A constitutive model of human dermis skin incorporating different collagen fiber families

Skin tissue is a complex heterogeneous material abundant with fibers. Various models capturing its anisotropy, nonlinearity, viscoelasticity have been developed. However, the existence of multiple fiber families and the differences among them have been largely ignored. Furthermore, inhomogeneous deformation over the thickness is observed in the skin under shear deformation, which the traditional skin models do not predict. In this paper, we propose that two fiber families with distinct mechanical and structural properties exist in the skin within the framework of a general structure tensor-based constitutive strain energy model. Our constitutive model considers distinct properties of fiber families and the consequent inhomogeneous deformation in the skin, showing good agreement with in vivo measurements of human face skin.

Invariant submodel of rank 1 and two families of exact solutions of gas dynamics equations with an equation of state of the special form

In this article, the gas dynamics equations with an equation of state of the special form are considered.The equation of state is the pressure which is equal to the sum of two functions, with one being a function of a density, and the other one being a function of an entropy. The system of equations is invariant under the action of 12-parameter transformations group. For three-dimensional subalgebra 3.32 of the 12-dimensional Lie algebra invariants are calculated, an invariant submodel of rank 1 is constructed, and two families of exact solutions are obtained. The obtained solutions specify the motion of particles in space with a linear velocity field with inhomogeneous deformation. The first family of solutions has two moments of time of particles collapse. The second family of solutions has one moment of time of particles collapse on the plane. In the simplest case of second family of solutions, a surface consisting of particle trajectories is constructed.

Torsional Fatigue Life Prediction of 30CrMnSiNi2A Based on Meso-Inhomogeneous Deformation

In this paper, torsional fatigue failure of 30CrMnSiNi2A steel which exhibited non-Masing behavior was studied under different constant shear strain amplitudes, using thin-walled tubular specimens. The relationship between shear fatigue and the evolution of meso-deformation inhomogeneity and the prediction method of the torsional fatigue life curve were investigated. Shear fatigue of the material under constant amplitude was researched by numerical simulation with reference to tests, by using crystal plasticity of polycrystalline representative volume element (RVE) as the material model. Considering the non-Masing behavior of material, when determining the parameter values of the crystal plasticity model the correlation between these parameters and strain amplitude was taken into account. The meso-deformation inhomogeneity with increments in the number of cycles was characterized by using the statistical shear strain standard deviation of RVE as the basic parameter. Considering the effect of strain amplitude on fatigue damage, ratio cycle peak stress/yield stress was taken as the weight to measure the torsional fatigue damage and an improved fatigue indicator parameter (FIP) to measure the inhomogeneous deformation of the material was proposed. The torsional fatigue life curve of 30CrMnSiNi2A steel was predicted by the critical value of the FIP and then the result was confirmed.

Релаксация поляризации при статическом прямом флексоэлектрическом эффекте в монокристалле SrTiO-=SUB=-3-=/SUB=-

The results of a study of the dielectric polarization induced by spherical bending of thin single-crystal SrTiO3 plates are presented, and the flexoelectric coefficients are estimated. The processes of relaxation of inhomogeneous deformation and induced polarization are investigated.

Influence of the train load on the stability of the subgrade at the speed of movement

The article deals with the vibration of the subgrade soil and for the sections of the sloping terrain of the location of the subgrade calculation methods. In the calculations, we use the finite element method, the advantages of which are the simplicity of obtaining systems of resolving equations and the possibility of thickening the grid of elements and taking into account the inhomogeneous deformation and density properties of the soil material. The stress-strain state caused by structural changes in the subgrade during high-speed train traffic is determined. It also determines the dependence of the increase in the stress in the embankment of the subgrade on its height during high-speed train traffic, the dependence of the stress in the embankment of the subgrade on its width during high-speed train traffic, and the dependence of the stress in the slopes of the notch its depth.