Abstract: Energy absorption devices are being used to protect structures from severe damages and reduce injury to occupants during accidents. The integrated characteristics of crash absorption devices can be classified as high energy absorption capacity, light-weight, and cost-effective. One of the thin-walled structures which has drawn the attention of scientists is corrugated tube structure. In this paper, the effect of corrugation geometry on the crushing parameters of an aluminum corrugated tube is investigated. In this regard, different elliptical corrugation shapes were deemed and the compression response was numerically evaluated under lateral quasi-static loading. Finally, the crashworthiness parameters were extracted and compared to determine the influence of corrugation shape on the crashworthy response. Our results showed that using vertical elliptical corrugation decrease the densification point. Moreover, there is a gradual enhancement of mean crushing load by moving from the horizontal elliptical corrugations to the vertical ones. Also, by modifying of corrugation shape, the stress variation pattern changes, significantly.
Abstract: Stable zinc oxide nanoparticles were prepared by chemical process. Zinc oxide nanoparticles were synthesized using a modified method with zinc nitrate and sodium hydroxide at 60° C. The synthesized nanopowders were characterized in terms of chemical composition (EDS), structure FTIR and XRD, particle size and morphology by TEM. The XRD results confirm that ZnO nanoparticles were obtained with hexagonal arrangement (Wurtzite). The nanoparticles showed sizes between 10 to 30 nm and semispherical forms. The luminescent properties of the synthesized nanoparticles were measured in a photoluminescence assay on a Raman instrument. The samples were irradiated with two laser beams of different wavelengths. The application of the fingerprints on different surfaces was done using deferments surfaces.
Abstract: Friction stir processing (FSP) is a thermos-mechanical process for modifying the microstructural and material properties of metals. FSP also can be used for mechanical alloying and producing metal matrix composites. Due to creation of longitudinal cracks and tunneling cavities throughout the processing path, FSP of AZ91 is difficult and also sensitive to processing temperature. In this study, the effect of processing parameters such as the traverse and rotational speeds and the dimension of the tool pin on the temperature history experienced by material were investigated. Additionally, a minimum temperature required to produce a defect-free specimen was presented.
Abstract: With a pressure die casting process, one of the important factors affecting the quality of castings represented by porosity is plunger pressing velocity determines the regime die cavity filling and correct determination of dose mass of a molten metal required for one casting cycle. The mass is given by a total of the net mass of a casting, overflows, a gate system and a metal rest inside a filling chamber (the tablet height). As a rule, the tablet height represents the largest mass ratio regarding the waste metal. A correct determination of the tablet height is important from both economical and qualitative aspect of a pressure die casting process.
Abstract: The fabrication processes of nanomaterials adopt semiconductor manufacturing technology mostly, and restrain from mass production due to high vacuity, expensive equipment, and long cycle time. This research offers a relatively simple and convenient fabrication process to improve the manufacturing technology of nanowires. Starting with aluminum film of high purity, this research utilized anodizing to produce the array nanoporous mold, electrochemical deposition to inject ion-state metal, oxidation-reduction method to obtain metal nanowires, and annealing to result the oxidation of metal nanowires. The influence of substrate and oxidation layers was investigated with respect to parameters such as voltage, current, and time. In order to get the best control of array dispersion, diameters, and depth, the influence of temperature over the process is also investigated. A higher anodizing temperature was utilized to stabilize the fabrication process of the array nanoporous mold. The resulted metal nanowires were analyzed with X-ray diffraction, FE-SEM, and TEM, to inspect the morphology and crystallography. The observations are summarized. (a) The preferred orientation of nickel nanowires being annealed at the 600°C pure nitrogen is NiO(111). (b) As the oxidation temperature rises, NiO in pure oxygen or the atmosphere would transfer into Ni2O3 due to the size effect. Nickel nanowires in pure oxygen could oxidize into Ni2O3 at a lower temperature of 500°C. (c) Nickel nanowires both in pure oxygen and in the atmosphere would transfer stably into Ni2O3 at 900°C.