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Том 74, № 2 (2019)
- Год: 2019
- Статей: 6
- URL: https://journals.rcsi.science/0027-1330/issue/view/10035
Article
Procedure to Experimentally Estimate the Long-Term Strength of Polymer Materials Using the Test Results for Ring Specimens
Аннотация
A number of results obtained during the numerical finite element analysis of a procedure to test the ring specimens of polymer materials under internal pressure are discussed. The internal pressure is produced by the compression of an inset made of an incompressible material in the cavity of the specimen under test. The analysis is performed for the ring polyarylate specimens. The stress distributions in the specimen are obtained under constant load. It is shown that the stress distribution in the cross section of the specimen is not uniform for this type of loading. The effect of the elastic modulus and Poisson’s ratio of the loading inset on the tensile stresses in the specimen is studied. It is also shown that it is possible to use the maximum stress value or the stress intensity to estimate the long-term strength of polymer rings. The numerical results are used to estimate the durability of polyarylate sealing rings obtained by pressure casting at various temperature values. The experimental dependencies of time before fracture are given as functions of the maximum stress for the polymer specimens manufactured at the temperatures equal to 310 and 350° C. A new exponential dependence is proposed to approximate the experimental curves.
29-35
Fatigue Fracture of Metals under Complex Stress State with Consideration of Structural Changes
Аннотация
A phenomenological model of brittle fatigue fracture in metals and alloys is discussed in the case of proportional (simple) loading. The model is formulated in the framework of the physico-mechanical approach as a system of hypotheses concerning the probability of defect evolution at various scale-structural levels, such as micro- and macrocracks. The described constitutive relations are based on this model. A number of fatigue curves are obtained for various limit states of metals.
36-40
Brief Communications
Arrangement of Wave Propulsors on a Ship
Аннотация
A brief historical review of creating the ecological wave propulsors mounted on ships is presented. A particular attention is given to the arrangement of such devices. Experimental data on model tests concerning the positioning of wave propulsors on a ship to increase their efficiency are discussed.
41-43
Numerical Experiments for the Case of Acceleration of a Body of Revolution
Аннотация
Reducing the aerodynamic drag of bodies of revolution at supersonic speeds due to the creation of a bottom thrust is an important subject of aeromechanics. In the framework of this problem, it is proposed to perform numerical experiments on a model with a detachable bottom. It is assumed that the detachable bottom is affected by the main air flow jets separating from the surface of the body of revolution. The gas is reflected from the bottom and acts on the body of revolution, creating a bottom thrust and accelerating it.
44-46
Three-Wave Resonance in a Two-Dimensional Stationary Problem of Gas Dynamics
Аннотация
The isentropic motion of a perfect ideal gas on a constant homogeneous supersonic background is considered. A two-dimensional stationary potential problem of gas dynamics is solved to study the interaction of three traveling waves whose amplitudes and phases are slowly varying in the direction of the background flow in the case when the sum of “harmonic” phases is exactly equal to zero. The equations of amplitude and phase variation are derived and their solutions are analyzed analytically. The question of what boundary conditions should be satisfied is discussed.
47-50
Ejection of a Liquid from a Vessel by a Plane Wall Jet
Аннотация
The process of ejecting a liquid from a finite-size vessel with an inclined wall by a submerged wall jet is considered. The character of flows arising in the vessel and the intensity of liquid ejection are numerically studied for various values of jet thickness and velocity. The numerical method in use is verified by a number of experiments. It is found that, at the last stages of ejection, in the liquid it is possible to observe the multiple formation of vortex regions with gas inclusions at their centers. The dependence of the time necessary to empty the vessel completely on the jet thickness and velocity is also found.
51-53