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  • The question by parametric models of partial failures in technical devices

    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

  • The reliability model of the partial failure in the technical system

    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

  • Model of decision making on the continuation of the functioning of a technical object in conditions of partial refusal by the criterion of economic expediency

    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

  • Model of degradation of partial failure in the technical system

    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

  • Partial failure in the theory of reliability

    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

  • Construction criteria for the identification of damage on the basis of the phase portraits fluctuations trusses

    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