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Influence of friction condition on failure location of AA5754 aluminium sheet in Nakajima test

Slota J., Šiser M.

Zeszyty Naukowe Politechniki Rzeszowskiej. Mechanika

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2018

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z. 90 [298], nr 1

57--66

EN

This paper presents the results of numerical and experimental investigations on the influence of friction on failure location in Nakajima formability tests. Finite element (FE) simulations were performed using commercial explicit dynamic FE code. The numerical results obtained from the FE simulation were compared with experimental data from Nakajima tests. A 3D digital image correlation system ARAMIS was used in experiments. The location of failure on the sample was detected depending on friction conditions. The studies confirmed that the crack location near the centre of the specimen as required by the ISO standard could be obtained for low values of the friction coefficient. The numerical simulation combined with the inverse analysis was used to estimate a real value of the friction coefficient in the Nakajima formability test.

PL

W pracy przedstawiono numeryczne i eksperymentalne badania wpływu tarcia na lokalizację uszkodzeń w teście Nakajima. Symulację numeryczną testu przeprowadzono przy użyciu komercyjnego jawnego dynamicznego kodu FE. Wyniki uzyskane z symulacji FE porównano z danymi doświadczalnymi. W badaniach eksperymentalnych wykorzystano system ARAMIS do optycznej korelacji obrazu 3D. Lokalizacja uszkodzenia próbki wykazała zależność od warunków tarcia. Badania potwierdziły, że położenie pęknięcia w pobliżu środka próbki, zgodnie z wymaganiami normy ISO, można uzyskać dla niskich wartości współczynnika tarcia. Do oszacowania rzeczywistej wartości współczynnika tarcia w teście odkształcalności według Nakajima zastosowano symulację numeryczną połączoną z analizą odwrotną.

2

Geometric verification of the validity of Finite Element Method analysis of Abdominal Aortic Aneurysms based on Magnetic Resonance Imaging

Domagała Z., Stępak H., Drapikowski P., Kociemba A., Pyda M., Karmelita-Katulska K., Dzieciuchowicz Ł., Oszkinis G.

Biocybernetics and Biomedical Engineering

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2018

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Vol. 38, no. 3

544--555

EN

The currently used criterion of maximum transverse diameter for the Abdominal Aortic Aneurysm treatment has some limitations. Attempts to create individualized, therapeutic strategies are being conducted, including biomechanical assessment of rupture risk of an aneurysm based on the Finite Element Analysis of the geometric models. The usual approach is to use the results of the computed tomography imaging to build a three-dimensional model of the aneurysm. The FEA is then performed and the resulting stress is analysed to estimate the risk of rupture. Although such an approach brings significant improvements over the traditional maximum diameter method, it is difficult to ensure the validity of the assumptions made. This paper presents a method to evaluate the correctness of such an approach. The emergence of gated Magnetic Resonance Imaging allows registering aneurysm in both the systolic and diastolic phase of cardiac cycle. The corresponding geometric models are built and the results of the FEA applied to the diastolic model are compared with the actual deformation of the aneurysm observed in the patient's body. Thus, it is possible to verify whether the individualized diagnostic approach applied to a specific patient was correct. The geometry of the reference and the analysed models were compared using the Differential Surface Area Method. The average geometry error equals 1.65%. In the best case the error amounts to 1.04%, in the worst to 3.00%. The obtained results provide evidence that the Finite Element Analysis is a reliable method and can be potentially used for individualized diagnostics and treatment.

3

Fracture of laminated woven GFRP composite pressure vessels under combined low-velocity impact and internal pressure

Sharifi S., Gohari S., Sharifiteshnizi M., Alebrahim R., Burvill C., Yahya Y., Vrcelj Z.

Archives of Civil and Mechanical Engineering

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2018

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Vol. 18, no. 4

1715--1728

EN

Dome curvatures of pressure vessels often sustain highest level of stresses when subjected to various loading conditions. This research is aimed at investigating the effect of dome geometrical shape (hemispherical, torispherical, and ellipsoidal domes) on mechanical deformation and crack length of laminated woven reinforced polymer (GRP) composite pressure vessels under low-velocity impact (LVI) (case one) or combination of LVI and internal pressure (case two). The study is based on finite element (FE) simulations with laboratory-based experimental validation studies. It was observed that the maximum vertical displacements () and crack length along the diameter of deformation (a) are both of lower magnitude in case one. Damage intensity and fracture differ for different combinations of loading. Only matrix breakage and debonding occurs in case one and fiber breakage occurs in case two. The dome geometric shapes used in this study were found to be invariant to both damage intensity and failure modes. Irrespective of the type of load applied, the magnitude of and crack length correlate with dome geometric shape as the maximum and the minimum occur in torispherical and hemispherical domes, respectively. The maximum and the minimum crack lengths also take place in torispherical and hemispherical domes, respectively.

4

Analysis Of The Extrusion Process Of A Square Tube Multi-Channel Heat Pipe

Kim K. S., Kim J. Y.

Archives of Metallurgy and Materials

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2015

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Vol. 60, iss. 2B

1463--1466

EN

Heat pipes have been recently in use for cooling purposes in various fields, including electronic circuit boards and vehicle parts that generate large amounts of heat. In order to minimize the loss of heat transferred, there is a need to maximize the contact area of the working fluid. This study produced a square tube multi-channel heat pipe to replace the existing circular pipe type to maximize the internal surface area thereof. This expands the surface, allowing the working fluid to come into contact with a wider area and enhancing thermal radiation performance. A mold for the production for such a product was designed, and finite element simulation was performed to determine whether production is possible.