Sandwich panels have the best stiffness-to-lightness ratio, which is what makes them very useful in industrial applications. This paper is focused on a study of the buckling capacities of the core components under uniaxial compression. The critical buckling loads for various core densities and materials of honeycomb panels were experimentally and numerically investigated. The specimens under lateral loading showed three zones: zone 1 is the initial elastic state, followed by the plateau region in zone 2, while zone 3 shows a monotonically stiffening region, associated with the densification of the material. The effect of the core density and its materials on the behavior and the damage was highlighted. From the experiment it is clear that the buckling load of the specimens increases as the core density is increasing. In terms of stiffness and load at failure, the honeycomb sandwich panel had better mechanical characteristics than its components. The study also calculated the numerical buckling loads of the panels using the ABAQUS finite-element analysis program. The achieved experimental and numerical results were compared with each other. In conclusion, a good correlation between theory and experiment was found. Keywords: honeycomb sandwich panel, buckling analysis, compression, finite-element method, collapse Sendvi~ni paneli imajo najbolj{e razmerje med togostjo in maso. To jih dela primerne za industrijsko uporabo. Ta~lanek je usmerjen v {tudij zdr`ljivosti za upogibanje klju~nih komponent pri enoosni tla~ni obremenitvi. Eksperimentalno in numeri~no so bile preiskane kriti~ne upogibne obremenitve za razli~ne klju~ne gostote in material satastih plo{~. Vzorci, stransko obremenjeni, so pokazali tri podro~ja: podro~je 1 je za~etno elasti~no stanje, ki mu sledi podro~je platoja, tj. podro~je 2. Podro~je 3 prikazuje monotono upogibanje, povezano z zgo{~evanjem materiala. Ocenjen je bil vpliv klju~ne gostote in materialov glede vedenja in po{kodb. Iz preizkusov je razvidno, da z nara{~anjem klju~ne gostote nara{~a tudi odpornost proti upogibni obremenitvi vzorcev. Glede na upogibanje in obremenitev pri poru{itvi ima satasta sendvi~na plo{~a bolj{e mehanske lastnosti v primerjavi z njenimi komponentami. V {tudiji je tudi izra~unana numeri~na upogibna obremenitev panelov z analizo kon~nih elementov s programom ABAQUS. Primerjani so dobljeni eksperimentalni in numeri~ni rezultati. Dobljena je bila dobra korelacija med teorijo in eksperimentalnimi rezultati. Klju~ne besede: satasta sendvi~na plo{~a, analiza upogibanja, tla~enje, metoda kon~nih elementov, poru{itev

No abstract

Profile shift has an immense effect on the sliding, load capacity, and stability of involute cylindrical gears. Available standards such as ISO/DIS 6336 and BS 436 DIN/3990 currently give the recommendation for the selection of profile shift coefficients. It is, however, very approximate and usually given in the form of implicit graphs or charts. In this article, the optimal selection values of profile shift coefficients for cylindrical involute spur and helical gears are described, using a differential evolution algorithm. The optimization procedure is developed specifically for exact balancing specific sliding coefficients at extremes of contact path and account for gear design constraints. The obtained results are compared with those of standards and research of other authors. They demonstrate the effectiveness and robustness of the applied method. A substantial improvement in balancing specific sliding coefficients is found in this work.

Abstract

In this research, a hexagonal honeycomb core under a compressional load is studied numerically from the initial elastic regime to the fully crushed state using the Abaqus finite-element modelling. Two modelling approaches, i.e., a static analysis and an explicit non-linear analysis are applied to a 3D model of an aluminium honeycomb core. This honeycomb structure is compressed quasi statically using rigid plates and displacement control. Moreover, the crushing of the honeycomb-core structure and the failure due to buckling are verified numerically, and a study is also performed to show how different densities, cell sizes and specimen sizes can affect the average crush force and plateau force. A comparison between experimental and numerical results is drawn, showing that the numerical models can effectively predict the mean crushing force and mechanical behaviour with a good accuracy.Avtorji so raziskovali obna{anje jedra heksagonalnega satovja pod tla~no obremenitvijo. Numeri~na {tudija, izvedena s pomo~jo metode kon~nih elementov na programskem orodju Abaqus, je potekala od za~etnega elasti~nega re`ima do popolne poru{itve strukture. Uporabili so dva pristopa k modeliranju, to je: stati~no analizo in eksplicitno nelinearno analizo 3D modela jedra satovja iz izbrane Al zlitine (AlMg3). Izbrana struktura v obliki satovja je bila kvazi-stati~no tla~no obremenjena z uporabo togih plo{~v re`imu kontrole pomika. Nadalje so avtorji numeri~no verificirali poru{itev strukture zaradi njene deformacije. Numeri~na {tudija je tudi pokazala, kako razlike v gostoti, velikosti celic in velikosti same strukture vplivajo na povpre~no in maksimalno obremenitev, ki sta potrebni za njeno poru{itev. Izvedli so primerjavo med eksperimentalno dobljenimi rezultati in rezultati numeri~nih simulacij. Izkazalo se je, da se dobljeni rezultati med seboj dobro ujemajo ter da lahko numeri~ni model dokaj natan~no napove povpre~no obremenitev, potrebno za poru{itev dane strukture. Klju~ne besede: sendvi~struktura, jedro satovja iz Al zlitine, tla~na obremenitev, deformacije, poru{itev, numeri~na analiza na osnovi metode kon~nih elementov UDK 620.1:669.715:620.173