl acetate (EVA) surfaces, which have been separated from the glass panel. Two types of time-dependent indentation cycle modes, the time domain (creep mode) and frequency domain (dynamic mode) were performed to determine the viscoelastic behavior. For each mode, a corresponding model was applied to calculate the main mechanical properties. The general capability of nanoindentation as cross-linking determination method is investigated with the methodological advantages over bulk mechanical characterization methods. A large number of Glass/EVA/Backsheet laminates were built using different lamination conditions resulting in different degrees of curing. Both indentation modes indicate good modulus sensitivity for following the EVA crosslinking in its early stages but could not reliably differentiate between samples with higher EVA branching. Additional dynamic mechanical analysis (DMA) characterization was used as an established method to validate the indentation measurements. Both nanoindentation and DMA tensile mode produce similar quantitative viscoelastic responses, in the form of the damping factor parameter, demonstrated for three different frequencies at room temperature. A statistical study of the data reveals the advantages for the investigation of multilayer PV laminates by using nanoindenation as a surface method while also being applicable to field aged modules.
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Golan, Ofek, Hila Shalom, Ifat Kaplan-Ashiri, Sidney R. Cohen, Yishay Feldman, Iddo Pinkas, Rakefet Ofek Almog, Alla Zak e Reshef Tenne. "Poly(L-lactic acid) Reinforced with Hydroxyapatite and Tungsten Disulfide Nanotubes". Polymers 13, n. 21 (8 novembre 2021): 3851. http://dx.doi.org/10.3390/polym13213851.
Testo completoAbstract (sommario):
Poly(L-lactic acid) (PLLA) is a biocompatible, biodegradable, and semi-crystalline polymer with numerous applications including food packaging, medical implants, stents, tissue engineering scaffolds, etc. Hydroxyapatite (HA) is the major component of natural bone. Conceptually, combining PLLA and HA could produce a bioceramic suitable for implants and bone repair. However, this nanocomposite suffers from poor mechanical behavior under tensile strain. In this study, films of PLLA and HA were prepared with small amounts of nontoxic WS2 nanotubes (INT-WS2). The structural aspects of the films were investigated via electron microscopy, X-ray diffraction, Raman microscopy, and infrared absorption spectroscopy. The mechanical properties were evaluated via tensile measurements, micro-hardness tests, and nanoindentation. The thermal properties were investigated via differential scanning calorimetry. The composite films exhibited improved mechanical and thermal properties compared to the films prepared from the PLLA and HA alone, which is advantageous for medical applications.
38
Samélor, D., Maelenn Aufray, Loic Lacroix, Yannick Balcaen, Joël Alexis, H. Vergnes, Dominique Poquillon et al. "Mechanical and Surface Properties of Chemical Vapor Deposited Protective Aluminium Oxide Films on TA6V Alloy". Advances in Science and Technology 66 (ottobre 2010): 66–73. http://dx.doi.org/10.4028/www.scientific.net/ast.66.66.
Testo completoAbstract (sommario):
Mechanical, barrier and surface properties of aluminium oxide films were investigated by nanoindentation, microscratch and micro tensile tests, by isothermal oxidation and voltammetry, and by contact angle measurement. The films were grown on TA6V substrates by a low pressure MOCVD process from aluminium tri-isopropoxide. Modelling of local gas flow, gas concentration and deposition rate profiles was performed using the CFD code Fluent on the basis of an apparent kinetic law. Films grown at 350 °C are amorphous AlO(OH), the one at 480 °C is amorphous Al2O3 and the one at 700 °C is nanocrystalline -Al2O3. Scratch tests and micro tensile tests resulted in adhesive failure on the two films grown at low temperature whereas cohesive failure was observed for the high temperature growth. Sample processed at 350 °C presents significantly lower oxidation kinetics in dry air than the bare substrate. Contact angle changes approximately from 100 to 50 degrees for films processed at 350-480 °C and 700 °C, respectively. Concerning the electrochemical behavior in NaCl environment, polarization curves revealed that amorphous alumina coatings improved the corrosion resistance by comparison with the others oxide films. These consolidated results reveal promising combination of properties for the films grown at different temperatures with regard to the targeted applications.
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Her, Shiuh-Chuan, e Wei-Chun Hsu. "Sensing Performance and Mechanical Properties of Buckypaper Impregnated with Epoxy Resin". Nanomaterials 10, n. 11 (14 novembre 2020): 2258. http://dx.doi.org/10.3390/nano10112258.
Testo completoAbstract (sommario):
Buckypaper consisting of a carbon nanotube (CNT) sheet has a great potential for sensing and structural applications due to the exceptional piezoresistive and mechanical properties of CNTs. In this work, buckypaper was impregnated with the epoxy resin to improve the fragility and handling capability. The mechanical properties of the buckypaper/epoxy composite were determined by the tensile and nanoindentation tests. A thermogravimetric analyzer (TGA) was used to evaluate the thermal stability. Strain and temperature sensing performances of the buckypaper/epoxy composite based on the piezoresistive effect were investigated using a meter source. Experimental results indicated that the elastic modulus and ultimate strength of the buckypaper/epoxy composite were increased by 82% and 194%, respectively, in comparison with the pristine buckypaper, while the strain and temperature sensitivities were decreased by 33% and 0.2%, respectively. A significant increase of the tensile strength accompanied with a moderate decrease of the strain sensitivity demonstrates that the overall performance of buckypaper/epoxy composite is better than that of pristine buckypaper.
40
Şevik, Hüseyin, Selma Özarslan e Hajo Dieringa. "Assessment of the Mechanical and Corrosion Properties of Mg-1Zn-0.6Ca/Diamond Nanocomposites for Biomedical Applications". Nanomaterials 12, n. 24 (9 dicembre 2022): 4399. http://dx.doi.org/10.3390/nano12244399.
Testo completoAbstract (sommario):
In this work, the microstructure, mechanical properties, and corrosion behavior of the Mg-1Zn-0.6Ca matrix alloy (ZX10), reinforced by adding various amounts of nanodiamond particles (0.5, 1, and 2 wt.%), prepared by the ultrasound-assisted stir-casting method, were investigated as they are deemed as potential implant materials in biomedical applications. Microstructure, nanoindentation, mechanical tensile, immersion, and potentiodynamic polarization tests were performed for evaluating the influence of the addition of nanodiamond particles on the alloy’s mechanical and biocorrosion properties. The results revealed that the addition of nanodiamond particles causes a reduction in the alloy’s grain size. The alloy’s nanohardness and elastic modulus values increased when the amount of added nanodiamond particles were increased. The nanocomposite with an addition of 0.5% ND showed the best composition with regard to an acceptable corrosion rate as the corrosion rates are too high with higher additions of 1 or 2% NDs. At the same time, the yield strength, tensile strength, and elongation improved slightly compared to the matrix alloy.
41
Li, Youzhi, Yongfeng Shen, Sixin Zhao, Weina Zhang e Wenying Xue. "Strengthening a Medium-Carbon Low-Alloy Steel by Nanosized Grains: The Role of Asymmetrical Rolling". Nanomaterials 13, n. 5 (6 marzo 2023): 956. http://dx.doi.org/10.3390/nano13050956.
Testo completoAbstract (sommario):
A medium-carbon low-alloy steel was prepared via the asymmetric rolling process with different ratios of upper and down roll velocities. Subsequently, the microstructure and mechanical properties were explored by using SEM, EBSD, TEM, tensile tests and nanoindentation. The results show that asymmetrical rolling (ASR) can significantly improve strength while retaining good ductility compared with conventional symmetrical rolling. The yield strength and tensile strength of the ASR-steel are 1292 ± 10 MPa and 1357 ± 10 MPa, respectively, which are higher than the values of 1113 ± 10 MPa and 1185 ± 10 MPa for the SR-steel. The ASR-steel retains good ductility of 16.5 ± 0.5%. The significant increase in strength is related to the joint actions of the ultrafine grains, dense dislocations and a large number of nanosized precipitates. This is mainly because of the introduction of extra shear stress on the edge under asymmetric rolling, which induces gradient structural changes hence increasing the density of geometrically necessary dislocations.
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Somov, Pavel A., Eugene S. Statnik, Yuliya V. Malakhova, Kirill V. Nyaza, Alexey I. Salimon, Dmitry K. Ryabov e Alexander M. Korsunsky. "On the Grain Microstructure–Mechanical Properties Relationships in Aluminium Alloy Parts Fabricated by Laser Powder Bed Fusion". Metals 11, n. 8 (24 luglio 2021): 1175. http://dx.doi.org/10.3390/met11081175.
Testo completoAbstract (sommario):
Recent years witnessed progressive broadening of the practical use of 3D-printed aluminium alloy parts, in particular for specific aerospace applications where weight saving is of great importance. Selective laser melting (SLM) is an intrinsically multi-parametric fabrication technology that offers multiple means of controlling mechanical properties (elastic moduli, yield strength, and ductility) through the control over grains size, shape, and orientation. Targeted control over mechanical properties is achieved through the tuning of 3D-printing parameters and may even obviate the need of heat treatment or mechanical post-processing. Systematic studies of grain structure for different printing orientations with the help of EBSD techniques in combination with mechanical testing at different dimensional levels are the necessary first steps to implement this agenda. Samples of 3D-printable Al-Mg-Si RS-333 alloy were fabricated in three orientations with respect to the principal build direction and the fast laser beam scanning direction. Sample structure and proper-ties were investigated using a number of techniques, including EBSD, in situ SEM tensile testing, roughness measurements, and nanoindentation. The as-printed samples were found to display strong variation in Young’s modulus values from nanoindentation (from 43 to 66 GPa) and tensile tests (from 54 to 75 GPa), yield stress and ultimate tensile strength (100–195 and 130–220 MPa) in different printing orientations, and almost constant hardness of about 0.8 GPa. A further preliminary study was conducted to assess the effect of surface finishing on the mechanical performance. Surface polishing was seen to reduce Young’s modulus and yield strength but improves ductility, whereas the influence of sandblasting was found to be more controversial. The experimental results are discussed in connection with the grain morphology and orientation.
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Hull, Katherine L., Younane N. Abousleiman, Yanhui Han, Ghaithan A. Al-Muntasheri, Peter Hosemann, S. Scott Parker e Cameron B. Howard. "Nanomechanical Characterization of the Tensile Modulus of Rupture for Kerogen-Rich Shale". SPE Journal 22, n. 04 (13 febbraio 2017): 1024–33. http://dx.doi.org/10.2118/177628-pa.
Testo completoAbstract (sommario):
Summary In the past decade, chemical, physical, and mechanical characterization of source-rock reservoirs has moved toward micro- and nanoscale testing and analyses. Nanoindentation is now widely used in many industrial and university laboratories to measure stiffness and strength as well as other mechanical properties of shales. However, to date, tensile failures of shales have not been studied at the micro- or nanoscale. In this work, a scanning electron microscope (SEM) coupled with a focused ion beam (FIB) and a special nanoindenter (NI) testing configuration (SEM-FIB-NI) is used to bring organic-rich shale samples (preserved Woodford shale from a wellsite in Ada, Oklahoma, USA) to failure in tension. Microcantilever beam geometries were milled and loaded to failure in tension while monitoring in situ with SEM. The force-displacement curves were generated while videos recording in-situ real-time displacements and failures were collected simultaneously. The microcantilever beam tests of this composite natural material demonstrate linear elastic behavior followed by elastic/plastic yield before complete failure. This behavior was clearly observed to correlate with the amount of organic matter (OM) at the fractured surface of the microcantilever beam supports. Energy-dispersive X-ray spectroscopy (EDS) analyses were conducted along the prepared microbeam samples before loading. In addition, post-failure EDS analysis was performed on the resulting fractured faces of the failed microbeams, and the correlation between tensile behavior and shale OM content was shown. Large tensile moduli of rupture, or moduli of toughness, were associated with high OM, or kerogen, present at the failed supports of the kerogen-rich-shale (KRS) microcantilever beams. The moduli of toughness as a measure of work or energy needed to bring these samples into tensile failure were ten times less when OM was missing or barely present at the support, in terms of shale microbeam volume.
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Chahrour, Mutaz K., Md Akter Hosen, Yingxin Goh, Teong Yen Tong, Soon Poh Yap e Mohamed Amine Khadimallah. "Failure Mechanisms of Structural Bamboo Using Microstructural Analyses". Advances in Materials Science and Engineering 2021 (20 dicembre 2021): 1–10. http://dx.doi.org/10.1155/2021/1571905.
Testo completoAbstract (sommario):
Bamboo is deemed an emerging constructional material with promising application projections due to the reliable natural properties and advantageous structural characteristics. However, there is a lack of systematic studies on the mechanical characteristics of the bamboo species from a microstructural scale. Hence, this paper investigated the primary mechanical properties of the bamboo specimens (Dendrocalamus asper) with further microstructural analysis on the bamboo failure. The direct tensile strength of bamboo specimens was about 226.45 MPa, while the final splitting tensile modulus was found to be 2.88 MPa. Microstructural characterisation of the failed tensile specimens indicates that fibre debonding is the main failure mechanism under tensile conditions. On the other hand, splitting and end bearing failure were found on compression test specimens. In addition, nanoindentation tests were carried out on different cell structures to articulate the hardness and Young’s modulus. The elastic modulus of the fibre cell walls is three times that of the parenchyma cell walls, yet the hardness values are comparable. This confirms that the specimen failure of previous macromechanical testing is due to crack propagation along the parenchyma cells, instead of the cell walls. Based on the experimental studies discussed in this paper, the conclusion can convey a positive message regarding the ability of bamboo as a primary sustainable substitute for conventional construction materials.
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Zou, Y., L. F. Ge, Z. Y. Li, J. W. Guo, W. Zhu e Z. S. Ma. "Determination of the intrinsic elastic modulus, hardness and fracture strength of thermally growth oxide by nanoindentation and tensile tests". Engineering Failure Analysis 131 (gennaio 2022): 105815. http://dx.doi.org/10.1016/j.engfailanal.2021.105815.
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Mishra, Pragya, Pia Åkerfeldt, Farnoosh Forouzan, Fredrik Svahn, Yuan Zhong, Zhijian Shen e Marta-Lena Antti. "Microstructural Characterization and Mechanical Properties of L-PBF Processed 316 L at Cryogenic Temperature". Materials 14, n. 19 (6 ottobre 2021): 5856. http://dx.doi.org/10.3390/ma14195856.
Testo completoAbstract (sommario):
Laser powder bed fusion (L-PBF) has attracted great interest in the aerospace and medical sectors because it can produce complex and lightweight parts with high accuracy. Austenitic stainless steel alloy 316 L is widely used in many applications due to its good mechanical properties and high corrosion resistance over a wide temperature range. In this study, L-PBF-processed 316 L was investigated for its suitability in aerospace applications at cryogenic service temperatures and the behavior at cryogenic temperature was compared with room temperature to understand the properties and microstructural changes within this temperature range. Tensile tests were performed at room temperature and at −196 °C to study the mechanical performance and phase changes. The microstructure and fracture surfaces were characterized using scanning electron microscopy, and the phases were analyzed by X-ray diffraction. The results showed a significant increase in the strength of 316 L at −196 °C, while its ductility remained at an acceptable level. The results indicated the formation of ε and α martensite during cryogenic testing, which explained the increase in strength. Nanoindentation revealed different hardness values, indicating the different mechanical properties of austenite (γ), strained austenite, body-centered cubic martensite (α), and hexagonal close-packed martensite (ε) formed during the tensile tests due to mechanical deformation.
47
Jiang, Chun Yu, Xiao Xiao Tian e Guo Dong Shi. "Microstructure and Mechanical Properties of Tough Phase Layers of a NiCoCrAl/YSZ Multiscalar Microlaminate". Advanced Materials Research 1089 (gennaio 2015): 15–19. http://dx.doi.org/10.4028/www.scientific.net/amr.1089.15.
Testo completoAbstract (sommario):
One multiscalar microlaminate comprising 66 thin strong layer stacks of NiCoCrAl / ZrO2-8wt.%Y2O3 (YSZ) and 5 thick tough phase layers of NiCoCrAl whose thicknesses ranged from 5μm to 25μm was fabricated by Electron Beam Physical Vapor Deposition (EB-PVD) and followed by hot pressing treatment. Scanning electron microscopy was used to characterize the microstructures and failure mode of the tough phase layers. Tensile tests and nanoindentation tests were performed to evaluate the mechanical properties of the tough phase layers. The influence of thicknesses of tough phase layers on their microstructure and mechanical properties was investigated. It was found that with the increasing thicknesses of the tough phase layers, their hardness decreased, but their plasticity increased. There was a critical thickness for the tough phase layers between 13μm and 20μm. The tough phase layers with thickness less than the critical value displayed the different microstructure and failure mode from those with thickness more than the critical value.
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Carneiro, Íris, e Sónia Simões. "Investigation of Mechanical Properties of Al/CNT Nanocomposites Produced by Powder Metallurgy". Applied Sciences 13, n. 1 (21 dicembre 2022): 54. http://dx.doi.org/10.3390/app13010054.
Testo completoAbstract (sommario):
Demanding requirements in automotive and aerospace applications promote the growing need to obtain materials and advanced technology capable of combining low weight with high mechanical properties. Aluminum matrix nanocomposites could be great candidates to respond to such needs. In this sense, this investigation aims to study the mechanical properties of nanocomposites of aluminum matrices reinforced with carbon nanotubes (CNTs). The nanocomposites were produced by powder metallurgy with 1.00 vol.% of reinforcement and ultrasonication as the dispersion method. Tensile, Vickers microhardness and nanoindentation tests were carried out in different sections. Microstructural characterizations were conducted in scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD) to understand and relate to the mechanical properties. An increase in the yield strength of 185% was observed for the nanocomposites, which can be attributed to the load transfer mechanism. However, the CNTs observed at the grain boundaries promote a decrease in the ductility of the nanocomposites. The mechanical behavior of the nanocomposites was further investigated by EBSD observation. The results revealed that the nanocomposites have a less extensive area of plastic deformation than the Al matrix, which is consistent with the tensile results. The presence of reinforcement affects the lattice rotation during the tensile test and the active slip systems, thus affecting their deformation behavior.
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Yan, Xiang, Yiming Wu, Minghe Zhang, Songsong Liu, Lihui Sun e Yunli Feng. "Microstructure Evolution and Mechanical Properties of Ferrite–Austenite Duplex Fe-Mn-Al-(Cu)-C Steel under Different Annealing Temperatures". Materials 15, n. 22 (21 novembre 2022): 8271. http://dx.doi.org/10.3390/ma15228271.
Testo completoAbstract (sommario):
The effect of Cu addition and the intercritical annealing (IA) temperature on the microstructural evolution and mechanical properties of Fe-0.4C-7Mn-4Al (wt%) was investigated via scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), X-ray diffraction (XRD) and nanoindentation tests. The results showed that the volume fraction and the average grain size of austenite, and the fraction of high angle grain boundaries, increased with IA temperature increase in the range of 650 °C to 710 °C. The addition of Cu facilitates the formation of Cu-rich nanoparticles, raises the volume fraction of austenite, and delays the recrystallization of austenite. As IA temperature increased, the yield strength (YS), ultimate tensile strength (UTS), and Lüders bands strain (LBS) decreased in both experimental steels. The Cu addition not only increases the YS of medium Mn steel but also benefits the decrease of LBS. The best comprehensive mechanical properties were obtained at the IA temperature of 690 °C in the studied steel, with Cu addition. According to nanoindentation experiments, the Cu addition raises the hardness of ferrite and austenite from 4.7 GPa to 6.3 GPa and 7.4 GPa to 8.5 GPa, respectively, contributing to the increase of YS of medium-Mn steel.
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Isaza M, Cesar A., JE Ledezma Sillas, JM Meza e JM Herrera Ramírez. "Mechanical properties and interfacial phenomena in aluminum reinforced with carbon nanotubes manufactured by the sandwich technique". Journal of Composite Materials 51, n. 11 (13 luglio 2016): 1619–29. http://dx.doi.org/10.1177/0021998316658784.
Testo completoAbstract (sommario):
Recently, a new manufacturing process for the production of metallic matrix composite materials reinforced with carbon nanotubes, known as sandwich technique has been proposed. This technique produces a material comprised of a metallic matrix and a banded structures-layers of multi-walled carbon nanotubes. However, among other issues, the matrix-reinforcement interface and the reinforcement dispersion degree are still open questions. The present study uses field emission scanning electron microscopy and high resolution transmission electron microscopy to probe that the method is capable to achieve a good dispersion of the multi-walled carbon nanotubes with no evidence of carbon nanotubes’ damage. The mechanical properties were measured by tensile and nanoindentation tests; improvements in the elastic modulus, yield and ultimate strengths were found, with respect to the unreinforced material.