Dmitry Sergeevich Lisovenko

This paper presents a numerical analysis of the biomechanical behavior of the abdominal aortic wall and aneurysm. The problem is considered in an axisymmetric formulation, where vascular wall deformation is caused by the hydrodynamic effects of pulsating blood flow, which is described using the Carreau model that takes into account the dependence of viscosity on shear rate. Finite element analysis is used to calculate the relationship between hemodynamic loads and the stress-strain state of the aorta. Particular attention is paid to how changes in the mechanical characteristics of the aneurysm affect on the distribution of local strains and stresses within it.

A series of experiments on the penetration of plate-shaped specimens of thermoplastic polyurethane (flexible TPU 95A plastic), manufactured using various 3D printing infilling patterns, by a rigid spherical striker were conducted. The ability of such specimens to resist penetration and reduce the kinetic energy of strikers at a speed of approximately 190 m/s and a temperature of 25°C was experimentally studied. Four standard 3D printer infilling patterns for continuous filling of a given volume with material were used in preparing the specimens: “line,” “triangle,” “gyroid,” and “cube.” For each pattern, the filling density of the specimens with material varied from 25 to 100 percent. For the selected experimental conditions, it was found that plate-shaped specimens of TPU 95A plastic, printed on a 3D printer using the continuous filling “line” pattern, best reduce the kinetic energy of the striker at the maximum filling density.

The ability of composite structures incorporating flexible metamaterials with a cell-based structure in the form of a convex or concave hexagon to mechanically resist penetration by a rigid spherical striker was experimentally studied. In some experiments, solid layered samples with layers having different internal structures were penetrated. In other cases, the penetrated samples consisted of separate, unconnected layers. The samples were 3D-printed from flexible TPU 95A plastic (thermoplastic polyurethane) and represented metamaterials with various mechanical properties, including auxetic ones. The prepared barriers, similar in total mass, differed in the sequence of laying solid or separate layers and were compared for their ability to reduce the kinetic energy of strikers at a speed of approximately 190 m/s and a temperature of 25°C. Under the chosen experimental conditions, it was found that separate layers better reduce the kinetic energy of the striker. The most efficient order of laying layers in barriers was also determined.

Экспериментально исследовалось сопротивление образцов ауксетических метаматериалов, изготовленных на 3D-принтере из гибкого термопластичного полиуретана (TPU 95A пластика) на основе ячейки в виде вогнутого шестиугольника (метаматериалов с отрицательным коэффициентом Пуассона), пробиванию по нормали жестким сферическим ударником. Были подготовлены образцы, внутренняя структура которых отличались углом поворота (0, 30, 45, 60 или 90 градусов) относительно вертикальной оси. Образцы сравнивались по способности снижать кинетическую энергию ударников на скорости около 190 м/c при температурах 5, 16, 25 и 35◦С. Было установлено, что в рассмотренном диапазоне температур образцы наиболее эффективно сопротивляются пробиванию ударником при 25◦С. При этом для всех температур наибольшее сопротивление характерно для ауксетических метаматериалов из термопластичного полиуретана, с развернутой на 90 градусов структурой. The resistance of auxetic metamaterial samples to normal penetration by a rigid spherical impactor was experimentally investigated. The samples were made on a 3D printer from thermoplastic polyurethane (TPU 95A plastic) based on a cell in the form of a concave hexagon, which has a negative Poisson’s ratio. The internal structure of the manufactured samples differed in the angle of rotation (0, 30, 45, 60 or 90 degrees) relative to the vertical axis. The samples were compared in terms of their ability to reduce the kinetic energy of the impactors at a velocity of about 190 m/s at temperatures of 5, 16, 25, and 35◦С. It was found that in the considered temperature range, the samples most effectively resist penetration by an impactor at 25◦C. At the same time, for all temperatures, the greatest resistance is characteristic of auxetic metamaterials made of thermoplastic polyurethane, with a 90-degree unfolded structure.

The article discusses the longitudinal tension of two-layered plates of orthorhombic crystals. Expressions for effective Young’s moduli and Poisson’s ratios for different loading directions are obtained. With use of available experimental data on the elasticity constants, variability of effective elastic properties of plates is analyzed for all possible combinations of orthorhombic crystals. Plates with effective Young’s modulus greater than Young’s moduli of the layers and plates with a negative effective Poisson’s ratio are identified.

An Erratum to this paper has been published: https://doi.org/10.1134/S0025654425010017

An review of the temperature dependences of the elasticity characteristics of cubic crystals of simple substances is presented. It is shown that the general trend is a decrease in elastic moduli E, G, and B with temperature due to the weakening of interatomic bonds caused by thermal expansion of the crystal lattice. However, there are also anomalous dependencies, such as an increase in the shear modulus G with temperature, observed for BCC crystals of vanadium V, niobium Nb, tantalum Ta, and FCC crystals of palladium Pd, platinum Pt. A common feature for the cubic crystals considered, except for BCC chromium Cr, is an increase in Poisson’s ratio ν with temperature. The factor of elastic anisotropy A also shows a general upward trend, but for some crystals, BCC V, Nb, Ta, and FCC Al, local minima are observed, and for BCC Cr and FCC Pd, maxima are observed.