1,721,029 research outputs found
A novel body centered cubic 3D auxetic chiral geometry
Full text linkAuxetic materials and structures have a negative Poisson's ratio (PR), which means that they expand under a longitudinal tensile loading and shrink under compressive load. This property gives them an increased shear resistance, damping and energy absorption capabilities. Chiral geometries are among the most effective auxetic structures for their ability to convert the axial loading in the rotation of their internal nodes. In the present work, a novel 3D chiral geometry is presented, and its response is investigated both experimentally and numerically. It is made of spheres placed following a Body Centered Cubic lattice; each one connected to the closest neighbors by eight ligaments. A sample was 3D-printed and mechanically tested in compression exhibiting an auxetic behavior in certain directions. A Finite Element model was then developed, successfully reproducing the outcome of the experimental tests, both in terms of force and PR. Then, a numerical testing campaign was performed on representative units constrained using periodic boundary conditions. This campaign allows to evaluate the mechanical properties of the structure as a function of its geometrical parameters. It shows to be able to exhibit an approach a PR of -1 in all the directions. Moreover, the relationship between the sphere's rotation, PR and instability was investigated
Experimental and computational evaluation of tensile properties of additively manufactured hexa- and tetrachiral auxetic cellular structures
Full text linkThe auxetic cellular structures with two different chiral geometries (tetrachiral and hexachiral) were fabricated using laser powder bed fusion (LPBF) technology from two different materials (aluminium alloy AlSi10Mg and stainless steel AISI 316L). The specimen's microstructure, porosity and surface texture were observed by X-ray diffraction, optical and electron microscopy and micro-computed tomography. The mechanical properties of all specimens were determined experimentally with a simple tensile test. The results show that hexachiral and tetrachiral auxetic structures have similar initial stiffness, whereas the former provides a more ductile response with more than four times larger failure strain. The AISI316L steel provides for a much more ductile response than AlSi10Mg at comparable normalised load-carrying capability. The samples' deformation behaviour was analysed with the digital image correlation and tracking method, where it was shown that hexachiral samples exhibit a lower Poisson's ratio. The experimental results were used to validate the corresponding computational models, providing a more detailed analysis of deformation behaviour. They allow for cost-effective parametric studies and the development of new optimised chiral geometries
Mechanical behaviour analysis of an auxetic crash box
Full text linkV magistrski nalogi je predstavljena analiza mehanskega obnašanja avksetičnega absorberja trkov. Edinstvena lastnost avksetične strukture je, da imajo negativen Poissonov koeficient. Obravnavani absorberji, z osnovno celico oblike vbočenih šestkotnikov, so bili sestavljeni iz dvanajstih panelov upognjenih pod predpisanimi koti in zlepljeni skupaj v predpisano geometrijo. Obravnavali smo tri absorberje različnih debelin in pa gradiranega, kateri je bil sestavljen iz štirih panelov vseh treh različnih debelin. Z uporabo računalniških simulacij, ob uporabi metode končnih elementov, smo analizirali njihov odziv ob trku. Rezultate simulacij smo nato primerjali z rezultati eksperimentov, da smo validirali simulacijske modele. Iz rezultatov simulacij pa smo nato še izračunali najpomembnejše mehanske karakteristike absorberjev.The master\u27s thesis presents an analysis of the mechanical behavior of an auxetic crash absorber. A unique feature of auxetic structures is that they have a negative Poisson\u27s ratio. The absorbers observed in the study, had a concave hexagon-shaped base cell and consisted of twelve panels bent at prescribed angles and glued together to the prescribed geometry. The study considered three absorbers of different thicknesses and a graded one, which consisted of four panels of all three different thicknesses. Using computer simulations with the finite element method, we analyzed their collision response. The simulations results were then compared to the experimental results to validate the simulations models. From the results of the simulations, we then also calculated the most important mechanical characteristics of the crash absorbers
Development of new auxetic metamaterial geometries
Full text linkV magistrskem delu je zajeto modeliranje novih avksetičnih struktur, katere bi s svojim edinstvenim obnašanjem lahko v bodoče uporabili na širšem področju strojništva, medicine, tekstilstva idr. Avksetični metamateriali imajo to lastnost, da izkazujejo negativno Poissonovo razmerje. V delu je bilo na podlagi treh osnovnih oblik modalne analize Kelvinove celice opravljeno večje število potencialnih novih struktur, katere bi se lahko obnašale avksetično. Računalniške simulacije so bile izvedene znotraj programskega okolja LS-DYNA, kjer so bile nove strukture postavljene med dve plošči. Celotna struktura je bila tlačno obremenjena, nato je bil spremljan deformacijski odziv določene strukture. Zajeti so bili podatki o spremembah širine in dolžine posamezne strukture, čemur je sledil izračun napetosti in deformacij. V simulacijah je bila variirana debelina medceličnih povezav od 0,3 do 0,6 mm, nakar je bil spremljan deformacijski odziv. Na koncu so bili rezultati simulacij tudi obdelani in primerjani med seboj. Za vsako novo strukturo je bilo izračunano tudi pripadajoče Poissonovo razmerje, zatem je bilo ovrednoteno, ali je obnašanje avksetično ali ne.This master\u27s thesis covers the modeling of novel auxetic structures that could find future applications with their unique properties in broader fields such as mechanical engineering, medicine, the textile industry, etc. Auxetic metamaterials possess the property of exhibiting a negative Poisson\u27s ratio. In this work, a large number of potential new structures that could exhibit auxetic behavior were investigated using three basic forms of modal analysis of the Kelvin cell. The computer simulations were conducted within the LS-DYNA software environment, with the new structures positioned between two panels. The structures underwent pressure loading, and subsequently, the response of each structure was observed. Data on the changes in the width and length of each structure were captured, followed by the calculation of stresses and strains. During the simulations, the thickness of the linear elements varied from 0,3 to 0,6 mm, and the deformation response was monitored. Finally, the results of the simulations were processed and compared with one another. For each novel structure, the corresponding Poisson\u27s ratio was calculated, after which it was evaluated whether the behavior was auxetic or not
Characterization of deformation and mechanical behaviour of the auxetic composite metamaterial
Full text linkPrispevek predlaga inovativen večmaterialen pristop za vpeljavo avksetičnega obnašanja v področje sintaktičnih pen. Z natančnim oblikovanjem velikosti, oblike in orientacije sintaktične pene je bilo doseženo avksetično deformacijsko obnašanje. Najprej so bili iz ekspandiranega perlita in mavca izdelani šestkotni elementi v obliki peščene ure, nato pa je bil avksetični vzorec teh elementov razporejen v škatlo iz nerjavnega jekla. Prazni prostori med vložki so bili zapolnjeni z aluminijevo zlitino (A356) s pomočjo uporabe tehnike proti gravitacijskega litja. Vliti avksetični kompozit je imel gostoto 1,52 g/cm3. Izdelan preizkušanec je bil nato deformiran s kvazi-statično obremenitvijo, da bi lahko okarakterizirali njegovo deformacijsko obnašanje in določili njegove mehanske lastnosti, zlasti Poissonovo število. Deformacija kompozita je bila avksetična s Poissonovim številom -1,04. Za boljše razumevanje mehanizma in zagotavljanje možnosti za nadaljnjo optimizacijo geometrije so bile izvedene računalniške simulacije po metodi končnih elementov.This thesis proposes an innovative multi-material approach for introducing auxetic behaviour to syntactic foams (SFs). By carefully designing the size, shape, and orientation of the SFs, auxetic deformation behaviour was induced. Re-entrant hexagon-shaped SF elements were fabricated using expanded perlite (EP) particles and a plaster of Paris slurry first. Then an auxetic pattern of these SF elements was arranged within a stainless-steel casting box. The empty spaces between the SF elements were filled with molten aluminium alloy (A356) using the counter-gravity infiltration casting technique. The cast auxetic composite had a bulk density of 1.52 g/cm3 . The cast composite was then compressed under quasi-static loading to characterise its deformation behaviour and to determine the mechanical properties, especially the Poisson’s ratio. The cast composite deformation was auxetic with a Poisson’s ratio of −1.04. Finite Element (FE) simulations were conducted to understand the deformation mechanism better and provide means for further optimisation of the geometry
Strength analysis of aluminium slab manipulator components
Full text linkV diplomskem delu je obravnavan manipulator aluminijastih bram, ki se uporablja za transport in manipuliranje težkih aluminijastih bram v industriji. Z uporabo programa PrePoMax je bila izvedena numerična analiza vilic manipulatorja, s katero smo preučili mehansko obnašanje posameznih komponent. Pri diskretizaciji geometrijskega modela je bila uporabljena metoda končnih elementov, za izbor ustrezne mreže pa je bila izvedena konvergenčna analiza. Dobljeni rezultati so ustrezno analizirani ter nudijo vpogled v trdnostne lastnosti komponent ter možne izboljšave njihove zasnove.The thesis addresses an aluminum bar manipulator, which is used for the transport and manipulation of heavy aluminum bars in the industry. Using the PrePoMax software, a numerical analysis of the manipulator\u27s grippers was performed to study the mechanical behavior of the individual components. The finite element method was used for the discretization of the geometric model, and a convergence analysis was conducted for selecting an appropriate mesh. The obtained results are adequately analyzed and provide insights into the strength properties of the components and possible improvements in their design
Design and manufacturing of electrohydraulic press in company galvanizacija Fric d.o.o.
Full text linkV diplomskem delu je predstavljeno področje hidravličnih stiskalnic, ki so v današnjem času nepogrešljive v industriji. Poznamo več tipov hidravličnih stiskalnic, ki imajo velike zmožnosti upravljanja raznolikih nalog. V prvem delu diplomskega dela je na kratko predstavljeno podjetje Galvanizacija Fric d. o. o. ter hidravlične stiskalnice, njihove vrste in njihovo delovanje. V drugem delu je opisan celotni postopek izdelave hidravlične stiskalnice, ki bi se uporabljala za stiskanje odpadnega materiala, kot so papir, karton in folija. Sama konstrukcija stiskalnice je zasnovana iz kovinskega ogrodja, katerega smo spojili z MIG-MAG varjenjem. Potisna plošča, namenjena stiskanju odpadne embalaže, je operirana s hidravličnim cilindrom. Ta cilinder je nato povezan na hidravlični generator, kar pomeni, da je v sklopu enega sistema hidravlična črpalka, elektro-hidravlični potni ventil z dvema hitrima spojkama in rezervoarjem za olje. Vse skupaj se zaključi z natančnim izračunom dejanske moči stiskalnice.The field of hydraulic presses, which are indispensable in today’s industry, is presented in the thesis. We know several types of hydraulic presses that have great capabilities for handling diverse tasks. In the first part of the thesis, there is a brief presentation of a firm Galvanizacija Fric d. o. o. and the hydraulic presses themselves- their types, and their operation. The second part describes the entire process of making a hydraulic press that would be used to press waste materials such as paper, cardboard and foil. The construction of the press itself is designed from a metal frame, which we fused with MIG-MAG welding technology. The push plate, intended for compressing waste packaging, is operated by a hydraulic cylinder. This cylinder is the connected to a hydraulic generator, which means that a hydraulic pump, an electro-hydraulic travel valve with two quick coupling, and an oil tank are part of one system. It concludes with an accurate calculation of the actual power of the press
Parametric modeling of a pipe delivery device
Full text linkV diplomskem delu je bil razvit parametrični model naprave za podajanje cevi grelcev za bojlerje, pri čemer bo podjetje KEV, d. o. o., končni izdelek dobavljalo podjetju TIKI HVAC, d. o. o. Izdelani sta bili dve napravi za tri dimenzije cevi, in sicer Ф16, Ф12 in Ф10. Določene so bile ključne dimenzije, funkcionalnosti in izboljšave, ki so omogočile večjo fleksibilnost in avtomatizacijo proizvodnje.For the purpose of this paper, a parametric model of a pipe delivery device for water heaters was developed. The final product will be supplied by the KEV company to the TIKI HVAC company. Two devices were designed to accommodate three different pipe dimensions: Ф16, Ф12 and Ф10. Key dimensions, functionalities and improvements were defined, allowing greater flexibility and automation of the production process
Parametric modeling of the rinsing unit of the beverage filling system
Full text linkV diplomski nalogi se obravnava parametrično modeliranje izpiralne enote polnilnega sistema za pijače podjetja Vipoll, d. o. o., ki se ukvarja z izdelavo polnilnih sistemov za živilsko industrijo. Poudarjena je pomembnost izpiranja embalaže in zagotavljanje higiene ter kakovosti. Glavni cilj je parametrizacija izpiralne enote, določitev ključnih parametrov in izdelava parametričnega modela z različnimi konfiguracijami. Celotni model je izdelan v programskem paketu SolidWorks 2023, kar omogoča hitrejše načrtovanje in zmanjšuje potrebo po ponovnem modeliranju podobnih elementov. Prav tako je prikaz modela v virtualnem svetu potrdil, da je model pripravljen za izdelavo.The thesis addresses the parametric modeling of the rinsing unit of a beverage filling system by Vipoll d.o.o., a company engaged in manufacturing filling systems for the food industry. The importance of rinsing containers to ensure hygiene and quality is emphasized. The main goal is the parametrization of the rinsing unit, the determination of key parameters, and the creation of a parametric model with various configurations. The entire model is developed using the SolidWorks 2023 software, which enables faster design and reduces the need for re-modeling similar elements. The virtual display of the model confirmed that it is ready for production
Strength Analysis of Machine Frame Variants
Full text linkV magistrskem delu je obravnavano zgornje ogrodje stroja za vezanje lesenih letev v
pakete. Izvedena je bila trdnostna analiza obstoječega ogrodja z uporabo metode končnih elementov. Sledil je analitičen preračun obstoječe gibalne navojne zveze. Razvitih je bilo pet novih variantnih rešitev ogrodja, ki so bile trdnostno analizirane. Na podlagi rezultatov analiz in zahtevnika je bila kot najboljša izbrana variantna rešitev številka dve, saj je imela za 21 % manjši poves ogrodja.In the master’s thesis, the upper frame of the machine for strapping wooden slats into packages is discussed. A strength analysis of the existing frame was conducted using the finite element method. This was followed by an analytical calculation of the existing threaded spindle with nut. Five new variant solutions for the frame were developed and strength analysed. Based on the results of the analyses and the requirements, variant solution number two was chosen as the best, as it had a 21% lower deflection of the frame
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