125 research outputs found
Dynamic Shear Deformation and Failure of Ti-6Al-4V and Ti-5Al-5Mo-5V-1Cr-1Fe Alloys
No full textTo study the dynamic shear deformation and failure properties of Ti-6Al-4V (Ti-64) alloy and Ti-5Al-5Mo-5V-1Cr-1Fe (Ti-55511) alloy, a series of forced shear tests on flat hat shaped (FHS) specimens for the two investigated materials was performed using a split Hopkinson pressure bar setup. The evolution of shear deformation was monitored by an ultra-high-speed camera (Kirana-05M). Localized shear band is induced in the two investigated materials under forced shear tests. Our results indicate that severe strain localization (adiabatic shear) is accompanied by a loss in the load carrying capacity, i.e., by a sudden drop in loading. Three distinct stages can be identified using a digital image correlation technique for accurate shear strain measurement. The microstructural analysis reveals that the dynamic failure mechanisms for Ti-64 and Ti-55511 alloys within the shear band are of a cohesive and adhesive nature, respectively
Comparative Study of the Dynamic Fracture Toughness Determination of Brittle Materials Using the Kolsky-Hopkinson Bar Machine
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Numerical and Experimental Studies on the Explosive Welding of Tungsten Foil to Copper
No full textThis work verifies that the W foil could be successfully welded on Cu through conventional explosive welding, without any cracks. The microstructure was observed through scanning electron microscopy (SEM), optical microscopy and energy-dispersive X-ray spectrometry (EDS). The W/Cu interface exhibited a wavy morphology, and no intermetallic or transition layer was observed. The wavy interface formation, as well as the distributions of temperature, pressure and plastic strain at the interface were studied through numerical simulation with Smoothed Particle Hydrodynamics (SPH). The welding mechanism of W/Cu was analyzed according to the numerical results and experimental observation, which was in accordance with the indentation mechanism proposed by Bahrani
Preparation and Performance of Mo/Cu/Fe Multi-Layer Composite Coating with Staggered Spatial Structure by Electro-Explosive Spraying Technology
No full textIn the present study, electro-explosive spraying technology was used to prepare a multi-layer composite coating with a staggered spatial structure on a 45 steel substrate, and the mechanical properties and wear behavior of the coating were studied. The composite coating was prepared by spraying Mo as the bonding layer, then spraying high-carbon steel and aluminum bronze alternately as a functional coating. The cross-sectional morphology, surface morphology and the properties of the coating were analyzed with a scanning electron microscope (SEM), energy dispersive spectrometer (EDS), electron backscattered diffraction (EBSD) and a 3D profilometer. The bonding strength, friction and wear resistance of the coating were studied by the bonding strength experiment and by the friction and wear experiment. The results showed that it is feasible to prepare a composite coating with a sponge-like spatial structure with electro-explosive technology. There was metallurgical bonding as well as mechanical bonding between the adjacent coating layers. The composite coating had the advantages of uniform thickness, high compactness, high bonding strength and good wear resistance
Elastic constants characterization on graphite at 500°C by the virtual fields method
No full textAbstractIn this paper the elastic constants of graphite at elevated temperature were experimentally investigated by using the virtual fields method (VFM). A new method was presented for the characterization of mechanical properties at elevated temperature. The three-point bending tests were performed on graphite materials by an universal testing machine equipped with heating furnace. Based on the heterogeneous deformation fields measured by the digital image correlation (DIC) technique, the elastic constants were then extracted by using VFM. The measurement results of the elastic constants at 500°C were obtained. The effect on the experimental results was also analyzed. The successful results verify the feasibility of using the proposed method to measure the properties of graphite at high temperature, and the proposed method is believed to have a good potential for further applications
Synthesis of N-Doped Few-Layer Graphene through Shock-Induced Carbon Fixation from CO2
No full textIn this study, graphene and N-doped graphene nanosheets were synthesized through the shock-induced reduction of CO2 using a cylindrical shock-loading apparatus. The mixture of solid CO2 and Mg powder was filled in the pre-cooled sample tube and then impacted by a shock-driven cylindrical flyer tube. The impact generated a shockwave that propagated into the mixed precursor, inducing a chemical reaction between CO2 and Mg at a high shock pressure and high shock temperature. The recovered black powders were characterized via various techniques, confirming the presences of few-layer graphene. The mechanism is carefully shown to be that CO2 was reduced by Mg to form few-layer graphene under shock-induced high pressure and high temperature. By adding carbamide as an N source, this synthetic route was also applied to synthesize N-doped graphene nanosheets. Moreover, the yield and mass of the graphene materials in this study are up to 40% and 0.5 g, respectively. This study showed an efficient and easy-to-scale-up route to prepare few-layer graphene and N-doped few-layer graphene through shock synthesis
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