Wyniki wyszukiwania - Biblioteka Nauki

1

Experimental and numerical study of damage initiation mechanism in elastomeric composites

100%

Silva Botelho T. D. , Bayraktar E.

|

tom Vol. 36, nr 1

65-70

EN

Purpose: Experimental and Finite Element Analysis (FEA) of the damage initiation mechanisms in elastomeric composites were carried out under static loading at room temperature. Double Cantilever Beam (DCB) specimens from natural rubber (NR) vulcanised and reinforced with other materials such as carbon black, silica, fibres and textiles or metals (rubber composites). Design/methodology/approach: Very huge experimental results were compared with that of the Finite Element Analysis (FEA). Damage mechanism has been described with a threshold criterion to identify damage. The damage was evaluated just at the beginning of the tearing by assuming large strain. A typical type of specimen geometry of Double Cantilever Beam (DCB) specimens was considered under static tensile tests conducted on the notched specimens with variable depths. Findings: In this stage of this research, a finite element analysis (FEA) has been applied under the same conditions of this part in order to obtain the agreement between experimental and FEA results. The numerical modelling is a representation of a previous experimental study. The specimen is stretched more than once its initial size, so that large strains occur. A hyper elastic Moonley-Rivlin law and a Griffith criterion are chosen. The finite elements analysis was performed with ABAQUS code (V.6.4.4). Practical implications: A damage criterion was suggested in the case of simple tension conditions by assuming large strain levels. an effective finite elements model has been developed to evaluate notch size effects on the load-displacement elastic response of 3D-DCB type specimen. Originality/value: This study proposes a threshold criterion for the damage just at the beginning of the tearing for Double Cantilever Beam (DCB) specimens from rubber composites and gives a detail discussion for explaining the damage mechanisms. Comparison of FEA results with those of experimental studies gives many facilities for the sake of simplicity in industrial applications.

2

Mechanizm uszkodzenia betonu w obiektach oczyszczalni ścieków przemysłowych

100%

Słomka-Słupik B. , Zybura A.

|

tom nr 12

14-15

3

Damage diagnostics of turbine blades.

100%

Madej J.

|

2003

|

tom Vol. L, nr 1

69-87

EN

The paper presents the most frequently encountered types and mechanisms of damage of turbines' flow elements. The methods used nowadays for diagnosis of the damage are presented. A new possibility of localisation of damaged areas of turbine blades based upon the analysis of isotherm layout is proposed.

PL

W artykule opisano najczęściej spotykane rodzaje i mechnizmy uszkodzeń elementów przepływowych turbin. Na tle aktualnie stosowanych metod diagnozowania uszkodzeń zaproponowano nową możliwość lokalizowania defektów łopatek turbinowych drogą analizy rozkładu izoterm. Niniejsze opracowanie stanowi kontynuację wcześniejszych prac autora na temat wpływu uszkodzeń na rozkład temperatur w materiałach konstrukcyjnych i dotyczy wykorzystania poczynionych spostrzeżeń do diagnozowania części maszyn.

4

Degradation modeling method for rotary lip seal based on failure mechanism analysis and stochastic process

100%

Liu D. , Wang S. , Tomovic M. M.

|

2020

|

tom Vol. 22, no. 3

381--390

EN

Rotary lip seal is widely used in aircraft and its performance affects the safety of the aircraft. Hence, it is necessary to estimate useful lifetime and reliability of the seal. Degradation of rotary lip seal is always with random effects, which cannot be considered by theoretical failure mechanism analysis. Hence, in order to consider the random effects of rotary lip seal degradation, stochastic processes are applied. Furthermore, considering the monotonic degradation of the seal, Gamma process and inverse Gaussian process are selected as the candidate processes. To combine the candidate processes, Bayesian model averaging is introduced. Based on the failure mechanism analysis and numerical simulation, the theoretical wear path is predicted and corresponding linearization method is proposed. The measured degradation data is converted and the seal wear process is transformed to a linear degradation process. The model parameters and model probabilities are evaluated by fully Bayesian inference method. The effectiveness of the proposed method is verified by comparing the predicting degradation and experimental observations. The proposed method can be used to evaluate reliability and useful lifetime of rotary lip seal. According to sensitivity analysis, an effective way to improve lifetime and reliability of the seal is to increase the wear depth threshold.

PL

Obrotowe uszczelnienia wargowe znajdują szerokie zastosowanie w samolotach, a ich sprawność wpływa na bezpieczeństwo statków powietrznych. Oznacza to, iż szacowanie żywotności i niezawodności tego rodzaju uszczelnień ma kluczowe znaczenie. Degradacja obrotowego uszczelnienia wargowego jest zawsze związana z efektami losowymi, których nie uwzględnia teoretyczna analiza mechanizmu uszkodzenia. Dlatego też do oceny efektów losowych degradacji obrotowego uszczelnienia wargowego wykorzystuje się procesy stochastyczne, takie jak proces Gamma czy odwrotny proces Gaussa. W przedstawionej pracy, wybrane procesy degradacji łączono za pomocą metody bayesowskiego uśredniania modeli. Na podstawie analizy mechanizmów uszkodzeń i symulacji numerycznej, konwertowano uzyskane w pomiarach dane degradacyjne, co pozwoliło na przekształcenie procesu degradacji obrotowego uszczelnienia wargowego w proces liniowy. Parametry modelu i prawdopodobieństwa oceniano za pomocą metody pełnego wnioskowania bayesowskiego na podstawie obserwacji degradacji. Skuteczność przedstawionej metody weryfikowano porównując przewidywane i obserwowane wartości degradacji. Proponowaną metodę można wykorzystywać do oceny niezawodności i żywotności obrotowego uszczelnienia wargowego. Przeprowadzona analiza czułości pokazuje, że skutecznym sposobem na poprawę żywotności i niezawodności omawianego typu uszczelnienia jest zwiększenie progu uszkodzenia w postaci maksymalnej głębokości zużycia.

5

Damage initiation mechanism in rubber sheet composites during the static loading

100%

Luong R. , Isac N. , Bayraktar E.

|

2007

|

tom Vol. 28, nr 1

19-26

EN

Purpose: Mechanical behaviour and damage initiation mechanisms in thin rubber sheet composites were investigated under static solicitation at room temperature. Two types of rubber are used in this study; Natural rubber, NR vulcanised and reinforced by carbon black and Synthetic rubber (styrene-butadiene-rubber, SBR). Design/methodology/approach: A comprehensive study has been carried out in order to identify a threshold criterion for the damage mechanism to explain a tearing criterion for the concept of tearing energy of the elastomers and also to give a detail for the damage mechanism depending on the loading conditions. A typical type of specimen geometry of thin sheet rubber composite materials was studied under static tensile tests conducted on the smooth and notched specimens with variable depths. In this way, the effects of the plane stress on the damage mechanism are characterized depending on the rubber materials. Findings: Damage mechanisms during tensile test have been described for both of rubber types and the criteria which characterize the tearing resistance, characteristic energy for tearing (T) was explained. Damage in the specimens were evaluated just at the beginning of the tearing by means of the observations in the scanning electron microscopy (SEM). Practical implications: A tearing criterion was suggested in the case of simple tension conditions by assuming large strain. In the next step of this study, a finite element analysis (FEA) will be applied under the same conditions of this part in order to obtain the agreement between experimental and FEA results. Originality/value: This study propses a threshold criterion for the damage just at the beginning of the tearing for thin sheet rubber composites and gives a detail discussion for explaining the damage mechanisms by SEM results. This type of study gives many facilities for the sake of simplicity in industrial application.

6

Corrosion behaviour of the welded steel sheets used in automotive industry

80%

Katundi D. , Tosun-Bayraktar A. , Bayraktar E. , Toueix D.

|

tom Vol. 38, nr 2

146-153

EN

Purpose: of this paper is to characterise the corrosion resistance in the steel sheets (Hot dip galvanizing of steel sheets) used in automotive industry. In fact, corrosion of automotive components by road salt is a widely known problem. The different parts under the car body and the interior surface of body panels suffer easily from the corrosive products deposited on roads and used mainly to melt snow. A comparison in a chemical investigation of the corrosion rate for base metals (without welding) and welded steel is required. Therefore, conformity will be accomplished between the corrosion phenomena in simulated corrosion tests and those in actual cars. Design/methodology/approach: Simulated corrosion tests, wet/humidity test and hot dust/dry cycle talk test carried on in laboratory conditions was investigated quantitatively. Dynamic behaviour of the corroded specimens have been tested dynamically to simulate under the crash test conditions. Findings: Studies carried out on the vast corroded samples have shown that the pitting corrosion damage and crack initiation sites have began and propagated generally in the HAZ in the welded steel sheets (Tailored welded blanks - TWB). Research limitations/implications: This paper contains partially results of a common research project. Some limitations exist in application of hot dust/dry cycle talk to the real open air test conditions. All of these results were carried out in the laboratory conditions. Practical implications: The problem is of extreme importance to all academic, scientific, manufacturing, maintenance and industrial societies. The outcome of the proposed study will contribute to the industrial application of ARCELOR-MITTAL. The proposed study will be benefit not only for the car industry and steel makers, but also important for the other industrial applications. The proposed research can be employed in a broad range of applications in oil and natural gas industries. This project will promote multidisciplinary research and cooperation between university and industry. Originality/value: An effective corrosion test proposed by Volvo was applied to the welded sheets (TWB) in an enclosed climatic chamber. This test is a practical and inexpensive test. Impact tensile-crash test makes it possible to analyse the corrosion damage of sheet metals under the dynamic rupture.