Akar, Samet
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Doç. Dr.
Email Address
samet.akar@cankaya.edu.tr
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Makine Mühendisliği
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Current Staff
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Scholarly Output
15
Articles
25
Citation Count
89
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0
15 results
Scholarly Output Search Results
Now showing 1 - 10 of 15
Article Citation - WoS: 0Citation - Scopus: 0Selection of Optimum Performance Conditions in the Laser-Assisted Turning of Aisi 4340 Hardened Steel Through the Coupling of Entropy/Mcdm Analysis(Springer Heidelberg, 2024) Akar, Samet; Modanloo, Vahid; Abedini, Vahid; Akar, Samet; Ghadikolaee, Hossein Talebi; Makine MühendisliğiThe laser-assisted turning (LAT) process comprises complicated interactions between cutting process parameters and laser heating. These interactions pose a significant challenge for predicting and optimizing surface integrity, even though it is crucial for the success of the process and its adoption as an alternative industrial process. This research employs multi-criteria decision-making (MCDM) approaches to determine the optimal machining conditions. The entropy method was applied to assign weights to the criteria, and the MOORA and TOPSIS techniques were utilized to rank the alternatives. A combination of various machining parameters, including feed, cutting speed, and depth of cut were assumed to be the alternatives (machining conditions). Moreover, the white layer thickness, microhardness, and surface roughness were considered selection criteria. The results demonstrated that all parameters are effective for surface integrity. On the other hand, the properties of surface integrity were greatly impacted by the laser power and feed. Therefore, the factors that most affected the creation of the white layer were the feed (47.26%) and the laser power (22.10%). The most advantageous process parameters for the LAT of AISI 4340 steel were found to be a cutting speed of 240 m/min, a cutting feed of 0.07 mm/rev, a cutting depth of 0.5 mm, and a laser power of 450 W by the MCDM analysis.Article Citation - Scopus: 1Numerical simulation and experimental investigation: Metal spinning process of stepped thin-walled cylindrical workpiece(Murat Yakar, 2022) Seyedzavvar, M.; Akar, Samet; Seyedzavvar, M.; Akar, S.; Abbasi, H.; 315516; Makine MühendisliğiMany equipment and devices utilized in the aerospace industry are formed as symmetric parts through high plastic deformation of high strength sheet metal alloys with low thickness. Considering the inherent advantages of the spinning process of simple tooling and concentrated deformation loading, this process can be considered as one of the main options in producing these thin-sectioned lightweight parts. In this study, a Finite Element (FE) model has been developed to simulate the formation of a stepped thin-walled cylindrical workpiece of AISI 316 stainless steel alloy by spinning process. The FE simulation results were employed to investigate the effects of process parameters, including feed rate of the roller and rotational velocity of the mandrel on the distribution of stress and strain in the sheet metal, wrinkling failure, and thinning of the sheet metal during deformation. Experiments were carried out using selective input parameters based on the results of FE simulations. The comparison between FE simulations and experiments revealed that the developed model could predict the thinning of the sheet metals with over 93 % accuracy. Additionally, a good agreement between the experimentally deformed sheet configurations with those resulting from finite element simulations has been observed. © Author(s) 2022.Article Citation - WoS: 0Citation - Scopus: 0Prediction of the onset of shear localization based on machine learning(Cambridge Univ Press, 2023) Akar, Samet; Akar, Samet; Ayli, Ece; Ulucak, Oguzhan; Ugurer, Doruk; 315516; 265836; Makine MühendisliğiPredicting the onset of shear localization is among the most challenging problems in machining. This phenomenon affects the process outputs, such as machining forces, surface quality, and machined part tolerances. To predict this phenomenon, analytical, experimental, and numerical methods (especially finite element analysis) are widely used. However, the limitations of each method hinder their industrial applications, demanding a reliable and time-saving approach to predict shear localization onset. Additionally, since this phenomenon largely depends on the type and parameters of the constitutive material model, any change in these parameters requires a new set of simulations, which puts further restrictions on the application of finite element modeling. This study aims to overcome the computational efficiency of the finite element method to predict the onset of shear localization when machining Ti6Al4V using machine learning methods. The obtained results demonstrate that the FCM (fuzzy c-means) clustering ANFIS (adaptive network-based fuzzy inference system) has given better results in both training and testing when it is compared to the ANN (artificial neural network) architecture with an R-2 of 0.9981. Regarding this, the FCM-ANFIS is a good candidate to calculate the critical cutting speed. To the best of the authors' knowledge, this is the first study in the literature that uses a machine learning tool to predict shear localization.Article Citation - WoS: 10Citation - Scopus: 11Molecular dynamic approach to predict thermo-mechanical properties of poly(butylene terephthalate)/CaCO3 nanocomposites(Elsevier, 2021) Seyedzavvar, Mirsadegh; Akar, Samet; Boga, Cem; Akar, Samet; Pashmforoush, Farzad; 315516; Makine MühendisliğiThermo-mechanical properties of poly(butylene terephthalate) polymer reinforced with carbonate calcium nanoparticles have been investigated using molecular dynamics simulations. Detailed analyses have been conducted on the effects of nanofiller content, at concentration levels of 0-7 wt%, on the mechanical properties of PBT, i.e. Young's modulus, Poisson's ratio and shear modulus. Thermal properties, including thermal conductivity and glass transition temperature, have been determined using Perl scripts developed based on nonequilibrium molecular dynamics and a high temperature annealing procedure, respectively. Experiments have been performed to verify the accuracy of the results of MD simulations. The CaCO3/PBT nanocomposites were synthesized using melt blending and mold injection techniques. The uniaxial tensile test, thermal conductivity, differential scanning calorimetry and x-ray diffraction spectroscopy measurements were conducted to quantify the thermo-mechanical properties of such nanocomposites experimentally. The results showed significant improvements in the mechanical properties by addition of CaCO3 nanoparticles due to strong binding between rigid particles and PBT polymer and high nucleation effects of nanoparticles on the matrix. Thermal conductivity and glass transition temperature of nanocomposites represented a consistent increase with the ratio of CaCO3 nanoparticles up to 5 wt% with an enhancement of 38% and 36% with respect to that of pure PBT, respectively.Article Citation - WoS: 0Citation - Scopus: 2Fused filament fabrication in CAD education: A closed-loop approach(Sage Publications inc, 2025) Totuk, Onat Halis; Totuk, Onat Halis; Selvi, Özgün; Selvi, Ozguen; Akar, Samet; Akar, Samet; 315516; Mekatronik Mühendisliği; Makine MühendisliğiIntegrating low-cost fused filament fabrication 3D printing as a foundation for learning 3D modelling is explored. This method blends traditional computer aided design (CAD) instruction with additive manufacturing possibilities. Experimental results demonstrate increased comprehension speed and reduced learning time. This hands-on approach empowers students by enabling direct engagement with the modelling process. Analogous to reverse engineering, the strategy instructs engineering students from final product to model creation, closing the gap between theory and practice. Incorporating 3D printing bridges this divide, enhancing understanding, creativity and problem-solving. The study underscores technology's influence on learning strategies, aligning with the surge of 3D printing in education. Results link advanced design technology usage to improved student performance, with 3D-printed materials yielding 45% higher grades and 30% faster task completion. This study advocates curricular advancement for design-focused careers through enhanced technology integration and favourable 3D printing model reception.Article Citation - Scopus: 4Micro-WEDM of Ni55.8Ti shape memory superalloy: Experimental investigation and optimisation(Inderscience Publishers, 2021) Meshri, H.A.M.; Akar, Samet; Akar, S.; Seyedzavvar, M.; Kiliç, S.E.; 315516; Makine MühendisliğiNickel-titanium superalloy has gained significant acceptance for engineering applications as orthotropic implants, orthodontic devices, automatic actuators, etc. Considering the unique properties of these alloys, such as high hardness, toughness, strain hardening, and development of straininduced martensite, micro-wire electro-discharge machining (μ-WEDM) process has been accepted as one of the main options for cutting intricate shapes of these alloys in micro-scale. This paper presents the results of a comprehensive study to address the material removal rate (MRR) and surface integrity of Ni55.8Ti shape memory superalloy (SMA) in the μ-WEDM process. The effects of discharge current, pulse on-time, pulse off-time, and servo voltage on the performance of this process, including MRR, white layer thickness, surface roughness, and micro-hardness of the machined surface, were investigated by multi-regression analysis using response surface methodology (RSM). The optimisation of input parameters based on the gradient and the swarm optimisation algorithms were also conducted to maximise the MRR and minimise the white layer thickness, surface roughness, and micro-hardness of the machined samples. © 2021 Inderscience Enterprises Ltd.. All rights reserved.Article Citation - WoS: 16Citation - Scopus: 18Investigation of surface integrity in laser-assisted turning of AISI 4340 hardened steel: Finite element simulation with experimental verification(Elsevier Sci Ltd, 2022) Khatir, Farzad Ahmadi; Akar, Samet; Sadeghi, Mohammad Hossein; Akar, Samet; 315516; Makine MühendisliğiThis study investigates the laser-assisted turning (LAT) of AISI 4340 hardened steel (similar to 52 HRC). Despite the various advantages of this process for machining hard materials, the issues related to the machined surface integrity remain the most important challenge. The laser heating used in this process substantially affects the surface integrity characteristics of the workpiece and its mechanical properties. Therefore, it is important to understand, predict, and optimize the workpiece's heat effects at various regions. Due to the complexity of the process, experimental investigations alone cannot reveal thorough information of various phenomena involved. Therefore, a reliable finite element model has been developed to predict the effect of various process input parameters on the metallurgical changes of the machined workpieces. Since general-purpose finite element codes cannot predict the phenomena of interest, three user-defined subroutines have been developed to capture surface integrity parameters such as heat-affected zone, hardness variations of the machined surface, and white layer formation. The developed FE model consists of three parts: mechanical model, thermal model, and coupled thermo-mechanical model. The results of the FE models are verified with experimental data, and a good agreement has been observed. The effect of various process parameters on the surface integrity characteristics of the workpiece has been studied in detail. It has been observed that the laser scanning speed, laser power, and undeformed chip thickness have the most significant influence on the metallurgical effects on the workpiece, respectively.Conference Object Citation - WoS: 9Citation - Scopus: 12Investigation of surface roughness in laser-assisted hard turning of AISI 4340(Elsevier, 2021) Khatir, Farzad Ahmadi; Akar, Samet; Sadeghi, Mohammad Hossein; Akar, Samet; 315516; Makine MühendisliğiIn recent years, new materials such as titanium, nickel alloys, and high-strength steels have been widely used in medical, nuclear, and other industries. Since the manufacturing of different components from these materials has always been associated with the machining process, the use of hard machining in their production is unavoidable. The short life of the cutting tool, the poor quality of the machined surfaces, and the long machining time are some of the challenging issues involved in the traditional machining of these materials. Therefore, researchers have investigated new machining techniques to increase the efficiency and quality of produced parts. Thermal-assisted machining, especially laser-assisted machining is one of the promising methods of machining difficult-to-machine materials. However, this process faces some challenges in terms of the achievable surface integrity of the machined surfaces. This research studies the effect of cutting and thermal parameters on the surface roughness in the laser-assisted turning (LAT) process of AISI 4340 hard steel with a hardness of 560 HV. The results illustrated that by selecting a proper combination of process parameters, the damage caused by the heat penetration into the workpiece can be minimized and the advantages of LAT can be benefited from. (C) 2020 The Authors. Published by Elsevier Ltd.Article Molecular dynamic approach to predict thermo-mechanical properties of poly(butylene terephthalate)/CaCO3 nanocomposites(2021) Akar, Samet; Boğa, Cem; Akar, Samet; Pashmforoush, Farzad; 315516; Makine MühendisliğiThermo-mechanical properties of poly(butylene terephthalate) polymer reinforced with carbonate calcium nanoparticles have been investigated using molecular dynamics simulations. Detailed analyses have been conducted on the effects of nanofiller content, at concentration levels of 0–7 wt%, on the mechanical properties of PBT, i.e. Young's modulus, Poisson's ratio and shear modulus. Thermal properties, including thermal conductivity and glass transition temperature, have been determined using Perl scripts developed based on nonequilibrium molecular dynamics and a high temperature annealing procedure, respectively. Experiments have been performed to verify the accuracy of the results of MD simulations. The CaCO3/PBT nanocomposites were synthesized using melt blending and mold injection techniques. The uniaxial tensile test, thermal conductivity, differential scanning calorimetry and x-ray diffraction spectroscopy measurements were conducted to quantify the thermo-mechanical properties of such nanocomposites experimentally. The results showed significant improvements in the mechanical properties by addition of CaCO3 nanoparticles due to strong binding between rigid particles and PBT polymer and high nucleation effects of nanoparticles on the matrix. Thermal conductivity and glass transition temperature of nanocomposites represented a consistent increase with the ratio of CaCO3 nanoparticles up to 5 wt% with an enhancement of 38% and 36% with respect to that of pure PBT, respectively. © 2021 Elsevier LtdArticle Citation - WoS: 5Citation - Scopus: 7Combined use of ultrasonic-assisted drilling and minimum quantity lubrication for drilling of NiTi shape memory alloy(Taylor & Francis inc, 2023) Akar, Samet; Lotfi, Bahram; Kilic, S. Engin; Yilmaz, Okan Deniz; Akar, Samet; 315516; Makine MühendisliğiThe drilling of shape-memory alloys based on nickel-titanium (Nitinol) is challenging due to their unique properties, such as high strength, high hardness and strong work hardening, which results in excessive tool wear and damage to the material. In this study, an attempt has been made to characterize the drillability of Nitinol by investigating the process/cooling interaction. Four different combinations of process/cooling have been studied as conventional drilling with flood cooling (CD-Wet) and with minimum quantity lubrication (CD-MQL), ultrasonic-assisted drilling with flood cooling (UAD-Wet) and with MQL (UAD-MQL). The drill bit wear, drilling forces, chip morphology and drilled hole quality are used as the performance measures. The results show that UAD conditions result in lower feed forces than CD conditions, with a 31.2% reduction in wet and a 15.3% reduction in MQL on average. The lowest feed forces are observed in UAD-Wet conditions due to better coolant penetration in the cutting zone. The UAD-Wet yielded the lowest tool wear, while CD-MQL exhibited the most severe. UAD demonstrated a & SIM;50% lower tool wear in the wet condition than CD and a 38.7% in the MQL condition. UAD is shown to outperform the CD process in terms of drilled-hole accuracy.
