Laser-assisted Processes Research Articles

Laser-assisted Belt Grinding with Creep Feed for Enhanced Surface Integrity and Abrasive wear Reduction

Creep feed belt grinding (CFBG) is a vital machining technique used for intricate curved parts like aero-engine blades and flaps. CFBG effectively removes material by using larger depths of cut and lower feed rates, but high loads can lead to severe belt wear and thermal damage defects in the process. Laser-assisted processing technology can mitigate tool wear and enhance machining quality. This research compared and analyzed belt wear behavior and its impact on the surface integrity of titanium alloys in laser-assisted creep feed belt grinding (LCFBG) and CFBG processes. The following conclusions were drawn: The local thermal effect of the laser softened the material, reduced the grinding force. The wear pattern of the abrasive grains changed from abrasive fracture and stripping to steady abrasive wear. The effective life of the belt increased by about 33 %. In addition, due to reduction in grinding force, the thermo-mechanical coupling effect caused by material removal is reduced, and the grinding temperature is lowered. As a result of the reduction in grinding force and temperature, the mechanical and thermal stresses are reduced, the oxidation reaction on the surface of the titanium alloy is weakened, and the residual stress is lowered, leading to an improvement in surface quality.

Composition Profiles at the Metal Substrate-Deposit Interface Produced in Laser-Assisted Additive Manufacturing Processes.

The cross-section of various substrate-deposit metal pairs obtained with a laser-assisted additive manufacturing process has been studied by observing the composition profile with energy-dispersive spectroscopy (EDS). The EDS composition profiles observed with a sufficiently high data acquisition time revealed that the composition profile is asymmetric. By scanning toward the growth direction, a sudden composition variation was observed, which was followed by a slow decay. The character of the composition profile was the same for a number of substrate-deposit pairs, and similar trends were found in various earlier publications as well. A mathematical model for the composition variation is suggested based on the assumption that a spontaneous homogenization process takes place in the intermixing (dilution) zone of the remelted top layer of the substrate. The equation obtained makes it possible to quantitatively describe the composition profile of each component that exhibits a concentration difference between the substrate and the deposit, provided that the mole fraction difference much exceeds the scattering of the data measured. The suggested model has also been applied successfully to composition profiles published in other works, hence exhibiting general relevance. Since the variation in some physical parameters (such as hardness) along the growth direction has been reported to follow the same pattern, it is assumed that the root cause in these cases may also be the composition variation.

Key technologies for laser-assisted precision grinding of 3D C/C-SiC composites

Due to their exceptional and distinctive qualities, 3D C/C-SiC composites are widely utilized in producing high-end equipment and the aerospace national defense industries. However, the hard and pseudo plastic nature of the material and its anisotropies make it challenging to process. To improve the processing quality of 3D C/C-SiC composites, laser-assisted precision grinding technology is introduced in this paper, which innovatively controls the depth of the thermally induced damage layer by adjusting the laser process parameters to reduce the hard brittleness of the material, and then the surface is created by precision grinding with a grinding wheel on this basis. Experiments on laser-induced damage, laser-assisted grinding, and diamond scratching were carried out to investigate the effect of laser parameters on material damage and the effect of laser-assisted grinding processes, with an emphasis on revealing the mechanism of material removal. The results show that laser irradiation causes complex reactions such as sublimation, decomposition, and oxidation of 3D C/C-SiC composites, resulting in SiO2 and Si and recondensed SiC, causing surface/subsurface damage. A maximum reduction in normal grinding force, tangential grinding force, specific grinding energy, and surface roughness of 35.6%, 43.6%, 43.58%, and 24.22%, respectively, compared to conventional grinding processes with laser-assisted grinding. After laser irradiation, the degree of brittle fracture in the precision grinding of workpieces is significantly reduced due to the degradation of matrix and fiber damage caused by laser irradiation, which reduces the hard and pseudo plastic properties of the material. The removal mechanism shows a trend of ductile domain removal in the grinding of thermally damaged layers, which reduces the grinding force and improves the surface quality.

Interfacial thermal conductance of 7075 aluminum alloy microdroplets in contact with a solid at fast melting and crystallization

Ultrafast nanocalorimetry, in combination with high-speed IR thermography, is used to measure the interfacial thermal conductance (ITC) of the thermal contact of metal microdroplets with a solid during fast melting (including laser heating). IR thermography and membrane nanocalorimetry were used to measure the temperature difference at the membrane/sample interface during the melting and crystallization of aluminium alloy (AA7075) microdroplets (20 μm in diameter) over a wide range of heating and cooling rates (up to 105 K s−1). This is the first time ITC has been measured at such high heating and cooling rates with this new method. We found that the interfacial temperature difference reaches about 80 K during the solidification of microdroplets during laser heating. This result is significant for understanding various industrial laser-assisted processes. It has been established that ITC measured for AA7075 microdroplets gradually increases by an order of magnitude during melting in the range from the solidus temperature to the liquidus temperature of the alloy. This unusual behavior of ITC during melting can be important for understanding and optimizing laser-assisted additive manufacturing processes.

Particle detection in rare gas solid crystals: a feasibility experimental study—exploring new ways for dark matter searches

AbstractThis article reviews the experimental activity that has been carried out within the INFN DEMIURGOS research and development (R &D) project. This R &D concerns the study of possible innovative experimental approaches for the detection of low-energy-releases of feeble interacting particles within the matter. Possible applications could be the direct investigation of Dark Matter candidates. The idea behind the proposed scheme is to exploit rare gas solid crystals both pure and doped, combined with the in-vacuum single electron detection technology. In pure materials, the signal can be the charge produced directly during the ionization. Laser-assisted processes can instead be used to probe low-energy-releases in doped materials. Both these mechanisms should lead to a detectable electronic signal triggered by the incoming particle. In such a way, energy threshold ranging from meV to tens of eV could in principle be reached, opening-up the possibility to probe theoretically, well-motivated regions of unexplored electroweak parameter-space and thus test the existence of light Dark Matter candidates. The activity presented here has been performed to understand the mechanisms at the basis of the proposed detection scheme and possible showstopper. The experimental investigations refer to the research and development phases about: the crystal growing techniques and the corresponding set-up, the electrons’ extraction from rare gas crystals to the vacuum environment, and finally the spectroscopic studies on atomic species embedded into rare gas matrices.

Emerging laser-assisted vacuum processes for ultra-precision, high-yield manufacturing.

Laser technology is a cutting-edge process with a unique photothermal response, precise site selectivity, and remote controllability. Laser technology has recently emerged as a novel tool in the semiconductor, display, and thin film industries by providing additional capabilities to existing high-vacuum equipment. The in situ and in operando laser assistance enables using multiple process environments with a level of complexity unachievable with conventional vacuum equipment. This broadens the usable range of process parameters and directly improves material properties, product precision, and device performance. This review paper examines the recent research trends in laser-assisted vacuum processes (LAVPs) as a vital tool for innovation in next-generation manufacturing processing equipment and addresses the unique characteristics and mechanisms of lasers exclusively used in each study. All the findings suggest that the LAVP can lead to methodological breakthroughs in dry etching, 2D material synthesis, and chemical vapor deposition for optoelectronic devices.

Influence of the laser position in laser-assisted WAAM process on weld bead shape and surface properties

The lateral use of the laser in laser-assisted WAAM processes, resulting in a directional dependence, can influence the bead shape and the bead surface. The influence of the laser position on the weld bead is investigated. Beads with different laser positions are applied and the height and width as well as the waviness of the beads are evaluated. In addition, claddings are welded and the waviness is measured. The waviness along the beads ranges from 8.77 to 34.66 µm, and no significant correlation with the welding direction could be determined. For the bead shape, the differences in height range from 3.54 to 3.90 mm and in width from 8.20 to 8.89 mm. Based on the results, a dependence on the laser position for surface properties and weld bead shape becomes clear.

Elastic electron-proton scattering in the presence of a circularly polarized laser field

Owing to recent advances in laser technology, it has become important to investigate fundamental laser-assisted processes in very powerful laser fields. In the present work and within the framework of laser-assisted quantum electrodynamics, electron-proton scattering was considered in the presence of a strong electromagnetic field of circular polarization. First, we present a study of the process where we only take into account the relativistic dressing of the electron without the proton. Then, in order to explore the effect of the proton dressing, we fully consider the relativistic dressing of the electron and the proton together and describe them by using Dirac–Volkov functions. The analytical expression for the differential cross section (DCS) in both cases is derived at lowest-order of perturbation theory. As a result, the DCS is notably reduced by the laser field. It is found that the effect of proton dressing begins to appear at laser field strengths greater than or equal to 1010 V cm−1 and it therefore must be taken into account. The influence of the laser field strength and frequency on the DCS is reported. A comparison with the Mott scattering and the laser-free results is also included.

Literature survey to the materials used in laser-assisted additive manufacturing processes for the production of nuclear materials

Literature survey to the materials used in laser-assisted additive manufacturing processes for the production of nuclear materials

Quest for New Data: Ionizing Radiation Metrology in the Presence of Laser-Assisted Scattering Processes

Radiation metrology is crucial in space, for instance in monitoring the conditions on-board space vehicles. The energy released in matter by ionizing radiation is due to the atomic and molecular ionization processes, which have been investigated for several decades from both a theoretical and an experimental point of view. Electronic excitation and ionization cross-section are of particular interest in radiation physics, because of their role in the radiation–matter interaction process. Recently, experimental findings have shown that the interplay with a laser field can strongly modify the electronic interaction probabilities and emission spectra. These phenomena are still not completely understood from a theoretical point of view, and the available empirical data concern a few, simple atomic species. We represent a possible dosimetric effect of the interaction with laser light, inferring from experiments the characteristics of laser-assisted cross-sections. Using a Monte-Carlo calculation for simulating the micro-dosimetric aspects of the irradiation of a simple geometry, we show the need of new experimental data and more detailed theoretical approaches to these phenomena in complex molecular systems.

Laser Assisted Fabrication of Surface Oxide Nanostructures for Photovoltaic Applications

The paper discusses the application of laser-assisted processes for synthesis of oxides nanoparticles (NPs) and their assembling into the nanostructured thin films. The study of the laser parameters influence on the NPs formation and thin film deposition conditions allowed to find optimal conditions for the formation of ZnO, CuO colloidal NPs as well as ZnO/CuO nanostructured thin films suitable for practical applications. The morphology, structure, as well as electronic and optical characteristics of the formed oxide nanostructures were studied and their potential optoelectronic and photovoltaic applications are discussed.

Fabrication of Microwave Devices Based on Magnetic Nanowires Using a Laser-Assisted Process.

This paper compares two laser-assisted processes developed by the authors for the fabrication of microwave devices based on nanowire arrays loaded inside porous alumina templates. Pros and cons of each process are discussed in terms of accuracy, reproducibility and ease of fabrication. A comparison with lithography technique is also provided. The efficiency of the laser-assisted process is demonstrated through the realization of substrate integrated waveguide (SIW) based devices. A Nanowired SIW line is firstly presented. It operates between 8.5 and 17 GHz, corresponding to the first and second cut-off frequency of the waveguide, respectively. Next, a Nanowired SIW isolator is demonstrated. It shows a nonreciprocal isolation of 12 dB (corresponding to 4.4 dB/cm), observed in absence of a DC magnetic field, and achieved through an adequate positioning of ferromagnetic nanowires inside the waveguide cavity.

Calculation of specific heat of polymers using molecular dynamics simulations

Precise evaluation of the heat capacity at constant pressure (Cp) of polymers during rapid heating and cooling is required to predict and optimize the performance of polymer products after laser-assisted manufacturing processes. However, currently available experimental methods are not capable of determining Cp at rapid temperature fluctuations. Molecular Dynamics (MD) simulations could be useful to evaluate Cp under such conditions. In order to determine the efficacy of MD simulation, Cp at the room temperature of various well-studied polymers (polyethylene, polyethylene terephthalate, polypropylene, polystyrene, polyvinyl chloride, and polytetrafluoroethylene) were computed with the MD simulations using General Amber Force Field (GAFF) potentials. The simulated Cp values for these polymers were found to be higher than experimental values. Possible reasons for the disparity in Cp values are discussed, and suggestions for extracting accurate Cp values are provided.

“Industrial applications of lasers” at the University of Vigo as legacy of Professor Mariano Pérez-Amor

From the early days in a modest laboratory equipped with a low power CO2 laser, more than thirty years have gone under the direction of Prof. Mariano Pérez-Amor first and Prof. Juan Pou Saracho later, transforming the initial status of the young research group to the current one under a watchword: supportive team work. During these years we have diversified our research areas, including processes at the nano-scale, processing and synthesizing materials of diverse nature, as well as introducing and patenting new laser-assisted processes and opening horizons to some laser applications well-established in the industry. All of it, with the commitment of our founder, the team that he has formed, in constant renewal, and the collaborating researchers in other national and international centers supported with public and private funding from different regional, national and European organizations.This paper is a modest tribute to Prof. Mariano Pérez-Amor who passed away on January 14th 2018.

Bimetallic clustered thin films with variable electro-optical properties

The drop deposition of colloidal nanoparticles was performed from water-based colloidal solutions. The proposed procedure is based on the agglomeration of colloidal particles in laser-assisted evaporation processes. The evaporation process was resulted in the formation of clustered thin films on a glass substrate. In the experiments with bimetallic Au:Ag solutions, the clustered films are grown, the formation of the clustered films with the average height of 100 nm was achieved. Optical properties of the deposited structures were investigated experimentally. It is shown that the obtained films may become transparent and its properties are defined by its morphology.

Experimental Investigation of Effect of the Laser-Assisted Finish Turning of Ti-6Al-4V Alloy on Machinability Indicators

In this paper, the experimental studies of the finish turning of Ti-6Al-4V titanium alloy with the laser-assisted machining were described. For the tests, a cemented carbide tool was used. The influence of the laser heating on the microstructure of Ti-6Al-4V titanium alloy for kinematics corresponding with the turning process was determined. For a laser scanning rate of 80 m/min and laser power 1200W, the maximum depth of the melted zone was about 50 μm. The beneficial effect of laser assisted machining on components of the cutting force was established. For a cutting speed of 80 m/min, feed rate 0.1 mm/rev, depth of cut 0.25 mm and laser power 1200 W, over 60% reduction of the tangential components of cutting force was observed. The chip-breaking effect for the conventional and the laser-assisted processes was determined. Roughness parameters of the surface after the conventional and laser-assisted turning are compared.

Plasmon effects in photoemission

Recently, we observe an increasing interest in the laser-assisted processes that take place at the solids surfaces or at the interfaces of semiconductor heterostructures. These processes are affected by the plasmon effects induced by the interaction of quasi-free electrons in solids with laser fields. The plasmon effects lead to a significant enhancement of the oscillating in time electric field in a vicinity of the surface. The latter strongly modifies processes such as the high-order harmonic generation from atoms passing close to the surface, the electron photoemission from metal tips or the tunneling processes in semiconductor heterostructures. In our paper, we focus on the photoemission phenomenon accounting for the space-dependence of an oscillating in time, effective electric field created at the surface.

Atomic processes in bicircular fields

Various laser-induced and laser-assisted processes in atoms exposed to bicircular fields are investigated. The strong-field ionization process is exemplified by the direct and by the high-order above-threshold detachment of negative fluorine ions both for corotating and counterrotating bicircular fields. The symmetries of the electron distributions in the momentum plane are analyzed in detail. The results for laser-assisted electron-ion recombination and for high-order harmonic generation are presented for the bicircular field with counterrotating components.

Laser-assisted hybrid processes: A review

Today, hybrid processes have a great influence on various material process fields due to factors such as improvements in the machinability and reductions of process forces. Also, the development of hybrid processes represents a new opportunity for the growth of manufacturing technology. Hybrid processes are developed to enhance the advantages of individual processes. The effect of hybrid processes is better than the sum of the advantages of a single process. Many researchers have studied a number of approaches to combine various manufacturing processes. Specifically, since the development of the laser, it has been applied in various engineering fields. Moreover, interest in laser and non-laser hybrid processes is recently increasing in various industries. The laser is a type of non-contact thermal energy technology and is used in material processing. The laser heat source can be used for the heating and preheating of various materials. In this paper, the laser is selected as an energy source and laser-assisted hybrid processes over the past five years are reviewed, including those related to machining, welding and coating processes. The last part of this paper discusses the trends in future research on laser-assisted hybrid processes.

Critical analysis of friction stir-based manufacturing processes

In this study, a detailed analysis of friction stir-based processes that can significantly contribute to joining of materials and surface property enhancement has been completed. Past, present, and future projections, advantages and disadvantages, technological barriers, and drawbacks of these processes have been given. Detailed explanations of the recent developments of friction stir-based processes and main components are given. Potential industrial applications have been assessed and evaluated using economic and technological considerations. In industrial applications, friction stir-based processes can be used in conjunction with additive processes such as laser-engineered near net shaping, thermal spraying and laser-assisted direct metal deposition processes. Developments in friction stir-based processes have led to improved metallurgical and mechanical properties such as microstructure modification, refinement, homogenization, surface cladding, corrosion, fatigue, wear, and hardness of metallic materials. The results of the study conclusively predict that reasonable costs and improved properties of processed materials will lead to a substantial increase in the use of friction stir-based processes.