Parametric study of the conditions of supershear crack propagation in brittle materials

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in AIP Conference Proceedings 1683, 020209 (2015) and may be found at https://doi.org/10.1063/1.4932899.The paper is devoted to the numerical analysis of the conditions of acceleration of dynamically propagating longitudinal shear cracks from sub-Rayleigh to intersonic/supershear velocities. We showed that an ability of the initial crack to propagate in supershear regime can be predicted with use of the empirically derived dependence of the geometrical criterion of sub-Raleigh-to-intersonic transition on material and crack parameters

Theoretical Study of the Conditions and the Mechanism of Shear Crack Acceleration towards the Longitudinal Wave Velocity

AbstractThe question about physically admissible velocity of dynamic crack growth is of significance to safety engineering as well as to earthquake dynamics. Recent researches including numerical simulations, experimental observations and the analysis of strong earthquakes have shown a possibility of propagation of shear cracks in supershear regime, namely at velocities comparable with dilatational wave speed. The present paper is devoted to the theoretical (numerical) study of some fundamental aspects of this problem. It is shown that development of a sub Raleigh shear crack is connected with a vortex traveling ahead of the crack tip at a shear wave velocity. The stress concentration area ahead of the crack tip revealed by different authors (Burridge, Andrews, Geubelle, Rosakis and others) is connected with this vortex. Acceleration of a shear crack towards the longitudinal wave velocity is concerned with formation of a daughter crack by the mechanism of shearing (the daughter crack is formed in the center of vortex). Analysis of sub Raleigh to intersonic transition has shown that development of shear cracks is self-similar and depends on dimensionless parameters

Theoretical study of peculiarities of unstable longitudinal shear crack growth in sub-Rayleigh and supershear regimes

In the paper we present the results of the theoretical study of some fundamental aspects of mode II crack propagation in conventional sub-Rayleigh regime and transition to intersonic regime. It is shown that development of a sub-Rayleigh shear crack is determined in many respects by elastic vortex traveling ahead of the crack tip at a shear wave velocity. Formation of such a vortex helps to better understand the well-known phenomenon of acceleration of a shear crack towards the longitudinal wave velocity. Simulation results have shown that due to self-similarity of shear crack propagation the conditions of sub-Rayleigh to intersonic transition depend on dimensionless material and crack parameters. Two key dimensionless parameters are proposed

A molecular dynamic study of charged nanofilm interaction with negative lipid bilayer

Hydrophobic and functionalized nanoparticles of different sizes and shapes have a various biomedical application, in particular anticancer therapy. It is known that charged nanoparticles may bind lipids and membrane proteins as well as cause lipid bilayer disruption. We have performed preliminary molecular dynamic simulations to investigate the effect of positively charged synthetic nanofilm, imitating a fragment of the two-dimensional folded AlOOH structure, on the POPE/POPG lipid membrane. It has been shown that the synthetic nanofilm with frozen coordinates tightens the membrane and binds lipid headgroups. Furthermore, the presence of the positively charged nanofilm perturbs the cation concentration in the near-surface membrane region

Adsorption of charged protein residues on an inorganic nanosheet: Computer simulation of LDH interaction with ion channel

Quasi-two-dimensional and hybrid nanomaterials based on layered double hydroxides (LDH), cationic clays, layered oxyhydroxides and hydroxides of metals possess large specific surface area and strong electrostatic properties with permanent or pH-dependent electric charge. Such nanomaterials may impact cellular electrostatics, changing the ion balance, pH and membrane potential. Selective ion adsorption/exchange may alter the transmembrane electrochemical gradient, disrupting potential-dependent cellular processes. Cellular proteins as a rule have charged residues which can be effectively adsorbed on the surface of layered hydroxide based nanomaterials. The aim of this study is to attempt to shed some light on the possibility and mechanisms of protein “adhesion” an LDH nanosheet and to propose a new direction in anticancer medicine, based on physical impact and strong electrostatics. An unbiased molecular dynamics simulation was performed and the combined process free energy estimation (COPFEE) approach was used

Molecular Level in Silico Studies for Oncology. Direct Models Review

The combination of therapy and diagnostics in one process "theranostics" is a trend in a modern medicine, especially in oncology. Such an approach requires development and usage of multifunctional hybrid nanoparticles with a hierarchical structure. Numerical methods and mathematical models play a significant role in the design of the hierarchical nanoparticles and allow looking inside the nanoscale mechanisms of agent-cell interactions. The current position of in silico approach in biomedicine and oncology is discussed. The review of the molecular level in silico studies in oncology, which are using the direct models, is presented

Two-Dimensional Al Hydroxide Interaction with Cancerous Cell Membrane Building Units: Complexed Free Energy and Orientation Analysis

The application of hierarchical nanoparticles based on metal hydroxides in biomedicine, including anticancer therapy and medical imaging, is a rapidly developing field. Low-dimensional aluminum oxyhydroxide nanomaterials (AlOOH-NM) are quite promising base to develop hybrid theranostic nano-agents with core-shell architecture, which is determined by AlOOH-NMs physicochemical properties such as: large specific surface area, pH-dependent charge, amphoteric behavior, high surface density of polar groups capable to form non-covalent bonds, low or null cytotoxicity and biocompatibility. Characterization of the system behavior within interface between NM and plasmatic membrane is crucial for the understanding of nano-agent-cell interaction. In the present work the complex in silico study including the free energy estimation and orientation analysis of phosphatidylcholine (POPC) and phosphatidylethanolamine (POPE) lipids interacting with AlOOH nanosheet was conducted to understand the effect of such nanomaterial on cancerous cell plasmatic membrane

Investigation of initiation conditions of relative displacements of the fault-block media units under vibration loading

On the basis of computer modeling by the method of movable cellular automata the theoretical investigation of initiation conditions of relative displacements along the interfaces of complex stressed geological media blocks in the complex intense condition under local vibrating loading has been performed. It is shown, that defining factors at formation of unstable shift on the interblock border of fracture-block geological environments are the relative value of shift stresses and also the frequency of vibrating loading, i. е. time of impulse energy allocation. Low in power, but long-continued loadings on influences on high-voltage borders of section are the most effective in respect to power inputs

On the role of scales in elastomer friction

The paper is devoted to a general analysis of friction of elastomers from the point of view of scales contributing to the force of friction. We argue that-contrary to the wide spread opinion-elastomer friction is not a multiscale phenomenon, but is governed mostly by the interplay of only two scales-the largest and the smallest scales of roughness of the contacting bodies. This is illustrated by analyzing the main ideas of the theory of elastomer friction based on the paradigm of Greenwood, Tabor and Grosch. The same conclusions can be obtained from the widely used contact theory proposed by Persson