Search

Copyright of Journal of Polytechnic is the property of Journal of Polytechnic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Çarpışma kutuları araçlarda darbe emici yapılar olarak araçların tampon kısımlarında bulunur. Çarpışma kutularının şekli, çarpışma performansını önemli oranda etkilemektedir. Çarpışma kutuları üzerine yapılan çalışmalarda çok hücreli çarpışma kutularının tek duvardan oluşan çarpışma kutularına göre daha iyi performansa sahip oldukları ortaya koyulmuştur. Çok hücreli çarpışma kutularında dış duvar içerisindeki yapıların geometrisi çarpışma performansını arttırmada önemli rol oynamaktadır. Bu çalışmada her birinin dış duvarı silindirik olan ve içi kare, altıgen, sekizgen ve dairesel kesitler ile eklenmiş dört farklı çarpışma kutusunun performansları incelenmiştir. En iyi performansa sahip olan içerisine dairesel kesit eklenmiş dairesel çok hücreli çarpışma kutusuna çoklu arama stratejileri kullanan çok amaçlı parçacık sürü optimizasyonu (MMOPSO) yöntemiyle optimizasyon çalışması yapılmıştır. Optimizasyon çalışması, radyal temelli fonksiyonlar yöntemi ile elde edilen metamodel kullanılarak gerçekleştirilmiştir. Metamodel, latin hiperküp yöntemi ile belirlenen otuz adet örnekleme noktası kullanılarak oluşturulmuştur.

In this study, behaviour of absorbed energy of empty square tailor-welded tubes having different thickness and welding locations was investigated using the finite element software LS-DYNA with optimization modulus LS-OPT under axial impact loading. As a results, specific energy absorption (SEA), the pick force and crush force efficient (CFE) curves were determined. Also, optimization thickness values were obtained for maximum absorbed energy and minimum peak force. [ABSTRACT FROM AUTHOR]

The Caucasian mobile belt is situated in the area of Late Cenozoic collision of the large Afro-Arabian and Eurasian lithospheric plates. Extensive volcanic activity in the Georgian part of the Caucasian mobile belt took place during the Late Miocene--Holocene. Five volcanic regions have been identified in Georgia; each of them reveals in a greater or lesser degree similarity of tectonic and magmatic processes. Volcanic products are represented by basaltic, doleritic, andesitic basaltic, andesitic dacitic, rhyolitic lavas and their pyroclastics with andesites and dacites prevailing. Using petrochemical and geochemical data the volcanics can be divided into two main rock groups: calc-alkaline and subalkaline series. The marker petrogeochemical series is presented by the medium-to high-K calc-alkaline volcanics. Relative to the heavy elements (HFSE) Y, Nb they are enriched in some large ion lithophile elements (LILE) Rb, Sr, Ba and light rare earth elements (REE) La, Ce. This confirms the leading role of fractional crystallization in forming the volcanics of the study area. These volcanics have the characteristics of pre-collision subduction (increased LILE content and high La/Nb ratios) geodynamic regimes. Volcanic rocks derived from sources displaying different tectonic environments show close petrogeochemical resemblance, indicating the similarity of the melting substrates of magmatic chambers. The findings also allow us to give priority to the magma generation conditions, to its periodical renewal and depths of inception in comparison with the geodynamical factors. Isotopic data (87Sr/86Sr) have confirmed that the subduction-enriched lithospheric mantle material was more important than that of the continental crust components. Sr isotopic ratios do not show marked dependence on the values of the petrochemical composition of the enclosing rocks and on the time of their formation. [ABSTRACT FROM AUTHOR]

The structure and geological history of the Caucasus are largely determined by its position between the still-converging Eurasian and Africa-Arabian lithospheric plates, within a wide zone of continental collision. During the Late Proterozoic-Early Cenozoic, the region belonged to the Tethys Ocean and its Eurasian and Africa-Arabian margins where there existed a system of island arcs, intra-arc rift s, back-arc basins characteristic of the pre-collisional stage of its evolution of the region. The region, along with other fragments that are now exposed in the Upper Precambrian- Cambrian crystalline basement of the Alpine orogenic belt, was separated from western Gondwana during the Early Palaeozoic as a result of back-arc rifting above a south-dipping subduction zone. Continued rifting and seafloor spreading produced the Palaeotethys Ocean in the wake of northward migrating peri-Gondwanan terranes. The displacement of the Caucasian and other peri-Gondwanan terranes to the southern margin of Eurasia was completed by ~350 Ma. Widespread emplacement of microcline granite plutons along the active continental margin of southern Eurasia during 330-280 Ma occurred above a north-dipping Palaeotethyan subduction zone. However, Variscan and Eo-Cimmerian-Early Alpine events did not lead to the complete closing of the Palaeozoic Ocean. The Mesozoic Tethys in the Caucasus was inherited from the Palaeotethys. In the Mesozoic and Early Cenozoic, the Great Caucasus and Transcaucasus represented the Northtethyan realm -- the southern active margin of the Eurasiatic lithospheric plate. The Oligocene-Neogene and Quaternary basins situated within the Transcaucasian intermontane depression mark the syn- and post-collisional evolution of the region; these basins represented a part of Paratethys and accumulated sediments of closed and semiclosed type. The final collision of the Africa-Arabian and Eurasian plates and formation of the present-day intracontinental mountainous edifice of the Caucasus occurred in the Neogene-Quaternary period. From the Late Miocene (c. 9-7 Ma) to the end of the Pleistocene, in the central part of the region, volcanic eruptions in subaerial conditions occurred simultaneously with the formation of molasse troughs. The geometry of tectonic deformations in the Transcaucasus is largely determined by the wedge-shaped rigid Arabian block intensively indenting into the Asia Minor-Caucasian region. All structural-morphological lines have a clearly-expressed arcuate northward-convex configuration reflecting the contours of the Arabian block. However, farther north, the geometry of the fold-thrust belts is somewhat different -- the Achara-Trialeti fold-thrust belt is, on the whole, W-E-trending; the Greater Caucasian fold-thrust belt extends in a WNW-ESE direction. [ABSTRACT FROM AUTHOR]

Major, trace element and K-Ar age determinations are reported for a suite from the Yamadağı volcanics in the Eastern Anatolia. The exposed rocks mainly consist of medium-potassium calc-alkaline basaltic andesites, andesites and dacites. Petrographical data exhibit disequilibrium mineral textures, such as resorption of the ferromagnesian phases, clinopyroxene-mantled orthopyroxene, and sieve-textured plagioclases. The Yamadağı volcanics have a calk- alkaline character, and trace element characteristics exhibit that the volcanics resemble subduction zone volcanics and/or volcanics assimilated by continental crust. K/Ar age determinations show that the Yamadağı volcanics were formed during the 12 ± 0.5 - 15 ± 0.5 Ma time interval. Geochemical characteristics of these volcanics can be attributed to complex petrogenetic processes, including magma mixing and crustal assimilation along with fractional crystallization. [ABSTRACT FROM AUTHOR]