246 research outputs found
Effects of Alloying Elements (Mo, Ni, and Cu) on the Austemperability of GGG-60 Ductile Cast Iron
No full textKonca, Erkan/0000-0001-8943-091X; TUR, KAZIM/0000-0002-8017-8209The interest in austempered ductile irons (ADI) is continuously increasing due to their various advantageous properties over conventional ductile irons and some steels. This study aimed to determine the roles of alloying elements Ni, Cu, and Mo, on the austemperability of GGG-60 ductile cast iron. Two different sets of GGG-60 (EN-GJS-600-3) samples, one set alloyed with Ni and Cu and the other set alloyed with Mo, Ni, and Cu, were subjected to austempering treatments at 290 degrees C, 320 degrees C, and 350 degrees C. A custom design heat treatment setup, consisting of two units with the top unit (furnace) serving for austenitizing and the 200 L capacity bottom unit (stirred NaNO2-KNO3 salt bath) serving for isothermal treatment, was used for the experiments. It was found that austempering treatment at 290 degrees C increased the hardness of the Ni-Cu alloyed GGG-60 sample by about 44% without causing a loss in its ductility. In the case of the Mo-Ni-Cu alloyed sample, the increase in hardness due to austempering reached to almost 80% at the same temperature while some ductility was lost. Here, the microstructural investigation and mechanical testing results of the austempered samples are presented and the role of alloying elements (Mo, Ni, and Cu) on the austemperability of GGG-60 is discussed
Process Design Optimization for the Post-Weld Controlled Accelerated Cooling of R350ht Head Hardened Rail Joints
No full textMantarı sertleştirilmiş rayların kullanımından tam olarak fayda sağlayabilmek için bu rayların kaynak ve ısıdan etkilenen bölgelerinin, mantarı sertleştirilmiş raya özelliğini veren sıkı dizili perlit içyapısının sağladığı mekanik özelliklere yakın özellikler veren içyapılara sahip olması gerekmektedir. Bu ise yanmalı alın kaynağı ile birleştirilmiş raylarda söz konusu bölgelerin kaynak işleminden hemen sonra hızlandırılmış kontrollü soğutulmasıyla mümkün olabilmektedir. Bu çalışmada yanmalı alın kaynağı yöntemiyle birleştirilmiş mantarı sertleştirilmiş R350HT rayların kaynak bölgelerine uygulanacak kontrollü hızlı soğutmanın hangi koşullarda ve nasıl yapılması gerektiği araştırılmıştır. Dilatometrede R350HT ray çeliği numuneler kullanılarak ilgili ray ve ray kaynak standardların gerektirdiği sertlik değerlerini veren içyapı ve bu içyapıyı elde etmek için gereken ısıl işlem koşulları belirlenmiştir. Ray kaynak bölgelerinin kontrollü hızlandırılmış soğutulmasında kullanılacak aparatın tasarımı bilgisayarda simule edilerek geliştirilmiştir. Özel olarak tasarlanan soğutma aparatı ve sistemi kullanılarak yanmalı alın kaynağı ile birleştirilmiş 60E1 kesitli R350HT rayların kaynak bölgelerine farklı koşullarda hızlandırılmış soğutma uygulanmış ve ilgili EN 14587-2 standardını karşılayan başarılı sonuçlar elde edilmiştir. Mantarı sertleştirilmiş rayların aluminotermit kaynağı ile birleştirilmelerinde ise uygun kaynak porsiyonu kullanımıyla ilgili EN 14730 standardının karşılanabildiği gösterilmiştir.In order to benefit fully from the use of head hardened rails, the weld and the heat affected zones of these rails must have microstructures with mechanical properties similar to those produced by the fine pearlitic microstructures of the rails themselves. For the flash butt welding of head hardened rails, this is only possible through the accelerated controlled cooling of the related zones just after the welding operation. In this study, the required method and the conditions for the controlled accelerated cooling of flash butt welded head hardened R350HT rails have been investigated. Dilatometer experiments were performed on R350HT rail steel samples in order to determine the heat treatment conditions to produce microstructures that would give the hardness values required by the related rail and rail welding standards. A computer simulation study was undertaken to improve the design of the apparatus to be used for the accelerated cooling of the rail welds. A custom accelerated cooling system that employs this specially designed apparatus was used on flash butt welded R350HT rail joints of the 60E1 profile and results satisfying the related EN 14587-2 standard were obtained. For the aluminothermite welding of the head hardened rails, it was shown that the related EN 14730 standard could be met through the use of the proper weld portion
Static and dynamic properties of CN/Cu(001) surfaces and oxidation, dissociation and bimolecular debarboxylation of isocyanate species adsorbed on Cu(001)
No full textThis dissertation presents an outlines my investigations of static and dynamic properties of adsorbed cyanide (CN) and isocyanate (-NCO) species as well as some of their chemistries. Surface bound CN-containing species have not previously been studied extensively, partially due to the inapplicability of fundamental e-beam based surface analysis techniques for investigations. I had the opportunity in my studies to employ multiple surface probing techniques, i.e. HAS, XPS, NEXAFS, TPD and RAIRS, to compile and cross-examine information from CN, –NCO, and derived species, adsorbed on the Cu(001) surface. While angle resolved He atom scattering (HAS) was employed to identify and investigate the ordered superstructure of CN/Cu(001) surfaces, TOF-HAS was employed to investigate its dynamic properties. The CN/Cu(001) surface induced unprecedented simultaneous coherent He diffraction with a large “classical” multiphonon backscattered He intensity. A superstructure is implied that contains both rigidly bound CN species, which maintain the long range c(10x6) translational symmetry, together with bound highly-dynamic CN species that exhibit large thermally induced displacements. The NEXAFS measurements suggest multiple spatial binding configurations for the adsorbed CN moieties. In addition, TPD spectra of C2N2 desorption from CN/Cu(001) surface were analyzed, using my newly developed method, to determine the activation energies for desorption as a function of CN coverage. There are two reactions of NCO species examined in my studies. The first is the newly discovered mutual reaction between NCO species. This type of interaction had not been seen before, as it is essentially difficult to prepare pure NCO/metallic surfaces. Copper was chosen as a substrate as HNCO exposures of Cu(001) at RT, followed by spontaneous H2 desorption, do produce NCO only surfaces. A thermal treatment of the surface, at 573K, leads to a bimolecular decarboxylation of NCO, leaving a carbodimide species (NCN) on the surface. The sp-hybridized linear NCN moieties, which are bound nearly parallel to the substrate, show high thermal stability. The second reaction of NCO, which I have studied, is its oxidation. In particular, the effect of CN coadsorbates on the oxidation of NCO was studied. It was found that the presence of CN catalyzes a dissociation reaction of NCO species on Cu(001).Ph. D.Includes bibliographical referencesby Erkan Ziya Ciftlikl
Effect of size and slenderness on the axial-compressive behavior of basalt FRP-confined predamaged concrete
No full textTo investigate the size and slenderness effect on the axial-compressive behavior of basalt fiber-reinforced polymer (BFRP)-confined predamaged concrete, five groups of concrete cylinders with different sizes and slenderness ratios were designed and tested. The cylinders were axially preloaded to three predamage levels, then repaired using BFRP, and reloaded. The results showed that the concrete predamage had an adverse effect on the ultimate strength and initial elastic modulus of BFRP-confined concrete. Except for the smallest specimens affected by the wall effect, the initial analysis found that the ultimate strength of BFRP-confined concrete decreased with an increase in size and slenderness ratio, and the size and slenderness effect decreased with an increase in BFRP confining pressure, while these increased with the severity of concrete predamage. However, there was no obvious size or slenderness effect on the ultimate strain of BFRP-confined concrete. Through multifactorial analysis, it was confirmed that the ultimate strength of BFRP-confined undamaged and predamaged concrete was influenced by the slenderness. Considering the effect of size, slenderness, and predamage, monotonic and cyclic models were developed for BFRP-confined concrete. Finally, a uniaxial material object was added into OpenSees to provide an effective numerical material model for theoretical analyses and engineering applications. © 2021 American Society of Civil Engineers.The present research was supported by the National Natural Science Foundation of China (Grant No. 51878268) and the Natural Science Foundation of Hunan Province, China (Grant No. 2020JJ4195).
Part of this research was completed by the first author in collaboration with the third and fourth authors during his one-year visit to Ohio State University. The first author acknowledges the State Scholarship Fund of China Scholarship Council (Grant No. 201606135057) for supporting this work and his research visit to the United States
Optimization of Microresistor Beam Performance Using COMSOL Multiphysics and Taguchi Method
No full textMicroresistor beams are crucial components in microelectromechanical systems (MEMS), with broad applications spanning from sensors to microactuators. Their performance is significantly influenced by their design and material properties, thus necessitating an effective optimization strategy. This study proposes a comprehensive approach to the optimization of microresistor beam performance using COMSOL Multiphysics and the Taguchi method. We utilized COMSOL Multiphysics, a powerful finite element analysis tool, to model and simulate the microresistor beam's behavior under a range of conditions. Through COMSOL, we investigated the effects of various design, material and operational parameters, including applied voltage, heat sink temperature and heat transfer coefficient, on beam's performance. The simulations allowed for a nuanced understanding of the complex interplay between these parameters and their impact on the beam's mechanical and electrical characteristics. The Taguchi method, a statistical design of experiments technique, was then employed to optimize these design parameters. By setting up orthogonal arrays, we could systematically explore the design space and identify the optimal combination of parameters that yielded maximum performance and resilience. In addition, the Taguchi method helped in minimizing the undesirable effects of noise factors, enhancing the robustness of the design. The findings of this study highlight the potential of integrating finite element modeling with the statistical design of experiments for the optimization of MEMS components. Moreover, the study offers a replicable and scalable model that can be employed in the optimization of other MEMS components.Although the focus of this study was on microresistor beams, the methodologies and insights gained are applicable to a wide array of microscale devices. Future research could adapt this approach for other MEMS components and explore its potential in different operational environments. In conclusion, this study presents a novel approach to the optimization of microresistor beams, contributing to the growing body of literature on the design and optimization of MEMS. By coupling finite element modeling with the statistical design of experiments, we offer a robust, efficient, and reliable path to the development of high-performance MEMS
Harnessing the Power of Digital Twins for Enhanced Material Behavior Prediction and Manufacturing Process Optimization in Materials Engineering
No full textThe advent of Industry 4.0 and the digital revolution have brought forth innovative technologies such as digital twins, which have the potential to redefine the landscape of materials engineering. Digital twins, virtual representations of physical entities, can model and predict material behavior, enabling enhanced design, testing, and manufacturing of materials. However, the comprehensive utilization of digital twins for predictive analysis and process optimization in materials engineering remains largely uncharted. This research intends to delve into this intriguing intersection, investigating the capabilities of digital twins in predicting material behavior and optimizing manufacturing processes, thereby contributing to the evolution of advanced materials manufacturing. Our study will commence with a detailed exploration of the concept of digital twins and their specific applications in materials engineering, emphasizing their ability to simulate intricate material behaviors and processes in a virtual environment. Subsequently, we will focus on exploiting digital twins for predicting diverse material behaviors such as mechanical properties, failure modes, and phase transformations, demonstrating how digital twins can utilize a combination of historical data, real-time monitoring, and sophisticated algorithms to predict outcomes accurately. Furthermore, we will delve into the role of digital twins in optimizing materials manufacturing processes, including casting, machining, and additive manufacturing, illustrating how digital twins can model these processes, identify potential issues, and suggest optimal parameters. We will present detailed case studies to provide practical insights into the implementation of digital twins in materials engineering, including the advantages and challenges. The final segment of our research will address the current challenges in implementing digital twins, such as data quality, model validation, and computational demands, proposing potential solutions and outlining future directions. This research aims to underline the transformative potential of digital twins in materials engineering, thereby paving the way for more efficient, sustainable, and intelligent material design and manufacturing processes
Applying Deep Learning for Automated Quality Control and Defect Detection in Multi-stage Plastic Extrusion Process
No full textIn the plastics industry, particularly in multistage extrusion processes, maintaining a consistent product quality is paramount. The extrusion process often involves converting granular raw material into a plastic film by heating and stretching it across multiple layers. Two significant aspects of the output product quality are product parameters such as film thickness and stretch, and the presence or absence of defects. Currently, product parameters are efficiently monitored using sensors, but defect identification largely relies on the manual visual inspection by the operator, which may not always occur in real time. This manual approach is prone to errors and can result in delayed defect detection. This study proposes to explore the application of deep learning to automate defect detection in the multi-stage plastic extrusion process. By training deep learning models on a rich dataset of process parameters of the output product, it is possible to enable realtime, automatic identification of defects. This can lead to a substantial improvement in the efficiency and accuracy of the quality control process. Various deep learning architectures will be employed and evaluated for their effectiveness in this task. Furthermore, this study also aims to investigate the correlation between various factors, including equipment performance and quality of incoming raw materials, and the occurrence of defects. Advanced deep learning techniques like Recurrent Neural Networks (RNNs) and Long Short-Term Memory (LSTM) networks will be used to analyze the time-series data from the extrusion process. The findings from this analysis could provide valuable insights into the root causes of defects and guide efforts to minimize their occurrence. In conclusion, this research seeks to leverage the potential of deep learning to enhance the quality control process in the multi-stage plastic extrusion industry, with a focus on automated, real-time defect detection and root cause analysis
Seyahat işletmelerinde bütünleşme ve teknoloji
No full textTez (yüksek lisans) - Anadolu ÜniversitesiAnadolu Üniversitesi, Sosyal Bilimler Enstitüsü, Turizm İşletmeciliği Anabilim DalıKayıt no: 132857Turizm endüstrisi ; konaklama, ulaştırma, yemeÊiçme, rekreasyon, yan hizmet kuruluşları ve seyahat olmak üzere altı sektörü içerir. Tur operatörleri ve seyahat acentaları, seyahat sektörünün önemli kuruluşlarıdır. Geleneksel tur operatörleri, üretici işletmelerin ürünlerini bir araya getirerek paket tur adıyla tüketicilere sunarlar. Seyahat acentaları ise, turizm ürünlerini üreticiler ve toptancılar adına pazarlarlar. Ülkeler ve ülkelerin oluşturduğu birlikler arasında sınırların daralması, bir başka deyişle küreselleşme, diğer sektörleri olduğu gibi seyahat sektörünü de etkiler. Günümüz tur operatörleri, yurtiçinde ve yurtdışında havayolu işletmeleri, otelleri ve seyahat acentaları zincirleri olan bütünleşmiş kuruluşlardır. Seyahat sektörü, farklı ülkelerde ve dağıtım ağının farklı düzeylerinde çalışabilmek için teknolojiye belki de en fazla gereksinim duyan turizm sektörüdür. Türkiye'nin turizmde bir tür çekim ülkesi olması, seyahat işletmelerinin 'coming' ağırlıklı çalışmasına ve bu yönde gelişmesine neden olmaktadır. Ancak, Türk seyahat işletmeleri yurtiçinde ve yurtdışında diğer sektörlerle bütünleşmede ve teknoloji kullanımında yine de başarılı çalışmalar gerçekleştirmektedir
A Comparison of the Ballistic Performances of Various Microstructures in Mil-A Armor Steel
No full textKonca, Erkan/0000-0001-8943-091XDue to their advantageous properties, there is a growing interest in developing armor steels containing fully or partially bainitic microstructures. In this study, bainitic and martensitic microstructures were obtained in rolled homogeneous armor (RHA) steel samples and their ballistic protection performances were investigated. RHA (MIL-A-12560) steel samples were subjected to isothermal heat treatments at three different temperatures, where one temperature (360 degrees C) was above the martensite formation start (Ms) temperature of 336 degrees C while the other two (320 degrees C and 270 degrees C) were below. For the assessment of the ballistic protection performance, the kinetic energy losses of the 12.7 mm bullets fired at the test samples were determined. The promising nature of the bainite microstructure was confirmed as the sample isothermally treated at 360 degrees C provided approximately 10% higher ballistic protection as compared to the regular RHA sample of tempered martensite microstructure. However, the ballistic performances of the isothermally treated samples decreased as the treatment temperature went below the Ms temperature. Following the ballistic tests, hardness measurements, impact tests at -40 degrees C, and macro- and microstructural examinations of the samples were performed. No correlation was found between the hardness and impact energies of the samples and their ballistic performances.ROKETSAN Missile Industries Inc. (Ankara, Turkey)This research was funded by ROKETSAN Missile Industries Inc. (Ankara, Turkey). The APC was paid for by the author
Investigation of the Effects of Austenitizing Temperature on the Austempering Behavior of EN-GJS- 600-3 Spheroidal Graphite Cast Iron
No full textDergiPark: 705209konjesBu çalışmada östenitleme sıcaklığının EN-GJS-600-3 (GGG-60) küresel grafitli dökme demirinöstemperlenme davranışına etkisi araştırılmıştır. Y bloklarına dökülen % 0,5 Cu alaşımlı EN-GJS-600-3küresel grafitli dökme demirden çıkarılan numuneler kullanılarak iki farklı östenitleme sıcaklığı (850 ve950°C) ve iki farklı östemperleme sıcaklığının (290 ve 320°C) dört ayrı kombinasyonunda östemperlemedeneyleri yapılmıştır. Östemperleme deneyleri sonrası numunelerin sertlik ölçümleri, çekme testleri ve içyapı incelemeleri gerçekleştirilmiştir. Her iki östemperleme sıcaklığında da 950°C’de östenitlenmişnumunelerde 850°C’de östenitlenmiş numunelere göre daha yüksek sertlik, akma ve çekme dayanımıdeğerlerine ulaşılmıştır. Bu sonuçlar, 950°C’de yapılan östenitlemenin 850°C’ye göre östenit matris içindehem daha çok karbonun çözünmesini hem de östenitin daha iri taneli olmasını sağlayaraköstemperlenmeye daha elverişli östenit yapısı oluşturabilmesiyle ilişkilendirilmiştir.The effect of austenitizing temperature on the austempering behavior of EN-GJS-600-3(GGG-60) spheroidal graphite cast iron was investigated. 0.5% Cu alloyed EN-GJS-600-3 spheroidalgraphite cast iron samples obtained from Y-blocks were subjected to four different austemperingexperiments as a combination of two different austenitizing (850 and 950°C) and two differentaustempering temperatures (290 and 320°C). Hardness measurements, tensile tests and microstructuralexaminations were performed after the austempering experiments. The samples austenitized at 950°Cproduced higher hardness, yield and tensile strength values as compared to the samples austenitized at850°C. This observation was linked to the fact that as compared to 850°C austenitizing at 950°C providedboth more carbon to dissolve in the austenite matrix and larger austenite grain size resulting in betteraustemperability
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