Research Interests:
Research Interests: Engineering, Materials Science, Laser, Corrosion, Stress corrosion cracking, and 13 moreFatigue crack growth, Surface Roughness, Profitability, Materiales, Surface Properties, Residual Stress, Stress Corrosion Cracking, Wear resistance, Mecánica, Experimental Method, Corrosion Resistance, Mechanical Property, and Crack growth
Research Interests:
Research Interests:
Previous calculations on the dynamics of inertial confinement fusion (ICF) targets subject to irradiation show that radiation plays a major role in the ignition phase of these targets, because at some hundred electron volts it becomes the... more
Previous calculations on the dynamics of inertial confinement fusion (ICF) targets subject to irradiation show that radiation plays a major role in the ignition phase of these targets, because at some hundred electron volts it becomes the dominant energy transport mechanism over electron /plus/ supra-thermal particle conduction. Correspondingly, the several kilo-electron-volts of thermal radiation originating from the hot zones of the reacting fusion fuel plays a role no less important in the process of burn propagation. A major problem in the analysis of radiation energy transport in dense, high-temperature media (typical of ICF systems) is the strong nonlinear character of the temperature-dependent radiation source term, even under the assumption of local thermodynamic equilibrium. In the cases in which local thermodynamic equilibrium (LTE) cannot be assumed, the radiation field itself, including its detailed frequency dependence, influences to a critical extent the transport medium optical properties and emission dynamics. Consequently, the nonlinear character of the problem is significantly strengthened, thus needing a detailed rather that average-based treatment. The PLANCKY code solves the radiation transport equation in a multigroup framework for the energy (frequency) variable of the radiation-specific intensity with angular dependence taken into account through a discrete ordinates treatment. 7 refs., 1more » fig.« less
Research Interests:
Research Interests:
Several new commercial advanced high-strength steels exhibit high strength and enhanced formability. These materials have the potential to affect cost and weight saving while improving performance. However, welding, by modifying the... more
Several new commercial advanced high-strength steels exhibit high strength and enhanced formability. These materials have the potential to affect cost and weight saving while improving performance. However, welding, by modifying the microstructure of the steel, has in general a detrimental effect on the mechanical properties of structural components. If high power density technologies are used, the result is that the
Research Interests: Engineering, Materials Science, Microstructure, Solid Mechanics, Advanced high strength steels, and 12 moreWelding, CHEMICAL SCIENCES, Electron beam welding, High Power, Microstructures, Numerical Model, Electron Beam, Experimental Analysis, WELDED JOINT, Formability, Ultimate Tensile Strength, and Mechanical Property
Laser shock processing (LSP) has been presented as an effective technology for improving surface mechanical and corrosion properties of metals, and is being developed as a practical process amenable to production engineering. The main... more
Laser shock processing (LSP) has been presented as an effective technology for improving surface mechanical and corrosion properties of metals, and is being developed as a practical process amenable to production engineering. The main acknowledged advantages of the laser shock processing technique consist on its capability of inducing a relatively deep compression residual stresses field into metallic alloy pieces allowing an improved mechanical behaviour, explicitly, the life improvement of the treated specimens against wear, crack growth and stress corrosion cracking. In the present paper, practical results at laboratory scale on the application of Laser Shock Processing are presented showing the obtained tensile residual stresses relaxation along with corresponding preliminary results about the resulting mechanical properties improvement induced by the treatment. Additionally, the influence of different irradiation parameters will be presented along with a physical interpretation...
Research Interests:
Research Interests:
Research Interests:
In this paper, a short conceptual review (avoiding details en physico-mathematical formulation for the sake of brevity) of the fundamental energy transport mechanisms in the laser matter interaction at high intensities will be presented... more
In this paper, a short conceptual review (avoiding details en physico-mathematical formulation for the sake of brevity) of the fundamental energy transport mechanisms in the laser matter interaction at high intensities will be presented along with the associate calculational tools normally used for their simulation, and, as a sample of this kind of calculational SchemeS, a description will be provided on a particular calculaticnal rrdel able to simulate the plasma behaviour under a coupled schen relating the radiative and fluiddynamic rrdium evolution.
Research Interests:
Due to its wide applicability in industry, devising microstructures on the surface of materials can be easily implemented and automated in technological processes. Laser Surface Texturing (LST) is applied to modify the chemical... more
Due to its wide applicability in industry, devising microstructures on the surface of materials can be easily implemented and automated in technological processes. Laser Surface Texturing (LST) is applied to modify the chemical composition, morphology, and roughness of surfaces (wettability), cleaning (remove contaminants), reducing internal stresses of metals (hardening, tempering), surface energy (polymers, metals), increasing the adhesion (hybrid joining, bioengineering) and decreasing the growth of pathogenic bacteria (bioengineering). This paper is a continuation and extension of our previous studies in laser-assisted texturing of surfaces. Three different patterns (crater array-type C, two ellipses at 90° overlapping with its mirror-type B and 3 concentric octagons-type A) were applied with a nanosecond pulsed laser (active medium Nd: Fiber Diode-pumped) on the surface of a ferritic stainless steel (AISI 430). Micro texturing the surface of a material can modify its wettabilit...
Research Interests:
The effect of process parameters and the orientation of the cladding layer on the mechanical properties of 316L stainless steel components manufactured by laser metal deposition (LMD) was investigated. High aspect-ratio walls were... more
The effect of process parameters and the orientation of the cladding layer on the mechanical properties of 316L stainless steel components manufactured by laser metal deposition (LMD) was investigated. High aspect-ratio walls were manufactured with layers of a 4.5 mm wide single-cladding track to study the microstructure and mechanical properties along the length and the height of the wall. Samples for the tensile test (according to ASTM E-8M-04) were machined from the wall along both the direction of the layers and the direction perpendicular to them. Cross-sections of the LMD samples were analyzed by optical and scanning electron microscopy (SEM). The orientation of the growing grain was observed. It was associated with the thermal gradient through the building part. A homogeneous microstructure between consecutive layers and some degree of microporosity was observed by SEM. Uniaxial tension tests were performed on samples extracted from the wall in perpendicular and parallel dire...
Research Interests:
Research Interests:
Laser Welding (LW) is more and more chosen as manufacturing process due to its advantages, namely capability of joining small dimension parts, opportunities for joining of special materials, less Heat Affected Zone, good repeatability,... more
Laser Welding (LW) is more and more chosen as manufacturing process due to its advantages, namely capability of joining small dimension parts, opportunities for joining of special materials, less Heat Affected Zone, good repeatability, high speed etc. Nowadays, LW is of particular interest in manufacturing small mechatronics parts of mechanic, electric or electronic nature. This paper underscores several achievements in three key-processes, namely classical LW, laser hybrid welding (LHW) and remote laser welding (RLW). These results were obtained at the UPM Laser Centre (CLUPM) of Polytechnical University of Madrid (Universidad Politecnica de Madrid) with a CO2 laser of 3350 W dedicated to RLW of thin sheets for automotive and other sectors, and with a Nd:YAG laser of 3300 W, respectively. The second is operated by a 6-axis ABB robot and is meant for various laser processing methods, including welding. Several important applications experimented at CLUPM and recently implemented in ...
Research Interests:
Research Interests:
Laser Shock Processing (LSP) is continuously developing as an effective technology for improving the surface and mechanical properties of metallic alloys and is emerging in direct competition with other established technologies, such as... more
Laser Shock Processing (LSP) is continuously developing as an effective technology for improving the surface and mechanical properties of metallic alloys and is emerging in direct competition with other established technologies, such as shot peening, both in preventive manufacturing treatments and maintenance/repair operations [...]
Research Interests:
In recent years, an increasing interest in designing magnesium biomedical implants has been presented due to its biocompatibility, and great effort has been employed in characterizing it experimentally. However, its complex anisotropic... more
In recent years, an increasing interest in designing magnesium biomedical implants has been presented due to its biocompatibility, and great effort has been employed in characterizing it experimentally. However, its complex anisotropic behaviour, which is observed in rolled alloys, leads to a lack of reliable numerical simulation results concerning residual stress predictions. In this paper, a new model is proposed to focus on anisotropic material hardening behaviour in Mg base (in particular AZ31B as a representative alloy) materials, in which the particular stress cycle involved in Laser Shock Processing (LSP) treatments is considered. Numerical predictions in high extended coverage areas obtained by means of the implemented model are presented, showing that the realistic material’s complex anisotropic behaviour can be appropriately computed and—much more importantly—it shows a particular non-conventional behaviour regarding extended areas processing strategies.
Research Interests:
Abstract Laser shock processing (LSP) is increasingly applied as an effective technology for improving the properties of different metallic components. This is done principally to enhance their corrosion and fatigue life behaviour, stress... more
Abstract Laser shock processing (LSP) is increasingly applied as an effective technology for improving the properties of different metallic components. This is done principally to enhance their corrosion and fatigue life behaviour, stress corrosion cracking resistance, etc. In this paper, LSP has been applied to a commercially pure Mg and a Mg-1Zn alloy (wt%) which is aimed to be used as a biodegradable material for biomedical applications. The rational for microalloying with Zn is not only influencing the bacterial response, but also enhancing corrosion resistance and mechanical strength of Mg without causing any toxic effect. The present work is focussed on the examination of the effects of the LSP treatment on the relevant surface related properties of the samples and their correlation with the surface and subsurface induced modifications such as residual stress state, microstructural, roughness, hardness, etc. Central to this investigation is the study of the corrosion response and antibacterial properties against Staphylococcus epidermidis of the different samples as a function of material and LSP parameters. The results show that the application of LSP introduces compressive residual stresses up to 1 mm deep. This occurs together with a significant improvement in corrosion resistance, and less bacterial colonization.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
The evolution over time of wettability properties of super hydrophobic Al2024 developed using an IR-, ns-laser was studied under different storage conditions.
Research Interests:
A novel structural piezoresistive pressure sensor with annularly grooved membrane combined with rood beam has been proposed for low pressure measurements based on silicon substrate. In this study, a design method, including the model... more
A novel structural piezoresistive pressure sensor with annularly grooved membrane combined with rood beam has been proposed for low pressure measurements based on silicon substrate. In this study, a design method, including the model design, dimensions optimization, and performance prediction of the novel structure sensor, is presented. The finite element method has been used to analyze the stress distribution of sensitive elements and the deflection of membrane. On the basis of simulation results, the relationships between structural dimension variables and mechanical performance are deduced, which make the fabrication processes more efficient. According to statistics theory, the coefficient of determination R(2) and residual sum of squares are introduced to indicate whether the fitting equations and curves match well with the simulation results. After that, a series of the optimal membrane dimensions are determined. Compared with other structural sensors, the optimized sensor achi...
Research Interests:
Ultrahydrophobic self cleaning surface is fabricated with nanosecond laser source on aluminium foil.
Research Interests: Materials Science and RSC
Research Interests: Materials Engineering, Mechanical Engineering, Biomedical Engineering, Titanium, Surface topography, and 11 moreResidual Stresses, Composite Material, Pressure, Surface Properties, Shot Peening, Materials Testing, Alloys, Biocompatible Materials, Waterjet Peening , Fatigue Resistance, and Grit Blasting
Laser shock processing (LSP) is a technique for strengthening metals. This process induces a compressive residual stress field which increases fatigue crack initiation life, reduces fatigue crack growth rate and increases wear resistance... more
Laser shock processing (LSP) is a technique for strengthening metals. This process induces a compressive residual stress field which increases fatigue crack initiation life, reduces fatigue crack growth rate and increases wear resistance of metals. We present a configuration and results in the LSP concept for metal surfaces treatments in underwater layer with constant thickness using laser irradiation at 1064
Research Interests:
This paper presents a simulation study of the phenomenology arising from plasma expansion between the confinement layer and the base material, which is specifically addressed as a clear factor that influences the subsequent... more
This paper presents a simulation study of the phenomenology arising from plasma expansion between the confinement layer and the base material, which is specifically addressed as a clear factor that influences the subsequent thermo-mechanical behaviour of the treated specimens. Results based on the calculation model show that a number of process scaling laws have been obtained, which allow a predictive
Research Interests:
Laser micromachining techniques are among the most promising fabrication processes in strategic industrial fields. Although lasers systems have been widely applied last twenty years in semiconductor industry for microfabrication process... more
Laser micromachining techniques are among the most promising fabrication processes in strategic industrial fields. Although lasers systems have been widely applied last twenty years in semiconductor industry for microfabrication process development, the current availability of new excimer and Diode Pumped Solid State Lasers (DPSS) sources are extending the applications fields of laser microprocessing. Nowadays MEMs, fluidic devices, advanced sensors and
Research Interests:
ABSTRACT
Research Interests:
Laser shock processing (LSP) has been proposed as a competitive alternative technology to classical treatments for improving fatigue and wear resistance of metals. We present a configuration and results in the LSP concept for metal... more
Laser shock processing (LSP) has been proposed as a competitive alternative technology to classical treatments for improving fatigue and wear resistance of metals. We present a configuration and results in the LSP concept for metal surfaces treatments in underwater laser irradiation at 535 nm. A convergent lens is used to deliver 0.9 J/cm2 in an 8 ns laser FWHM pulse
Research Interests:
ABSTRACT Technology for nano-scale integration is achieving promising results for the development of novel sensors systems to explore its application to important medical, biopharmaceutical and environmental applications such as drug... more
ABSTRACT Technology for nano-scale integration is achieving promising results for the development of novel sensors systems to explore its application to important medical, biopharmaceutical and environmental applications such as drug development and immunoassays. They use well-known optical structures such as waveguide Surface Plasmon Resonance (SPR), Mach-Zehnder (M-Z) interferometers, two-mode waveguide interferometry, but need complex optical coupling such as inverted taper and grating couplers. The proposed system is based on the observation of external reflectivity profiles. A dielectric micro-nano structure consisting of a triangular lattice of sub-micro-holes fabricated on a SiO2/Si wafer produces spectra interference patterns as a function of the angle of incidence for both p and s polarization directions as well as a phase shift between s and p polarisation. The measurements have been performed simultaneously by using a linearly polarized laser operating at 675 nm with a tightly focussed beam, which provides a sub-micrometer spot and therefore allow these measurements to be accomplished in a single sub-micro-hole. Consecutively the reflectivity of the photonic structures is measured and analyzed over a wide range of wavelengths of light as well. The sub-micro-holes are filled with optical liquids with different refractive indices, involving a change in the effective refractive index which produces variations in the phase shift and the interference reflectivity patterns. The optical system is able to measure extremely small volumes of analyte (approximately 0.1 femtolitres per hole). The simultaneous use of three optical techniques, remove ambiguities and improve reliability. The detection limit achievable with this system is up to 10−6 R.I.U. which is competitive with the current state of the art, and could be improved with not complex changes for all the optical techniques. Furthermore, the complexity of coupling in the current photonic label-free biosensors is avoided, as the light is collected normally.
Research Interests:
On the basis of the Ashcroft and Sturm theory on the optical properties of metals, a theoretical model is proposed for the prediction of frequency- and temperature-dependent interaction properties of pure metals subjected to laser... more
On the basis of the Ashcroft and Sturm theory on the optical properties of metals, a theoretical model is proposed for the prediction of frequency- and temperature-dependent interaction properties of pure metals subjected to laser irradiation in laser processing applications. This model is directly suitable for on-line coupling to numerical process modelling without any recursion to external experimental data fitting.
Research Interests:
... owing to a number of potential advantages, such as increased accuracy, stability, reliability and linearity. ... A base pressure of about 10 −7 mbar is obtained in the system chamber. ... AE 1982 Surface ripples on silicon and gallium... more
... owing to a number of potential advantages, such as increased accuracy, stability, reliability and linearity. ... A base pressure of about 10 −7 mbar is obtained in the system chamber. ... AE 1982 Surface ripples on silicon and gallium arsenide under picosecond laser illumination Appl. ...
Research Interests: Engineering, Materials Science, Technology, Laser, Scanning Electron Microscopy, and 12 moreTransparent Conducting Oxide Materials, Optoelectronics, Thin Film, Morphological Analysis, Laser Ablation, High performance, Laser processing, Confocal Laser Scanning Microscopy, Process Development, Amorphous Silicon, Laser Micromachining, and Indium tin oxide
Research Interests:
Laser shock forming is conceived as a non-thermal laser forming method of thin metal sheets using the shock wave induced by laser irradiation to modify the target curvature. The plastic deformation induced by the shock wave and the direct... more
Laser shock forming is conceived as a non-thermal laser forming method of thin metal sheets using the shock wave induced by laser irradiation to modify the target curvature. The plastic deformation induced by the shock wave and the direct plasma pressure applied on the material generate a residual stress distribution in the material finally leading to its bending. Using water
Research Interests:
Research Interests:
Research Interests:
Research Interests:
An inverse approach for the Laser Surface Hardening Process is proposed. It departs from specific austenization requirements in terms of a desired size for the austenized region at any cross section of the treated sample, aiming at... more
An inverse approach for the Laser Surface Hardening Process is proposed. It departs from specific austenization requirements in terms of a desired size for the austenized region at any cross section of the treated sample, aiming at calculating suitable process parameters to obtain it. This approach contrasts with conventional direct procedures, from process parameters to thermal cycles and austenite distribution, where stochastic design strategies, falling on the dynamics of successive approximations, are performed. A thermo-metallurgical numerical model is used to determine the irradiance distribution capable of meeting the prescribed austenization requirements. This theoretical irradiance distribution is implemented by means of an adaptative high-frequency scanning of the treated surface. The minimum scanning frequency to guarantee the equivalence between the pursued theoretical irradiance distribution and the scanning is established attending to the evolution of temperature and i...
Research Interests:
A novel structural piezoresistive pressure sensor with four-grooved diaphragm combined with rood beam has been proposed for low pressure measurements of less than 1 psi. The proposed sensor chip is fabricated on a SOI wafer by traditional... more
A novel structural piezoresistive pressure sensor with four-grooved diaphragm combined with rood beam has been proposed for low pressure measurements of less than 1 psi. The proposed sensor chip is fabricated on a SOI wafer by traditional MEMS micromachining and anodic bonding technology. By localizing more strain energy in the stress concentration region and increasing the constraint of the partial pedestal, the sensor achieved a high sensitivity and linearity of 30.9 mV/V/psi and 0.25% FSS respectively at room temperature, and thereby the contradiction between sensitivity and linearity is alleviated. Besides, a sensitivity of 21.2 mV/V/psi and a linearity of 0.5% FSS were obtained at 150 °C, which illustrates that the proposed sensor has a stable high temperature output characteristic. Additionally, the mechanisms about strain energy transmission and partially stiffened diaphragm are also discussed.
Research Interests:
Laser surface texturing (LST) is a method to obtain micro-structures on the material’s surface for improving tribological performances, wetting tuning, surface treatment, and increasing adhesion. The material selected for LST is AISI 430... more
Laser surface texturing (LST) is a method to obtain micro-structures on the material’s surface for improving tribological performances, wetting tuning, surface treatment, and increasing adhesion. The material selected for LST is AISI 430 ferritic stainless steel, distinguished by the low cost in manufacturing, corrosion resistance, and high strength at elevated temperature. The present study addresses the morphology of new pattern designs (crater array, ellipse, and octagonal shapes). The patterns are applied on the stainless-steel surface by a non-contact method with high quality and precision nanosecond pulsed laser equipment. The investigation of laser parameter influence on thermal affected area and micro-structures is accomplished by morphological and elemental analysis (SEM + EDX). The parameters of the laser micro-patterning have a marked influence on the morphology, creating groove-type sections with different depths and recast material features. From the SEM characterizatio...
Research Interests:
Research Interests:
Numerical simulation codes provide an essential tool for analyzing the very broad range of concepts and variables considered in ICF targets. In this paper, the relevant processes embodied in the NORCLA code, needed to simulate ICF targets... more
Numerical simulation codes provide an essential tool for analyzing the very broad range of concepts and variables considered in ICF targets. In this paper, the relevant processes embodied in the NORCLA code, needed to simulate ICF targets driven by heavy ion beams will be presented. Atomic physic models developed at DENIM to improve the atomic data needed for ion beam
Research Interests:
Research Interests:
Research Interests:
In the present paper, a model is presented aiming to provide a physical basis for the theoretical estimation of both the plasma expansion dynamics following laser irradiation and the shock wave propagation into the treated material with a... more
In the present paper, a model is presented aiming to provide a physical basis for the theoretical estimation of both the plasma expansion dynamics following laser irradiation and the shock wave propagation into the treated material with a specific consideration of its constitutional properties (i.e. taking into account its real mechanical and E.O.S. parameters). Although initially limited to a 1D description, the proposed model aims to overcome the difficulties existing for an accurate theoretical estimation of the process due to the treated material behavior not directly amenable to analytical solutions and sometimes modeled through empirical approaches, and to provide a detailed treatment of the plasma behavior (i.e. ionization, breakdown, etc.). Additionally, and as a direct consequence of its analytical-numerical character, the model can provide a fully time dependent representation of the processes, including the laser pulse temporal profile, what is a real advance over previous theoretical studies.
Research Interests:
ABSTRACT Position detectors are useful for alignment and orientation sensing. Charge-coupled devices (CCDs) are used in small-area systems. Four-quadrant diodes are a low-cost, limited-accuracy alternative. In cases where either large... more
ABSTRACT Position detectors are useful for alignment and orientation sensing. Charge-coupled devices (CCDs) are used in small-area systems. Four-quadrant diodes are a low-cost, limited-accuracy alternative. In cases where either large area or reliability under harsh conditions are required, thin-film-silicon sensors may become the only reasonable choice. The paper proposes a simple structure for making such devices, describes the first experiments and discusses the key issues faced, with emphasis on laser scribing.