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Vol 74, No 1 (2019)
- Year: 2019
- Articles: 5
- URL: https://journals.rcsi.science/0027-1330/issue/view/10032
Article
1-8
Approaches to Modeling the Properties of Complex Structure Materials
Abstract
Some approaches to the axiomatic formulation of theoretical fundamentals in continuum mechanics are considered. The basic concepts, laws, and hypotheses in the classical theory of continuum mechanics and their modifications for its nonclassical versions are discussed. In the framework of the classical version of the rational theory, a number of axioms are proposed for the general theory of constitutive relations. For the media of nonclassical type, the approaches to axiomatic formulation are studied by the example of the rational mechanics of moment media (Cosserat continuum): some specific notions of bodies with their attributes and the forms of their interactions and motions are introduced, the appropriate generalizations of the main laws and hypotheses are given, and the general forms of constitutive relations are analyzed for arbitrary and small strains. The approaches to the construction of medium models are discussed in accordance with the method of mechanical modeling proposed by A. A. Il’yushin.
9-13
Stabilization of Steady Motions for Systems with Redundant Coordinates
Abstract
The vector-matrix Shulgin’s equations are used to stabilize the steady motions of mechanical systems with nonlinear geometric constraints in the case of incomplete information on the state. The momenta are introduced only for the cyclic coordinates that are not used to control. Three variants of the measurement vector are used to prove a theorem on the stabilization of control with the help of a part of the cyclic coordinates described by Lagrange variables. The control coefficients and the estimation system coefficients are specified by solving the corresponding Krasovskii linear-quadratic problem for a linear controlled subsystem without the critical variables corresponding to the redundant coordinates and to the introduced momenta. The stability of the complete closed nonlinear system is proved by reducing to a special Lyapunov case and by the application of the Malkin stability theorem in the case of time-varying perturbations.
14-19
Effect of a Laying Method for Various Weaving Types on the Protective Properties of Multilayer Fabric Barriers
Abstract
The effect of various weaving types for fabric composites on the low-speed (up to 350 m/s) penetration into multilayer fabric barriers made of aramid fibers is studied. The geometric properties of plain and twill weaves are taken into account on the basis of experimental data showing that the warp and weft threads may have different elastic and ultimate properties. Significant differences in the parameters of interlayer friction are also taken into account for the fabrics of various weave patterns. The results of full-scale experiments for the penetration into four-layer and ten-layer fabric barriers are used to verify the models of penetration into fabric barriers and to study the penetration into composite fabrics with various mutual arrangements of plain and 3/3 twill weaves. It is shown that some particular laying methods based on layer alternations can improve the protective properties of multilayer fabric barriers.
20-23
Calibration of Inertial Sensors in the Case of Varying Temperature
Abstract
The calibration of a strapdown inertial navigation system is considered in the case of varying temperature. A parameterized model of measurement errors is used to calibrate the inertial sensors. In addition to usual standard parameters, this model contains the coefficients in the temperature dependence. In the author’s previous publications, it is shown that it is possible to estimate these coefficients and the coefficients in the dependence describing the time derivative of temperature as well as the other parameters. The practical application of this author’s approach is based on the following: the time dependence of temperature is determined using the temperature sensors mounted on the navigation system under study. The determination of this derivative on the basis of the temperature sensors is not a trivial problem. In this paper we propose a function to approximate the readings of temperature sensors. The relation between this function and the model of thermal processes inside the navigation system is analyzed. This process is described by the heat conduction equation.
24-28