Bonding features and associated mechanisms in kinetic sprayed titanium coatings

Numerical simulations of shock wave propagation through discretely represented powder mixtures were performed to investigate the characteristics of deformation and mixing in the Ni+Al system. The initial particle arrangements and morphologies were imported from experimentally obtained micrographs of powder mixtures pressed at densities in the range of 45%–80% of the theoretical maximum density (TMD). Simulations were performed using these imported micrographs for each density compact subjected to driver velocities (Up) of 0.5, 0.75, and 1km∕s, and the resulting shock velocity (Us) was used to construct the Us-Up equation of state. The simulated equation of state for the 60% TMD mixture was validated by matching results obtained from previous gas-gun experiments. The details of shock wave propagation through the Ni+Al powder mixtures were explored on several scales. It is shown that the shock compression of mixtures of powders of dissimilar densities and strength is associated with heterogeneous deformatio...

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Discrete particle simulation of shock wave propagation in a binary Ni+Al powder mixture

Mesoscale simulation of the configuration-dependent shock-compression response of Ni + Al powder mixtures

A Lagrangian finite and discrete element technique, combined with a finite deformation, thermo-elastic-viscoplastic, and stick-slip friction theory, is used to computationally examine volumetric and surface dissipation within the meso-structure of granular explosive (HMX, C4H8N8O8) induced by uniaxial deformation waves. Emphasis is placed on characterizing the fraction of mass heated to elevated temperature (referred to as hot-spot mass fraction) by quasi-steady waves due to plastic and friction work and its dependence on wave strength. Predictions for a large, randomly packed ensemble of HMX particles having a solid volume fraction of 0.85 and a mean diameter of 60 μm show that plastic work principally affects the average temperature, whereas friction work affects the high frequency, high-temperature fluctuations that are likely responsible for combustion initiation. Cumulative distributions for hot-spot mass within the wave indicate that most mass (~99.9%) is heated to approximately 330, 400, and 500 K by plastic work for impact speeds of 50, 250, and 500 m/s, respectively, with a small fraction (~0.001%) heated to 600, 1,100, and 1,400 K by friction work. The hot-spot mass fraction induced by plastic work is well described by a Gamma distribution, though significant departures occur in the high-temperature end of the distribution due to friction work, even at higher impact speeds. Consequently, it is not possible to describe hot-spot mass fraction curves by a single classical distribution function. Implications of the predicted hot-spot mass fraction on granular HMX combustion are discussed.

Mesoscale analysis of volumetric and surface dissipation in granular explosive induced by uniaxial deformation waves

A combined experimental and numerical approach to the kinetics of mechanically induced phase transformations

This article presents numerical studies on the deformation of particles during dynamic compaction of metal powders. The analysis of the process is based on a micromechanics approach using multiple particle configurations. The material considered is elastoviscoplastic with interparticle friction. Two-dimensional studies on particles in close packed arrangement were carried out using plane strain conditions for deformation and thermal response. The finite element method using an explicit dynamic analysis procedure was used for the simulations. The influence of speed of compaction, strain hardening, strain rate dependency, interparticle friction and size of the powder particles on the final shape and temperature variations within the particles were analyzed. The studies offer useful information on the shape and temperature variations within the particles. The results provide a better understanding of the dynamic compaction process at the micromechanics level.

Simulation of dynamic compaction of metal powders

This paper investigates the use of a simple drop weight instrumented impact loading facility to produce metal powder compacts with better qualities than attained by the conventional means. Experiments were performed on Fe powder, Fe-C-Cu-Mn powder mix, and Cu-Zn powder mix at different height to diameter ratios and compacted at different energies. The overall density, density variation within the compact, dimensional accuracy, and microstructure were compared with quasistatic specimens compacted using conventional hydraulic press. The results showed that the dynamic compaction specimens attained better densification and dimensional accuracy than quasistatic compaction specimens.

Investigations on dynamic compaction of metal powders: Part 1: Experimental

Simulation of Surface Densification of PM Gears

Numerical investigations of pyramid indentation on powder compacts

Plastics are widely utilised materials that play an important part in everyday life. The use of this nonbiodegradable commodity is fast expanding, as is the accumulation of plastic garbage. Due to the paucity of landfills, disposing of waste plastic is a severe challenge in the current circumstances. Poor disposal procedures have made them a major source of environmental and natural disasters. The goal of this study is to determine the viability of employing recycled High Density Polyethylene (HDPE) and recycled PolyEthylene Terephthalate (PET) as bitumen modifiers to improve the properties of the resulting binder for use in Bituminous Concrete (BC) mix building. The modified mix was made by replacing part of the bitumen binder with varied quantities of HDPE (4%, 6%, respectively) and PET (6 percent , 8 percent ). The dry technique, i.e. plastic coating of aggregates, was used to combine HDPE and PET. The Marshall Stability of HDPE and PET modified bituminous concrete is significantly increased, up to 52 percent. The addition of HDPE and PET in the mix has a brilliant good influence on the qualities of BC mix, and it can increase the re-use of plastic waste, according to test results.

D. Roshan Kumar

Papers

Simulation of dynamic compaction of metal powders

Investigations on dynamic compaction of metal powders: Part 1: Experimental

Simulation of Surface Densification of PM Gears

Numerical investigations of pyramid indentation on powder compacts

Effect of copolymer additives on the binding properties of bitumen mix