An urgent task in creating and using composite materials is the assessment and prediction of their performance properties and reliability. Currently, when studying the reliability of the materials, there is little experimental data, mathematical descriptions, and models for both probabilistic and deterministic methods to assess reliability. Based on the obtained experimental data, this article discusses the development of a methodology for predicting reliability. The article also proposes a statistical model for assessing reliability by the criterion of the structural strength of products made of polymer composite materials. The characteristics of the reliability changes in the materials when in operation are presented. The calculation allowed obtaining graphs showing the dispersion and statistical variability of the characteristics of polypropylene-based polymeric materials at the design, production, and operation stages of the product life cycle. The computational experimental results for determining the influence of the shape of inclusions and mass on the mechanical properties of a polymer composite material aimed at improving the strength characteristics of the products are presented. Based on a computational experiment in the MSC Digimat MF nonlinear solver, equations are provided to demonstrate the regression dependence of the strength of a part made of a polymer composite material on technological factors.
The presence of burrs on parts is not allowed in high-tech industries; there is a tendency to improve accuracy and quality and to reduce overall dimensions. A high proportion of operations are aimed at removing burrs in the labor intensity of release. Thermal pulse deburring machines are being developed and are applicable for deburring small-sized high-precision parts while providing additional processing conditions. A significant part of the electronic component base—coaxial radio components—is produced from beryllium bronze and the 29 NK alloy. It is not possible to prevent burr formation when cutting these materials. The conditions for deburring by the thermal pulse method are established in compliance with the requirements for deviations in the geometry of parts, for surface roughness and for ensuring maximum processing performance. These are restrictions on the thickness of the burr root, a variant of the arrangement of parts in the chamber of thermal impulse installation, which ensures the prevention of damage to parts during processing. Additionally, it provides access to a combustible mixture of all the surfaces of the parts; there is also a pressure value of the combustible mixture, depending on the characteristics of the thermal pulse installation, the total area of the treated surface, and the thermal conductivity of the materials for workpieces.
The application of multi-criteria optimization to two-carrier two-speed planetary gear trains is outlined in this paper. In order to determine the mathematical model of multi-criteria optimization variables, the objective functions and conditions must be determined first. Two-carrier two-speed planetary gear trains with brakes on coupled shafts are analyzed in this paper. The mathematical model covers the determination of the set of the Pareto optimal solutions as well as the method for selecting an optimal solution from this set. A numerical example is provided to illustrate the procedure in which the optimal two-speed planetary gear train is selected and defined by design parameters.
Rotary machines just like other complex technical devices, are the subject to vibrations that can lead to harmful effects during operation, and sometimes to destruction of individual elements, for example, reference nodes . The main source of vibration in such machines is a rotating element - the rotor, to which the centrifugal forces act in presence of shell elements or their residual imbalance. This is the main and inevitable type of vibration of any rotary machine. The unbalanced rotor always oscillates with the reference frequency, that is, the rotation velocity. In this case, the resulting centrifugal forces can cause not only vertical and horizontal vibrations, but also, under certain conditions, axial vibrations. The analysis of the dynamic behavior of the rotor under the influence of these forces should be carried out to any rotary machine both as at the design and operational stages, and so in case of operational accidents. The purpose of this work is to determine the main dynamic parameters and characteristics of the rotor of a centrifugal pump, taking into account the shell elements, determination of critical rotation velocities and the derivation of results in the form of the Campbell diagram with visualization of the rotor motion paths to determine the danger of resonance modes. To achieve this goal, the NASTRAN engineering analysis system of the standardized DMAP procedure "Rotodynamics" was used. The rotor was modeled as a shaft of piecewise constant cross section with shell elements modeled in the form of concentrated masses with inertia of rotation. In the article the results of calculations of two design schemes of a rotor of the pump with fastening the end of a shaft at a guide support, in the form of a caprolon sleeve and at a bearing support are given.
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