The modal analysis is considered as one of the lines of technical diagnostics for evaluating the quality of polymer composite materials (PCMs). It allows one to link the structure of modal characteristics of PCM element base in the amplitude-frequency domain. In the course of modal analysis, the complex construction of PCM as a heterogeneous material is transformed into a set of easy-to-understand independent systems with one degree of freedom. This structural approach is used to analyze the structure of PCM components. A laser is used to form an external action, with the help of which PCM components can form a wave field when vibrations pass through its thickness. Vibrations and deformations of PCM structural elements under a mechanical excitation are considered as the intrinsic vibration forms (vibration modes) of PCM elements -the filler and matrices. High-frequency laser actions extracts a constant wavefront, which is used for constructing an algorithm for recognition of the structure of PCM, including the detection of possible defects, such as changes in its density and various stratifications. To assess the technical condition of structural elements of PCM, a mathematical model was developed to assess the effect of defects on passage of a wave and the excitation of modal vibrations by the element base of PCM. The mathematical algorithm for estimating the acoustic conductivity of the wavefront, together with experimental data, was used for constructing a wave diagnostics algorithm. It made it possible to create an algorithm for a technical diagnostics of PCM elements. An experiment was conducted on the laser action on a carbon fiber panel with specially created defects. The frequency values found in various zones of carbon fiber showed a qualitative and quantitative change in the structure of PCM. It is shown that, to construct an effective model for diagnosing the technical condition of PCM elements, more experimental studies are required.
An algorithm for constructing a dynamic analysis during the formation of a wave field of stand for testing turbines and the effect of the frequency interaction of the stand’s elements on the measurement of its magnitude is described. The research algorithm involves the use of theoretical solutions of nonlinear wave processes using linear oscillations, refined by experiments. The diagnostic model can determine the technical condition of the stand’s elements and also determine the causes of the discrepancies between the calculated and measured turbine power values. To clarify the stiffness coefficients between the stand’s elements, a modal analysis was used to obtain the range of their changes depending on the external dynamic load, which made it possible to assess the impact of changes in the frequency interaction conditions on the turbine power measurement at different test modes. The conditions for amplifying the amplitude of oscillations at their eigenfrequencies are obtained, and the value of the possible deviation of the expected power value at its measurement for specific modes of the turbine is calculated. The algorithm allows to estimate the dynamic state of the stand-in different research modes of turbines and give recommendations for reducing the level of frequency interaction.
The purpose of the study is to analyze the prospects for the development of loading methods for gas turbines as well as to develop a mathematical model that adequately describes the real operating conditions of the loading system at various loads and rotation speeds. A comparative analysis of the most common methods and technical means of loading the shafts of a free turbine at gas turbine plants intended for operation as part of gas pumping units is presented. Based on the results of the analysis, the expediency of using the loading model “Free Power Turbine Rotor–Hydraulic Brake” as a load simulation is shown. Recommendations for the creation of an automation system for the load testing of power plants have been developed. Mathematical models and Hardware-in-the-Loop simulation models of power plants have been developed and tested. One of the most important factors that predetermine the effectiveness of the loading principle is the possibility of software implementation of the loading means using software control systems that provide the specified loading parameters of the gas turbine.
Пермский национальный исследовательский политехнический университет, Пермь, Россия ДИАГНОСТИКА ТЕХНИЧЕСКОГО СОСТОЯНИЯ КРУПНОГАБАРИТНЫХ ДЕТАЛЕЙ ГАЗОТУРБИННЫХ ДВИГАТЕЛЕЙ ПО МОДАЛЬНЫМ ХАРАКТЕРИСТИКАМ Описан алгоритм построения модального анализа при формировании волнового поля в деталях сложной геометрии. Показано, что, используя алгоритм модального вычета, можно с определенной достоверностью строить диагностическую модель по определению технического состояния объекта, возможных дефектов, отклонений в геометрических размерах (например, разнотолщинность, отклонение от заданного размера и т.д.), а также изменения плотности материала, микротрещин в теле конструкции. Показано, что данный алгоритм может использоваться без определенных знаний априорного волнового поля объекта, поскольку для выявления различных отклонений его структуры достаточно использовать определенное количество датчиков (не менее двух), установленных определенным образом по геометрическим плоскостям и их переходам, формирующим пространственную геометрию изделия. Проведено поэлементное «прослушивание» определенных однотипных зон детали при модальном их возбуждении, построен алгоритм определения ее технического состояния. С помощью анализа изменения волнового поля, формируемого поочередно от датчика к датчику, в объекте выстраивается алгоритм распознавания. Следовательно, получаемая оценка технического состояния объекта может быть построена на структурных характеристиках конкретного элемента, детали или сборки в целом. Приведен алгоритм диагностики сложных пространственных деталей на примере дефлектора второй ступени турбины высокого давления двигателя ПС-90А и кольца 0 ступени компрессора двигателя ПС-90ГП-2. Волновой алгоритм построен на анализе виброакустических откликов конструкции с использованием модального анализа при формировании виброакустических полей в изделии и на выявлении влияния различных дефектов на изменение амплитудночастотных характеристик волнового поля исследуемой детали. Приведены результаты оценки состояния исследуемых деталей.Ключевые слова: неразрушающий контроль, техническая диагностика, модальный анализ, амплитудно-частотная характеристика, волновое поле, дефект, частотный анализ.An algorithm for constructing a modal analysis in the formation of the wave field in the details of complex geometry is described. It is shown that. using the algorithm of modal deduction, it is possible to build a diagnostic model with a certain reliability to determine the technical condition of the object, to determine possible defects, deviations in geometric dimensions (for example, different thickness, deviation from a given size, etc.), in addition, changes in the density of the material, microcracks in the body of the structure. It is shown that this algorithm can be used without certain knowledge of the a priori wave field of the object, since to detect various deviations of its structure it is enough to use a certain number of sensors (at least two) installed in a certain way on the geometric planes and their transitions that form the spatia...
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