Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 3 of 3
Full-Text Articles in Mechanical Engineering
Melt-Dispersion Mechanism For Fast Reaction Of Aluminum Particles: Extension For Micron Scale Particles And Fluorination, Valery I. Levitas, Michelle L. Pantoya, Kyle W. Watson
Melt-Dispersion Mechanism For Fast Reaction Of Aluminum Particles: Extension For Micron Scale Particles And Fluorination, Valery I. Levitas, Michelle L. Pantoya, Kyle W. Watson
Valery I. Levitas
The theoretically predicted relationship for the relative flame rate versus relative particle size based on the melt dispersion mechanism (MDM), which was previously confirmed for oxidation of 40–120nm diameter aluminum particles, is found to be in agreement with experiments for 1–3μm diameter Al particles and fluorination. The main physical parameters for MDM (pressure in molten particle, cavitation threshold, and nanoclusters’ velocity) have been estimated for micron scale particles. The results suggest parameters that could be controlled during particle synthesis that would enable micron scale Al particles to react and achieve the performance of nanoscale Al particles.
Melt Dispersion Versus Diffusive Oxidation Mechanism For Aluminum Nanoparticles: Critical Experiments And Controlling Parameters, Valery I. Levitas, Michelle L. Pantoya, Birce Dikici
Melt Dispersion Versus Diffusive Oxidation Mechanism For Aluminum Nanoparticles: Critical Experiments And Controlling Parameters, Valery I. Levitas, Michelle L. Pantoya, Birce Dikici
Valery I. Levitas
Critical experiments were performed on Al and MoO3 thermites. The diameter and alumina shell thickness of the Alnanoparticles were varied, and flame propagation velocities were measured. The results strongly support the melt-dispersion mechanism and contradict the diffusionoxidation mechanism. The parameters that control the oxidation rate and flame velocity are justified and directions for the synthesis of Alnanoparticles (which are opposite to the current directions based on diffusionoxidation) are suggested. An equation for the flame velocity versus Alnanoparticle geometrical parameters, thermomechanical properties, and synthesis parameters is formulated.
Finite Element Modeling Of Dynamics Of Martensitic Phase Transitions, Alexander V. Idesman, Joon Yeoun Cho, Valery I. Levitas
Finite Element Modeling Of Dynamics Of Martensitic Phase Transitions, Alexander V. Idesman, Joon Yeoun Cho, Valery I. Levitas
Valery I. Levitas
A finite element approach is suggested for the modeling of the dynamics of multivariant martensitic phase transitions (PTs) in elasticmaterials at the nanoscale in the three dimensional (3D) case. The model consists of a coupled system of the Ginzburg–Landau equations for transformation strain-related order parameters and dynamic elasticity equations. Thermodynamic potential [V. Levitas and D. Preston, Phys. Rev. B66, 134206 (2002)] that captures the main features of macroscopic stress-strain curves is used. The evolution of multivariant microstructure in a 3D specimen for cubic to tetragonal PT in a NiAl alloy is modeled with dynamic and static formulations. The numerical results …