Optimal laser pre-sintering parameters are essential for reducing the surface roughness of laser melting samples. This paper investigates the impact of process parameters, including laser power, exposure time, line spacing, and point spacing, on surface roughness during the pre-sintering process. To achieve high-quality processing parameters, a response surface method (RSM) and a support vector machine (SVM) model optimized by the warp snake algorithm (SO) were established. The results indicate that both models possess strong predictive capabilities, with the SO-SVM model demonstrating superior optimization and generalization performance. The minimum surface roughness achieved through the SVM model optimized by the snake algorithm for the refined process parameters is 17.7 μm, which is lower than the 19.3 μm obtained using the response surface method. This study provides a reference for minimizing surface roughness, significantly reducing the trial-and-error costs in the machining process, and facilitating the production of higher quality machined parts.

This study investigates the relationship between key process parameters and dimensional accuracy in the fabrication of heat transfer plates for microfluidic heat exchangers using selective laser melting (SLM) technology, addressing issues of high cost and environmental pollution associated with traditional processing methods. Simulation and experimental validation were employed to analyze the effects of scanning distance, laser power, and scanning speed on part accuracy. The findings indicate that scanning distance has a negligible impact on the maximum displacement in the X and Y directions of the fabricated parts, whereas laser power and scanning speed significantly influence dimensional accuracy. Increasing the laser power, the maximum displacement value decreases first and then tends to be stable, since the length of plates in X direction is mainly affected by the edge molten pool, and in the Y direction, the length is mainly affected by the internal molten pool, and the maximum displacement first increases and then decreases. When the scanning speed is increased, the maximum displacement values in the X and Y directions decrease first and then increase. When the scanning distance is 60 m, the laser power is 165 W, and the scanning speed is 1 050 mm/s, plates with good dimensional accuracy can be fabricated.

TC17 titanium alloy samples were prepared by laser additive manufacturing technology. The effects of different solution aging temperature and heat treatment on microstructure, microhardness and tribological properties of TC17 titanium alloy were studied. The results show that the microstructure is transformed into coarse basket microstructure after solution aging treatment. With the increase of solution temperature, the primary α phase (αp) coarses gradually and the volume fraction decreases. After aging, the volume fraction of secondaryα phase (αs) precipitates from the β transition microstructure. With the aging temperature increasing, the thickness of the secondary α photographic layer increases obviously. After solid solution aging heat treatment, the microhardness increased obviously. After 840 ℃/1 h,AC+800 ℃/4 h,WQ+630 ℃/8 h,AC solution aging treatment, the microhardness reached the highest 447.6 HV, 14% higher than that of deposition, and higher than the forging standard (400 HV). The lowest average friction coefficient is 0.21, which is 34% lower than that of the deposition, and the wear amount is 3.4 mg at least, which is about 1/3 of that of the deposition (9.7 mg), showing good anti-wear performance.

To address the issue of inadequate wear resistance on the surface of 65Mn steel, a Fe60-WC composite coating was applied to 65Mn steel via laser cladding. The microstructure, phase composition, microhardness and friction and wear properties of the cladding layer were analyzed by SEM, EDS, XRD and wear tester. The results show that the maximum elastic modulus is 338.57GPa when the WC content is 30%. The microstructure of the cladding layer is mainly composed of fine equiaxed crystal, cellular crystal and columnar crystal. The strengthening phases, including WC, W2C, Fe3W3C, Fe6W6C are added in the phase of the composite coating. Meanwhile the microhardness of the cladding layer increases with the increasing of WC content. When the WC content is 40%, the average hardness is about three times of the matrix. With the increasing of WC content, the wear volume first decreases and then increases. When the WC content is 30%, the wear volume of the cladding layer is 68% of that of the Fe60 cladding layer.

The flow behavior of metal powder determines the quality and performance of molded parts, which is influenced by many factors such as powder properties, process parameters and nozzle structure. In order to improve the quality and performance of aluminum alloy powder laser clad molded parts, this paper introduces the research progress on the flow behavior of metal powder, and study the influencing factors such as powder properties, nozzle structure, process parameters, laser-powder coupling, coating layer structure, etc.; then compare with the material properties of aluminum alloy powder, summarize the research progress on the optimization of aluminum alloy powder flow behavior, and propose the laws and methods to improve the flow behavior of aluminum alloy powder. Finally, the existing problems and future research directions of aluminum alloy powder in the field of metal laser cladding are summarized and prospected. The research results are of great significance for improving the flow properties of aluminum alloy powder and promoting the application of metal powder in the field of laser cladding.

Laser surface modification technology improves material surface properties through the interaction of a laser beam with the material surface. This paper reviews the fundamental principles, current research status, and specific applications of laser cladding, laser shock peening, laser transformation hardening, and?laser texturing?in rail transportation. Laser cladding prepares various cladding layers on the surface of the substrate material to improve its properties or repair it, with a focus on controlling residual stresses in the surface and heat-affected zone and inhibiting crack initiation. Laser shock peening generates shockwaves in the subsurface of the material to increase its hardness and wear resistance, emphasizing the study of residual stress distribution patterns and fatigue fracture resistance mechanisms on the material surface. Laser transformation hardening creates high-hardness, low-toughness martensite on the material surface, improving surface hardness and wear resistance, with a focus on controlling residual stresses in the overlap zone. Laser texturing enhances surface properties by generating microstructures on part surfaces, prioritizing the optimization of process parameters to improve material surface quality. The paper concludes by suggesting directions for future development of laser surface modification technology, focusing on modification mechanisms and applied research areas.

Improving the bonding strength in carbon fiber-reinforced plastics (CFRP) is important for the increasingly growing functional use of these materials. Here, we investigated and compare the effects of a pulse CO2 laser-based surface treatment on the bond strengthening of CRFPs. The microscopic morphology, wettability, chemical composition and mechanical properties of the sample surface were characterized by using scanning electron microscopy, laser confocal microscopy, contact angle measurement, X-ray photoelectron spectroscopy and tensile testing machine. The mechanisms of different surface treatment methods on the bond strength of CFRPs were compared and analyzed. The results showed that the selective removal of resin and the induction of oxygen-containing functional groups on the surface layer of CFRP by the pulsed CO2 laser pretreatment were beneficial to the improvement of the bond strength between the adhesive joints. In addition, the gap structure formed between the fiber bundles after the pulsed CO2 laser pretreatment increases the contact area with the adhesive, which further improves the bonding performance of the CFRP surface.

The 2319 aluminium alloy samples were deposited by the Wire Oscillating Laser Additive Manufacturing (O-WLAM) process. The optimal parameters were obtained by optimizing process and the effect of deposition parameters on the formability were studied. The results show that the O-WLAM process significantly reduced the porosity and improved the process stability and formability compared to non-oscillating laser. The circular and “∞” oscillating mode obtained optimal formation. The minimum heat input is 12.4J/mm3 under circular oscillating. The smoothest deposition layer was obtained under the condition of 50% overlap ratio. With the increase of the number of deposition layers, the number of pores increases, and the forming is gradually stable. Finally, the deposition samples with good forming are obtained in the circular oscillating mode. Under the deposition state, the tensile strength and elongation in the XYZ direction are 246 MPa and 17.9%, 267 MPa, 8.9%, 266 MPa and 11. 1%, respectively. The anisotropy of the sample is not obvious.

Ti-Al composite coatings were fabricated on titanium alloy surfaces using laser cladding technology with a coaxial argon gas protection feeding mode. AlSi10 aluminum alloy powder served as the cladding material. The microstructure and properties of the composite coating were analyzed by SEM, XRD and EDS. Analysis revealed that the Ti-Al coatings are primarily composed of Ti, Al, Si, and V, with the atomic ratio of Ti to Al varying across different coating regions. The coating is composed of a variety of Ti-Al intermetallic compounds and elemental metals, the main intermetallic compounds are Ti0.6Al3V0.33, Ti7Al5Si12, TiAl3, TiAl2 and so on. The surface hardness of Ti-Al coating increases gradually from the substrate to the outside, and shows a decreasing trend after reaching the peak value at the joint of the coating. The maximum surface hardness at the joint of the coating is 788.3 HV, which is approximately 1.8 times of the matrix. When the laser power was 1 200 W and the scanning speed was 15 mm/s, the coating performance was better and the defects such as holes and cracks were the least.

This study investigates the weld formation of 20 mm thick EH36 high-strength steel using laser-arc hybrid welding. The weld forming characteristics under various laser powers, welding speeds, and wire feeding speeds were examined under a non-groove butt joint configuration. The arc and plasma characteristics during welding were analyzed and observed through high-speed photography. The results show that the fluctuation of weld penetration increases with the increase of laser power. The increase of laser power enhances the heating and radiation of welding wire, resulting in the acceleration of welding wire melting rate; Increasing the welding speed in a small range has a certain inhibiting effect on the back hump defect, and is conducive to reducing the degree of underfill; In high current welding, the concavity of the underfill decreases first and then increases with the increase of wire feeding speed. The arc force generated at higher wire feeding speed and the disturbance of the welding wire end to the weld pool are the main reasons for the underfill and poor formation of the weld.

This study investigates the weld formation of 20 mm thick EH36 high-strength steel using laser-arc hybrid welding. The weld forming characteristics under various laser powers, welding speeds, and wire feeding speeds were examined under a non-groove butt joint configuration. The arc and plasma characteristics during welding were analyzed and observed through high-speed photography. The results show that the fluctuation of weld penetration increases with the increase of laser power. The increase of laser power enhances the heating and radiation of welding wire, resulting in the acceleration of welding wire melting rate; Increasing the welding speed in a small range has a certain inhibiting effect on the back hump defect, and is conducive to reducing the degree of underfill; In high current welding, the concavity of the underfill decreases first and then increases with the increase of wire feeding speed. The arc force generated at higher wire feeding speed and the disturbance of the welding wire end to the weld pool are the main reasons for the underfill and poor formation of the weld.

The steel 42CrMo with thickness of 20 mm used in the planetary frame of heavy trucks, were welded by YLS-20000 fiber laser, and a single-pass penetration weld was achieved using a 20 kW fiber laser. By optimizing the defocus position, a well formed weld bead with no surface defects on both sides was obtained, and the microstructure and mechanical properties of the welding joints were analyzed under hot-rolled and tempered conditions. The experiment results show that melt-through welding of thick plates can be achieved in the case of negative defocusing. Under the condition of Tempered state base material, the microstructure of the weld zone and heat-affected zone were mainly martensite and bainite organization, the average tensile strength of the welded joint is 946 MPa, the average microhardness of the weld and the base material are 509 HV and 247 HV, the microhardness of the weld is significantly higher than the base material, but there is a softening phenomenon in the heat-affected zone. On the other hand, under the condition of hot-rolled state base material, the microstructure of the weld zone and heat-affected zone were mainly bainite organization, the average tensile strength of the welded joint is 781 MPa, the average value of microhardness of the weld and the base material were 506 HV and 219 HV, and the heat-affected zone is not significantly softened. The tensile specimens are fractured at the base material with hot-rolled and tempered state.2023-03-15

To address the industrial application requirements for rapid detection using Laser-Induced Breakdown Spectroscopy (LIBS), a swift classification method for heat-resistant steel utilizing portable LIBS equipment has been developed. The study involved six types of typical steel as experimental specimens. The classification models were respectively build based on the support vector machine (SVM), recursive feature elimination method combined with support vector machine (RFE-SVM) and linear discriminant analysis combined with support vector machine (LDA-SVM). The prediction accuracy and running time were used as the main evaluation indexes to evaluate each model, and the impact of input data and spectral feature dimension change on model performance was discussed. The results showed that the classification performance of the LDA-SVM model achieved the best performance, the accuracy of classification prediction was 95.28%, and the average time spent on classification was around 0.011 s. This research offers a methodological guide for the rapid classification of steel types using LIBS technology and lays the groundwork for the development of intelligent, rapid detection capabilities for portable LIBS devices.

This paper addresses the issue of error accumulation in Laser Inertial Simultaneous Localization and Mapping (SLAM) for large-scale environments in intelligent mobile devices by proposing a global constraint-based LiDAR SLAM algorithm for global environment map construction and localization. The algorithm consists of two parts: In the part of GNSS/IMU loose combination and LiDAR SLAM, 18 state parameters are estimated and solved by Kalman filtering method in the GNSS/IMU loose combination, and the GNSS/IMU combination positioning results are added as global constraints on the basis of traditional LiDAR/inertial SLAM. The cumulative errors of laser SLAM can be effectively reduced, the accuracy of positioning and mapping of mobile devices in large-scale and outdoor environment scenarios can be improved, and the global positioning information can be provided to realize seamless indoor and outdoor positioning. The results show that the errors in X, Y and Z directions decrease from 1.538 m, 0.345 m and 28.56 m to 0.536 m, 0.115 m and 0.851 m, respectively, after adding GNSS/IMU global constraints. The improvement in map construction and positioning accuracy, as well as the enhanced accuracy of point cloud mapping with repeated scans, confirms the effectiveness of the proposed algorithm.

Chewing gum is frequently found as physical evidence at crime scenes, necessitating an efficient method for gum category identification. The spectral data were normalized, followed by Principal Component Analysis for dimensionality reduction, selecting the top 100 principal components that accounted for a cumulative explained variance of 92.32%. After preprocessing, the entire dataset was divided into a 70% training set and a 30% test set. These sets were input into three machine learning models—Random Forest, Support Vector Machine, and K-Nearest Neighbors-combined with the Bayesian Optimization. After 100 iterations, the three models obtained optimal hyperparameter combinations, achieving classification accuracies of 98.03%, 88.72%, and 89.21%, respectively. Notably, the Bayesian Optimization - Random Forest model exhibited the highest classification accuracy, reaching 98.03%. K-fold Cross-Validation was subsequently applied to evaluate the classification accuracy and stability of the Bayesian Optimization-Random Forest model.

The structure function gradient lattice model exhibits superior compression and energy absorption properties, making it a popular choice in machinery, vehicles, aerospace, and other industries. Inspired by the geometry of butterfly wing and combined with rhombohedral regular dodecahedral monocytes, novel module is proposed in this study. Through parametric modeling, the monocytes are configured into lattice structures with uniform rod diameters, and gradient lattice structures are developed for comparative analysis. Utilizing photo-curing additive manufacturing with photosensitive resin, the structures are fabricated. Based on quasi-static compression experiments, the compression and energy absorption properties of the two lattice structures are investigated. The results show that both structures are densified by layer by layer collapse, but the crack propagation direction is opposite. The strain energy per unit volume of the two structures increases with the increase of rod diameter and geometric shape parameters. Notably, the gradient lattice structure demonstrates enhanced specific energy absorption while utilizing less material compared to the uniform lattice structure of the same size.

Aiming at the safety hazards and various collision problems in the construction process of transmission line tension release, this paper proposes a simulation method of transmission line tension release construction process based on laser point cloud. Firstly, the 3D point cloud data of the transmission line construction site is collected by airborne LiDAR, and the normalized elevation threshold filtering algorithm is used to segment the point cloud data to obtain ground and non-ground points, and the tower points are coarsely extracted according to the spatial dimensional features of the point cloud; then the point cloud of a single transmission tower is extracted with high precision by using the improved K-Means algorithm to cluster the center of the body elements; according to the laser point cloud, the laser point cloud is used to BIM technology is used to reverse model the target equipment and construction environment to build a digital 3D real-world model of the construction site; finally, the virtual prototype technology is used to establish a 3D real-world tension release system for transmission lines to simulate the dynamic process of tension release at the construction site and realize the construction process control, safety exploration and hazard point analysis. Results demonstrate that this method can effectively and accurately simulate the tension release construction process on-site with a numerical error within 5%. This provides reliable data support for precise construction, process control, and safety survey of tension release, indicating its significant engineering value.

To address the issue of inaccurate measurement data due to electromagnetic interference in traditional electronic and magnetic field angle sensors, this paper introduces a reflective optical fiber angle sensor. The Angle measurement is carried out by converting reflected optical fiber ranging into Angle, and the optical fiber Angle sensor model with STM32 as the main control is built. The voltage-angle characteristic curve is drawn by recording the corresponding relationship between the rotation Angle of the Angle sensor and its output voltage. However, due to the interference of the sensor′s mechanical structure and external environment, the nonlinear error of the volt-angle characteristic curve is relatively high. Therefore, the least square method is used to analyze the nonlinear error of the optical fiber Angle sensor. The nonlinear error of the sensor is calculated by the experimental simulation as 16.11%, indicating that the nonlinear error of the sensor is relatively high. So the nonlinear compensation model is established by using table lookup method. The experiment shows that the nonlinear error of the sensor can be reduced to 8.57% and increased by 7.54 percentage points by using table lookup method.

The “bare resonator” model is conventionally employed in the analysis of unstable resonators. However, for lasers with large active volumes, the saturation effect and non-uniformity of the gain medium significantly impact laser mode structures, output power, and beam propagation characteristics. In contrast to the "bare resonator," the "loaded resonator" model can provide output power predictions. In this paper, the “loaded resonator” model of unstable resonator with large Fresnel number was established, the characteristics of 2 kW RF-excited slab CO2 laser have been studied and been compared with the “bare resonator” model. There is a clear difference in the intensity distribution on the output plane, far field beam half-width and the energy contained in the side lobes of the two resonators.These parameters are significant for output beam shaping system. Furthermore, the misalignment characteristics of “loaded resonator” have been analyzed, the rear mirror misalignment on output power are more serious than the output mirror. The output power is 31% of the aligned resonator when the rear mirror tilt angle is +8 mrad. Consequently, the "loaded resonator" model is essential for analyzing large Fresnel number unstable resonators in laser design and commissioning.

Laser optical system aberrations can degrade beam quality, cause deviations from the optical axis during transmission, and shift focus positions, thereby adversely impacting laser processing. In this paper, the influence of aberration on beam quality of resonator with different structures is analyzed theoretically, compared with the negative-branch resonator, the positive-branch resonator is less affected, however, when the equivalent Fresnel number is large, the beam quality of both types of resonators deteriorates sharply. When these two resonators are numerically simulated, it is found that the effect of aberration is small for a positive-branch resonator with an equivalent Fresnel number of 72.6, and experimental results also prove this phenomenon. While a negative-branch cavity with the same gain region volume and equivalent Fresnel number of -223.8 has also been investigated, the output beam direction deviates -1.79 mrad from the optical axis when resonator with spherical mirrors, while the output beam is almost a collimated one and propagates along the optical axis for parabolic mirror resonator because the influence of aberration is eliminated. Therefore, the influence of aberration must be considered in the design of unstable resonator with large Fresnel numbers.

For the problems of long registration time and low accuracy caused by the difficulty of feature extraction during the registration of aviation blade point cloud, a method of point cloud edge contour extraction based on Alpha Shape algorithm is proposed. Using PCA principal component analysis to transform coordinate system of source point cloud, the Y-Z plane of the transformed coordinate system is used as the projection plane, the surface point cloud is projected into planar point cloud, and its planar boundary is obtained by Alpha-Shape algorithm, Compare the planar boundary coordinates with the original surface point cloud coordinates, and obtain the 3D edge point coordinates ,then obtain the surface edge point cloud. In the coarse registration stage,downsampling the target point cloud, the surface edge point cloud and the target point cloud are characterized by the FPFH algorithm,using the random consistency algorithm (SAC-IA)to register the edge point cloud and the down-sampled target point cloud , and the source point cloud is transformed to the initial position that meets the requirements of the ICP algorithm using the parameter matrix obtained from the coarse registration, Finally, the ICP algorithm based on Levenberg-Marquardt (LM) optimization is used to complete the precise registration. The results show that compared with SAC-IA+ICP algorithm, the accuracy is improved by 54% and the speed is increased by 17%.

Laser bending forming often requires multiple scans to achieve the desired angle, which can alter the sheet material′s structure and impact its mechanical properties. This study focuses on TA15 titanium alloy sheets and employs numerical simulation based on a phase transition dynamics model for dual heating and cooling processes. The simulation models the phase transition during laser dual scanning, revealing the distribution of phase volume fractions across the sheet section under varying laser energy densities and comparing these findings with experimental data. The simulation results indicate that dual scanning increases the phase transition zone size and the total martensitic phase amount. As laser energy density increases, the phase transition zone enlarges, but the martensitic phase volume fraction decreases. This study provides insights into the material structure changes and phase distribution during laser bending of titanium alloy sheets, which is crucial for optimizing the bending process and ensuring material integrity.

Chronic periodontitis (CP) is a disease caused by the chronic progressive destruction of dental support tissues mainly by dental plaque. The treatment of chronic periodontitis is limited by traditional treatments due to the small structure of oral organs, the susceptibility of bacteria to drug resistance, and the traumatic nature. Photodynamic therapy (PDT) offers advantages such as high sensitivity, minimal side effects, non-invasiveness, resistance to drug resistance, and a broad antibacterial spectrum. To overcome the limitations of traditional treatment, some scholars have combined PDT with periodontal therapy. This article reviews the principle of photodynamic therapy, the research progress of photodynamic combined therapy, and the factors affecting photodynamic treatment of periodontitis.

The non-clinical research data in the registration materials of energy therapy products, including dose-effect relationship and energy safety research data, are crucial for evaluating the safety and effectiveness of these products. This paper elucidates the specific requirements for various energy therapy products, such as optics, ultrasound, radiofrequency, and microwave equipment. It defines the concepts of dose-effect relationship and energy safety and proposes detailed requirements for the registration research materials pertaining to these aspects. The aim is to provide assistance and guidance to registration applicants and relevant practitioners in submitting pertinent content materials.