Aiming at the problems of low positioning accuracy, poor positioning effect and low positioning performance in the center positioning process of the current algorithm, a linear positioning algorithm for the spot center of laser welding pool image is proposed. Firstly, the laser molten pool image is processed by denoising, interference suppression and information enhancement, and the image features are extracted according to the processing results. Secondly, Hough transform method is used to transform the image characteristic parameters to complete the extraction of laser spot center information. Finally, the linear positioning of the laser spot center is realized through the extracted information. Experimental results show that: when the algorithm is used to locate the spot center, it has high positioning accuracy, good positioning effect and strong positioning performance.

The formation mechanism of typical welding defects in copper and steel dissimilar metals was studied using fiber laser. Results show that the main welding defects in laser welded of copper steel dissimilar metals were micro-segregation, porosity and solidification cracking. The main reason for the micro-segregation and solidification cracking was the composition segregation during the solidification process of molten pool metal. The Cu element segregation at grain boundaries weakened the bonding force between grains, thereby resulting in offsetting the thermal stress during the welding process by virtue of the plastic deformation of grains and the occurrence of grain boundary cracking. The formation of pores was mainly related to the keyhole instability during the laser welding process. The keyhole instability caused the collapse of the inner wall of the keyhole, which resulted in that the metal vapor cannot overflow smoothly from the molten pool surface. The method of alternating magnetic field assisted laser welding was proposed to restrain the defects of welds and obtain good weld formation.

Due to the multiple welding parameters and the coupling of various welding parameters in the hybrid welding, any change of the welding parameters will have a significant influence on the weld geometry. Therefore, it is always very important to choose reasonable parameters that can increase the stability of welding bead and geometry. In this paper, we will make the center of welding bead and geometry as the origin of polar coordinate system in which the dimensions of welds will be measured every other 15 degrees. Basing on multiple welding parameters and welding shape dimensions, we apply the BP neural networks to build a calculating model between the welding parameters (welding current, laser power, welding angle, welding gap and welding ) and 24 groups of welding shape dimensions in the polar coordinate system. Finally a genetic optimization algorithm is introduced to improve the forecast precision. The dimension difference between the dimensions on the right side and those on the left side is calculated as the symmetry of the welding shape. The research shows that the dimensions prediction accuracy of the optimized predicting BP neural is 5% and the symmetry prediction accuracy is about 13%. The research method proposed in this paper has a important significance to the hybrid welding research of parameter optimization.

Using laser cladding technology to prepare nickel-based tungsten carbide reinforced coating on the surface of 42CrMo steel substrate, this paper studied the microstructure, element composition, phase composition, microhardness and wear resistance of the nickel-based tungsten carbide reinforced coating under three different binders that were prepared by adding rosin alcohol solution, a mixed solution of cellulose acetate and acetone, and an aqueous solution of water glass. Results show that the phase composition of the laser cladding coating is γ-Ni(Fe), Ni3Fe, WC, Cr23C6, Cr7C3. When the rosin alcohol solution is used as the binder, the bottom of the coating obtained is cell crystals and some dendritic dendrites. Moreover, the structure distribution is dense and uniform, and the middle of the coating is mostly dendritic dendrites. The average hardness is 739.4 HV, and the average friction coefficient is 0.53. The average wear volume is 14.07×10-3 mm3, which are reduced by about 13% and 68.5%, respectively, compared to the matrix. The form of wear is slight abrasive wear and fatigue wear, which improves the wear resistance of the coating.

Due to the poor control effect of electric vehicle suspension system and the failure to extract material surface cracks, in order to reduce the integrity and effect of crack repair, the control of electric vehicle suspension system and laser cladding repair method of material surface cracks are proposed. Firstly, the dynamic model of electric vehicle is constructed, and the suspension performance is analyzed. Based on this, LQG controller is designed to realize the control of suspension system. The flood filling algorithm is used to extract the crack target on the material surface, and the height and width of the crack are calculated. An neural network is used to construct the laser cladding repair model to complete the repair of the crack on the material surface. Experimental results show that the proposed method has good control effect, high integrity and good effect.

The laser cladding technology was used to prepare GH4169 coating on the surface of as-rolled GH4169 alloy. The microstructure, precipitation phases, high temperature micro-hardness and high temperature wear properties of the coating were studied. Results show that there are no defects, such as pores and cracks in the coating, and it is mainly composed of Laves segregation phase, γ matrix phase and a small amount of MC and MN phases. The average micro-hardness of coating at room temperature is 273.6 HV (0.3 kg test force), and with the increase of the test temperature, its micro-hardness shows a downward trend at different temperatures. When the test temperature is 600 ℃, its micro-hardness decreases to 197.4 HV (0.3 kg test force), about 72% of that at room temperature. High temperature wear property results also show that the wear rate decreases with the increase of the test temperature. When the test temperature is 600 ℃, the wear rate of the sample is close to 25% of that of the room temperature tested sample. After the wear test, the micro-hardness of the samples, which test temperatures are not higher than 500 ℃, have no obvious change, while the room temperature micro-hardness of the coating with the test temperature of 600 ℃ is increased due to the precipitation of strengthening phase.

In the field of textile and clothing, although the traditional textile and clothing technology is good, in mass production, it cannot meet the needs of people. Based on this, the emergence of laser processing technology has been widely used in the field of textile and clothing, with the advantages of high precision, high degree of automation. There are laser cutting, laser engraving, laser welding and other laser processing technologies. This paper briefly introduces the laser processing technology in the field of textile and clothing, summarizes its research status, and gives the development trend of laser processing technology in the field of textile and clothing outlook.

An array of micro-craters was machined on the surface of M35 high-speed steel (HSS) using a 1 030 nm femtosecond laser. The three-dimensional morphology and the contact angle of the samples were measured using an optical microscope, a white light interferometer and a contact angle measurement system. Results show that the sizes and depths of the craters increase with increasing energy density and number of scans. The contact angle of the M35 HSS surface decreases, and the hydrophilicity of the sample surface increases. Reducing the spacing of the craters can improve the hydrophilicity of the M35 HSS surface. These test results can be used as a reference for the study of surface wettability of HSS.

A 1 060 nm fiber laser marking machine was used to mark the square on the surface of 2024 aluminum alloy, and the effects of scanning speed, filling interval, laser average power and other process parameters on the laser marking quality of aluminum alloy are studied. Three factors and a 5-level orthogonal experiment were designed to study the effect of laser process parameters on the quality of the laser marking. The color difference and surface roughness of laser marking were evaluated by colorimeter and ultra-depth three-dimensional microscope. Results show that the overlap rate of scanning track and beam spot have more obvious influence on the color difference of laser marking, and the energy and heat of materials receiving laser have more obvious influence on the roughness of laser marking. The optimized parameter combination after orthogonal optimization was: the scanning speed of 644 mm/s, the filling interval of 0.028 mm and the laser power of 15 W. The optimized marking has a surface roughness of 1.5 μm and a color difference of 9.41 NBS.

The laser molten pool model was built to research the influence of high-frequency ultrasound vibration (HFUV) on aircraft thin-walled structures using the COMSOL software. The acoustic pressure of the laser molten pool was simulated, which considered the position and number of sources, with side-touch single vibration sources. Subsequently, we analyzed the conditions of the ultrasound cavitation effect and the acoustic streaming effect. The results indicate that, firstly, the positive and negative acoustic pressures alternate with HFUV, and this phenomenon favors the formation and collapse of cavitation bubbles. Secondly, the distance and amplitude of the ultrasound are directly proportional to the acoustic pressure of the molten pool. The acoustic pressure of the molten pool will enlarge 2-3 fold with each 10 mm decrease in the distance, which will enlarge by 10 Pa with each 4 μm increase in the amplitude. Thirdly, HFUV primarily acts as a blender toward the molten pools. The acoustic streaming effect will appear when the amplitude is higher than 7 μm and the distance is lower than 60 mm. The ultrasound cavitation effect will appear when the distance is lower than 15 mm. Fourthly, the acicular α′-martensite content is more intense, orientation and arrangement are more cluttered, besides, the acicular α′-martensite average length is shorter because of ultrasonic vibration and radiation pressure.

In order to detect the inclined microcracks on the surface of the workpiece, this paper analyzes the interaction between the broadband Rayleigh wave generated by the laser and the inclined angle defect on the rectangular aluminum plate theoretically and experimentally. The angle of the defect is measured quantitatively by the transmitted wave, reflected wave and the diffraction wave generated at the crack tip by the Rayleigh wave interacting with the inclined defect. By observing the stress nephogram of the finite element simulation, it is found that Rayleigh waves propagate along the defect, and modal conversion occurs at the tip of the defect. Some waves are diffracted along the crack to the metal surface, and some of the waves are reflected while some are converted into longitudinal and transverse waves. In this paper, through the Fourier transform of the diffracted wave, the frequency spectrum of the diffracted wave is obtained, the trend of the diffracted wave in the frequency domain is observed, and the energy of the diffracted wave is calculated. The energy of the diffracted wave decreases with the increase of defect angle, and it is e exponential decay distribution. Combining finite element simulation with experiments, the results show that when the surface defect and the surface are inclined at a certain angle, the energy extraction of the diffraction wave may be an effective method to detect the inclination angle of the surface defect.

In order to predict the geometric error of machine tool guide more accurately, a geometric error prediction method based on tolerance was designed, and the mapping relationship between surface topography error and geometric error was given. Sampling dual-frequency laser interferometer can realize the advantages of high precision, fast response and high resolution, which can fully meet the needs of high precision displacement testing. Thirty-seven measuring points were set for the travel of X-axis guide rail in an equidistance manner. After the sliding plate arrived at each measuring position and stayed for 6s to complete the sampling process, the R2 parameter of the fitting curve of the circular marking position could reach the ideal fitting accuracy. There is a difference of 0.15 μm between the actual measured data and the predicted results. Compared with the geometric error test results, most of the residuals are small, and the maximum residuals are controlled within 10% of the measured results. The proposed method can accurately predict the geometric error of the guide rail in the initial design process of the machine tool based on the tolerance. This study has a good theoretical significance for improving the accuracy of machine tools and is easy to be applied in practice.

Aiming at the problems of poor detection accuracy in the existing high-frequency partial discharge detection methods of electrical equipment, a high-frequency partial discharge detection technology of electrical equipment based on modulated laser phase is proposed in this paper. The frequency domain window width is determined by Gaussian error function to complete the acquisition of high-frequency partial discharge signals of electrical equipment. According to the characteristics of sinusoidal or cosine signal of local discharge narrow-band interference signal of electrical equipment, the Fourier series method is used to suppress the narrow-band interference and extract the characteristics of discharge interference signal. On this basis, the high-frequency partial discharge detection of electrical equipment is completed by synchronously calibrating the high-frequency signal and separating the laser phase pulse. Experimental results show that the high frequency partial discharge detection technology of electrical equipment designed in this paper effectively improves the accuracy of high frequency partial discharge detection of electrical equipment, and the detection time is always less than 4 min.

Laser ultrasound can realize the function of nondestructive testing of internal defects and residual stress state of components. The center frequency of the sensor was set as 2.5 MHz, and the software was used to complete the data acquisition process and implement filtering processing. The K417G disc was first treated by hot die forging, and then shot peening was carried out on its surface. A total of 5 points were set on the K417G nickel-based alloy along the length direction. The distance of the adjacent points was controlled as 1.96 mm, and the surface wave velocity was 2 950 m/s. Test results show that the surface wave velocity above 2 949 m/s is reached in both x and y directions, and the compression stress is formed on the surface of K417G disc. Both XRD and ultrasonic examination showed that compressive stress was formed, with the same variation trend. The maximum radial residual stress measured by XRD method is -906 MPa. The laser ultrasonic method with larger test depth can obtain smaller test parameters than the XRD measurement results. This study is of great practical value to understand the surface residual stress distribution of metal samples after shot peening, which is helpful for the subsequent machining process selection.

In view of the problems existing in the current cable winding machine, such as the untimely return to the edge, low efficiency and reliance on manual reverse, a line laser sensor is used to detect the real-time dynamic situation of the cable arriving to the edge of the cable winding machine, and the lateral movement direction of the winding machine is adjusted timely according to the results. Firstly, according to the cable and the special position of the baffle node, the segmentation of point cloud data was achieved via concave and convex constrained point detection algorithm. Secondly, using RANSAC algorithm of baffle linear fitting, the data after using slope characteristics were found in cable data cable under test, with measuring cable the overall least square circle. Finally, the relative position of the cable was calculated to the damper under test. Experimental results show that the algorithm can accurately find the data segmentation point and calculate the distance between the cable to be tested and the baffle, which realizes the real-time detection of the reverse to the edge during the winding process of the cable.

Point cloud registration is a critical step in 3D reconstruction. In order to solve the problems of low speed, many iterations and low accuracy of the traditional Iterative Closest Point (ICP) point cloud registration algorithm, this paper builds an imaging system that consists of a 3D camera and a RGB module and proposes a new method that combines the Accelerated KAZE (AKAZE) algorithm with the Generalized Iterative Closest Point (GICP) algorithm. In this method, the AKAZE algorithm was used to match the feature points of RGB image, and the RGB image feature points were mapped to the corresponding point cloud data. Moreover, the GICP algorithm was then used to achieve the point cloud registration. Results show that, compared with the usual ICP algorithm, the fusion algorithm in this paper reduces the number of iterations, the average time is shortened by 41.29%, the time efficiency is greatly improved, and the registration effect is also significantly improved. The point cloud registration method proposed in this paper effectively solves the problem of low time efficiency of traditional registration method.

Aiming at improving the low efficiency in CNC machine tool coaxial testing, a new type of CNC machine tool coaxial testing technology is developed through visual imaging system to build a mechanical control system that can meet the automatic positioning of feed system of CNC machine tool. Research results show that when the camera pixel is 5 million, the average error of the arc piecewise circular algorithm is 0.046 mm, and the total time required is 242 ms to achieve the real-time display effect. Moreover, fast arc detection algorithm can achieve high accuracy in a short time under the condition of low camera resolution, so as to improve the final image processing accuracy. Furtermore, the application test shows that the response time required by this algorithm is 244 ms, and it can control the chuck offset in real time. The average error is 0.038 mm, the maximum is 0.075 mm, and the alignment time of CNC machine tool is greatly shortened without decreasing the accuracy. This research has a practical significance for improving the machining accuracy of CNC machine tools, which is easy to be applied widely.

In order to improve the efficiency and quality of laser paint removal, the surface roughness of the substrate after laser paint removal was optimized by response surface analysis. By establishing the quadratic polynomial regression model of laser paint removal process parameters, the adaptability of the model is verified, and the surface properties of the substrate after using the optimal parameters are further compared and analyzed. Results show that the laser power and frequency have significant effects on the surface roughness of the substrate, and scanning speed and scanning times have little effect on surface roughness. When using 2024 aluminum alloy as the base, the paint thickness is 100 μm, the optimal parameters obtained by response surface analysis method are: laser power 45 W, laser frequency 400 kHz, laser scanning speed 600 mm/s, scanning times 6. Surface roughness of Sa the substrate is 1.739 μm, and the error rate between simulation and experiment is only 0.6%. These results show that the macroscopic morphology of the substrate surface is uneven and laser scan trace, and the surface roughness Sa increases from 1.319 μm to 1.739 μm. It is found that there are passivation layer and bulge molten substance on the surface of the substrate, and the local area is smoother and even, and the chemical composition of the matrix has not changed. After laser paint removal, the microhardness of the substrate decreased from 141.59 HV to 130.37 HV, the corrosion rate decreased from 0.008 852 0 mm/a to 0.002 340 4 mm/a, and the microhardness of the substrate decreased and the corrosion resistance improved. Although the surface morphology and properties of the substrate are changed after laser paint removal, it has no effect on the reuse of the substrate and the repainting of the paint. This research provides a reference for improving the laser paint removal process, so as to reduce the matrix damage and obtain better paint removal effect.

In order to avoid the environmental pollution and damage to operators caused by the use of chemical reagents for wheel set paint removal, an automatic paint removal method based on composite laser is proposed. The equipment adopts the through design, and the runner mechanism cooperates with the system scheme of three-axis automation platform to meet the requirements of on-site process layout and assembly line operation. Through theoretical calculation, effect test, efficiency test and SEM test, the specific process parameters are pulse laser power 100%, scanning speed 8 000 mm/s, line width 55 mm, frequency 20 kHz and wheel set rotation speed 21 mm/s. The power of semiconductor laser is 90%, the scanning speed is 7 000 mm/s, the line width is 55 mm, the frequency is 2 kHz, the duty cycle is 100%, and the transverse moving speed of laser processing head is 1.95 mm/s.

In the measurement process of wavelength modulated laser absorption spectroscopy (WMS), the measurement system will inevitably be affected by circuit hardware noise, mechanical vibration noise, environmental noise and other factors. Taking the absorption spectrum of CH4 near 6 046.95 cm-1 as an example, the noise response characteristics of WMS technology are quantitatively studied by numerical simulation methods. The peak value changes of normalized second harmonic signals extracted by FFT filtering method under different signal-to-noise ratio are compared and analyzed. On this basis, the relationship between standard deviation and relative error of the second harmonic peak value change and the signal-to-noise ratio was modeled. Moreover, the approximate expression between the two and the signal-to-noise ratio was obtained, and the fitting R2 value are 0.999 57 and 0.993 52, respectively. Research results show that the method of data averaging cannot fundamentally eliminate the influence of noise on the accuracy of WMS measurement. The mathematical model established in this paper provides an idea for the correction of WMS measurement results under the influence of noise.

Quantitative phase detection is an important indicator for detecting the wavefront of incident light field. Shack-Hartmann wavefront sensors (SHWFSs) can simultaneously measure amplitude and phase distribution of wavefront with low resolution. The conventional incoherent phase detection methods require two CMOSs placed in different positions, estimating the phase information of wavefront by the exact difference between the diffraction images. This detection system has disadvantages of complexity and uncertainty. In this article, we propose to use a broadband light as the illumination light source, and the single-shot color image is needed as the input of the neural network. Gradient descent algorithm functions is used as the optimizer to complete the phase reconstruction. Both simulation and experimental results show that this technology combines physical models with neural networks to achieve phase reconstruction with high resolution, high speed, low cost. As the mean square error function (MSE) to evaluate the quality of reconstructed images, the minimum value of this method can reach 0.089 rad, and the phase reconstruction quality of transparent cells is 0.133 rad, which is better than the GS method (0.320rad) and the TIE method (0.378 rad). In consequence, the phase reconstruction method of broadband light source based on neural network can be used in adaptive optics, live cell biological real-time imaging field, etc.

Dynamic laser speckle scattered by blood flowing in a vessel is studied in frequency domain. The power spectrum of the speckle field is derived based on single scattering approximation, and an algorithm is proposed to obtain the power spectrum from the speckle intensity. Results show that the spectrum is generally determined by three parameters: the ratio of static and dynamic speckle field, the characteristic frequency and the fixed doppler shift. Algorithm to get these parameters from a simulated power spectrum is presented, which shows a good accuracy. Procedures to measure the flowing velocity and the random movements based on the parameters are developed.

To observe the clinical effect of modified Jingfangfang combined with low-level light therapy with light-emitting diodes (LED-LLLT) on wind-heat type Facial Corticosteroid Addictive Dermatitis (FCAD), 83 patients with wind-heat type FCAD were randomly assigned to 41 cases in the treatment group and 42 cases in the control group. Patients in both groups were treated with skin barrier repair agents and 830 nm/ 590 nm LED-LLLT externally, and the treatment group was additionally given modified Jingfangfang internal medication, both for 8 weeks. Pruritus, burning, erythema, pain, tightness and Dermatological Life Quality Index (dermatology life quality index,DLQI) scores at different times before and after treatment were compared, and clinical efficacy of skin barrier function, serum IFN-γ levels and IL-4 levels before and after treatment and evaluation were detected. Results show that 4 weeks after treatment, the total effective rates were 75.61% in the treatment group and 54.76% in the control group. 8 weeks after treatment, the total effective rate of the treatment group was 92.68%, and that of the control group was 76.19%. It demonstrates that the treatment group was better than the control group, and the difference between the two groups was statistically significant (P<0.05). At 2 weeks, 4 weeks, and 8 weeks after treatment, the scores of itching, burning, pain, tightness, and erythema area decreased in both groups (P<0.05). Meanwhile, the scores of pruritus in the treatment group were lower than those in the control group at the same time (P<0.05). At 8 weeks after treatment, the erythema area scores were lower the treatment group than in the control group (P<0.05). DLQI scores of the treatment group were lower than those of the control group at 4 weeks and 8 weeks after treatment (P<0.05). After treatment, TEWL decreased, epidermal water content increased, and stratum corneum thickened in both group, with the treatment group outperforming the control group (P<0.05). IFN-γ levels and IL-4 levels of the treatment group and the control group were significantly different from pre-treatment (P<0.05). Modified Jingfangfang combined with LED-LLLT to treat wind-heat type FCAD can significantly improve the symptoms of patients and the quality of life.