Optimization Of Laser Processing Research Articles

Optimization of 12Х18Н9Т-Steel Processing by Ring Laser Beams

Using the MOGA genetic algorithm built into the DesignXplorer module of the ANSYS Workbench program, optimization of laser processing of 12Х18Н9Т-steel by annular beams has been performed. The calculation of temperature fields has been carried out taking into account the dependence of the thermophysical properties of the material on temperature by the finite element method in the ANSYS Workbench program. A regression model has been obtained for processing 12Х18Н9Т-steel by annular laser beams using a face-centered variant of the central compositional plan of the experiment. The power density and duration of laser radiation pulses, the outer and inner diameters of the laser beam in the processing plane were used as variable factors. The penetration depths of the material and the maximum temperatures in the laser processing zone were used as responses. The influence of processing parameters on the penetration depths of the material in the laser impact zone and the maximum temperature values has been evaluated. It has been established that the depth of penetration of the material and the maximum temperatures are most affected by the power density of laser radiation. Optimization of laser processing of 12Х18Н9Т-steel by annular beams was carried out by setting the limiting values of the maximum tempe-rature in the processing zone for three variants of the minimum penetration depth. The parameters obtained as a result of optimization using the MOGA algorithm and the parameters obtained as a result of finite element modeling are compared. The maximum relative error of the results when determining the maximum temperatures did not exceed 1 % and when determining the maximum penetration depths did not exceed 6 %.

Realizing high strength and toughness of gradient high-entropy alloy coating by in-situ interface reaction of FeCoCrNi/FeCoCrAl

In the pursuit of high performance development of alloy materials, it is a long-standing problem to enhance strength and toughness simultaneously. In this study, by selecting heterogeneous high-entropy alloy (HEA) materials and conducting structural design and laser process optimization, an external-hard internal-tough HEA composite coating with an in-situ dual-phase interface layer was successfully prepared. For the microstructure, the phase structures at the top, middle, and bottom of the coating are single-phase body-centered cubic (BCC), dual-phase BCC/face-centered cubic (FCC), and single-phase FCC, respectively. Among them, the dual-phase interface layer gives priority to the FCC phase (79.4 %), supplemented by the BCC phase (16.7 %). In terms of mechanical properties, the hardness of the coating from the top to the bottom is 9.85 GPa, 5.53 GPa, and 4.86 GPa, respectively. As demonstrated by employing the three methods of K, H/E, and H3/E2, the HEA composite coating has favorable integrated characteristics of strength and toughness. Meanwhile, due to the in-situ generated dual-phase interface layer, the structural and performance differences between the high-hardness layer and the high-toughness layer are effectively alleviated, and the stress concentration is reduced, thus stabilizing the overall structure of the coating. Hence, the HEA composite coating designed and prepared in this study possesses better erosion resistance (mass erosion rate = 0.141 × 10−3 g.cm−2 s−1), tribological properties (wear rate = 0.30 × 10−6 mm3/(N · m)), and impact resistance (AKU = 103.5 ± 2.8 J). The study results can provide new methods and new theories for new HEA composite coatings with integrated strength and toughness, and can be used in guiding the development and design of similar HEA composite coating structures.

Numerical simulation and experimental analysis of machining morphology with pulsed laser

In this study, simulation and experimental studies are used to evaluate the temperature field distribution and process law for the pulsed laser processing of stainless steel. The numerical simulation is based on the theory of heat transfer. The temperature field distribution and change process of the stainless steel surface under the influence of laser is explained subjectively, and the morphology evolution law of stainless steel during the entire process is studied. The influence of insufficient laser spot overlap ratio and the variation of laser power on the machining quality is analyzed by comparing with the experimental results. The evolution law of machining morphology and size with the laser incident angle, scanning speed, repetition frequency, and laser power are evaluated. The results provide theoretical support for determining the high-quality processing of stainless steel by a pulsed laser, which can be used for the parameter optimization of laser processing, such as metal material cutting, surface microstructure preparation, and two-dimensional code marking.

Laser micro-texture formation mechanism based on modified heat-mass transfers and hydrodynamic models

Laser surface texturing is considered as a novelty and feasible technology to fabricate some micro-feature due to the non-contact, high precision and processing efficiency. However, it is difficult to deeply understand the material removal mechanism and predict the surface topography due to a confined heat-affected zone and extremely short time in the laser machining process. In this research, based on the mixed phase theory and level-set method, a modified heat-mass transfer and hydrodynamic model was proposed for deeply analyzing the influence of various physical factors such as recoil pressure, buoyancy, surface tension, gravity and thermal-mass transport on the material removal and micro-texture topography evolution at a mesoscale level. The analysis of hydrodynamic behaviors and temperature fields of the molten pool indicated that the melts sputtering and molten pool expansion caused by the recoil pressure was the dominant factor responsible for micro-texture formation during laser action. The reflux induced by the surface tension and gravity as well as the residual effect of the melts flowing upward were the main factors of the occurrence of a vortex during the molten pool cooling. Finally, the effects of laser parameters on the micro-feature topography were discussed based on the experiments and simulation model. The diameter and depth of the hole as well as the width and depth of the groove gradually increased with increasing frequency and pulse duration. The laser moving speed had less effect on the width of the groove, but it had great effect on the surface roughness of the groove. This work can be beneficial to understand the material removal mechanism and provide a guide for the parameters optimization of laser processing at a mesoscale level.

Surface defect detection and prediction in carbide cutting tools treated by lasers

Laser surface engineering of cutting tools is used to improve the performance of cutting processes via altering the material interaction between the tool surface and workpiece. Laser processing applied to cemented carbide cutting tools can induce various thermal and mechanical surface defects including porosity, splatter, cracks, balling, spherical pores, voids, and dissociation. Those defects could be detrimental to the integrity of the tool, therefore parametric optimization is crucial to limit and control possible post-processing defects. This study aimed to identify and classify surface defects in post laser processed carbides to better understand the relationship between parameters and resultant surface integrity. A region convolutional neural network (R-CNN) was trained for identification and classification of these surface defects using scanning electron microscopy images (SEM) as inputs. The R-CNN provided a quantitative analysis of each defect with an average accuracy of 91%. Using the data from the R-CNN matched with the laser parameters, a back propagation neural network (BPNN) was trained to act as a predictive network. The network predicts the number and proportion of defects when the tool grain size, roughness and laser parameters are entered. The accuracy of this predictive network was 96.6%. The effect of individual laser parameters on the surface integrity is estimated by this method, enabling the optimization of laser processing in cutting tools. For the first time this can be used to predict tool performance based on tool’s surface integrity.

The Stability of Laser Hardening Structures to Softening During Heating

Structural and phase changes occurring in laser-hardened steels after tempering at different temperatures are considered. It is shown that the optimization of laser processing and subsequent tempering allows to increase the heat resistance of steels 50-120°C by maintaining a high density of defects in the crystal structure and appearance of the uniform allocation of dispersed carbide particles. It is established that for the laser-irradiated metal, from the energy point of view, it is not the formation of ε-carbide during tempering, but the deposition of carbon atoms and alloying elements on structural imperfections with further formation of carbides according to the scheme: carbon in solid solution → carbon associated with defects → carbide on defects of the crystal structure.

Application of fiber laser technology to repair of thin-walled component and laser process optimization

Application of fiber laser technology to repair of thin-walled component and laser process optimization

Optimization of Laser Processing in the Fabrication of Stents

Stents are commonly inserted into coronary arteries for treating cardiovascular diseases. Nonetheless, the process of manufacturing metal stents is challenging owing to the geometric design, the optimization of machining methods and the materials involved. Fiber lasers were used as the laser cutting technology for cutting stents. The experiment revealed the importance of precise technical parameters, including the lens’ focal length, focus position, pulse frequency, cutting speed and pulse width. These parameters strongly influence the kerfs width and the quality of the cutting seam surface. Our results indicate that the width of the kerfs increases with an increase in the pulse frequency and pulse width, whereas it decreases or shows minimal change at higher cutting speeds. The surface roughness for stent laser cutting was Ra 43.5nm, which essentially meets the design requirement for further performance evaluation. Finally, high-quality cutting of a 316LVM stainless steel vascular stent was achieved. [doi:10.2320/matertrans.M2012188]

Distributed actuators deformable mirror for adaptive optics

In this paper we present a Modal Deformable Mirror (MDM) based on the continuous voltage distribution over a resistive layer. This Deformable Mirror (DM) can correct spherical aberration and coma in addition to the low order aberrations (defocus and astigmatism) using just nine contacts thus limiting the requirements of high voltage lines with respect to state of the art devices. We demonstrate the advantages of this technology presenting a mathematical description of the mirror, an experimental characterization and a comparison with discrete actuator DMs. In order to demonstrate the effectiveness of this design in sensorless applications we present the experimental results for image sharpening optimization. The easiness of use suggests that it can be useful for many applications from imaging systems to laser process optimization.

Process Optimization of Laser Processing in Terms of System-synergistic analysis

The article considers the approaches to the problem of optimization of laser processing for decision of actual tasks of technology of mechanical engineering. The authors developed the technique of optimization of the laser processing technology, based on synergetic method of an estimation of basic parameters. Optimization results on basis of recurrence relationship allow formulating of requirements for technological efficiency of the laser processing.

Calculation of thermal processes upon the laser modification of HTSC ceramics aimed at increasing the critical current

A mathematical model for the heating of a surface layer of HTSC ceramics by a CW laser beam scanned at a constant rate is considered. The calculated depths of the molten region are presented for the heating of the Bi(2223) ceramics by a CW CO2 laser. The theoretical results are in reasonable agreement with the experimental data. The calculations can be used for the optimization of laser processing of superconducting ceramics aimed at increasing the critical current density.