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    Wyświetlanie 1-4 z 4
    Tytuł:
    A model for service life control of selected device systems
    Autorzy:
    Zieja, M.
    Ważny, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/259281.pdf
    Data publikacji:
    2014
    Wydawca:
    Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
    Tematy:
    reliability
    unreliability
    durability
    service lifetime
    destructive processes
    Opis:
    This paper presents a way of determining distribution of limit state exceedence time by a diagnostic parameter which determines accuracy of maintaining zero state. For calculations it was assumed that the diagnostic parameter is deviation from nominal value (zero state). Change of deviation value occurs as a result of destructive processes which occur during service. For estimation of deviation increasing rate in probabilistic sense, was used a difference equation from which, after transformation, Fokker-Planck differential equation was obtained [4, 11]. A particular solution of the equation is deviation increasing rate density function which was used for determining exceedance probability of limit state. The so-determined probability was then used to determine density function of limit state exceedance time, by increasing deviation. Having at disposal the density function of limit state exceedance time one determined service life of a system of maladjustment. In the end, a numerical example based on operational data of selected aircraft [weapon] sights was presented. The elaborated method can be also applied to determining residual life of shipboard devices whose technical state is determined on the basis of analysis of values of diagnostic parameters.
    Źródło:
    Polish Maritime Research; 2014, 2; 45-49
    1233-2585
    Pojawia się w:
    Polish Maritime Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Dynamic Mechanical Properties of Artifcially Aged Double Base Rocket Propellant and the Possibilities for the Prediction of Their Service Lifetime
    Autorzy:
    Matečić-Mušanić, S.
    Sućeska, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/358886.pdf
    Data publikacji:
    2013
    Wydawca:
    Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
    Tematy:
    ageing
    double base rocket propellants
    dynamic mechanical analysis
    glass transition temperature
    lifetime prediction
    loss modulus
    softening temperature
    storage modulus
    tan δ
    Opis:
    The ageing of double base (DB) rocket propellants, as a consequence of the chemical reactions and physical processes that take place over time, has a signifcant effect on their relevant properties, such as chemical composition and mechanical and ballistic properties. The changes to relevant properties limit the safe and reliable service life of DB rocket propellants. Accordingly, numerous research efforts have been undertaken to fnd reliable methods to measure the changes caused by ageing in order to assess the quality of DB rocket propellants at a given moment of their lifetime, and to predict their remaining service lifetime. In this work we studied the dynamic mechanical properties of DB rocket propellant artifcially aged at temperatures of 80, 85 and 90 °C, in order to detect and quantify changes in the dynamic mechanical properties caused by ageing, and to investigate the possibilities for the prediction of service lifetime. Dynamic mechanical properties were studied using a dynamic mechanical analyser (DMA). The results obtained have shown that ageing causes signifcant changes in the storage modulus (E´), the loss modulus (E˝) and the tan δ curves’ shape and position. These changes are quantifed by following some characteristic points on the E´-T, E˝-T, and tan δ-T curves (e.g. glass transition temperatures; storage modulus, loss modulus and tan δ at characteristic temperatures, etc.). It has been found that the monitored parameters are temperature and time dependent, and that they can be shown to be functions of the so called ‘reduced time of artifcial ageing’. In addition, it has been found that, on the basis of known changes in viscoelastic properties as a function of time and ageing temperature, and the known kinetic parameters of the ageing process, it is possible to calculate (determine) the change in the properties at any ageing temperature provided that the mechanism of the ageing process does not change. Unfortunately, the use of kinetic parameters obtained by artifcial ageing at high temperatures (above 60 °C) for the prediction of the propellant lifetime will not give reliable results, because the mechanisms of ageing at 85 °C and 25 °C are not the same.
    Źródło:
    Central European Journal of Energetic Materials; 2013, 10, 2; 225-244
    1733-7178
    Pojawia się w:
    Central European Journal of Energetic Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Przewidywanie okresu trwałości elastomerów. Cz. I. Degradacja elastomerów i przewidywanie czasu życia
    Prediction of stability of elastomers. Part I. Degradation of elastomers and prediction of lifetime
    Autorzy:
    Lewandowski, M.
    Pawłowska, U.
    Powiązania:
    https://bibliotekanauki.pl/articles/272778.pdf
    Data publikacji:
    2016
    Wydawca:
    Sieć Badawcza Łukasiewicz - Instytut Inżynierii Materiałów Polimerowych i Barwników
    Tematy:
    trwałość elastomerów
    degradacja elastomerów
    czas życia
    czas przechowywania
    czas serwisowania
    metoda Arrheniusa
    metoda superpozycji czas–temperatura
    metoda Williamsa–Landela–Ferry’ego
    WLF
    stability of elastomers
    degradation of elastomers
    lifetime
    storage life
    service life
    Arrhenius approach
    time–temperature superposition
    Williams–Landel–Ferry approach
    Opis:
    Opisano czynniki wpływające na zmiany właściwości fizycznych elastomerów podczas ich przechowywania i eksploatacji. Zdefiniowano okres trwałości elastomerów i pojęcia z nim związane – czas życia, czas przechowywania, czas serwisowania, podano również szacunkowy czas i zalecane warunki przechowywania produktów elastomerowych. Opisano metody przewidywania czasu życia elastomerów przy użyciu przyspieszonego starzenia cieplnego: metodę Arrheniusa, metodę superpozycji czas–temperatura i metodę Williamsa–Landela–Ferry’ego (WLF).
    Factors affecting changes of physical properties of elastomers during storage and exploitation were described. A stability of elastomers and notions associated with it were defined – lifetime, storage life, service life. Estimated time and recommended conditions of storage of elastomeric products were also given. Methods of predicting the lifetime of elastomers using accelerated heat ageing: Arrhenius approach, time–temperature superposition, Williams–Landel–Ferry approach (WLF) were described.
    Źródło:
    Elastomery; 2016, 20, 2; 24-30
    1427-3519
    Pojawia się w:
    Elastomery
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Research on preventive maintenance strategies and systems for in-service ship equipment
    Autorzy:
    Song, Tingxin
    Tan, Taiyang
    Han, Guochen
    Powiązania:
    https://bibliotekanauki.pl/articles/32887248.pdf
    Data publikacji:
    2022
    Wydawca:
    Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
    Tematy:
    preventive maintenance
    FMEA
    lifetime prediction
    decision system
    ship equipment
    Opis:
    With continuous improvements in the function and performance of ship equipment, mechanisms of failure have become more and more complicated. To avoid over-maintenance or under-maintenance in existing routine ship maintenance strategies, a ship-level method for repair decisions based on the preventive maintenance concept is proposed in this paper. First, the anticipated repair demand levels of key components are calculated using an improved failure mode and effects analysis (FMEA) method; second, a Weibull distribution model is established, and the parameters are estimated using the maximum likelihood estimation (MLE) to predict the characteristic life of the equipment; then, logical decision principles and rule-based reasoning (RBR) are used to determine the ship repair level and repair timing. Finally, the feasibility and application value of the proposed repair strategy were verified by case studies, and a ship-level system for repair decisions was established.
    Źródło:
    Polish Maritime Research; 2022, 1; 85-96
    1233-2585
    Pojawia się w:
    Polish Maritime Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-4 z 4

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