Mechanical Engineering / Makina Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/4129
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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 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 Citation - WoS: 5Citation - Scopus: 4Design of a Novel Hybrid Cable-Constrained Parallel Leg Mechanism for Biped Walking Machines(Cambridge University Press, 2023) Demirel, M.; Kiper, G.; Carbone, G.; Ceccarelli, M.In this paper, a novel cable-constrained parallel mechanism is presented as a lightweight, low-cost leg mechanism design for walking machines to be used on flat surfaces. The proposed leg mechanism has three translational degrees of freedom. It is based on two specific hybrid kinematic topologies being herewith proposed. The paper reports the kinematic analysis formulation and a position performance evaluation to confirm the main characteristics of the proposed solutions. A 3D CAD model and simulations are carried out to demonstrate the feasibility of the proposed design for performing a human-like gait trajectory. A prototype has been built, and preliminarily tests have been conducted to confirm the motion capabilities of the proposed mechanism design. Then a second, enhanced prototype has been designed and built. An experimental validation is carried out for tracking a planar walking trajectory with the built prototypes by using a real-time PCI controller. Results are presented to validate the operation characteristics of the proposed mechanism and to prove its feasibility for legged walking machines. © The Author(s), 2023.Article An Experimental and Comparative Study of the Self-Loosening of Bolted-Joints Under Cyclic Transverse Loading(Sakarya University, 2021) İnce, U.; Güden, M.The capabilities of analytic models in predicting the experimental critical displacements of the self-loosening of bolted-joints were investigated experimentally and numerically. The experimental loosening rates were determined in a Junker test bench at a constant transverse displacement amplitude (0.45 mm) and under varying initial clamp force and clamp length and controlled bearing and thread friction coefficients. The analytic critical displacements were then calculated using experimental parameters. In addition, a three-dimensional accompanying finite element (FE) model was developed in order to calculate the ratio of spring constants engaging the thread to spring. The results showed relatively low capabilities of present analytic model in the prediction of the critical displacements of the self-loosening of bolted-joints. The efforts to modify the nut reaction moment and the inclination compliance of bolt head portion in the investigated equations however resulted moderate increase in the appropriate predictions. On the other side, the use of the reaction moment determined by FE model increased the appropriate prediction from 58.3 to 73.4%. The accuracy of the equations was further increased by the use of an appropriate kw value, but the increase in this case was only ~4%. © 2021, Sakarya University. All rights reserved.Conference Object Citation - Scopus: 7Design and Fatigue Life Comparison of Steel and Composite Leaf Spring(SAE International, 2012) Soner, M.; Tanoglu, M.; Guven, N.; Karaagac, M.; Akyali, R.; Aksoy, O.; Kanbolat, A.It has been a significant challenge to reduce weights of the vehicles to satisfy the regulations that require development of environmentally-safe vehicles with low CO2 emissions. The conventional leaf springs, designed for the optimized performance together with safety factors, are made of steel. However, it is considered that the steel leaf springs are replaced by lighter ones in order to fulfill the specified requirements. Fiber reinforced composite materials with polymer based matrix offer a great potential for manufacturing leaf springs with lightweight, high mechanical and fatigue performance. Therefore, leaf spring manufacturers have great interest on those materials to replace steel parts with the composite ones and an increasing number of studies have been published in the literature in recent years. In this study, fiber reinforced composite compared with steel leaf springs based on endurance rig tests will be presented. Copyright © 2012 SAE International.Conference Object Citation - Scopus: 69The Arrows Project: Adapting and Developing Robotics Technologies for Underwater Archaeology(IFAC Secretariat, 2015) Allotta, B.; Costanzi, R.; Ridolfi, A.; Colombo, C.; Bellavia, F.; Fanfani, M.; Daviddi, W.ARchaeological RObot systems for the World's Seas (ARROWS) EU Project proposes to adapt and develop low-cost Autonomous Underwater Vehicle (AUV) technologies to significantly reduce the cost of archaeological operations, covering the full extent of archaeological campaign. ARROWS methodology is to identify the archaeologists requirements in all phases of the campaign and to propose related technological solutions. Starting from the necessities identified by archaeological project partners in collaboration with the Archaeology Advisory Group, a board composed of European archaeologists from outside ARROWS, the aim is the development of a heterogeneous team of cooperating AUVs capable of comply with a complete archaeological autonomous mission. Three new different AUVs have been designed in the framework of the project according to the archaeologists' indications: MARTA, characterized by a strong hardware modularity for ease of payload and propulsion systems configuration change; U-C AT, a turtle inspired bio-mimetic robot devoted to shipwreck penetration and A-Size AUV, a vehicle of small dimensions and weight easily deployable even by a single person. These three vehicles will cooperate within the project with AUVs already owned by ARROWS partners exploiting a distributed high-level control software based on the World Model Service (WMS), a storage system for the environment knowledge, updated in real-time through online payload data process, in the form of an ontology. The project includes also the development of a cleaning tool for well-known artifacts maintenance operations. The paper presents the current stage of the project that will lead to overall system final demonstrations, during Summer 2015, in two different scenarios, Sicily (Italy) and Baltic Sea (Estonia). © 2015, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.Article Citation - WoS: 93Citation - Scopus: 6Natural Gas Fueled Compression Ignition Engine Performance and Emissions Maps With Diesel and Rme Pilot Fuels(Elsevier Ltd, 2014) Imran, Shahid Mohammed; Emberson, David Robert; Díez, Alvaro; Wen, Dongsheng; Crookes, Roy James; Korakianitis, Theodosios P.When natural gas is port/manifold injected into a compression ignition engine, the mixture of air and the natural gas is compressed during the compression stroke of the engine. Due to the difference in the values of specific heat capacity ratio between air and natural gas, the temperature and pressure at the time of pilot fuel injection are different when compared to a case where only air is compressed. Also, the presence of natural gas affects the peak in-cylinder (adiabatic flame) temperature. This significantly affects the performance as well as emissions characteristics of natural gas based dual fueling in CI engine. Natural gas has been extensively tested in a single cylinder compression ignition engine to obtain performance and emissions maps.Two pilot fuels, diesel and RME, have been used to pilot natural gas combustion. The performance of the two liquid fuels used as pilots has also been assessed and compared. Tests were conducted at 48 different operating conditions (six different speeds and eight different power output conditions for each speed) for single fueling cases. Both the diesel and RME based single fueling cases were used as baselines to compare the natural gas based dual fueling where data was collected at 36 operating conditions (six different speeds and six different power output conditions for each speed). Performance and emissions characteristics were mapped on speed vs brake power plots. The thermal efficiency values of the natural gas dual fueling were lower when compared to the respective pilot fuel based single fueling apart from the highest powers. The effect of engine speed on volumetric efficiency in case of the natural gas based dual fueling was significantly different from what was observed with the single fueling. Contours of specific NO<inf>X</inf> for diesel and RME based single fueling differ significantly when these fuels were used to pilot natural gas combustion. For both of the single fueling cases, maximum specific NO<inf>X</inf> were centered at the intersection of medium speeds and medium powers and they decrease in all directions from this region of maximum values. On the other hand, an opposite trend was observed with dual fueling cases where minimum specific NO<inf>X</inf> were observed at the center of the map and they increase in all direction from this region of minimum NO<inf>X</inf>. RME piloted specific NO<inf>X</inf> at the highest speeds were the only exception to this trend. Higher specific HC and lower specific CO<inf>2</inf> emissions were observed in case of natural gas based dual fueling. The emissions were measured in g/MJ of engine power. © 2021 Elsevier B.V., All rights reserved.