In order to improve the service life and performance of TC4 titanium alloy parts, design of multiple laser process parameters using orthogonal test method. Mg-Co alloy coatings were prepared on titanium alloy the surface by laser cladding process. The influences of current, pulse length and scanning speed on the dilution rate and aspect ratio of cladding layers as well as the interactive action among the each influencing factors are analyzed and verification experiments. Finally obtain the best process parameters of the titanium alloy single-track laser cladding. The results show that the scanning speed has the most significant influence on the dilution rate of cladding layer, while the pulse width has the most obvious influence on the aspect ratio of cladding layer. Through the contrast analysis, the best combination of process parameters was obtained, and provide experimental reference for later laser cladding of titanium alloy magnesium-cobalt alloy forming test.

Based on needs of repairing damaged TA19 titanium blisk of aero engine, a study focusing on laser forming repair process has been performed.TA19 powder prepared by plasma rotating electrode process, was used for laser forming, the samples were fabricated by laser forming in argon chamber. Both laser forming repair samples grown on base material and laser direct deposition samples were prepared. The microstructure, microhardness, tensile and fatigue strength of laser forming repair samples were investigated, and compared with base material and laser direct deposition samples. It is found that the sample fabricated by laser forming repair consists of laser repaired zone(RZ), heat affected zone(HAZ), and base material, laser repaired zone is metallurgical bonded with base material, coarse columnar grains in repair zone which grows parallel to deposition direction, an acicular αphase is formed inβgrains during rapid cooling stage which is known as widmanstatten structure. The microhardness of laser forming repair zone is 400 HV, which is 70 HV higher than that of base material. The average ultimate tensile strength and yield strength of laser forming repair samples were 999 MPa, 910 MPa respectively, which are basically equal to that of base material. The average elongation of laser forming repair samplesis 12.5%, which is reduced by 17% compared with base material. When the stress concentration factor Kt=3, the rotating bending fatigue strength of laser forming repair samples is 137 MPa at room temperature and 145 MPa at 450 ℃, which is comparable or slightly higher than that of base material. Laser forming repair process is a feasible approach for TA19 titanium blisk damage repair.

In this paper, fiber laser was used to clad Ni60 coating and Ni60+WC composite coating on the surface of high strength and toughness steel. The morphology of cladding layer under different process parameters was studied, and the influence of reinforcement phase on the microstructure of the cladding layer was investigated. Meanwhile the microstructure and hardness of the cladding layer before and after cryogenic were analyzed. The results show that the laser process parameters affect the microstructure of the cladding layer and no needle-like eutectic structure appears in the cladding layer of Ni60 with high laser power. After adding WC powder into Ni60 powder, grain refinement appears in the microstructure. For the Ni60 cladding layer with low hardness, cryogenic treatment results in precipitation of more carbides and thus high hardness. While cryogenic treatment contributes to refinement of microstructure and enhanced hardness of the Ni60+WC cladding layer with low hardness.

It is of great significance for the application of Ni-based single crystal superalloy in inhibiting the solidification crack and repairing the blade. The mechanism is to avoid the microstrucure transformed from columnar to equiaxed dendrites (CET), and to avoid the formation of dendritesin remelting zone. In this study, the relationship between crack sensitivity and grain size of DD6 alloy was investigated by laser cladding technology. The epitaxial growth of GH768 alloy deposited on DD6 single crystal superalloy was studied. The mechanism of laser processing parameters on the formation of single crystal structure was clarified. The results showed that with the increased of laser scanning speed, the grain size decreased, the regularity increased, and the solidification crack weakened. When the laser power was 250 W, the scanning speed was 2.5 mm/s, the lifting height was single layer was 100 μm, and the superposition rate was 41%, the solidification cracks could be eliminated and the damaged single crystal blade could be initially repaired.

Three sets of GH4169 samples were formed by selective laser melting technology using optimized process parameters, and high temperature fatigue test specimens were prepared. The porosity of the fatigue test specimens were measured by industrial CT, and the fatigue cycle tests were carried out at 650 ℃. The fracture morphology of the fatigue specimens was observed by SEM and the fracture mechanism was analyzed. The results show that some parameter sets pecimens have micropores of about 100 μm, which have no effects on fatigue fracture through subsequent analysis. The fatigue cycle number of the three sets samples do not change significantly with the change of process parameters, and all of them could reach 105~107 cycles, but the fatigue properties are lower than that of the forging part under the same test condition. The fracture morphology shows that the crack sources of are located on the surface of the specimens, and both brittle fracture and plastic fracture coexist in the process.

Using laser repair technology to repair cracks can effectively improve the fracture performance of parts.This paper takes 304 stainless steel compact tensile specimens as the research object, and establishes thermal analysis and mechanical analysis finite element models respectively. First, the temperature field distribution of the repair area around crack tipunder different laser process parameters was simulated, and the relationship between the dilution rate and the laser parameters was analyzed. Furthermore, the material composition of the repair zone was obtained from the relationship between the matrix material composition, the repair powder material composition and the dilution rate. Finally, the J-integral of the crack tip of the repaired 304 stainless steel specimen was simulated, and the influence of laser parameters on the J-integral of the crack tip was analyzed. The results show that when the laser spot diameter and heating time are constant, as the laser power increases, the J-integral at the crack tip decreases first and then increases, and the repair specimen has better fracture performance when the laser power is 1 800 W; When the power and heating time are constant, as the spot diameter increases, the J-integral at the crack tip decreases first and then increases. When the spot diameter is 3 mm, the repaired specimen has better fracture performance.

The surface quality of the porous scaffold was optimized by adjusting the laser power, scanning speed, and scanning spacing in the laser selective melting process parameters. The experimental results show that: the defects on the surface of the microporous scaffold are mainly microcracks and holes; as the scanning power gradually increases, the defects of the holes and microcracks are significantly reduced, and the density of the porous scaffold also increases; however, as the scanning speed and the gradual increase of scanning distance, the increase of pores and micro-crack defects, the dense and comprehensive mechanical properties of porous scaffolds decrease. Experiments show that when the art parameters are S=0.05 mm, P=130 W, V=500 mm/s, the surface of the microporous scaffold has the fewest defects, the best surface quality, and its highest density is 96.41%, and its compressive strength reaches the maximum. It was 583 MPa.

Ni-based alloy reinforced coating was prepared on the surface of 5CrNiMo steel, and the effects of scanning speed(6、8、10 mm/s)on the microstructure and properties of the cladding were analyzed. X-ray diffractometer、scanning electron microscope、energy spectrum analyzer、micro hardness tester and friction and abrasion tester were used to analyze and test the phase composition、microstructure、microhardness and wear resistance of the cladding The results show that the cladding layer is mainly composed of CrB2, Cr3B2, Cr7C3 and γ-Ni phases. With the increase of the scanning speed, the structure of the cladding layer is refined, the distribution is uniform, the micro hardness is increased, the amount of wear is reduced, and the friction coefficient is reduced. Laser cladding technology can successfully prepare Ni-based alloy reinforced coatings on the surface of 5CrNiMo. Choosing a suitable scanning speed can improve the microstructure of the cladding layer. When the tracing speed is 10 mm/s, the cladding layer has fine grains, dense and uniform structure distribution, and abrasion resistance and microhardness are significantly improved.

The application of laser cladding technology in thin-wall repair is limited by the instability deformation of the substrate. This paper discussed the characteristics of the instability deformation mechanism, the phase composition change of the fusion area and the surface layer of the thin-wall, the microstructure and microhardness and other properties through the test of laser cladding 2 mm thin-plate. The results show that the thermal stress plays a decisive role in the buckling deformation of 08 steel plate after 316L laser cladding. The fusion zone of thin plate surface produces a planar crystal fusion zone of about 5 μm brightness, and the phase content and mechanical properties of the fusion zone are close to that of cladding alloy. A single grain coarsening zone of 30 μm is generated in the heat affected zone of thin plate matrix. Due to the uneven residual stress, the materials around the micro indentation appear uplift.

The Selective Laser Melting (SLM) technology was utilized to fabricate high-strength TiB2/AlSi10Mg alloy. The effects of laser energy density E on the relative density, microstructure of the as-fabricated samples were researched by means of Optical Microscope(OM) and Scan Electron Microscope (SEM). The microhardness and tensile properties of the samples at different parameters were also investigated and the effects of various heat treatment(HT) condition on tensile properties of the SLM processed TiB2/AlSi10Mg were revealed. The results showed that the relative density of the sample improved and defects decreased with the increase of E. When E was increased to 71.5 J/mm3, there was only a few defects on sample section, and the clusters of TiB2 particles disappeared with a uniform distribution. Under this laser processing condition, the microhardness on the cross section reached to 138.9 HV0.5. Due to the addition of the TiB2 particle, the tensile property of the SLM-processed TiB2/AlSi10Mg alloy realized a tensile strength of 420 MPa and elongation of 6.13%, showing a 13.5% and 50% increcement respectively compared with the SLM-processed pure AlSi10Mg alloy. The temperature and time of HT also influenced the property of the TiB2/AlSi10Mg alloy and in this research, the relative optimized HT temperature and time were T=170 ℃, t=10 h, respectively.

This paper takes GH738 alloy parts as the research object, analyzes the effect of additive repair on the heat treatment and mechanical properties of GH738 alloy. Compared with the matrix, the size of γ 'phase in the heat affected zone increases significantly, its average size increases from 50 nm to 110 nm, and the average spacing increases significantly; the carbide content decreases in the heat affected zone, and some carbides decompose, The fracture micro morphology of laser deposition repair sample belongs to ductile fracture. After aging, the grain boundaries of the as deposited dendrites began to expand and merge, and new grains formed at the same time. After aging treatment, there are a lot of γ′ phase precipitated in the repair area, and the γ′ phase continues to grow with the increase of aging temperature, but the content of γ 'phase changes little. Compared with the deposited state, the tensile strength of the sample increased significantly after aging heat treatment, but the plasticity decreased; the plasticity of the repaired sample decreased with the increase of the effective temperature at any time. When the carbide on the grain boundary precipitates in the form of coating, the crack on the grain boundary propagates rapidly along the carbide on the grain boundary, and the mechanical properties of metal are seriously reduced.

The purpose of this paper is to study the optimal process parameters of laser cladding of 431CO-M2 alloy powder on the surface of 3Cr14 stainless steel. Based on the orthogonal experimental design, the method of range analysis was adopted to study the influence of laser power, cladding speed, powder feeding speed and protective gas size on the molding quality of cladding layer by taking dilution rate, forming coefficient and macroscopic hardness as evaluation indexes, so as to select the optimal cladding process parameters. The degree of influence on the dilution rate and forming coefficient is laser power, cladding speed, powder feeding speed, and protective gas size in descending order, The degree of influence on macroscopic hardness was laser power, powder feeding speed, cladding speed and protective gas size in order from large to small. The optimal process parameters are laser power 1 100 W, scanning speed 5 mm/s, powder feeding speed 26 g/min, protection size 0.1 MPa, spot diameter 4mm, carrying capacity 13 L/min, defocusing capacity 14 mm. Under the optimal process parameters, the surface of the cladding layer is continuous and smooth, and is closely combined with the substrate. The average microhardness of the cladding layer is 684.5 HV0.2, which is about 2.7 times of the average microhardness of the matrix, significantly increasing the hardness of the matrix.

In order to investigate the effects of different micro-textured surfaces on the coating properties of a cutting tool, fiber laser was used to fabricate the convex and groove micro-textured morphology of different area occupations. Then, the TiAlN coating was deposited on a textured sample surface by PVD magnetron sputtering. Nanofocus confocal microscopy was used to detect the texture morphology after coating; microhardness of the sample surface was measured by AMH-61 microhardness tester; residual stress on the textured coating surface was determined by D8 ADVANCE X-ray diffractometer; the coating surface was subjected to a scratch test using a Rtec MFT-5000 surface performance tester to characterize the coating/substrate binding force. The results show that the convex morphology with certain area occupation is beneficial to improve the microhardness of the coating, while the groove morphology has a weakening effect on the microhardness, and the area occupancy has little effect on it. Both textures can reduce the residual stress inside the coating, and the residual stress reduction is positively correlated with the texture area occupancy. The convex is more effective than the groove, and the bonding strength can be increased by up to 19.2%. The two different micro-textures have effectively improved the performance of coating on cutting tools’ surface.

The traditional ceramic molding process has the problems of low material utilization and high energy consumption. Therefore, this paper proposes a method of using digital light processing (DLP) to prepare zirconia ceramics with fine and complex structure. In the experiment, the ceramic-photosensitive resin paste with solid phase up to mass fraction of 72.5% was configured. Using ultraviolet light as the light source, the paste was cured layer by layer and superimposed. The experiment studied the influence of exposure time, exposure intensity and other factors on the curing depth. The optimized ceramic slurry showed good curing efficiency and molding accuracy. This paper also studied the effects of sintering temperature on the density and Vickers hardness of ceramic devices. Finally, a zirconia ceramic microdevice with density of more than 95%, Vickers hardness of 11.3 GPa, and XRD characterized as tetragonal phase was fabricated, which achieved rapid printing preparation of complex ceramic devices.

When the surface pollution of the insulator is cleaned by pulsed laser, the great temperature difference will produce great thermal stress. If the thermal stress is greater than the adhesive force, the pollution layer will fall off. This paper took porcelain insulator and its surface pollution as the object, established the finite element model, analyzed the change law of thermal stress field generated by temperature difference under different energy density, studies the pollution mechanism of pulsed laser cleaning insulator, and determined the optimal cleaning energy density. Also, the cleaning effect has proved by laser experiment.The results show that the first principal stress first presents as compressive stress, which reaches the maximum value at the center of the spot, and the maximum value can reach 1 240 MPa under the condition of ensuring safe cleaning. With the increase of diameter and depth, it is gradually transformed into tensile stress, and the maximum value at 0.014 mm below the center is 105 MPa, where the dirt is removed first. The laser energy density is 2.52 J /cm2~ 3.81 J /cm2, which can realize safe and effective cleaning. The results of this study provide an important basis for the selection of energy density of pulsed laser cleaning porcelain insulator.

Taking 316L/Q345 dissimilar steel laser welded joints as the research object, a bubble generation process model under keyhole instability conditions was established. It was concluded that the main reason for the formation of porosity were the retention of the bubble in the convective mixing zone and the adsorption of the solidifing interface on the bubble. The results of thermodynamic calculation showed that the change of surface free energy ΔGs of the solid-liquid interface attached by bubbles is less than 0, which further showed that the diffusion of bubbles to the solid-liquid interface was a spontaneous process; In addition, based on the fact that the characteristics of heat transfer, momentum transfer and mass transfer in the convective mixing zone are easier to meet the conditions of crystallization thermodynamics and kinetics. Meanwhile, a macrosegregation formation process was established for the cross-section of the laser welding joint penetrating through the keyhole.It is considered that the crystallization first occurs in the convective mixing zone, and the non mixed boundary layer was brought into the weld is overcooled under the action of the flow of the pool, forming “island organization”;or weld metal invaded the non-boundary mixed layer, forming a “beach organization”.

In this paper, Nd:YAG laser welding machine was used to process research on dual-phase steel. Respectively, three group parameters were selected in current, pulse width and frequency. Orthogonal experiment method was used to analyze the influence of welding quality. Range analysis was carried out on the measurement results. The best parameters selected were: current was 110 A, frequency was 14 Hz and pulse width was 1.4 ms. Furthermore variance analysis was carried out. It was founded that the influence of current on welding quality was more significant than frequency, and the pulse width almost had not influence in this experiment.

The black high temperature resistant polyester film was processed by a 60 W domestic CO2 laser. The influence of laser scanning speed, power, repetition frequency, defocusing amount and pulse width on the optical aperture, optical aperture and taper of the micropore was analyzed by orthogonal experiment. The optimized process parameters were obtained by comprehensive balance method. The results show that the laser scanning speed, defocusing amount and pulse width have great influence on the micro hole taper, defocusing amount and power have great influence on the aperture, and the optimized technological parameters are as follows: laser scanning speed 50 mm/s, power output 10%, repetition frequency 11kHz, The defocusing amount is 0 mm, and the pulse width is 0.1 ms. through the experiment, it is verified that the microporous optical aperture, optical aperture and taper obtained by the optimized parameter group are small, and the quality is good, which guides the upgrading of the enterprise production.

A computational model of the heating and ablation of semiconductor materials under repetitive laser pulses is described. By finite element method, the front and rear surfaces’ temperature increase and ablation depth of two semiconductor materials (Si and Ge) under repetitive laser pulses of different duty ratios are computed and analyzed, the influences of material thickness being studied. The numerical results show that under repetitive laser pulses radiation, the front surface temperature increase of semiconductors, like metals, presents a typical tooth-like profile; while the rear surface temperature increases in a step-by-step manner, which is different from that of metals. Also, repetitive laser pulses have more efficiency for heating and ablation on semiconductors than the CW laser.

Laser cutting has been widely used in the manufacturing process of front wheel shock absorber packages for all Changan Ford models. However, due to the complexity of the manufacturing process and numerous influencing factors, in order to meet the quality requirements, stable production, the kerf quality is assessed by the dross height and the fraction of oblique striation zone of the lower part of kerf, and the effects of process parameters such as laser power, cutting speed, defocusing distance and assistant gas pressure on the kerf quality are systematically investigated. And use the method of objective optimization to optimize the model. The results show that the laser power 3 408 W, cutting speed 43.1 mm/s, defocusing distance -3.27 mm can get the best kerf quality. The study provides the basis for process commissioning and quality optimization for the launch of new models.

Based on femtosecond laser and UV laser processing technology, this paper studies the laser fine processing technology experiment of copper, aluminum and titanium. The experiment of cutting metal sheet by UV laser shows that the spot diameter of UV laser can focus to small size, the width of cutting seam is small; when processing metal materials with high melting point, there is serious slag splashing; aluminum sheet processing The plasma has a great influence on the surface of copper. The femtosecond laser single pulse has a large energy, the heat affected area of the micro groove processed is small, the surface is relatively smooth, there is no slag deposition, and the effect of micro groove edge processing has a good consistency; in the three kinds of metal materials, due to the large thermal conductivity of aluminum, the low melting point, the short coupling time of electronic lattice, the femtosecond laser processing aluminum sheet has the thermal effects of surface grain growth, crystal recasting, etc, The processing effect is worse than that of UV laser, but the processing effect of titanium and copper sheet is better than that of UV laser. The laser pulse width is the difference between the ablation of metal target by ultraviolet laser and femtosecond laser. The ablation time of UV laser is determined by the pulse width of laser, while that of femtosecond laser is determined by the relaxation time of electronic lattice. The metal is removed by melting and gasification, and the slag on the surface of the micro groove is easy to deposit. The femtosecond laser is removed by direct gasification, and its heat affected zone is smaller than that of UV laser.

A 10 kW fiber laser was used to perform laser cutting process experiments on 10 mm thick 2A12 aluminum alloy. The effects of cutting speed, auxiliary air pressure, defocus amount, nozzle diameter, and nozzle height on cutting quality were systematically studied. During the study, the cutting quality was evaluated on the basis of the striation morphology and the height of dross. Firstly, through the single-factor experiments, the optimal parameter interval of the defocus amount, the nozzle diameter, and the nozzle height was determined. Then, full-factor experiments were performed. The results showed that there is a cutting speed interval that can obtain good cutting quality under a certain auxiliary air pressure, and increasing the auxiliary pressure to a certain extent will increase the speed interval.For 10 mm thick aluminum alloy laser cutting, the best process parameters are obtained: laser power 9 kW, cutting speed 1 750 mm/min, auxiliary air pressure 20 Bar, nozzle diameter 3.0 mm, nozzle height 0.8 mm, defocus amount -7 mm. The analysis of the recast layer of the laser cutting section shows that the precipitated phases become continuous distribution at the grain boundaries and diffuse distribution within the grains, which will have a strong hindrance to the movement of dislocations and improve the resistance to crack initiation on the surface of the material to a certain extent.

Benefits from the low thermal budget, the possibility to approach a high temperature in a short time, highly controllable fabrication process, highly reproducible ability in fabrication, the laser anneal technique has been used in semiconductor industry widely. The paper will introduce the study of mechanism for laser anneal technology at the early stage briefly, and further the application of laser anneal in the field of silicon solar cells, flat panel display, integrated circuits, and micro/nano fabrication.

High power diode lasers have been used in the fields of pumping source of solid state laser, surface modification, welding, cutting and so on for their high energy conversion efficiency, good reliability, long lifetime and small size. A novel collimator based on double focal lens are proposed, which could collimate the diode laser array in both directions simultaneously, to solve the question of bad collimation effect of diode laser array with high fill factor. Because the parameter design of the SAC and FAC are limited by the compact space of diode laser array with high factor, the double facol lens is the only way to achieve collimation with reducing the installation and adjustment deviation.

This paper proposes a method of obstacle detection based on 3D vision sensor, which is used to avoid false detection and missed detection of obstacle for robot navigation in quasi-static scenes. The algorithm firstly performed coordinate system conversion on the point cloud data obtained by the 3D vision sensor. Secondly, the depth image was generated with the height value as the scale factor, and then it was compared with the obstacle height parameter to generate the binarized image. Finally, we calculates the maximum connectivtity of the binarized image, and the size of field identifies the obstacle. The algorithm is used in the substation power inspection robot safety inspection project to verify the stability and effectiveness of the algorithm through long-term complex environment operation.

Based on three-dimensional laser scanning, taking a modern mine in Xinjiang as the research object, this paper studies the measurement technology of surrounding rock deformation of its mine development roadway. In the mapping of mine soft rock roadway, according to the actual situation of the survey area, the cloud data acquisition method based on the target point is selected. At the same time, the appropriate measuring points are selected, and the parameters such as scanning maximum measuring range, point cloud sampling density are set. Aiming at the single site 3D laser scanning point cloud, a tunnel modeling method based on cylindrical projection surface is proposed, which can quickly realize the automatic point cloud data modeling. The experiment shows that the method proposed in this paper has very high precision in the construction of three-dimensional model of mine roadway. The precision of the model is determined by the precision of the acquired point cloud. Through the analysis and evaluation of the calibration field, the precision of the point cloud data is ±4.8 mm and ±6.4 mm respectively when the scanning distance is 41 m and 81 m. Compared with Leica Cyclone 9 method, this method has the characteristics of automation and high efficiency. The method based on cylindrical projection surface provides a feasible method for the tunnel point cloud modeling, and provides the research basis for the subsequent tunnel point cloud modeling based on multi site.

In this paper, the application of airborne lidar in engineering survey and geological survey is studied. Combined with the actual work of pipeline engineering, aerial photogrammetry technology and airborne lidar technology are used to measure long-distance pipeline. Through the analysis of lidar flight, ground control survey, laser point cloud data processing and DEM generation image data processing and DOM generation, digital line drawing (DLG) production and so on, the corresp onding product results were obtained. In the long-distance pipeline measurement, the UAV airborne lidar technology can replace the traditional measurement method. The application of this technology can effectively ensure the quality and duration of survey and design, and the product quality, accuracy and effect to meet the requirements.

In order to achieve high-precision distance measurement, this paper proposed a distance measurement method using linear sweep of AOM acousto-optic modulator. Based on the interference theory, a mathematical theoretical model between ranging distance, phase and frequency was established. In the ranging experiment, using the AOM acousto-optic modulator dual-pass frequency sweeping scheme, a ranging optical path experiment system was built to generate dual-frequency component light. Through the photodetector, the optical signal in the experiment was converted into an electrical signal. Because the non-optical interference signal was generated, the relevant electronic devices are added in the experiment to perform signal demodulation processing. Finally, the experimental data was processed by FFT transform, and the results show that the ranging distance is 24.17 m and the ranging fluctuation range is ±0.22 m.

The solidification of the solid rocket motor lining is a key step of the solid rocket motor, and its state will affect the final performance of the rocket motor. The curing process of silicone sealant was monitored by laser ultrasonic on-line monitoring platform. This method combines the empirical mode decomposition (EMD) algorithm to process the laser ultrasonic echo signal, and characterizes the curing state according to the changes of ultrasonic propagation velocity and ultrasonic attenuation. The monitoring results show that, as the curing reaction progresses, the propagation speed of the ultrasonic wave increases rapidly, then decreases slightly, and finally stabilizes. The ultrasonic attenuation first decreases rapidly, then decreases slowly, and finally stabilizes. This fully reflects the entire curing process and can determine its semi-cured state, laying the foundation for non-contact online monitoring of the curing state of the lining.

In order to use laser ultrasonic technology to detect the surface crack depth of the sample, a laser ultrasonic non-destructive testing model was established based on the thermal-solid coupled physical field of the finite element analysis software (COMSOL), and cracks of different depths were simulated. Based on this, the quantitative calculation formula of crack depth was deduced according to the propagation law of ultrasonic waves in metal and the crack depth was calculated by experiments. The calculation formula was highly accurate. The results show that as the crack depth increases, the reflected shear wave SR at the bottom of the crack also increases, and the two have a linear relationship. The quantitative formula for crack depth proposed in this paper has higher accuracy, and the relative quantitative error of crack depth does not exceed 7%.

Aiming at the problem of online monitoring of laser paint removal, an acoustic monitoring experiment platform was built to study the acoustic monitoring technology of the laser paint removal process. Combining surface topography and signal processing, through time domain and frequency domain analysis, a series of characteristic parameters such as the peak value of positive pressure of the sound wave, the duration of the pulse waveform, the cleaning frequency component, the DC component and the frequency of the first spectral peak are found.According to these parameters, the discriminant function is obtained through the stepwise discriminant analysis method.Research shows that the acoustic signal of laserpaint removal can provide effective characteristics information, and the process of laser paint removal can be monitored through the recognition of cleaning characteristics.Acoustic monitoring has further practical potential.