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Roller burnishing technique to achieve isotropic surface topography on cylindrical components made of austempered ductile iron (ADI) casting is presented in this paper. In the last years, ADI casting components are used in many mechanical applications, due to their enhanced mechanical properties. ADI castings are difficult-to-cut materials; therefore, advanced techniques to improve manufacturing productivity are necessary and under research. On the other hand, spiral roughness pattern produced by turning operation is a common source of unconformities in several applications. Turning produces a defined kinematic pattern, similar to a thread. This work presents a theoretical and experimental validation using different burnishing conditions. Roughness and surface topography and surface integrity were checked. Results show that the technique greatly improves surface roughness, and eliminates the kinematic-driven roughness pattern of turning, leading to a more isotropic finishing. A comparison between roller burnishing and ball burnishing is also presented in this paper.

The study of the actual conditions in the discharge gap is a matter of large interest in area of WEDM. It is known that gap width and the presence of electrically conductive debris particles are the dominant factors affecting dielectric breakdown strength. Whereas, little information of that in WEDM is available, probably because of the difficult access to inter-electrode gap, wire vibration, etc. In this work the results of experimental observations of debris composition, morphology and size distribution of particles in WEDM are presented. A device designed to collect water from the working region and a set of WEDM experiments have been proposed. Techniques such as Energy Dispersive X-Ray Fluorescence Spectroscopy, laser diffraction, SEM and TEM have been used to characterize WEDM debris. Results show that debris in the gap is dominated by the presence of Cu-Zn from the wire. The presence of spherical particles in the range 1-20 μm has been confirmed. Histograms of particle volume and amount have been obtained, revealing the presence of massive amount of sub-micron and nanometric particles, most of them oxides of metals coming from the electrodes. The conclusions will be useful for future simulation work about particle movement and electrical fields in the working gap in WEDM.

Electrical discharge machining (EDM) is regarded as the most competitive solution for the machining of high-aspect ratio cavities with strict requirements in surface quality and accuracy. The diversity of applications ranges from the plastic injection mold industry to the manufacturing of turbine components. The cooling holes in vanes and blades and the seal slots in nozzle guide vanes (NGV) are demanding geometries in the aerospace sector usually processed by EDM. The nature of the material removal in EDM, developed without any contact with the part, is considered a major advantage when difficult to manufacture superalloys are involved. However, in high-aspect ratio cavities, due to debris accumulation in the narrow gap, the machining stability is limited with the machining depth. This productivity limitation has been a matter of industrial and scientific research. Considering that the key requirements in aerospace industry are quality and machining performance, this study proposes different machining strategies with the objective of enhancing the productivity of high-aspect ratio slots in Nickel base C1023 super-alloy. Results demonstrate that planetary motion of electrode during the machining process is a promising industrial solution for enhancing machining productivity of the slots machining in the lateral faces of NGV turbine components.

The use of friction drilling technique for hole making in tube dual phase steels was presented in this paper as an alternative to conventional drilling techniques. Due to the higher environmental consciousness growing up in the last years in different industrial environments, the feasibility of the proposed alternative must be analyzed taking into account both, technical and environmental aspects. In order to perform a complete environmental approach for conventional drilling, different lubri-cooling technologies were tested: dry drilling, wet drilling and minimum quantity of lubrication (MQL) drilling using high-oleic sunflower oil. From the technical point of view, results show that using friction drilling, the surface quality obtained was more appropriate. The deformed material provides a perfect base for future threading or joining operations and, moreover, the thermal affected layer observed in micrographies provides a 20 μm hardened layer which reduce surface wear and damages, improving hole zone life. From the environmental point of view, a life cycle assessment (LCA) was carried out for both drilling techniques and different lubricooling environments. Results show that friction drilling presents an ecologic improvement, obtaining a notable reduction in all impact categories. Analyzing both points of view, friction drilling is presented as a solution that improves current drilling processes of metal sheets.

In the current scenario of manufacturing competitiveness, it is a requirement that new technologies are implemented in order to overcome the challenges of achieving component accuracy, high quality, acceptable surface finish, an increase in the production rate, and enhanced product life with a reduced environmental impact. Along with these conventional challenges, the machining of newly developed smart materials, such as shape memory alloys, also require inputs of intelligent machining strategies. Wire electrical discharge machining (WEDM) is one of the non-traditional machining methods which is independent of the mechanical properties of the work sample and is best suited for machining nitinol shape memory alloys. Nano powder-mixed dielectric fluid for the WEDM process is one of the ways of improving the process capabilities. In the current study, Taguchi’s L16 orthogonal array was implemented to perform the experiments. Current, pulse-on time, pulse-off time, and nano-graphene powder concentration were selected as input process parameters, with material removal rate (MRR) and surface roughness (SR) as output machining characteristics for investigations. The heat transfer search (HTS) algorithm was implemented for obtaining optimal combinations of input parameters for MRR and SR. Single objective optimization showed a maximum MRR of 1.55 mm3/s, and minimum SR of 2.68 µm. The Pareto curve was generated which gives the optimal non-dominant solutions.

This paper presents the machining of integral blade rotors (IBRs) made in Ti6Al4V using CO2 as cryogenic cooling. This kind of component is typical in gas turbines, pumps, and other rotary machines. A flank milling technique using polycrystalline diamond (PCD) tools and CO2+minimum quantity lubrication (MQL), denominated CryoMQL, is here presented as an alternative to conventional oil emulsions. The proposed approach implies a balance between technical and environmental issues. Cryogenics makes feasible the use of PCD tools avoiding problems derived from the reactivity of Ti6Al4V alloy with this type of cutting tool, which is directly related to cutting temperature. One key aspect is that CO2 has to be supplied and injected onto the cutting zone avoiding the risks of dry-ice formation, and the consequent clogging of both pipes and nozzles. For this purpose, a new device for CO2 delivery was developed, using gas and liquid CO2 simultaneously.

A new approach of Fiber Enhanced Raman Spectroscopy (FERS) is described within this article based on the use of Hydrogel-Core microstructured Polymer Optical Fibers (HyC-mPOF). The incorporation of the hydrogel only on the core of the Hollow-Core microstructured Polymer Optical Fiber (HC-mPOF) enables to perform FERS measurements in a functionalized matrix, enabling high selectivity Raman measurements. The hydrogel formation was continuously monitored and quantified using a Principal Component Analysis verifying the coherence between the components and the Raman spectrum of the hydrogel. The performed measurements with high and low affinity target molecules prove the feasibility of the presented HyC-mPOF platform. This work was funded in part by the Fondo Europeo de Desarrollo Regional (FEDER), in part by the Ministerio de Ciencia, Innovación y Universidades under projects RTC2019-007194-4, RTI2018-094669-B-C31 and MAT2014-5742 R and in part by the Gobierno Vasco/Eusko Jaurlaritza IT933-16, ELKARTEK KK-2019/00101 (μ4Indust), and ELKARTEK KK-2019/00051 (SMARTRESNAK).

In this work, we detail two types of fabrication processes of four polymer optical fibers doped with lumogen dyes. The fiber preforms have been manufactured with two different methods: extrusion and casting. We have compared the performance of the two types of fibers as luminescent solar concentrators by calculating their optical efficiencies and concentration factors. The obtained results show better performance for those fibers manufactured by the casting process. We have also studied the photostability of the two types of fibers doped with the dye lumogen red under solar light radiation. A high thermal stability of the doped fibers has been observed., This work was funded in part by the Fondo Europeo de Desarrollo Regional (FEDER), in partby the Ministerio de Ciencia, Innovación y Universidades under projects RTC2019-007194-4, RTI2018-094669-B-C31 and MAT2014-5742-R and in part by the GobiernoVasco/Eusko Jaurlaritza IT933-16,ELKARTEK KK-2019/00101 (μ4Indust), and ELKARTEK KK-2019/00051 (SMARTRESNAK

The paper presents blisk blades manufactured by different manufacturing processes. In this sense, different milling trajectories are presented, and, super abrasive machining strategies and EDM technologies are also tested. Machining times, costs and surface finish are analysed in order to determine optimal machining process for blisk manufactured in low machinability materials., RYC-2017-22649

Wire Electrical Discharge Machining (WEDM) is a popular non-conventional machining technology widely used in high-added value sectors such as aerospace, biomedicine, and the automotive industry. Even though the technology is now ready to meet the requirements of the most complex components, certain fundamental aspects related to the discharge process and gap conditions are not yet fully explained and understood. Combining single discharge experiments with numerical simulation represents a good approach for obtaining a deeper insight into the fundamentals of the process. In this paper, a fundamental study of the WEDM through single discharge experiments and numerical simulation is presented. WEDM single discharge experiments are described with the aim of identifying the relation between crater dimensions, discharge gap, and part surface roughness. A thermal transient numerical model of the WEDM process is presented, and correlation with actual industrial material removal rates (MRR) is analyzed. Results from single discharge WEDM experiments show that crater volume is as much as 40% lower when discharging on a rough surface than when the discharge occurs on a flat surface. The proposed thermal numerical model can predict actual removal rates of industrial machines with great accuracy for roughing cuts, deviations with experimental values being below 10%. However, lager deviations have been observed for other WEDM conditions, namely trim cuts, thus confirming the need for future research in this direction.

As an important advanced machining process, in Wire Electrical Discharge Machining (WEDM) certain fundamental issues remain need to be studied in-depth, such as the effect of part surface roughness on heat transfer mechanisms. In the WEDM process, roughing cut wire goes into the workpiece to do the first shaping and in trim cut the wire sweeps on the outer surface to improve the surface roughness. In both of these two cases, the generation of sparks depends on the passing surface roughness. Therefore, with AISI D2 material and brass wire, this paper presents a study of the influence of part surface roughness on heat partition and the radius of the plasma channel in the WEDM process. Through extensive single discharge experiments, it is shown that the removal capacity per discharge can increase if the discharge occurs on a smoother surface. A Finite Element thermal model was then used for inverse fitting of the values of heat partition and radius of the plasma channel. These parameters completely define the characteristics of the heat conduction problem. The results indicate a strong correlation between an increase in heat partition ratio and a decrease in part surface roughness. The values of plasma channel radius show an increase in this value when discharging on rougher surfaces. It means that with the increasing of plasma channel radius, the heat source goes into the workpiece more dispersed. In the case of rougher surface, although the there is more area that affected by the heat source, finally the temperature of most area cannot reach to the melting point and it causes the smaller crater radius and volume, while the metal removal rate decreases. These results contribute towards a more complete understanding of the influence of surface roughness to the spark occurring. This research was funded by the Spanish Ministry of Economy and Competitiveness and the European Regional Development Fund (ERDF) operation program for funding the project “Scientific models and machine-tool advanced sensing techniques for efficient machining of precision components of Low-Pressure Turbines” (DPI2017-82239-P).

This paper presents a study on the influence of the polarization of the pump beam on the emission properties of dye-doped polymer optical fibers. The fiber samples, which are pumped transversely with linearly polarized light, are graded-index polymer optical fibers doped with rhodamine 6G. The variation of the intensity and angular distribution of the output emission are theoretically and experimentally analyzed as the polarization direction of the pump is changed. The analysis is carried out both in the regime of fluorescence and in the regime of amplified spontaneous emission. It is shown that a pump polarization perpendicular to the fiber symmetry axis yields not only higher emission efficiency but also narrower axial angular width. The effect of the polarization of the pump beam on the properties of the amplified spontaneous emission is also measured, including its threshold-like energy, relative efficiency, and optical gain. The results indicate that the pump polarization determines the light-emitting performance of dye-doped polymer optical fibers.

Machining of high-aspect ratio slots is a common operation in industry, particularly in the mold and die and aerospace sectors. Electrical Discharge Machining (EDM) is a competitive technology for this operation, since it does not depend on material hardness and can fulfill strict geometrical requirements. However, due to debris accumulation in the narrow gap, the machining depth for stable machining is limited. The present work includes original findings about the influence of machined holes on flushing efficiency. Different configurations for this basic approach have been proposed and their performance discussed in terms of machining time and electrode wear. A remarkable and original finding is that continuous pockets or open holes are much better than the separated or closed holes. Furthermore, the paper shows that a sudden change in material removal rate occurs when the vacant spaces of the holes are sunk in the slot. A deeper insight into the EDM phenomena has been achieved through a study of discharge parameters, by analyzing discharge frequency, duty factor, discharge delay time and discharge off-time. In this study, using the proposed electrode reduced the process time by as much as 65% in the machining of 10 mm depth slots. Moreover, machining stability can be guaranteed if the flushing pockets machined on the electrode go through the whole depth of the machine.

Multi-axis Electrical Discharge machining has become a feasible solution in the manufacturing of complex geometry parts of the aerospace and energy industry. In EDM, the final work piece is principally affected by electrode wear and gap width. The machine tool manufacturers provide limited information concerning both features, in which they do not consider the electrode geometry and electrode path. Thus, nowadays, previous highly time and cost consuming trial-and-error strategies are necessary for the machining of complex free form geometries. It is believed that a further understanding of electrode wear and gap width distribution patterns related with electrode geometry and machining path could enhance the electrode design and improve the process efficiency. Hence, the present work proposes easy-to-put in practice electrode wear and gap indicators, for those cases in which the average definition of wear is not enough. Furthermore, the proposed indicators have been tested in an experimental study of electrode wear and gap width in the EDM manufacturing of a shrouded blisk.

This paper is focused on novel electrode in-machine dressing strategy by means of EDM for seal slotted parts in aeronautical industry. The feasibility of in-machine electrode dressing applying a linear interpolation to the electrode to recover its frontal face has been analysed. The influence of different approaches in plate materials and parameters were studied. Dressing time, plate wear and geometrical accuracy for the different condition tested has been recorded. Ultrafine graphite as electrode material and mild steel and copper tungsteen as plate materials have been analysed in this work.

Wire Electrical Discharge Machining (WEDM) is a well-known non-conventional machining process for those applications that require both good finishing and tight tolerances. One of the main problems that occur during EDM operations is wire breakage, which leads to stops in the machining process and lowers process productivity. Recent findings have revealed that discharge accumulations near the same spot of the wire are the main cause for wire breakage. If this discharge accumulation is not stopped, the wire finally breaks. In the present work CFD simulations have been effectively used to simulate dielectric flow and particle movement. The effect of particle size and position, together with the effect of high and low pressure flushing conditions have been analyzed. The studied variables have a clear effect on debris evacuation, and it can be concluded that particle size and position, together with nozzle position affect process stability and wire breakage. This work can help to develop new WEDM strategies that consider the relation between mentioned variables and wire breakage.

Due to their extremely performant capabilities, super-alloys are gratefully acknowledged by mechanical designers to satisfy the requisites from the combustion chambers and other hot parts from the aircraft turbine. However, the high mechanical resistance and high chemical reactivity of heat resistant super-alloys (HRSA) lead to very aggressive machining operations where the tool life must be conveniently protected with cutting fluids. The novelty in this work lies in the idea of applying cryogenic cooling with MQL lubrication (CryoMQL) with CO2 as internal coolant to favor the integration of more environmental friendly machining systems. To prove the benefits from the novel technique, CryoMQL was compared with other lubri-coolant technologies. In this context, contour milling tests were carried out in Inconel 718.

Traceability is a critical issue in the manufacturing of aerospace components. However, extracting understandable information from huge amounts of data from manufacturing processes may become a very difficult task. In this paper, a novel proposal for geometrical defect detection in the manufacturing of fir-tree slots for disk turbines using wire electrical discharge machining is presented. Useful data about the wire Electrical Discharge Machining (WEDM) process are collected every 5 ms and each single discharge is classified as a function of ignition delay time. Information from this large amount of data is extracted by using a deep neural network, which includes two hidden dense layers, each with 64 units and Relu activation, and it ends with a single unit with no activation. The average of the per-epoch absolute error (MAE) scores has been used to decide the optimum training situation for the deep learning network. Validation of the method has been carried out by machining a high-precision fir-tree slot for a disk turbine under industrial conditions. Results show that even though a strict tolerance band of &plusmn, 5 &micro, m has been applied, as many as 80% of the predictions from the network match the results of the conventional measuring method (coordinate measuring machine).

The use of alternative processes for the manufacturing of aeronautical components is essential in order to fulfill the requirements that have been set by the aircraft sector. One particular solution that has been used for certain applications is that of Electrical Discharge Machining (EDM). The EDM process can machine any electrically conductive material, irrespective of its hardness or mechanical properties, and is thus a useful solution for difficult-to-machine aerospace alloys. However, due to its thermal nature, the EDM process induces metallurgical changes in the machined material, which in turn may reduce its fatigue service life. For this reason, the aerospace industry has restricted the use of EDM to the manufacturing of selected components. Nevertheless, there have recently been significant advances in the development of EDM generators that minimize thermal input toward the machined component. As a consequence, it is critical to know the extent to which these new EDM processes affect fatigue service life in aerospace alloys, in order to adequately evaluate the feasibility of using this process. Given the limited information in the literature regarding this topic, the present paper describes a study of the fatigue life of WEDM produced nickel-based Inconel® 718. In order to examine the capabilities of WEDM, fatigue specimens were manufactured using both this procedure and the grinding process (used as a reference for comparison). Surface analysis, metallographic studies, residual stresses, fractography and axial fatigue tests are described and discussed. The results showed that conducting the WEDM process with the new generation of machines has a detrimental effect at high fatigue cycles, reducing fatigue strength by approximately 10% in comparison with ground specimens. However, at low fatigue cycles, no significant differences were observed between ground and WEDM samples. These findings have implications for the potential use of the WEDM process in the manufacturing of disk turbine fir-trees.

The properties of the amplified spontaneous emission in rhodamine-6G doped graded-index polymer optical fibres of two different dopant concentrations have been analyzed by using the Variable Stripe Length method, both theoretically and experimentally. A theoretical model based on the laser rate equations describes the dependence of the emitted spectrum on the pumped length successfully. The fibre gains and their dependence on the dopant concentration have been analyzed.

Nowadays the trend of using monolithic parts on aerospace industry has suffered a considerable increase due to the benefits they provide. However, their complex shape and the low machinability of the materials used to manufacture them make their manufacturing by conventional methods difficult or even impossible. Electro discharge machining is an alternative to manufacture this kind of parts. Existing solutions do not offer a generic method that guarantees the smoothness of the erosion path, independently of the workpiece geometry and "user-dependent" features. With the aim to solve the problem, a new objective function has been proposed and a hybrid optimization method (Genetic Algorithm+Trust Region Reflective method) has been implemented. Results obtained by a single variable problem show that the proposed objective function generates a smooth path regardless of machined shape and available degrees of freedom. Therefore, the implemented optimization method combines a low computational cost together with the obtaining of the largest possible electrode. The optimized algorithm has been applied to an industrial case-study, the erosion of a shrouded blisk, to check its adequacy. The lack of instabilities during the erosion of the part proves the best performance of the developed work. An optimized electrode path generation algorithm has been presented.The algorithm can be used to manufacture aerospace components by EDM.An objective function has been proposed to obtain smooth path and stable erosion.The chosen optimization method ensures a large electrode and low computational cost.The developed work has been validated applying it to the erosion of a shrouded blisk.

Manufacturing high aspect ratio slots in low machinability aeronautical materials using conventional machining methods is an arduous work. Electrical discharge machining has become an appropriate solution to carry out this task due to the independence of this process from material properties such as hardness or machinability. Former works show that process parameters have influence on material removal rate (and in consequence on machining time) and on electrode wear. However, the influence of flushing has not been considered yet. During slot erosion, there is a depth in which erosion destabilizes and process time starts to grow. Although the depth in which this instability appears varies slightly with process parameters, this effect is unavoidable because it occurs due to debris accumulation in the erosion zone. The described problem has motivated an experimental study of the debris movements inside slots using different flushing methods. Tests have been carried out using a high speed camera to record and analyze how particles move inside the slot. Trials with no flushing, intermittent flushing applied with a nozzle and continuous flushing have been made. In addition, different electrode jump heights have been programmed. Result show that best debris evacuation is achieved with the highest electrode jump and applying continuous flushing. Besides, the feasibility of the use of numerical simulation in order to analyze alternative flushing methods has been studied. Commercial CFD-Computational Fluid Dynamics - software has been used to simulate a simple problem using no flushing and moving the electrode only. Numerical and experimental results have been compared. Comparison shows that numerical simulation is a good tool for further research on alternative flushing methods.

Manufacturing more efficient low pressure turbines has become a topic of primary importance for aerospace companies. Specifically, wire electrical discharge machining of disc turbine fir-tree slots has attracted increasing interest in recent years. However, important issues must be still addressed for optimum application of the WEDM process for fir-tree slot production. The current work presents a novel approach for tolerance monitoring based on unsupervised machine learning methods using distribution of ionization time as a variable. The need for time-consuming experiments to set-up threshold values of the monitoring signal is avoided by using K-means and hierarchical clustering. The developments have been tested in the WEDM of a generic fir-tree slot under industrial conditions. Results show that 100% of the zones classified into Clusters 1 and 2 are related to short-circuit situations. Further, 100% of the zones classified in Clusters 3 and 5 lie within the tolerance band of &plusmn, 15 &mu, m. Finally, the 9 regions classified in Cluster 4 correspond to situations in which the wire is moving too far away from the part surface. These results are strongly in accord with tolerance distribution as measured by a coordinate measuring machine.

This paper employs the solution-doping technique for the fabrication of active polymer optical fibers (POFs), in which the dopant molecules are directly incorporated into the core of non-doped uncladded fibers. Firstly, we characterize the insertion of a solution of rhodamine B and methanol into the core of the fiber samples at different temperatures, and we show that better optical characteristics, especially in the attenuation coefficient, are achieved at lower temperatures. Moreover, we also analyze the dependence of the emission features of doped fibers on both the propagation distance and the excitation time. Some of these features and the corresponding ones reported in the literature for typical active POFs doped with the same dopant are quantitatively similar among them. This applies to the spectral location of the absorption and the emission bands, the spectral displacement with propagation distance, and the linear attenuation coefficient. The samples prepared in the way described in this work present higher photostability than typical samples reported in the literature, which are prepared in different ways. This research was funded by European Regional Development Fund (ERDF), by Ministerio de Economia y Competitividad (MINECO) (TEC2015-638263-C03-1-R) and by Eusko Jaurlaritza (ELKARTEK KK-2016/0030, ELKARTEK KK-2016/0059, ELKARTEK KK-2017/00033, ELKARTEK KK-2017/00089, IT933-16). The work of Mikel Azkune was supported in part by a research fellowship from the Universidad del Pais Vasco/Euskal Herriko Unibertsitatea (UPV/EHU), Vicerrectorado de Euskera y Formacion Continua, while working on a Ph.D. degree.

Mirrorless graded-index polymer optical fibers doped with the organic dye rhodamine 6G result in very compact broadband fiber lasers in the visible region when pumped from the side. The emission spectrum, threshold, and efficiency obtained on both fiber ends depend on the lengths of the directly illuminated region and of the non-excited ones. The paper analyzes such parameters both experimentally and theoretically for the first time.

In this work, we show a design of a laboratory exercise in which a digital camera has been coupled to a Michelson interferometer based on free-propagation arms. By using the camera, our students measure the evolution of the interference patterns as a function of the difference between the optical paths of the arms. In this way, they obtain the corresponding reduction of the contrast of the fringes. The analysis of the results allows one to calculate the coherence length, and also to relate the temporal coherence of the employed laser with its spectral line profile. The exercise has been carried out with two lasers, which present different coherence lengths.

The emission properties of a graded-index thermoplastic polymer optical fiber and a step-index thermosetting one, both doped with rhodamine 6G, have been studied. The work includes a detailed analysis of the amplified spontaneous emission together with a study of the optical gains and losses of the fibers. The photostability of the emission of both types of fibers has also been investigated. Comparisons between the results of both doped polymer optical fibers are presented and discussed. This work has been funded in part by the Fondo Europeo de Desarrollo Regional (FEDER); by the Ministerio de Economia y Competitividad under project TEC2015-638263-C03-1-R; by the Gobierno Vasco/Eusko Jaurlaritza under projects IT933-16 and ELKARTEK (KK-2016/0030 and KK-2016/0059); by the University of the Basque Country UPV/EHU under program UFI11/16; and by the Japan Society for the Promotion of Science through the Funding Program for World-Leading Innovative R&D on Science and Technology (FIRST Program), initiated by the Council for Science and Technology. The work carried out by I. Parola has been funded by a research grant given by the Departamento de Educacion, Politica Linguistica y Cultura del Gobierno Vasco/Eusko Jaurlaritza for her PhD thesis. We also thank Stela Diamant and Oleg Palchik, from the company Intellisiv Ltd, for providing the thermosetting samples.

In this paper, a methodology for complex surface machining based on cutting forces prediction is presented. The work is focused on blade finishing operations. The cutting forces model developed can be applied to three axis and five axis milling cases. For three-axis cases, the chip thickness is calculated according to traditional analytical methods. On the contrary, for five-axis cases the chip thickness is obtained from a geometric method developed in the paper. The cutting forces values can be calculated for the complete toolpath, but the presented model can also provide the programmer information about the cutting forces in a single point of the toolpath. The cutting force model is integrated in the CAM software in order to provide an extra tool that helps the programmer to decide which the optimal milling strategy is, based on the minimum cutting forces. In the last section, results of a case study based on impeller and blisk blades flank milling are discussed. Model predicted forces and real measured...

The EDM process is adequate for machining of narrow slots in low machinability materials, such as Ni based alloys used for aeronautical applications. This paper studies the influence of main process parameters involved in this process. The objective is to determine the effect of parameters related to the discharge process (current, pulse time and servo voltage) on machining time and electrode wear. Influence of discharge parameters has been studied using Central Composite Design of Experiments. Results reveal that discharge current as well as the time pulse, are the most influencing process parameters. Trends of material removal rate and electrode wear versus current, pulse-time and servo voltage have been analyzed.

The emission properties of rhodamine-6G doped step-index cladded and uncladded thermoset fibres have been studied for a transversal excitation configuration. Measurements include a deep analysis of the amplified spontaneous emission and a detailed study of the optical gains of the fibres by using the Variable-Stripe Length method. The evolution of the emission spectra as a function of the propagation distance has also been reported for both one-photon emission and twophoton emission. Comparisons of the results of the cladded fibres with those of the uncladded ones are presented and discussed.

This paper analyzes the peculiarities of light amplification in doped polymer optical fibres (POFs) by using our computational model under diverse conditions. Specifically, the influence of the numerical aperture and of the radial distribution of the dopant in the fibre, on the one hand, and the most convenient temporal width of the pump pulse, on the other hand, are investigated. Analyses are carried out for both step-index and graded-index POFs. The results presented correspond to fibres excited longitudinally with short light pulses of several energies.; Artikulu honetan, gure eredu konputazionalaren bitartez, argi-anplifikazioaren ezaugarriak aztertu dira dopaturiko polimerozko zuntz optikoetan (PZOetan). Hain zuzen ere, zenbakizko irekiduraren eta dopantearen distribuzio erradialaren eraginaz gain, ponpaketaren denborazko pultsu-zabalera egokiena ere ikertu da. Analisi hauek guztiak maila-indize eta indize gradualeko PZOentzat egin dira. Lorturiko emaitzak energia desberdinetako argi-pultsuen bitartez longitudinalki kitzikaturiko zuntz aktiboetan oinarritzen dira.

The characterization of the spectral emission and of the photostability of polymer optical fibers (POFs) doped with conjugated polymers has been carried out taking into account the distribution of the dopant in the fiber core. Four different conjugated polymers embedded in the matrix of the typical POF material have been analyzed. Measurements include, among others, evolutions of the emission with excitation wavelength and time, spectral changes for different excitation irradiances, and the influence of the propagation distance along the fiber.

Organic dye-doped polymer optical fiber amplifiers (POFAs) are suitable for achieving high gains in short distances in the visible region. This paper presents a computational analysis of the optimum pump power and signal wavelength as a function of fiber length, numerical aperture, and radial distribution of dopant, for the case of a graded-index POFA doped with rhodamine B.

Polymer optical fibers doped with organic dyes can be used as efficient optical amplifiers and lasers in the visible region. We computationally study the spectral evolution with distance of the pulses propagating along such fibers. The main goal is to analyze the lasing threshold and the slope efficiency as functions of the fraction of spontaneous emission that contributes to laser emission. The discussion focuses on rhodamine-6G doped fibers.

A model of partial differential rate equations for the analysis of signal gain in typical europium-chelate-doped polymer optical fibers is presented and solved by a method of finite differences. The qualitative reliability of some of the results is confirmed by means of a simplified analytical expression. Typical types of chelates at various concentrations are studied in order to be able to optimize the fiber length and pumping conditions for attainment of maximum signal gain.

Polymer optical fibers doped with organic dyes can be used as efficient optical amplifiers and lasers in the visible region. We computationally analyze the spectral features of both their fluorescence and their amplified emission for different amounts of overlap between the emission and absorption spectra of the dyes employed. Representative cases are compared by calculating the respective evolutions along the doped fiber of the average wavelength, peak wavelength, and full-width at half-maximum of the output power obtained.

The chromatic dispersion and the refractive index of poly(methyl methacrylate) polymer optical fibers (POFs) have been characterized in this work by using a tunable femtosecond laser and a Streak Camera. The characterization technique is based on the measurement of the time delays of light pulses propagating along POFs at different wavelengths. Polymer fibers of three different lengths made by two manufacturers have been employed for that purpose, and discrepancies lower than 3% have been obtained in all cases. This work has been funded in part by the Fondo Europeo de Desarrollo Regional (FEDER); by the Ministerio de Economia y Competitividad under project TEC2015-638263-C03-1-R, and by the Gobierno Vasco/Eusko Jaurlaritza under projects IT933-16 and ELKARTEK (KK-2016/0030, KK-2017/00033, KK-2017/00089 and KK-2016/0059). The work of Mikel Azkune was supported in part by a research fellowship from the Universidad del Pais Vasco/Euskal Herriko Unibertsitatea (UPV/EHU), Vicerrectorado de Euskera y Formacion Continua, while working on a Ph.D. degree.

In this work we perform a detailed experimental and theoretical analysis of the properties of amplified spontaneous emission (ASE) in a rhodamine-6G-doped graded-index polymer optical fiber when the fiber is pumped either longitudinally or transversally with respect to the fiber axis. The dependence of the ASE threshold and efficiency on fiber length has been compared for both schemes of excitation. A theoretical model for longitudinal excitation has been carried out by means of the laser rate equations as functions of time, distance traveled by light and wavelength. The analysis takes into account that the fiber is a typical graded-index POF in which the radial distributions of light power density and dye concentration are not uniform. The theoretical calculations agree satisfactorily with the experimental results. The photodegradation of the ASE intensity has also been measured for both pumping schemes.

Use of heat-resistant alloys is growing worldwide in aeronautical turbo-machinery industry. One of the most used materials is Inconel 718. This material is featured by high resistance to corrosion and oxidation while keeping good mechanical properties at high temperature. However, low machinability of this material results in poor material removal rates and premature tool wear, among other drawbacks. Consequently, mineral cutting fluids are injected in the cutting zone in order to improve machining. However, today's environmental consciousness leads us to propose the cryoMQL technology as an ecological alternative. In order to achieve better results when milling Inconel 718, a CO2 cryogenic regulation system and a nozzle adaptor have been developed to use cryoMQL and a comparative analysis is performed with regard to other coolant alternatives.

The aim of this work is to analyze the propagation of the emitted light in fluorescent POFs by using the side-illumination technique. In particular, we have studied the angular distribution of the emitted light as a function of the launching angle and of the height of the incident beam. A theoretical model has been developed in order to explain the experimental measurements. A good agreement between the theoretical and the experimental results has been obtained both qualitatively and quantitatively. It is shown that both the theoretical and the experimental critical angles are appreciably higher than the meridional one corresponding to the maximum acceptance angle for a single source placed at the fiber axis. This increase changes the value of several important parameters in the performance of active fibers. The analysis has been performed in polymer optical fibers doped with a conjugated polymer.

Polymer optical fibers (POFs) doped with organic dyes can be used to make efficient lasers and amplifiers due to the high gains achievable in short distances. This paper analyzes the peculiarities of light amplification in POFs through some experimental data and a computational model capable of carrying out both power and spectral analyses. We investigate the emission spectral shifts and widths and on the optimum signal wavelength and pump power as functions of the fiber length, the fiber numerical aperture and the radial distribution of the dopant. Analyses for both step-index and graded-index POFs have been done. This work was supported by the Ministerio de Ciencia e Innovacion under projects TEC2009-14718-C03-01 and COBOR, by the Gobierno Vasco/Eusko Jaurlaritza under projects GIC07/156-IT-343-07, AIRHEM, S-PR10UN04, and S-PE10CA01, and by the Diputacion Foral de Bizkaia/Bizkaiko Foru Aldundia under project 06-12-TK-2010-0022. The research leading to these results has also received funding from the European Commission's Seventh Framework Programme (FP7) under grant agreement no. 212912 (AISHA II). I. Ayesta has a research fellowship from Vicerrectorado de Euskara y Plurilinguismo, Universidad del Pais Vasco/Euskal Herriko Unibertsitatea (UPV/EHU), while working on his PhD.

In this work we analyze experimentally and theoretically the properties of amplified spontaneous emission (ASE) in a rhodamine-6G-doped graded-index polymer optical fiber. A theoretical model based on the laser rate equations describes the ASE features successfully. The dependence of the ASE threshold and efficiency on fiber length is analyzed in detail.

Non- conventional machining processes play a critical role in the manufacturing of advanced components for high-added value sectors such as aerospace and bioengineering. Zero defect manufacturing is a key objective in these sectors, which requires more efficient monitoring techniques than those classically used in other sectors. In the classical approach, the engineer him/herself has to decide the statistical variables from which relevant information about the process will be obtained. Scientific literature shows that threshold levels were manually set for the voltage signal for monitoring and control of the Wire Electrical Machining (WEDM) process applied to aerospace components. However, now that the amount of data available is extremely large (Big Data), the decision on the statistics is not always straightforward. In this context, unsupervised Artificial Intelligence (AI) techniques provide a very interesting approach to the problem. In this paper, unsupervised machine learning techniques are used to extract relevant information from the voltage signal in the wire electrical discharge machining process.