In order to improve the wear resistance of the ball valve, the laser cladding is used to construct the strengthening layer of the biological structure imitating the leaf pattern on the surface of the stainless steel, and the microstructure, hardness, and wear resistance of the sample are tested and analyzed. The results show that the microstructure is rapidly cooled, the grain is refined during the laser cladding process, and the surface hardness of the cladding layer is greatly improved, forming the "vein" structure in the bionics. However, due to multiple overlapping and secondary scanning, the grains continue to grow and the hardness decreases, forming the "mesophyll" structure in biomimetic. The "vein" and "mesophyll" are staggered, with the higher hardness being "vein" and the lower hardness being "mesophyll". "Leaf vein" plays a supporting role in the skeleton, and "mesophyll" plays a buffering role in filling the skeleton. Among the different coupling bionic paths, the specimen with an angle of 60° between the laser scanning path and the friction and wear direction has the best wear resistance. The oblique bionic structure is beneficial to release the stress in the friction pair and reduce the fatigue wear phenomenon. The main wear mechanism is a small amount of abrasive wear and adhesive wear.

Fe60 + WC composite coating with different quality fraction was prepared on the surface of Q235 carbon steel, and the macromorphology of microscopy, microhardness tester, scanning electron microscopy (SEM), energy spectroscopy analyzer (EDS), and X-ray diffractometer (XRD) were studied. The results show that WC addition can form a hard phase, so that the added Fe60 coated coating can effectively improve the hardness of Q235 carbon steel. When the WC mass fraction is 3%, the hardness is 8 times of the substrate, which reaches the maximum.

Modern transportation is the lifeblood of national economy. The brake disc is one of the important parts to ensure the safe and reliable operation of high-speed train. However, the brake disc is at high speed, facing harsh service environment, prone to wear, crack, and other phenomena, resulting in the failure of the brake disc. In this experiment, 24CrNiMo alloy steel powder was used as cladding material. By changing the process parameters of laser cladding, single-channel and multi-layer cladding layers were prepared on steel plates. By means of stereomicroscop, Zeiss microscope, SEM, microhardness test, and tensile test, the influences of process parameters on the single-pass forming and the microstructure and mechanical properties of multi-pass cladding layer were analyzed and compared. The results show that with the increase of laser power, the fusion width increases while the residual height decreases. With the increase of scanning speed, the fusion width and residual height both decrease. With the increase of powder feeding speed, the fusion width and residual height both increase, but pores and cracks are easy to appear. The surface of the cladding layer is lath martensite, acicular ferrite and upper bainite. The microstructures near the matrix are coarse pearlite, ferrite, and granular bainite. When the scanning speed is too high, the hardness of the cladding layer fluctuates greatly and the distribution is not uniform. When the scanning speed is 340 mm/min, the tensile strength of the cladded layer is 1 110.22 MPa and the elongation is 10%, which reaches the standard of traditional steel casting. Reasonable control of cladding process parameters can achieve high hardness, high toughness, and other performance requirements, and can realize efficient additive manufacturing of brake discs for high-speed trains.

High-entropy alloys are used as surface-modified cladding materials for parts due to their high comprehensive properties. In this paper, a FeCoCrNiAlMox (x = 0, 0.75, 1.0, molar ratio) coating was prepared on the surface of 2Cr13 substrate by laser cladding method, and the mixing entropy of the actual composition of the coating was calculated. The microstructures of different coatings were compared and analyzed by OM and SEM. The composition of different micro-domains of the coatings was analyzed by EDS of scanning electron microscope, and the effect of Mo was explored. The results show that Mo0, Mo0.75, and Mo1.0 are high-entropy alloy coatings, and obvious delamination occurs in the coatings. The microstructures from the bonding area to the cladding area are plane crystal, columnar dendrite, and columnar crystal. With the addition of molybdenum element, the dendrites decrease, the columnar crystals increase, and the structure become finer. The atomic percentage of Mo element in the pre-crystallization area is larger than that in the post-crystallization area; while for Al element, on the contrary; Fe element in the matrix is diluted to the cladding layer, and the needle-like and granular precipitates at the top of the cladding layer that are rich in Cr and poor in Al are preliminarily judged to be α-Cr phase. This study provides an information basis for the microstructure, composition analysis, and application of FeCoCrNiAlMox high-entropy alloy coatings.

It is difficult to obtain low residual stress and high hardness after laser cladding M2 powder coating on the surface of 20 steel at the same time. In this paper, the finite element model of piston rod and coating was established. Different preheating temperatures were set in piston rod. The variation laws of the residual stress and hardness were investigated. The results show that the residual stress and hardness are affected by their cooling rate. The cooling rate and the residual stress are decreased by preheating process, and it also has a significant effect on the coating hardness. With the increase of preheating temperature, the radial and axial residual stress of the piston rod and coating are decreased. Compared with the non-preheating process, the hardness of the coating basically does not change and the lower hardness of the fusion zone when the preheating temperature is 300-475 ℃. The hardness of coating and fusion zone is decreased significantly when the preheating temperature is 500 ℃. When the preheating temperature is 475 ℃ and the same environment temperature is 20 ℃, the maximum radial residual stress decreases by 39.8%, the maximum axial residual stress decreases by 42.1%, and the coating hardness basically does not change with comparison of the non-preheating process. It is helpful to reduce the coating residual stress and obtain high hardness coating by preheating the piston rod to 475 ℃ temperature before laser cladding.

The effect of different laser power on the joint formation, weld morphology, and microstructure of TC4 titanium alloy were studied by laser-tungsten inert gas (TIG) hybrid welding process. The results show that TC4 titanium alloy welded by laser-TIG hybrid welding can form a welded joint with good surface shape, and no obvious defects such as undercut and overlap. The molten pool near the laser beam will produce violent flow, and there will be pits at the center of the weld surface after the molten pool solidifies. With the increase of laser power, the cross section of the weld gradually changes from “mushroom” shape to “hourglass” shape, the average pore area gradually decreases, and the pores are mainly concentrated at the bottom of the weld. Under the hybrid of laser-TIG, the increased laser power will make the molten pool flow more intense and the grain size will gradually decrease. The microstructure of the weld is α′ Martensite bundles composed of multiple parallel α′ Martensitic with narrow residues β Phase band. The width of the β phase band varies considerably, the wider area is about 1.95 μm, and the narrow area is about 0.45 μm.

In this paper, the aluminum alloy (AlSi10Mg) additive manufacturing by selective laser melting (SLM) was used for laser welding experiments, and then the effects of laser power on microstructure and mechanical properties of AlSi10Mg alloy welding seam by SLM additive manufacturing were studied by OM, SEM and EDS technical analysis, and mechanical properties testing. The results show that the width of the laser-selective melting heat affected zone is small. The weld zone is columnar dendrite structure. With the increase of laser welding power, the laser energy increases, the melting depth increases, the hardness of the weld zone and the tensile strength of the joint decrease, and the elongation is low, (4.1%, 3.4%, and 3.1%, respectively). The primary dendrite spacing and microstructure in the weld zone gradually increase, and Si element is easier to aggregate in the alloy, leading to the fracture separation of reticular Al-Si eutectic, while Mg element content is small, and there is little change. The pores are distributed in the welding seam of laser welding, and the pores are larger towards the surface. Because the pores reduce the effective bearing area of the cross section, and the local stress concentration accelerates the crack propagation, it is very important to reduce or avoid the pores in laser welding. Finally, the fracture section of the joint shows the appearance of a river pattern with the characteristics of brittle fracture.

In this paper, laser transmission welding experiment was carried out with glass fiber/PBT composites. Firstly, the effects of glass fiber content, laser power, and welding velocity on welding quality were explored by the response surface methodology (RSM), and the interaction effects of glass fiber content and laser power on welding quality were found to be of least significant. Secondly, microscopic morphology observation of welding seam drawing section was implemented under the change of welding velocity and glass fiber content. It was found that when the glass fiber mass content was 10%, the glass fiber and PBT polymer were tightly wound; when the welding velocity increased from 3 mm/s to 7 mm/s, the fish scale texture of the welding seam became more and more obvious. Finally, the optimal combination of process parameters for maximum welding strength and maximum welding velocity was obtained by experimental analysis.

The effects of laser melting deposition process parameters (laser power and powder feeding rate) controlled by PLC on the phase composition, microstructure, and tensile properties of TC4 titanium alloy were studied by means of X-ray diffractometer, metallographic microscope, and tensile testing machine. The results show that under different laser power and powder feeding rate, TC4 titanium alloy is mainly composed of α phase harmony β phase. With the increase of laser power or the decrease of powder feeding rate, the β phase of TC4 titanium alloy will gradually change into α phase. The density of TC4 titanium alloy increases with the increase of laser power and decreases with the increase of powder feeding rate. With the increase of laser power or powder feeding rate, the tensile strength, yield strength, and elongation of TC4 titanium alloy increase first and then decrease. The maximum value is obtained when the laser power is 1 400 W or the powder feeding rate is 1.1 r/ min. When the laser power is 1 400 W and the powder feeding rate is 0.9 r / min, the tensile strength, yield strength, and elongation of TC4 titanium alloy are 1 212 MPa, 1 150 MPa and 9.4% respectively. When the strength is higher than that of as-cast and forged & annealed TC4 titanium alloy, and the elongation is significantly higher than that of TC4 titanium alloy melted by selective laser, and TC4 titanium alloy deposited by laser melting has good strength and plasticity, which is mainly related to the high density and relatively small α and β microstructure of TC4 titanium alloy.

The lapping process of 0.5mm thick 6061 aluminum alloy and 0.5mm thick 304 stainless steel are studied by 1000W-QCW laser. The experiment consists of two parts: single laser welding and Wobble laser welding. The well-formed welds are obtained by adjusting the process parameters. The morphology of weld microstructure and thickness of intermetallic compound (IMC) layer are analyzed by super depth of field optical microscope and scanning electron microscope (SEM).The effective joint width of single laser welding is 213 μm, and the average thickness of IMC layer is 6 μm. The effective weld width of Wobble laser welding is 1 048 μm, and the average thickness of IMC layer is about 2 μm. Then the tensile test of mechanical properties is carried out using tensile testing machine. The maximum tensile strength of single laser welding process is 420 N. The maximum tension of Wobble laser welding is 720 N, and the weld breaks at the interface between aluminum and steel.

In order to study the influence of laser parameters on the cutting quality of carbon fiber reinforced resin matrix composites (CFRP), a fiber laser is used to perform a cutting test on a 0.3 mm CFRP thick tube. The mechanism of laser cutting CFRP is explored, the single-factor process test of CFRP materials is carried out, and the influence of laser processing parameters such as laser power, cutting speed, pulse frequency and auxiliary gas pressure on cutting quality is studied. On this basis, in order to obtain the best cutting quality, the cutting quality evaluation index is proposed, and the combination of different laser processing parameters on the thermal influence zone of the cutting seam and the quality of the cutting wall surface are analyzed through orthogonal optimization test. The results show that the surface morphology quality of the laser cut sample is better than that of mechanical cutting, and there are fewer wall defects such as surface burrs and cracks after laser cutting than mechanical cutting. The final parameter combination for the best cutting effect is laser power 1 050 W, pulse frequency 2 000 Hz, auxiliary air pressure 1.8 MPa, and cutting speed of 1.5 m/min.

The Marangoni effect caused by the temperature gradient often causes molten pool overflow on the smoothed surface, which reduces the effectiveness of continuous laser polishing of metal surfaces. To reduce the Marangoni effect in the laser polishing process, 304 stainless steel substrate was heated to reduce the molten pool temperature gradient. The substrate temperatures are 25, 100, 200, and 300 ℃ respectively. Surface roughness, the cross-section of molten pool, and surface micromorphological features of laser polishing specimen were measured and analyzed by laser scanning confocal microscope and scanning electron microscope. The experimental results indicate that a smother laser polishing surface can be obtained by heating the substrate surface compared with room temperature polishing. With the increase of substrate temperature, the width and depth of the molten pool increase, and the ratio of depth to width increases. When the substrate temperature is 100 ℃, laser polishing could enable reductions in surface roughness of over 75.9% (from 1.08 μm to 0.26 μm Sa) while also eliminated the machining marks originally on the specimen. The carbide precipitation on the polished surface increases and the step structure is enhanced when substrate temperature increases.

Rapid and precise monitoring of fruit development is essential for orchard management and fruit output forecasting. Compared to conventional technology, liDAR as an active monitoring technology offers a greater variety of nondestructive, high-precision measuring, and positioning options for fruits. On the basis of laser-point-cloud modeling tests on indoor potted apple trees, a three-dimensional spatial positioning and size detection approach suited for apple fruit trees was discovered, which gives vital scientific direction for monitoring apple growth. In this work, a technique for the spatial localization and identification of apple fruit size was developed using laser point cloud data collected from the ground. This article acquires data on apple trees using the Faro Fcous terrestrial laser scanner. The point cloud using the RANSAC approach is segmented, the segmented point cloud data is reconstructed, a threshold to classify is established, the fruit point cloud is identified, and the fruit′s spatial coordinates and radius are extracted. In comparison to the actual data, the root mean square errors of the horizontal distance, angle, height, and volume of the apple are 17.31 mm, 12.62°, 13.66 mm, and 3 512 mm3, the average absolute percentage errors are 22.94%, 13.63%, 5.19%, and 9.33%, and the coefficient of determination R2 is more than 0.90. This approach is applicable to the extraction of data for various round fruits and can rapidly and accurately find apple fruits and determine their volume.

2D LiDAR is widely used in pedestrian detection due to its low cost and the resistance to external disturbances. However, the disorder and sparsity of the LiDAR points makes pedestrian detection more challenging. In this article, we use a transformation model converting points cloud to images and propose an improved person detection network based on YOLOX. Coordinate Attention (CA) is introduced before pyramidal feature representation to improve the pedestrian feature extraction capability of the model, and the adaptive spatial feature fusion network (ASFF) is added before YoloHead to alleviate the inconsistency across different feature scales. Compared with the YOLOX, the average accuracy (AP) and mean average accuracy (mAP) of the improved network are increased by 1% and 1.4%, respectively, with the average accuracy reaching 95.2%. The single frame point cloud image inference time is 48 ms, which is only 8 ms longer than the original model. The result demonstrates that the proposed model can improve pedestrian detection accuracy and robustness effectively while maintaining real time efficiency.

In this paper, the propagation characteristics of s-wave in aluminum cylinder are studied by finite element method for the detection of different Angle defects in small diameter metal cylinder. The energy range of s-wave was determined by the study of s-wave directivity, and the artificial rectangular defects with different angles were set in the main energy range of S-wave. The propagation characteristics of PRS wave (the primary reflected s-wave interacting with the defects) were studied by B-scan method. Based on the statistical study of the range of scanning Angle of PRS wave, the optimal detection Angle β (the scanning Angle with the maximum amplitude of PRS wave within the range of scanning Angle) was determined. According to the relationship between the arrival time of the largest PRS wave and the defect Angle α, the error of α Angle was 0.025 when the Angle was 30°, and the error of other defect angles was less than 0.02. This paper visualizes PRS waves at different α angles by using the range of scanning angles and the optimal detection Angle β, and proposes a method to evaluate the α Angle by extracting energy points. The above research results provide a certain degree of reference value for laser ultrasonic detection of internal defects of cylindrical materials.

针对现有激光粉尘传感器易受其他光线干扰影响导致检测精度低的问题, 设计抗干扰激光粉尘传感器。该传感器基于Mie散射法检测粉尘浓度, 激光发射模块发射脉冲激光, 照射在粉尘颗粒物上发生散射。激光接收模块检测散射的激光并进行光电转换, 然后对电信号进行滤波放大处理后传输到主控制器中。主控制器采用设计的WIN-FFT(加窗快速傅里叶变换)算法滤除其他光线照射产生的干扰信号, 而后基于滤波后数字信号计算空气中的粉尘浓度值。实验结果表明, 与预标定的称重粉尘浓度值相比, 抗干扰激光粉尘传感器粉尘浓度检测的相对误差小于±8%, 提高了抗干扰能力与粉尘测量的准确度。

For the measurement of different crack depth ranges on metal surface, the study is carried out by extracting the characteristic points of surface acoustic wave reflection component. Using COMSOL Multiphysics to perform finite element analysis on the process of laser ultrasound acting on the surface of aluminum plate, the obtained surface acoustic wave in the time domain signal is bipolar. When the surface acoustic wave propagates to the surface defect, the reflection echo RR1, RR2, and the mode conversion wave RS are formed, which appear as an obvious oscillation signal in the time domain signal. Based on the signal, the characteristic points that conform to the characteristics of the reflected component are obtained, and the arrival time of the reflected echo is obtained. The position of the defect front and the depth of the defect are calculated. The study finds that the location of surface cracks can be obtained by the arrival time of RR1. When the crack depth is small, which is less than or equal to the depth range of the surface wave penetration at the crack front (ranging from 1 to 3 surface wave lengths), the crack depth can be calculated by the arrival time of RR2. When the crack depth is larger than the depth of surface wave penetration at the crack front (more than 3 surface wave lengths), the crack depth can be calculated by the arrival time of RS. Finally, according to the difference of the crack depth range, a piecewise function for calculating the crack depth is obtained, which provides a reference method for detecting the crack depth on the metal surface in practical applications.

The rapid detection of foreign object debris (FOD) is very important for the safe driving of aircraft. Considering the problems of small size FOD target recognition difficulty and poor real-time performance in traditional FOD detection technology, a FOD detection method based on voxel feature fusion is proposed. The method firstly extracts the point cloud in the region of interest and calibrates the ground point cloud according to the RANSAC method. Secondly, the voxel feature fusion algorithm is used to divide the calibrated point cloud into voxels, and the average Z value and the average reflectivity of all point clouds are fused in each voxel according to a certain proportion to form a new point. In this way, the dense point cloud is reduced in the case of protruding FOD. The ground point cloud and the point cloud of FOD on the ground are segmented. Finally, the Euclidean clustering is used based on the KD-tree algorithm and clusters the point cloud of the FOD on the ground after segmentation. The experimental results show that this method can realize FOD detection with length, width, and height greater than 1.3 cm in a distance of 30 meters. Compared with the traditional method, the detection FOD size performance increased by 35%, which provides a reference for lidar in FOD detection.

As a new type of light source, semiconductor lasers have been widely used in communications, military, and medical fields. In different fields, semiconductor lasers either operate in constant current mode, or work in constant power mode, or work in DC mode, or work in AC mode. This article describes a non-temperature-controlled semiconductor laser driver in multi-mode operation, which can operate in different modes and can be switched freely. In constant current mode, FPGA can linearly adjust the driver current of semiconductor laser, and the goodness of fit of trend line is 0.999 77, which has excellent linearity. This current can also be modulated to generate sine waves, square waves, and triangle waves. The relative error of the generated waveform frequency is controlled in the order of 10-5 magnitude; In constant power mode, the FPGA can stabilize the laser output power in both DC and AC conditions. Under long-term testing, the relative standard deviation of output power is 0.209% when the laser is driven by DC and 0.275% when the laser is driven by AC. All operations can be controlled wirelessly via the host computer interface, maximizing ease of use and flexibility.

High-power semiconductor lasers are widely used in optical communication, laser processing, laser display, and other fields because of their small size, light weight, and high efficiency. The output power stability of high-power semiconductor laser depends on the current stability of the driving power supply. Based on the current negative feedback circuit principle, this paper realizes the constant current control of the high-power semiconductor laser drive power supply, theoretically analyzes the main factors affecting the long-term stability of the output current of the drive power supply, and experimentally adopts high-precision voltage reference source, low-temperature drift sampling resistance, water cooling sink and so on. A driving power supply with continuously adjustable output current between 0 and 12 A is designed. When the output current is 12 A, the current stability reaches 66.7×10-6 within 10 h. At the same time, the drive power supply with delayed start, current limiting protection, short circuit protection, and other functions, can fully meet the requirement of the stable operation during a long time for the high-power semiconductor laser.

The conventional single-wavelength laser wireless power transmission (LWPT) system has some problems, such as low photovoltaic conversion efficiency, excessive concentration of light spots, and complex tracking-aiming system. In this research, a novel LWPT system based on deep learning algorithm is proposed. The white laser is used as the energy transmission source and the security camera is used as the visual recognition source. A new fluorescent ceramic heat sink structure is proposed. This let 60 W white laser lamps work steadily at 70 ℃ ambient temperature. The light intensity is more than 6 000 000 cd, the luminous half angle is 1.8°, and the light spot covers the target more evenly. An algorithm based on YOLOv5 for recognition and target posture acquisition is presented. After training, the mean average precision (Intersection over Union 0.5) of the model is 99.78%. Within the 8m range, the 60 W white laser lamps illuminate solar cells to power up the LED lamps. Outdoor test shows that the novel LWPT system can automatically recognize, track, and illuminate solar cells which are carried by the UAV (unmanned aerial vehicle). The system is more robust to avoid street lamp interference.