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Hermansson, Leif, Lars Kraft, Karin Lindqvist, Nils Otto Ahnfelt, and Hakan Engqvist. "Flexural Strength Measurement of Ceramic Dental Restorative Materials." Key Engineering Materials 361-363 (November 2007): 873–76. http://dx.doi.org/10.4028/www.scientific.net/kem.361-363.873.
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Flexural strength of a dental material reflects its ability to withstand tensile stresses and thus the fracture risk of a filling. The flexural strength of an experimental bioceramic Calcium aluminate-based (CA) dental restorative material was measured using three different methods with a composite (Tetric Ceram), a glass ionomer cement (Fuji II) and a phosphate cement (Harward) as references. The three test methods were: a) ISO 4049 for dental composites, 3-point bend test b) EN 843-1 for ceramic materials, 3-point bend test and c) ASTM F-394, biaxial ball-on-disc for ceramic materials. The strength of the CA-material, tested in the ball-on-disc method, is close to the theoretical strength based on the microstructure of the material (max. grain size of 15 μm). The composite material and the phosphate cement were rather insensitive to the test method, while the glass ionomer cement as the CA-material showed sensitivity towards the test method. A modified biaxial test method for evaluation of strength of dental materials in a close to real-life component is proposed.
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T. Mohamed, Muzher. "Study of the Fracture Strength of Alumina (Al2O3) Ceramic Using 3-Point Bend and Uniaxial Compressive Test." Diyala Journal For Pure Science 13, no. 4 (October 1, 2017): 38–45. http://dx.doi.org/10.24237/djps.1304.297a.
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Jeong, Haksan, Woo-Ram Myung, Kyung-Yeol Kim, Kyung Deuk Min, and Seung-Boo Jung. "Mechanical Reliability of Epoxy Sn–58wt.%Bi Composite Solder Under Temperature-Humidity Treatment with Organic Solderability Preservatives (OSP) Surface Finish." Science of Advanced Materials 12, no. 4 (April 1, 2020): 525–30. http://dx.doi.org/10.1166/sam.2020.3660.
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The microstructures and mechanical reliability of Sn–58Bi solder and epoxy Sn–58Bi composite solder joint were investigated with organic solderability preservative surface finishes. The mechanical reliabilities of Sn58Bi and epoxy Sn58Bi solder were evaluated by the board-level drop test and the 3-point bend test after temperature-humidity storage testing. The microstructure and chemical composition of the solder joints were characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy, respectively. The addition of epoxy in solder paste did not affect the morphology of the intermetallic compound. The thickness of the scalloped-shaped Cu6Sn5 intermetallic compound of solder/OSP joint increased with aging time. The drop number until fail for the epoxy Sn58Bi/OSP joint was higher than that for the Sn–58Bi/OSP joint; the average numbers of drops withstood by the Sn–58Bi/OSP joint and epoxy Sn–58Bi/OSP joint following the reflow process were fewer than 10 drops and 180 drops, respectively. The drop number of solder/OSP joints decreased with increasing aging time. The result of the 3-point bend tests shows that the number of bend cycles for the epoxy Sn–58Bi/OSP joint was 30 times higher than that for the Sn–58Bi/OSP joint. The number of bend cycles for solder/OSP joints was decreased with increasing aging time.
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Jeong, Haksan, Woo-Ram Myung, Yong-Gue Sung, Kyung-Yeol Kim, and Seung-Boo Jung. "Effect of Epoxy on Mechanical Property of SAC305 Solder Joint with Various Surface Finishes Under 3-Point Bend Test." Journal of Nanoscience and Nanotechnology 18, no. 9 (September 1, 2018): 6316–20. http://dx.doi.org/10.1166/jnn.2018.15624.
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Khan, W. Q., Q. Wang, and X. Jin. "Transformation Temperatures, Shape Memory and Magnetic Properties of Hafnium Modified Ti-Ta Based High Temperature Shape Memory Alloys." High Temperature Materials and Processes 36, no. 2 (February 1, 2017): 113–19. http://dx.doi.org/10.1515/htmp-2015-0113.
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AbstractIn this study the modification effect of Hf content on the shape memory properties and magnetic permeability of a 75.5-77Ti-20Ta-3-4.5Hf alloy system has been systematically studied by DSC, three-point bend test, vector network analyzer and XRD. The martensitic transformation temperature, heat of reaction and recovery strain increases with the increase of hafnium and tantalum content. A stable high temperature shape memory effect was observed (Ms = 385–390 °C) during the two thermal cycles between 20 °C and 725 °C. Transformation temperatures and heats of reaction were determined by DSC measurements. Recovery strain was determined by three-point bend testing. Also an alloy, 70Ti-26Ta-4Hf, with higher tantalum content was produced to observe the effect of Ta on the shape memory properties. Permeability increases gradually from 1.671 to 1.919 with increasing content of hafnium modification and remains stable in the frequency range of 450 MHz to 1 GHz.
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Chauhan, Richa, and Anindya Bhar. "Static energy absorption capacity of grid stiffened composite plates." International Journal of Engineering, Science and Technology 13, no. 1 (July 9, 2021): 88–92. http://dx.doi.org/10.4314/ijest.v13i1.13s.
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This paper presents an experimental study on the energy absorption capacity of iso-grid and ortho-grid stiffened composite plates under transverse loading. The 3-point bend test has been performed to investigate the energy absorption behavior of grid stiffened composite plates. The test results show that energy absorption capacity up to failure is improved when the load is applied on the rib side. The ortho grid stiffened structure shows a higher energy absorption capacity after failure when loaded at the rib side. The main failure modes in grid stiffened composite plates are rib fracture, matrix cracking and delamination over the skin.
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Choi, In Young, Young June Kang, Kyung Min Hong, Seong Jong Kim, and Gil Dong Lee. "Study on the Improvement of the Image Analysis Speed in the Digital Image Correlation Measurement System for the 3-Point Bend Test." Journal of the Optical Society of Korea 18, no. 5 (October 25, 2014): 523–30. http://dx.doi.org/10.3807/josk.2014.18.5.523.
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Bardelcik, Alexander, Alexandre Bouhier, and Michael J. Worswick. "Three Point Bend Performance of Solutionized, Die Quenched and Heat Treated AA7075 Beam Members." Materials Science Forum 794-796 (June 2014): 431–36. http://dx.doi.org/10.4028/www.scientific.net/msf.794-796.431.
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To overcome the low room temperature formability of AA7075-T6 aluminum sheet, without sacrificing the high strength properties of this alloy, a hat section beam member was formed and quenched within a cold die immediately after a 20 minute solutionizing treatment. Natural aging for 24 hours followed the forming process which was then followed by various heat treatments that included a typical precipitation hardening (PH) and industrial paint bake (PB) temperature-time treatment. Tensile specimens were extracted from the beams to evaluate their mechanical properties. When compared to the as-received AA7075-T6 mechanical properties, the beams heat treated with the PH, PHPB and PB treatment resulted in a 5%, 13% and 20% reduction in ultimate tensile strength respectively. A similar trend was shown for the yield strength measurements. There was little effect of the heat treatments on the total elongation, with the PH condition showing a slight improvement. A backing plate was riveted to the beams and a quasi-static 3 point bend test was conducted to evaluate the crush performance. The peak load for the PH, PHPB and PB beams was 9.2, 8.5 and 7.3 kN respectively, but the calculated energy-displacement (or energy absorption) curves were similar for the PH and PHPB parts due to a more ductile fracture behavior for the PHPB material condition.
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Guo, Jian-Min, Li-Ying Gong, and Yan Liu. "Characteristic analysis of carbon nanotube thread embedded into three-dimensional braided composite under bending load." Science and Engineering of Composite Materials 24, no. 5 (September 26, 2017): 791–98. http://dx.doi.org/10.1515/secm-2015-0447.
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AbstractIn this paper, we introduce an embedded method of carbon nanotube threads (CNTs) in three-dimensional (3-D) braided composite material preform. We investigate the strain sensing properties of CNTs embedded into 3-D braided composites using three-point bend test under different loads. The resistance change rate properties of CNTs in composites under tensile and compressive loading are analyzed in detail. Experimental results show that in the three-point bending process, the resistance of CNTs exponentially increases with the increase of strain until the specimen loading to fracture. Moreover, the residual resistance of CNTs has been observed after unloading. Our experiments have shown that structure health status of 3-D braided composites can be sensed and monitored in real-time using CNTs sensor under bending load. This study provides an experimental basis to lay the foundation for the structural health monitoring system construction of 3-D braided composites.
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Singh, Parminder, D. R. Prajapati, and Shankar Sehgal. "Investigations on Physical and Mechanical Characterization of the Joints Fabricated through Microwave Hybrid Heating Method." Advances in Science and Technology 105 (April 2021): 25–41. http://dx.doi.org/10.4028/www.scientific.net/ast.105.25.
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This paper presents the current major research developments and growths in the area of microwave hybrid heating-based joining of similar and dissimilar materials. The study discusses on the different types of specimen materials, susceptor materials, fillers and microwave power level used by researchers for joining process. Comparative studies of joints using different parametric conditions are also mentioned. Physical characterization of joint has been investigated with optical microscope, scanning electron microscope, energy dispersive spectroscopy, electron probe micro analysis, X-ray diffraction and mechanically with hardness test, tensile test, 3-point bend test, impact test. Various methods for design of experiment and optimization are also used to obtain better results. Current study will facilitate the proper choice of input parameters for easy and good joints formation through the microwave hybrid heating method.
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Lal, Sohan, C. P. Paul, C. H. Premsingh, P. Bhargava, S. K. Mishra, V. K. Raghuvanshi, L. M. Kukreja, and S. K. Deb. "Parametric Dependence and Characterization of Laser Brazed Copper-Stainless Steel Joints." Advanced Materials Research 585 (November 2012): 450–54. http://dx.doi.org/10.4028/www.scientific.net/amr.585.450.
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Joining of dissimilar metals leading to better material utilization with improved functionality encouraged the research thrust on various dissimilar material joining processes including laser brazing. This papers reports the development of laser brazing joints and their characterization for 3 mm thick Cu sheet with 3 mm thick AISI 316L stainless steel (SS) sheet in butt joint configuration using 63Ag-35.25Cu-1.75Ti active brazing foil as filler metal. Comprehensive experiments were carried out to identify the optimum processing parameters for controlled simultaneous heating of the filler metal and sh-7eets by laser beam resulting in melting of the filler metal without melting Cu and SS sheets. Using this methodology, a number of brazed joints were successfully prepared at different set of processing parameters. The brazed joints were subjected to various non-destructive (visual and dye-penetrant test) and destructive (microscopic examination, energy dispersive spectroscopy, four point bend testing etc.) characterization techniques. The results demonstrated that laser energy per unit length of 100 J/m is threshold limit for feasibility of brazing process for selected metal and thickness combination. Microscopic studies of transverse section of laser brazed joint showed full penetration across the thickness without the melting of parent metals. EDS studies showed the diffusion of filler material (Ag) more towards the Cu sheet as compared to that of SS sheet. Four point bend test showed that the alignment of laser beam-metal joint was critical for the brazing joint strength and improved joint strength was achieved when the beam was at the centre of the brazing joint. A maximum joint strength of 343.7 MPa was achieved for laser power of 550 W at scan speed of 3 mm/min.
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Whelan, Maurice P., Erwin Hack, Thorsten Siebert, Richard L. Burguete, E. A. Patterson, and Q. Saleem. "On the Calibration of Optical Full-Field Strain Measurement Systems." Applied Mechanics and Materials 3-4 (August 2006): 397–402. http://dx.doi.org/10.4028/www.scientific.net/amm.3-4.397.
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There are no standard reference materials suitable for the calibration of full-field optical strain measurement systems. This is hindering the uptake of the technology by industrial end-users since optical metrology instrumentation and procedures cannot be easily integrated into quality assurance systems. The EU-funded SPOTS project is developing a physical reference material (PRM) and measurement protocol that should provide the basis of a calibration standard for establishing the traceability of strain values obtained with optical devices. This paper describes a PRM based on a parametric design of monolithic four-point bend test that can reliably generate a known strain field over a range of specimen sizes. Measurements acquired from strain gauges and LVDTs compared well with data obtained from ESPI, digital image correlation, photoelasticity and thermoelasticity studies, demonstrating excellent repeatability and inter-laboratory reproducibility.
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Nuruddin, Md, Raju Gupta, Alfred Tcherbi-Narteh, Mahesh Hosur, and Shaik Jeelani. "Synergistic Effect of Graphene Nanoplatelets and Nanoclay on Epoxy Polymer Nanocomposites." Advanced Materials Research 1119 (July 2015): 155–59. http://dx.doi.org/10.4028/www.scientific.net/amr.1119.155.
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The prime objective of this study was to fabricate epoxy polymer composite modified with graphene nanoplatelets (GP) and montmorillonite nanoclay (MMT) binary filler materials. Different loading percentages of individual and binary nanofillers were incorporated into an epoxy matrix system to investigate the synergistic effect of nanofillers on composites properties. Dynamic mechanical analysis (DMA) and three point bend test were carried out to investigate the viscoelastic and flexural properties of neat epoxy and nanofillers reinforced nanocomposites. Incorporation of 3 wt. % of MMT and 0.1 wt. % of GP resulted in better flexure strength, modulus and storage modulus although there is no significance change in glass transition temperature (Tg).
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Moya-Gutiérrez, C., I. Ocaña-Arizcorreta, and A. Martín-Meizoso. "Micromechanisms of Cleavage Fracture in HAZ of Low Carbon Steel Welds." Materials Science Forum 482 (April 2005): 175–78. http://dx.doi.org/10.4028/www.scientific.net/msf.482.175.
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The general objective of the present work is to study the brittle fracture of the coarsegrain heat-affected zone (CGHAZ) of a C-Mn steel. The target is to develop a probabilistic model for brittle prediction for the CGHAZ based on microstructural data. The model is based on local approach. In order to validate this model, fracture mechanical test specimens (3-point bend) have been tested at different low temperatures; temperature dependence of fracture toughness was obtained. Post-morten examination of the fracture surfaces is used to gather information about the nucleation and arresting abilities of the different phases and interfaces respectively. Metallographic analysis has also been carried out for the HAZ.
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Bardakov, V. V., A. I. Sagaydak, and S. V. Elizarov. "ACOUSTIC EMISSION BEHAVIOUR OF OVER-REINFORCED CONCRETE BEAMS." Kontrol'. Diagnostika, no. 255 (2019): 4–12. http://dx.doi.org/10.14489/td.2019.09.pp.004-012.
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The paper presents the results of the conducted experimental studies on three-point bend testing of over-reinforced concrete beams with incremental cyclic load, up to destruction, using the acoustic emission method. In total 3 RC beams differ from each other in reinforcement type, concrete composition and ultimate load were tested. Special attention is paid to the investigation of the relationship between destructive processes occurring during the testing of reinforced concrete beams and the evolution of acoustic emission data registered during the test. The analysis described in the article makes it possible, on the basis of acoustic emission data, recorded during the tests, to distinguish the stages corresponding to the different technical state of over-reinforced concrete structures.
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Lough, Connor, Will Bezold, Kevin Feltgz, Kevin Middleton, Nathan Skelley, and Samuel Gieg. "Mechanical Comparison of 3D-Printed Plates and Screws for Open Reduction and Internal Fixation of Fractures." Orthopaedic Journal of Sports Medicine 8, no. 7_suppl6 (July 1, 2020): 2325967120S0038. http://dx.doi.org/10.1177/2325967120s00389.
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Objectives: Three-dimensional (3D) printing has emerged as a promising technology in the field of orthopaedic surgery. The purpose of this study was to evaluate the mechanical properties of 3D printed 1/3 tubular plates and cortical screws compared to standard-of-care stainless steel 1/3 tubular plates and cortical screws. Methods: Replication and modification designs were developed for both plates and screws using open-source computer-assisted design (CAD) software. Models were printed in four materials: acrylonitrile butadiene styrene (ABS), carbon fiber reinforced polylactic acid (PLA), polycarbonate (PC), and polyether ether ketone (PEEK). The implants (Figure 1) were tested and compared to surgical steel plates and screws. Plates were tested with three-point bend and torsional loading using an Instron® material testing machine. Screws were analyzed on pull-out strength in a Sawbones® bone model, shear strength, and torsional loading. Each combination of design and material was placed in its own test group with a sample size (n = 5) and compared to a steel control group (n = 5) for each mechanical test. Results: Significant interaction effects between material type and design type were observed for screw shear (p = 0.003), screw torque (p = 0.023), plate 3-point bend (p = 0.002), and plate torque (p = 0.001). A significant interaction effect was not observed for screw pull-out (p = 0.407), however, a statistically significant difference in mean force between material types (p <0.0005) was observed.Screw Shear: The highest mean force when both material and design were considered was for the CFPLA modified flat design with a mean force of 105.83 N (95% CI 88.51 to 123.14).Screw Torque: The highest mean force when both material and design were considered was for the PEEK modified tilt design with a mean force of 49.51 Ncm (95% CI 43.40 to 55.63).Plate 3-Point Bend: The highest mean force when both material and design were considered was for the PEEK modification design with a mean force of 31.93 N (95% CI 30.53 to 33.33).Plate Torque: The highest mean force when both material and design were considered was for the CFPLA modified flat design with a mean force of 46.88 Ncm (95% CI 42.95 to 50.80).Screw Pull-Out: Mean force produced was highest for PC across all test groups (Figure 2) with a total mean force of 211.86 N (95% CI 186.81 to 236.90). Conclusion: This study demonstrates that desktop 3D printers are capable of printing biocompatible materials that can replicate surgical implants. Although the current materials have significant mechanical variability, they do not approximate the properties of stainless steel. The utility of 3D printed surgical implants for internal fracture fixation provides a potential clinical application in locations where equipment is not as readily available, such as developing countries, forward operating military units, or long duration space flight missions. Furthermore, the cost for 3D printers and 3D printable materials has significantly decreased over recent years. This increase in technology and associated decrease in costs, along with numerous open-source 3D modeling software programs, could provide a low-cost alternative to more expensive and less accessible standard-of-care stainless-steel implants. [Figure: see text]
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TEOH, S. H., H. Y. CHIA, M. S. LEE, A. J. N. NASYITAH, H. B. S. M. LUQMAN, S. NURHIDAYAH, and WILLY C. K. TAN. "SELF HEALING COMPOSITE FOR AIRCRAFT'S STRUCTURAL APPLICATION." International Journal of Modern Physics B 24, no. 01n02 (January 20, 2010): 157–63. http://dx.doi.org/10.1142/s0217979210064083.
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When one cuts himself, it is amazing to watch how quickly the body acts to mend the wound. Immediately, the body works to pull the skin around the cut back together. The concept of repair by bleeding of enclosed functional agents serves as the biomimetic inspiration of synthetic self repair systems. Such synthetic self repair systems are based on advancement in polymeric materials; the process of human thrombosis is the inspiration for the application of self healing fibres within the composite materials. Results based on flexural 3 point bend test on the prepared samples have shown that the doubled layer healed hollow fibre laminate subjected to a healing regime of 3 weeks has a healed strength increase of 27% compared to the damaged baseline laminate. These results gave us confidence that there is a great potential to adopt such self healing mechanism on actual composite parts like in aircraft's composite structures.
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Tan, Willy C. K., J. C. Kiew, K. Y. Siow, Z. R. Sim, H. S. Poh, and M. D. Taufiq. "Self Healing of Epoxy Composite for Aircraft's Structural Applications." Solid State Phenomena 136 (February 2008): 39–44. http://dx.doi.org/10.4028/www.scientific.net/ssp.136.39.
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When one cut himself, it's amazing to watch how quickly the body acts to mend the wound. Immediately, the body works to pull the skin around the cut back together. The concept of repair by bleeding of enclosed functional agents serves as the biomimetric inspiration of synthetic self repair systems. Such synthetic self repair systems are based on advancement in polymeric materials; the process of human thrombosis is the inspiration for the application of self healing fibres within the composite materials. Preliminary results based on flexural 3 point bend test on prepared samples have shown the healed hollow fibre laminate has a healed strength increase of 47.6% compared to the damaged baseline laminate. These results gave us confidence that there is a great potential to adopt such self healing mechanism on actual composite parts like in aircraft’s composite structures.
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Esteves, Renata A., Letícia C. C. Boaro, Flávia Gonçalves, Luiza M. P. Campos, Cecy M. Silva, and Leonardo Eloy Rodrigues-Filho. "Chemical and Mechanical Properties of Experimental Dental Composites as a Function of Formulation and Postcuring Thermal Treatment." BioMed Research International 2018 (2018): 1–6. http://dx.doi.org/10.1155/2018/9845427.
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This study evaluated the influence of formulation and thermal treatment on the degree of conversion, fracture toughness, flexural strength, and elastic modulus of experimental composites. Six composites were analyzed at BisGMA : TEGDMA molar ratios of 1 : 1 and 7 : 3 with filler at 30, 50, and 70 wt%. The degree of conversion was analyzed by Fourier transform infrared spectroscopy, fracture toughness was measured using the single-edge notched beam, and flexural strength and elastic modulus were measured with the 3-point bend test. For all tests, one-half of the specimens received thermal treatment at 170°C for 10 min. Data were analyzed by the Kruskal-Wallis or ANOVA/Tukey’s test (α = 5%). The 1 : 1 BisGMA : TEGDMA ratio showed higher properties than the 7 : 3 ratio. Although the material with 70% filler had a conversion lower than the one with 50%, it showed higher mechanical properties. The thermal treatment improved all properties in all materials. Therefore, the use of an equimolar ratio of BisGMA : TEGDMA can be paired with 70 wt% filler to design dental composites that possess increased advantageous physical and chemical properties. Furthermore, the simple and low-cost method of thermal treatment proposed for use in clinical dentistry has been shown to effectively improve the properties of all evaluated materials.
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Wereszczak, A. A., O. M. Jadaan, and T. P. Kirkland. "Edge-Controlled Mechanical Failure of Si and SiC Semiconductor Chips†." Additional Conferences (Device Packaging, HiTEC, HiTEN, and CICMT) 2010, HITEC (January 1, 2010): 000325–32. http://dx.doi.org/10.4071/hitec-awereszczak-tha11.
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Silicon (Si) and silicon carbide (SiC) semiconductor chips are subjected to thermal gradients during service, have coefficient of thermal expansion mismatches with the constituents they are attached to, and are therefore subjected to thermomechanical tensile stresses that can initiate their fracture. Because of inherent brittleness, their probabilistic (Weibull) tensile failure strength was examined to understand sustainable tensile stresses and any exhibition of strength-size-scaling. Failure stress testing of entire (10-mm-square) chips was conducted using uniaxial flexure (3-point-bending) and biaxial flexure (anticlastic bending). The advantage of the anticlastic bend test is all eight primary edges are subjected to identical sinusoidal stress distribution so tensile failure stress is concurrently sensitive to edge-state quality, surface-state quality, crystallographic orientation, and any strength anisotropies of any of those. Tensile stress tolerance of both Si and SiC chips was limited by extrinsic strength-limiting flaws located at their edges and on lapped surfaces too in the case of the Si. Both materials exhibited strength-size scaling; namely, a larger chip is likely to fail at a lower tensile stress. The anticlastic bend test method was effective for evaluating edge failure stress provided surface-type strength-limiting flaws were not dominant. Edge-strength anisotropy (i.e., crystallographic orientation dependence) was observed with both the Si and SiC chips. Surface-strength anisotropy also occurred with Si chips because one side was lapped and the other polished. Lastly, the SiC chips failed at much higher tensile stresses than Si chips; however, that strength difference could be a ramification of differences in edge-slicing quality and not necessarily from intrinsic material differences.
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Miccoli, Gabriele, Andrea Cicconetti, Gianluca Gambarini, Andrea Del Giudice, Federico Ripanti, Dario Di Nardo, Luca Testarelli, and Marco Seracchiani. "A New Device to Test the Bending Resistance of Mechanical Endodontic Instruments." Applied Sciences 10, no. 20 (October 16, 2020): 7215. http://dx.doi.org/10.3390/app10207215.
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The aims of the present study were to propose a new machine for testing the bending behavior of an instrument at multiple specific points along the cutting surface and to compare the influence of proprietary heat treatment on the bending ability of EdgeTaper (ET), Protaper Universal (PTU), EdgeTaper Platinum (ETP), and Protaper Gold (PTG). A total of 320 instruments were examined in the present study: 80 ET, 80 PTU, 80 ETP, and 80 PTG. The bending ability of all instruments was tested at a 45° angle and on three different portions of the instrument at 3, 6, and 9 mm from the tip using a customized device. Statistical analysis showed significant differences among each single instrument of the series and between ET and PTU as well as ETP and PTG. The bending behavior of a nickel–titanium rotary instrument is its ability to bend without any plastic deformation. This feature, according to the results of the present study, is variable along the cutting surface; therefore, it should be evaluated. Due to the present testing device, it would be possible to obtain reliable and trustworthy information about an instrument’s bending ability.
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Petersen, R. C. "Discontinuous Fiber-reinforced Composites above Critical Length." Journal of Dental Research 84, no. 4 (April 2005): 365–70. http://dx.doi.org/10.1177/154405910508400414.
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Micromechanical physics of critical fiber length, describing a minimum filament distance for resin impregnation and stress transfer, has not yet been applied in dental science. As a test of the hypothesis that 9-micron-diameter, 3-mm-long quartz fibers would increase mechanical strength over particulate-filled composites, photocure-resin-pre-impregnated discontinuous reinforcement was incorporated at 35 wt% into 3M Corporation Z100, Kerr Corporation HerculiteXRV, and an experimental photocure paste with increased radiopaque particulate. Fully articulated four-point bend testing per ASTM C 1161-94 for advanced ceramics and Izod impact testing according to a modified unnotched ASTM D 256-00 specification were then performed. All photocure-fiber-reinforced composites demonstrated significant improvements over particulate-filled compounds (p < 0.001) for flexural strength, modulus, work of fracture, strain at maximum load, and Izod toughness, with one exception for the moduli of Z100 and the experimental reinforced paste. The results indicate that inclusion of pre-impregnated fibers above the critical aspect ratio yields major advancements regarding the mechanical properties tested.
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Ramkumar, K. R., Habtamu Bekele, and S. Sivasankaran. "Experimental Investigation on Mechanical and Turning Behavior of Al 7075/x% wt. TiB2-1% Gr In Situ Hybrid Composite." Advances in Materials Science and Engineering 2015 (2015): 1–14. http://dx.doi.org/10.1155/2015/727141.
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The present research work involves the study of AA 7075-TiB2-Gr in situ composite through stir casting route. This in situ method involves formation of reinforcements within the matrix by the chemical reaction of two or more compounds which also produces some changes in the matrix material within the vicinity. Titanium Diboride (TiB2) and graphite were the reinforcement in a matrix of AA 7075 alloy. The composite was prepared with the formation of the reinforcement inside the molten matrix by adding salts of Potassium Tetrafluoroborate (KBF4) and Potassium Hexafluorotitanate (K2TiF6). The samples were taken under casted condition and the properties of the composite were tested by conducting characterization using X-ray diffraction (XRD), hardness test, flexural strength by using three-point bend test, scanning electron microscope (SEM), optical microstructure, grain size analysis, and surface roughness. It was found that good/excellent mechanical properties were obtained in AA 7075-TiB2-Gr reinforced in situ hybrid composite compared to alloy due to particulate strengthening of ceramic particles of TiB2in the matrix. Further, Al 7075-3% TiB2-1% Gr hybrid in situ composite exhibited improved machinability over the alloy and composites due to self-lubricating property given by the Gr particles in the materials.
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Velmurugan, Natanasabapathy, Poornima Reddy, Suma Balla, Sandhya S. Raghu, Garlapati T. Gupta, and Hrudi S. Sahoo. "Effect of 5% Calcium Hypochlorite on Mechanical Properties of Root Dentin: An in vitro Study." Journal of Operative Dentistry & Endodontics 1, no. 2 (2016): 56–59. http://dx.doi.org/10.5005/jp-journals-10047-0012.
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ABSTRACT Introduction The aim of this study was to compare in vitro the effect of 5% calcium hypochlorite [Ca(OCl)2] and 5% sodium hypochlorite (NaOCl) on flexural strength and modulus of elasticity of root dentin. Materials and methods The available chlorine concentration of each solution was determined using iodometric titration. Standardized planoparallel dentin bars (n= 20) were divided into two test groups and one control group. The control, group 1, consisted of dentin bars stored in normal saline. The dentin bars in the two test groups were treated by exposure to following solutions: Group 2 to 5% Ca(OCl)2; and group 3 to 5% NaOCl. All the three test solutions were changed once in 15 minutes for 30 minutes. The dentin bars were then loaded to failure using three-point bend test. Results Available chlorine concentration was 64% in both the test solutions. There was a significant reduction in the flexural strength of 5% NaOCl group compared to 5% Ca(OCl)2-treated ones. A significant difference in modulus of elasticity was observed between the test groups and the control groups and also between the 5% Ca(OCl)2 and 5% NaOCl groups. Conclusion Within the limitations of this study, 5% NaOCl reduced the flexural strength and modulus of elasticity of root dentin bars more when compared to 5% Ca(OCl)2. How to cite this article Reddy P, Balla S, Raghu SS, Velmurugan N, Gupta GT, Sahoo HS. Effect of 5% Calcium Hypochlorite on Mechanical Properties of Root Dentin: An in vitro Study. J Oper Dent Endod 2016;1(2):56-59.
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Jun, Hyun Kyu, and Jung Won Seo. "Calculation of Critical Crack Size of Repair Welded Rail." Advanced Materials Research 891-892 (March 2014): 1175–80. http://dx.doi.org/10.4028/www.scientific.net/amr.891-892.1175.
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Repair of damaged rail surface by overlay welding is the common rail maintenance method. But the discontinuity in material between base and weld brings initiation of cracks and they causes a rail fracture. Unfortunately, such cracks are hard to detect on site because the weld boundary prevents the echo signals penetration by reflection. So estimation of the critical crack size (CCS) has been a critical issue in railroad industry to prevent a rail from sudden fracture. In this study, we calculated the critical size of crack which was initiated and propagated underneath of the overlay welded rail by applying linear elastic fracture mechanics. For this purpose, we measured the maximum load carrying capacities of cracked UIC60 by inverted 3 point bend tests and checked the feasibility of the finite element (FE) analysis procedure. We could find the correlation in crack size between the test and 3D FE analysis results and applied the proposed 3D FE analysis model to calculate the CCS of a rail. We calculated the stress intensity factors on cracked rail by increasing the size of crack until the rail broke. The CCS was calculated as around 30.0 mm under the normal railway service operating condition.
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Kul, Esra, Faruk Yesildal, Emre Mandev, and Cafer Celik. "Optimization of Variables Influencing the Thermal Conductivity and Fracture Strength of Reinforced PMMA by Using the Taguchi Method." Materiale Plastice 57, no. 3 (September 30, 2020): 137–46. http://dx.doi.org/10.37358/mp.20.3.5388.
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How the particle size and volumetric ratio of silicon carbide (SiC) powder additions will strengthen polymethyl methacrylate (PMMA) is unclear. The purpose of this in vitro study was to optimize the reinforcement parameters of PMMA with SiC powder by using the Taguchi experimental design method. Particle size, volumetric rate, silane coupling rate, and mixing type were determined as parameters that would affect the reinforcement of PMMA with SiC powder. Using the Taguchi L9 orthogonal array, test specimens with different parameter combinations were fabricated and tested. The fracture load (in newtons) of each specimen group was recorded with the 3-point bend test. The thermal conductivity values of 60x50-mm and 3-mm-thick rectangular specimens were measured by using the Linseis THB100 thermal conductivity unit. The thermal diffusivity values were then calculated. Thermal analysis indicated improvement in the thermal conductivity of PMMA after reinforcement with SiC. The maximum thermal diffusivity was obtained with 15% SiC powder by volume. Thermal conductivity and flexural strength increased with an increase in particle size. The maximum flexural strength value was obtained with 5% SiC powder by volume. Increasing the particle size of the filler SiC powder resulted in increased thermal conductivity and flexural strength. Increasing the SiC filler powder by volume increased the thermal conductivity of PMMA but reduced its flexural strength. This study helped determine the optimum conditions for the use of SiC powder. Knowledge of the importance of these variables will help in more effective modification of denture base resin with SiC powder to improve heat transfer without adversely affecting strength.
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Abhinav Agarwal, Manesh Lahori, and Dharmesh Kumar. "AN IN VITRO STUDY TO ASCERTAIN THE TRANSVERSE STRENGTH OF DENTURE BASE RESIN REINFORCED WITH TWO DIFFERENT FIBERS AND THEIR COMBINATION." UNIVERSITY JOURNAL OF DENTAL SCIENCES 6, no. 1 (July 12, 2020): 01–05. http://dx.doi.org/10.21276/ujds.2020.6.1.2.
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Purpose: The purpose of this study was to compare the transverse strength of denture base resin reinforced with two distinct fibers and their combination with the denture base resin without any reinforcement. MaterialsandMethod: Atotal40testsamplesofclearheatcureresinwerefabricatedwiththehelpofa customized metallic die and divided in to four groups- Group1: samples fabricated with clear acrylic resin without any reinforcement(Control group),Group2: samples reinforced with carbon fiber epoxy resin composite block, Group3: samples reinforced with glass fiber epoxy resin composite block, Group 4: samples reinforced with combination of carbon and glass fiber epoxy resin composite block. After finishing and polishing all the samples were having final dimension of 3 cm × 1 cm × 0.3cm with a ±0.02 error measured with digital vernier caliper. Samples were immersed in water for 7 days in an incubator. A 3-point bend test was done in a universal testing machine, and load to fracture was recorded (MPa). Statistical analysis was performed using one way analysis of variance (ANOVA) followed by tukey HSD post-hoc test to compare mean transverse Strength in four groups.
Results: Group 2 and group 4 showed highest strength with significant difference with all other groups and non-significant with each other. Group1(control group) showed lowest transverse strength among all the groups.
Conclusion: carbon fiber and glass fiber alone provided either good transverse strength or good esthetics respectively while unique combination of carbon and glass fiber epoxy resin composite significantly increased the transverse strength of acrylic resin along with good esthetics.
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Bonneville, Alain, Trenton T. Cladouhos, Susan Petty, Adam Schultz, Carsten Sørlie, Hiroshi Asanuma, Guðmundur Ómar Friðleifsson, Claude Jaupart, and Giuseppe de Natale. "The Newberry Deep Drilling Project (NDDP) workshop." Scientific Drilling 24 (October 22, 2018): 79–86. http://dx.doi.org/10.5194/sd-24-79-2018.
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Abstract. The important scientific questions that will form the basis of a full proposal to drill a deep well to the ductile–brittle transition zone (T>400 ∘C) at Newberry Volcano, central Oregon state, USA, were discussed during an International Continental Drilling Program (ICDP) sponsored workshop held at the Oregon State University-Cascades campus in Bend, Oregon, from 10 to 13 September 2017. Newberry Volcano is one of the largest geothermal heat reservoirs in the USA and has been extensively studied for the last 40 years. The Newberry Deep Drilling Project (NDDP) will be located at an idle geothermal exploration well, NWG 46-16, drilled in 2008, 3500 m deep and 340–374 ∘C at bottom, which will be deepened another 1000 to 1300 m to reach 500 ∘C. The workshop concluded by setting ambitious goals for the NDDP: (1) test the enhanced geothermal system (EGS) above the critical point of water, (2) collect samples of rocks within the brittle–ductile transition, (3) investigate volcanic hazards, (4) study magmatic geomechanics, (5) calibrate geophysical imaging techniques, and (6) test technology for drilling, well completion, and geophysical monitoring in a very high-temperature environment. Based on these recommendations, a full drilling proposal was submitted in January 2018 to the ICDP for deepening an existing well. The next steps will be to continue building a team with project, technology, and investment partners to make the NDDP a reality.
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Yesildal, Faruk, Esra Kul, Ruhi Yesildal, and Khamirul Amin Matori. "Investigation of the Thermal Conductivity and Flexural Strength of Polymethylmethacrylate Denture Base Material with SiC and Al2O3 Added." Materiale Plastice 58, no. 2 (July 5, 2021): 91–99. http://dx.doi.org/10.37358/mp.21.2.5481.
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Although polymethylmethacrylate (PMMA) is widely used as a denture base material, its disadvantages include low strength and low thermal conductivity. The effects on thermal conductivity, flexural strength, thermal diffusivity, and elastic modulus of adding Al2O3 and SiC powders in different volumes to PMMA were investigated. A total of 60 specimens were prepared in 10 groups (five groups for the thermal conductivity test and five groups for the flexural strength test (n:6). The specimens were immersed in water for 30 days before the testing. Thermal conductivity values were measured by the transient hot bridge (THB) method, and flexural strengths were measured by the 3-point bend test. A significant difference was found in thermal conductivity, flexural strength, thermal diffusivity and elastic modulus values between independent groups (P [0.001) using the Kruskal-Wallis test. The Kruskal Wallis 1-way ANOVA was used for the post hoc tests after Kruskal Wallis (a;=.05). The thermal conductivity of PMMA increased significantly with the addition of 15% SiC and 15% Al2O3. The flexural strength values decreased significantly with the addition of 10% SiC and 15% Al2O3. The thermal diffusivity values increased significantly with the addition of 10% and 15% SiC. The Young modulus of PMMA decreased when 10% SiC, 10% Al2O3 and 15% Al2O3 were added. Environmental scanning electron microscope (ESEM) showed that ceramic powders were dissipated in PMMA. The addition of 15% SiC powders to PMMA increased thermal conductivity without significantly reducing flexural strength. This study helped determine the optimum volumes for the use of SiC and Al2O3 powders. Knowledge of the importance of this variable will help in more effective modification of denture base resin with SiC and Al2O3 powders to improve heat transfer without adversely affecting strength.
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Huh, Dae, and Dae-Hun Kim. "Joining of AlN to Cu Using In-base Active Brazing Fillers." Journal of Materials Research 12, no. 4 (April 1997): 1048–55. http://dx.doi.org/10.1557/jmr.1997.0146.
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Brazing of aluminum nitride (AlN), which is a good ceramic substrate in high power electronic applications, to copper was investigated using In-base active fillers. Compositions of brazing fillers were chosen as In–1 wt.% Ti (IT1), In–19 wt.% Ag–2 wt.% Ti (IAT2), In–15 wt.% Ti (IT15), and In–52 wt.% Ag–20 wt.% Cu–3 wt.% Ti (ACIT3). Brazing operation was performed in vacuum at temperatures of 650–900 °C. The brazing fillers showed good wetting on AlN and led to a strong bond between AlN and braze alloy. From the microstructural analysis, no evidence of reaction layer was clearly found at the interface under the experimental brazing conditions. The composition of brazing alloy layer changed into Cu9In4 phase due to the extensive dissolving of Cu from base metal. Bond strength, measured by 4-point bend test, was obtained as high as 23–30 kgf for the Cu/AlN/Cu joint brazed with IT15 and ACIT3 fillers, and shown to be nearly constant even when the temperature was varied within 700–800 °C. Most of the fracture appeared to proceed through the interior of the AlN ceramic. Based on the experimental results, it is believed that a strong bonding between AlN and braze alloy can be achieved without the apparent forming of a Ti-rich reaction layer at the interface.
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Tripathi, Gyanendra Nath, and Hiroaki Wagatsuma. "PCA-Based Algorithms to Find Synergies for Humanoid Robot Motion Behavior." International Journal of Humanoid Robotics 13, no. 02 (May 25, 2016): 1550037. http://dx.doi.org/10.1142/s0219843615500371.
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Applying principal component analysis (PCA) to find synergy signal for specific motion of Robot is a standard method. However, implementation of PCA gives synergy solely on quantitative basis. The algorithms proposed in this paper advocates the enhancement of qualitative measure of PCA to locate well-coordinated synergy signals. The two main control strategies of central nervous system (CNS) are taken into account for enhancement of algorithms. First one is the CNS strategy of separate synergy generation for individual limbs and second is the trajectory generation of complex movement using via-points. The proposed algorithms find the synergy without loss of generality of implementation. Humanoid robot NAO is used as a robotic platform to test the result of the algorithm. The synergy for a group of motors is calculated by implementing the algorithm on motors position sensor data of the robot corresponding to three motion pattern 1. Knee bend sitting–standing, 2. Sitting–standing on chair, and 3. Walking. The improvement in result is statistically measured by calculating error between original and reconstructed signal for proposed algorithms and applying Z-test tested on error signals. Another statistical measure of improvement is treated by calculating ‘Goodness of Fit’ for original and reconstructed signal.
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Khanna, Prachi, and Racquel Z. LeGeros. "Properties of Gelatin/Carbonate Apatite Composite Compared to Bovine Bone." Key Engineering Materials 529-530 (November 2012): 413–16. http://dx.doi.org/10.4028/www.scientific.net/kem.529-530.413.
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Bone is a composite of approximately 65% inorganic phase (carbonate apatite, CHA) and a 35% organic phase (mostly collagen). To date, several commercial composites consisting of natural or synthetic polymers and calcium phosphates ( hydroxyapatite, tricalcium phosphate, biphasic calcium phosphates) are recommended for use in bone repair. Objective: The aim of this study was to compare the physico-chemical properties of gelatin/carbonate apatite composites with that of bovine bone. Native (Gel) or cross-linked (Gel*) was used. Methods: The CHA was prepared by hydrolysis method. The gelatin (denatured collagen) was cross-linked using Genipin. The gelatin/CHA composite were prepared by mixing of 35% gelatin and 65% CHA and freeze-drying. The composites were characterized using x-ray diffraction (XRD), FT-IR spectroscopy, scanning electron microscopy (SEM) and thermogravimetry (TGA). Dissolution properties were determined in acidic buffer (0.1M KAc, pH 6, 37°C). Mechanical strength was determined using 3-point bend test. Bovine bone was similarly characterized for comparison. Results: The composition and crystallite size of the CHA were similar to that of the bone mineral. The Gel/CHA and Gel*/CHA composites showed several physico-chemical properties (crystallinity, composition, thermal stability, mechanical strength, dissolution rate) similar to that of bone. Gel*/CHA compared to Gel/CHA composites showed lower elastic modulus, flexural strength, dissolution rate, swelling and higher porosity. Conclusion: The Gel*/CHA composites presented several properties similar to those of bovine bone and may have potential as bone substitute materials.
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Byun, Christine, Yifan Zheng, Aidan Pierce, Willi L. Wagner, Henrik V. Scheller, Debra Mohnen, Maximilian Ackermann, and Steven J. Mentzer. "The Effect of Calcium on the Cohesive Strength and Flexural Properties of Low-Methoxyl Pectin Biopolymers." Molecules 25, no. 1 (December 24, 2019): 75. http://dx.doi.org/10.3390/molecules25010075.
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Pectin binds the mesothelial glycocalyx of visceral organs, suggesting its potential role as a mesothelial sealant. To assess the mechanical properties of pectin films, we compared pectin films with a less than 50% degree of methyl esterification (low-methoxyl pectin, LMP) to films with greater than 50% methyl esterification (high-methoxyl pectin, HMP). LMP and HMP polymers were prepared by step-wise dissolution and high-shear mixing. Both LMP and HMP films demonstrated a comparable clear appearance. Fracture mechanics demonstrated that the LMP films had a lower burst strength than HMP films at a variety of calcium concentrations and hydration states. The water content also influenced the extensibility of the LMP films with increased extensibility (probe distance) with an increasing water content. Similar to the burst strength, the extensibility of the LMP films was less than that of HMP films. Flexural properties, demonstrated with the 3-point bend test, showed that the force required to displace the LMP films increased with an increased calcium concentration (p < 0.01). Toughness, here reflecting deformability (ductility), was variable, but increased with an increased calcium concentration. Similarly, titrations of calcium concentrations demonstrated LMP films with a decreased cohesive strength and increased stiffness. We conclude that LMP films, particularly with the addition of calcium up to 10 mM concentrations, demonstrate lower strength and toughness than comparable HMP films. These physical properties suggest that HMP has superior physical properties to LMP for selected biomedical applications.
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Rocha, MG, DCRS de Oliveira, MAC Sinhoreti, JF Roulet, and AB Correr. "The Combination of CQ-amine and TPO Increases the Polymerization Shrinkage Stress and Does Not Improve the Depth of Cure of Bulk-fill Composites." Operative Dentistry 44, no. 5 (September 1, 2019): 499–509. http://dx.doi.org/10.2341/18-234-l.
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SUMMARY Objectives: To evaluate the effect of combining camphorquinone (CQ) and diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO) on the depth of cure and polymerization shrinkage stress of bulk-fill composites. Methods and Materials: Experimental bulk-fill composites were produced containing equal molar concentrations of either CQ-amine or CQ-amine/TPO. The degree of in-depth conversion through each millimeter of a 4-mm-thick bulk-fill increment was evaluated by Fourier transform near-infrared microspectroscopy using a central longitudinal cross section of the increment of each bulk-fill composite (n=3). Light-transmittance of the multi-wave light-emitting diode (LED) emittance used for photoactivation (Bluephase G2, Ivoclar Vivadent) was recorded through every millimeter of each bulk-fill composite using spectrophotometry. The volumetric shrinkage and polymerization shrinkage stress were assessed using a mercury dilatometer and the Bioman, respectively. The flexural modulus was also assessed by a three-point bend test as a complementary test. Data were analyzed according to the different experimental designs (α=0.05 and β=0.2). Results: Up to 1 mm in depth, adding TPO to CQ-based bulk-fill composites increased the degree of conversion, but beyond 1 mm no differences were found. The light-transmittance of either wavelengths emitted from the multi-wave LED (blue or violet) through the bulk-fill composites were only different up to 1 mm in depth, regardless of the photoinitiator system. Adding TPO to CQ-based bulk-fill composites did not affect volumetric shrinkage but did increase the flexural modulus and polymerization shrinkage stress. Conclusion: Adding TPO to CQ-based bulk-fill composites did not increase the depth of cure. However, it did increase the degree of conversion on the top of the restoration, increasing the polymerization shrinkage stress.
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Kiryushina, Valentina V., Yuliya Yu Kovaleva, Petr A. Stepanov, and Pavel V. Kovalenko. "A study into the scale effect on the strength properties of polymer composite materials." Nuclear Energy and Technology 5, no. 2 (May 17, 2019): 13–18. http://dx.doi.org/10.3897/nucet..35797.
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Polymer composite materials (PCM) are used extensively and are viewed as candidates for application in various industries, including nuclear power. Despite a variety of methods and procedures employed to investigate the mechanical characteristics of PCMs, the use of the laboratory sample mechanical test results to design and model large-sized structures is not always fully correct and reasonable. In particular, one of the problems is concerned with taking into account the scale parameter effects on the PCM strength and elastic characteristics immediately in the product. The purpose of the study is to investigate the scale effects on the mechanical characteristics of glass reinforced plastics using phenolformaldehyde and silicon-organic binders and a fabric quartz filler. Samples of four different standard sizes under GOST 25604-82 and GOST 4648-2014 were tested for three-point bending using an LFM-100 test machine to estimate the scale effect. The thicknesses of the model samples were chosen with regard for the wall thicknesses of full-scale products under development or manufactured commercially and the test machine features, and varied in the limits of 1.6 to 7.5 mm. The tests showed that strength decreased as the sample thickness was increased to 3 mm and more both at room and elevated (200 to 500 °C) temperatures, which can be described by an exponential function based on the Weibull statistical model. The values of the Weibull modulus that characterizes the extent of the scale effect on the strength of the tested materials were 4.6 to 6.7. The average bend strength in the sample thickness range of 3 mm and less does not vary notably or tends to increase slightly as the thickness is increased. This fact makes it possible to conclude that estimation of allowable stresses in a thin-wall product requires the use of test results for samples with a thickness that is equal to the product wall thickness since standard samples may yield overestimated allowable stress values and lead, accordingly, to incorrect calculations of the strength factor. The results obtained shall be taken into account when defining the allowable levels of operation for full-scale products and structures of polymer composites based on the laboratory sample strength data as well as when estimating their robustness as a characteristic of the product’s fail-safe operation.
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Kiryushina, Valentina V., Yuliya Yu Kovaleva, Petr A. Stepanov, and Pavel V. Kovalenko. "A study into the scale effect on the strength properties of polymer composite materials." Nuclear Energy and Technology 5, no. 2 (May 17, 2019): 103–8. http://dx.doi.org/10.3897/nucet.5.35797.
Full textAbstract:
Polymer composite materials (PCM) are used extensively and are viewed as candidates for application in various industries, including nuclear power. Despite a variety of methods and procedures employed to investigate the mechanical characteristics of PCMs, the use of the laboratory sample mechanical test results to design and model large-sized structures is not always fully correct and reasonable. In particular, one of the problems is concerned with taking into account the scale parameter effects on the PCM strength and elastic characteristics immediately in the product. The purpose of the study is to investigate the scale effects on the mechanical characteristics of glass reinforced plastics using phenolformaldehyde and silicon-organic binders and a fabric quartz filler. Samples of four different standard sizes under GOST 25604-82 and GOST 4648-2014 were tested for three-point bending using an LFM-100 test machine to estimate the scale effect. The thicknesses of the model samples were chosen with regard for the wall thicknesses of full-scale products under development or manufactured commercially and the test machine features, and varied in the limits of 1.6 to 7.5 mm. The tests showed that strength decreased as the sample thickness was increased to 3 mm and more both at room and elevated (200 to 500 °C) temperatures, which can be described by an exponential function based on the Weibull statistical model. The values of the Weibull modulus that characterizes the extent of the scale effect on the strength of the tested materials were 4.6 to 6.7. The average bend strength in the sample thickness range of 3 mm and less does not vary notably or tends to increase slightly as the thickness is increased. This fact makes it possible to conclude that estimation of allowable stresses in a thin-wall product requires the use of test results for samples with a thickness that is equal to the product wall thickness since standard samples may yield overestimated allowable stress values and lead, accordingly, to incorrect calculations of the strength factor. The results obtained shall be taken into account when defining the allowable levels of operation for full-scale products and structures of polymer composites based on the laboratory sample strength data as well as when estimating their robustness as a characteristic of the product’s fail-safe operation.
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Krystýnová, Michaela, Pavel Doležal, Stanislava Fintová, Josef Zapletal, Tomas Marada, and Jaromír Wasserbauer. "Characterization of Brittle Phase in Magnesium Based Materials Prepared by Powder Metallurgy." Key Engineering Materials 784 (October 2018): 61–66. http://dx.doi.org/10.4028/www.scientific.net/kem.784.61.
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Magnesium-zinc based materials are characteristic with the creation of intermetallic phases, strongly influencing material mechanical properties. Mg-Zn powder mixture (10 % wt. Zn) was processed by the hot pressing method under 500 MPa at 300 °C. Microstructure of the prepared material was analyzed in terms of light optical microscopy and scanning electron microscopy. Chemical and phase composition of the processed material were analyzed by energy-dispersive X-ray spectroscopy and X-ray powder diffraction, respectively. Microhardness testing was adopted to characterize created structure mechanical properties on the microscopic level. Depending on the Mg-Zn powder mixture local chemical composition, the structural and chemical analysis of the processed material revealed that it consisted of magnesium and zinc rich areas, and MgZn2 intermetallic phase. The MgZn2 intermetallic phase belongs to the so-called Laves phases group with the general formula AB2. Laves phases are characteristic with high hardness and the related high brittleness. Their presence in the material usually results in deterioration of mechanical properties such as strength and toughness. The microhardness of magnesium and zinc rich areas in the processed material was 58±1 HV 0.025 and 47 ±1 HV 0.025, respectively, while the value of the microhardness for MgZn2 intermetallic phase was 323±12 HV 0.025. Different behavior and mechanical properties of the present phases was observed on the fracture surfaces of specimens broken during the 3-point bend test. While brittle fracture was a characteristic feature for MgZn2 intermetallic phase, the rest of the material exhibited more ductile fracture behavior with characteristic transgranular failure.
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Seetala, Naidu V., Naeem Tull-Walker, Abhijit Baburaj, Jian Ren Zhou, Richard Wilkins, and Milan Barnett. "Positron Lifetime Studies of Irradiated Ultra-High Molecular Weight Polyethylene and Composites Made of Martian Regolith." Materials Science Forum 783-786 (May 2014): 1585–90. http://dx.doi.org/10.4028/www.scientific.net/msf.783-786.1585.
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Positron Annihilation Lifetime Spectroscopy (PALS) is used to study the nanoporosity and fractional free volume in Ultra High Molecular Weight Polyethylene (UHMWPE) and composites with the addition of Martian Regolith (UHMWPE-MR) as-made and irradiated with56Fe heavy ions at an energy of 600 MeV/u to three different doses (10, 32, 64 Gy). The positron lifetime spectra were obtained using22Na positron source and the spectra were analyzed to two lifetime components using POSFIT program. First short lifetime component around 0.28 ns is related to positron annihilation in material including vacancy defects and the second long lived component around 1.7 ns is due to Positronium formation in free volume pores. UHMWPE-MR composites were shown to be less porous with much lower nanopores concentration compared to the UHMWPE polymer. The average size of the nanopores is around 0.5 nm (obtained from a simple model). Larger variations in positron lifetime parameters are observed with increasing irradiation dose for UHMWPE polymer compared to UHMWPE+MR composites. The 3-point bend test results also showed larger variations with increasing irradiation dose for the UHMWPE polymer. The variations in PALS parameters may indicate an increasing competition between two processes at higher irradiation doses: 1) vacancy defects aggregation and 2) escape of vacancy defects as the local temperature increases at higher doses resulting in increased vacancy defects mobility. Present results clearly indicate a qualitative inverse relationship between nanoscale porosity measured by positron life time and mechanical properties of UHMWPE and its composite with MR.
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Kukharenko, V. M., L. P. Perkhun, and N. M. Tovmachenko. "The Method for Comprehensive Quality Evaluation of Tests. Part 1." Statistics of Ukraine 82, no. 3 (September 4, 2018): 40–48. http://dx.doi.org/10.31767/su.3(82)2018.03.04.
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Informatization of the modern society has led to the wide-scale and rapid introduction of distance training technologies in virtually all the categories of Ukrainian HEEs. Studies of the aspects related to applications of digital technologies in education processes are subject to close attention in Ukraine and beyond. An important component of the training process is test control of knowledge.
Education activities at the National Academy of Statistics, Accounting and Audit rely on criteria oriented tests. They are realized on the basis of distance training system Moodle that allows for creating test questions of various types and their repeated inclusion in various packages of test tasks. The Moodle environment allows for computation of selected statistical indicators on a fulfilled test and its individual tasks: average estimate and median, standard deviation, asymmetry, excess, internal agreement rate, standard error etc. However, these characteristics are not enough for justified acceptance of test results.
The article presents the first phase in elaborating a comprehensive method for quality evaluation of selected test tasks and the test as a whole. This method combining the classical theory, Data Mining and Item Response theory methods involves six steps. The first step, based on indicators of descriptive statistics, allows for evaluating the obtained distribution of test results. The second step involves evaluation of the validity of test tasks. The point-bead ratio is computed to derive the correlation between individual test task and individual test score of a student, with values higher than 0.5 considered satisfactory. Pearson correlation coefficient for binary variables shows the correlation between pairs of test tasks. The test tasks with negative correlations with the other test tasks are not considered as valid, and they have to be corrected or replaced. At the third step, the factor validity of the test is evaluated. The test tasks combined in groups using factor analysis methods are subject to further analysis to determine their impact on the final result, the individual test score of a student. All the above mentioned steps are illustrated by example. The computation is made by SPSS software package. The difference in interpretation of the computation results in each step for norm oriented and criteria oriented tests is demonstrated.
The description of further steps involves in the method for comprehensive quality evaluation of tests, which use Data Mining and Item Response Theory methods, will be continued in next publications.
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Wang, Bo, and T. Siegmund. "A modified 4-point bend delamination test." Microelectronic Engineering 85, no. 2 (February 2008): 477–85. http://dx.doi.org/10.1016/j.mee.2007.08.010.
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Dagbasi, M., and C. E. Turner. "Serendipity and the three point bend test." International Journal of Fracture 42, no. 1 (January 1990): R15—R18. http://dx.doi.org/10.1007/bf00018619.
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Gurova, T., J. R. Teodòsio, J. M. A. Rebello, and V. Monin. "Variation of the residual stress state in a welded joint during plastic deformation in a 5.0%Cr and 0.5%Mo steel." Journal of Strain Analysis for Engineering Design 32, no. 6 (August 1, 1997): 455–59. http://dx.doi.org/10.1243/0309324971513553.
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The aim of the present work is to verify the variation of the initial residual compressive stress induced by shot-peening, during plastic deformation under uniaxial tension, in a steel with 5.0%Mo and 0.5%Cr, employing test pieces taken from a welded joint where, due to the welding process, there are regions with different mechanical properties (yield strength and tensile strength). The regions of the joint, the base metal, the heat-affected zone and the weld bead exhibited different behaviour. In the heat-affected zone the residual compressive stresses in the longitudinal direction changed to tensile stresses with 0.5-1 per cent plastic deformation. At 3 per cent the stresses attain a maximum tensile value, decreasing in an oscillating manner up to 6 per cent plastic deformation. Beyond this point the test pieces reached a constant tensile value until the fracture. The transverse residual stress values were also modified during the tensile test but no full stress relaxation was observed. Indeed, the initial compressive stress values changed under small applied plastic deformation and after 4 per cent plastic deformation they changed weakly until the test piece fracture. The weld bead was weakly deformed and no effective stress relaxation was observed. In both the longitudinal and the transverse directions, the residual compressive stresses are brought sharply from an initial value of — 470MPa to a minimum of — 250MPa for only 0.5 per cent plastic deformation. No further changes were observed until the fracture of the test piece.
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RENALDI, LUKY, SUGONDO HADIYOSO, and DADAN NUR RAMADAN. "Purwarupa Radar sebagai Pendeteksi Benda Diam menggunakan Ultrasonik." ELKOMIKA: Jurnal Teknik Energi Elektrik, Teknik Telekomunikasi, & Teknik Elektronika 6, no. 3 (October 18, 2018): 317. http://dx.doi.org/10.26760/elkomika.v6i3.317.
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ABSTRAKDeteksi keberadaan objek secara otomatis pada ruangan diperlukan ketika terdapat keterbatasan dalam melakukan penginderaan. Pemanfaatan sistem radar menjadi saah satu solusi untuk penginderaan objek. Pada paper ini, diimplementasikan prototipe radar menggunakan sensor ultrasonik, mikrokontroller Arduino UNO R3 dan motor servo. Sistem ini dirancang dengan tiga buah sensor ultrasonik dengan motor sebagai penggerak horizontal dan vertikal dalam sistem pemindainya. Sensor yang berjumlah tiga buah, diletakkan pada titik yang berbeda sehingga dapat membaca jarak, sudut dan ketinggian objek dari arah titik tersebut, hasil dari pengukuran objek ditampilkan pada PC melalui aplikasi pemograman GUI. Dari hasil pengujian, radar mampu mendeteksi objek antara 5 cm dari depan radar dengan jarak maksimum 30 cm dan diperoleh tingkat kesalahan pengukuran jarak dan ketinggian sebesar 1 - 2 cm sedangkan untuk sudut 1˚- 3˚.Kata kunci: Deteksi, Radar, Ultrasonik, Jarak, SudutABSTRACTAutomatic detection of objects in the room is required when there are limitations in the sensing. Utilization of radar system becomes one solution for sensing object. In this paper, we implemented a prototype radar using ultrasonic sensor, Arduino UNO R3 microcontroller and servo motor. The system is designed with three ultrasonic sensors with motors as horizontal and vertical drive in the scanning system. Three sensors are placed at different points so that they can read the distance, angle and height of the object from that point, the result of measuring the object displayed on the PC through the GUI programming application. From the test results, the radar is able to detect objects between 5 cm from the front of the radar with a maximum distance of 30 cm and obtained the error rate measurement of distance and altitude of 1 - 2 cm while for the angle of 1˚ - 3˚.Keywords: Detection, Radar, Ultrasonic, Distance, Angle
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Marur, Prabhakar R. "Dynamic analysis of one-point bend impact test." Engineering Fracture Mechanics 67, no. 1 (September 2000): 41–53. http://dx.doi.org/10.1016/s0013-7944(00)00035-7.
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AOKI, Shigeru, Kenji AMAYA, Yuuki ONISHI, and Takayuki MIZUTANI. "Numerical Simulation of One-Point-Bend Impact Test." Transactions of the Japan Society of Mechanical Engineers Series A 68, no. 670 (2002): 924–29. http://dx.doi.org/10.1299/kikaia.68.924.
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Lube, T., M. Manner, and R. Danzer. "THE MINIATURISATION OF THE 4-POINT-BEND TEST." Fatigue & Fracture of Engineering Materials & Structures 20, no. 11 (November 1997): 1605–16. http://dx.doi.org/10.1111/j.1460-2695.1997.tb01514.x.
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Doz, Graciela N., and Jorge D. Riera. "Influence of support friction on three-point bend test." International Journal of Pressure Vessels and Piping 51, no. 3 (January 1992): 373–80. http://dx.doi.org/10.1016/0308-0161(92)90108-r.
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Shetty, Santosh, and Tommi Reinikainen. "Three- and Four-Point Bend Testing for Electronic Packages." Journal of Electronic Packaging 125, no. 4 (December 1, 2003): 556–61. http://dx.doi.org/10.1115/1.1604158.
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This study demonstrates the application of three-point and four-point bending tests for evaluating the reliability of chip scale packages under curvature loads. A three-point bend test is conducted on 0.5-mm-pitch chip-scale packages (CSPs) mounted on FR4 (Flame Retardant) substrates. This test is simulated by using the finite element method and the results are calibrated experimentally to formulate a reliability model. A three-point bend scheme is an ideal choice for generating reliability models because multiple packages can be tested under multiple loads in a single test. This reliability model can be used to predict the durability of the packages in the real product under any printed wiring board (PWB) curvature loading conditions. A four-point bending simulation is also demonstrated on the test substrate. Four-point bending test is an ideal method for testing a larger sample size of packages under a particular predefined stress level. This paper describes the bending simulation and testing on packages in a generic sense. Due to the confidentiality of the test results, the package constructional details, material properties, and the actual test data have not been presented here.
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Crouch, B. A. "Finite element modeling of the three-point bend impact test." Computers & Structures 48, no. 1 (July 1993): 167–73. http://dx.doi.org/10.1016/0045-7949(93)90468-s.
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Alafiatayo, Akinola Adekoya, Kok-Song Lai, Ahmad Syahida, Maziah Mahmood, and Noor Azmi Shaharuddin. "Phytochemical Evaluation, Embryotoxicity, and Teratogenic Effects of Curcuma longa Extract on Zebrafish (Danio rerio)." Evidence-Based Complementary and Alternative Medicine 2019 (March 5, 2019): 1–10. http://dx.doi.org/10.1155/2019/3807207.
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Curcuma longa L. is a rhizome plant often used as traditional medicinal preparations in Southeast Asia. The dried powder is commonly known as cure-all herbal medicine with a wider spectrum of pharmaceutical activities. In spite of the widely reported therapeutic applications of C. longa, research on its safety and teratogenic effects on zebrafish embryos and larvae is still limited. Hence, this research aimed to assess the toxicity of C. longa extract on zebrafish. Using a reflux flask, methanol extract of C. longa was extracted and the identification and quantification of total flavonoids were carried out with HPLC. Twelve fertilized embryos were selected to test the embryotoxicity and teratogenicity at different concentration points. The embryos were exposed to the extract in the E3M medium while the control was only exposed to E3M and different developmental endpoints were recorded with the therapeutic index calculated using the ratio of LC50/EC50. C. longa extract was detected to be highly rich in flavonoids with catechin, epicatechin, and naringenin as the 3 most abundant with concentrations of 3,531.34, 688.70, and 523.83μg/mL, respectively. The toxicity effects were discovered to be dose-dependent at dosage above 62.50μg/mL, while, at 125.0μg/mL, mortality of embryos was observed and physical body deformities of larvae were recorded among the hatched embryos at higher concentrations. Teratogenic effect of the extract was severe at higher concentrations producing physical body deformities such as kink tail, bend trunk, and enlarged yolk sac edema. Finally, the therapeutic index (TI) values calculated were approximately the same for different concentration points tested. Overall, the result revealed that plants having therapeutic potential could also pose threats when consumed at higher doses especially on the embryos. Therefore, detailed toxicity analysis should be carried out on medicinal plants to ascertain their safety on the embryos and its development.