In order to find weld defects in time and improve the welding quality of workpieces, a laser vision image-guided mechanical weld recognition method is proposed. Analyze the structure of the laser vision imaging system, build the camera imaging model, and adjust the imaging position through coordinate transformation to avoid distortion; Through binary processing and expansion operation, the contour features of the pattern are retained to reduce the image noise; The gray distribution of the image is adjusted by contour pose correction and histogram equalization; Taking crack, incomplete penetration, incomplete fusion, porosity and spherical slag inclusion as the main manifestations of the weld, combined with the parameters of edge smoothness and filling degree, the weld characteristics are extracted; Establish the classification surface of support vector machine, input the samples to be recognized, input the feature types into support vector machine, determine the penalty coefficient, and output the recognition results after continuous training. Experiments show that the image obtained by the proposed method can contain more feature information and reduce the probability of error recognition.

The welding riveting composite connection of Q460 steel/6061 aluminum alloy for construction was carried out by using laser-TIG arc composite heat source, the effects of DC-TIG current on the forming, morphology and mechanical properties of aluminum/steel welding riveting composite joint were studied. The results showed that, when the DC-TIG current is 75~ 115 A, the steel/aluminum welding riveting composite joint samples are well formed, and there are no abnormal cracks, pores and other welding defects in the solder joint and surrounding area; With the increase of DC-TIG current from 75 A to 115 A, the area of unmelted area of solder joint gradually decreases, the welding penetration of aluminum plate gradually grows, the tensile and shear load of steel/aluminum welding riveting composite joint first increases and then decreases, and the maximum value is obtained when the DC-TIG current is 95 A; When the DC-TIG current is 75 A, the steel/aluminum welding riveting composite joint shows button fracture, and the other joints show pull-out fracture; The appropriate DC TIG current is 95 A, when the solder joint is well formed, the welding penetration is 350 mm, and the tensile shear load is 5.52 kN.

A semiconductor laser was used to conduct laser transmission welding experiments on polyarylsulfone (PASF) filled with zinc powder absorber and the influence of zinc powder absorber on PASF welding effect and weld morphology was explored with different mass of zinc powder absorber in this paper. Firstly, the shear strength of welded parts was tested and the influence of zinc powder absorbent on the shear strength was analyzed. Secondly, the surface morphology and weld width of welds were observed, and the microstructure of weld pool was observed by scanning electron microscope, and the macroscopic morphology of weld cross section and interface of molten zinc particles were analyzed. The results showed that the zinc powder absorber has a greater impact on the welding of PASF and the best welding effect was got when the zinc powder mass is 16.8 mg. Phenomena such as polymer molecular chain diffusion entanglement, zinc powder particles wrapped by PASF and connected zinc powder particles, in the molten state, have a positive effect on the welding strength.

For laser splicing welding of stainless steel with thickness of 1.0 mm, the influence of clearance on weld strength was analyzed. When the assembly gap was 0 mm, orthogonal experiments was conducted on laser power, welding speed and defocusing amount to obtain the maximum tensile strength of welded joint and the corresponding optimal process parameters. The tensile strength of the weld was tested by welding experiments under different clearance conditions. The tensile strength of welded joints almost remained unchanged when the assembly gap was between 0 mm and 0.09 mm, but decreased sharply when the gap was 0.12 mm. When the assembly clearance was less than 0.09 mm, the microstructure of the fracture surface was rough and showed shear lip, and when the assembly gap was 0.12 mm, the weld was brittle fracture.

Based on the conductivity tomography technique, the laser cladding conductivity tomography equipment is designed to quickly present the conductivity distribution of the cladding layer for analysis of structural changes.The molten clad material 304 stainless steel was used as the object of study, and the designed conductivity tomography imaging equipment was used to test the molten clad layer of 304 stainless steel to compare and analyze the detection of the molten layer of 304 stainless steel with different number of electrodes, excitation measurement mode and temperature change, and to verify the feasibility of the detection method.The results show that the measured voltage data have low fluctuation and high stability in the case of 16-electrode, interval excitation reference measurement mode;The super-resolution image reconstruction algorithm is capable of accomplishing the identification of different shapes of the molten cladding layer with high accuracy of the reconstructed image;Compared with the room temperature region, the heating region of 304 stainless steel cladding layer electron movement speed up, conductivity distribution changes significantly, the conductivity of significant differences occur.

To predict the geometrical characteristics and cross-sectional average hardness of composite cladding layer of U71Mn steel laser cladding WC-Ni60, and to provide reference for repairing rail wear by laser cladding technology. Different experiments were designed and single-track WC-Ni60 composite coatings were deposited on the surface of U71Mn steel by later cladding technique.Meanwhile,the cross-sectional macrostructure and average hardness of the single-track coating was observed by industrial microscopy and Leitzs microhardness tester. Then BP, GA-BP and PSO-BP network were used to predict, and the result of them were compared with the experimental results. The prediction accuracy of GA-BP and PSO-BP model was both good,the average relative errors of the GA-BP model and the PSO-BP model were 2.53% and 2.90%, respectively. The GA-BP model was more accurate in predicting the average hardness of the cladding layer, the average relative errors were 1.00%. The PSO-BP model was more stable than the GA-BP model.So the accuracy of GA-BP model was higher, and the stability of PSO-BP model was better.

Selective Laser Melting (SLM) Technology, as a representative of additive manufacturing technology, has a wide range of applications in the field of civil aircraft, but the overall application maturity is not high. In this paper, the influence of different key factors on additive manufacturing performance is analyzed based on the key factors of SLM technology itself. At the same time, according to the requirements of airworthiness, the challenges of selective laser melting technology in the field of civil aircraft are analyzed, and the development direction of the popularization and application of this technology is provided.

Considering the influence of processing parameters and model shape parameters of selective laser melting on the forming quality of the part, four levels of five factors, such as contour laser power, filling laser power, scanning speed, scanning distance and shape parameters, were selected to carry out the orthogonal experiment. The influence of these five parameters on the surface roughness, X/Y dimensional accuracy and the profile error of circular surface is studied. In order to evaluate the forming accuracy synthetically, the multi-objective optimization model is established. In order to facilitate calculation, the weighted method is used to turn the multi-objective into single objective optimization. The final results show that the precision of the printed parts is the best when the filling laser power is 210 kW, the scanning distance is 0.09 mm, the surface laser power is 160 kW and the scanning speed is 1 100 mm s-1. At the same time, the results also show that the shape parameters of the parts have some influence on the precision of the parts.

The selective laser melting (SLM) process of AlSi10Mg alloy was numerically simulated by simfactory additive 4.0 software. The effects of scanning speed, scanning distance, substrate temperature and laser power on the deformation behavior of AlSi10Mg alloy and the residual stress on the interface between the part and substrate were studied. The results show that the tensile deformation is mainly in the x direction, while the shrinkage deformation is in the y and z directions; With the increase of substrate temperature (25-225 ℃), laser power (250-450 W), scanning speed (900-1 300 mm/s) and scanning spacing (40-80 mm/s). The results show that the residual stress of the interface decreases first and then increases with the increase of the stress. Through simulation, the best printing parameters are the substrate temperature: 180 °C, the scanning speed is 1 100 mm/s, the laser power is 450 W, and the scanning distance is 70 μm.

The 18Ni300 die steels were prepared by the Selective Laser Melting (SLM). Compared with the forged sample, the microstructure and corrosion resistance of 18Ni300 die steel sample prepared by SLM in 3.5% (mass fraction) NaCl solution was analyzed. The results show that the hardness of the SLM formed specimen is slightly lower than that of the forged specimen. There were many small holes in the microstructure of SLM sample; the volta potential of SLM formed sample is lower than that of forged sample; the corrosion resistance of SLM formed sample is worse than that of forged sample according to the results of the polarization curve test and immersion corrosion test.

In this paper, an electron-spin-lattice three-temperature coupling model is established for the femtosecond laser ablation of the face gear material 18Cr2Ni4WA. The temperature change process of the face gear material under the effect of electron, spin and lattice single pulse energy at different energy densities is simulated and analyzed, and the evolution relationship of ablation crater morphology and roughness and other characteristics under different energy densities is experimentally studied. It is shown that the temperature of the spin system is finally cooled by the temperature of the lattice system, and the temperature of the electron increases sharply with the increase of energy density and the equilibrium time of the electron, spin and lattice temperatures also increases. The diameter and depth of the ablation crater become larger with increasing energy density, and the tooth surface roughness does not get better continuously with increasing energy density. The ablation characteristics of the face gear material simulated by the three-temperature coupled model are experimentally verified, which can provide a reference for improving the quality of face gear processing.

In order to quickly and easily prepare micro-nano structures on the surface of nickel-based alloys to achieve super-hydrophobicity, femtosecond laser processing and modification with fluorosilane were used to successfully achieve super-hydrophobicity on the surface of nickel-based alloys, and their corrosion resistance and adhesion, and its corrosion resistance, adhesion, and self-cleaning properties were tested. The experimental results show that the prepared surface has good superhydrophobicity, and its contact angle is 156.8° and the rolling angle is 4.2°. Different laser scanning distances have a significant effect on the wettability of the metal surface. As the scanning distance increases from 5-50 μm, the contact angle changes from 156.8°-121.7°, and the rolling angle changes from 4.2°-90°. Electrochemical corrosion experiments show that when the scanning distance is 15 μm, the corrosion resistance is better improved, and the self-cleaning experiment shows that water droplets can easily take away surface dust. Changing the scanning interval can control the surface morphology to achieve super-hydrophobicity, and effectively improve the surface corrosion resistance.

The evolution of dislocation patterns and the properties of hexagonal close-packed (HCP) structure in TC4 dual-phase titanium alloy under ultra-high strain rate plastic deformation were studied via laser shot peening (LSP) treatment. The results show that, the compressive residual stress can be generated and the grains can be refined by the LSP treatment. Moreover, with the LSP times increasing, more finer grains, larger compressive residual stress, and the depth of LSP-induced compressive residual stress are generated. The evolution of dislocation patterns in the HCP structure subjected to LSP treatments can be described as follows. For the as-machined specimen (with an average grain size d=21.33 μm), dislocations and dislocations are dominant. While for the LSP-1 specimen (with an average grain size d=9.65 μm), parts of unstable dislocations are decomposed into dislocations and dislocations. After massive LSP treatments (with an average grain size d=4.55 μm), more slip systems are activated, and dislocations and dislocations are dominant eventually. In addition, Values of hardness and elastic modulus of HCP structure increase with the increase of strengthening times, but the increment decreases simultaneously.

In this paper, fiber laser is used to laser quench the surface layer of rail material U75V. The surface flatness of the rail specimen after laser quenching is no different from that before quenching. The quenching depth at the center of the laser heat source is the deepest, about 1 mm. The center position is a very fine acicular martensite structure, at the overlapping position. The grains in the laser secondary quenching zone will be refined again. The latter pass has an obvious thermal effect on the former pass, resulting in a coarse retained austenite structure. The U75V laser quenching hardness of the rail is as high as about 850 HV, the effect of hardness improvement is obvious.

Laser shock peening is a surface strengthening technology that uses laser beams to modify the surface of metal materials, which can improve the surface microstructure of materials, generate work hardening and compressive residual stress at a certain depth, effectively improve the fatigue properties and prolong the service life of materials. This paper introduces the technical principle of laser shock peening, summarizes the process parameters, numerical simulation and main application research of laser shock peening technology, and prospects the follow-up research and development of this technology.

In order to improve the service life of the grilled board of the grate cooler, the laser surface alloying technology is used to prepare an alloy layer on the surface of the ZG40Cr25Ni20 anti-wear and heat-resistant steel. Under the optimal process parameters, the surface of the grilled board is continuous and smooth without pores and cracks; the alloy hardened layer forms a good metallurgical bond with the substrate; The microstructure of the alloy hardened layer from the surface to the bottom is equiaxed crystals, dendrites and columnar crystals in sequence; The average hardness of the laser alloy hardened layer is 840 HV, which is about 1.6 times that of the matrix. The installation experiment of the cement plant shows that the service time of the grate slab after laser alloying has been prolonged by more than one time on average.

Aiming at the inaccurate detection of cone buckets by Euclidean clustering algorithm in the race track environment, a cone bucket detection method based on improved Euclidean clustering algorithm is proposed. Firstly, the point clouds are collected through the robot operating system (ROS); then the point clouds are preprocessed to find the region of interest (ROI) and then the ground and cone bucket point clouds are separated using a random sampling algorithm; then the distances and thresholds are modeled; then a region partitioning method is designed for the track environment to improve Euclidean clustering algorithm, and the cone bucket point clouds are segmented using dynamic threshold clustering; finally the algorithm is validated through the Matlab platform. The accuracy of clustering segmentation reached 93.98% and 99% in real-world tests under two track environments, respectively. The test results show that the proposed method can accurately detect the cone bucket in the track.

In order to solve the inefficient and time-consuming detection problem of artificial drunk driving and realize the rapid non-contact screening of drunk driving, this paper designed a set of non-contact measurement system based on the tunable laser measurement method to detect the concentration of alcohol gas in the air. The alcohol characteristic absorption peak of 3.345 μm band was used as the characteristic data and the second harmonic algorithm was used to measure the gas. The experimental results showed that the alcohol gas concentration had a good correlation with the second harmonic integral value R2=0.971. At the same time, it is verified that the detection limit of alcohol gas by the second harmonic integral area method of tunable laser can reach 50 mg/100 mL. It is proved that the method of using tunable laser to measure the second harmonic integration has a good effect on alcohol gas detection and provides theoretical support for the practical application of drunk driving detection.

Aiming at the noise caused by human interference and equipment defects in the process of laser scanning, a steady-state filtering technology of spectral data based on the informatization of laser scanning terminal is proposed to effectively remove the noise. According to the composition structure of the laser scanning system and the information process of the terminal, the noise source in the scanning process is determined, and the spectral data noise model is established under the influence of factors such as beam divergence, scanning angle and equipment defects. After wavelet transform, the initial signal is decomposed into low frequency and high frequency. Soft threshold function and hard threshold function are integrated to describe the changing trend of spectral data after wavelet decomposition, and the filtering threshold function is set to realize noise filtering. Simulation results show that the proposed technique can effectively improve the signal-to-noise ratio of spectral signal, and the root mean square error between the filtered signal and the real signal is the smallest.

Cable sheath is one of the most common physical evidence at the scene of an explosion, as well as at other crime scenes such as kidnapping, theft, homicide and rape. In order to establish a method to identify cable sheath quickly and effectively, 40 cable sheath samples were tested by X-ray fluorescence spectrometer. In this paper, we examined and analyzed the cable sheath that may be left behind at various crime scenes such as explosions. The samples were preliminarily clustered by K-means clustering into 5 categories. On this basis, the multi-layer perceptron and Fisher discriminant analysis classification models are constructed. The results show that the accuracy of training set and test set of multi-layer perceptron classification model is 100%, and the accuracy of Fisher discriminant analysis classification model is 90% using the leave-one-out cross-validation method. It can be seen from the classification accuracy that the combination of X-ray fluorescence and machine learning methods can effectively classify cable sheaths quickly and accurately. Thus, this method can provide efficient traceability support for all kinds of crimes involving cable lines, such as explosion cases.

Low cadmium ion contents in aqueous solutions were determined based on laser-induced fluorescence spectroscopy. Cd2+ ions in aqueous solution were extracted with chelating resin ECS60, and the fluorescence emission of the cadmium chelates excited by a laser at a central wavelength of 447 nm was analyzed. The results showed that the sensitivity of laser-induced fluorescence spectroscopy was significantly increased for the detection of cadmium in water. The effect of reaction time of the resin chelating the ions and the acidities of the aqueous solutions on the fluorescence emission intensities of the chelates was studied, indicating that it took 40 min for the resin to form stable Cd2+ chelates at the optimal acidity of pH 6.0. In this case, the strongest fluorescence emission of the chelates was obtained when excited. The laser-induced fluorescence spectroscopy could be applied for effective detection of Cd2+ ions in aqueous solutions.