Effects Of Different Laser Parameters Research Articles

Real-time microwave transmittance variation of glass fiber composites subjected to laser irradiation

Laser irradiation may have a significant impact on the microwave transmission properties of glass fiber composites. In this study, a two-dimensional microwave transmission transient model of glass fiber composites during the complete laser irradiation process was developed. The numerical results indicate that carbonization during irradiation causes a significant increase in dielectric loss, thus resulting in a decrease in transmittance. After irradiation, the dielectric loss decreased due to the decrease in temperature, which, in turn, led to an increase in transmittance. The increased transmittance after cooling was lower than the original value due to the generation of pyrolytic carbon with a high dielectric loss. The numerical results were verified by conducting an experiment wherein the microwave transmittance of glass fiber composites was measured in real time before, during, and after laser irradiation. In addition, the effects of different laser parameters on the real-time microwave transmittance during laser irradiation were investigated experimentally and numerically. For the same total energy, a laser with a high power density and short irradiation time had a more significant effect on the attenuation of transmittance.

Hysteresis phenomenon in single electron nonlinear Thomson scattering in tightly focused linearly polarized lasers caused by collision position changes

The collision between high-energy electrons and linearly polarized laser pulses is systematically studied, which has significant application value. The effect of different laser parameters on the spectrum and power angular distribution has been analyzed. The maximum transverse amplitude of the electron motion track changes as one moves farther away from the focal point acting as the electronic initial position. Concurrently, an extensive examination of the off-axis properties of the electron is carried out. As the form of scattering changes from linear to nonlinear, the angular radiation of its power distribution exhibits intriguing characteristics. We found the ‘hysteresis’ phenomenon of the radiation characteristics. Our research can serve as a useful resource for comprehending and using laser electron interactions.

Effect of Different Laser Parameters on Surface Physical Characteristics and Corrosion Resistance of 20 Steel in Laser Cleaning

The rusting of metals brings huge losses to the industry every year, and post-treatment of rusted metals to restore their properties to the initial state is a hot topic of current research. In particular, 20 steel, which is widely used in various structural components such as ships, is prone to oxidation in atmospheric environment. Therefore, in this study, a nanosecond pulsed laser was used to remove the rust layer on the surface of 20 steel. The effects of different energy densities and spot overlap rates on the roughness, surface morphology, chemical composition, microhardness and corrosion resistance of the rust layer were analyzed. The results showed that the best cleaning effect was achieved at an energy density of 4.26 J/cm2 and a spot overlap rate of 75%. Under these conditions, the rust layer was completely removed without damage to the substrate, and it even improved the corrosion resistance of 20 steel. At energy densities of 1.42 J/cm2 and 2.84 J/cm2, the rust layer was not completely removed, while at 5.68 J/cm2, the rust layer was removed but the substrate was damaged. In addition, the mechanism of rust removal and substrate damage is discussed.

Rapidly screening out refractory metallic alloys with high glass-forming ability by laser surface remelting

Compared with conventional metallic glasses, refractory metallic glasses (RMGs) with a mass of refractory element(s), high glass-transition temperature (Tg) and outstanding mechanical properties (like ultrahigh strength, high hardness and good wear resistance) exhibit fascinating potential applications in high temperature field. However, the development of RMGs is painfully slow, and one of the key problems is the lack of rapid and convenient way to screen out high glass-forming refractory alloys. In this study, a method for rapid evaluation of glass forming ability (GFA) based on laser surface remelting was provided. The high-efficiency screening-out method was validated in a classical glass-forming model system of Ni–Nb binary refractory alloys. The effects of different laser parameters on the glass formation and phase evolution were investigated by experimental analysis and finite element simulation. By correlating thermal history of the laser treatment with glass formation, the alloys with high GFA in Ni–Nb system was screened out rapidly. The screening-out efficiency of the novel method can be improved one order of magnitude, compared with that of the conventional techniques, and the materials cost can be reduced, especially for RMGs. The revealed formation mechanism of glassy and crystalline phases in time and spatial distributions influenced by thermal history under multi-scanning laser treatment can provide a significant insight in the construction of the bulk-metallic-glass materials and the related composite ones by laser additive manufactory.

Preliminary tests on additive-manufactured Al-Sc specimens for the setup of a numerical model for Laser Shock Peening

Aluminum-Scandium alloys offer a great potential in aerospace applications due their high corrosion resistance and improved strength properties. Furthermore, these alloys have been qualified for laser additive manufacturing (AM), producing parts with static strengths rivalling their conventionally manufactured counterparts. However, laser processing also results in large residual stresses that can severely affect fatigue properties and result in geometric distortion. A proven method for reducing the fatigue-related problems in metallic structures is to drive compressive residual stresses into the affected area by means of Laser Shock Peening (LSP). This surface treatment is very effective in bulk structures, improving life performances of fatigue-sensitive aeronautical components, such as jet engines turbine blades or helicopter gearboxes. On the other hand, quite a limited number of studies has been presented on the effect of LSP on fatigue crack growth in thin components and laser AM structures. This work presents first the results of preliminary tensile tests on additive manufactured Al-Sc specimens. The tensile strengths of as-built and heat-treated samples are compared. Then, a reliable and computationally time-effective numerical model of laser peening is reviewed, referring to case studies investigated earlier. In view of applying LSP to additive manufactured Al-Sc components, the effects of different laser parameters and geometries are discussed. Finally, the possible drawbacks of the LSP treatment are addressed, in order to exploit its full potential in increasing the fatigue life of AM components.

Investigation of temperature field for the in-situ fabrication of particle-reinforced alumina ceramics coating via laser induction

Laser-induced aluminum thermal reaction was used to prepare a new iron particle reinforced alumina ceramic coating on the surface of TC4 titanium alloy. The aluminum thermal reaction heat generation in the on-line laser melting and coating process is fast and not easy to control, and its effect on the coating quality is unknown and usually neglected in the preparation process. In this paper, a numerical simulation model of a dual heat source containing the reaction heat is established. The temperature field of the new Al2O3-Fe composite coating and the thermal stress distribution pattern of the components were investigated. The effects of different laser parameters on the maximum molten pool temperature, thermal deformation and coating morphology of TC4 titanium alloy substrates were also discussed. The accuracy of the model is verified by the joint temperature acquisition experiment, which provides a reference for the selection of laser cladding process parameters. The simulation results show that the maximum temperature and volume of the melt pool increase significantly due to the coupling of the induced reaction heat, and the maximum temperature is not inversely proportional to the laser scanning speed, but directly proportional. The residual stress analysis shows that the residual stress on the coating is mainly the tensile stress along the laser cladding direction, which is the main reason for the transverse crack of the single layer coating after laser cladding.

Biphasic dose response in the anti-inflammation experiment of PBM.

Non-invasive laser irradiation can induce photobiomodulation (PBM) effects in cells and tissues, which can help reduce inflammation and pain in several clinical scenarios. The purpose of this study is to review the current literature to verify whether PBM can produce dose effects in anti-inflammatory experiments by summarizing the clinical and experimental effects of different laser parameters of several diseases. The so-called Arndt-Schulz curve is often used to describe two-phase dose reactions, assuming small doses of therapeutic stimulation, medium doses of inhibition, and large doses of killing. In the past decade, more and more attention has been paid to the clinical application of PBM, especially in the field of anti-inflammation, because it represents a non-invasive strategy with few contraindications. Although there are different types of lasers available, their use is adjusted by different parameters. In general, the parameters involved are wavelength, energy density, power output, and radiation time. However, due to the biphasic effect, the scientific and medical communities remain puzzled by the ways in which the application of PBM must be modified depending on its clinical application. This article will discuss these parameter adjustments and will then also briefly introduce two controversial theories of the molecular and cellular mechanisms of PBM. A better understanding of the extent of dualistic dose response in low-intensity laser therapy is necessary to optimize clinical treatment. It also allows us to explore the most dependable mechanism for PBM use and, ultimately, standardize treatment for patients with various diseases.

Pt nanoparticle decoration on femtosecond laser-irradiated SnO2 nanowires for enhancing C7H8 gas sensing

In this study, we have fabricated a sensitive and selective toluene gas sensor based on SnO2 nanowires (NWs) using the femtosecond (FS) laser irradiation and Pt nanoparticle (NPs) decoration. The effects of different laser parameters, including wavelength, laser pulse energy, hatch distance, and scan speed, are investigated on the gas-sensing properties. The FS laser irradiation-induced embossing surface is found to be a dominant factor in determining the gas-sensing behavior, which provides more oxygen absorption sites, resulting in an increase in the width of the electron depletion layer (EDL) and the sensor response. The Pt decoration on the FS laser-irradiated SnO2 NWs developed additional EDL, which further enhances the sensor response. The Pt-decorated and FS laser-irradiated SnO2 NWs gas sensor shows a high selectivity toward C7H8 owing to the catalytic effect of Pt toward toluene, where the sensor response to 50 ppm C7H8 is as high as 53 at 300 °C. Based on X-ray photoelectron spectroscopy and transmission electron microscopy analyses, a gas-sensing mechanism of the Pt-decorated and FS laser-irradiated SnO2 NWs gas sensor is proposed. This study highlights a promising combination of Pt decoration and FS laser irradiation for the realization of reliable toluene gas sensors.

Ultrafast laser ablation of copper with GHz bursts: A numerical study on the effects of repetition rate, pulse number and burst fluence on ablation efficiency and heat-affected zone

Ultrafast laser burst ablation (ULBA) with high repetition rates up to GHz has emerged as a promising method for improving ablation efficiency and reducing heat-affected zone (HAZ). However, the effects of different laser parameters are not well understood. This article presents a numerical study by an improved two-temperature model on the influences of repetition rate, pulse number and burst fluence on ablation efficiency and HAZ in ULBA of copper. Due to thermal accumulation, increasing the repetition rate enhances the maximum ablation efficiency, by over 150% at 3456 MHz. Interestingly, large pulse numbers also assist this effect by extending the period of thermal accumulation. However, if the burst fluence is too low, increased pulse numbers will reduce the ablation efficiency due to insufficient pulse fluences. Burst duration and fluence are determined to have the greatest impact on HAZ thickness. To minimize HAZ, the burst duration needs to be short, by raising repetition rates or reducing pulse numbers, to decrease the thermal diffusion time. The dependences of ablation optimum and threshold fluences on pulse numbers and repetition rates are analyzed and summarized in simple formulae. This study unveils the impacts of laser parameters in ULBA and provides guidelines for ablation efficiency and HAZ optimization.

Numerical analysis of laser melting of alumina coated steel

This article presents a numerical investigation of laser melting of alumina coated steel specimen. After the laser is irradiated, the specimen is heated and the temperature increases. When the temperature reaches the melting temperature, a melt pool is generated. However, the melting temperature of alumina and steel are different. Therefore, it is interesting to observe the progress of melt front in the two layers of materials in this article. As the laser pulse is repetitive in nature, some region gets solidified which is already melted during the cooling period of the irradiation. So, the effect of different laser parameters to control the growth of the melt pool is discussed in detail with a numerical model. The temperature field is determined from the energy and fluid flow equation. Finite Volume Method is used obtain the algebraic equations from governing equations. The relevant equations are now solved using Tri-Diagonal Matrix algorithm. The detail position of the interface can be known using the enthalpy method.

Skin, Light and their Interactions, an In-Depth Review for Modern Light-Based Skin Therapies

Light-based therapies, including laser, have evolved over the last decades in the dermatology and cosmetic fields. Practitioners should have a deep understanding of the mechanism of action and the effect of different laser parameters on treatments outcomes and safety profiles. Moreover, practitioners would not be able to improve the existing laser treatment protocols or develop new ones without understanding the light fundamentals and different laser-skin interactions. This review article attempts to bridge the theoretical concepts of laser and skin anatomy with the practical applications of light-based treatments.

Tribological behaviors of high-hardness Co-based amorphous coatings fabricated by laser cladding

Co-based metallic glasses with ultrahigh strength and high microhardness are regarded as ideal surface-coating materials to significantly improve hardness and wear resistance of substrate materials. In this paper, a Co-based amorphous powder with high glass-forming ability was prepared by gas-atomization technique. Then a large-area Co-based amorphous coating was fabricated from the powder by laser cladding technology. The effects of different laser parameters (i.e., laser scanning speed and operating voltage) on glass formation of the amorphous coating were investigated. Furthermore, the thermal properties, microhardness and wear resistance of the amorphous coating produced with an optimal laser parameter were evaluated. The results indicate that the Co-based amorphous cladding layer exhibits extremely high microhardness of ~14.9 GPa, which can significantly improve the wear resistance of the substrate. A complex wear-failure mechanism of the Co-based coating is clarified as a mixture role of abrasive- & fatigue-wear, oxidation wear and adhesive wear proofed by microstructural and element-distribution analysis of various worn surface.

Simulation of the laser-material interaction of ultrashort pulse laser processing of silicon nitride workpieces and the key factors in the ablation process

Understanding the laser ablation mechanism is highly essential to find the effect of different laser parameters on the quality of the laser ablation. A mathematical model was developed in the current investigation to calculate the material removal rate and ablation depth. Laser cuts were created on the workpiece with different laser scan speeds from 1 to 10 mm s−1 by an ultrashort pulse laser with a wavelength of about 1000 nm. The calculated depths of laser cuts were validated via practical experiments. The variation of the laser power intensity on the workpiece’s surface during laser radiation was also calculated. The mathematical model has determined the laser-material interaction mechanism for different laser intensities. The practical sublimation temperature and ablated material temperature during laser processing are other data that the model calculates. The results show that in laser power intensities (IL) higher than 1.5 × 109 W cm−2, the laser-material interaction is multiphoton ionisation with no effects of thermal reaction, while in lower values of IL, there are effects of thermal damages and HAZ adjacent to the laser cut. The angle of incidence is an essential factor in altering incident IL on the surface of the workpiece during laser processing, which changes with increasing depth of the laser cut.

Laser surface hardening of SS316L

Laser surface hardening is one of the effective method to enhance the mechanical properties of localised surface area of engineering parts made of different types of steels and other metals like titanium etc. Laser surface hardening has many advantages over conventional hardening process like, self-quenching, very fast, control over energy input and localised hardening etc. This work presents the effect of different laser parameters on the micro hardness of SS316L after laser hardening. The experimental work was carried out using 30W Diode-pumped nanosecond (ns) pulsed laser. Design of Experiments One Variable at a Time (OVAT) approach was used for experimentation. Laser power, laser scanning speed, frequency and number of passes were the process parameters used for the experiments. Effects of these parameters over the micro hardness of the surface are described. Along with this, discussion of features of microstructures using optical microscope are done. It has been found that, there is around 25% increase in hardness after laser hardening. Hardened depth up to 400 microns was obtained.

Evolution of a Superhydrophobic H59 Brass Surface by Using Laser Texturing via Post Thermal Annealing.

To fabricate an industrial and highly efficient super-hydrophobic brass surface, annealed H59 brass samples have here been textured by using a 1064 nm wavelength nanosecond fiber laser. The effects of different laser parameters (such as laser fluence, scanning speed, and repetition frequency), on the translation to super-hydrophobic surfaces, have been of special interest to study. As a result of these studies, hydrophobic properties, with larger water contact angles (WCA), were observed to appear faster than for samples that had not been heat-treated (after an evolution time of 4 days). This wettability transition, as well as the evolution of surface texture and nanograins, were caused by thermal annealing treatments, in combination with laser texturing. At first, the H59 brass samples were annealed in a Muffle furnace at temperatures of 350 °C, 600 °C, and 800 °C. As a result of these treatments, there were rapid formations of coarse surface morphologies, containing particles of both micro/nano-level dimensions, as well as enlarged distances between the laser-induced grooves. A large number of nanograins were formed on the brass metal surfaces, onto which an increased number of exceedingly small nanoparticles were attached. This combination of fine nanoparticles, with a scattered distribution of nanograins, created a hierarchic Lotus leaf-like morphology containing both micro-and nanostructured material (i.e., micro/nanostructured material). Furthermore, the distances between the nano-clusters and the size of nano-grains were observed, analyzed, and strongly coupled to the wettability transition time. Hence, the formation and evolution of functional groups on the brass surfaces were influenced by the micro/nanostructure formations on the surfaces. As a direct consequence, the surface energies became reduced, which affected the speed of the wettability transition—which became enhanced. The micro/nanostructures on the H59 brass surfaces were analyzed by using Field Emission Scanning Electron Microscopy (FESEM). The chemical compositions of these surfaces were characterized by using an Energy Dispersive Analysis System (EDS). In addition to the wettability, the surface energy was thereby analyzed with respect to the different surface micro/nanostructures as well as to the roughness characteristics. This study has provided a facile method (with an experimental proof thereof) by which it is possible to construct textured H59 brass surfaces with tunable wetting behaviors. It is also expected that these results will effectively extend the industrial applications of brass material.

Analytical modeling of the heat-affected zone in laser-assisted milling of AerMet100 steel

Compared with conventional milling, laser-assisted milling (LAM) enhances the productivity of difficult-to-cut materials and is a green process due to the elimination of coolant. However, this heat-assisted process may induce a detrimental heat-affected zone (HAZ, generally referred to as phase transformation zone) in the workpiece. This paper presents an analytical model to predict the HAZ produced by laser heating in LAM of AerMet100 steel, in which the size of HAZ is determined by comparing the steady temperature field with the phase transformation temperature of workpiece material. A series of laser heating and LAM experiments are performed to validate the HAZ model. XRD technique is employed to analyze the microstructures in the heated and machined surface layers. Phase compositions and retained austenite content of each specimen are compared with those of the base material. The results indicate that the proposed model is feasible. In addition, the effects of different laser parameters on the HAZ are discussed. The size of the HAZ increases significantly with increasing laser power and decreases significantly with increasing feed speed. The HAZ width increases with the increase of laser spot size, and it appears the opposite change for the HAZ depth. This work can be applied to determine the process parameters in LAM that will yield no residual HAZ in the workpiece after machining.

Parametric optimization of pulsed laser ablation on stainless steel for improving corrosion resistance by Taguchi method

In the present study, pulsed laser ablation in liquid (PLAL) treatment has been optimised for ASTM 304/2B stainless steel using Taguchi method. PLAL experimental trials were carried out using fiber laser source by varying laser parameters include overlap rate, scanning speed, laser irradiation power and the number of laser pulses. The optimum laser parameters have been derived by considering the response which is corrosion potential of metal targets. Analysis of Variance (ANOVA) and signal to noise ratio are used to analyse the effect of different laser parameters on the responses. The laser irradiation power is the most dominant factors affecting the corrosion resistance of stainless steel in neutral solution; the overlap rate is the most significant impact corrosion resistance of metal in acidic solution. The responses of the optimized laser parameters obtained implementing the Taguchi method has been verified experimentally and hence supporting the accuracy of optimization of laser parameters under the given set of experimental conditions.

Microstructure and properties of LENS (laser engineered net shaping) manufactured Ni-Ti shape memory alloy

Successful attempt of laser deposition of a nitinol alloy is presented in this paper. The influence of the deposition velocity on the alloy microstructure and phase composition was investigated. Nine samples with different scanning velocities and layer thicknesses were manufactured using the LENS process. The effect of different laser parameters on the microstructure, secondary phase compositions and functional properties of the nitinol alloy was examined using optical microscopy, X-ray diffraction and DSC analyses. The microstructural characteristics, factors influencing the transformation temperatures and phase analyses are discussed to show the Ni-Ti alloy behaviour and great challenges in front of additive manufacturing applications for nitinol part manufacturing.

Use of high-energy laser radiation for surface preparation of magnesium for adhesive applications

This paper is intended to demonstrate how the parameters for the surface preparation of magnesium alloys for adhesive bonding can be optimized. The effects of different laser parameters are analyzed by using a combination of advanced sample preparation and ultra-high resolution scanning electron microscopy on a nanoscale level and a specific combination of mechanical tests on the macroscopic level. These data allow a discussion of the physical principles and the key parameters influencing the interaction of laser radiation with the magnesium surface.

Study of 3D Laser Cladding for Ni85Al15 Superalloy

Conditions of successful3D laser cladding for Ni based superalloy were studied. A high power Yb-YAG laser was used to create a molten pool on a stainless steel substrate into which Ni85Al15 powder stream was delivered to create 3D samples. The effect of different laser parameters on the structure and the intermetallic phase content of the manufactured samples were explored by optical metallography, microhardness, SEM, X-ray, and EDX analysis. The cladding of the Ni3A1 coating with small dilution into substrate can be obtained at the appropriate power density of about 2-8 J/mm2 under the laser scan velocity of 100-200 mm/min and the powder feed rate ∼ 3.8 g/min.