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Abrasive Waterjet Machining (AWJM) is considered a viable alternative to conventional machining processes, due to its capability of rendering even complex features on parts with high productivity. However, it is currently also important for manufacturing processes to comply with the various aspects of sustainability, by putting emphasis on the environmental dimension apart from the economic. Although AWJM generally is considered an inherently environmentally friendly process, it is required that thorough experimental studies be carried out to evaluate the sustainability of AWJM under various conditions. In the present work, AWJM experiments under various conditions were conducted on a Ti-6Al-4V workpiece in order to determine the optimal conditions leading to a high degree of sustainability in this process based on several indicators. The experiments were carried out using glass beads, which act as an eco-friendly abrasive. After the basic outcome of the experiment was analyzed to determine the correlations between process parameters and depth of penetration, kerf width, and kerf taper angle, sustainability analysis with the aid of Grey Relational Analysis (GRA) was conducted. The optimum solution provided a sufficiently high score regarding both the economic and environmental dimensions of sustainability.
Nikolaos E. Karkalos; Panagiotis Karmiris-Obratański; Rafał Kudelski; Angelos P. Markopoulos. Experimental Study on the Sustainability Assessment of AWJ Machining of Ti-6Al-4V Using Glass Beads Abrasive Particles. Sustainability 2021, 13, 8917 .
AMA StyleNikolaos E. Karkalos, Panagiotis Karmiris-Obratański, Rafał Kudelski, Angelos P. Markopoulos. Experimental Study on the Sustainability Assessment of AWJ Machining of Ti-6Al-4V Using Glass Beads Abrasive Particles. Sustainability. 2021; 13 (16):8917.
Chicago/Turabian StyleNikolaos E. Karkalos; Panagiotis Karmiris-Obratański; Rafał Kudelski; Angelos P. Markopoulos. 2021. "Experimental Study on the Sustainability Assessment of AWJ Machining of Ti-6Al-4V Using Glass Beads Abrasive Particles." Sustainability 13, no. 16: 8917.
Surface quality has always been an important goal in the manufacturing industry, as it is not only related to the achievement of appropriate geometrical tolerances but also plays an important role in the tribological behavior of the surface as well as its resistance to fatigue and corrosion. Usually, in order to achieve sufficiently high surface quality, process parameters, such as cutting speed and feed, are regulated or special types of cutting tools are used. In the present work, an alternative strategy for slot milling is adopted, namely, trochoidal milling, which employs a more complex trajectory for the cutting tool. Two series of experiments were initially conducted with traditional and trochoidal milling under various feed and cutting speed values in order to evaluate the capabilities of trochoidal milling. The findings showed a clear difference between the two milling strategies, and it was shown that the trochoidal milling strategy is able to provide superior surface quality when the appropriate process parameters are also chosen. Finally, the effect of the depth of cut, coolant and trochoidal stepover on surface roughness during trochoidal milling was also investigated, and it was found that lower depths of cut, the use of coolant and low values of trochoidal stepover can lead to a considerable decrease in surface roughness.
Nikolaos Karkalos; Panagiotis Karmiris-Obratański; Szymon Kurpiel; Krzysztof Zagórski; Angelos Markopoulos. Investigation on the Surface Quality Obtained during Trochoidal Milling of 6082 Aluminum Alloy. Machines 2021, 9, 75 .
AMA StyleNikolaos Karkalos, Panagiotis Karmiris-Obratański, Szymon Kurpiel, Krzysztof Zagórski, Angelos Markopoulos. Investigation on the Surface Quality Obtained during Trochoidal Milling of 6082 Aluminum Alloy. Machines. 2021; 9 (4):75.
Chicago/Turabian StyleNikolaos Karkalos; Panagiotis Karmiris-Obratański; Szymon Kurpiel; Krzysztof Zagórski; Angelos Markopoulos. 2021. "Investigation on the Surface Quality Obtained during Trochoidal Milling of 6082 Aluminum Alloy." Machines 9, no. 4: 75.
Abrasive waterjet cutting is a well-established non-conventional technique for the processing of difficult-to-cut material and rendering of various complex geometries with high accuracy. However, as in every machining process, it is also required that high efficiency and productivity are achieved. For that reason, in the present study, the effect of performing the machining process by multiple passes is investigated, and the evaluation of this approach is performed in terms of total depth of penetration, kerf width, kerf taper angle, mean material removal rate, and cutting efficiency. In the case of multiple passes, the passes are performed in the same direction with the traverse speed adjusted accordingly in order to maintain the total machining time constant in each case. From the experimental results, it was found that the effect of multiple passes on the kerf characteristics, mean material removal rate, and cutting efficiency depends on the process conditions, especially regarding the depth of penetration, and it is possible to achieve significantly higher efficiency by the multi-pass cutting technique when the appropriate process conditions are selected.
Panagiotis Karmiris-Obratański; Nikolaos E. Karkalos; Rafał Kudelski; Emmanouil L. Papazoglou; Angelos P. Markopoulos. On the Effect of Multiple Passes on Kerf Characteristics and Efficiency of Abrasive Waterjet Cutting. Metals 2021, 11, 74 .
AMA StylePanagiotis Karmiris-Obratański, Nikolaos E. Karkalos, Rafał Kudelski, Emmanouil L. Papazoglou, Angelos P. Markopoulos. On the Effect of Multiple Passes on Kerf Characteristics and Efficiency of Abrasive Waterjet Cutting. Metals. 2021; 11 (1):74.
Chicago/Turabian StylePanagiotis Karmiris-Obratański; Nikolaos E. Karkalos; Rafał Kudelski; Emmanouil L. Papazoglou; Angelos P. Markopoulos. 2021. "On the Effect of Multiple Passes on Kerf Characteristics and Efficiency of Abrasive Waterjet Cutting." Metals 11, no. 1: 74.
The hardened tool steel AISI O1 has increased strength, hardness, and wear resistance, which affects the complexity of the machining process. AISI O1 has also been classified as difficult to cut material hence optimum cutting parameters are required for the sustainable machining of the alloy. In this work, the effect of feed peer tooth (fz), cutting speed (vc), cutting of depth (ap) on surface roughness (Ra, Rt), cutting force (Fx, Fy), cutting power (Pc), machining cost (Ci), and carbon dioxide (Ene) were investigated during the slot milling process of AISI O1 hardened steel. A regression analysis was carried out on the obtained experimental results and the induction of nonlinear mathematical equations of surface roughness, cutting force, cutting power, and machining cost with a high coefficient of determination (R2 = 90.62–98.74%) were deduced. A sustainability assessment model is obtained for optimal and stable levels of design variables when slot milling AISI O1 tool steel. Stable indicators to ensure personal health and safety of operation, P1 values were set to “1” at a cutting speed of 20 m/min or 43.3 m/min and “2” at a cutting speed of 66.7 m/min or 90 m/min. It is revealed that for eco-benign machining of AISI O1, the optimum parameters of 0.01 mm/tooth, 20 m/min, and 0.1 mm should be adopted for feed rate, cutting speed, and depth of cut respectively.
Angelos P. Markopoulos; Nikolaos E. Karkalos; Mozammel Mia; Danil Yurievich Pimenov; Munish Kumar Gupta; Hussein Hegab; Navneet Khanna; Vincent Aizebeoje Balogun; Shubham Sharma. Sustainability Assessment, Investigations, and Modelling of Slot Milling Characteristics in Eco-Benign Machining of Hardened Steel. Metals 2020, 10, 1650 .
AMA StyleAngelos P. Markopoulos, Nikolaos E. Karkalos, Mozammel Mia, Danil Yurievich Pimenov, Munish Kumar Gupta, Hussein Hegab, Navneet Khanna, Vincent Aizebeoje Balogun, Shubham Sharma. Sustainability Assessment, Investigations, and Modelling of Slot Milling Characteristics in Eco-Benign Machining of Hardened Steel. Metals. 2020; 10 (12):1650.
Chicago/Turabian StyleAngelos P. Markopoulos; Nikolaos E. Karkalos; Mozammel Mia; Danil Yurievich Pimenov; Munish Kumar Gupta; Hussein Hegab; Navneet Khanna; Vincent Aizebeoje Balogun; Shubham Sharma. 2020. "Sustainability Assessment, Investigations, and Modelling of Slot Milling Characteristics in Eco-Benign Machining of Hardened Steel." Metals 10, no. 12: 1650.
Grinding at the nanometric level can be efficiently employed for the creation of surfaces with ultrahigh precision by removing a few atomic layers from the substrate. However, since measurements at this level are rather difficult, numerical investigation can be conducted in order to reveal the mechanisms of material removal during nanogrinding. In the present study, a Molecular Dynamics model with multiple abrasive grains is developed in order to determine the effect of spacing between the adjacent rows of abrasive grains and the effect of the rake angle of the abrasive grains on the grinding forces and temperatures, ground surface, and chip formation and also, subsurface damage of the substrate. Findings indicate that nanogrinding with abrasive grains situated in adjacent rows with spacing of 1 Å leads directly to a flat surface and the amount of material remaining between the rows of grains remains minimal for spacing values up to 5 Å. Moreover, higher negative rake angle of the grains leads to higher grinding forces and friction coefficient values over 1.0 for angles larger than −40°. At the same time, chip formation is suppressed and plastic deformation increases with larger negative rake angles, due to higher compressive action of the abrasive grains.
Nikolaos E. Karkalos; Angelos P. Markopoulos. Molecular Dynamics Study of the Effect of Abrasive Grains Orientation and Spacing during Nanogrinding. Micromachines 2020, 11, 712 .
AMA StyleNikolaos E. Karkalos, Angelos P. Markopoulos. Molecular Dynamics Study of the Effect of Abrasive Grains Orientation and Spacing during Nanogrinding. Micromachines. 2020; 11 (8):712.
Chicago/Turabian StyleNikolaos E. Karkalos; Angelos P. Markopoulos. 2020. "Molecular Dynamics Study of the Effect of Abrasive Grains Orientation and Spacing during Nanogrinding." Micromachines 11, no. 8: 712.
Impellers are the most crucial components of pumps, as they directly determine the velocity profile of the fluid flowing through the pump and its efficiency. Given that the impellers have a complex geometry, they pose an important challenge to the manufacturer in order to construct them with the best possible dimensional accuracy and surface quality, and also achieve short machining times. In the present paper, the machining operations for the manufacture of a radial impeller were designed and implemented for the case of a single-entry semi-closed radial flow impeller. At first, the best milling strategies, optimum cutting conditions, and appropriate cutting tools were selected for each of the three machining phases, namely, roughing, semi-finishing, and finishing. Then, an experimental investigation was conducted, especially for the optimum process conditions during finishing of impeller blades, using Taguchi L16 orthogonal array. After the analysis of surface roughness was conducted for the 16 experiments, it was found that the most important parameters were spindle speed and feed. Furthermore, the optimum settings were determined as the maximum spindle speed and the lowest feed per tooth value and a regression model correlating process parameters with surface roughness was established with a high degree of accuracy.
Fotios I. Stratogiannis; Nikolaos I. Galanis; Nikolaos E. Karkalos; Angelos P. Markopoulos. Optimization of the Manufacturing Strategy, Machining Conditions, and Finishing of a Radial Impeller. Machines 2019, 8, 1 .
AMA StyleFotios I. Stratogiannis, Nikolaos I. Galanis, Nikolaos E. Karkalos, Angelos P. Markopoulos. Optimization of the Manufacturing Strategy, Machining Conditions, and Finishing of a Radial Impeller. Machines. 2019; 8 (1):1.
Chicago/Turabian StyleFotios I. Stratogiannis; Nikolaos I. Galanis; Nikolaos E. Karkalos; Angelos P. Markopoulos. 2019. "Optimization of the Manufacturing Strategy, Machining Conditions, and Finishing of a Radial Impeller." Machines 8, no. 1: 1.
Apart from experimental research, the development of accurate and efficient models is considerably important in the field of manufacturing processes. Initially, regression models were significantly popular for this purpose, but later, the soft computing models were proven as a viable alternative to the established models. However, the effectiveness of soft computing models can be often dependent on the size of the experimental dataset, and it can be lower compared to that of the regression models for a small-sized dataset. In the present study, it is intended to conduct a comparison of the performance of various neural network models, such as the Multi-layer Perceptron (MLP), the Radial Basis Function Neural Network (RBF-NN), and the Adaptive Neuro-Fuzzy Inference System (ANFIS) models with the performance of a multiple regression model. For the development of the models, data from drilling experiments on an Al6082-T6 workpiece for various process conditions are employed, and the performance of models related to thrust force (Fz) and cutting torque (Mz) is assessed based on several criteria. From the analysis, it was found that the MLP models were superior to the other neural networks model and the regression model, as they were able to achieve a relatively lower prediction error for both models of Fz and Mz.
Nikolaos E. Karkalos; Nikolaos Efkolidis; Panagiotis Kyratsis; Angelos P. Markopoulos. A Comparative Study between Regression and Neural Networks for Modeling Al6082-T6 Alloy Drilling. Machines 2019, 7, 13 .
AMA StyleNikolaos E. Karkalos, Nikolaos Efkolidis, Panagiotis Kyratsis, Angelos P. Markopoulos. A Comparative Study between Regression and Neural Networks for Modeling Al6082-T6 Alloy Drilling. Machines. 2019; 7 (1):13.
Chicago/Turabian StyleNikolaos E. Karkalos; Nikolaos Efkolidis; Panagiotis Kyratsis; Angelos P. Markopoulos. 2019. "A Comparative Study between Regression and Neural Networks for Modeling Al6082-T6 Alloy Drilling." Machines 7, no. 1: 13.
The term “Swarm Intelligence” refers directly to the collective behavior of a group of animals, which are following very basic rules, or to an Artificial Intelligence approach, which aims at the solution of a problem using algorithms based on collective behavior of social animals. For over three decades, several algorithms based on the observation of the behavior of groups of animals were developed, such as Particle Swarm Optimization, from the observation of flocks of birds. Some of the most established Swarm Intelligence (SI) methods include the Ant Colony Optimization method, the Harmony Search method and the Artificial Bee Colony algorithm.
Nikolaos E. Karkalos; Angelos P. Markopoulos; João Paulo Davim. Swarm Intelligence-Based Methods. Tunable Low-Power Low-Noise Amplifier for Healthcare Applications 2018, 33 -55.
AMA StyleNikolaos E. Karkalos, Angelos P. Markopoulos, João Paulo Davim. Swarm Intelligence-Based Methods. Tunable Low-Power Low-Noise Amplifier for Healthcare Applications. 2018; ():33-55.
Chicago/Turabian StyleNikolaos E. Karkalos; Angelos P. Markopoulos; João Paulo Davim. 2018. "Swarm Intelligence-Based Methods." Tunable Low-Power Low-Noise Amplifier for Healthcare Applications , no. : 33-55.
In the current section, several metaheuristics involving the evolutionary of a population in order to create new generations of genetically superior individuals are presented. These algorithms are usually significantly influenced by the most prominent (and earliest) among them, the Genetic Algorithm (GA). Details about their basic characteristics and function, as well as some important variants, are described and applications in the field of industrial engineering are highlighted. A detailed description of the basic features of the genetic algorithm is presented at the beginning of this chapter and afterwards, other Evolutionary Algorithms (EA) are summarized. In specific, both relatively older and well established, as well as newer but promising methods are included, namely Differential Evolutionary, Memetic Algorithm, Imperialist Competitive Algorithm, Biogeography-Based Optimization algorithm, Teaching-Learning-Based optimization, Sheep Flock Heredity algorithm, Shuffled Frog-Leaping algorithm, and Bacteria Foraging Optimization algorithm.
Nikolaos E. Karkalos; Angelos P. Markopoulos; J. Paulo Davim. Evolutionary-Based Methods. Tunable Low-Power Low-Noise Amplifier for Healthcare Applications 2018, 11 -31.
AMA StyleNikolaos E. Karkalos, Angelos P. Markopoulos, J. Paulo Davim. Evolutionary-Based Methods. Tunable Low-Power Low-Noise Amplifier for Healthcare Applications. 2018; ():11-31.
Chicago/Turabian StyleNikolaos E. Karkalos; Angelos P. Markopoulos; J. Paulo Davim. 2018. "Evolutionary-Based Methods." Tunable Low-Power Low-Noise Amplifier for Healthcare Applications , no. : 11-31.
The design and manufacturing of medical implants constitutes an active and highly important field of research, both from a medical and an engineering point of view. From an engineering aspect, the machining of implants is undoubtedly challenging due to the complex shape of the implants and the associated restrictive geometrical and dimensional requirements. Furthermore, it is crucial to ensure that the surface integrity of the implant is not severely affected, in order for the implant to be durable and wear resistant. In the present work, the methodology of designing and machining the femoral component of total knee replacement using a 3-axis Computer Numerical Control (CNC) machine is presented, and then, the results of the machining process, as well as the evaluation of implant surface quality are discussed in detail. At first, a preliminary design of the components of the knee implant is performed and the planning for the production of the femoral component is implemented in Computed Aided Manufacturing (CAM) software. Then, three femoral components are machined under different process conditions and the surface quality is evaluated in terms of surface roughness. Analysis of the results indicated the appropriate process conditions for each part of the implant surface and led to the determination of optimum machining strategy for the finishing stage.
Angelos P. Markopoulos; Nikolaos I. Galanis; Nikolaos E. Karkalos; Dimitrios E. Manolakos. Precision CNC Machining of Femoral Component of Knee Implant: A Case Study. Machines 2018, 6, 10 .
AMA StyleAngelos P. Markopoulos, Nikolaos I. Galanis, Nikolaos E. Karkalos, Dimitrios E. Manolakos. Precision CNC Machining of Femoral Component of Knee Implant: A Case Study. Machines. 2018; 6 (1):10.
Chicago/Turabian StyleAngelos P. Markopoulos; Nikolaos I. Galanis; Nikolaos E. Karkalos; Dimitrios E. Manolakos. 2018. "Precision CNC Machining of Femoral Component of Knee Implant: A Case Study." Machines 6, no. 1: 10.