Makine Mühendisliği Bölümü Yayın Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/263

Browse

Now showing 1 - 20 of 23

Citation - WoS: 7
Citation - Scopus: 10
Combined Use of Ultrasonic-Assisted Drilling and Minimum Quantity Lubrication for Drilling of Niti Shape Memory Alloy
(Taylor & Francis inc, 2023) Namlu, Ramazan Hakki; Lotfi, Bahram; Kilic, S. Engin; Yilmaz, Okan Deniz; Akar, Samet
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 & 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.
Citation - WoS: 5
Citation - Scopus: 6
Comparison of Different Yield Criteria in Various Deep Drawn Cups
(Springer France, 2017) Darendeliler, Haluk; Cogun, Ferah
The aim of the study is to evaluate the performance of three recent yield criteria namely; BBC2008-8p, Yld2003-8p, Hu2003 through the simulation of the hemispherical, cylindrical and square cup drawing processes by comparing the results with the ones obtained by using the von Mises criterion for the isotropic, kinematic and combined hardening and the Hill'48 criterion. For this purpose, two different sheet materials, SS304 stainless steel and DKP6112 steel, and various punch travels were used in the simulations and experimental phases of this study. The BBC2008-8p, Yld2003-8p and Hu2003 models were implemented to the ABAQUS software through the user material subroutine VUMAT. The thickness strain distributions obtained from the simulations were compared with the experimental results to analyze the validity of the three aforementioned criteria. Compared with the other models, the material behavior in deep drawing cases of this study is better predicted with more recent models, namely BBC2008-8p, Yld2003-8p and Hu2003, which include anisotropy parameters found from uniaxial and biaxial tension tests.
Citation - WoS: 16
Citation - Scopus: 17
Effects of Electrolytic Copper and Copper Alloy Electrodes on Machining Performance in Electrical Discharge Machining (Edm)
(Taylor & Francis inc, 2022) Esen, Ziya; Simsek, Ulke; Cogun, Can
The most important cost element of electric discharge machining (EDM) is the production of tool electrode (shortly electrode). In the EDM process, copper and its alloys are often used as electrode materials. The machining with EDM without increasing the costs can be achieved by selecting the proper electrode with low production and material costs as well as high workpiece material removal rate (MRR), low electrode wear rate (EWR), and relative wear (RW = MRR/EWR). In this study, the EDM performance outputs, namely, MRR and RW were experimentally investigated for electrolytic copper, CuCr1Zr (with and without aging treatment) and CuCo2Be alloy electrode materials for varying machining parameters. The performance outputs were affected by the electrode material and the applied aging treatment. The aged CuCr1Zr alloy electrodes had higher electrical conductivity and better machining performance than the as-received alloy. The CuCo2Be alloy electrodes exhibited moderate to high MRR; however, their RW was the highest. Although the electrolytic copper has moderate MRR performance compared to the investigated alloys, its low cost increased its performance index, making it a more suitable electrode material for EDM applications.
Citation - WoS: 16
Citation - Scopus: 18
Electrostatic Energy Harvesting by Droplet-Based Multi-Phase Microfluidics
(Springer Heidelberg, 2012) Kulah, Haluk; Yildirim, Ender
This paper presents an energy scavenging technique, merging microfluidics with electrostatic energy harvesting. The method employs droplet-based microflow of two phases with different electrical permittivities, resulting in a capacitance change across the microchannel, to harvest electrical energy. The technique is implemented on 3 mm wide, 1 mm deep minichannels. It is shown that 0.4 nW can be harvested using a single electrode pair, with air and water as the two phases flowing at 1 ml/min. The generated power can be increased significantly by microscale implementation, where the number of electrodes can also be increased for further improvement.
Citation - WoS: 3
Citation - Scopus: 3
Experimental and Numerical Investigation of Comparability of Whiplash Sled Test Results
(Springer Heidelberg, 2016) Ider, Sitki Kemal; Gokler, Mustafa Ilhan; Ozdemir, Mustafa
Whiplash-associated neck injuries represent an important health and socioeconomic problem attracting more and more attention of the vehicle safety community. Sled tests are conducted for the dynamic whiplash assessment of seats. However, reproducibility of the initial backset distances and of the sled pulses in every test plays an important role on the comparability of these results. In this study, in order to investigate these aspects, three different driver seat types are considered with three identical and unused samples for each of them, and by strictly following the European New Car Assessment Program (Euro NCAP) whiplash protocol and using the BioRID II dummy, totally nine sled tests are performed. The sled pulses are in general reproduced quite well for different vehicle seats in these tests. However, it is seen that there are differences of up to 5 mm in the initial backset distances recorded for the identical seats of the same type, while this difference increases up to 7 mm among the different seat types considered. Moreover, taking into account the associated tolerances allowed in this protocol, this uncertainty in the backset can even increase up to 10 mm. Based on the previous simulation results obtained by using the finite element model of the BioRID II dummy, linear regression models are constructed, and it is shown that a 10-mm increase in the backset will yield an increase of 2.25, 2.89 and 3.11 m(2)/s(2) in the NICmax values for the low, medium and high severity Euro NCAP pulses, respectively. Being 38, 22 and 31 % of the differences between the associated Euro NCAP higher and lower performance limits, and 68, 96 and 124 % of the differences between the associated Euro NCAP lower performance and capping limits, such increases in the NICmax values are found to bring an unacceptably high uncertainty in the test results, and they can even easily lead to the application of capping, which means giving a zero score for the entire test. In light of these findings, several suggestions are recommended for a more solid whiplash dynamic assessment procedure.
Citation - WoS: 3
Citation - Scopus: 3
Experimental Investigation of Laminar Heat Transfer Inside Trapezoidal Duct Having Different Corner Angles
(Taylor & Francis inc, 2015) Arslan, K.; Onur, N.
In this study, steady-state laminar forced flow and heat transfer in a horizontal smooth trapezoidal duct having different corner angles were experimentally investigated in the Reynolds number range from 10(2) to 10(3). Flow is hydrodynamically fully developed and thermally developing under a uniform surface temperature condition. Based on the present experimental data of laminar flow in the thermal entrance region, new engineering correlations were presented for the heat transfer and friction coefficients for each corner angle. The results have shown that as the Reynolds number increases heat transfer coefficient increases but Darcy friction factor decreases. Also, it is observed that average Nusselt number increases while average Darcy friction factor decreases with increasing corner angle of the duct.
Citation - WoS: 7
Citation - Scopus: 9
An Experimental Work on Using Conductive Powder-Filled Polymer Composite Cast Material as Tool Electrode in Edm
(Springer London Ltd, 2014) Cogun, Can; Yaman, Kemal
This paper introduces the composite tool electrodes made of electrical conductive powder-filled polyester resin matrix material, providing promise for the electrical discharge machining (EDM) process. The dendrite-shaped copper powder, graphite powder, and their mixture were used as conductive fillers. Six different types of composite electrodes, namely, plain copper-polyester, pressed copper-polyester, furnaced copper-polyester, plain copper-graphite-polyester, pressed copper-graphite-polyester, and furnaced copper-graphite-polyester were prepared. It is found experimentally that increasing v (f) improved workpiece material removal rate, tool wear rate, relative wear, and electrical conductivity of electrodes. The pressed copper-polyester electrodes were found to be promising in the ED finishing of workpieces at low machining current settings. The practical applicability of the proposed composite electrodes in the industry was also illustrated.
Citation - WoS: 2
Citation - Scopus: 1
Exploring the Potential of Artificial Intelligence Tools in Enhancing the Performance of an Inline Pipe Turbine
(Sage Publications Ltd, 2024) Celebioglu, Kutay; Ayli, Ece; Cetinturk, Huseyin; Tascioglu, Yigit; Aradag, Selin
In this study, investigations were conducted using computational fluid dynamics (CFD) to assess the applicability of a Francis-type water turbine within a pipe. The objective of the study is to determine the feasibility of implementing a turbine within a pipe and enhance its performance values within the operating range. The turbine within the pipe occupies significantly less space in hydroelectric power plants since a spiral casing is not used to distribute the flow to stationary vanes. Consequently, production and assembly costs can be reduced. Hence, there is a broad scope for application, particularly in small and medium-scale hydroelectric power plants. According to the results, the efficiency value increases on average by approximately 1.5% compared to conventional design, and it operates with higher efficiencies over a wider flow rate range. In the second part of the study, machine learning was employed for the efficiency prediction of an inline-type turbine. An appropriate Artificial Neural Network (ANN) architecture was initially obtained, with the Bayesian Regularization training algorithm proving to be the best approach for this type of problem. When the suitable ANN architecture was utilized, the prediction was found to be in good agreement with CFD, with an root mean squared error value of 0.194. An R2 value of 0.99631 was achieved with the appropriate ANN architecture.
Citation - WoS: 2
Citation - Scopus: 2
Hybrid Force and Motion Control of a Three-Dimensional Flexible Robot Considering Measurement Noises
(Mdpi, 2022) Kilicaslan, Sinan; Ozgoren, Mustafa Kemal; Ider, Sitki Kemal
This work addresses the end-effector trajectory-tracking force and motion control of a three-dimensional three-link robot considering measurement noises. The last two links of the manipulator are considered as structurally flexible. An absolute coordinate approach is used while obtaining the dynamic equations to avoid complex dynamic equations. In this approach, each link is modeled as if there is no connection between the links. Then, joint connections are expressed as constraint equations. After that, these constraint equations are used in dynamic equations to decrease the number of equations. Then, the resulting dynamic equations are transformed into a form which is suitable for controller design. Furthermore, the dynamic equations are divided as pseudostatic equilibrium and deviation equations. The control torques resulting from the pseudostatic equilibrium and the elastic deflections are obtained easily as the solution of algebraic equations. On the other hand, the control torques corresponding to the deviations are obtained without any linearization. Encoders, strain gauges, position sensors and force and moment sensors are required for measurements. Low pass filters are considered for the sensors. For the crossover frequencies of the sensors, low and high values are chosen to observe the filtering effect on the robot output.
Citation - WoS: 30
Citation - Scopus: 32
Investigation on Replication of Microfluidic Channels by Hot Embossing
(Taylor & Francis inc, 2017) Arikan, M. A. Sahir; Cogun, Ferah; Yildirim, Ender
In this study, effects of embossing temperature, time, and force on production of a microfluidic device were investigated. Polymethyl methacrylate (PMMA) substrates were hot embossed by using a micromilled aluminum mold. The process parameters were altered to observe the variation of replication rate in width and depth as well as symmetry of the replicated microfluidic channels. Analysis of variance (ANOVA) on the experimental results indicated that embossing temperature was the most important process parameter, whereas embossing time and force have less impact. One distinguishing aspect of this study is that, the channels were observed to be skewed to either side of the channel depending on the location of the protrusions on the mold. The mechanism of the skewness was investigated by finite element analysis and discussed in detail. Results showed that the skewness depends on the flow characteristics of the material and could be reduced by increasing the embossing temperature. The best replication rates were obtained at parameter settings of 115 degrees C, 10kN, and 8min for the molds with minimum 56 mu m wide features of 120 mu m depth. We also showed that the fabricated channels could be successfully sealed by solvent-assisted thermo-compressive bonding at 85 degrees C under 5.5kN force.
Citation - WoS: 6
Citation - Scopus: 6
Machine Learning Based Developing Flow Control Technique Over Circular Cylinders
(Asme, 2023) Turkoglu, Hasmet; Ayli, Ece; Kocak, Eyup
This paper demonstrates the feasibility of blowing and suction for flow control based on the computational fluid dynamics (CFD) simulations at a low Reynolds number flows. The effects of blowing and suction position, and the blowing and suction mass flowrate, and on the flow control are presented in this paper. The optimal conditions for suppressing the wake of the cylinder are investigated by examining the flow separation and the near wake region; analyzing the aerodynamic force (lift and drag) fluctuations using the fast Fourier transform (FFT) to separate the effects of small-scale turbulent structures in the wake region. A method for stochastic analysis using machine learning techniques is proposed. Three different novel machine learning methods were applied to CFD results to predict the variation in drag coefficient due to the vortex shedding. Although, the prediction power of all the methods utilized is in the acceptable accuracy range, the Gaussian process regression (GPR) method is more accurate with an R-2(coefficient of determination) > 0.95. The results indicate that by optimizing the blowing and suction parameters like mass flowrate, slot location, and the slot configuration, up to 20% reduction can be achieved in the drag coefficient.
Molecular dynamic approach to predict thermo-mechanical properties of poly(butylene terephthalate)/CaCO3 nanocomposites
(2021) Seyedzavvar, Mirsadegh; Boğa, Cem; Akar, Samet; Pashmforoush, Farzad
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 - WoS: 10
Citation - Scopus: 12
Molecular Dynamic Approach To Predict Thermo-Mechanical Properties of Poly(Butylene Terephthalate)/Caco3 Nanocomposites
(Elsevier, 2021) Boga, Cem; Akar, Samet; Pashmforoush, Farzad; Seyedzavvar, Mirsadegh
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 - WoS: 1
Citation - Scopus: 1
Motion Control of a Spatial Elastic Manipulator in the Presence of Measurement Noises
(Springer Heidelberg, 2021) Kilicaslan, Sinan; Ider, S. Kemal; Ozgoren, M. Kemal
This paper presents a method for the end effector motion control of a spatial three-link robot having elastic second and third links including measurement noises. In the derivation of equations of motion, not to face with complex equations of motion, each link is modeled as though the links are not connected and the restrictions on the links due to connecting them by joints are written as constraint equations. After that the Lagrange multipliers are eliminated and the constraint equations at the acceleration level are substituted into the equations of motion to reduce the number of equations. To handle the non-minimum phase property, the equations of motion of the elastic manipulator are divided as the equations corresponding to a pseudostatic equilibrium and the equations of the deviations from them. Definition of the pseudostatic equilibrium used in this study can be given as a hypothetical state in which the end effector velocity and the end effector acceleration possess their reference values while the elastic deflections are instantly constant. The advantages of this control method are that the elastic deflections and the control inputs required for the pseudostatic equilibrium are obtained by an algebraic method and the feedback stabilization control inputs for the deviation equations are determined without linearizing the dynamic equations. The required measurements are obtained from the strain gauges on the links, the encoders placed on the joints and the position sensors attached to the end effector. For each sensor, a low pass filter is used. Simulations are made with low and high values of crossover frequencies to show the positive and negative effects of filtering on the responses of the system.
Citation - WoS: 11
Citation - Scopus: 11
A Novel Cfd-Ann Approach for Plunger Valve Optimization: Cost-Effective Performance Enhancement
(Elsevier Sci Ltd, 2024) Kaak, Abdul Rahman Sabra; Celebiog, Kutay; Bozkus, Zafer; Ulucak, Oguzhan; Ayli, Ece
This paper introduces a novel computational fluid dynamics-artificial neural network (CFD-ANN) approach that has been devised to enhance the efficiency of plunger valves. The primary emphasis of this research is to achieve an optimal equilibrium between hydraulic flow and geometric configuration. This study is a novel contribution to the field as it explores the flow dynamics of plunger valves using Computational Fluid Dynamics (CFD) and proposes a unique methodology by incorporating Machine Learning (ML) for performance forecasting. An artificial neural network (ANN) architecture was developed using a thorough comprehension of flow physics and the impact of geometric parameters acquired through computational fluid dynamics (CFD). Using optimization, the primary aspects of the Artificial Neural Network (ANN), including the learning algorithm and the number of hidden layers, have been modified. This refinement has resulted in the development of an architecture exhibiting a remarkably high R2 value of 0.987. This architectural design was employed to optimize the plunger valve. By utilizing Artificial Neural Networks (ANN), a comprehensive analysis comprising 1000 distinct configurations was effectively performed, resulting in a significant reduction in time expenditure compared to relying on Computational Fluid Dynamics (CFD). The result was a refined arrangement that achieved maximum head loss, subsequently verified using computational fluid dynamics (CFD) simulations, resulting in a minimal discrepancy of 2.66%. The efficacy of artificial neural networks (ANN) becomes apparent due to their notable cost-efficiency, along with their capacity to produce outcomes that are arduous and expensive to get through conventional optimization research utilizing computational fluid dynamics (CFD).
Citation - WoS: 11
Citation - Scopus: 14
Numerical Study on Effects of Computational Domain Length on Flow Field in Standing Wave Thermoacoustic Couple
(Elsevier Sci Ltd, 2019) Turkoglu, Hasmet; Mergen, Suhan; Yildirim, Ender
For the analysis of thermoacoustic (TA) devices, computational methods are commonly used. In the computational studies found in the literature, the flow domain has been modelled differently by different researchers. A common approach in modelling the flow domain is to truncate the computational domain around the stack, instead of modelling the whole resonator to save computational time. However, where to truncate the domain is not clear. In this study, we have investigated how the simulation results are affected by the computational domain length (I-d) when the truncated domain approach is used. For this purpose, a standing wave TA couple which undergoes a refrigeration cycle was considered. The stack plate thickness was assumed to be zero and the simulations were performed for six different dimensionless domain length (I-d/lambda) varying between 0.029 and 0.180. Frequency and Mach number were taken as 100 Hz and 0.01, respectively, and kept constant for all the cases considered. The mean pressure and the pressure amplitude were taken as 10 kPa and 170 Pa, respectively (Drive ratio of 1.7%). Helium was considered as the working fluid. To assess the accuracy of the simulation results, the pressure distributions across the domain were compared with that of the standing wave. In addition to the pressure variation, the effects of the domain length on the phase delay of the pressure and velocity waves along the stack plate were also investigated. The results showed that with the increasing I-d/lambda. ratio, the simulated pressure distribution compares better with the standing wave pressure distribution. With the lowest I-d/lambda ratio (0.029) considered, the difference between the amplitudes of the computed pressure distribution and theoretical standing wave pressure distribution was approximately 50 Pa. However, as I-d/lambda value increases, the simulation results approach to the theoretical standing wave pressure distribution better. The computational results obtained with Id/lambda = 0.132 and 0.180, were almost identical with standing wave acoustic field. Hence, it was concluded that the domain length has a significant effect on the accuracy of the computational results when the truncated domain approach is used. It was also observed that for a given TA device and operating parameters, there is a minimum I-d/lambda value for obtaining reliable results.
Citation - WoS: 2
Citation - Scopus: 2
Parametric Analysis of an Anti-Whiplash System Composed of a Seat Suspension Arrangement
(Springer Heidelberg, 2015) Ider, Sitki Kemal; Gokler, Mustafa Ilhan; Ozdemir, Mustafa
Neck injuries frequently seen in low-speed rear-end collisions are referred to as whiplash injuries. Most of the proposed anti-whiplash systems in the literature rely on reducing the backset. A relatively new and promising alternative concept is a slideable seat. This study aimed to parametrically analyze an anti-whiplash vehicle seat that can slide backward against a horizontal suspension arrangement composed of a spring and a damper in response to a rear-end collision, and to investigate the effects of the suspension parameters on the injury risk. A simplified model of a slideable vehicle seat is developed, and simulations are conducted in LS-DYNA (R) environment using this slideable seat model and the commercially available finite element model of the BioRID II dummy. The maximum value of the Neck Injury Criterion (NICmax) is used as the measure of the injury risk. As a result, a strong linear inverse correlation is observed between NICmax and the maximum seat sliding distance, while the stiffness and damping coefficients of the suspension are varied. This result is also verified by obtaining the same NICmax value for the same maximum seat sliding distance (although the stiffness and damping coefficients are different). It is also shown that, for a given backset value as large as 60 mm, a slideable seat with the suspension parameters selected to yield a reasonable maximum seat sliding distance such as 100 mm significantly improves NICmax compared to a standard seat. As the maximum seat sliding distance is increased, the injury risk becomes smaller.
Citation - WoS: 30
Citation - Scopus: 33
Performance and Surface Alloying Characteristics of Cu-Cr and Cu-Mo Powder Metal Tool Electrodes in Electrical Discharge Machining
(Taylor & Francis inc, 2016) Uslan, Ibrahim; Usta, Yusuf; Cogun, Can; Gulcan, Orhan
The main objective of this study is to investigate the effect of Cu-Cr and Cu-Mo powder metal (PM) tool electrodes on electrical discharge machining (EDM) performance outputs. The EDM performance measures used in the study are material removal rate (MRR), tool electrode wear rate (EWR), average workpiece surface roughness (R-a), machined workpiece surface hardness, abrasive wear resistance, corrosion resistance, and workpiece alloyed layer depth and composition. The EDM performance of Cu-Cr and Cu-Mo PM electrodes produced at three different mixing ratios (15, 25, and 35wt% Cr or Mo), compacting pressures (P-c = 600, 700, and 800MPa), and sintering temperatures (T-s = 800, 850, and 900 degrees C) are compared with those machined with electrolytic Cu and Cu PM electrodes when machining SAE 1040 steel workpiece. Analyses revealed that tool materials were deposited as a layer over the work surface yielding high surface hardness, strong abrasion, and corrosion resistance. Moreover, the mixing ratio, P-c, and T-s affect the MRR, EWR, and R-a values.
Citation - WoS: 1
Citation - Scopus: 1
Performance Determination of Axial Wind Tunnel Fan With Reverse Engineering, Numerical and Experimental Methods
(Asme, 2022) Ayli, Ece; Kocak, Eyup
In today's technology, in case of the need for rehabilitation, renovation, or damage, it is necessary to recover the problems quickly with a cost-effective approach. In the case of destructive failure, or misdesign of the devices, replacing the problematic part with the new design is crucial. In order to substitute the related part with the efficient one, reverse engineering (RE) methodology is utilized. In this paper, from the perspective of engineering implementation and based on the idea of reverse engineering, axial wind tunnel fan is rehabilitated using numerical and experimental methods. The current study is focused on an axial pressurization fan placed into Cankaya University Mechanical Engineering Laboratory wind tunnel that has firm guaranteed specifications of 5.55 m(3)/s airflow capacity. The measurements performed during experiments showed that the fan provides less than 60% airflow compared with firm guaranteed specifications. In order to determine the problems of the existing fan, a reverse engineering methodology is developed, and the noncontact data acquisition method is used to form a computer aided drawing (CAD) model. A computational fluid dynamics (CFD) methodology is developed to analyze existing geometry numerically, and results are compared with an experimental study to verify numerical methodology. According to the results, the prediction accuracy of the numerical method can attain 92.95% and 96.38% for flowrate and efficiency, respectively, at the maximum error points.
Citation - WoS: 1
Citation - Scopus: 1
Prediction of the Onset of Shear Localization Based on Machine Learning
(Cambridge Univ Press, 2023) Ayli, Ece; Ulucak, Oguzhan; Ugurer, Doruk; Akar, Samet
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 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.

Browse

Browsing Makine Mühendisliği Bölümü Yayın Koleksiyonu by WoS Q "Q2"