The authors consider the issue of assessing partial failure in the technical system from the standpoint of parametric reliability. Evaluation of failure behavior is carried out according to such parameters as time between hours to failure and the achievement of goals, risks. Under the risk in this paper refers to the likelihood of a subsequent failure (full or partial) or the transition occurred in full. The authors propose to expand the range of parameters that characterize hitting a failure state by adding characteristics of possible degradation processes and values of destructive environmental factors in the predicted period of continued operation of the object under study. Also, special attention is paid to the fact that the likelihood of partial failure is influenced by factors that can be divided into external and internal, while the internal ones may depend on external ones. Ishikawa diagram shows the dependence of the rate of degradation of the PR on various factors.
Keywords: partial failure, parametric reliability, risk, time of failure degradation, Ishikawa diagram
In the article, the authors present the results of studies related to the effect of partial failures (PF) on the reliability characteristics of the system, determined through the probability of continuous operation over the interregional period under the conditions of continued operation after PF. The computational model is based on the assumption that the process of continuing to function after a spacecraft can be considered as redundancy by substitution, when the reserve appears capable of performing post-failure functions, but with some change in the reliability characteristics. The entire work interval is divided into separate sections inside, which the technical system operates with new reliability characteristics, with the sequential occurrence of several PF. A model with an exponential law of distribution of probabilities of partial failures is considered. It is believed that testing the device of the entire interregional period without a complete failure can be characterized as the product of the probabilities of the absence of a complete failure on the considered time interval, the absence of the occurrence of destructive external influences exceeding the critical values, the error-free processing of the program by the expert system and the absence of errors in the operator's actions. The results of the illustrative calculation are presented and conclusions are made.
Keywords: partial failure, redundancy, indicators of reliability of working out in the interregional period, calculated ratios for assessing reliability in case of partial failure
This article discusses the economic approach to the choice of the mode of continuation of the system in the face of partial failure. It discusses strategies related to the continuation of work in conditions of partial failure or cessation of operation until the completion of the operational restoration process. The characteristics of each of the strategies are presented in a comparative aspect for the continuation of the operation of the object in the post-failure period or the delay in operation for the duration of the restoration. The dependence of the time recovery parameters and the times defining the moment of identifying a partial failure in the coordinates of the time axis from the beginning of the working cycle to the next scheduled maintenance has been revealed. The resulting mathematical expressions allow, under certain conditions, to justify the choice of one of the two strategies considered. For more complex cases, it is proposed to use expert approaches to take into account additional characteristics of the process, such interregional period, performance and acceptable risks associated with working in conditions of partial failure. The article provides graphs illustrating the change in reliability characteristics in two ways of developments of events related to the adoption of a decision to continue work.
Keywords: partial failure, the coefficient of gain in terms of work, the probability of uptime, recovery time, time in the post failure period
The process of analysis and modeling is proposed to be carried out in three stages: determinism, stochasticity and adaptability. The essence of these stages is revealed. The authors highlight the problem of predicting changes in partial failure, affecting the state of the technical system. The main distinctive features of such a refusal from the full (partial loss of working capacity, reducing the number of functions performed, and others) are shown. A diagram of the development of possible degradation processes in a technical facility as a result of partial failure is presented. Transitions to the states of several consecutive partial failures or transitions to a complete failure after one or several partial ones are possible. With getting into a state of complete failure, the object is fully restored. Developed proposals for the sequence of operations for the identification of failures at the level of the generalized algorithm. An illustrative example considers a fragment of the transition of a partial failure to another partial failure, which develops into a complete failure with the impossibility of further functioning of the electric machine for its intended purpose. The conclusion is made about the need to use expert systems and assessments for making decisions about functioning in conditions of partial failure.
Keywords: partial failure, critical failure, degradation change failure, diagnostic task, electric machine
The problem of lateral buckling of a free-supported wooden strip with a constant narrow cross-section loaded with concentrated force in the middle of the span is considered. In the study of lateral buckling of the beam was used energy method. For the case of load application in the center of gravity, the problem is reduced to a generalized secular equation. The dependence between the value of the critical force and the position of the point of application of the load is obtained. A linear approximating function is chosen for this dependence. The results obtained by the authors are compared with the analytical solution using Bessel functions and the numerical iterative method.
Keywords: thermal conductivity, finite element method, the steady-state temperature field, radiation-heat shield, thick-walled cylinders
The concept of “partial failure” used in practice is analyzed as a state in which the possibility of continuing the operation of a technical device remains. It is argued that partial failures are widespread in the operation of technology, but unlike full failures, under which the continuation of work becomes impossible in any mode, not fully understood. A number of reliability indicators are proposed that take into account the specifics of partial failures and the possibility of continuing work when they occur. Attention is drawn to the fact that the decision to continue the operation of the device in the presence of a partial failure is associated with risks. The essence of the risks lies in the possibility of receiving damage in the form of further deterioration of the technical condition of the partially failed device. However, in many cases such a risk may be justified. The task of deciding on the continuation of the operation, in the conditions of a partial failure is a complex task of system analysis. Its solution will require the use of complex models compiled using modern methods of mathematical descriptions and research.
Keywords: partial failure, reliability theory, reliability indicators with partial failure, risks of continued operation, making decisions on continuation of operation
Light steel thin-walled structures are considered as elements of modern building erection technology. Domestic and foreign regulatory documents governing the use and design of structures made of thin-walled steel profiles are presented, and obvious advantages and operational disadvantages are indicated.
Keywords: construction, metal structures, light steel thin-walled structures, thin-walled beams, energy efficiency
An actual problem of the lack of green spaces in modern cities is considered. Some ways of applying gardening in the structure of the building are suggested, which can solve the indicated problem. The most detailed consideration is the reception of horizontal external landscaping, examples of domestic and foreign experience are given.
Keywords: Green architecture, green spaces, vertical landscaping, atrium landscaping, horizontal outdoor landscaping, house-garden decoration of building facades, roofs in operation
Flat bending stability problem of constant rectangular transverse section wooden beam, loaded by a concentrated force in the middle of the span is considered. Differential equation is provided for the cases when force is located not in the center of gravity. The solution of the equation is generated numerically by the method of finite differences. For the case of applying a load at the center of gravity, the problem reduces to a generalized secular equation. In other cases, the iterative algorithm developed by the authors is implemented, in the package Matlab. A relationship is obtained between the value of the critical force and the position of the load application point. For this dependence, a linear approximating function is chosen. A comparison of the results obtained by the authors with an analytical solution using the Bessel functions is performed.
Keywords: flat bending stability, secular equation, finite difference method, iteration process
A constructive solution of the walls of wooden houses from round logs or a profiled beam, which is installed vertically (wooden element) is considered. It is proposed to arrange two longitudinal milled grooves of a rectangular shape located in the diametral plane of the section of the log for the installation of sheet plywood keys, which makes it possible to include in the joint work adjacent contiguous elements when working on bending from the plane of the wall. The variant of the strapping device, it is proposed to use metal rolling profiles of Channel and I-sections, connected with metal tube elements (box section) mounted in the corners of the frame.
Keywords: round log, profiled beam, sheet plywood keys, tubular section elements
We consider eccentrically compressed rod elements of reinforced concrete structures. Problems are solved for the development of methods for calculating the strength of normal sections in the case of eccentric compression of reinforced concrete elements; calculation of the load-carrying capacity of reinforced concrete structures by the example of columns of varying flexibility for ultimate effort. Analytically, a calculation is made, which makes it possible to determine the strength of reinforced concrete structures.
Keywords: внецентренно сжатые стержни, железобетонные конструкции, прочность, нормальные сечения, колонны различной гибкости, несущая способность, предельные усилия
This paper proposes a method for detecting damage truss rod cantilever structure on the basis of new information sign "Express - distinguishing between" damage. It is based on the analysis of the phase diagrams for modeling its transient oscillations. Produced comparison of various parameters damped oscillations truss rod design for the structure without damage and corruption. Processed and analyzed the frequency response based on them phase diagrams. To analyze the response considered in the frequency range from 0 to 100 Hz. An analysis of the phase diagrams in different frequency regions design is presented as an information sign "Express - distinction" of having damage to the truss.
Keywords: Truss rod design, damage, finite element modeling, information sign, transient fluctuations of the amplitude-frequency analysis, phase diagrams
Time Division Multiplexing is the one of the main information transmission technology. Main problem of this method is the large amount of empty of traffic. This number can reach about 97%. In article presents a method for reducing amount of empty traffic by using the new system pointers, that encode information about the frame . Pointer consists of three components : a pointer to a smaller source (points to the source that gave less information ), a pointer to a smaller amount of information and a pointer to the source memory block (points to the memory block , where the frame was formed ). This pointer is generated when creating a frame and is written in the first data slot. After transmitting a frame pointer is decoded, and based on this information, the distribution of data occurs on the output signals. The developed method has several advantages over similar methods of data transmission, does not depend of the speed of data sources, and have minimum depends on amount of input signals. This technology allows to fill information cells only useful information, and improve the efficiency of code up 96.6 %.
Keywords: Time division multiplexing, traffic reduction, statistical multiplexing, static multiplexing, frame coding
The article describes the experience of the unique complex of works to improve the operational reliability of the emergency office buildings located in a cramped building, whose main task was to eliminate excessive rolls with hydraulic jacks and ensure the continued trouble-free operation. Highlighted the key features of the design and technology solutions for the simultaneous lifting and leveling of several buildings with different design decisions.
Keywords: adjustable foundation, electro-hydraulic flat jacks, cramped building, lifting and leveling, operational reliability.
The problem of temperature stresses in revetments of concrete plates taking in the account various conditions of temperature impact is considered. Contact conditions for various friction coefficient are considered. The simulation is made using finite element method in Ansys © software. The examples of exact simulations for stress fields are given for different parameters of problem
Keywords: temperature stresses, concrete plate, finite element method