Microstructure and strength of metals processed by severe plastic deformation

The microstructure of f.c.c. metals (Al, Cu, Ni) and alloys (Al-Mg) processed by severe plastic deformation (SPD) methods is studied by X-ray diffraction line profile analysis. It is shown that the crystallite size and the dislocation density saturate with increasing strain. Furthermore, the Mg addition promotes efficiently a reduction of the crystallite size and an increase of the dislocation density in Al during the SPD process. The yield strength correlates well with that calculated from the dislocation density using the Taylor equation, thereby indicating that the main strengthening mechanism in both pure metals and alloys is the interaction between dislocations

Model predictive direct power control of three-level T-type inverter-fed doubly-fed induction generator for wind energy system

The paper proposes a simplified direct power control strategy of a doubly-fed induction generator fed by a three-level T-type inverter based on finite control set model predictive control. A mathematical model based on grid voltage orientation was employed to determine the predictive values of the stator flux, rotor current, and capacitor voltages for all feasible rotor-side inverter output voltages. The active and reactive powers were calculated by using the grid voltage and the rotor current. A cost function was applied to track the active and reactive powers, maintain the balance of capacitor voltages, and reduce the common-mode voltage. The best switching control input was chosen by minimizing the cost function and implemented to the inverter. Different operating conditions of wind turbine systems were studied with Matlab/Simulink environment. The simulation results validate the improved performance of the proposed method compared with the classical control in terms of transient response and steady-state conditions

Observations on multiple mating flights of Apis dorsata queens

This observation is aimed at providing information for a reasonable comparative study on reproductive biology among the honeybee species. The research was carried out in 1996 in the submerged Melaleuca forest of southern Vietnam, where low-nesting colonies on man-made supports, rafters, allowed us to make detailed observations on the queens. Flights of six newly emerged queens were observed and after their final mating flights, queens were dissected to count the sperm number. The five investigated queens took their first flights 6 ± 1 (mean ± SD) days after emergence. Four queens took orientation flights of less than 3 min. One queen flew to mate without any orientation flight. Mating flights happened around sunset and lasted 15.4 ± 4.3 (n = 14) min. A queen undertook two to four mating flights and after fully mating, she had 5.5 ± 0.9 (n = 5) million sperm in her spermatheca. This study indicated the extreme polyandry in A. dorsata. © Inra/DIB/AGIB/Elsevier, Pari

Ultra high Performance Fiber Reinforced Concrete Panel Subjected to Severe Blast Loading

Experimental studies play a crucial role in shedding light on the dynamic behaviour of structures under blast loading. However, high costs and complicated technical requirements, particularly for full-scale structures, are still huge disadvantages to conduct such a series of tests. Hence, the finite element method is much needed to provide supplementary information to previous experiments and to enable further parametric studies without testing. This article presents a numerical investigation carried out to understand the behaviour of ultra high performance fiber reinforced concrete (UHPFRC) panels under severe blast loading. The authors designed a subroutine with eight numbers of solution-dependent state variables, 32 mechanical constants, integrated with the Abaqus program to analyze the dynamic behaviour of UHPFRC against multiple blast impacts, using the Johnson-Holmquist 2 damage model incorporating both the damage and residual strength of the material. The subroutine was validated by comparing the simulation results with test results. For the purpose of estimating the structural response of the UHPFRC panel subjected to blast loading, other studying scenarios were considered by varying input parameters, including the thickness of the panel, stand-off distance, and steel reinforcement bar volume. The variations in deflection, strain, and damage of the UHPFRC panel, as well as the steel reinforcement strain, were also evaluated. Through important obtained results, the UHPFRC panel is strongly recommended for a protective barrier installed in the vicinity of critical infrastructure against severe blast loadin

EFFECTS OF pH OF TEOS SOLUTION ON MORPHOLOGY, THERMAL STABILITY AND MECHANICAL PROPERTIES OF EVA/SILICA NANOCOMPOSITES PREPARED BY SOL-GEL METHOD

Ethylene-vinyl acetate copolymer/silica nanocomposites (EVA/silica) were prepared by mixing EVA solutions and tetraethylorthosilicate (TEOS) solutions. Silica particles were formed through sol-gel mechanism with the aid of hydrochloric acid catalyst and dispersed in EVA matrix. The pH of TEOS solutions was controlled from 1 to 6. The influence of pH on formation of silica in EVA matrix, as well as morphology, thermal stability of the nanocomposites were characterized by using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and field emission scanning electron microscopy (FESEM). The FTIR spectra of the nanocomposites clearly indicated the presence of silica in EVA matrix, the shifts of Si-O stretching vibration in the nanocomposites in comparison with pure silica were also observed. This can be explained by hydrogen bonding between SiOH groups of the silica and carbonyl groups of vinyl acetate units in EVA. The TGA results of the nanocomposites showed that silica could improve thermal stability of EVA. Comparing preparation conditions at pH from 1 to 4, it is clear that at the lower pH the higher content of silica was formed in EVA matrix, 3.78; 3.70; 2.50 and 2.09 wt.% respectively. The FESEM images of the nanocomposites showed that nanoscale dispersion of silica was observed obviously at pH of 4 - 6, whereas during their preparation at pH of 1 - 3, the obtained silica particles formed mainly in microscale. The pH also affected on the mechanical properties (tensile strength, elongation at break) of EVA/silica nanocomposites. At pH of 1 - 3, the silica particles formed mainly in larger size, thereby they reduced the mechanical properties of EVA. At pH of 4 - 6, the nanosilica particles had significantly improved mechanical properties of EVA, particularly at pH of 4. The improvement of shear modulus of EVA/silica was also discussed

Mikroszerkezet karakterizációja röntgen vonalprofil analízis alapján = Characterization of microstructure by X-ray line profile analysis

A "" Mikroszerkezet karakterizációja röntgen vonalprofil analízis alapján"" c. T-046990, OTKA pályázat rövid szakmai összefoglalója, zárójelentés A deformációs anizotrópia jelenségét kihasználva részletes elméleti és kísérletes kutatásokat végeztünk a mikroszerkezet kvalitatív és kvantitatív karakterizációjára vonatkozóan köbös, hexagonális és ortorombos kristályrendszerekben a röntgen vonalprofil analízis módszerével. A földkéregben mintegy 100 km-es mélységben fekvő ortorombos MgSiO3 perovszkitokat szimuláló mintát állítottunk elő magas hőmérsékletű nagynyomású présben. Megállapítottuk, hogy csak és Burgers vektorú diszlokációk jönnek létre. 700 és 1000 K közötti hőmérsékleteken összenyomással deformált Ge egykristályokban helyfüggő mikrodiffrakcióval megállapítottuk, hogy a mikroszerkezet jelentős fluktuációkat mutat. [001], [011] és [111] textúrájú NiAl emlékező ötvözet mintákban meghatároztuk a különböző textúra komponensekhez tartozó kemény illetve puha krisztallit populációkban az aktív Burgers vektor típusokat valamint diszlokációsűrűségeket. Golyósmalomban őrölt alkáli földfém fluoridok krisztallitméret és diszlokációsűrűség meghatározása során felfedeztük, hogy pormintákban is létrejön röntgen optikai interferencia. Módszert dolgoztunk ki Burgers vektor típusok meghatározására hcp kristályokban. Kidolgoztuk a rétegződési hibák és ikerhatárok gyakoriságának meghatározási módszerét köbös kristályokban. A módszert számos esetben sikeresen alkalmaztuk. | ""Characterization of microstructure by X-ray line profile analysis"" Short summary of the T-046990, OTKA project, final report On the basis strain anisotropy detailed theoretical and experimental work has been carried out for the characterization of the microstructure in cubic, hexagonal and orthorhombic crystal structures by using the method of X-ray line profile analysis. A synthetic orthorhombic MgSiO3 perovskite was prepared the high temperature and pressure. We have found that only and type Burgers vectors are present in the deformed crystals. Ge single crystals were deformed by compression between 700 and 1000 K. Position sensitive microdiffraction has revealed that the deformed microstructure is strongly fluctuating on different length scales. NiAl shape memory alloys with [001], [011] and [111] textures were deformed by compression. We have determined the active Burgers vector types and dislocation densities in the different texture components for different grain orientation populations. Alkali-halide fluorides were ball milled to different extent. We have shown that X-ray optical interference can occur in nanocrystalline powder specimens. A method has been worked out to determine active Burgers vector types in hexagonal crystal systems, and the frequency of stacking faults and twin boundaries in cubic crystals. The methods have been applied successfully in several different cases

PREPARATION AND FTIR STUDIES OF PMMA/PVC POLYMER BLENDS, PVC-g-PMMA GRAFT COPOLYMERS AND EVALUATING GRAFT CONTENT

This study presents the qualitative and quantitative analyses of Fourier Transform Infrared (FTIR) spectra of poly(methyl methacrylate)/poly(vinyl chloride) blends (PMMA/PVC), as well as PVC-g-PMMA graft copolymers. Graft copolymerizations of methyl mathacrylate (MMA) onto PVC macromolecules were carried out mixture of cyclohexanone/N,N-dimethylformamide as solvents, dibenzoyl peroxide as initiator and nitrogen medium. FTIR spectra of PMMA/PVC blends showed that there were molecular interactions between C=O groups of PMMA and C-Cl groups of PVC. Assignments of infrared absorption bands for specific groups of PMMA/PVC blends have been contributed. Using regression method, linear calibration curve between PMMA mole content and peak areas of C=O groups in FTIR spectra of the blends has been found when C=O peak areas were multiplied by an appropriate factor. PMMA grafted content and total PMMA formed content in PVC-g-PMMA graft copolymers have been evaluated. The results showed that grafted PMMA content was increased since PVC was initiatly dechlorinated by NaOH solution. The grafted PMMA content and total formed PMMA content were 5.05 wt.% and 11.25 wt.% respectively when MMA monomers were grafted onto neat PVC and modified PVC molecules

Classification of cow’s behaviors based on 3-DoF accelerations from cow’s movements

Cow’s behavior classification helps people to monitor cow activities, thus the health and physiological periods of cows can be well tracked. To classify the behavior of cows, the data from the 3-axis acceleration sensor mounted on their neck is often used. Data acquisition and preprocessing of sensor data is required in this device. We acquire data from the 3-axis acceleration sensor mounted on the cows’neck and send to the microcontrollter. At the microcontroller, a proposed decision tree is applied in real-time manner to classify four important activities of the cows (standing, lying, feeding, and walking). Finally, the results can be sent to the server through the wireless transmission module. The test results confirm the reliability of the proposed device