Mechanical Engineering / Makina Mühendisliği
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Conference Object A Comparative Study of Attention-Augmented YOLO Architectures for Defect Detection in Fused Deposition Modelling(Institute of Electrical and Electronics Engineers Inc., 2025) Cezayirli, H.; Tetik, H.; Dede, M.I.C.; Phone, W.L.; Alkan, B.Additive manufacturing (AM), particularly fused deposition modelling (FDM), facilitates the fabrication of complex geometries with increasing flexibility and efficiency. Ensuring consistent print quality in FDM processes necessitates the development of accurate defect detection mechanisms. Attention-augmented YOLO (You Only Look Once) models have emerged as a promising solution for addressing this challenge. In this study, we systematically benchmark and evaluate the performance of YOLO architectures enhanced with attention mechanisms within the context of FDM 3D printing applications. The models were trained and evaluated using representative defect datasets. The attention-augmented models demonstrate improved detection performance. © 2025 IEEE.Conference Object Redundancy resolution options for the twin-it-romans robotic hybrid manufacturing system(Springer Science and Business Media B.V., 2025) Gündüz, G.M.; Dede, Mehmet İsmet Can; Kiper, Gökhan; Schmitz, M.; Corves, B.The Twinnig Iztech in Robotics Manufacturing System (TWIN-IT-ROMANS) project funded by EU Horizon -Widera-2023-Access-02-01 aims to develop a hybrid manufacturing system that can perform additive and subtractive manufacturing processes and inline quality control using a robotic system. The system will incorporate a 6-degree-of-freedom robot arm and a positioner with 2-degree-of-freedom, which will operate synchronously. This manipulation system is to be designed for performing different manufacturing operations with different degrees-of-freedom requirements. In order to reveal alternative trajectory planning scenarios for this system, this paper presents an initial review of redundancy resolution approaches for kinematically redundant robotic manipulators. First, the four main approaches for redundancy resolution techniques are introduced. Then main studies on energy minimization and stiffness maximization for kinematically redundant robotic manipulators are reviewed. Similar or new approaches are planned to be generated and implemented for the redundant system for hybrid manufacturing. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2025.Conference Object Towards Sustainable Manufacturing: a Review and Future Directions in Additive Manufacturing of Fiber-Reinforced Polymer Composites(Springer Science and Business Media B.V., 2025) Türkcan, M.Y.; Tetik, Halil; Kurt, B.; Dede, Mehmet İsmet Can; Karaş, B.; Tetik, H.; Shokrani, A.; Dede, M.İ.C.The United Nations Sustainable Development Goals (SDGs) provide a global framework for addressing critical challenges such as climate change, resource scarcity and sustainable industrialization. With increasing demand for products and improving quality of life, linear consumption of materials and resources following the “take-make-waste” is no longer possible. As such, innovative solutions are increasingly necessary to enable circular economy in manufacturing. Additive manufacturing (AM) has emerged as a transformative technology in achieving SDGs by enhancing resource efficiency and minimizing waste. Fiber reinforced composites are a promising application of AM, as they offer the potential to optimize material use, reduce labor and support sustainable production practices. However, there is an urgent need for considering circular economy strategies, life cycle assessment (LCA) frameworks and effective recycling at the end of their lifetime. This study examines additive manufacturing systems for fiber-reinforced composites, their environmental impact and exploring the potential contributions of robotic integration in composite manufacturing to enhanced sustainability. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2025.Article Citation - WoS: 1Citation - Scopus: 1Analysis and Comparison of the Projectile Impact Response of an Electron Beam Melt-Ti64 Body Centered Cubic Lattice-Cored Sandwich Plate(Springer, 2025) Erten, H.İ.; Çimen, G.; Yıldıztekin, F.M.; Güden, M.Background: One potential application of additively fabricated lattice structures is in the blade containment rings of gas turbine engines. The blade containment rings are expected to be able to absorb the kinetic energy of a released blade (broken blade) in order to protect the engine parts from damaging. Metallic lattice-cored sandwich plates provide a gap (free space) between two face sheets, which helps to arrest the released blade and increases the energy absorption capability of containment rings. Objective: The objective was to investigate numerically the projectile impact response of Body-Centered-Cubic (BCC) Electron-Beam-Melt (EBM) lattice-cored/Ti64 face sheet sandwich plates as compared with that of an equal-mass monolithic EBM-Ti64 plate. Methods: The projectile impact simulations were implemented in LS-DYNA using the previously determined flow stress and damage models and a spherical steel impactor at the velocities ranging from 150 to 500 m s−1. The experimental projectile impact tests on the monolithic plate were performed at two different impact velocities and the results were used to confirm the validity of the used flow stress and damage models for the monolithic plate models. Results: Lower impact stresses were found numerically in the sandwich plate as compared with the monolithic plate at the same impact velocity. The bending and multi-cracking of the struts over a wide area in the sandwich plate increased the energy absorption and resulted in the arrest of the projectile at relatively high velocities. While monolithic plate exhibited a local bent area, resulting in the development of high tensile stresses and the projectile perforations at lower velocities. Conclusions: The numerical impact stresses in the sandwich plate were distributed over a wider area around the projectile, leading to the fracture and bending of many individual struts which significantly increased the resistance to the perforation. Hence, the investigated lattice cell topology and cell, strut, and face sheet sizes and the lattice-cored sandwich plate was shown potentially more successful in stopping the projectiles than the equal-mass monolithic plates. © The Author(s) 2025.Article Ağır Ticari Araçlarda Kullanılan Bir Volanın Parametrik Optimizasyon Yöntemiyle Tasarımının İyileştirilmesi(2022) Sırmalılar, Mehmet Yalçın; Haktanır, Murat; Saklakoğlu, Nurşen; Eş, CanerOtomotiv endüstrisinde rekabetçi olabilmenin anahtarı ürün geliştirmenin ilk aşamalarında üretim maliyetini ve ürün performansını düşünerek daha iyi yapısal tasarımlar elde etmektir. Son yıllarda sonlu eleman analizindeki gelişmeler daha güvenli ve daha ucuz tasarımların oluşturulmasını sağlamış ve bu yeteneği kazanan firmalar önemli avantajlar elde etmiştir. Bu çalışmada Dönmez Debriyaj firmasında seri üretimi yapılan bir volanın malzeme maliyetini azaltmak üzere boyut optimizasyonu gerçekleştirilmiştir. Bilgisayar destekli sonlu elemanlar yöntemi ile volanın çalışma koşulları simüle edilmiş, parametrik optimizasyon yöntemi ile volan için istenen mekanik özellikleri sağlamanın yanı sıra maliyeti en düşük tutacak şekilde optimizasyon yapılmıştır. Bu çalışma sonunda volan ağırlığı 27,956 kg’dan 26,019 kg’a düşürülerek, toplam volan ağırlığından %6,93 azaltma sağlanmıştır ve ilgili volan, analizlerden elde edilen sonuçlar doğrultusunda talaşlı üretim ile revize edilerek üretilmiş ve araç testine tabi tutulmuştur. Bu test sonucunda hiçbir hasarla karşılaşılmamıştır.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 Citation - WoS: 5Citation - Scopus: 5A Continuously Variable Transmission-Based Variable Stiffness Actuator for Phri: Design Optimization and Performance Verification(American Society of Mechanical Engineers, 2024) Mobedi, Emir; Dede, Mehmet İsmet CanPhysical human–robot interfaces (pHRIs) enabled the robots to work alongside the human workers complying with the regulations set for physical human–robot interaction systems. A variety of actuation systems named variable stiffness/impedance actuators (VSAs) are configured to be used in these systems’ design. Recently, we introduced a new continuously variable transmission (CVT) mechanism as an alternative solution in configuring VSAs for pHRI. The optimization of this CVT has significant importance to enhance its application area and to detect the limitations of the system. Thus, in this paper, we present a design optimization approach (an adjustment strategy) for this system based on the design goals, desired force, and minimization of the size of the system. To implement such design goals, the static force analysis of the CVT is performed and validated. Furthermore, the fabrication of the optimized prototype is presented, and the experimental verification is performed considering the requirements of VSAs: independent position and stiffness variation, and shock absorbing. Finally, the system is calibrated to display 6 N continuous output force throughout its transmission variation range. © 2024 by ASME.Conference Object Citation - Scopus: 3Four-bar function generation using excel solver(Springer, 2023) Söylemez, Eres; Kiper, GökhanThe Chapter presents a simple and efficient way of approximating a function with a four-bar mechanism using four or five design parameters including one or both of the initial crank angles. The method only involves solution of linear set of equations and evaluating determinants, whereas nonlinear equations are numerically solved using a simple program such as Excel. So, the method is easy to explain and can be taught in an undergraduate course along with the wellknown linear three precision point synthesis problem. Precision point synthesis, order synthesis, mixed order synthesis, least squares approximation and extreme point synthesis can all be treated using the same method. The proposed method is illustrated with numerical examples for all mentioned synthesis problems and shown to be quite efficient with very low amount of structural error values.Article Citation - WoS: 18Citation - Scopus: 20Cold Plate Enabling Air and Liquid Cooling Simultaneously: Experimental Study for Battery Pack Thermal Management and Electronic Cooling(Elsevier, 2023) Coşkun, Turgay; Çetkin, ErdalThe temperature of cells varies greatly during dis/charge while their performance and lifetime are greatly affected by this fluctuation. Elevated temperatures may yield battery fire due to thermal runaway as well they accelerate ageing and capacity fade of cells. Thermal management systems are a necessity for electric vehicles to extend the lifetime of battery cells and eliminate any fire risks, especially for fast dis/charging applications. Here, we document a hybrid cold plate with a working fluid(s) of sole air or liquid as well as both of them. Hybridization of air and liquid cooling promises to minimize energy consumption requirements during a charge/ discharge cycle by combining the benefits of both thermal management strategies if energy management is controlled accordingly. The temperature of each cell can be kept below 30 degrees C with the proposed hybrid cooling heat exchanger, and the temperature difference between the cells is reduced by 30 % relative to liquid cooling. The maximum temperatures are decreased by 18 % and 3 % in hybrid cooling when compared to air and water cooling, respectively. Furthermore, a step function combining various discharge rates (1C and 3C) was employed in experiments to mimic a realistic situation, i.e. variable C-rate rather than constant. The results show that the temperature of the battery cells can be kept below 30 degrees C with air cooling for variable discharge rate and the effect of contact resistance should not be overlooked for liquid cooling. Furthermore, the possible use of the proposed hybrid cold plates is surveyed in the cooling of electronic devices which produce more and continuous heat than cells. Therefore, three resistance heaters with a capacity of 50W are used in experiments as well. The results show that the proposed cold plates could be used in both electronics cooling and battery thermal management with a control algorithm to switch between sole working fluid and combination modes which could be developed based on the results of this paper.Article Citation - WoS: 2Citation - Scopus: 3Design and Manufacturing of a Hip Joint Motion Simulator With a Novel Modular Design Approach(Springer, 2023) Torabnia, Shams; Mihçin, Şenay; Lazoğlu, İsmailThe 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.