Wyniki wyszukiwania - BazTech

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Experimental research of energy absorbing structures within helmet samples made with the additive manufacturing method – preliminary study

Tobola Wojciech, Papis Mateusz, Jastrzębski Dominik, Perz Rafał

Acta of Bioengineering and Biomechanics

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2023

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Vol. 25, no. 1

127--136

EN

This study aimed to develop an energy-absorbing structure for bicycle helmets to minimize head injuries caused by collisions. The research team explored three geometric structures produced through additive methods and compares their energy absorption properties with a standard bicycle helmet made of Expanded Polystyrene (EPS) foam. Methods: The study prepared samples of three geometric structures (a ball, a honeycomb and a conical shape) and a fragment of a bicycle helmet made of EPS foam with the same overall dimensions. Laboratory tests were conducted using a pneumatic hammer, piston compressor, anvil, triaxial accelerometer and data processing systems. Three crash tests were performed for each type of structure, and the anvil's maximum acceleration and stopping distance after the crash were analyzed. Results: The study found that the energy absorption properties of the Polylactic Acid (PLA) material printed with the incremental method were comparable or better than those of the EPS material used in helmets. The geometric structure of the energy-absorbing material played a crucial role in its effectiveness. The most promising results were obtained for the ball samples. Conclusions: The study concluded that further research on energy-absorbing structures made using the Fused Deposition Modeling (FDM) method could be useful in the production of bicycle helmets. The results show that the geometric structure of the energy-absorbing material is a crucial factor in its effectiveness. The findings suggest that the ballshaped structure made with PLA material printed using the incremental method could be a promising design for bicycle helmets to minimize head injuries caused by collisions.

2

Studies on the performance of impact resistant structure of hydraulic support in fully mechanized mining face under rock burst

Zhang Qiang, Zhang Runxin

Journal of Theoretical and Applied Mechanics

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2022

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Vol. 60 nr 4

649--658

EN

In order to solve the support problem of a fully mechanized coal face under rock burst and with the goal of safe and efficient coal mining, the present study hasenvisaged a hexagon periodic arrangement energy absorption structure. Based on the shell theory, the mechanical model of the impact resistant structure and hydraulic support was constructed using the finite element method. The mechanical properties of the hydraulic support under a full impact and a partial load impact of the roof were analysed, and the impact resistant structure was designed to prove the reliability of the structure. The results showed that the anti-impact structure reduced the stress and stress fluctuation of the column and effectively reduced the shape variable of the weak link of the hydraulic support. Furthermore, a delay in the time was observed, when the pressure of the hydraulic cylinder reached the yield strength, and there was a gain in the time for the opening of the large flow safety valve. Especially, under the action of partial load, the column did not bend, and the hydraulic cylinder was in the elastic range. Our results can provide new insights in the support of rock burst working face, which is of great significance concerning safety in the coal mining.

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Energy absorption study of aluminium profiles with variety of filling configurations

Bogusz P., Stankiewicz M., Sławiński M.

Engineering Transactions

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2017

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Vol. 65, iss. 4

543--562

EN

The subject of this paper is research of thin-walled aluminium profiles filled with different materials and subjected to dynamic load. The aim of this study was to determine the crashworthiness capabilities of the tested elements. Such structures can be used as elements minimalising the effects of blast wave load on military vehicles and occupants carried thereon. The blast wave generated during the explosion of explosives, especially improvised explosive devices(IED), under or near a combat vehicle poses a deadly threat to the crew and passengers inside the vehicle. The idea of installing crashworthy structures in a vehicle seat to protect the crew and passengers is not new. It was found useful in aviation, automotive or railway industry. In this paper, circular aluminium profiles of an external diameter of 50 mm and thickness of 2 mm were investigated. They were filled with three kinds of materials: cork, foamed aluminium of low density and foamed aluminium of high density. The dynamic tests were performed on a spring hammer apparatus. The energy absorbing structures and materials used to fill the aluminium profiles were examined separately in static compression tests. The characteristics of force-displacement response of the investigated structures were determined, compared and analysed. The energy absorbing characteristic parameters were obtained and discussed to determine the best option.

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Experimental support for numerical simulations of energy absorbing structures

Ochelski S., Gotowicki P.

Journal of KONES

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2008

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Vol. 15, No. 1

183-217

EN

This paper presents experimental investigations of mechanical properties of materials used in the absorbing energy structures. Numerous experimental investigations are essential to develop a reliable numerical model of composite structures absorbing the impact energy. This model should correctly describe the dissipation of kinetic impact energy in the progressive crush process. Mechanical properties of composite materials like elastic modulus, strength, failure strains with influence of anisotropic properties are obtained experimentally. Different strength hypotheses are used for fibrous composites. The investigations on the complex stress state allow determining which of these theories describes the composite best. It was proved that both the matrix type and the structure of the composite have a very large influence on the SEA (Specific Energy Absorption), in particular on their crack propagation resistance. The dependence between the energy absorbed by a single energy absorbing element and a fragment of the structure absorbing the impact energy was discussed. Friction forces play the important role in the progressive crush of composites and they should be taken into account in developing a valid numerical model. Some authors state that the friction forces absorb 40% of the impact energy. The influence of failure strain rates on the absorbing energy capability, which is not clearly defined in the literature about composite structures, was also discussed.

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Porównanie energochłonności konstrukcji przekładkowych typu sandwicz z wypełnieniem oraz cienkościennych struktur falistych

Ochelski S., Bogusz P.

Biuletyn Wojskowej Akademii Technicznej

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2008

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Vol. 57, nr 1

145-157

PL

W pracy opisano badania eksperymentalne konstrukcji energochłonnych. Dokonano porównania wyników zdolności pochłaniania energii uderzenia struktur typu sandwicz z wypełnieniem z tworzywa spienionego oraz cienkościennych konstrukcji energochłonnych z rdzeniem z powłoki falistej. Wykonano próbki z użyciem kompozytu epoksydowego wzmocnionego matą szklaną, tkaniną szklaną i tkaniną węglową. Struktury faliste ze wzmocnieniem włóknami węglowymi wykazały najwyższą wartość względnej energii absorpcji.

EN

The work presents experimental studies of energy absorbing structures. The presented investigation covers absorbing impact energy capability results of sandwich structures with a core made of composite plates filled with foamed material (PVC) and composite thin-walled waved constructions. The specimens were made of glass mat, glass fabric, and carbon fabric reinforced with epoxy resin. The waved thin-walled energy absorbing structures reinforced with carbon fabric proved to be the best.

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Zasady doboru parametrów elementów konstrukcji energochłonnej

Ochelski S.

Prace Naukowe Politechniki Warszawskiej. Mechanika

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2007

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z. 219

173--186

PL

W pracy podano wskazówki pozwalające opracować element konstrukcji energochłonnej w zależności od energii kinetycznej uderzenia. Przedstawiono wyniki własnych badań doświadczalnych wpływu: rodzaju osnowy i wzmocnień kompozytów, struktury, kształtów i grubości elementów na zdolność pochłaniania energii.

EN

The work presents various methods of development of the energy absorbing structure elements depending on impact kinetic energy. The presented investigation covers experimental tests of the influence of different factors: matrix and reinforcement type, structure, shape and element thickness on energy absorption capability.