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This study investigated the effect of fiber ratio on the impact behavior of polypropylene fiber reinforced concrete cube and beam samples. Plain concrete mixtures for control samples and polypropylene fiber-reinforced concrete mixtures with fiber ratios of %0.22, %0.44, and %0.66 by volume were prepared. An instrumented drop-weight impact system was used for the dynamic tests. Static compression tests, three-point bending tests, and impact tests were performed on beam samples (with the dimension of 100×100×500 mm). Static compression and impact tests were performed on cube samples (with the size of 100 mm). It was observed that the fracture properties of polypropylene fiber reinforced concrete for both cube and beam samples were better than the control samples under impact. The crack width in the beams under the impact decreased with the increase in polypropylene fiber ratio. The cube and beam concrete samples reinforced with polypropylene fibers absorbed the impact energy better than the control samples.

Bu çalışmada çelik lif takviyeli beton kirişlerde lif oranının eğilmede çarpma davranışına etkisi araştırılmıştır. Çelik lif oranı ile eğilmede çarpma davranışı arasındaki ilişkinin belirlenmesi amacıyla aletli ağırlık düşürme sistemi kullanılmıştır. Çalışma için kontrol karışımının yanı sıra beton hacminin % 0.25 (19.5 kg/m³), % 0.50 (39 kg/m³) ve % 0.75 (58.5 kg/m³) oranlarında çelik lif takviyeli beton karışımları üretilmiştir. Deneyler için 100x100x500 mm boyutlarında kirişler üretilmiştir. Kirişler üzerinde basınç, eğilme ve aletli ağırlık düşürme deneyleri yapılmıştır. Ayrıca ağırlık düşürme deneyleri sonucunda kiriş ortasında meydana gelen çatlak genişliği ölçümü yapılmıştır. Aletli düşen ağırlık sistemi kullanılarak yapılan düşük hızlı darbe deneylerde ise çelik lif takviyeli betonların kontrol numunesine kıyasla ani kırılmaya karşı daha dirençli olduğu görülmüştür. Ayrıca çelik lif miktarının artması ile düşük hızlı darbe deneyi sonucunda kirişlerde oluşan çatlak genişliklerinin azaldığı tespit edilmiştir. Yapılan çalışma sonucunda çelik lifin betonun statik ve dinamik özelliklerine olumlu etkilerinin olduğu görülmüştür., In this study, the effect of steel fiber ratio on the flexural impact behavior of concrete beams was investigated. An instrumented drop weight system was used to determine the relationship between steel fiber ratio and impact behavior in flexure. In addition to the control mixture, steel fiber added concrete mixtures were produced in the ratios of 0.25% (19.5 kg / m³), 0.50% (39 kg / m³) and 0.75% (58.5 kg / m³) of the concrete volume for the study. Beams with the dimension of 100x100x500 mm were produced for the experiments. Pressure, flexural, and instrumented drop weight tests were performed on the beams. In addition, the width of the cracks formed in the middle of the beam because of the drop weight tests was measured. In the low-velocity impact tests performed using an instrumented drop weight system, it was observed that the steel fiber-reinforced concretes were more resistant to sudden fracture compared to the control sample. In addition, because of the low-velocity impact test, it was determined that as the amount of steel fiber increases, the crack widths decrease. As a result of the study, it has been observed that steel fiber has positive effects on the static and dynamic properties of concrete.

Bu çalışmada, “Deprem Etkilerinin Tamamının Moment Aktaran Süneklik Düzeyi Yüksek Betonarme Çerçevelerle Karşılandığı Taşıyıcı Sistemler” ile “Deprem Etkilerinin Tamamının Süneklik Düzeyi Yüksek Boşluksuz Betonarme Perdelerle Karşılandığı Taşıyıcı Sistemler” maliyet ve deprem performansları bakımından karşılaştırmalı olarak irdelenmiştir. Bu amaçla 18 katlı konut tipi bir bina esas alınmış ve her iki taşıyıcı sistemi karşılaştırmak üzere STA4CAD yazılımında iki farklı model hazırlanmıştır. Türkiye Bina Deprem Yönetmeliği-2018 (TBDY 2018) esas alınarak yapılan analizlerden her iki modelle elde edilen maliyetler karşılaştırılmıştır. Çok Modlu İtme Yöntemi kullanılarak yapılan analizler sonucunda elde edilen eleman hasar durumları üzerinden yapılan değerlendirmede perdeli modelin deprem performansının çerçeveli modelin performansından daha iyi olduğu gözlenmiştir. Kaba yapı maliyeti esas alınarak yapılan karşılaştırmada, deprem etkilerinin tamamının betonarme perdelerle karşılandığı taşıyıcı sistem modelinin, deprem etkilerinin tamamının betonarme çerçeveler ile karşılandığı taşıyıcı sistem modeline kıyasla daha ekonomik olduğu gözlenmiştir.

Bu çalışmada, ülkemizde yapılabilecek 14 katlı betonarme bir konut binası için deprem yönetmeliğinde verilen tasarıma esas olabilecek taşıyıcı sistem türleri karşılaştırmalı olarak irdelenmiştir. Süneklik düzeyi yüksek olan salt çerçeveli, salt perdeli ve plandaki perde oranı düşük ve yüksek olan iki adet çerçeveli-perdeli model tasarlanmıştır. Bunlara ilaveten beşinci model olarak süneklik düzeyi karma çerçeveli-perdeli bir taşıyıcı sistem modeli tasarlanmıştır. Deprem yönetmeliğimizde belirtildiği şekilde dayanıma göre tasarım yaklaşımı ile doğrusal analizler yapılmıştır. Modeller arasında taban kesme kuvveti ve tepe deplasmanı dağılımları karşılaştırılmıştır. Her iki büyüklük için de dağılımların çok büyük oranda 1/R ilişkisine benzer şekilde gerçekleştiği görülmüştür. Çalışma kapsamındaki modeller arasında perde oranı arttıkça maksimum deprem deplasmanları artış göstermiştir. Zemin katlardaki hasar durumuna göre, en fazla hasar salt çerçeveli modelde, en az hasar ise salt perdeli modelde gözlenmiştir. En düşük maliyet salt perdeli model için hesaplanmış olup bu model salt çerçeveli modelin kaba yapı maliyetinden yaklaşık olarak %5 daha ekonomiktir., In this study, the types of structural systems that can be the basis for the design given in the earthquake code for a 14-story reinforced concrete residential building that can be built in our country are examined comparatively. A high ductility level of models is designed, which comprised of frames only, of walls only, and combinations of frames and walls one with a low wall ratio and the other with a high wall ratio in the plan. In addition, a fifth structural model -with a mixed ductility level- with the combinations of frames and walls is designed. Linear analyzes are carried out with the strength-based design approach as specified in our earthquake code. The base shear force and peak displacement distributions among the models are compared. It has been seen that the distributions for both parameters are very similar to the 1/R relationship. Maximum seismic displacements increased as the wall ratio in the plan increased, within the scope of the study. According to the damage status of ground floors, the maximum damage is observed for the model comprised of frames only, and the least damage is for the model comprised of walls only. The lowest cost is obtained for the model comprised of walls only, which is approximately 5% more economical than the construction cost of the model comprised of frames only.

Efficient lightweight solutions are of great interest in many industries (aviation, automotive) particularly regarding the limitation of CO2-emissions and material waste. An innovative strategy to address these challenges is the use of hybrid manufacturing. Additive manufacturing (laser metal deposition, LMD) and conventional forming methods (hole-flanging) are used to optimize and functionalize AA 6016 sheet metal parts, which are widely used in the manufacturing of car body parts. First of all, the effects of the additive reinforcements on the mechanical and microstructural properties are investigated using tensile and microstructural tests. After manufacturing reinforced blanks and performing subsequent forming operations, the parts are investigated regarding damages and functionalized through threading. This allows the application of a bolt connection, which is tested through rip-off tests to evaluate the effect of the reinforcements on the fracture forces. It can be shown, that reinforcements can be manufactured without defects and virtually no porosity and the formability is only slightly reduced compared to conventional materials. At the same time, the performance of the reinforced bolt joint can be enhanced while the increase in weight can be limited to relatively small amounts., Production Engineering, 15 (2)

Bu çalışmada, Türkiye Bina Deprem Yönetmeliği (2018) ve Deprem Bölgelerinde Yapılacak Binalar Hakkında Yönetmelik (2007) kapsamında bina yüksekliğinin, toplam eşdeğer deprem yükü (taban kesme kuvveti) ve maksimum tepe deplasmanı üzerindeki etkisi karşılaştırılmalı olarak incelenmiştir. Bu amaçla ele alınan yapı örneği, ETABS bilgisayar programında, başta 30 kat olarak modellenmiş ve yapılan her analiz sonrası 1 adet ara kat eksiltilerek 5 ile 30 katlar arasındaki 26 adet model için analizler tekrarlanmıştır. Yapının 15 metre ile 91 metre arasında değişen yüksekliklere sahip modelleri için Mod birleştirme yöntemine göre hesaplanmış olan taban kesme kuvveti ve maksimum tepe deplasmanı gibi büyüklükler kaydedilmiştir. TBDY 2018 esas alınarak elde edilen taban kesme kuvveti değerlerinin TDY 2007 esas alınarak elde edilen taban kesme kuvveti değerlerinden çok daha düşük değerler aldığı gözlenmiştir. TBDY 2018 esas alınarak elde edilen taban kesme kuvveti değerlerinin ise yapı yüksekliği arttıkça doğrusala yakın bir ilişki ile azaldığı gözlenmiştir. Ayrıca taban kesme kuvveti değerlerinin yakın olması halinde, TBDY 2018 esas alınarak elde edilen maksimum tepe deplasmanı değerlerinin TDY 2007 esas alınarak elde edilen maksimum tepe deplasmanı değerlerinden çok daha büyük olduğu gözlenmiştir., In this study, the effect of the building height on the total equivalent seismic load (base shear) and the maximum top displacement was examined comparatively, within the scope of the Turkish Earthquake Code 2007 and 2018. The structure sample handled for this purpose was modeled as 30 storey at first in the ETABS computer program and after each analysis, 1 intermediate floor was decreased and analyzes were repeated for 26 models between 5 and 30 floors. For models of the building with heights ranging from 15 meters to 91 meters, values such as the base shear force and maximum top displacement obtained according to the response spectrum analysis were recorded. It was observed that the base shear force values obtained based on the 2018 earthquake regulation are much lower than the values obtained based on the 2007 earthquake regulation. It was observed that the base shear force values obtained based on the 2018 earthquake regulation decreased in linear relation with the increase in the height of the building. In addition, in case of equivalent values for base shear forces, it was observed that the maximum top displacement values obtained based on the 2018 earthquake regulation are much larger than the values obtained based on the 2007 earthquake regulation.

In this paper, multi-axis single stage incremental hole-flanging is explored in place of three axis multi-stage tool paths in order to prevent flange conicity in hole-flanging by single point incremental forming (SPIF). The angle of inclination of the forming tool, the starting radius and step size of the tool paths are varied to investigate the feasibility of new tool paths. Using the proposed tool paths, an optimization is performed by Finite element (FE) analyses. The geometrical accuracy of the flange is maintained within tolerances relevant to industrial applications while minimizing the resultant forces acting on the tool and maintaining high formability (hole expansion ratio, HER). The FE analyses of the process reveal low formability and high forming forces for flanges formed at high angles of inclination of the forming tool. The tool paths with small diameters at the start point of the tool path result in high bulge heights and high resultant forces. Hence, the existing three axis tool paths are better than the proposed strategies. To prevent flange conicity, over bending of the flange edge to compensate for springback after forming is implemented on the three axis tool path strategy. This is achieved by adding a second tool path with an over bend angle at the end of the three axis tool path., Procedia Manufacturing, 47, ISSN:2351-9789, 23rd International Conference on Material Forming

Additive manufacturing (AM) offers the possibility of locally reinforcing sheet metal or sheet metal products by adding patches that are metallurgically bonded to the substrate. Due to the high design freedom of AM, patches can be easily adapted to loads in geometry and thickness. However, the heat input and the high cooling rates during AM processes have a strong influence on the microstructure in the patch as well as in the substrate, which will affect forming properties. The aim of this work is to investigate the influence of patches produced by laser material deposition (LMD) on formability of micro-alloyed sheet metals. After determining a suitable process window for metallurgically bonded patches without cracks and pores, investigations were carried out on the microstructure and mechanical properties of reinforced samples. This work includes metallographic examinations using optical microscopy, hardness measurements and tensile tests. The formability of sheets with local reinforcement was investigated by stretching and Nakajima tests. The heat input creates a heat affected zone (HAZ) directly next to the patches with a reduced strength, caused by recrystallization that may lead to failure in the forming process and thus limits the forming capacity of locally reinforced sheet metals. A subsequent laser heat treatment can homogenize the properties in the HAZ., Procedia Manufacturing, 47, ISSN:2351-9789, 23rd International Conference on Material Forming

Wire-arc additive manufacturing is an additive manufacturing technology which allows for high deposition rates and is well suited for manufacturing larger parts in a short time compared to other additive manufacturing technologies. The technology has already received considerable industrial take-up for various materials and applications. The aim of this work is to investigate the alloy EN AW 6016 as wire stock for WAAM. To establish this, aluminum wire was produced by wire drawing. Using this wire, specimens were produced on base plate material using a variety of process parameters. These parts were then used to evaluate the mechanical properties. Further properties such as porosity and hardness were investigated using light optical microscopy. Based on the results, the potential of the alloy for WAAM of lightweight parts is discussed., Procedia Manufacturing, 47, ISSN:2351-9789, 23rd International Conference on Material Forming

Especially in crash relevant car body structures, local reinforcements of sheet metal parts can combine high crash performance and lightweight design. Patchwork blanks (PB) can be used to manufacture locally reinforced hot stampings. However, PB may entail disadvantages like corrosion in the gap between patch and base material or low formability of the joining zone and low shear strength at the spot welds. Additively manufactured local patches with metallurgical bonding to the substrate material are a promising alternative. The patches are generated by Laser Metal Deposition (LMD), where metal powder is melted together with the surface of the substrate to build a metallurgical bond. This new approach has already been tested with steel and aluminum alloys. For hot stamping of 22MnB5 steel, the hardenability of the additively manufactured material is of key importance. With quenching experiments, a similar hardening behavior of additively manufactured 22MnB5 compared to conventional sheet material can be shown. Based on this, a component with additive reinforcements was manufactured by hot stamping. For this purpose, rolled 22MnB5 sheets were locally reinforced by LMD and subsequently formed in a hot stamping process. The formability of locally reinforced sheets and the hardenability of the additively manufactured 22MnB5 patches are analyzed and compared with quenching experiments. Additionally, the hardenability and martensite/bainite transformation of additively manufactured 22MnB5 is investigated using dilatometer experiments and compared to conventional 22MnB5.

Bu çalışmada, hibrit donatılı betonarme kirişlerin yük-deplasman davranışı teorik olarak incelenmiştir. Hibrit donatılı betonarme kesitlerde, çekme veya basınç bölgesinde cam elyaf lifli polimer (GFRP) ve çelik donatılar bir arada kullanılmaktadır. Çalışmada, test verileri literatürde mevcut olan hibrit donatılı (GFRP ve çelik) basit mesnetli 6 adet betonarme kiriş numunesi esas alınmış ve kirişler sayısal bir yöntemle analiz edilmiştir. Kirişlerin yük-deplasman ilişkileri teorik olarak elde edilmiş ve sonuçlar mevcut deneysel çalışmada verilen yük-deplasman eğrileriyle karşılaştırılmıştır. Sayısal yöntemde kirişlerin çatlamış durumdaki efektif eğilme rijitliklerinin hesabında çatlamış kesit analizi ile hesaplanan moment-eğrilik ilişkileri esas alınmaktadır. Sistem deplasmanlarının hesabında rijitlik matrisi yöntemi kullanılmaktadır. Sayısal yönteme dayalı olarak elde edilen yük-deplasman eğrilerinin deneysel sonuçlar ile uyum içerisinde olduğu gözlenmiştir.&nbsp, In this study, load-deflection behavior of hybrid reinforced (GFRP and steel) concrete beams is theoretically investigated. Six hybrid reinforced (GFRP and steel) simply supported concrete beams available in literature were considered and analyzed based on a numerical method. The load-deflection curves of beams are obtained theoretically and the results are compared with the load-deflection curves given in the available experimental study. The moment-curvature relationships calculated by cracked section analysis is taken as basis for the effective flexibilities of the beams in cracked state. The stiffness matrix method is used in the structural analysis. It is observed that the load-deflection curves obtained based on the numerical procedure is in good agreement with the available test results.

New technological challenges like electro-mobility pose an increasing demand for cost-efficient processes for the production of product variants. This demand opens the possibility to combine established die-based manufacturing methods and innovative, dieless technologies like additive manufacturing [1, 2]. In this context, additive manufacturing technologies allow for the weight-efficient local reinforcement of parts before and after forming, enabling manufacturers to produce product variants from series parts [3].Previous work by the authors shows that the optimal shape of the reinforcing structure can be determined using sizing optimization. Sheet metal parts can then be reinforced using laser metal deposition. The material used is a pearlite-reduced, micro-alloyed steel (ZE 630). The aim of this paper is to determine the effect of the additive manufacturing process on the material behavior and the mechanical properties of the base material and the resulting composite material. The parameters of the AM process are optimized to reach similar material properties in the base material and the build-up volume. A metallographic analysis of the parts is presented, where the additive layers, the base material and also the bonding between the additive layers and the base material are analyzed. The paper shows the feasibility of the approach and details the resulting mechanical properties and performance.New technological challenges like electro-mobility pose an increasing demand for cost-efficient processes for the production of product variants. This demand opens the possibility to combine established die-based manufacturing methods and innovative, dieless technologies like additive manufacturing [1, 2]. In this context, additive manufacturing technologies allow for the weight-efficient local reinforcement of parts before and after forming, enabling manufacturers to produce product variants from series parts [3].Previous work by the authors shows that the optimal shape of the reinforcing structure can be determined using sizing optimization. Sheet metal parts can then be reinforced using laser metal deposition. The material used is a pearlite-reduced, micro-alloyed steel (ZE 630). The aim of this paper is to determine the effect of the additive manufacturing process on the material behavior and the mechanical properties of the base material and the resulting composite material. The parameters of the AM ...

Bu çalışmada çekme rijitleşmesinin, FRP ve çelik donatılı betonarme kirişlerin yük-deplasman davranışı üzerindeki etkisi teorik olarak incelenmiştir. Bu amaçla yapılan analizlerde, literatürde mevcut çeşitli deneysel çalışmalarda test edilmiş olan 12 adet FRP ve çelik donatılı kiriş numunesi esas alınmıştır. Çekme rijitleşmesinin eğilme davranışı üzerindeki etkisini incelemek üzere hesaplarda iki bölgeli doğrusal çekme rijitleşmesi modeli kullanılmıştır. Bu modelde çekme rijitleşmesini ?ts parametresi kontrol etmektedir. Yapılan analizlerle, her bir kiriş için ?ts parametresinin 2 ile 25 arasında değişen değerlerine bağlı olarak yük-deplasman eğrisi elde edilmiştir. Analizlerden elde edilen sonuçlar, mevcut deneysel çalışmalarda verilen kiriş numunelerine ait yük-deplasman ilişkileriyle karşılaştırılmıştır. Deney sonuçları ile en uyumlu yük-deplasman ilişkisini sağlayan ?ts değerleri kaydedilmiştir. Sonuç olarak yükdeplasman davranışı belirlenmek istenen FRP ve çelik donatılı betonarme kirişlerin analizi için hesaplarda esas alınması gereken ?ts değerinin, donatı oranı ve donatı elastisite modülü gibi faktörlere bağlı olarak önemli oranda değişkenlik gösterdiği belirlenmiştir In this study, tension stiffening effect on load-deflection behavior of concrete beams reinforced with FRP and steel bars is investigated. A total of 12 FRP reinforced concrete beam specimens, available in the literature, were considered in the analysis. In order to investigate tension stiffening effect on flexural behavior, bilinear tensile stress-strain model was considered for concrete material. In this model the parameter ?ts controls the tension stiffening effect on the load-deflection behavior of the beam. Loaddeflection curves for the specimens were obtained with varying ?ts between 2 to 25, and then were compared with the experimental results. In conclusion it is observed that the value of ?ts to be taken into account for calculations in order to predict load-deflection behavior of reinforced concrete beams significantly depend on the reinforcement ratio and the mechanical properties of reinforcement.

WOS: 000180281800007 Bryozoan and foraminiferal assemblages from a core drilled in the Kusdili (Kadikoy, Istanbul) Upper Pleistocene-Holocene sequence were studied. Assemblages are absent from the very basal and top parts but they are well represented all along the middle part of the sequence. All the species found presently live in the Mediterranean. In the area sedimentation seemingly started about 13 000 years ago in very shallow near-shore environments with the deposition of pebbly sediments rapidly evolving to mud. Near the base, the presence of erosional surface allows to recognize three successive sedimentary cycles. Bryozoan and foraminiferal assemblages found in the middle part of the sequence testify to a shallow water, estuarine or lagoonal paleo-environment, in which effects of low salinity waters, more obvious toward the top, could be related to the reestablishment of a connection between the Marmara Sea and the Black Sea through the Bosphorus, about 7000 years BP. (C) 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved.

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