Wyniki wyszukiwania - BazTech

1

Experimental and numerical evaluation of quasi-static indentation behaviour of laminates with polypropylene matrix

Mahdad M’hamed, Benidir Adel, Belaidi Idir

Composites Theory and Practice

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2021

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R. 21, nr 4

127--134

EN

This paper presents an analysis of the damage process of composite laminates subjected to low-velocity quasi-static indentation (QSI) load. The laminates were prepared using the compression moulding technique. The composites were made from orthotropic layers with E-glass or steel fibres and a polypropylene matrix. The quasi-static indentation tests were carried out at three levels of indentation energy under low-velocity. The experimental results reveal that using steel fibres increases the perforation threshold, which alludes to the importance of the fibre type in delineating damage regions. In contrast, the evolution of the damage and the perforation resistance of glass fibre reinforced laminates is somewhat different. A numerical model based on a finite element program was developed to understand the mechanisms of damage evolution in the laminates. It involves implementing the Matzenmiller-Lubliner-Taylor (MLT) damage model. A comparison between the experimental and numerical results was also made.

2

Uszkodzenia i diagnostyka zasuw instalacji wysokoprężnych

Jasiński Artur

Energetyka

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2020

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nr 9

495--499

PL

W instalacjach przemysłowych oraz rurociągach ogólnego przeznaczenia powszechnie montowane są zasuwy. Ich zadaniem jest doprowadzanie lub odcinanie przepływu mediów, takich jak: woda i ścieki, para wodna, gazy, ropa, oleje, spaliny i inne. W zależności od konstrukcji instalacji, parametrów pracy i rodzaju medium montuje się je w pozycji poziomej lub pionowej poprzez połączenia kołnierzowe, kielichowe, gwintowe lub spawane. W zależności od napędu rozróżniamy zasuwy z napędem ręcznym, elektrycznym, pneumatycznym lub hydraulicznym, a ich sterowanie może być ręczne lub automatyczne. Prawidłowe wytworzenie, montaż i eksploatacja nie powinny stanowić zagrożenia dla osób i otoczenia. Jeśli jednak zasuwy są stosowane i eksploatowane niewłaściwie lub posiadają wady wytwórcze, mogą w skrajnych przypadkach stanowić ogromne zagrożenie. Artykuł poświęcony jest najczęściej spotykanym uszkodzeniom zasuw.

EN

Gate valves are elements commonly mounted in industrial installations and general purpose pipelines. Their objective is to deliver or cut off the flow of media, for example, water and wastewater, water vapour, petroleum, gas, oil, flue gas and others. Depending on the construction of the installation, operating parameters and medium, gate valves are mounted in a horizontal or vertical position by means of flange / socket / threaded or welded connections. Gate valves can have manual, electrical, pneumatic or hydraulic actuators. They can be operated manually or automatically. Their proper production, assembly and use should not cause any danger to people or the environment. However, if gate valves are used in an improper way or contain manufacturing defects, in extreme cases, they can create a huge hazard. The article focuses on the most common damage to gate valves.

3

Torsional fatigue behaviour and damage mechanisms in the very high cycle regime

Bayraktar E., Xue H., Ayari F., Bathias C.

Archives of Materials Science and Engineering

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2010

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Vol. 43, nr 2

77-86

EN

Purpose: of this paper: Many engineering components operate under combined torsion and axial cyclic loading conditions, which can result in fatigue fracture after a very long life regime of fatigue. This fatigue regime were carried out beyond 109 loading cycles called very high cycle fatigue (VHCF) to understand the fatigue properties and damage mechanisms of materials. Design/methodology/approach: Torsional fatigue tests were conducted using a 20 kHz frequency ultrasonic fatigue testing device. The results obtained were compared to those of the conventional torsional fatigue test machine operated at 35 Hz to observe any discrepancy in results due to frequency effects between two experiments. Findings: All the fatigue tests were done up to 1010 cycles at room temperature. Damage mechanisms in torsional fatigues such as crack initiation and propagation in different modes were studied by imaging the samples in a Scanning Electron Microscope (SEM). The results of the two kinds of material show that the stress vs. number of cycle curves (S-N curves) display a considerable decrease in fatigue strength beyond 107 cycles. Research limitations/implications: Each test, the strain of specimen in the gage length must be calibrated with a strain gage bonded to the gage section. This is a critical point of this study. The results are very sensitive to the calibration system. Control of the displacement and the output of the power supply are made continuously by computer and recorded the magnitude of the strain in the specimen.

4

Torsional fatigue behaviour in gigacycle regime and damage mechanism of the perlitic steel

Xue H. Q., Bayraktar E., Marines-Garcia I., Bathias C.

Journal of Achievements in Materials and Manufacturing Engineering

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2008

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Vol. 31, nr 2

391-397

EN

Purpose: This paper gives a comprehensive study based on the damage mechanism under torsional fatigue behaviour of D38MSV5S steel in very high cycle regime (VHCF). Torsional fatigue tests have been carried out at 20 kHz ultrasonic fatigue testing device, and these results were compared with that of the conventional torsional fatigue test machine at 35 Hz as to whether the discrepancy due to the frequency effects between two test results. All of the fatigue tests were carried out up to 1010 cycles at room temperature. Design/methodology/approach: Damage mechanism in torsional fatigues crack initiation and propagation in different mode was evaluated by Scanning Electron Microscopy (SEM). Findings: The experimental results have shown that the S-N curves exhibited a considerable decrease in fatigue strength beyond 107 cycles. Practical implications: These results give a precise data for the safety design of the pieces. Originality/value: Damage mechanism under torsional fatigue loading composes two stages, crack initiation and crack propagation, contrary to the damage under axial loading that exposes only crack initiation mechanism in the VHCF range.

5

Manufacturing and damage mechanisms in metal matrix composites

Bayraktar E., Masounave J., Caplain R., Bathias C.

Journal of Achievements in Materials and Manufacturing Engineering

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2008

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Vol. 31, nr 2

294-300

EN

Purpose: Mechanical properties of metal matrix composites (MMCs) are essentially functions of the manufacturing processes. Surface state and roughness conditions as well as the type of matrix reinforcement and heat treatment influence the mechanical behaviour of the MMCs in service conditions. The factors such as the porosity of the matrix, volume fraction of the reinforcement and their distribution, agglomeration or sedimentation of particles and particle size, dross and porosities influence the behaviour of the MMC. The static and cyclic deformation behaviour of these two metal matrix composites has been investigated at room temperature; 2124/Al-Si-Cu fabricated by powder metallurgy and AS7G/Al-Si-Mg fabricated by foundry. Design/methodology/approach: In cyclic deformation, surface roughness effect on the damage behaviour has been discussed. The microstructure for optical images was made by Olympus optical microscope (OM). The failed specimens are observed by using of scanning electron microscope (SEM) and also the variation of volume fraction depending on the tomography density (TD) was evaluated by means of X-rays computed tomography, CT. Findings: AS7G composite showed considerable lower mechanical properties regarding to the 2124 composite. In the AS7G composite, the crack generally initiated at the interface (SiC/matrix) with many interface debonding between the SiC particles and the matrix. This was the principal cause of the reduced fatigue strength. Practical implications: Applications of χ -rays CT on the composite materials is more efficient and skilful. χ -rays CT well characterise the particle size and the distribution of the reinforcements-volume fraction as 3D at the mesoscopic scale as a possible way to study this aspect. Originality/value: Manufacturing of two new different MM-composites and damage analysis in successful usage of aerospace application.