Internal Stress Energy Research Articles

KASSANDRA Model: Detecting Dangerous Traffic Conditions By Modeling Drivers’ Internal Stress Energy

KASSANDRA Model: Detecting Dangerous Traffic Conditions By Modeling Drivers’ Internal Stress Energy

Solid-solid phase transformation via internal stress-induced virtual melting: Additional confirmations

Recently, we predicted a mechanism of solid-solid phase transformation (PT) via virtual melting at 121K below the melting temperature. We report additional experimental and theoretical results for PTs among three polymorphs of the energetic material HMX, α, β, and δ that support this mechanism. In particular: (a) the predicted velocity of interface propagation for β→δ PT and overall kinetics of δ→β PT are in agreement with experiment; (b) the energy of internal stresses is sufficient to reduce the melting temperature from 520to400K for δ→β PT; (c) the nanocracking that appears during solidification does not change the PT thermodynamics and kinetics for the first and the second β↔δ PT cycles; (d) δ→β PT starts at a very small driving force; (e) δ→α and α→δ PTs do not occur above 400K and below 461K, respectively.

On a unified approach to the description of phase transitions and strain localization

Two contradictions are stated in the paper: (1) The standard approach to the description of the onset of strain localization (SL) cannot describe known results related to the onset of phase transition (PT) although PT can also be considered as a form of SL. (2) In the course of PT, traction continuity is violated across the phase interface. To remove tje contradictions, the concept of stress fluctuating across the discontinuity surface is introduced. The stress overcomes the energy barrier and restores the traction continuity. It is shown that the unified approach to the two types of instabilities can be found by a kinetic method only. A simplest macroscopic counterpart of the known microscopic kinetic method is considered. For SL, it results in a kinetic theory of surface damage, time-dependent behaviour and fracture at the stress smaller than the peak value of the stress-strain diagram. The classical description of SL can be obtained for vanishing velocity of damage accumulation, i.e. when the fluctuating stress is absent. The fluctuating stress is necessary for equilibrium PT. In the last part of the paper, the equilibrium PT is considered by taking into account both the energy of internal stresses and the threshold-type thermodynamical dissipative forcek. Known experimental results on the deformation of pseudoelastic material are described. A simple dependence ofk on the volume fraction of martensite and PT history is determined. A kinetic equation is suggested which includes the above thermodynamical description.

Effect of Internal Stresses on Thermodynamics of Heterophase Structures in Epitaxial Layers

ABSTRACTThe effect of the elastic energy of internal stresses in a system of coherent phases within an epitaxial layer is considered. The equilibrium two-phase layer has a transversely modulated structure with a modulation period dependent on the layer thickness. The phase diagrams for the phases in an epitaxial layer can differ qualitatively from standard phase diagrams, and this difference also depends on the layer thickness.

Internal Friction of Ferromagnetic Substance Due to Rotation of Spontaneous Magnetization

In ferromagnetic substance, the origin of internal friction under low stress amplitude has been considered to be due to two kinds of eddy current. The first named macroscopic eddy current was studied by Brown and its theoretically predicted contribution to internal friction was known to be consistent with the experimental data. But the second named microscopic eddy current has not yet been investigated except in demagnetized state. In this paper this loss is calculated as a function of magnetization assuming that magnetic anisotropy energy is negligibly small compared with the internal stress energy. The result shows that internal friction increases initially with increase of magnetization but decreases rapidly near the magnetic saturation. The experimental behavior of internal friction obtained previously can be qualitatively explained by this theoretical result.