Articoli di riviste: "Miniaturized specimen"

1

Samal, MK, KS Balakrishnan, J. Parashar, GP Tiwari e S. Anantharaman. "Estimation of transverse tensile behavior of Zircaloy pressure tubes using ring-tensile test and finite element analysis". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 227, n. 6 (13 settembre 2012): 1177–86. http://dx.doi.org/10.1177/0954406212460474.

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Determination of transverse mechanical properties from the ring type of specimens directly machined from the nuclear reactor pressure tubes is not straightforward. It is due to the presence of combined membrane as well as bending stresses arising in the loaded condition because of the curvature of the specimen. These tubes are manufactured through a complicated process of pilgering and heat treatment and hence, the transverse properties need to be determined in the as-manufactured condition. It may not also be possible to machine small miniaturized specimen in the circumferential direction especially in the irradiated condition. In this work, we have performed ring-tensile tests on the un-irradiated ring tensile specimen using two split semi-cylindrical mandrels as the loading device. A three-dimensional finite element analysis was performed in order to determine the material true stress–strain curve by comparing experimental load–displacement data with those predicted by finite element analysis. In order to validate the methodology, miniaturized tensile specimens were machined from these tubes and tested. It was observed that the stress–strain data as obtained from ring tensile specimen could describe the load–displacement curve of the miniaturized flat tensile specimen very well. However, it was noted that the engineering stress–strain as directly obtained from the experimental load–displacement curves of the ring tensile tests were very different from that of the miniaturized specimen. This important aspect has been resolved in this work through the use of an innovative type of 3-piece loading mandrel.

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Zhu, Zhikang, Zheng Lu, Peng Zhang, Wei Fu, Changyu Zhou e Xiaohua He. "Optimal Design of a Miniaturized Cruciform Specimen for Biaxial Testing of TA2 Alloys". Metals 9, n. 8 (25 luglio 2019): 823. http://dx.doi.org/10.3390/met9080823.

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The biaxial tensile testing of cruciform specimens is an effective way to create complex loading, and is a feasible experimental method for studying the subsequent yield behavior. However, relevant knowledge gaps still exist in the geometric design of miniaturized cruciform specimens which are applicable to test machines with maximum load less than 5000 N. The present work outlines the systematic investigations of the optimal design of the miniaturized cruciform specimen of a commercial pure titanium TA2 for biaxial tensile testing. Finite element modeling (FEM) coupled with the orthogonal design is employed to explore the influence of various geometric parameters, i.e., the thickness of the central gauge region, the width, the length, and the number of the slit, and the radius of the inner chamfer, on the stress distribution of the central gauge region. The optimal geometric design of the miniaturized cruciform specimen is successfully obtained, simultaneously considering the stress uniformity in the central gauge region and economic factors. The full-field strain distributions are also determined via the digital image correction (DIC) technique, which confirm the accuracy of the results achieved from FEM. This work provides a complete and reliable procedure for optimizing the geometry of miniaturized cruciform specimens, whose application can be expanded to other metals in the future.

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Rubešová, Kateřina, Martin Rund, Sylwia Rzepa, Hana Jirková, Štěpán Jeníček, Miroslav Urbánek, Ludmila Kučerová e Pavel Konopík. "Determining Forming Limit Diagrams Using Sub-Sized Specimen Geometry and Comparing FLD Evaluation Methods". Metals 11, n. 3 (14 marzo 2021): 484. http://dx.doi.org/10.3390/met11030484.

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Sheet metal forming boundaries are established using the forming limit diagram (FLD). The Nakajima and Marciniak tests, which are based on stretching a material using a punch, are the most commonly used methods for determining the FLD or fracture forming limit diagram (FFLD). The results are usually evaluated by calculating local strain, strain rates, specimen thickness reduction or fracture strain. When the amount of experimental material is insufficient, miniaturization of the testing specimens may be a solution. However, the interchangeability of the results for standard and miniaturized specimens has not been proven yet. In this study, the Nakajima tests were performed using standard and sub-sized specimens made of manganese–boron steel 22MnB5, commonly used in the automotive industry. Afterwards, four FLD/FFLD evaluation methods were applied and compared. The miniaturized specimens yielded higher strain values, which was explained by the varied ratio of material thickness/punch diameter and different bending conditions. The highest compliance of the results was recorded for the standard and miniaturized FFLD.

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Spisak, Bernadett, Zoltán Bézi, Réka Erdei e Szabolcs Szávai. "Modelling of crack propagation in miniaturized and normal SENB specimens based on local failure criterion". Frattura ed Integrità Strutturale 18, n. 68 (27 febbraio 2024): 296–309. http://dx.doi.org/10.3221/igf-esis.68.20.

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The use of miniaturized specimen testing methods is a promising way to solve the problem of limited materials in RPV monitoring programs. The use of miniature specimens allows the evaluation of fracture toughness from other specimen materials used. In particular, the small-size compact tensile test specimen (0.16T CT) is promising for the determination of fracture toughness, as it can be produced from the standard size Charpy specimen that has already been tested. However, if we have only 0.16T CT test, we cannot investigate the dimensional response and also have only one restricted deformation state, which may pose problems in verifying geometry independence and determining local parameters for state-of-the-art analyses. It is therefore recommended to prepare at least two tests with two different restricted deformation specimens. Therefore, the testing of mini single edge notched bending (SENB) is also required and can be worked out from the Charpy specimens. The paper presents the determination of fracture toughness for these miniaturized specimens by modifying the virtual crack closure technique (VCCT) simulation method using GTN parameters instead of energy release as the driving force. This allows the calculation of the J-integral to proceed in parallel with the crack propagation.

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Cruz, Daniel J., Jose Xavier, Rui L. Amaral e Abel D. Santos. "A Miniaturized Device Coupled with Digital Image Correlation for Mechanical Testing". Micromachines 13, n. 11 (19 novembre 2022): 2027. http://dx.doi.org/10.3390/mi13112027.

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Miniaturized mechanical testing based on small sample testing technology is a powerful technique to characterize the mechanical properties of different materials, and it is being used in different application fields. However, the small size of the specimens poses several challenges because the results are highly sensitive to measurement accuracy and the corresponding mechanical properties can change substantially due to the so-called specimen size effect. In this work, a novel testing device based on miniaturized specimens is presented. The equipment is designed to test materials in tensile and compressive loadings, but it is also capable of performing reverse-loading tests. Buckling of the specimen is an inherent phenomenon in compression loadings, especially for thin materials. Therefore, specimen geometry is properly studied and optimized to mitigate this effect. To evaluate the deformation of the specimen, the digital image correlation (DIC) technique is used to capture the full-field strain in the central gauge section of the sample. A sensitivity analysis of the DIC setting parameters was performed for this application. To evaluate the performance of the developed system, experimental results of monotonic tests and tests with reverse loadings (tension-compression) are presented, considering two high-strength steels (DP500 and DP780).

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Yu, Bintao, Wentuo Han, Zhenfeng Tong, Diancheng Geng, Chenlong Wang, Yingchao Zhao e Wen Yang. "Application of Small Specimen Test Technique to Evaluate Creep Behavior of Austenitic Stainless Steel". Materials 12, n. 16 (9 agosto 2019): 2541. http://dx.doi.org/10.3390/ma12162541.

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Small specimen test techniques (SSTT) are highly demanded in the nuclear field. In the present work, SSTT was applied to the creep tests of 15-15Ti austenitic steel. The creep behaviors of specimens with miniaturized and standard sizes were contrastively studied. The feasibility of SSTT is verified after tests under more than 20 creep conditions. The results that were obtained by miniaturized specimens are relatively conservative and they can be securely applied. The stress exponent and apparent activation creep energy of 15-15Ti are calculated as 7.7 and 428 kJ/mol, respectively. The creep microstructures are characterized by the evolution of dislocations, deformation twins, and precipitates.

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Mao, Xingyuan. "Fracture Toughness JIC Prediction From Super-Small Specimens (0.2CT, 0.5MM Thick) of a Martensitic Stainless Steel HT-9". Journal of Engineering Materials and Technology 113, n. 1 (1 gennaio 1991): 135–40. http://dx.doi.org/10.1115/1.2903369.

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The fracture toughness of alloy HT-9, a martensitic stainless steel under consideration for fusion reactor applications, was determined from 0.2CT (0.5mm thick) specimens. Specimens with thicknesses of 25 (1CT), 10 (0.4CT), 3 and 0.5 (0.2CT)mm were tested to investigate the effects of specimen size on fracture toughness. 0.2CT (0.5mm thick) specimens did not satisfy ASTM E813 size requirements for a valid JIc. Fractographic examinations of the variation of stretch zone width and fracture modes along the specimen thickness were performed by scanning electron microscopy (SEM), where flat and shear fracture regions had been distinguished. A new JIc evaluation procedure for invalid specimen size is proposed using rigid plastic analysis and shear fracture measurements with fractographic observations. Predicted JIc values were compared with the JIc values obtained from valid specimen sizes. This miniaturized specimen technique may be applicable to post-irradiation fracture toughness testing.

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Konishi, Yutaka, Takamoto Itoh, Masao Sakane, Fumio Ogawa e Hideyuki Kanayama. "Low Cycle Fatigue Test of Lead Free Solders Using Small Sized Specimen". Key Engineering Materials 734 (aprile 2017): 194–201. http://dx.doi.org/10.4028/www.scientific.net/kem.734.194.

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This paper investigates the fatigue results in low cycle fatigue region obtained from a miniaturized specimen having a 6mm gage length, 3mm diameter and 55mm total length. Fatigue tests were performed for two type lead-free solders using horizontal-type electrical servo hydraulic push-pull fatigue testing machine. Materials employed were Sn-3.0Ag-0.5Cu and Sn-5Sb. The results from Sn-3.0Ag-0.5Cu were compared with those obtained using a bulk specimen in a previous study. Relationship between strain range and number of cycles to failure of the small-sized specimen agreed with those of the bulk specimens. The testing techniques are applicable to Sn-5Sb following the Manson-Coffin law. These results confirm that the testing technique proposed here, using small-sized specimen, is suitable to get fruitful fatigue data for lead-free solder compounds.

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Lin, Yun, Wen Yang, Zhen Feng Tong e Guang Sheng Ning. "Fracture Toughness Analysis of the China RPV Steel with Miniaturized Specimen". Materials Science Forum 850 (marzo 2016): 41–46. http://dx.doi.org/10.4028/www.scientific.net/msf.850.41.

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Reactor pressurized vessel (RPV), which determines the lifetime of the nuclear power plant (NPP), is mainly forged using A508-3 steel in China. In order to meet the requirement of the small specimen test technique in the nuclear application, the fracture toughness of A508-3 steel was tested under-100°C using 1/4 CT specimens, and analyzed using Master Curve according to ASTM E 1921. In this work, the relationship of the KIC and the distance between the cleavage crack initiation site and the front of the fatigue crack is studied, and the transition temperature T0 of A508-3 is-98.7 oC, which is quite close to the test temperature.

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Miwa, Y., S. Jitsukawa e A. Hishinuma. "Development of a miniaturized hour-glass shaped fatigue specimen". Journal of Nuclear Materials 258-263 (ottobre 1998): 457–61. http://dx.doi.org/10.1016/s0022-3115(98)00306-7.

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Schwenk, Jochen M., Oliver Poetz, Robert Zeillinger e Thomas O. Joos. "A Miniaturized Ligand Binding Assay for EGFR". International Journal of Proteomics 2012 (8 aprile 2012): 1–5. http://dx.doi.org/10.1155/2012/247059.

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In order to study receptor abundance and its function in solutions or in homogenates from clinical specimen, methods such as sandwich or radioimmunoassays are most commonly employed. For the determination of epidermal growth factor receptor (EGFR), we describe the development of a miniaturized bead-based ligand binding assay using its ligand EGF as immobilized capture reagent. This assay was used to analyze lysates from cell lines, and the ligand-bound EGFR was detected using an EGFR-specific antibody combined with a fluorescence-based reporter system. In a proof-of concept study with lysates from breast biopsies, the assay allowed to classify breast cancer samples in accordance to clinically the relevant EGFR cut-off level. The study suggests that such a ligand binding receptor assay could become an integral part of protein profiling procedures to provide additional information about receptor functionality in addition to its abundance.

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Ma, Yan, Yan Ze Xu, Shu Yu Zhang e Chen Lin Lu. "Evaluation of Mechanical Properties of Hastelloy C-276 Weld by Small Punch Test". Advanced Materials Research 941-944 (giugno 2014): 1483–87. http://dx.doi.org/10.4028/www.scientific.net/amr.941-944.1483.

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Mechanical properties of the electron beam weld zone, which are different from the base metal, of Hastelloy C-276 were studied by small punch test (SPT) technology. Load–displacement curves and material properties were obtained by using miniaturized plate-type specimens (3mm diameter×(0.15-0.4) mm thick) from the weld and base metal respectively. The result shows that the maximum load of weld is larger than that of the base metal under the same thickness, meaning the higher strength of the weld. Furthermore, finite element method analysis was performed to investigate the effects of specimen thickness, the diameter of loading ball and the diameter of center hole in holder on the plastic damage of Hastelloy C-276.

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KIM, BUMJOON, BYEONGSOO LIM e DONGHYUN KI. "CREEP BEHAVIOR AND LIFE EVALUATION OF AGED P92 STEEL". International Journal of Modern Physics B 20, n. 25n27 (30 ottobre 2006): 4231–36. http://dx.doi.org/10.1142/s0217979206041148.

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Creep strength and life of material is closely related with the microstructural characteristics. Components used under creep condition for long time are unable to maintain the stability of microstructure and experience degradation of material. From this viewpoint, it is necessary for safety and residual life of power plant to investigate creep properties of specimens prepared from the material cut directly from the operating service components. The small punch test has been developed as a useful method to estimate mechanical properties because of its miniaturized specimen size. In this study, small punch creep tests were carried out to investigate the effect of aging time on creep properties using P92 steel aged from 0~12100 hrs at 600°C.

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Serizawa, Hisashi, e Hidekazu Murakawa. "A Critical Review on Modeling of Fracture Behavior of Ceramic Joints". Advances in Science and Technology 88 (ottobre 2014): 121–30. http://dx.doi.org/10.4028/www.scientific.net/ast.88.121.

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As examples of the most typical methods to determine the shear strength of SiC/SiC composite joints, the asymmetrical four point bending test of a butt-joined composite, the tensile test of a lap-joined composite, and the compression test of a double-notched composite joint were analyzed by using a finite element method with the interface element. From the results, it was found that the shear strength in the asymmetrical bending test was controlled by both the surface energy and the shear strength at the interface regardless of their combination while the strength in the tensile test or the compression test was governed by the surface energy when both the surface energy and the shear strength were large. In addition, the interface element was employed in order to examine the influence of the specimen geometry on the microstructural fracture morphology in nanoSiC/SiC composite during a miniaturized Double Notch Shear (DNS) test. From the serial computations, it is revealed that a relationship between the inter-laminar shear strength and the yield stress seems to be very important for selecting appropriate specimen geometry of the miniaturized DNS test.

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Wolfenden, A., XY Mao, T. Shoji e H. Takahashi. "Development of a Miniaturized Specimen Technique for Fracture Toughness JIc Measurement". Journal of Testing and Evaluation 16, n. 2 (1988): 229. http://dx.doi.org/10.1520/jte11166j.

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Jelinek, Alexander, Stanislav Zak, Megan J. Cordill, Daniel Kiener e Markus Alfreider. "Nanoscale printed tunable specimen geometry enables high-throughput miniaturized fracture testing". Materials & Design 234 (ottobre 2023): 112329. http://dx.doi.org/10.1016/j.matdes.2023.112329.

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Hoefnagels, J. P. M., P. J. M. Janssen, T. H. de Keijser e M. G. D. Geers. "First-Order Size Effects in the Mechanics of Miniaturized Components". Applied Mechanics and Materials 13-14 (luglio 2008): 183–92. http://dx.doi.org/10.4028/www.scientific.net/amm.13-14.183.

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This work analyses those size effects that are encountered first upon downscaling, including grain boundary effects, free surface effects, grain statistics effects. The separate influence of first-order effects was carefully investigated from uniaxial tensile tests on high-purity aluminum specimens with a well-defined microstructure of through-thickness grains, whereby the total number of grains in the cross-section was reduced towards a single grain in a cross-section by, first, decreasing the film thickness and, second, for specimens with through-thickness grains decreasing the specimen width. In addition, 3D dislocation-field strain gradient plasticity simulations were employed to analyze the intrinsic size effects, using the grain size and texture as measured experimentally. The work shows that for miniaturized structures with a limited number of columnar grains a unique Hall-Petch relation does not exist, even though a grain boundary effect, i.e. a decrease in stress level (at a given strain) for decreasing grain boundary area per unit volume, is clearly present. When the microstructure is kept constant upon miniaturization, the free surface per unit area increases causing the stress level of the structure to decrease, the effect of which increases towards a single grain in the cross-section. In addition, the work shows that grain statistics effects also contribute to observed weakening, due to insufficient compensation of local (weaker) material properties by the surrounding material (i.e. grains). Finally, grain statistics also significantly increase the statistical variation in mechanical properties for small-sized structures, an effect that is especially important for the reliability of miniature components. The separate influence of these first-order effects as well as their interplay are explained in terms of the movement of the dislocations upon plastic flow.

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Zielke, H., Martin Abendroth e Meinhard Kuna. "Determination of Fracture Mechanical Properties of Carbon Bonded Alumina Using Miniaturized Specimens". Key Engineering Materials 713 (settembre 2016): 70–73. http://dx.doi.org/10.4028/www.scientific.net/kem.713.70.

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Open cell ceramic foam filters are utilized to reduce non-metallic inclusions during casting of metals and therefore to enhance the quality of cast parts. A new generation of multifunctional filters made of carbon bonded alumina (Al2O3-C) has been developed within the scope of the collaborative research center CRC 920 [1]. The assessment of the resistance against high thermal and mechanical loads requires a mechanical characterization of the ceramic filter material. The mechanical properties show a distinctive size dependency, that’s why the specimen dimensions should be similar to the strut size of the real filter structures. The tensile fracture behavior is investigated by means of the Small Punch Test (SPT) using miniaturized disk-shaped specimens. During the mechanical tests a load-displacement curve is measured until failure occurs and a fracture stress is calculated from the experimental results. An estimation about the failure probability by means of Weibull statistics is performed because of the large scatter of the strength of the material. Furthermore, a modified version of the SPT, the so called Ball On Three Balls Test (B3B), is applied and compared to the SPT. In a final step numerical simulations of the B3B tests are performed by means of the finite element method to identify fracture mechanical material parameters like the fracture toughness.

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Liew, Li-Anne, David T. Read e Nicholas Barbosa. "Fatigue testing of bulk materials using a microsystems based approach". Additional Conferences (Device Packaging, HiTEC, HiTEN, and CICMT) 2014, DPC (1 gennaio 2014): 000632–64. http://dx.doi.org/10.4071/2014dpc-ta34.

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Fatigue, the degradation of a material's mechanical properties due to cyclic loading, is a critical issue limiting the reliability of structural materials[1]. Fatigue testing of materials is typically carried out in controlled laboratory conditions on specially prepared specimens, and the results are extrapolated to real world conditions. In the past two decades, conventional fatigue testing machines and specimens have undergone miniaturization for the purpose of evaluating the fatigue properties of miniaturized mechanical components such as sensors and biomedical implants, with the smallest test specimens having dimensions on the order of 1 mm length [2] or consisting of foils and wires [3]. Challenges with miniaturization include difficulty in specimen handling, gripping, and alignment. At the same time, MEMS technology has been used to fabricate the actuators and sensors for fatigue testing of thin films [4]. In this approach, the specimen is typically part of the MEMS actuator and is fabricated in-situ. While this eliminates the problems with specimen gripping and alignment, it limits the specimen materials to those from which MEMS actuators and sensors can be readily fabricated, is destructive to the MEMs device, and furthermore is typically limited to thin films. We seek to use the advantages of MEMS to study the fatigue properties of bulk materials rather than thin films, but at the micrometer scale. This allows for greater accuracy and spatial resolution, compared to the state of the art, of property measurements of structural materials such as aluminum and stainless steel alloys as well as other materials used in civil infrastructure, aerospace, transportation and energy industries. Our approach is to use MEMS as chip-scale re-useable test instruments into which small specimens cut from bulk materials can be inserted and tested [5]. We describe the design of the MEMS test instrument and the metal foil specimen, whose gage section was 135 um wide and 25 um thick. The test instrument was fabricated from silicon and glass wafers, and the specimens were etched from commercially available Al 1145 H19 foil. Our S-N curve agrees within expectation with published values for similar aluminum alloys tested using conventional methods at much larger specimen size scales, and the fracture surface shows distinct regions corresponding to slow and fast crack growth. We envision this test technique as a tool to further the study of the fatigue properties of structural materials.

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Meshii, Toshiyuki, Teruhiro Yamaguchi e Yuma Higashino. "Applicability of the Modified Ritchie-Knott-Rice Failure Criterion to Examine the Feasibility of Miniaturized Charpy Type SE(B) Specimens". Advances in Materials Science and Engineering 2016 (2016): 1–12. http://dx.doi.org/10.1155/2016/3728035.

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This paper examined whether the modified Ritchie-Knott-Rice (RKR) failure criterion can be applied to examine the feasibility of miniaturized Charpy type SE(B) specimens of thickness-to-width ratio B/W=1. The modified RKR failure criterion considered in this paper is the (4δt,σ22c) criterion which predicts the onset of cleavage fracture when the midplane crack-opening stress measured at a distance equal to four times the crack-tip opening displacement, denoted as σ22d, exceeds a critical stress σ22c. Specimens with B values of 25, 10, 3, and 2 mm (denoted as 25t, 10t, 3t, and 2t specimens, resp.) manufactured with 0.55% carbon steel were tested at 20°C. The results showed that the modified RKR criterion could appropriately predict the occurrence of cleavage fracture accompanied by negligibly small stable crack extension (denoted as KJc fracture) naturally for the 25t and 10t specimens. The modified RKR criterion could also predict that KJc fracture does not occur for the 2t specimen. The σ22c obtained from specimens for the 25t and 10t specimens exhibited only a small difference, indicating that the Jc obtained from the 10t specimens can be used to predict the Jc that will be obtained with the 25t specimens.

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Han, A. Ruem, Hye Jin Lee, Nak Kyu Lee, Geun An Lee e Jung Han Song. "Micro Mechanical Property Measurement of Nickel (99.9%) Thin Film Using Vision Strain Measuring Method". Materials Science Forum 620-622 (aprile 2009): 69–72. http://dx.doi.org/10.4028/www.scientific.net/msf.620-622.69.

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Mechanical properties of micro-electro-mechanical systems (MEMS) materials are increasingly important with the wide use of miniaturized systems. This paper deals with development of the strain measurement module for micro materials tests. Vision strain method (VSM) and actuating stroke method (ASM) are adopted in the strain measurement module in order to reduce the discrepancies between the measured deformation and actual one in the specimen. With the developed strain measurement system, a number of tensile tests were concluded for 99.9% nickel thin films with the thickness of 500µm. Specimens with various widths from 1 mm to 2mm and with various lengths from 2mm to 4mm were used in the tests. From the experiment, material properties such as yield strength, tensile strength, fracture strength, fracture strain and young’s modulus are analyzed with stress-strain curves of 99.9% nickel thin film.

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Guan, Wei, Aiden Lockwood, Beverley J. Inkson e Günter Möbus. "A Piezoelectric Goniometer Inside a Transmission Electron Microscope Goniometer". Microscopy and Microanalysis 17, n. 5 (13 settembre 2011): 827–33. http://dx.doi.org/10.1017/s143192761100050x.

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AbstractPiezoelectric nanoactuators, which can provide extremely stable and reproducible positioning, are rapidly becoming the dominant means for position control in transmission electron microscopy. Here we present a second-generation miniature goniometric nanomanipulation system, which is fully piezo-actuated with ultrafine step size for translation and rotation, programmable, and can be fitted inside a hollowed standard specimen holder for a transmission electron microscope (TEM). The movement range of this miniaturized drive is composed of seven degrees of freedom: three fine translational movements (X,Y, andZaxes), three coarse translational movements along all three axes, and one rotational movement around theX-axis with an integrated angular sensor providing absolute rotation feedback. The new piezoelectric system independently operates as a goniometer inside the TEM goniometer.In situexperiments, such as tomographic tilt without missing wedge and differential tilt between two specimens, are demonstrated.

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Nahm, Seung Hoon, Amkee Kim e Jonghwa Park. "Evaluation on toughness degradation of Cr–Mo–V steel using miniaturized impact specimen technology". International Journal of Impact Engineering 25, n. 8 (settembre 2001): 805–16. http://dx.doi.org/10.1016/s0734-743x(01)00006-9.

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Bergonzi, Lorenzo, Matteo Vettori e Alessandro Pirondi. "Development of a miniaturized specimen to perform uniaxial tensile tests on high performance materials". Procedia Structural Integrity 24 (2019): 213–24. http://dx.doi.org/10.1016/j.prostr.2020.02.018.

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Liew, Li-Anne, David T. Read e Nicholas Barbosa. "Bend testing of micro-scale bulk metal specimens using a chip-scale test instrument". Additional Conferences (Device Packaging, HiTEC, HiTEN, and CICMT) 2015, DPC (1 gennaio 2015): 000827–64. http://dx.doi.org/10.4071/2015dpc-tp36.

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We describe bend testing on micro-scale specimens of 302 stainless steel, using a MEMS test instrument. Bend testing is a common way of measuring the flexural stiffness of structural materials across many size scales, from thin laminate sheets to large weldments. Whereas the stiffness of a material under tensile loading is given by the Young's Modulus, the flexural stiffness, or the stiffness in bending, is much lower. In the past two decades, conventional materials testing machines and the specimens themselves have undergone miniaturization for the purpose of evaluating the mechanical properties of miniaturized mechanical components such as sensors and biomedical implants, for which the smallest specimen dimension is typically around 1 mm [2]. Another driver for miniaturizing the testing apparatuses is to test materials with inherently small form factors such as wires and thin films [3]. Now the emerging 3D printing technology is creating another need for material property measurement at micrometer size scales, to accurately capture the property gradients resulting from the layered manufacturing. However, with ever increasing miniaturization comes increasing difficulty in specimen handling, gripping, and alignment. Concurrently, MEMS technology has been used over the past 2 decades to fabricate small actuators and sensors for mechanical testing of materials of thin films [4] or nanoscale materials such as nanowires. We seek to use the advantages of MEMS to study the mechanical properties of bulk materials rather than thin films, but at the micrometer scale. We believe this will result in greater accuracy and spatial resolution of property measurements of structural materials used in civil infrastructure, aerospace, transportation and energy industries, as well as characterizing manufacturing processes that lead to steep property gradients such as 3D printed components. Our approach is to use MEMS actuators as chip-scale re-useable test instruments into which small specimens sectioned from bulk materials can be inserted and tested [5], to reduce the cost and time to obtain large data sets and to allow the measurements to be done in-situ in harsh environments. We will describe the design of a micro-size 302 stainless steel specimen, and the use of a MEMS test instrument for performing the bend testing on the specimens. The specimen's gage section was 350 um long, 65 um wide and 25 um thick, and was made by lithographic etching of a foil. The MEMS test instrument was fabricated from silicon and glass wafers. The specimens were inserted into the MEMS test chip and the silicon actuator applied static bending loads to the specimen. Displacements were measured from optical microscope images, and the force was calculated from the applied voltage and the known (measured) stiffness of the silicon actuator. The applied force from the MEMS actuator was measured directly, without any specimen, using a custom table-top force probe and load cell apparatus, and was in agreement with the force calculated from the applied voltage. The flexural stiffness of the micro specimens were measured, using the MEMS test device, at 90 – 130 N/m. These values were validated by independently testing the specimens with the much larger table-top force probe. We thus show that our MEMS test chip can be used to perform bending tests on micro scale specimens of bulk materials, but with a 1000-fold reduction in size compared to table-top force-measuring apparatuses.

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Brackett, J., B. Durley, R. Janczak, V. Kazlauskas, J. Kmiec, J. Norlie, R. Rosencranz, S. Schultz, T. Spring e W. Theusch. "Centrifugal ion-selective electrode system for potassium in whole blood". Clinical Chemistry 36, n. 12 (1 dicembre 1990): 2126–30. http://dx.doi.org/10.1093/clinchem/36.12.2126.

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Abstract We describe a novel ion-selective electrode (ISE) system that can be used in the Abbott Vision analyzer. A reusable sensor pack and a disposable test pack have been miniaturized to approximately the size and weight of a conventional Vision test pack, thus eliminating the need for a separate ISE module. The sensor pack contains a fluid path, battery-powered electronics, and screw-in electrodes. The test pack contains separate chambers and fluid channels for a blood specimen and two aqueous calibrators. During a run, plasma is separated from blood cells and is moved sequentially, along with the two calibrators, into and out of the sensor pack by centrifugal force. Each run includes checks for electromechanical integrity, fluid contamination, calibration slope and intercept, and specimen hemolysis. The system operates with CVs of less than 2% and gives results that correlate well with those by flame photometry and direct ISE methods. Either skin-puncture or venipuncture whole blood can be assayed, as well as serum or plasma.

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Wang, S. B., O. Y. Wu, S. R. Li, Y. Y. Wang e H. W. Zhao. "A minimized and efficient low temperature loading device for indentation". Review of Scientific Instruments 93, n. 9 (1 settembre 2022): 093902. http://dx.doi.org/10.1063/5.0080913.

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Abstract (sommario):

A minimized and efficient low temperature loading device cooling with Peltier coolers for indentation test is developed. Both specimen and indentation tip are immersed in 50% methanol–water solution, totally eliminating the contact thermal drift problem. Low temperature indentation tests down to 253.8 K can be realized within 10 min. The size of the device is miniaturized within 50 × 40 × 30 mm3, and no vacuum environment is required. Monocrystalline copper is tested to perform the feasibility of the device. Based on the simple structure and stable experimental effect, the developed device can be integrated into various types of current indentation devices to attach low temperature testing ability.

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Cruz, Daniel J., André F. G. Pereira, Vasco M. Simões, Rui Amaral, Abel dos Santos e Marta C. Oliveira. "Work Hardening of Metallic Sheets under Tension-Compression and Simple Shear Reverse Loading". Key Engineering Materials 926 (22 luglio 2022): 2012–21. http://dx.doi.org/10.4028/p-73lq3w.

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The hardening models have a significant influence on the accuracy of finite element analysis (FEA). Although, isotropic hardening models are the most widely used, it is known that kinematic hardening models (describing the Bauschinger effect and permanent softening) can significantly improve the accuracy of FEA results. However, when considering sheet metal materials, the parameters of kinematic hardening models are difficult to identify due to the challenges of obtaining experimental results from test with strain path inversions. This work considers an experimental procedure that enables the analysis of the mechanical behaviour of sheet metal materials submitted to reverse loadings. A miniaturized test device was developed to perform tension and compression tests, with reverse loadings, for sheet metal materials. This specimen design has two main advantages: (1) reduces buckling during compression (compared to standard tensile test specimens) and, consequently, (2) enables the characterization of the mechanical behaviour under reverse tension-compression strain paths changes. The small size of the specimens, with 2 x 2 mm gauge area, poses the main challenge of the current methodology, namely the measurement of the strain field distribution using the Digital Image Correlation (DIC) technique. The results obtained from tension-compression tests with mini-specimens are validated by comparison with standard tensile and shear (reverse loading) and tests.

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Bergonzi, L., M. Vettori, F. Moroni, F. Musiari e A. Pirondi. "Experimental validation of miniaturized specimen developed to perform uniaxial tensile test on high performance materials". IOP Conference Series: Materials Science and Engineering 1038, n. 1 (1 febbraio 2021): 012070. http://dx.doi.org/10.1088/1757-899x/1038/1/012070.

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SAITO, Masahiro, Hideaki TAKAHASHI, Hee Don JEONG, Akira KAWASAKI e Ryuzo WATANABE. "Evaluation of fracture toughness for metal/Ceramics composite materials by means of miniaturized specimen technique." Transactions of the Japan Society of Mechanical Engineers Series A 57, n. 535 (1991): 522–29. http://dx.doi.org/10.1299/kikaia.57.522.

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Lašan, Michal. "Application of Small Punch Tests for Screening of Mechanical Properties for T91 Steel". Key Engineering Materials 606 (marzo 2014): 43–46. http://dx.doi.org/10.4028/www.scientific.net/kem.606.43.

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Abstract (sommario):

The T91 steel is considered a perspective structural material for Generation IV (GEN IV) nuclear reactors components. The operating conditions of GEN IV nuclear reactor, which include higher operating temperatures, higher neutron fluencies and using liquid metals as coolants, constitute new challenges for structural materials validation. To properly assess the impact of radiation, thermal, load and environmental damage the screening test procedures for initial overview of the induced changes of mechanical properties need to be developed and validated. One of the test procedures with potential to be used for the mechanical properties screening is Small Punch test. Small Punch test receive considerable attention since their development in the 1980's. The use of miniaturized test specimen constitutes minimal requirements for the test material and the option of obtaining the test material directly from the component. They have been successfully used on industrial scale for design life extension of components for energy industry in the past. In this paper we address the issue of the Fracture Appearance Transition Temperature (FATT) determination by the means of Small Punch test for the T91 steel, manufactured according to ASTM standard A387-Ed99. The test specimen were manufactured and used for the experiments in a wide range of test temperatures. Multiple levels of deformation energy were used to provide more representative interpretation of the test data. A data fit is applied on the deformation energy – test temperature dependence to obtain the value of FATT from Small Punch test, which is subsequently correlated to the values obtained from testing sub-size Charpy specimens.

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Silva, F. G. A., M. F. S. F. de Moura, N. Dourado, F. A. M. Pereira, J. J. L. Morais, M. I. R. Dias, Paulo J. Lourenço e Fernando M. Judas. "Mode I fracture characterization of human bone using the DCB test". International Journal of Structural Integrity 6, n. 3 (8 giugno 2015): 355–66. http://dx.doi.org/10.1108/ijsi-05-2014-0023.

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Purpose – Fracture characterization of human cortical bone under pure mode I loading was performed in this work. The purpose of this paper is to validate the proposed test and procedure concerning fracture characterization of human cortical bone under pure mode I loading. Design/methodology/approach – A miniaturized version of the double cantilever beam (DCB) test was used for the experimental tests. A data reduction scheme based on crack equivalent concept and Timoshenko beam theory is proposed to overcome difficulties inherent to crack length monitoring during the test. The application of the method propitiates an easy determination of the Resistance-curves (R-curves) that allow to define the fracture energy under mode I loading from the plateau region. The average value of fracture energy was subsequently used in a numerical analysis with element method involving cohesive zone modelling. Findings – The excellent agreement obtained reveals that the proposed test and associated methodology is quite effective concerning fracture characterization of human cortical bone under pure mode I loading. Originality/value – A miniaturized version of traditional DCB test was proposed for cortical human bone fracture characterization under mode I loading owing to size restrictions imposed by human femur. In fact, DCB specimen propitiates a longer length for self-similar crack propagation without undertaking spurious effects. As a consequence, a R-curve was obtained allowing an adequate characterization of cortical bone fracture under mode I loading.

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Fröbisch, N. B., A. Brar e R. R. Reisz. "New specimen of <i>Cacops woehri</i> indicates differences in the ontogenetic trajectories among cacopine dissorophids". Fossil Record 18, n. 1 (27 gennaio 2015): 73–80. http://dx.doi.org/10.5194/fr-18-73-2015.

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Abstract. The Lower Permian Dolese locality has produced numerous exquisitely preserved tetrapod fossils representing members of a lower Permian upland fauna. Therein, at least nine taxa of the clade Dissorophoidea, ranging in size from the large predaceous trematopid Acheloma to the miniaturized amphibamid Doleserpeton, highlight the great taxic and ecological diversity of this anamniote clade. Here we describe a large specimen of the dissorophid Cacops woehri, which was previously only known from the juvenile or subadult holotype skull. Another member of the genus Cacops present at the Dolese locality, Cacops morrisi, is also represented by specimens spanning juvenile, subadult, and adult stages, allowing for a comparison of morphological changes taking place in the late phases of the ontogenetic trajectory of cacopine dissorophids. The new find shows that, in contrast to C. morrisi and C. aspidephorus, C. woehri only undergoes relatively subtle changes in skull morphology in late ontogeny and retains the overall more gracile morphology into adult stages. This includes retention of the rather shallow skull shape as well as a pattern of sculpturing consisting of elongate ridges and grooves and a large occipital flange. This suggests somewhat different functional demands in C. woehri than in other known species of Cacops, possibly associated with a different ecology paralleling the great taxic diversity of dissorophoids at the Dolese locality.

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Manahan, M. P. "Mechanical behaviour of magnetite from the Oconee-2 and TMI-1 steam generators using miniaturized specimen technology". Journal of Materials Science 25, n. 8 (agosto 1990): 3415–23. http://dx.doi.org/10.1007/bf00575365.

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35

Rzepa, S., D. Melzer, M. Koukolíková, P. Konopík, M. Brázda e J. Vavřík. "Tensile properties evaluation of additively manufactured AISI 316L thin wall and bulk material using various miniaturized specimen geometries". IOP Conference Series: Materials Science and Engineering 1178 (22 settembre 2021): 012048. http://dx.doi.org/10.1088/1757-899x/1178/1/012048.

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36

Pugia, Michael J., Gert Blankenstein, Ralf-Peter Peters, James A. Profitt, Klaus Kadel, Thomas Willms, Ronald Sommer, Hai Hang Kuo e Lloyd S. Schulman. "Microfluidic Tool Box as Technology Platform for Hand-Held Diagnostics". Clinical Chemistry 51, n. 10 (1 ottobre 2005): 1923–32. http://dx.doi.org/10.1373/clinchem.2005.052498.

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Abstract Background: Use of microfluidics in point-of-care testing (POCT) will require on-board fluidics, self-contained reagents, and multistep reactions, all at a low cost. Disposable microchips were studied as a potential POCT platform. Methods: Micron-sized structures and capillaries were embedded in disposable plastics with mechanisms for fluidic control, metering, specimen application, separation, and mixing of nanoliter to microliter volumes. Designs allowed dry reagents to be on separate substrates and liquid reagents to be added. Control of surface energy to ±5 dyne/cm2 and mechanical tolerances to ≤1 μm were used to control flow propulsion into adsorptive, chromatographic, and capillary zones. Fluidic mechanisms were combined into working examples for urinalysis, blood glucose, and hemoglobin A1c testing using indicators (substances that react with analyte, such as dyes, enzyme substrates, and diazonium salts), catalytic reactions, and antibodies as recognition components. Optical signal generation characterized fluid flow and allowed detection. Results: We produced chips that included capillary geometries from 10 to 200 μm with geometries for stopping and starting the flow of blood, urine, or buffer; vented chambers for metering and splitting 100 nL to 30 μL; specimen inlets for bubble-free specimen entry and containment; capillary manifolds for mixing; microstructure interfaces for homogeneous transfer into separation membranes; miniaturized containers for liquid storage and release; and moisture vapor barrier seals for easy use. Serum was separated from whole blood in <10 s. Miniaturization benefits were obtained at 10–200 μm. Conclusion: Disposable microchip technology is compatible with conventional dry-reagent technology and allows a highly compact system for complex assay sequences with minimum manual manipulations and simple operation.

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Jain, Manu, Navneet Narula, Amit Aggarwal, Brendon Stiles, Maria M. Shevchuk, Joshua Sterling, Bekheit Salamoon et al. "Multiphoton Microscopy: A Potential “Optical Biopsy” Tool for Real-Time Evaluation of Lung Tumors Without the Need for Exogenous Contrast Agents". Archives of Pathology & Laboratory Medicine 138, n. 8 (7 novembre 2013): 1037–47. http://dx.doi.org/10.5858/arpa.2013-0122-oa.

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Context.—Multiphoton microscopy (MPM) is an emerging, nonlinear, optical-biopsy technique, which can generate subcellular-resolution images from unprocessed and unstained tissue in real time. Objective.—To assess the potential of MPM for lung tumor diagnosis. Design.—Fresh sections from tumor and adjacent nonneoplastic lung were imaged with MPM and then compared with corresponding hematoxylin-eosin slides. Results.—Alveoli, bronchi, blood vessels, pleura, smokers' macrophages, and lymphocytes were readily identified with MPM in nonneoplastic tissue. Atypical adenomatous hyperplasia (a preinvasive lesion) was identified in tissue adjacent to the tumor in one case. Of the 25 tumor specimens used for blinded pathologic diagnosis, 23 were diagnosable with MPM. Of these 23 cases, all but one adenocarcinoma (15 of 16; 94%) was correctly diagnosed on MPM, along with their histologic patterns. For squamous cell carcinoma, 4 of 7 specimens (57%) were correctly diagnosed. For the remaining 3 squamous cell carcinoma specimens, the solid pattern was correctly diagnosed in 2 additional cases (29%), but it was not possible to distinguish the squamous cell carcinoma from adenocarcinoma. The other squamous cell carcinoma specimen (1 of 7; 14%) was misdiagnosed as adenocarcinoma because of pseudogland formation. Invasive adenocarcinomas with acinar and solid pattern showed statistically significant increases in collagen. Interobserver agreement for collagen quantification (among 3 observers) was 80%. Conclusions.—Our pilot study provides a proof of principle that MPM can differentiate neoplastic from nonneoplastic lung tissue and identify tumor subtypes. If confirmed in a future, larger study, we foresee real-time intraoperative applications of MPM, using miniaturized instruments for directing lung biopsies, assessing their adequacy for subsequent histopathologic analysis or banking, and evaluating surgical margins in limited lung resections.

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Christian, Eunike Thirza Hanita, Basari Basari, Siti Fauziyah Rahman e Yudan Whulanza. "Electrochemical Detection and Spectrophotometry of Dopamine using Commercial Screen-Printed Electrodes". Journal of Biomedical Science and Bioengineering 2, n. 1 (27 luglio 2022): 7–13. http://dx.doi.org/10.14710/jbiomes.2022.v2i1.7-13.

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Abstract (sommario):

Lab-on-chip is miniaturized devices integrated into a chip which can run one or several analyses which are usually done in laboratory settings, such as biochemical detection. Dopamine is an important neurotransmitter which regulates hormones, control of movement, emotion, attention, and motivation. Excess, lack, and dysregulation of dopamine could cause numbers of diseases and disorders. The technique used to measure and evaluate dopamine usually are expensive to run, require longer time to run, require some technical qualification to run, require expensive equipments, and some are invasive to do. These are the reasons why a lab-on-chip system is needed to make the detection of dopamine concentration faster, easier, and more portable. This paper studied the accuracy of using electrochemical detection to measure the concentration of liquid specimens of dopamine compared to uv/vis spectrophotometry. Electrochemical detection method named cyclic voltammetry was chosen for this study. The hypothesis for this study is that both peak current (ip) and absorbance positively correlate to concentration, therefore both could be used with minimal error margin. For this study, the peak current (ip) and absorbance of different concentrations of liquid specimen of dopamine are measured, and its regression were observed. It was shown that the concentration of liquid specimens of dopamine is linear to both anodic peak current (ipa) and absorbance. Due to the high R2 values of 0.9883, electrochemical detection could be used and implemented to detect dopamine concentration for application of lab-on-chip, as it is more portable and requires less volume of sample compared to spectrophotometry.

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Villacampa, I., Jia Chao Chen, Philippe Spätig, Hans Peter Seifert e F. Duval. "Helium Effects on 316L Austenitic Stainless Steel Fracture Mechanism". Key Engineering Materials 713 (settembre 2016): 228–31. http://dx.doi.org/10.4028/www.scientific.net/kem.713.228.

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The most common fracture mechanism of nuclear reactor internals is irradiation-assisted stress corrosion cracking (IASCC). Its susceptibility at relatively low dose is dominated by conventional mechanisms such as radiation-induced segregation and radiation hardening. However, the aging of the nuclear fleet combined with the increase of their life-span reveals other mechanisms that could play an important role on IASCC susceptibility. A large amount of helium (He) can be accumulated in reactor internal components of pressurized water reactors (PWR) after long term operation. This occurrence could significantly increase (or even dominate) the IASCC susceptibility at high doses. He has been homogeneously implanted in an especially designed miniaturized specimen at 300°C up to 1000 appm. Slow strain rate tests (SSRT) results in high temperature air and in simulated PWR conditions indicate that homogenized, as-implanted He does not have a significant effect on IASCC up to 1000 appm under these test conditions.

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Alfreider, M., M. Meindlhumer, V. Maier-Kiener, A. Hohenwarter e D. Kiener. "Extracting information from noisy data: strain mapping during dynamic in situ SEM experiments". Journal of Materials Research 36, n. 11 (19 gennaio 2021): 2291–304. http://dx.doi.org/10.1557/s43578-020-00041-0.

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Abstract Micromechanical testing techniques can reveal a variety of characteristics in materials that are otherwise impossible to address. However, unlike to macroscopic testing, these miniaturized experiments are more challenging to realize and analyze, as loading and boundary conditions can often not be controlled to the same extent as in standardized macroscopic tests. Hence, exploiting all possible information from such an experiment seems utmost desirable. In the present work, we utilize dynamic in situ microtensile testing of a nanocrystalline equiatomic CoCrFeMnNi high entropy alloy in conjunction with initial feature tracking to obtain a continuous two-dimensional strain field. This enables an evaluation of true stress–strain data as well as of the Poisson’s ratio and allows to study localization of plastic deformation for the specimen. We demonstrate that the presented image correlation method allows for an additional gain of information in these sophisticated experiments over commercial tools and can serve as a starting point to study deformation states exhibiting more complex strain fields. Graphic abstract

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41

Krans, J. M., e T. L. van Rooy. "A Miniature Low Voltage SEM with High Resolution". Microscopy and Microanalysis 5, S2 (agosto 1999): 322–23. http://dx.doi.org/10.1017/s1431927600014938.

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Abstract (sommario):

Miniaturization of electron optical systems has gained much interest over the last decade [1,2]. In a scanning electron microscope, downscaling of the column dimensions is expected to allow for high resolution imaging at low electron beam voltage. Main advantages of low voltage imaging are lower penetration depth, increased secondary electron yield, less specimen charging and better topographic contrast [3].We have developed a miniature scanning electron microscope (SEM) with high resolution at low beam energies. The outer dimensions of the miniaturized SEM column are 25 mm diameter and 95 mm length, including conventional field emitter electron source module. The column prototype is shown in Fig. 1. The size reduction has been achieved by the exclusive implementation of electrostatic column components. Electron optical simulations indicate that the retarding objective lens of the miniature SEM allows for a probe resolution of 3 nm at 1 keV beam energy. The secondary electrons are collected at an internal scintillator detector.

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Komazaki, Shinichi, T. Nakata, Takayuki Sugimoto e Yutaka Kohno. "Creep Property Evaluation of Heat-Resistant Steels by Small Punch Creep Test". Materials Science Forum 539-543 (marzo 2007): 4434–39. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.4434.

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The recently developed small punch (SP) creep test was applied to four different heatresistant ferritic steels, namely, two kinds of conventional ferritic steels which had been actually used in the high-temperature components for long periods and two advanced high chromium ferritic steels for fusion reactor materials to investigate the applicability of the SP creep test. The ratio of the load of SP creep test to the stress of standard uniaxial creep test was calculated so that both the creep rupture curves (load/stress versus Larson-Miller parameter curves) were overlapped to convert the results of SP creep test into those of standard test. As a result, the ratio was determined to be 2.4, irrespective of the kind of ferritic steel. This result indicates that the creep rupture strength of heat-resistance ferritic steels can be estimated using a miniaturized plate-type specimen and this conversion coefficient 2.4 independent of the kind of ferritic steel.

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Dehkhoda, Sahar, Mingyuan Lu e Han Huang. "Adhesion Evaluation of an Embedded SiN/GaAs Interface Using a Novel “Push-Out” Technique". Micromachines 14, n. 1 (23 dicembre 2022): 37. http://dx.doi.org/10.3390/mi14010037.

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Abstract (sommario):

Adhesion assessments of an embedded interface in a multilayer system that contains a ductile layer are challenging. The occurrence of plastic deformation in the ductile layer often leads to additional complexity in analysis. In this study, an innovative “push-out” technique was devised to evaluate the interfacial toughness (Gin) of the embedded SiN/GaAs interface in a Au/SiN/GaAs multilayer system. Focus ion beam (FIB) milling was utilized to manufacture the miniaturized specimen and scratching with a conical indenter was used to apply load. This approach effectively minimized plastic deformation in the soft Au layer while inducing tensile stress to the embedded SiN/GaAs interface. As a result, the Au/SiN bilayer detached from the GaAs substrate with little plasticity. The energy associated with the interfacial delamination was derived from analyzing the load–displacement curves obtained from the scratching test. The Gin of the SiN/GaAs interface was calculated by means of energy analysis, and the average Gin was 4.86 ± 0.96 J m−2.

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Suttner, Sebastian, e Marion Merklein. "Cyclic Tension Test of AZ31 Magnesium Alloy at Elevated Temperature Realized in a Miniaturized Uniaxial Tensile Test Setup". Materials Science Forum 854 (maggio 2016): 112–17. http://dx.doi.org/10.4028/www.scientific.net/msf.854.112.

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Abstract (sommario):

The use of new materials, e.g. aluminum and magnesium alloys, in the automotive and aviation sector is becoming increasingly important to reach the global aim of reduced emissions. Especially magnesium alloys with their low density offer great potential for lightweight design. However, magnesium alloys are almost exclusively formable at elevated temperatures. Therefore, material characterization methods need to be developed for determining the mechanical properties at elevated temperatures. In particular, cyclic tests at elevated temperatures are required to identify the isotropic-kinematic hardening behavior, which is important for numerically modeling the springback behavior. In this contribution, a characterization method for determining the cyclic behavior of the magnesium alloy AZ31B at an elevated temperature of 200 °C is presented. The setup consists of a miniaturized tensile specimen and stabilization plates to prevent buckling under compressive load. The temperature in the relevant area is introduced with the help of conductive heating. Moreover, the complex kinematic model according to Chaboche and Rousselier is identified, to map the transient hardening behavior of AZ31B after load reversal, which cannot be modeled with a single Bauschinger coefficient.

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Liu, Haiting, Yao Shen, Shuang Yang, Pengfei Zheng e Lei Zhang. "A comprehensive solution to miniaturized tensile testing: Specimen geometry optimization and extraction of constitutive behaviors using inverse FEM procedure". Fusion Engineering and Design 121 (ottobre 2017): 188–97. http://dx.doi.org/10.1016/j.fusengdes.2017.07.016.

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Mao, Xinyuan, e Hideaki Takahashi. "Development of a further-miniaturized specimen of 3 mm diameter for tem disk (ø 3 mm) small punch tests". Journal of Nuclear Materials 150, n. 1 (settembre 1987): 42–52. http://dx.doi.org/10.1016/0022-3115(87)90092-4.

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YAMAGUCHI, Teruhiro, Yuma HIGASHINO, Koki HUKINBARA, Hideki YUYA, Yoshihiro SAEKI, Hiroaki KURISHITA e Toshiyuki MESHII. "1120 Development of the Miniaturized Fracture Toughness Test Specimen for a Material in the Ductile-to-Brittle Transition Temperature Region". Proceedings of Conference of Hokuriku-Shinetsu Branch 2016.53 (2016): _1120–1_—_1120–5_. http://dx.doi.org/10.1299/jsmehs.2016.53._1120-1_.

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Maghzinajafabadi, Mohammadali, Raphael Lamprecht e Marion Semmler and Alexander Sutor. "Acoustic Pressure Pipette Aspiration Method Combined with Finite Element Analysis for Isotropic Materials". Applied Sciences 9, n. 18 (15 settembre 2019): 3875. http://dx.doi.org/10.3390/app9183875.

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Abstract (sommario):

A measurement setup combined with a numerical simulation by a linear finite element analysis is presented as a method to determine the elastic modulus of both artificial and real tissue as a function of frequency. At the end, the future goal is to develop and validate the method to measure the elastic modulus of in-vivo human vocal folds over the human phonation frequency range. In the present study, a miniaturized acoustic pressure pipette aspiration technique is developed to measure the material characteristics of an isotropic silicone specimen with similar characteristics as human vocal folds. In previous studies, friction and compression force effects of the pipette tip wall on the surface of the sample and the radius of the pipette were not investigated. Moreover, the large scale of the measurement setups made them impossible to use for clinical applications. Therefore, two different pipette sample cross-section boundary conditions and two different pipette radii were used. With the aim of ensuring reliable results, we tested our method with pipettes of two different radii on four silicone samples with different consistencies over a frequency range of 50–500 Hz. The simulation verified the measurement results in which the strong dependency of the elastic modulus on the excitation frequency, radius of the pipette, the pipette tip compression force and friction was revealed. By the simulation results, two different frequency dependent equations were developed for calculating elastic modulus of the silicone mixtures in the two cross-section boundary conditions. It was concluded that using a very small gap in between the pipette tip and the specimen can cancel the impact of the pipette tip force and friction which are the major cause of uncertainty. However, if a connection between the pipette and the surface is unpreventable, the contact force should be restricted to be absolutely zero.

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Costin, Walter, Olivier Lavigne e Andrei G. Kotousov. "Characterisation of Fracture and HAC Resistance of an Individual Microstructural Constituent with Micro-Cantilever Testing". Key Engineering Materials 713 (settembre 2016): 66–69. http://dx.doi.org/10.4028/www.scientific.net/kem.713.66.

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Abstract (sommario):

This paper focuses on the application of miniaturized fracture tests to evaluate the fracture and hydrogen assisted cracking (HAC) resistance of a selected microstructural constituent (acicular ferrite, AF) which only occurs in microscopic material volumes. Site-specific Focused Ion Beam (FIB) micro-machining was used to fabricate sharply notched micro-cantilevers into a region fully constituting of AF. The micro-cantilevers were subsequently tested under uncharged and hydrogen charged conditions with a nanoindenter. The load displacement curves were recorded and analysed with a simplified plastic hinge model for the uncharged specimen, as AF demonstrated an essentially ductile behaviour. The simplified model assisted with FE simulations provided values of the critical plastic crack tip opening displacement (CTOD). A value of the conditional fracture toughness was thereby determined as 12.1 MPa m1/2. With LEFM, a threshold stress intensity factor, Kth, to initiate hydrogen crack propagation in AF was found to range between 1.56 MPa m1/2 and 4.36 MPa m1/2. All these values were significantly below the corresponding values reported for various ferrous alloys in standard macro-tests. This finding indicates that the fracture and HAC resistance at the micro-scale could be very different than at the macro-scale as not all fracture toughening mechanisms may be activated at this scale level.

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Haque, M. A., H. D. Espinosa e H. J. Lee. "MEMS for In Situ Testing—Handling, Actuation, Loading, and Displacement Measurements". MRS Bulletin 35, n. 5 (maggio 2010): 375–81. http://dx.doi.org/10.1557/mrs2010.570.

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Abstract (sommario):

AbstractMechanical testing of micro- and nanoscale materials is challenging due to the intricate nature of specimen preparation and handling and the required load and displacement resolution. In addition, in Situ testing requires the entire experimental setup to be drastically miniaturized, because conventional high-resolution microscopes or analytical tools usually have very small chambers. These challenges are increasingly being addressed using microelectromechanical systems (MEMS)-based sensors and actuators. Because of their very small size, MEMS-based experimental setups are the natural choice for materials characterization under virtually all forms of in Situ electron, optical, and probe microscopy. The unique advantage of such in Situ studies is the simultaneous acquisition of qualitative (up to near atomic visualization of microstructures and deformation mechanisms) and quantitative (load, displacement, flaw size) information of fundamental materials behavior. In this article, we provide a state-of-the-art overview of design and fabrication of MEMS-based devices for nanomechanical testing. We also provide a few case studies on thin films, nanowires, and nanotubes, as well as adhesion-friction testing with a focus on in Situ microscopy. We conclude that MEMS devices offer superior choices in handling, actuation, and force and displacement resolutions. Particularly, their tight tolerances and small footprints are difficult to match by off-the-shelf techniques.

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