Wyniki wyszukiwania - Biblioteka Nauki

1

Prediction of estimates of technical object’s reliability on the basis of damage determined from lindberg levy’s claim and multiplicity of the set specified from ergodicity stream damage

100%

Lindstedt P. , Sudakowski T. , Grądzki R.

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2013

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tom Vol. 20, No. 1

179--184

EN

During the exploitation one problem still unsolved is that of determining reliability characteristics for single (individual or small set) technical object. This particularly concerns identification of damage set (parametrical and momentary) as well as determination of substitute cardinality of objects set, where in fact this equals 1, 2, 3 at the most. The article presents a method of determining parametrical and momentary damages from iteration equations: D K= aRb DK + bRbU , (1) UW = aRc U + bRc DK , (2) where: DK – complex diagnostic signal, UW – net environment signal (manner of use), aRb – technical condition parameter, aRc – exploitation condition parameter (exploitation potential), bRb – parameter of environment (manner of use) influence intensity on technical condition, bRc – intensity parameter of technical condition (physical wear) influence on technical object operation quality. Assumption is made that if current value of aRb technical condition parameter is higher than aRb dop (permissible) stemming from central limit theorem, parametrical damage occurs and analogically if value of exploitation condition parameter aRc is higher that aRc dop, momentary damage occurs. Additional assumption is made that substitute cardinality of objects set might be deputized by properly long observation of single object, as resulting from assumption of damage flux ergodicity. Therefore, having damages number (parametrical and momentary) and large enough substitute cardinality for a single object, unreliability estimators might be calculated and thus reliability characteristics of technical object. Presented method of determining reliability characteristics is based on virtually not dangerous parametrical and momentary damages that occur before extremely dangerous catastrophic damage. Method has been verified in practices on bearing systems of two pump complexes of second grade pump station in Jurowce Water Purification Plant of Białystok Water Department.

2

Charakterystyki dynamiczne układu hydraulicznego jako nośnik informacji diagnostycznej o stanie niezdatności jego elementów

75%

Rychlik A.

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tom nr 2(42)

57-62

PL

W pracy zaproponowano metodę identyfikacji stanu technicznego układu hydraulicznego na podstawie analizy charakterystyk dynamicznych pozyskanych w kanale tłocznym pompy oleju. Jako uogólniony parametr stanu technicznego badanego układu hydraulicznego przyjęto zmianę: ciśnień i jego amplitud zarejestrowanych podczas ruchów roboczych układu, czasu ruchu roboczego tłoczyska siłownika oraz temperatury czynnika roboczego.

EN

The method of identification of the technical state of the hydraulic system on the base of the analysis of dynamic characteristics acquired in the pumping conduit of the oil pump was presented in the paper. As a generalized parameter of the technical state of the investigated hydraulic system there was assumed the change of: pressures and their amplitudes recorded during activity of the system, activity time of the piston rod of the hydraulic cylinder, temperature of the working fluid.

3

The sources of contamination and reasons for damage of the flow part of the marine turbine engine in operation

75%

Korczewski Z.

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tom R. 51, nr 4

9-19

EN

The aim of this paper is to show particular sensitivity of the flow part of the marine turbine engine to the presence of contaminants in the intake air. The contaminants form hard-to-remove deposits in the intervane channels that result in a reduced efficiency and performance of the engine. The paper classifies the contaminants according to the source of their formation and their destructive force. The performed analyses and syntheses of the discussed problem have been complemented with the results of own endoscopic research of the flow part of various types of marine turbine engines.

PL

Celem niniejszego artykułu jest wykazanie szczególnej wrażliwości części przepływowej turbinowego silnika spalinowego zabudowanego w siłowni okrętowej na obecność zanieczyszczeń zawartych w powietrzu dolotowym. Tworzą one w kanałach międzyłopatkowych sprężarek i turbin trudno usuwalne osady, które zmniejszają sprawność i osiągi silnika. W artykule sklasyfikowano występujące zanieczyszczenia według źródła powstawania i według charakteru destrukcyjnego oddziaływania na część przepływową. Przeprowadzone analizy i syntezy rozpatrywanego problemu eksploatacyjnego uzupełniono wynikami własnych badań endoskopowych części przepływowej różnych typów turbinowych silników okrętowych.

4

Zastosowanie sztucznych sieci neuronowych do identyfikacji uszkodzenia w belkach – badania numeryczne i doświadczalne

75%

Borowiec A. , Ziemiański L.

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tom R. 109, z. 8-M

3--13

PL

W pracy przedstawiono zastosowanie sztucznych sieci neuronowych (SSN) do identyfikacji uszkodzenia (położenie, wielkość) w belkach laboratoryjnych. Ocena uszkodzenia belek polega na analizie zmian częstotliwości rezonansowych wywołanych dodatkową zmieniającą położenie masą. Metoda nie wymaga znajomości parametrów modalnych belki nieuszkodzonej.

EN

This paper presents the application of Artificial Neural Networks (ANN) in the identification of damage (location, extent) in simple laboratory beam structure. The assessment of the state of a beams relies on the comparison of the structure eigenfrequencies obtained from the systems with additional masses placed in different nodes without knowledge of the natural frequencies of undamaged structures.

5

Damage identification using 2-D discrete wavelet transform on extended operational mode shapes

63%

Makki Alamdar M. , Li J. , Samali B.

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tom Vol. 15, no. 3

698--710

EN

In this paper a new scheme of damage detection and localisation is presented by implementing frequency response functions (FRFs) of damaged structure only. First damage sensitive shape signals are generated by taking the second order derivatives of the operational mode shapes at each frequency coordinate and then the anti-symmetric extension of each shape signal at the beginning and at the end of the signal is created to avoid boundary distortion phenomenon. In order to highlight the damage influence on shape signals, the shape signals are normalised with respect to the maximum value to adjust the amplitude difference between shape signals at different frequencies. It is illustrated that normalisation of shape signals significantly improves the damage localisation results. After normalising the shape signals, a two-dimensional (2-D) map of all shape signals is created and then is analysed by employing 2-D discrete wavelet transform (DWT). By performing 2-D DWT, three sets of horizontal, vertical and diagonal detailed wavelet coefficients will be obtained. It is demonstrated that amongst these three sets, horizontal detail coefficients are the most sensitive ones to any perturbation in the shape signals due to damage occurrence and, thus, are utilised to localise damage in this study.

6

Application of wavelet transform for damage detection in steel nodes of statically loaded truss girders

51%

Kawa O. , Knitter-Piątkowska A. , Studziński R.

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tom nr 12

27--33

EN

The article discusses non-destructive methods for identifying damage in welded truss joints using wavelet transform in a discrete form. Analyses showed that detecting damage required processing the difference between signals from the damaged and undamaged structure. With BIM development, recording reference points for the structural condition is straightforward, providing a basis for assessing the structure’s technical condition.

PL

Artykuł porusza problematykę nieniszczących metod identyfikacji uszkodzeń węzłów spawanych kratownic. Do identyfikacji uszkodzeń wykorzystano transformację falkową. Przeprowadzone analizy wykazały, że do wykrycia uszkodzenia w węźle kratownicy konieczne było przetworzenie różnicy sygnałów konstrukcji uszkodzonej i nieuszkodzonej. W kontekście rozwoju BIM, rejestracja punktów odniesienia stanu konstrukcji jest procesem prostym i dającym podstawę do późniejszej oceny jej stanu technicznego.

7

Damage identification of bridge structure model based on empirical mode decomposition algorithm and Autoregressive Integrated Moving Average procedure

44%

Lu W. , Dong J. , Pan Y. , Li G. , Guo J.

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tom Vol. 68, nr 4

653--667

EN

Time series models have been used to extract damage features in the measured structural response. In order to better extract the sensitive features in the signal and detect structural damage, this paper proposes a damage identification method that combines empirical mode decomposition (EMD) and Autoregressive Integrated Moving Average (ARIMA) models. EMD decomposes nonlinear and non-stationary signals into different intrinsic mode functions (IMFs) according to frequency. IMF reduces the complexity of the signal and makes it easier to extract damage-sensitive features (DSF). The ARIMA model is used to extract damage sensitive features in IMF signals. The damage sensitive characteristic value of each node is used to analyze the location and damage degree of the damaged structure of the bridge. Considering that there are usually multiple failures in the actual engineering structure, this paper focuses on analysing the location and damage degree of multi-damaged bridge structures. A 6-meter-long multi-destructive steel-whole vibration experiment proved the state of the method. Meanwhile, the other two damage identification methods are compared. The results demonstrate that the DSF can effectively identify the damage location of the structure, and the accuracy rate has increased by 22.98% and 18.4% on average respectively.