Mechanical Engineering / Makina Mühendisliği
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Article Citation - WoS: 2Citation - Scopus: 3Design and Manufacturing of a Hip Joint Motion Simulator With a Novel Modular Design Approach(Springer, 2024) Torabnia, S.; Mihçin, D.Ş.; Lazoglu, I.The study is aimed to develop a hip joint wear simulator using a modular design approach to help experimentally monitor and control critical wear parameters to validate in-silico wear models. The proper control and application of wear parameters such as the range of motion, and the applied force values while estimating the lost material due to wear are essential for thorough analysis of wear phenomena for artificial joints. The simulator's dynamics were first modeled, then dynamic loading data was used to calculate the forces, which were further used for topology optimization to reduce the forces acting on each joint. The reduction of the link weights, connected to the actuators, intends to improve the quality of motion transferred to the femoral head. The modular design approach enables topology-optimized geometry, associated gravitational and dynamic forces, resulting in a cost-effective, energy-efficient product. Moreover, this design allows integration of the subject specific data by allowing different boundary conditions following the requirements of industry 5.0. Overall, the in-vitro motion stimulations of the hip-joint prosthesis and the modular design approach used in the study might help improve the accuracy and the effectiveness of wear simulations, which could lead into the development of better and longer-lasting joint prostheses for all. The subject-specific and society-based daily life data implemented as boundary conditions enable inclusion of the personalized effects. Next, with the results of the simulator, CEN Workshop Agreement (CWA) application is intended to cover the personalized effects for previously excluded populations, providing solution to inclusive design for all. © 2023, The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.Article Citation - WoS: 9Citation - Scopus: 11Experimental Investigation of Spray Characteristics of Ethyl Esters in a Constant Volume Chamber(Springer, 2024) Ulu, A.; Yildiz, G.; Özkol, Ü.; Rodriguez, A.D.Abstract: Biodiesels are mainly produced via the utilization of methanol in transesterification, which is the widespread biodiesel production process. The majority of this methanol is currently obtained from fossil resources, i.e. coal and natural gas. However, in contrast with methanol, biomass-based ethanol can also be used to produce biodiesels; this could allow the production line to become fully renewable. This study aimed to investigate the spray characteristics of various ethyl ester type biodiesels derived from sunflower and corn oils in comparison to methyl esters based on the same feedstocks and reference petroleum-based diesel. Spray penetration length (SPL) and spray cone angle (SCA) were experimentally evaluated in a constant volume chamber allowing optical access, under chamber pressures of 0, 5, 10 and 15 bar and injection pressures of 600 and 800 bar. Sauter mean diameter (SMD) values were estimated by using an analytical correlation. Consequently, ethyl esters performed longer SPL (2.8–20%) and narrower SCA (5.1–19%) than diesel under ambient pressures of 5 and 10 bar. Although the SMD values of ethyl esters were 48% higher than diesel on average, their macroscopic spray characteristics were very similar to those of diesel under 15 bar chamber pressure. Moreover, ethyl esters were found to be very similar to methyl esters in terms of spray characteristics. The differences in SPL, SCA and SMD values for both types of biodiesels were lower than 4%. When considering the uncertainty (± 0.84%) and repeatability (±5%) ratios, the difference between the spray characteristics of methyl and ethyl esters was not major. Graphical abstract: [Figure not available: see fulltext.] © 2022, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.Article Gemi Sevk Gücü ve Isı Transferinin Yapısal Gelişim Teorisi ile İlişkisi(TMMOB Gemi Mühendisleri Odası, 2022) Güneş, Ümit; Çetkin, Erdal; Şahin, BahriYapısal Gelişim Teorisi 1996 yılında literatüre kazandırılmış olup tabiattaki ve mühendislikteki tasarım prensiplerini açıklar. Teori, yeryüzündeki akış sistemlerini bütüncül bir şekilde ele alır. Akışın (hareketin) olmadığı yerde çoğu zaman canlılıktan bahsetmemiz dahi mümkün olmamaktadır. Akış sistemlerinin çözümünde anahtar davranış biçimi bu sistemlerin minimum dirençli yol ile hareketini sürdürmesidir. Belli bir zaman dilimi için minimum direnç ile hareket eden sistem zaman geçtikçe kendine yeni yollar (kanallar) bulmakta ya da bazı yolları hiç kullanmayarak yönünü değiştirmektedir. Yapısal Gelişim Teorisi ise hayati öneme sahip olan akış sistemlerinin fiziksel arka planını ortaya koymaktadır. Bu makalede özellikle mühendislik çözümlerinin başında gelen akış sistemlerinin yapısı (gemilerde kurulu ana makine gücü ve ısı transferi örnekleri özelinde) ve Yapısal Gelişim Teorisi’ne göre ilişkisi araştırılmıştır. Bunun için 1085 adet petrol tankeri için DWT ile bu tankerler için gerekli olan güç ilişkisi nonlineer regresyon ile analiz edilmiştir. Sonuç olarak gemilerdeki genel gelişimin ve ısı transferinin yapısal gelişim prensiplerine uygun şekilde gerçekleştiği gösterilmiştir.Article Citation - WoS: 3Boşluk İletim Tabakasız ve Esnek Organo Kurşun İyodür Perovskit Güneş Hücresinin Çevresel Etki Değerlendirmesi(Gazi Üniversitesi, 2022) Sarıaltın, HüseyinPerovskit güneş pilleri (PSC) esneklik ve düşük maliyetli rulodan ruloya üretim gibi avantajlarla birlikte son zamanlarda güç dönüşüm verimliliğinde de önemli bir ilerleme kat etmiştir. PSC'lerin ticarileştirilmesinden önce çevresel performansının yaşam döngüsü değerlendirme (LCA) yöntemi ile araştırılması önemlidir. Bu çalışmada, literatür verilerinden istifade edilerek, esnek Polietilen tereftalat (PET) alt tabaka ve boşluk iletim katmanı (HTL) eliminasyonunu içeren çözelti bazlı organo-kurşun iyodür perovskit güneş hücresinin beşikten kapıya yaşam döngüsü analizi (LCA) gerçekleştirilmiştir. 1 m2 hücre alanı üretiminden kaynaklanan çevresel etkiler altı Uluslararası Referans Yaşam Döngüsü Veri Sistemi (ILCD) kategorisinde belirlenmiştir. Analizin sonucunda, en fazla etki değerinin yüksek elektrik enerjisi tüketimine sahip vakum biriktirme işlemi gereksinimine sahip olan alüminyum metal elektrot tabakasının imalatından kaynaklandığı bulunmuştur. Ticari fotovoltaik teknolojilerle karşılaştırma yapabilmek için en yaygın kullanılan çevresel göstergelerden birisi olan küresel ısınma potansiyeli (GWP), birim kWh elektrik üretimi için hesaplanmıştır. Buna göre, bu çalışmada incelenen HTL'siz esnek (HFF) PSC'nin ticari PV'lerle rekabetçi GWP değerine ulaşmak için 15-20 yıl cihaz ömrüne ihtiyacı olduğu bulunmuştur.Data Paper Citation - WoS: 15Citation - Scopus: 20Database Covering the Prayer Movements Which Were Not Available Previously(Nature Publishing Group, 2023) Mihçin, Şenay; Şahin, Ahmet Mert; Yılmaz, Mehmet; Alpkaya, Alican Tuncay; Tuna, Merve; Akdeniz, Sevinç; Can, Nuray Korkmaz; Tosun, Aliye; Şahin, SerapLower body implants are designed according to the boundary conditions of gait data and tested against. However, due to diversity in cultural backgrounds, religious rituals might cause different ranges of motion and different loading patterns. Especially in the Eastern part of the world, diverse Activities of Daily Living (ADL) consist of salat, yoga rituals, and different style sitting postures. A database covering these diverse activities of the Eastern world is non-existent. This study focuses on data collection protocol and the creation of an online database of previously excluded ADL activities, targeting 200 healthy subjects via Qualisys and IMU motion capture systems, and force plates, from West and Middle East Asian populations with a special focus on the lower body joints. The current version of the database covers 50 volunteers for 13 different activities. The tasks are defined and listed in a table to create a database to search based on age, gender, BMI, type of activity, and motion capture system. The collected data is to be used for designing implants to allow these sorts of activities to be performed.Data Paper Database Covering the Previously Excluded Daily Life Activities(2023) Mihçin, Şenay; Şahin, Ahmet Mert; Yılmaz, Mehmet; Alpkaya, Alican Tuncay; Tuna, Merve; Can, Nuray Korkmaz; Şahin, Serap; Akdeniz, Sevinç; Tosun, AliyeIn biomedical engineering, implants are designed according to the boundary conditions of gait data and tested against. However, due to diversity in cultural backgrounds, religious rituals might cause different ranges of motion and different loading patterns. Especially in the Eastern part of the world, diverse Activities of Daily Living (ADL) consist of salat, yoga rituals, and different style sitting postures. Although databases cover ADL for the Western population, a database covering these diverse activities of the Eastern world, specific to these populations is non-existent. To include previously excluded ADL is a key step in understanding the kinematics and kinetics of these activities. By means of developments in motion capture technologies, excluded ADL data are captured to obtain the coordinate values to calculate the range of motion and the joint reaction forces. This study focuses on data collection protocol and the creation of an online database of previously excluded ADL activities, targeting 200 healthy subjects via Qualisys and IMU motion capture systems, and force plates, from West and Middle East Asian populations. Anthropometrics are known to affect kinematics and kinetics which are also included in the collected data. The current version of the database covers 50 volunteers for 12 different activities, the database aims for 100- male and 100- female healthy volunteers as the final target including C3D and BVH file types. The tasks are defined and listed in a table to create a database to make a query based on age, gender, BMI, type of activity and motion capture system. The data is collected only from a healthy population to understand healthy motion patterns during these previously excluded ADLs. The collected data is to be used for designing implants to allow these sorts of activities to be performed without compromising the quality of life of patients performing these activities in the future.Conference Object A Parametric Numerical Analysis of Laminar Hydrogen Diffusion Flames(International Association for Hydrogen Energy, IAHE, 2022) Korucu, Ayşe; Benim, Ali CemalAtmospheric, laminar, diffusion flames of hydrogen and air are numerically investigated. A detailed hydrogen combustion reaction scheme, in combination with the extended Zeldovich mechanism for the thermal nitrogen oxide formation are used. For comparison purposes, a global mechanism is also applied. The numerical procedure is first validated by comparisons with results of other authors. Subsequently, parametric studies are performed to find optimal solutions with respect to the related to the operation parameters of such flames to achieve minimum low nitrogen oxide emission levels. The question that are addressed include the Reynolds number effect on nitrogen emissions, and the interaction of neighbouring flames, when they are applied in an array. For ensuring an adequately fine resolution of the flame fronts, local adaptive grid refinement techniques are applied to track the flame front. For preliminary results the radiative heat loses has assumed to be insignificant however it should be taken into the account for the further analyses. The maximum temperature is predicted to be ~2040 K which is higher than the reported adiabatic stoichiometric flame temperature, 2023K for the exit velocity of 0.5 m/s. The radial mole fractions of N2 and H2 at the centerline are observed to be 0.66 and 0.41 respectively at the axial distance of 10 mm. Furthermore, the width of the high temperature region of the flame is observed to be ~6.5 mm. © 2022 Proceedings of WHEC 2022 - 23rd World Hydrogen Energy Conference: Bridging Continents by H2. All rights reserved.Research Project Biyobenzetilmis nano yüzey yapıları kullanarak ıslanma ve akış kontrolü(2020) Barışık, MuratProjemizin amacı nano-ölçek yüzey yapılandırmanın yüzey ıslanmasına, akısa ve ısı transferine olan etkilerinin incelenmesidir. Bu nano-ölçek mekanizmaları moleküler dinamik yöntemi ile simüle ettik. Silika-su arasındaki gerekli parametreleri quantum hesapları ile bulduk. Standart yogunluk-fonksiyonları kabüllerinin hesaplayamadıgı fakat dispersive vander- Waals kuvvetlerinin dogru bulunması için gerekli uzun erimli elektron etkilesimlerini DFTD3 grubundan Becke-Johnson modeliyle hesapladık. Devamında silikon yüzeylerin kristal yapısı ve amorf özelliklerine göre ıslanmasındaki degisimini karakterize ettik. Farklı katı yüzey molekül yogunluklarında farklı silikon kristal yapıları seçerken, benzer yüzey molekül yogunlugu aralıgında amorf silikon yapılarını farklı sok sogutmalar yaparak elde ettik. Katı moleküler dizilimlerin ıslanmaya etkisini karakterize ettik. Devamında silika yüzeylerin ıslanmasını inceledik. ?-kristobalit formunun, amorf-silika özelliklerine benzerligi dogrultusunda seçtik. Farklı yüzey yapıları olusturarak ıslanmada olusan degisimi inceledik. Mevcut Cassie-Baxter ve Wenzel ıslatma modellerinin, bu nano-ölçek ıslatma mekanizmalarını tahmin edemedigini gösterdik. Islanma açısının yüzey yapısının geometrik özellikleri ile degisimini karakterize ettik. Devamında yüzey yapılarının neden oldugu çivilenme/takılma etkilerinin literatürde ilk defa detaylı karakterize ettik. Temas çizgisi çıkıntıya takılmıs bir damlacıgın ıslatma açısı damlacık hacminin büyümesi/küçülmesi ile dogrusal oranda artıp/azaldıgını ve bu davranısın boyutlardan ve yüzey ıslatma özelliklerinden bagımsız olarak yüzey yapısının ve damlacıgın büyüklüklerinin oranı cinsinden olustugunu gösterdik. Devamında çalısdıgımız degisik yapılara sahip yüzeylerden nano-kanallar olusturduk. Bu kanallarda basınçla sürülen akısların hız profillerini ve arayüzlerinde olusan kayma hızlarını ölçtük. Yüzey yapılarının ıslanma açısını arttırarak yüzeyi hydrophobik yapmasına ragmen beklenenin aksine kayma hızını azalttıgını bulduk. Mevcut literatürde ıslanma açısının artmasıyla kayma uzunlugu artısını açıklayan modellerin düz olmayan yüzeylerde geçerli olmadıgını gösterdik. Devamında aynı kanal setinde duvardan duvara tek yönde iletim ile ısı transferi çalıstık. Sıcaklık profillerinden arayüz ısıl direnci nedeniyle olusan sıcaklık atlamalarını Kapitza uzunlugu cinsinden ölçtük. Kapitzanın da artan ıslanma açısına karsın azaldıgını gösterdik. Sonuçta ıslanma açısını, kayma hızını ve Kapitza uzunlugunu yüzey yapısının hacmi, yüksekligi ve genisligi cinsinden karakterize ettik. Ihtiyaç duyulan ıslanma, akıs yada ısı transferi yüzey yapılarıyla ayarlanabilir.Article Citation - WoS: 2The Effect of the Temperature of Heat Treatment Process and the Concentration and Duration of Acid Leaching on the Size and Crystallinity of Nano-Silica Powders Formed by the Dissociation of Natural Diatom Frustule(American Scientific Publishers, 2022) Ülker, Sevkan; Güden, MustafaThe present study focused on the processing of nano-silica powders in varying sizes and crystallinities through IP: 846247.10 On: Wed, 14 Dec 2022 07:29:25 heat treatment (900-1200 degrees C), hydrofluoric acid leaching (1-7 N), and ball milling (1 h, 500 rpm) of natural Copyright American Scentfic P blishers diatom frustules. The starting natural frustules were determined to be composed of amorphous silica (88%) Delivered by Ingenta and quartz. The partially ordered crystalline low-quartz and or precursor to low-cristobalite started to form at-900 degrees C. As the heat treatment temperature increased, the crystallinity of the frustules increased from 9.3% at 25 degrees C to 46% at 1200 degrees C. Applying a ball milling reduced the mean particle sizes of the as-received and heat-treated frustules from 15.6-13.7 mu m to 7.2-6.7 mu m, respectively. Acid leaching of the as-received and heat-treated frustules resulted in a further increase in the crystallinity. Furthermore, a ball milling applied after an acid leaching was very effective in reducing the particle size of the as-received and heat-treated frustules. The mean particle size of the acid-leached frustules decreased to 774-547 nm with a crystallinity varying between 12 and 48% after ball milling. A partially dissolved amorphous phase was observed in between crystalline silica grains after acid leaching, which resulted in a rapid fracture/separation of the frustules in ball milling.Article Citation - WoS: 8Citation - Scopus: 9Experimental Investigation of Air Cooling With/Out Tab Cooling in Cell and Module Levels for Thermal Uniformity in Battery Packs(ASME, 2023) Göçmen, Sinan; Çetkin, ErdalCatastrophic effects of global warming and environmental pollution are becoming more evident each day, and reduction in fossil fuel consumption is an urgent need. Thus, electric vehicles powered by sustainable energy sources are becoming a major interest. However, there are some challenges such as safety, limited range, long charging times, and battery life which are inhibitory to the adaptation of them. One of the biggest reasons for these challenges is the relationship between battery degradation and temperature which can be eliminated if batteries can be kept at the optimum temperature range. Here, the effects of three distinct (natural convection, forced convection, and tab cooling) methodology were experimentally compared at both the cell and module levels (six serial 7.5 Ah Kokam pouch cells, 1P6S) for thermal management of lithium-ion cells. The experiments were conducted at a discharge rate of 3C with ambient temperatures of 24 ◦C and 29 ◦C. The cell-level test results show that the tab cooling yields 32.5% better thermal uniformity in comparison to the other techniques. Furthermore, tab cooling yields better temperature uniformity with and without air convection as the hot spots occurring near the tabs is eliminated. For the module level, the forced air convection method stands out as the best option with a 4.3% temperature deviation between cells and maximum cell temperature of 39 ◦C. Overall, the results show that a hybrid approach with tab cooling would be beneficial in terms of temperature homogeneity especially in high capacity electric vehicle battery cells.
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