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Special Issue "Machining—Recent Advances, Applications and Challenges"

A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: closed (31 May 2019).

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A printed edition of this Special Issue is available here.

Special Issue Editors

Prof. Dr. Luis Norberto López De Lacalle
E-Mail Website
Guest Editor
Department of Mechanical Engineering (High Performance Manufacturing Group), University of the Basque Country (UPV/EHU), Parque Tecnológico de Zamudio 202, 48170 Bilbao, Spain
Interests: manufacturing process; aeronautics; machine tools; Industry 4.0; machining
Special Issues and Collections in MDPI journals
Dr. Gorka Urbicain
E-Mail Website
Guest Editor
Department of Mechanical Engineering, University of the Basque Country (UPV/EHU), Plaza Europa 1, 20018 San Sebastián, Spain
Interests: modeling of metal removal processes; machining dynamics; chatter vibrations
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues,

In 1907, the American engineer, F.W. Taylor, exposed the basis and fundamentals of modern machining concepts, such as the relationship between tool life and cutting speed, the economic optimization of the machining processes, and modern management of industrial companies, which along with previous developments of new grades of high-alloyed steels (HSS) for the production of cutting tools, promoted a rapid evolution of machining processes. In the 20th century, continuous advances happened one after the other, related to the invention of sintered carbide tools, coatings, the introduction of CNC in machine-tools, multitasking and multiprocess concepts, etc. At the start of this century, machining remains the key operation to achieve high productivity and precision for high-added value parts in several sectors. Continous research is performed and new ideas are constantly considered.

This Special Issue is open to new advances in machining aspects, involving:

  • High performance operations for difficult-to-cut alloys, wrought and cast materials, light alloys, ceramics, etc.
  • Cutting tools, grades, substrates and coatings. Wear damage.
  • New applications of machining in high-added value components, for aeronautics, automotive, windmill, energy, and other key sectors.
  • Heat in metal cutting: Heat sources, accuracy in machining, prediction and measurements of temperatures in the cutting zone.
  • New approaches in the tribology of the cutting process.
  • Advanced cooling in machining: Minimum quantity of lubricant, dry or cryogenics.
  • Modelling, focused on the reduction of risks, the process outcome, and to maintain surface integrity.
  • Vibration problems in machines: Active and passive/predictive methods, sources, diagnosis and avoidance.
  • Influence of machining in new concepts of machine–tool, and machine static and dynamic behaviors.
  • Machinability of new composites, brittle and emerging materials.
  • Sensor-assisted machining: Sensors and system architecture, intelligent/smart tools.
  • Machining economics and optimization: Advanced methods.
  • Assisted machining processes by high-pressure, laser, US and others.
  • Micromachining, challenges and applications.
  • Introduction of new analytics and decision making into machining programming.

Prof. Dr. Luis Norberto López De Lacalle
Dr. Gorka Urbicain
Guest Editors

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Keywords

  • machining
  • machine-tools
  • cutting tools
  • machinability
  • modelling
  • tribology

Published Papers (33 papers)

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Research

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Article
Trochoidal Milling and Neural Networks Simulation of Magnesium Alloys
Materials 2019, 12(13), 2070; https://doi.org/10.3390/ma12132070 - 27 Jun 2019
Cited by 13 | Viewed by 1240
Abstract
This paper set out to investigate the effect of cutting speed vc and trochoidal step str modification on selected machinability parameters (the cutting force components and vibration). In addition, for a more detailed analysis, selected surface roughness parameters were investigated. The [...] Read more.
This paper set out to investigate the effect of cutting speed vc and trochoidal step str modification on selected machinability parameters (the cutting force components and vibration). In addition, for a more detailed analysis, selected surface roughness parameters were investigated. The research was carried out for two grades of magnesium alloys—AZ91D and AZ31—and aimed to determine stable machining parameters and to investigate the dynamics of the milling process, i.e., the resulting change in the cutting force components and in vibration. The tests were performed for the specified range of cutting parameters: vc = 400–1200 m/min and str = 5–30%. The results demonstrate a significant effect of cutting data modification on the parameter under scrutiny—the increase in vc resulted in the reduction of the cutting force components and the displacement and level of vibration recorded in tests. Selected cutting parameters were modelled by means of Statistica Artificial Neural Networks (Radial Basis Function and Multilayered Perceptron), which, furthermore, confirmed the suitability of neural networks as a tool for prediction of the cutting force and vibration in milling of magnesium alloys. Full article
(This article belongs to the Special Issue Machining—Recent Advances, Applications and Challenges)
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Article
A Study on the Laser-Assisted Machining of Carbon Fiber Reinforced Silicon Carbide
Materials 2019, 12(13), 2061; https://doi.org/10.3390/ma12132061 - 27 Jun 2019
Cited by 11 | Viewed by 1551
Abstract
In recent years, as replacements for traditional manufacturing materials, monolithic ceramics and carbon fiber reinforced silicon carbide (C/SiC) ceramic matrix composites have seen significantly increased usage due to their superior characteristics of relatively low density, lightweight, and good high temperature mechanical properties. Demand [...] Read more.
In recent years, as replacements for traditional manufacturing materials, monolithic ceramics and carbon fiber reinforced silicon carbide (C/SiC) ceramic matrix composites have seen significantly increased usage due to their superior characteristics of relatively low density, lightweight, and good high temperature mechanical properties. Demand for difficult-to-cut materials is increasing in a variety of area such as the automotive and aerospace industries, but these materials are inherently difficult to process because of their high hardness and brittleness. When difficult-to-cut materials are processed by conventional machining, tool life and quality are reduced due to the high cutting force and temperatures. Laser-assisted machining (LAM) is a method of cutting a workpiece by preheating with a laser heat source and lowering the strength of the material. LAM has been studied by many researchers, but studies on LAM of carbon–ceramic composites have been carried out by only a few researchers. This paper focuses on deducing the optimal machining parameters in the LAM of C/SiC. In this study, the Taguchi method is used to obtain the major parameters for the analysis of cutting force and surface roughness under various machining conditions. Before machining experiments, finite element analysis is performed to determine the effective depth of the cut. The cutting parameters for the LAM operation are the depth of cut, preheating temperature, feed rate, and spindle speed. The signal to noise (S/N) ratio and variance analysis (ANOVA) of the cutting force and surface roughness are analyzed, and the response optimization method is used to suggest the optimal machining parameters. Full article
(This article belongs to the Special Issue Machining—Recent Advances, Applications and Challenges)
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Article
Analysis of Secondary Adhesion Wear Mechanism on Hard Machining of Titanium Aerospace Alloy
Materials 2019, 12(12), 2015; https://doi.org/10.3390/ma12122015 - 23 Jun 2019
Cited by 8 | Viewed by 1327
Abstract
Titanium alloys are widely used in important manufacturing sectors such as the aerospace industry, internal components of motor or biomechanical components, for the development of functional prostheses. The relationship between mechanical properties and weight and its excellent biocompatibility have positioned this material among [...] Read more.
Titanium alloys are widely used in important manufacturing sectors such as the aerospace industry, internal components of motor or biomechanical components, for the development of functional prostheses. The relationship between mechanical properties and weight and its excellent biocompatibility have positioned this material among the most demanded for specific applications. However, it is necessary to consider the low machinability as a disadvantage in the titanium alloys features. This fact is especially due to the low thermal conductivity, producing significant increases in the temperature of the contact area during the machining process. In this aspect, one of the main objectives of strategic industries is focused on the improvement of the efficiency and the increase of the service life of the elements involved in the machining of this alloy. With the aim to understand the most relevant effects in the machinability of the Ti6Al4V alloy, an analysis is required of different variables of the machining process like tool wear evolution, based on secondary adhesion mechanisms, and the relation between surface roughness of the work-pieces with the cutting parameters. In this research work, a study on the machinability of Ti6Al4V titanium alloy has been performed. For that purpose, in a horizontal turning process, the influence of cutting tool wear effects has been evaluated on the surface finish of the machined element. As a result, parametric behavior models for average roughness (Ra) have been determined as a function of the machining parameters used. Full article
(This article belongs to the Special Issue Machining—Recent Advances, Applications and Challenges)
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Article
Investigation of Tool Wear and Chip Morphology in Dry Trochoidal Milling of Titanium Alloy Ti–6Al–4V
Materials 2019, 12(12), 1937; https://doi.org/10.3390/ma12121937 - 16 Jun 2019
Cited by 14 | Viewed by 1456
Abstract
Titanium alloys are widely used in the manufacture of aircraft and aeroengine components. However, tool wear is a serious concern in milling titanium alloys, which are known as hard-to-cut materials. Trochoidal milling is a promising technology for the high-efficiency machining of hard-to-cut materials. [...] Read more.
Titanium alloys are widely used in the manufacture of aircraft and aeroengine components. However, tool wear is a serious concern in milling titanium alloys, which are known as hard-to-cut materials. Trochoidal milling is a promising technology for the high-efficiency machining of hard-to-cut materials. Aiming to realize green machining titanium alloy, this paper investigates the effects of undeformed chip thickness on tool wear and chip morphology in the dry trochoidal milling of titanium alloy Ti–6Al–4V. A tool wear model related to the radial depth of cut based on the volume of material removed (VMR) is established for trochoidal milling, and optimized cutting parameters in terms of cutting speed and axial depth of cut are selected to improve machining efficiency through reduced tool wear. The investigation enables the environmentally clean rough machining of Ti–6Al–4V. Full article
(This article belongs to the Special Issue Machining—Recent Advances, Applications and Challenges)
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Article
Parametric Optimization of Trochoidal Step on Surface Roughness and Dish Angle in End Milling of AISID3 Steel Using Precise Measurements
Materials 2019, 12(8), 1335; https://doi.org/10.3390/ma12081335 - 24 Apr 2019
Cited by 10 | Viewed by 1621
Abstract
Tool steel play a vital role in modern manufacturing industries due to its excellent properties. AISI D3 is a cold work tool steel which possess high strength, more hardenability and good wear resistance properties. It has a wide variety of applications in automobile [...] Read more.
Tool steel play a vital role in modern manufacturing industries due to its excellent properties. AISI D3 is a cold work tool steel which possess high strength, more hardenability and good wear resistance properties. It has a wide variety of applications in automobile and tool and die making industries such as blanking and forming tools, high stressed cutting, deep drawing and press tools. The novel ways of machining these steels and finding out the optimum process parameters to yield good output is of practical importance in the field of research. This research work explores an attempt to identify the optimized process parameter combinations in end milling of AISI D3 steel to yield low surface roughness and maximum dish angle using trochoidal milling tool path, which is considered as a novelty in this study. 20 experimental trials based on face centered central composite design (CCD) of response surface methodology (RSM) were executed by varying the input process factors such as cutting speed, feed rate and trochoidal step. Analysis of variance (ANOVA) was adopted to study the significance of selected process parameters and its relative interactions on the performance measures. Desirability-based multiple objective optimization was performed and the mathematical models were developed for prediction purposes. The developed mathematical model was statistically significant with optimum conditions of cutting speed of 41m/min, feed rate of 120 mm/min and trochoidal step of 0.9 mm. It was also found that the deviation between the experimental and predicted values is 6.10% for surface roughness and 1.33% for dish angle, respectively. Full article
(This article belongs to the Special Issue Machining—Recent Advances, Applications and Challenges)
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Article
Multi-Response Optimization of WEDM Process Parameters for Machining of Superelastic Nitinol Shape-Memory Alloy Using a Heat-Transfer Search Algorithm
Materials 2019, 12(8), 1277; https://doi.org/10.3390/ma12081277 - 18 Apr 2019
Cited by 21 | Viewed by 2067
Abstract
Nitinol, a shape-memory alloy (SMA), is gaining popularity for use in various applications. Machining of these SMAs poses a challenge during conventional machining. Henceforth, in the current study, the wire-electric discharge process has been attempted to machine nickel-titanium (Ni55.8Ti) super-elastic SMA. Furthermore, to [...] Read more.
Nitinol, a shape-memory alloy (SMA), is gaining popularity for use in various applications. Machining of these SMAs poses a challenge during conventional machining. Henceforth, in the current study, the wire-electric discharge process has been attempted to machine nickel-titanium (Ni55.8Ti) super-elastic SMA. Furthermore, to render the process viable for industry, a systematic approach comprising response surface methodology (RSM) and a heat-transfer search (HTS) algorithm has been strategized for optimization of process parameters. Pulse-on time, pulse-off time and current were considered as input process parameters, whereas material removal rate (MRR), surface roughness, and micro-hardness were considered as output responses. Residual plots were generated to check the robustness of analysis of variance (ANOVA) results and generated mathematical models. A multi-objective HTS algorithm was executed for generating 2-D and 3-D Pareto optimal points indicating the non-dominant feasible solutions. The proposed combined approach proved to be highly effective in predicting and optimizing the wire electrical discharge machining (WEDM) process parameters. Validation trials were carried out and the error between measured and predicted values was negligible. To ensure the existence of a shape-memory effect even after machining, a differential scanning calorimetry (DSC) test was carried out. The optimized parameters were found to machine the alloy appropriately with the intact shape memory effect. Full article
(This article belongs to the Special Issue Machining—Recent Advances, Applications and Challenges)
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Article
Model Based on an Effective Material-Removal Rate to Evaluate Specific Energy Consumption in Grinding
Materials 2019, 12(6), 939; https://doi.org/10.3390/ma12060939 - 21 Mar 2019
Cited by 4 | Viewed by 1118
Abstract
Grinding energy efficiency depends on the appropriate selection of cutting conditions, grinding wheel, and workpiece material. Additionally, the estimation of specific energy consumption is a good indicator to control the consumed energy during the grinding process. Consequently, this study develops a model of [...] Read more.
Grinding energy efficiency depends on the appropriate selection of cutting conditions, grinding wheel, and workpiece material. Additionally, the estimation of specific energy consumption is a good indicator to control the consumed energy during the grinding process. Consequently, this study develops a model of material-removal rate to estimate specific energy consumption based on the measurement of active power consumed in a plane surface grinding of C45K with different thermal treatments and AISI 304. This model identifies and evaluates the dissipated power by sliding, ploughing, and chip formation in an industrial-scale grinding process. Furthermore, the instantaneous positions of abrasive grains during cutting are described to study the material-removal rate. The estimation of specific chip-formation energy is similar to that described by other authors on a laboratory scale, which allows to validate the model and experiments. Finally, the results show that the energy consumed by sliding is the main mechanism of energy dissipation in an industrial-scale grinding process, where it is denoted that sliding energy by volume unity decreases as the depth of cut and the speed of the workpiece increase. Full article
(This article belongs to the Special Issue Machining—Recent Advances, Applications and Challenges)
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Article
A New Cutting Tool Design for Cryogenic Machining of Ti–6Al–4V Titanium Alloy
Materials 2019, 12(3), 477; https://doi.org/10.3390/ma12030477 - 04 Feb 2019
Cited by 14 | Viewed by 1793
Abstract
Titanium alloys are extensively used in aerospace and medical industries. About 15% of modern civil aircrafts are made from titanium alloys. Ti–6Al–4V, the most used titanium alloy, is widely considered a difficult-to-machine material due to short tool life, poor surface integrity, and low [...] Read more.
Titanium alloys are extensively used in aerospace and medical industries. About 15% of modern civil aircrafts are made from titanium alloys. Ti–6Al–4V, the most used titanium alloy, is widely considered a difficult-to-machine material due to short tool life, poor surface integrity, and low productivity during machining. Cryogenic machining using liquid nitrogen (LN2) has shown promising advantages in increasing tool life and material removal rate whilst improving surface integrity. However, to date, there is no study on cutting tool geometry and its performance relationship in cryogenic machining. This paper presents the first investigation on various cutting tool geometries for cryogenic end milling of Ti–6Al–4V alloy. The investigations revealed that a 14° rake angle and a 10° primary clearance angle are the most suitable geometries for cryogenic machining. The effect of cutting speed on tool life was also studied. The analysis indicated that 110 m/min cutting speed yields the longest tool life of 91 min whilst allowing for up to 83% increased productivity when machining Ti–6Al–4V. Overall the research shows significant impact in machining performance of Ti–6Al–4V with much higher material removal rate. Full article
(This article belongs to the Special Issue Machining—Recent Advances, Applications and Challenges)
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Article
Modeling and Optimization of Fractal Dimension in Wire Electrical Discharge Machining of EN 31 Steel Using the ANN-GA Approach
Materials 2019, 12(3), 454; https://doi.org/10.3390/ma12030454 - 01 Feb 2019
Cited by 13 | Viewed by 1549
Abstract
To achieve enhanced surface characteristics in wire electrical discharge machining (WEDM), the present work reports the use of an artificial neural network (ANN) combined with a genetic algorithm (GA) for the correlation and optimization of WEDM process parameters. The parameters considered are the [...] Read more.
To achieve enhanced surface characteristics in wire electrical discharge machining (WEDM), the present work reports the use of an artificial neural network (ANN) combined with a genetic algorithm (GA) for the correlation and optimization of WEDM process parameters. The parameters considered are the discharge current, voltage, pulse-on time, and pulse-off time, while the response is fractal dimension. The usefulness of fractal dimension to characterize a machined surface lies in the fact that it is independent of the resolution of the instrument or length scales. Experiments were carried out based on a rotatable central composite design. A feed-forward ANN architecture trained using the Levenberg-Marquardt (L-M) back-propagation algorithm has been used to model the complex relationship between WEDM process parameters and fractal dimension. After several trials, 4-3-3-1 neural network architecture has been found to predict the fractal dimension with reasonable accuracy, having an overall R-value of 0.97. Furthermore, the genetic algorithm (GA) has been used to predict the optimal combination of machining parameters to achieve a higher fractal dimension. The predicted optimal condition is seen to be in close agreement with experimental results. Scanning electron micrography of the machined surface reveals that the combined ANN-GA method can significantly improve the surface texture produced from WEDM by reducing the formation of re-solidified globules. Full article
(This article belongs to the Special Issue Machining—Recent Advances, Applications and Challenges)
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Article
Hybrid Composite-Metal Stack Drilling with Different Minimum Quantity Lubrication Levels
Materials 2019, 12(3), 448; https://doi.org/10.3390/ma12030448 - 01 Feb 2019
Cited by 10 | Viewed by 1335
Abstract
Hybrid stack drilling is a very common operation used in the assembly of high-added-value components, which combines the use of composite materials and metallic alloys. This process entails the complexity of machining very dissimilar materials, simultaneously, on account of the interactions that are [...] Read more.
Hybrid stack drilling is a very common operation used in the assembly of high-added-value components, which combines the use of composite materials and metallic alloys. This process entails the complexity of machining very dissimilar materials, simultaneously, on account of the interactions that are produced between them, during machining. This study analyzed the influence of Minimum Quantity Lubrication (MQL) on the performance of diamond-coated carbide tools when drilling Ti/carbon fiber reinforced plastics (CFRP)/Ti stacks. The main wear mechanism observed was diamond-coating detachment, followed by fragile breaks in the main cutting-edge. The tests done with the lower lubrication levels have shown an important adhesion of titanium (mainly on the secondary cutting-edge) and a higher friction between the tool and the workpiece, producing higher temperatures on the cutting region and a thermal softening effect on the workpiece. These phenomena affect the evolution of cutting power consumption with tool wear in the titanium layer. Regarding the quality of the test specimen, no significant differences were observed between the lubrication levels tested. Full article
(This article belongs to the Special Issue Machining—Recent Advances, Applications and Challenges)
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Article
Predictive Modeling of Machining Temperatures with Force–Temperature Correlation Using Cutting Mechanics and Constitutive Relation
Materials 2019, 12(2), 284; https://doi.org/10.3390/ma12020284 - 16 Jan 2019
Cited by 43 | Viewed by 2326
Abstract
Elevated temperature in the machining process is detrimental to cutting tools—a result of the effect of thermal softening and material diffusion. Material diffusion also deteriorates the quality of the machined part. Measuring or predicting machining temperatures is important for the optimization of the [...] Read more.
Elevated temperature in the machining process is detrimental to cutting tools—a result of the effect of thermal softening and material diffusion. Material diffusion also deteriorates the quality of the machined part. Measuring or predicting machining temperatures is important for the optimization of the machining process, but experimental temperature measurement is difficult and inconvenient because of the complex contact phenomena between tools and workpieces, and because of restricted accessibility during the machining process. This paper presents an original analytical model for fast prediction of machining temperatures at two deformation zones in orthogonal cutting, namely the primary shear zone and the tool–chip interface. Temperatures were predicted based on a correlation between force and temperature using the mechanics of the cutting process and material constitutive relation. Minimization of the differences between calculated material flow stresses using a mechanics model and a constitutive model yielded an estimate of machining temperatures. Experimental forces, cutting condition parameters, and constitutive model constants were inputs, while machining forces were easily measurable by a piezoelectric dynamometer. Machining temperatures of AISI 1045 steel were predicted under various cutting conditions to demonstrate the predictive capability of each presented model. Close agreements were observed by verifying them against documented values in the literature. The influence of model inputs and computational efficiency were further investigated. The presented model has high computational efficiency that allows real-time prediction and low experimental complexity, considering the easily measurable input variables. Full article
(This article belongs to the Special Issue Machining—Recent Advances, Applications and Challenges)
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Article
A Study on the Optimal Machining Parameters of the Induction Assisted Milling with Inconel 718
Materials 2019, 12(2), 233; https://doi.org/10.3390/ma12020233 - 11 Jan 2019
Cited by 12 | Viewed by 1745
Abstract
This paper focuses on an analysis of tool wear and optimum machining parameter in the induction assisted milling of Inconel 718 using high heat coated carbide and uncoated carbide tools. Thermally assisted machining is an effective machining method for difficult-to-cut materials such as [...] Read more.
This paper focuses on an analysis of tool wear and optimum machining parameter in the induction assisted milling of Inconel 718 using high heat coated carbide and uncoated carbide tools. Thermally assisted machining is an effective machining method for difficult-to-cut materials such as nickel-based superalloy, titanium alloy, etc. Thermally assisted machining is a method of softening the workpiece by preheating using a heat source, such as a laser, plasma or induction heating. Induction assisted milling is a type of thermally assisted machining; induction preheating uses eddy-currents and magnetic force. Induction assisted milling has the advantages of being eco-friendly and economical. Additionally, the preheating temperature can be easily controlled. In this study, the Taguchi method is used to obtain the major parameters for the analysis of cutting force, surface roughness and tool wear of coated and uncoated tools under various machining conditions. Before machining experiments, a finite element analysis is performed to select the effective depth of the cut. The S/N ratio and ANOVA of the cutting force, surface roughness and tool wear are analyzed, and the response optimization method is used to suggest the optimal machining parameters. Full article
(This article belongs to the Special Issue Machining—Recent Advances, Applications and Challenges)
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Article
One-Shot Drilling Analysis of Stack CFRP/UNS A92024 Bonding by Adhesive
Materials 2019, 12(1), 160; https://doi.org/10.3390/ma12010160 - 06 Jan 2019
Cited by 7 | Viewed by 1678
Abstract
The use of adhesive layers can improve the properties and reduce the defects produced in the interfaces. This provides adherence to the structure, adapting the joining surfaces and avoiding spaces between the layers. However, the presence of the adhesive can potentiate the defects [...] Read more.
The use of adhesive layers can improve the properties and reduce the defects produced in the interfaces. This provides adherence to the structure, adapting the joining surfaces and avoiding spaces between the layers. However, the presence of the adhesive can potentiate the defects caused during drilling. In turn, a loss of adhesive in the interface can occur during machining affecting the final structure. This work has followed a conventional OSD strategy in CFRP and UNS A92024 aluminium sheet stacking with adhesive. A series of dry drilling tests have been developed with different cutting conditions and new noncoated WC-Co helical cutting tools. Analysis of Variance (ANOVA) statistical analyses and surface response models have been applied to determine the mechanical behaviour in the holes. For this purpose, the dimensional deviation, surface quality, and adhesive loss in the interface in relation to the number of holes have been considered. A combination of cutting parameters that minimizes the evaluated defects has been found. Diametric deviations and surface qualities below 2% and 3.5 µm have been measured in the materials that make up the stack with cutting speeds higher than 140 m/min and feed rates between 200 and 250 mm/min. However, the greatest adhesive losses occur at high cutting speeds. Full article
(This article belongs to the Special Issue Machining—Recent Advances, Applications and Challenges)
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Article
Research on High Performance Milling of Engineering Ceramics from the Perspective of Cutting Variables Setting
Materials 2019, 12(1), 122; https://doi.org/10.3390/ma12010122 - 02 Jan 2019
Cited by 2 | Viewed by 1423
Abstract
The setting of cutting variables for precision milling of ceramics is important to both the machined surface quality and material removal rate (MRR). This work specifically aims at the performance of corner radius PCD (polycrystalline diamond) end mill in precision milling of zirconia [...] Read more.
The setting of cutting variables for precision milling of ceramics is important to both the machined surface quality and material removal rate (MRR). This work specifically aims at the performance of corner radius PCD (polycrystalline diamond) end mill in precision milling of zirconia ceramics with relatively big cutting parameters. The characteristics of the cutting zone in precision milling ceramics with corner radius end mill are analyzed. The relationships between the maximum uncut chip thickness (hmax) and the milling parameters including feed per tooth (fz), axial depth of cut (ap) and tool corner radius (rε) are discussed. Precision milling experiments with exploratory milling parameters that cause uncut chip thickness larger than the critical value were carried out. The material removal mechanism was also analyzed. According to the results, it is advisable to increase fz appropriately during precision milling ZrO2 ceramics with corner radius end mill. There is still a chance to obtain ductile processed surface, as long as the brittle failure area is controlled within a certain range. The appropriate increasing of ap, not only can prevent the brittle damage from affecting the machined surface, but also could increase the MRR. The milling force increases with increasing MRR, but the surface roughness can still be stabilized within a certain range. Full article
(This article belongs to the Special Issue Machining—Recent Advances, Applications and Challenges)
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Article
Optimum Selection of Variable Pitch for Chatter Suppression in Face Milling Operations
Materials 2019, 12(1), 112; https://doi.org/10.3390/ma12010112 - 31 Dec 2018
Cited by 17 | Viewed by 1843
Abstract
Cutting capacity can be seriously limited in heavy duty face milling processes due to self-excited structural vibrations. Special geometry tools and, specifically, variable pitch milling tools have been extensively used in aeronautic applications with the purpose of removing these detrimental chatter vibrations, where [...] Read more.
Cutting capacity can be seriously limited in heavy duty face milling processes due to self-excited structural vibrations. Special geometry tools and, specifically, variable pitch milling tools have been extensively used in aeronautic applications with the purpose of removing these detrimental chatter vibrations, where high frequency chatter related to slender tools or thin walls limits productivity. However, the application of this technique in heavy duty face milling operations has not been thoroughly explored. In this paper, a method for the definition of the optimum angles between inserts is presented, based on the optimum pitch angle and the stabilizability diagrams. These diagrams are obtained through the brute force (BF) iterative method, which basically consists of an iterative maximization of the stability by using the semidiscretization method. From the observed results, hints for the selection of the optimum pitch pattern and the optimum values of the angles between inserts are presented. A practical application is implemented and the cutting performance when using an optimized variable pitch tool is assessed. It is concluded that with an optimum selection of the pitch, the material removal rate can be improved up to three times. Finally, the existence of two more different stability lobe families related to the saddle-node and flip type stability losses is demonstrated. Full article
(This article belongs to the Special Issue Machining—Recent Advances, Applications and Challenges)
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Article
Theoretical and Experimental Investigation of Surface Topography Generation in Slow Tool Servo Ultra-Precision Machining of Freeform Surfaces
Materials 2018, 11(12), 2566; https://doi.org/10.3390/ma11122566 - 17 Dec 2018
Cited by 10 | Viewed by 1588
Abstract
Freeform surfaces are featured with superior optical and physical properties and are widely adopted in advanced optical systems. Slow tool servo (STS) ultra-precision machining is an enabling manufacturing technology for fabrication of non-rotationally symmetric surfaces. This work presents a theoretical and experimental study [...] Read more.
Freeform surfaces are featured with superior optical and physical properties and are widely adopted in advanced optical systems. Slow tool servo (STS) ultra-precision machining is an enabling manufacturing technology for fabrication of non-rotationally symmetric surfaces. This work presents a theoretical and experimental study of surface topography generation in STS machining of freeform surfaces. To achieve the nanometric surface topography, a systematic approach for tool path generation was investigated, including tool path planning, tool geometry selection, and tool radius compensation. The tool radius compensation is performed only in one direction to ensure no high frequency motion is imposed on the non-dynamic axis. The development of the surface generation simulation allows the prediction of the surface topography under various tool and machining variables. Furthermore, it provides an important means for better understanding the surface generation mechanism without the need for costly trial and error tests. Machining and measurement experiments of a sinusoidal grid and microlens array sample validated the proposed tool path generation and demonstrated the effectiveness of the STS machining process to fabricate freeform surfaces with nanometric topography. The measurement results also show a uniform topography distribution over the entire surface and agree well with the simulated results. Full article
(This article belongs to the Special Issue Machining—Recent Advances, Applications and Challenges)
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Article
Experimental Determination of Residual Stresses Generated by Single Point Incremental Forming of AlSi10Mg Sheets Produced Using SLM Additive Manufacturing Process
Materials 2018, 11(12), 2542; https://doi.org/10.3390/ma11122542 - 13 Dec 2018
Cited by 9 | Viewed by 2319
Abstract
This paper focuses on investigating the residual stress values associated with a part fabricated by Selective Laser Melting technology (SLM) when this is subjected further to forces on single point incremental forming (SPIF) operation of variable wall angle. The residual stresses induced by [...] Read more.
This paper focuses on investigating the residual stress values associated with a part fabricated by Selective Laser Melting technology (SLM) when this is subjected further to forces on single point incremental forming (SPIF) operation of variable wall angle. The residual stresses induced by the SLM manufacturing process on the fabricated AlSi10Mg metallic sheets, as well as those produced during their forming SPIF operation were determined by X-ray diffraction (XRD) measurements. Significant residual stress levels of variation, positive or negative, along the metallic sample were observed because of the bending effects induced by the SPIF processes. It is also shown how the wall thickness varies along the additive manufactured SPIFed part as well as the morphology of the melting pools as a function of the deformation depth. Full article
(This article belongs to the Special Issue Machining—Recent Advances, Applications and Challenges)
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Article
Drilling Process in γ-TiAl Intermetallic Alloys
Materials 2018, 11(12), 2379; https://doi.org/10.3390/ma11122379 - 26 Nov 2018
Cited by 10 | Viewed by 1526
Abstract
Gamma titanium aluminides (γ-TiAl) present an excellent behavior under high temperature conditions, being a feasible alternative to nickel-based superalloy components in the aeroengine sector. However, considered as a difficult to cut material, process cutting parameters require special study to guarantee component quality. In [...] Read more.
Gamma titanium aluminides (γ-TiAl) present an excellent behavior under high temperature conditions, being a feasible alternative to nickel-based superalloy components in the aeroengine sector. However, considered as a difficult to cut material, process cutting parameters require special study to guarantee component quality. In this work, a developed drilling mechanistic model is a useful tool in order to predict drilling force (Fz) and torque (Tc) for optimal drilling conditions. The model is a helping tool to select operational parameters for the material to cut by providing the programmer predicted drilling forces (Fz) and torque (Tc) values. This will allow the avoidance of operational parameters that will cause excessively high force and torque values that could damage quality. The model is validated for three types of Gamma-TiAl alloys. Integral hard metal end-drilling tools and different cutting parameters (feeds and cutting speeds) are tested for three different sized holes for each alloy. Full article
(This article belongs to the Special Issue Machining—Recent Advances, Applications and Challenges)
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Article
Multi-Objective Optimization for Grinding of AISI D2 Steel with Al2O3 Wheel under MQL
Materials 2018, 11(11), 2269; https://doi.org/10.3390/ma11112269 - 13 Nov 2018
Cited by 34 | Viewed by 2223
Abstract
In the present study, the machinability indices of surface grinding of AISI D2 steel under dry, flood cooling, and minimum quantity lubrication (MQL) conditions are compared. The comparison was confined within three responses, namely, the surface quality, surface temperature, and normal force. For [...] Read more.
In the present study, the machinability indices of surface grinding of AISI D2 steel under dry, flood cooling, and minimum quantity lubrication (MQL) conditions are compared. The comparison was confined within three responses, namely, the surface quality, surface temperature, and normal force. For deeper insight, the surface topography of MQL-assisted ground surface was analyzed too. Furthermore, the statistical analysis of variance (ANOVA) was employed to extract the major influencing factors on the above-mentioned responses. Apart from this, the multi-objective optimization by Grey–Taguchi method was performed to suggest the best parameter settings for system-wide optimal performance. The central composite experimental design plan was adopted to orient the inputs wherein the inclusion of MQL flow rate as an input adds addition novelty to this study. The mathematical models were formulated using Response Surface Methodology (RSM). It was found that the developed models are statistically significant, with optimum conditions of depth of cut of 15 µm, table speed of 3 m/min, cutting speed 25 m/min, and MQL flow rate 250 mL/h. It was also found that MQL outperformed the dry as well as wet condition in surface grinding due to its effective penetration ability and improved heat dissipation property. Full article
(This article belongs to the Special Issue Machining—Recent Advances, Applications and Challenges)
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Article
Fast Analytic Simulation for Multi-Laser Heating of Sheet Metal in GPU
Materials 2018, 11(11), 2078; https://doi.org/10.3390/ma11112078 - 24 Oct 2018
Cited by 4 | Viewed by 2037
Abstract
Interactive multi-beam laser machining simulation is crucial in the context of tool path planning and optimization of laser machining parameters. Current simulation approaches for heat transfer analysis (1) rely on numerical Finite Element methods (or any of its variants), non-suitable for interactive applications; [...] Read more.
Interactive multi-beam laser machining simulation is crucial in the context of tool path planning and optimization of laser machining parameters. Current simulation approaches for heat transfer analysis (1) rely on numerical Finite Element methods (or any of its variants), non-suitable for interactive applications; and (2) require the multiple laser beams to be completely synchronized in trajectories, parameters and time frames. To overcome this limitation, this manuscript presents an algorithm for interactive simulation of the transient temperature field on the sheet metal. Contrary to standard numerical methods, our algorithm is based on an analytic solution in the frequency domain, allowing arbitrary time/space discretizations without loss of precision and non-monotonic retrieval of the temperature history. In addition, the method allows complete asynchronous laser beams with independent trajectories, parameters and time frames. Our implementation in a GPU device allows simulations at interactive rates even for a large amount of simultaneous laser beams. The presented method is already integrated into an interactive simulation environment for sheet cutting. Ongoing work addresses thermal stress coupling and laser ablation. Full article
(This article belongs to the Special Issue Machining—Recent Advances, Applications and Challenges)
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Article
Using the Machine Vision Method to Develop an On-machine Insert Condition Monitoring System for Computer Numerical Control Turning Machine Tools
Materials 2018, 11(10), 1977; https://doi.org/10.3390/ma11101977 - 14 Oct 2018
Cited by 14 | Viewed by 1557
Abstract
This study uses the machine vision method to develop an on-machine turning tool insert condition monitoring system for tool condition monitoring in the cutting processes of computer numerical control (CNC) machines. The system can identify four external turning tool insert conditions, namely fracture, [...] Read more.
This study uses the machine vision method to develop an on-machine turning tool insert condition monitoring system for tool condition monitoring in the cutting processes of computer numerical control (CNC) machines. The system can identify four external turning tool insert conditions, namely fracture, built-up edge (BUE), chipping, and flank wear. This study also designs a visual inspection system for the tip of an insert using the surrounding light source and fill-light, which can be mounted on the turning machine tool, to overcome the environmental effect on the captured insert image for subsequent image processing. During image capture, the intensity of the light source changes to ensure that the test insert has appropriate surface and tip features. This study implements outer profile construction, insert status region capture, insert wear region judgment, and calculation to monitor and classify insert conditions. The insert image is then trimmed according to the vertical flank, horizontal blade, and vertical blade lines. The image of the insert-wear region is captured to monitor flank or chipping wear using grayscale value histogram. The amount of wear is calculated using the wear region image as the evaluation index to judge normal wear or over-wear conditions. On-machine insert condition monitoring is tested to confirm that the proposed system can judge insert fracture, BUE, chipping, and wear. The results demonstrate that the standard deviation of the chipping and amount of wear accounts for 0.67% and 0.62%, of the average value, respectively, thus confirming the stability of system operation. Full article
(This article belongs to the Special Issue Machining—Recent Advances, Applications and Challenges)
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Article
Comparison of Flank Super Abrasive Machining vs. Flank Milling on Inconel® 718 Surfaces
Materials 2018, 11(9), 1638; https://doi.org/10.3390/ma11091638 - 06 Sep 2018
Cited by 12 | Viewed by 2220
Abstract
Thermoresistant superalloys present many challenges in terms of machinability, which leads to finding new alternatives to conventional manufacturing processes. In order to face this issue, super abrasive machining (SAM) is presented as a solution due to the fact that it combines the advantages [...] Read more.
Thermoresistant superalloys present many challenges in terms of machinability, which leads to finding new alternatives to conventional manufacturing processes. In order to face this issue, super abrasive machining (SAM) is presented as a solution due to the fact that it combines the advantages of the use of grinding tools with milling feed rates. This technique is commonly used for finishing operations. Nevertheless, this work analyses the feasibility of this technique for roughing operations. In order to verify the adequacy of this new technique as an alternative to conventional process for roughing operations, five slots were performed in Inconel® 718 using flank SAM and flank milling. The results showed that flank SAM implies a suitable and controllable process to improve the manufacture of high added value components made by nickel-based superalloys in terms of roughness, microhardness, white layer, and residual stresses. Full article
(This article belongs to the Special Issue Machining—Recent Advances, Applications and Challenges)
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Article
Experimental Parametric Model for Adhesion Wear Measurements in the Dry Turning of an AA2024 Alloy
Materials 2018, 11(9), 1598; https://doi.org/10.3390/ma11091598 - 03 Sep 2018
Cited by 7 | Viewed by 1603
Abstract
Adhesion wear is the main wear mechanism in the dry turning of aluminium alloys. This type of wear produces an adhesion of the machining material on the cutting tool, decreasing the final surface quality of the machining parts and making it more difficult [...] Read more.
Adhesion wear is the main wear mechanism in the dry turning of aluminium alloys. This type of wear produces an adhesion of the machining material on the cutting tool, decreasing the final surface quality of the machining parts and making it more difficult to maintain industrial tolerances. This work studies the influence of the cutting parameters on the volume of material adhered to the cutting tool surface for dry machining of AA2024 (Al-Cu). For that purpose, a specific methodology based on the automatic image processing method that can obtain the area and the thickness of the adhered material has been designed. This methodology has been verified with the results obtained through 3D analysis techniques and compared with the adhered volume. The results provided experimental parametric models for this wear mechanism. These models are analytic approximations of experimental data. The feed rate mainly results in low cutting speed, while low depths of cut presents a different behaviour due to the low contact pressure. The unstable behaviour of aluminium adhesion on the cutting tool produces a high variability of results. This continuous change introduces variation in the process caused by the continuous change of the cutting tool geometry. Full article
(This article belongs to the Special Issue Machining—Recent Advances, Applications and Challenges)
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Article
Investigation of Cutting Temperature during Turning Inconel 718 with (Ti,Al)N PVD Coated Cemented Carbide Tools
Materials 2018, 11(8), 1281; https://doi.org/10.3390/ma11081281 - 25 Jul 2018
Cited by 14 | Viewed by 1909
Abstract
Physical Vapor Deposition (PVD) Ti1−xAlxN coated cemented carbide tools are commonly used to cut difficult-to-machine super alloy of Inconel 718. The Al concentration x of Ti1−xAlxN coating can affect the coating microstructure, mechanical [...] Read more.
Physical Vapor Deposition (PVD) Ti1−xAlxN coated cemented carbide tools are commonly used to cut difficult-to-machine super alloy of Inconel 718. The Al concentration x of Ti1−xAlxN coating can affect the coating microstructure, mechanical and thermo-physical properties of Ti1−xAlxN coating, which affects the cutting temperature in the machining process. Cutting temperature has great influence on the tool life and the machined surface quality. In this study, the influences of PVD (Ti,Al)N coated cemented carbide tools on the cutting temperature were analyzed. Firstly, the microstructures of PVD Ti0.41Al0.59N and Ti0.55Al0.45N coatings were inspected. The increase of Al concentration x enhanced the crystallinity of PVD Ti1−xAlxN coatings without epitaxy growth of TiAlN crystals. Secondly, the mechanical and thermo-physical properties of PVD Ti0.41Al0.59N and Ti0.55Al0.45N coated tools were analyzed. The pinning effects of coating increased with the increasing of Al concentration x, which can decrease the friction coefficient between the PVD Ti1−xAlxN coated cemented carbide tools and the Inconel 718 material. The coating hardness and thermal conductivity of Ti1−xAlxN coatings increased with the increase of Al concentration x. Thirdly, the influences of PVD Ti1−xAlxN coated tools on the cutting temperature in turning Inconel 718 were analyzed by mathematical analysis modelling and Lagrange simulation methods. Compared with the uncoated tools, PVD Ti0.41Al0.59N coated tools decreased the heat generation as well as the tool temperature to reduce the thermal stress generated within the tools. Lastly, the influences of Ti1−xAlxN coatings on surface morphologies of the tool rake faces were analyzed. The conclusions can reveal the influences of PVD Ti1−xAlxN coatings on cutting temperature, which can provide guidance in the proper choice of Al concentration x for PVD Ti1−xAlxN coated tools in turning Inconel 718. Full article
(This article belongs to the Special Issue Machining—Recent Advances, Applications and Challenges)
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Article
Numerical Simulation and Experimental Investigation of Cold-Rolled Steel Cutting
Materials 2018, 11(7), 1263; https://doi.org/10.3390/ma11071263 - 23 Jul 2018
Cited by 9 | Viewed by 2015
Abstract
The paper presents results of the investigations on numerical computations and experimental verification concerning the influence of selected parameters of the cutting process on the stress state in bundles of cold-rolled steel sheets being cut using a guillotine. The physical model and, corresponding [...] Read more.
The paper presents results of the investigations on numerical computations and experimental verification concerning the influence of selected parameters of the cutting process on the stress state in bundles of cold-rolled steel sheets being cut using a guillotine. The physical model and, corresponding to it, the mathematical model of the analysed steel sheet being cut were elaborated. In this work, the relationship between the cutting depth and the values of reduced Huber–Mises stresses as well as the mechanism of sheet separation were presented. The numerical simulations were conducted by means of the finite element method and the computer system LS-DYNA. The results of numerical computations are juxtaposed as graphs, tables, and contour maps of sheet deformation as well as reduced Huber–Mises strains and stresses for selected time instants. The microscopic tests revealed two distinct zones in the fracture areas. The ductile and brittle zones are separated at the depth of ca. 1/3 thickness of the cut steel sheet. Full article
(This article belongs to the Special Issue Machining—Recent Advances, Applications and Challenges)
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Article
A Consistent Procedure Using Response Surface Methodology to Identify Stiffness Properties of Connections in Machine Tools
Materials 2018, 11(7), 1220; https://doi.org/10.3390/ma11071220 - 16 Jul 2018
Cited by 11 | Viewed by 1414
Abstract
Accurate finite element models of mechanical systems are fundamental resources to perform structural analyses at the design stage. However, uncertainties in material properties, boundary conditions, or connections give rise to discrepancies between the real and predicted dynamic characteristics. Therefore, it is necessary to [...] Read more.
Accurate finite element models of mechanical systems are fundamental resources to perform structural analyses at the design stage. However, uncertainties in material properties, boundary conditions, or connections give rise to discrepancies between the real and predicted dynamic characteristics. Therefore, it is necessary to improve these models in order to achieve a better fit. This paper presents a systematic three-step procedure to update the finite element (FE) models of machine tools with numerous uncertainties in connections, which integrates statistical, numerical, and experimental techniques. The first step is the gradual application of fractional factorial designs, followed by an analysis of the variance to determine the significant variables that affect each dynamic response. Then, quadratic response surface meta-models, including only significant terms, which relate the design parameters to the modal responses are obtained. Finally, the values of the updated design variables are identified using the previous regression equations and experimental modal data. This work demonstrates that the integrated procedure gives rise to FE models whose dynamic responses closely agree with the experimental measurements, despite the large number of uncertainties, and at an acceptable computational cost. Full article
(This article belongs to the Special Issue Machining—Recent Advances, Applications and Challenges)
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Article
Effects of Cutting Edge Microgeometry on Residual Stress in Orthogonal Cutting of Inconel 718 by FEM
Materials 2018, 11(6), 1015; https://doi.org/10.3390/ma11061015 - 14 Jun 2018
Cited by 21 | Viewed by 2040
Abstract
Service performance of components such as fatigue life are dramatically influenced by the machined surface and subsurface residual stresses. This paper aims at achieving a better understanding of the influence of cutting edge microgeometry on machined surface residual stresses during orthogonal dry cutting [...] Read more.
Service performance of components such as fatigue life are dramatically influenced by the machined surface and subsurface residual stresses. This paper aims at achieving a better understanding of the influence of cutting edge microgeometry on machined surface residual stresses during orthogonal dry cutting of Inconel 718. Numerical and experimental investigations have been conducted in this research. The cutting edge microgeometry factors of average cutting edge radius S¯, form-factor K, and chamfer were investigated. An increasing trend for the magnitudes of both tensile and compressive residual stresses was observed by using larger S¯ or introducing a chamfer on the cutting edges. The ploughing depth has been predicted based on the stagnation zone. The increase of ploughing depth means that more material was ironed on the workpiece subsurface, which resulted in an increase in the compressive residual stress. The thermal loads were leading factors that affected the surface tensile residual stress. For the unsymmetrical honed cutting edge with K = 2, the friction between tool and workpiece and tensile residual stress tended to be high, while for the unsymmetrical honed cutting edge with K = 0.5, the high ploughing depth led to a higher compressive residual stress. This paper provides guidance for regulating machine-induced residual stress by edge preparation. Full article
(This article belongs to the Special Issue Machining—Recent Advances, Applications and Challenges)
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Article
Influence of the Regime of Electropulsing-Assisted Machining on the Plastic Deformation of the Layer Being Cut
Materials 2018, 11(6), 886; https://doi.org/10.3390/ma11060886 - 25 May 2018
Cited by 15 | Viewed by 1872
Abstract
In this article, the influence of electropulsing on the machinability of steel S235 and aluminium 6060 has been studied during conventional and electropulsing-assisted turning processes. The machinability indices such as chip compression ratio ξ , shear plane angle ϕ and specific cutting energy [...] Read more.
In this article, the influence of electropulsing on the machinability of steel S235 and aluminium 6060 has been studied during conventional and electropulsing-assisted turning processes. The machinability indices such as chip compression ratio ξ , shear plane angle ϕ and specific cutting energy (SCE) are investigated by using different cutting parameters such as cutting speed, cutting feed and depth of cut during electrically-assisted turning process. The results and analysis of this work indicated that the electrically-assisted turning process improves the machinability of steel S235, whereas the machinability of aluminium 6060 gets worse. Finally, due to electropluses (EPs), the chip compression ratio ξ increases with the increase in cutting speed during turning of aluminium 6060 and the SCE decreases during turning of steel S235. Full article
(This article belongs to the Special Issue Machining—Recent Advances, Applications and Challenges)
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Article
ANN Surface Roughness Optimization of AZ61 Magnesium Alloy Finish Turning: Minimum Machining Times at Prime Machining Costs
Materials 2018, 11(5), 808; https://doi.org/10.3390/ma11050808 - 16 May 2018
Cited by 37 | Viewed by 3119
Abstract
Magnesium alloys are widely used in aerospace vehicles and modern cars, due to their rapid machinability at high cutting speeds. A novel Edgeworth–Pareto optimization of an artificial neural network (ANN) is presented in this paper for surface roughness (Ra) prediction of [...] Read more.
Magnesium alloys are widely used in aerospace vehicles and modern cars, due to their rapid machinability at high cutting speeds. A novel Edgeworth–Pareto optimization of an artificial neural network (ANN) is presented in this paper for surface roughness (Ra) prediction of one component in computer numerical control (CNC) turning over minimal machining time (Tm) and at prime machining costs (C). An ANN is built in the Matlab programming environment, based on a 4-12-3 multi-layer perceptron (MLP), to predict Ra, Tm, and C, in relation to cutting speed, vc, depth of cut, ap, and feed per revolution, fr. For the first time, a profile of an AZ61 alloy workpiece after finish turning is constructed using an ANN for the range of experimental values vc, ap, and fr. The global minimum length of a three-dimensional estimation vector was defined with the following coordinates: Ra = 0.087 μm, Tm = 0.358 min/cm3, C = $8.2973. Likewise, the corresponding finish-turning parameters were also estimated: cutting speed vc = 250 m/min, cutting depth ap = 1.0 mm, and feed per revolution fr = 0.08 mm/rev. The ANN model achieved a reliable prediction accuracy of ±1.35% for surface roughness. Full article
(This article belongs to the Special Issue Machining—Recent Advances, Applications and Challenges)
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Article
The Effect of Weld Reinforcement and Post-Welding Cooling Cycles on Fatigue Strength of Butt-Welded Joints under Cyclic Tensile Loading
Materials 2018, 11(4), 594; https://doi.org/10.3390/ma11040594 - 12 Apr 2018
Cited by 6 | Viewed by 2742
Abstract
This research deals with the fatigue behavior of butt-welded joints, by considering the geometry and post-welding cooling cycles, as a result of cooling in quiet air and immersed in water. ASTM A-36 HR structural steel was used as the base metal for the [...] Read more.
This research deals with the fatigue behavior of butt-welded joints, by considering the geometry and post-welding cooling cycles, as a result of cooling in quiet air and immersed in water. ASTM A-36 HR structural steel was used as the base metal for the shielded metal arc welding (SMAW) process with welding electrode E6013. The welding reinforcement was 1 mm and 3 mm, respectively; axial fatigue tests were carried out to determine the life and behavior in cracks propagation of the tested welded joints, mechanical characterization tests of properties in welded joints such as microhardness, Charpy impact test and metallographic analysis were carried out. The latter were used as input for the analysis by finite elements which influence the initiation and propagation of cracks and the evaluation of stress intensity factors (SIF). The latter led to obtaining the crack propagation rate and the geometric factor. The tested specimens were analyzed, by taking photographs of the cracks at its beginning in order to make a count of the marks at the origin of the crack. From the results obtained and the marks count, the fatigue crack growth rate and the influence of the cooling media on the life of the welded joint are validated, according to the experimental results. It can be concluded that the welded joints with a higher weld reinforcement have a shorter fatigue life. This is due to the stress concentration that occurs in the vicinity of the weld toe. Full article
(This article belongs to the Special Issue Machining—Recent Advances, Applications and Challenges)
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Article
Characteristics of the Arcing Plasma Formation Effect in Spark-Assisted Chemical Engraving of Glass, Based on Machine Vision
Materials 2018, 11(4), 470; https://doi.org/10.3390/ma11040470 - 22 Mar 2018
Cited by 6 | Viewed by 1926
Abstract
Spark-assisted chemical engraving (SACE) is a non-traditional machining technology that is used to machine electrically non-conducting materials including glass, ceramics, and quartz. The processing accuracy, machining efficiency, and reproducibility are the key factors in the SACE process. In the present study, a machine [...] Read more.
Spark-assisted chemical engraving (SACE) is a non-traditional machining technology that is used to machine electrically non-conducting materials including glass, ceramics, and quartz. The processing accuracy, machining efficiency, and reproducibility are the key factors in the SACE process. In the present study, a machine vision method is applied to monitor and estimate the status of a SACE-drilled hole in quartz glass. During the machining of quartz glass, the spring-fed tool electrode was pre-pressured on the quartz glass surface to feed the electrode that was in contact with the machining surface of the quartz glass. In situ image acquisition and analysis of the SACE drilling processes were used to analyze the captured image of the state of the spark discharge at the tip and sidewall of the electrode. The results indicated an association between the accumulative size of the SACE-induced spark area and deepness of the hole. The results indicated that the evaluated depths of the SACE-machined holes were a proportional function of the accumulative spark size with a high degree of correlation. The study proposes an innovative computer vision-based method to estimate the deepness and status of SACE-drilled holes in real time. Full article
(This article belongs to the Special Issue Machining—Recent Advances, Applications and Challenges)
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Article
On the Cutting Performance of Segmented Diamond Blades when Dry-Cutting Concrete
Materials 2018, 11(2), 264; https://doi.org/10.3390/ma11020264 - 09 Feb 2018
Cited by 16 | Viewed by 2624
Abstract
The objective of the present study is to analyze and compare the cutting performance of segmented diamond blades when dry-cutting concrete. A cutting criteria is proposed to characterize the wear of the blades by measuring the variation of the external diameter and the [...] Read more.
The objective of the present study is to analyze and compare the cutting performance of segmented diamond blades when dry-cutting concrete. A cutting criteria is proposed to characterize the wear of the blades by measuring the variation of the external diameter and the weight loss of the blade. The results exhibit the cutting blade SB-A, which has twice the density of diamonds and large contact area, exhibits less wear even though the material removal rate is higher compared with the other two cutting blades. Additionally, the surface topography of the different blades is evaluated to examine the impact of wear depending on the surface profile and the distribution of the diamonds in the blade’s matrix. Large number of diamonds pull-out are found in blades type SB-C, which additionally shows the worst wear resistant capability. As a conclusion, the cutting efficiency of the blade is found to be related to the density of embedded diamonds and the type of the surface profile of the cutting blade after reaching the stop criteria. Full article
(This article belongs to the Special Issue Machining—Recent Advances, Applications and Challenges)
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Review

Jump to: Research

Review
Thin-Wall Machining of Light Alloys: A Review of Models and Industrial Approaches
Materials 2019, 12(12), 2012; https://doi.org/10.3390/ma12122012 - 23 Jun 2019
Cited by 18 | Viewed by 1961
Abstract
Thin-wall parts are common in the aeronautical sector. However, their machining presents serious challenges such as vibrations and part deflections. To deal with these challenges, different approaches have been followed in recent years. This work presents the state of the art of thin-wall [...] Read more.
Thin-wall parts are common in the aeronautical sector. However, their machining presents serious challenges such as vibrations and part deflections. To deal with these challenges, different approaches have been followed in recent years. This work presents the state of the art of thin-wall light-alloy machining, analyzing the problems related to each type of thin-wall parts, exposing the causes of both instability and deformation through analytical models, summarizing the computational techniques used, and presenting the solutions proposed by different authors from an industrial point of view. Finally, some further research lines are proposed. Full article
(This article belongs to the Special Issue Machining—Recent Advances, Applications and Challenges)
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