Makine Mühendisliği Bölümü

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Citation Count: Akar, Samet; Seyedzavvar, Mirsadegh; Boğa, Cem. (2023)." A study on the μwire-EDM of Ni55.8Ti shape memory superalloy: an experimental investigation and a hybrid ANN/PSO approach for optimization", Journal Of The Brazilian Society Of Mechanical Sciences And Engineering, Vol.45, No.3.
A study on the μwire-EDM of Ni55.8Ti shape memory superalloy: an experimental investigation and a hybrid ANN/PSO approach for optimization
(2023) Akar, Samet; Seyedzavvar, Mirsadegh; Boğa, Cem; 315516
The unique properties of high hardness, toughness, strain hardening, and development of strain-induced martensite of nickel-titanium superalloys made the micro-wire electro discharge machining (mu wire-EDM) process one of the main practical options to cut such alloys in micro-scale. This paper presents the results of a comprehensive study to address the response variables of Ni55.8Ti superalloy in mu wire-EDM process, including the kerf width (KW), material removal rate (MRR), arithmetic mean surface roughness (R-a) and white layer thickness (WLT). To this aim, the effects of pulse on-time (T-on), pulse off-time (T-off), discharge current (I-d) and servo voltage (SV) as input parameters were investigated using the experiments conducted based on Taguchi L-27 orthogonal array. The results were employed in the analysis of variance (ANOVA) to examine the significance of input parameters and their interactions with the output variables. An optimization approach was adopted based on a hybrid neural network/particle swarm optimization (ANN/PSO) technique. The ANN was employed to achieve the models representing the correlation between the input parameters and output variables of the mu wire-EDM process. The weight and bias factor matrices were obtained by ANN in MATLAB and together with the feed forward/backpropagation model and developed functions based on PSO methodology were used to optimize the input parameters to achieve the minimum quantities of KW, R-a and WLT and the maximum value of MRR, individually and in an accumulative approach. The results represented a maximum accumulative error of nearly 8% that indicated the precision of the developed model and the reliability of the optimization approach. At the optimized level of input parameters obtained through the accumulative optimization approach, the KW, R-a, and WLT remained nearly intact as compared with the levels of responses obtained in the individual optimization approach, while there was a sacrifice in the machining efficiency and reduction in the MRR in the mu wire-EDM process of Nitinol superalloy.
Citation Count: Namlu, Ramazan Hakkı...et.al. (2023). "Combined use of ultrasonic-assisted drilling and minimum quantity lubrication for drilling of NiTi shape memory alloy", Machining Science and Technology, Vol.27, No.4, pp.325-349.
Combined use of ultrasonic-assisted drilling and minimum quantity lubrication for drilling of NiTi shape memory alloy
(2023) Namlu, Ramazan Hakkı; Lotfi, Bahram; Kılıç, S. Engin; Yılmaz, Okan Deniz; Akat, Samet; 315516
The 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 ∼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.
Citation Count: Perveen, Asma; Akar, Samet. Electrochemical discharge machining: trends and development, in Micro Electro-Fabrication, pp. 317-338, 2021.
Electrochemical discharge machining: trends and development
(2021) Perveen, Asma; Akar, Samet; 315516
The fabrication of microscale products revolutionizes the way manufacturing industries work today and has become the demand of current era due to their applications in various fields like microfluidics, biomedical testing systems, and microelectromechanical systems. Current research interest of manufacturing industries has shifted toward micromanufacturing process development. Electrochemical discharge machining (ECDM) is one of such recently developed process well known for its capability to machine both conductive as well as nonconductive materials. This process evolved from combination of electrodischarge machining and electrochemical machining. This hybrid machining process becomes an attractive technology due to its process simplicity and application in fabrication of microscale features and three-dimensional structures. This chapter will be focusing on the state-of-the-art review of the ECDM processes and its recent development. Various form of this process such as ECDM turning, ECMD-milling, and ECDM grinding will be presented in this chapter. Based on the research found in the literature, limitation associated with ECDM process will be demonstrated, and future research trend for overcoming these drawbacks will be narrated.
Citation Count: Emami, Mohsen...et al. (2023). "Experimental investigation into the effect of magnetorheological fluid damper on vibration and chatter in straight turning process", Journal of Manufacturing Processes, Vol.99, pp.825-847.
Experimental investigation into the effect of magnetorheological fluid damper on vibration and chatter in straight turning process
(2023) Emami, Mohsen; Nasab, Vahid Hasan; Akar, Samet; Batako, Andre; 315516
Magneto-Rheological (MR) dampers have received a great deal of attention in recent years due to the potential of offering semi-active control. MR dampers have been successfully applied in the vibration control of several machining processes. However, the effect of the material of the damper's fluid chamber on its magnetic properties has not been studied much. In this study, an MR damper has been designed to control the chatter vibration of the straight turning operation. The magnetic properties of the MR damper are simulated in the FEM software COMSOL Multiphysics with two types of steel AISI 410 and AISI 1018, and the material with the best performance for constructing the fluid chamber is determined. Then, the MR damper with an assembly to hold the cutting tool was fabricated and experimentally tested during straight turning operation and its effect on the tool vibration, and work surface roughness was analyzed. From the result, it was observed that the MR damper reduced tool vibration and chatter effectively. The results obtained in this research confirm that the application of the MR damper in the straight-turning process can either suppress the chatter or greatly reduce the frequency amplitude of the chatter. The reduction of the tool's acceleration amplitude with the MR damper was more intense in the condition of chatter suppression and reached up to 89.42 %. Moreover, the MR damper reduced the roughness of the machining surface. This reduction was higher in cases where the chatter was suppressed and it was observed up to 29 %.
Citation Count: Totuk, Onat Halis; Selvi, Özgün; Akar, Samet (2023). "Fused filament fabrication in CAD education: A closed-loop approach", International Journal of Mechanical Engineering Education.
Fused filament fabrication in CAD education: A closed-loop approach
(2023) Totuk, Onat Halis; Selvi, Özgün; Akar, Samet; 315516
Integrating 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.
Citation Count: Khatir, Farzad Ahmadi; Sadeghi, Mohammad Hossein; Akar, Samet (2022). "Investigation of surface integrity in laser-assisted turning of AISI 4340 hardened steel: Finite element simulation with experimental verification", Optics and Laser Technology, Vol. 147.
Investigation of surface integrity in laser-assisted turning of AISI 4340 hardened steel: Finite element simulation with experimental verification
(2022) Khatir, Farzad Ahmadi; Sadeghi, Mohammad Hossein; Akar, Samet; 315516
This study investigates the laser-assisted turning (LAT) of AISI 4340 hardened steel (∼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. © 2021
Citation Count: Khatir, Farzad Ahmadi; Sadeghi, Mohammad Hossein; Akar, Samet (2021). "Investigation of surface integrity in the laser-assisted turning of AISI 4340 hardened steel", Journal of Manufacturing Processes, Vol. 61, pp. 173-189.
Investigation of surface integrity in the laser-assisted turning of AISI 4340 hardened steel
(2021) Khatir, Farzad Ahmadi; Sadeghi, Mohammad Hossein; Akar, Samet; 315516
The use of laser-assisted turning (LAT) can improve different aspects of the machinability of high hardness/strength materials. The heat applied in this process reduces the strength of the material and upon a proper selection of laser heat source and machining process parameters, a significant improvement in the machining process can be achieved. This research studies the effect of machining and laser heat source parameters on the surface integrity of the LAT process of AISI 4340 hardened steel with a hardness of 560 HV using Response Surface Methodology (RSM). The effect of machining process parameters (feed rate, depth of cut and cutting speed) and laser power on the surface integrity characteristics of the machined surfaces (white layer thickness, microhardness, surface roughness, and surface chemical composition) are investigated. A detailed finite element simulation of the process has been performed to better understand the physics of the process and to interpret the experimental results. Laser power and feed rate are shown to be the most significant parameters affecting the surface integrity of the machined surfaces. It has been shown that a proper selection of machining and laser heat source parameters makes it possible to minimize the adverse effect of laser heating in the LAT process. This can pave the way for the widespread application of the LAT process by eliminating one of the most important obstacles of this process by controlling the laser heat diffusion into the workpiece. © 2020
Citation Count: Ahmadi Khatir, Farzad; Hossein Sadeghi, Mohammad; Akar, Samet (2020). "Investigation of surface roughness in laser-assisted hard turning of AISI 4340", 1st International Conference and Exposition on Mechanical, Material and Manufacturing Technology, ICE3MT 2020, Materials Today: Proceeding, Vol. 38, pp. 3085-3090.
Investigation of surface roughness in laser-assisted hard turning of AISI 4340
(2020) Ahmadi Khatir, Farzad; Hossein Sadeghi, Mohammad; Akar, Samet; 315516
In 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. © 2020 Elsevier Ltd. All rights reserved.
Citation Count: Meshri, Hassan Ali M...et al (2021). "Micro-WEDM of Ni55.8Ti shape memory superalloy: Experimental investigation and optimisation", International Journal of Mechatronics and Manufacturing Systems, Vol. 14, No. 1, pp. 18-38.
Micro-WEDM of Ni55.8Ti shape memory superalloy: Experimental investigation and optimisation
(2021) Meshri, Hassan Ali M.; Akar, Samet; Seyedzavvar, Mirsadegh; Kılıç, Sadık Engin; 315516
Nickel-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.
Citation Count: Nasseri, Behzad; Akar, Samer; Naseri, Erdinç. "Microchannels for microfluidic systems", in Biomedical Applications of Microfluidic Devices, Academic Press, 2021, pp. 37-75.
Microchannels for microfluidic systems
(Academic Press, 2021) Nasseri, Behzad; Akar, Samer; Naseri, Erdinç; 315516
Microfluidic systems (which are also known as microchannel devices) are an important and versatile practical apparatus applicable in different areas of science and technology. The appropriate design of microfluidic system demands the accurate calculation of the parameters of the microfluidic device. The channels used in microfluidic systems are critical compartments of the device, which affect the efficiency of the system. The purpose of this chapter is to survey the microchannels and their characteristics in microfluidic systems. After a detailed discussion of microchannels, their applications for non-living phantoms for cardiovascular, neuroscience and respiratory studies will be discussed. In the biomedical applications of microchannels the areas such as cell studies e.g. cytoskeleton behavior, cell-to-cell interaction detecting of cell derived moieties are important. Also cellular level tissue engineering, such as cell vaso-occlusion in tissue biomimicking is described.
Citation Count: Seyedzavvar, Mirsadegh...et al (2021). "Molecular dynamic approach to predict thermo-mechanical properties of poly(butylene terephthalate)/CaCO3 nanocomposites", Materials Today Communications, Vol. 28.
Molecular dynamic approach to predict thermo-mechanical properties of poly(butylene terephthalate)/CaCO3 nanocomposites
(2021) Seyedzavvar, Mirsadegh; Boğa, Cem; Akar, Samet; Pashmforoush, Farzad; 315516
Thermo-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 Ltd
Citation Count: Seyedzavvar, Mirsadegh;...et.al. (2021). "Molecular dynamic approach to predict thermo-mechanical properties of poly(butylene terephthalate)/CaCO3 nanocomposites", Materials Today Communications, vol.28.
Molecular dynamic approach to predict thermo-mechanical properties of poly(butylene terephthalate)/CaCO3 nanocomposites
(2021) Seyedzavvar, Mirsadegh; Boğa, Cem; Akar, Samet; Pashmforoush, Farzad; 315516
Thermo-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.
Citation Count: Seyedzavvar, Mirsadegh;...et.al. (2022). "Numerical simulation and experimental investigation: Metal spinning process of stepped thin-walled cylindrical workpiece", Turkish Journal of Engineering, Vol.6, No.1, pp.67-80.
Numerical simulation and experimental investigation: Metal spinning process of stepped thin-walled cylindrical workpiece
(2022) Seyedzavvar, Mirsadegh; Seyedzavvar, Mirali; Akar, Samet; Abbasi, Hossein; 315516
Many 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.
Citation Count: Akar,S.;...et.al. (2023). "Prediction of the onset of shear localization based on machine learning", Artificial Intelligence for Engineering Design, Analysis and Manufacturing: AIEDAM, Vol.37.
Prediction of the onset of shear localization based on machine learning
(2023) Akar, Samet; Aylı, Ece; Ulucak, Oğuzhan; Uğurer, Doruk; 315516; 265836
Predicting 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 R2 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.
Citation Count: Ilkhchi, Reza Najati...et al (2021). "Prediction of white layer formation in μ-WEDM process of NiTi shape memory superalloy: FEM with experimental verification", International Journal of Advanced Manufacturing Technology, Vol. 113, No. 9-10, pp. 2805-2817.
Prediction of white layer formation in μ-WEDM process of NiTi shape memory superalloy: FEM with experimental verification
(2021) Ilkhchi, Reza Najati; Akar, Samet; Meshri, Hassan Ali M.; Seyedzavvar, Mirsadegh; 315516
Microscopic changes in the surface of nickel-titanium (nitinol) shape memory alloys (SMAs) in micro-wire electro-discharge machining (μ-WEDM) due to the formation of a resolidified layer on the machined surface, called white layer, are one of the main drawbacks in the processing of such alloys. Since these changes significantly affect the shape memory and elastic recovery characteristics of these alloys, reduction of the white layer thickness (WLT) based on the selection of optimum process parameters is essential to raise the quality of the machined parts. In this regard, a finite element model (FEM) has been developed to simulate the effects of μ-WEDM process parameters, including discharge current, pulse on-time, pulse off-time, and servo voltage, on the heat distributing in Ni55.8Ti SMA to predict the WLT. The flushing efficiency of electric discharges and the effect of flow regime of the dielectric fluid on the heat distribution in the workpiece and the formation of the WLT are analyzed. Experimental data are used to verify the accuracy of the FEM. The results show that the developed model can predict the WLT in μ-WEDM process of Ni55.8Ti SMA with an average error of 14%. The effects of discharge parameters on the formation of the WLT are discussed in details based on the results of the FEM.

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