At present, laser cladding technology has been widely used in the automotive and aerospace fields, which has great advantages in high-value material repair and material surface enhancement. Continuous laser and rectangular pulse waveform laser are commonly used in the laser cladding process, but few researches focus on the influence of other different laser waveforms on the performance of the cladding layer. This paper studies the geometric characteristics, microstructure, and microstructure of 316L stainless steel by different laser waveforms (continuous, rectangular pulse, ramp-up, ramp-down, mixed ramp) single-channel monolayer experiments. The effect of hardness. The results show that the molten pool generated by the continuous laser waveform has the largest cladding layer size, the coarsest microstructure, and the lowest hardness due to the low cooling rate. The two waveforms of ramp-up and ramp-down have low heat input, small size of cladding layer, and the characteristics of gradual heating and gradual cooling, so that the cooling rate of the molten pool is limited and the grain size is slightly larger. The size difference of the cladding layer produced by the rectangular pulse waveform and the mixed waveform is not significant, but the cladding layer exhibits the most detailed microstructure and the highest hardness due to the highest cooling rate of the molten pool under the rectangular pulse waveform.

In order to improve the performance of laser cladding Ni-based cladding layer on impeller surface of centrifugal pump, (Ti,W)C particles were added. The microstructure of WC hard phase and Ni base alloy was characterized, and the wear resistance was tested. The results showed that the cladding layer with dense structure is formed and the overall microstructure is uniform. The (Ti,W)C particles are partially remelted by laser with high energy density and solidified with the melted nickel-based powder. The remelted 45 steel matrix solidifies and forms a new phase. There are Fe3Ni, Cr23C6, and W2C phases on the surface of the cladding layer. The microhardness of the cladding layer is 623 HV, which is significantly higher than that of 45 steel. The friction coefficient of (Ti,W)C particle reinforced Ni-base cladding layer is 0.32, which is reduced by 47.2% compared with the matrix. Compared with 30.83 mg of 45 steel, the wear amount decreased to 9.67 mg. There are grains of different sizes on the surface of the cladding layer, and no furrow structure is formed. The wear marks contain C, Ni, W, and Cr, which can effectively protect the matrix structure and make it show better wear resistance.

Laser cladding was used on the surface of 18CrNiMo7 tool steel to produce Ni-based coating whose microstructure and mechanical properties were tested and analyzed. Results showed that there is no crack in the coating, and the microstructure is uniform with a lot of fine equiaxed dendrites and eutectic structures. After high-frequency quenching, the surface hardness of 18CrNiMo7 is up to 625 HV, which is higher than that of uniform coating, and the hardness of interlining coating is fluctuated. During wear process, plastic coating occurs on the surface of 18CrNiMo7 substrate, presenting adhesive wear characteristics. Under the action of pulse laser, the addition of WC particles to uniform coating makes finer microstructure that improves and the coating hardness and reduces adhesion wear rate. The WC particles in the Ni60A composite layer interact with the pulse laser to form a fine internal structure, presenting a dispersion distribution state, which improves the impact resistance of the Ni60A composite layer. Therefore, the wear resistance and impact resistance of the coating are enhanced. This study proves to be a reference for surface modification of other materials by wear and impact.

In order to explore the optimal process parameters of selective laser melting forming of TC4 titanium alloy, the effects of scanning speed, laser power, and scanning distance on the process parameters were analyzed with the densification degree and microhardness as evaluation indexes. The process parameters were optimized by orthogonal test, range analysis, and genetic algorithm. The results showed that the influence of laser power, scanning distance, and scanning speed on density and microhardness is the largest. At the same time, when the scanning speed is in the range of 980-1 024 mm /s, laser power is 205 W, and scanning distance is 0.05 mm, the density of TC4 titanium alloy forming parts can reach 95% and Vickers microhardness can reach 420 HV, which is higher than the hardness of traditional forging parts.

Ni60 coating was obtained by laser cladding on the surface of 304 austenitic stainless steel used for cutting tools. The hardness, wear resistance, and corrosion resistance of the cladding layer were studied by experimental testing. Results showed that there are mainly planar and cellular crystal structures at the bottom of the coating, a large number of columnar crystals in the middle of the coating, and many small-sized equiaaxial crystals appear near the depth of 200 μm from the upper layer. The maximum hardness at the top of Ni60 coating is 710.2 HV, with an average of 593.1 HV, which is nearly two times higher than that of the base material. The hardness of the boundary between coating and substrate reaches 252.3 HV, which is significantly lower than the average hardness of coating. The average friction coefficient of Ni60 coating is 0.08, which forms a surface with great hardness and better lubrication performance than the base material. Finer wear marks occur on the Ni60 coating after abrasion, without obvious spalling and plastic deformation. The abrasion loss is 3.2×10-5 mm3/(N·m), which is lower than the base material by an order of magnitude. The research has a good theoretical value for improving the wear resistance and service life of cutting tools and is easy to be used broadly.

Selective Laser Melting (SLM) is an additive manufacturing technology that builds layer-by-layer through a laser-scanned powder bed. The AlSi10Mg alloy formed by SLM has a high density and can ensure the overall quality of the structure. In this paper, the relationship between laser power, scanning speed, scanning distance, and the quality of SLM was determined through FLOW3D numerical simulation. The microstructure and mechanical properties were analyzed under the optimal process parameters. The results showed that the linear energy density will increase with the increase of laser power, resulting in a gradual increase in the width of the single-channel molten pool, so the forming quality increases. With the increase of scanning speed and scanning distance, the density of SLM molding decreases. Under the optimal process parameters, it is found that the internal microstructure distribution of the SLM-formed AlSi10Mg sample is uneven, and there are fine-grained, coarse-grained, and heat-affected zones. The ultimate tensile strength at room temperature can reach 219 MPa, the yield strength can reach 153 MPa, and the impact energy can reach 5.8 J. The surface hardness of XOY plane and XOZ plane are (130±5) HV and (120±5) HV, respectively. Through experimental comparison, it can be found that the mechanical properties of the SLM-formed AlSi10Mg sample are much larger than that of ZAlSi9Mg, which is close to the extruded 6061 aluminum alloy and can meet the application requirements of rapid additive manufacturing.

In the laser direct metal deposition forming, surface flatness is the key to its forming quality. To obtain the ideal surface flatness, ER-2209 wire was selected, and the weld seam was shaped based on a single-layer, single-pass fusion weld by laser side-axis feeding. MATLAB software was used for image processing, seam feature extraction, and mathematical fitting. The experimental results show that the parabolic model of the conventional weld differs greatly from the characteristics of the actual clad weld. In order to ensure that the error is controllable and at the same time avoid the generation of unfavorable factors, after several groups of fitting results of different orders are compared, it is found that the use of the 6th order function is a better fit for the experimental object. The optimal fitting function can be derived from the fitting results of the weld curve, and then the best theoretical lap rate can be solved by using the idea of differentiation to establish the mathematical model of optimal flatness. The surface flatness model proposed in this paper was verified by 5 sets of single-factor laser side-axis wire feeding lap experiments. The results show that the weld surface flatness is a function of weld characteristics and interlayer offset, and the theoretical optimum lap rate of the model is 30.46%, ideally between 30% and 35% for experimental verification, the theoretical optimum lap rate holds within the allowable experimental error. In the actual laser side axis feed wire fusion forming process, small flexible adjustments based on the theoretical optimal lap rate can be made according to the actual situation.

In this paper, The ABAQUS software was used to establish a 5083/AZ31B dissimilar alloys model by using the life and death element method. The distribution of welding temperature field, residual stress field, and welding deformation under different laser powers were studied. The results show that the temperature field has an elliptical distribution during the welding process. With the increase of the laser power, the aspect ratio of the weld increases, the maximum welding temperature increases. The temperature field distribution has no effect. Cooling for 20 s after welding, the temperature drops to 160 ℃, and the heat dissipation on the AZ31B side is faster. The heat dissipation will be accelerated with changing the laser power. When the workpiece is completely cooled, the temperature distribution on both sides of the dissimilar alloy plate is semi-elliptical. The residual stress at 3 000 s after welding presents a distribution state of large and small ends in the middle. The longitudinal stress of the workpiece is the tensile stress of 232 MPa at the weld, and the maximum transverse stress is 225 MPa that is also distributed near the weld. The residual stress at the weld toe changes largest. When the workpiece is completely cooled, the post-weld deformation presents an approximately elliptical distribution near the center of the weld and small at the edge of the workpiece. The highest deformation of the workpiece surface is distributed at the end of the weld. The unit deformation is 0.405 mm. The laser power will increase slightly by 0.02 mm deformation amount.

Surface modification of 800H high temperature alloy welded joint was carried out by laser shock strengthening process. The influence of microstructure evolution and residual stress on welded joint was studied, and numerical simulation of welding and laser shock was carried out by Abaqus. Results show that laser shock strengthening can significantly refine the grain size of welded joints. Impact strengthening can effectively improve the residual stress distribution near welded joint surface, and stress distribution changes from 165~216 MPa to -212~-98 MPa. The stress distribution trend after impact strengthening is basically consistent with the numerical analysis results. The numerical analysis results can provide reference for laser impact weldment.

Laser plate cutting not only improves production efficiency, but is also easier to adapt to changing production needs. At present, laser cutting has been widely used in automobile part cutting. However, single laser cutting is the most widely used in both theoretical research and practical production. However, in large-scale industrial production, this cutting method cannot meet the production needs. To further improve the cutting efficiency of automobile parts, dual laser collaborative cutting path planning was studied. First, the mathematical model of double laser collaborative cutting was established. Second, a fuzzy clustering vaccine immune algorithm was proposed to plan the double laser cutting path. Finally, the irregular polygon samples provided by the ESICUP website and actual automobile part data were selected for algorithm simulation verification. Experimental results show that compared with the traditional GA/IA algorithm for single laser cutting path planning, the laser cutting path planned by the proposed algorithm has a shorter empty travel and higher stability.

Due to the feature of remote transmission by optical fiber, laser shocking peening with low pulse energy has a wide potential application in the field of on-site strengthening and life extension for large-sized mechanical components. In this work, finite element method was employed for the simulation of the laser shocking dynamic procedure and for the analysis of the static residual stress field in AISI 420 martensitic stainless steel, a typical material for the last-stage of steam turbine blades. Using Abaqus/Explicit dynamics, temporal distribution of the laser shock energy and von Mises stress were analyzed. Based on the Johnson-Cook plastic flow constitutive model, the residual stress and plastically-affected depth were comprehensively analyzed with parameters of pulse time, shot times, and peak pressure. The results indicated that laser shocking with low pulse energy has similar effect in terms of residual stress distribution with that obtained from high pulse energy. This trend also complied well with published experimental data.

The modified layers were prepared on the surface of 40Cr samples by two composite processes of plasma nitriding followed by laser quenching and plasma nitriding followed by laser quenching, the phase characters of the modified layer were analyzed by microhardness, metallographic and x-ray diffraction, the electrochemical and friction experiments were carried out to compare the surface properties. The results show that the surface of the post-laser quenching process consists of α′ phase, low nitrogen compounds and oxides which are mainly composed of Fe3O4, the surface hardness is 818 HV, the thickness of the modified layer is 1 100 μm, the hardness gradient is gentle, and the wear resistance is better. The surface of the post-plasma nitriding process is mainly composed of γ′-Fe4N and α′ phases, the surface hardness is 970 HV, the thickness of the modified layer is 500 μm, and the corrosion resistance is better. Different phases of the modified layers by two composite processes lead to differences on the corrosion and wear resistance, and the composite process should be selected according to the working conditions.

In order to investigate the effect of laser processing parameters on surface roughness Ra and tool wear VB of zirconia ceramics, a fiber laser and a CBN tool were used to turn zirconia ceramics. Taguchi orthogonal experiment with four factors and four levels of laser power, spindle speed, feed speed, and backstroke was designed by Minitab, and the main effect of taguchi experiment was analyzed. The results showed that the order of influence of various process parameters on surface roughness Ra is laser power, backdraft amount, feed speed, and spindle speed. The order of influence on tool wear VB is laser power, backdraft amount, spindle speed, and feed speed. The higher the laser power, the smaller the amount of the back, the smaller the surface roughness of the workpiece, and the lighter the tool wear. Taking the minimum roughness of workpiece surface and the minimum tool wear as indexes, the optimal process parameters are obtained as laser power of 125 W, spindle speed of 550 r/min, feed speed of 5 mm/min, and backdraft of 0.2 mm. Compared with the experimental results of non-laser-assisted turning, laser-assisted machining is further verified that it can greatly improve workpiece surface quality and reduce tool wear.

Improving the aeration efficiency of traditional microporous aerator by changing the surface wettability is of great significance to improve the efficiency of sewage treatment. In this paper, Janus aluminum foil with asymmetric wettability on both sides is prepared by laser bionic manufacturing technology. Janus aluminum foil is applied to the self-made aerator to produce uniform ultra-fine bubbles for high-performance aeration, so as to speed up the decomposition efficiency of ammonia nitrogen by nitrifying bacteria in aerobic biofilm and improve the efficiency of wastewater treatment. The results show that the decomposition rate of ammonia nitrogen using Janus aluminum foil aerator is nearly three times that of double-sided superhydrophobic aluminum foil. This simple and low-cost method of laser manufacturing Janus aluminum foil shows great potential in improving oxygen mass transfer and energy efficiency in sewage treatment process.

In order to investigate the effect of laser shock peening (LSP) and heat treatment on the surface properties of TC4 titanium alloy, LSP was applied to TC4 titanium alloy specimens. The surface hardness and corrosion resistance of the surfaces before and after LSP and heat treatment were analyzed by using microhardness tester and an electrochemical workstation. The surface and cross-sectional morphology and microstructure were analyzed through laser confocal microscopy and SEM. The results show that the surface hardness of the specimens strengthened by one and two LSP impacts reached 425.4 HV and 456.5 HV respectively, an increase of 12.3% and 20.5% compared to the original specimen. After heat treatment, the surface hardness of specimens further increased to 465.1 HV and 483.2 HV respectively. The self-corrosion potential was positively shifted and the corrosion current density decreased after LSP. The corrosion rate of the specimens was reduced by 36.2% and 4% compared to the original specimen after one and two impacts, respectively. After heat treatment, the self-corrosion potential of TC4 specimens shifted negatively, the corrosion current density increased, the corrosion rate increased, and the corrosion resistance decreased.

As an important geographical environment resource in China, the lake area is of great significance for ecological protection and environmental governance by obtaining high-precision terrain in this area. In order to obtain high-precision topographic data in the lake area, a variety of filtering methods under the point cloud data were studied. Meanwhile, considering the characteristics of progressive encryption triangulation network filtering and cloth simulation filtering itself, the progressive encryption triangulation network filtering and cloth simulation filter fusion filtering methods were introduced to reduce the influence of seed point selection and terrain undulation on the filtering algorithm. With the help of noise point constraints, largescale and small-scale noise were firstly processed respectively to obtain relatively clean point clouds. Secondly, CSF multi-scale acquisition of seed points to be determined was used to complete the acquisition of final seed points by TPS interpolation. Finally, the triangulated network encryption was carried out to obtain ground points. Taking three special areas (construction area, vegetation area, and fish pond area) of Weishan Island as examples, the applicability of the three methods was compared and analyzed. Among them, the fusion filtering algorithm was used in the three sets of data, and the overall error were 0.19%, 2.96%, and 7.32%, which were reduced by 22.44% and 3%, 13.57% and 1.39%, 24.02% and 14.14% compared with the PSD and CSF filtering algorithms. Although the total error of the three algorithms increased in the fish pond area, the accuracy of the fusion filtering algorithm was still the best, and the results showed that the fusion filtering method had the highest accuracy, which was more suitable for multi-type complex regional point cloud filtering.

The content of calcium in milk is very important for the quality of milk as it can provide an important source of nutrition for the human body. It is of great significance to quickly determine calcium in milk. In this work, picosecond laser ablation spectroscopy was used to achieve quantitative analysis of calcium elements in milk with the emission spectral lines selection and calibration curves of calcium in milk. The linear fitting coefficient was more than 0.99, showing a good fitting effect. At the same time, the measurement setup was built on a breadboard, which could achieve portable, online, and rapid detection. The calcium element in random milk was detected by this technology, and the detection error was controlled below 2%, which verified the accuracy of the detection. This work realizes the real-time and online rapid detection of calcium in milks with different calcium content, which shows positive significance for the online quality inspection of products and the rapid analysis of calcium concentration.

In view of the shortcomings of the existing light plane calibration, a method of calibrating line-structured light is improved. Firstly, this method uses the improved Steger algorithm to extract the subpixel center of 2 or more laser stripes projected at different heights or angles of the checkerboard calibration board. Secondly, using the constraint of the checkerboard grid world coordinates =0 in Zhang Zhengyou′s camera calibration method, the camera coordinates of the center points of the laser stripes are calculated, and then the ordinary least squares is used to calculate the light plane. A different method from the traditional direct-beam trigonometric method is used to find the height of the object and a new evaluation method is proposed because of no clear standard for the accuracy of the light plane calibration. Experimental results show that the accuracy and robustness of the algorithm are good. For the three blocks with different heights, the maximum of root mean square error is 0.063 mm and the minimum is 0.023 mm.

In the process of reverse engineering, due to the influence of instrument accuracy, human disturbance, complex environment, and other factors, there will be a large number of noise points and uneven distribution using laser scanning equipment to obtain point cloud data. This will have a certain impact on subsequent point cloud processing and model reconstruction. A point cloud denoising algorithm combining statistical filtering and spatial density clustering algorithm (DBSCAN) is proposed for this purpose. This algorithm firstly establishes the topological relationship of the point cloud through the K-dimension (kd tree) to accelerate neighborhood searching speed and complete coarse denoising of the point cloud data. Secondly, by improving the neighborhood radius selection method of the density clustering algorithm, precise denoising of the point cloud data is achieved. At last, the point cloud in the scanning point cloud database of Stanford University and the measured machine element are selected for experimental verification. The experimental results show that, compared with a single bilateral filtering and radius filtering algorithm, this method can remove irrelevant noise while retaining the original geometric features of objects and meet the subsequent modeling accuracy.

Laser simulation shooting technology has the advantages of low cost, high safety, and strong simulation effect, which has been used in daily military training. Aiming at the problem of large far field light spot, an adaptive laser simulator for soldier training is designed in this paper. According to Mie theory, the laser power attenuation caused by atmosphere is calculated. the corresponding relationship between the distance of beam from the optical axis centroid and the optical power at this position are studied, and the corresponding beam model is established. The functional relationship between the optical power between 120~200 meters and the threshold spot diameter of the detector are analyzed, the driving circuit of the laser is designed, the adaptive control theory of the threshold spot of the laser is established, and the far-field spot is regulated based on the PWM output of STM32. Through adjusting the threshold spot diameter of the detector from large to small, the kill range of the simulator′s far-field firing is adjusted. Finally, the adaptive control system is verified through experiments, and the threshold light spot at 200 meters is adjusted to the ideal state, which solved the problem of hitting multiple people with a single shot from a distance, which improves the reliability, convenience, and practicability of the simulator.

Objective: To investigate the predictive value of three-dimensional ultrasound combined with neutrophil/lymphocyte ratio (NLR) and D-dimer in elderly patients with non-valvular atrial fibrillation. Methods: From January 2020 to December 2021, 102 elderly patients with non-valvular atrial fibrillation (observation group) and 100 healthy subjects (control group) admitted to our hospital during the same period were selected as the research objects. Cardiac examination, NLR expression level was detected by automatic blood cell analyzer, and D-dimer was detected by enzyme-linked immunosorbent assay. The differences in the detection results of three-dimensional echocardiography, NLR, and D-dimer between the two groups were compared, and the relationship between three-dimensional echocardiography, NLR, D-dimer and poor prognosis of non-valvular atrial fibrillation was analyzed by Logistic regression analysis. Receiver operating characteristic (ROC) curve analysis of three-dimensional echocardiography, NLR, and D-dimer in the prognosis prediction of non-valvular atrial fibrillation. Results: The detection values of LVEDV, LVESV, RVEDV, RVESV, NLR, and D-dimer in the observation group and patients with poor prognosis were significantly higher than those in the control group. Patients with good prognosis, while the detection values of LVEF and RVEF in the observation group and patients with poor prognosis were significantly lower than those in the control group. There was a statistically significant difference between the two groups and those with good prognosis (P<0.05). Logistic regression analysis showed that three-dimensional ultrasound (high expression of LVEDV, LVESV, RVEDV, and RVESV), NLR (high expression), and D-dimer (high expression) were the influencing factors of poor prognosis in non-valvular atrial fibrillation (P<0.05). The results of drawing receiver operating characteristic (ROC) curve showed that the combination of three-dimensional ultrasound, NLR, and D-dimer had the highest AUC (0.855, 95%CI: 0.768~0.942) in predicting the prognosis of non-valvular atrial fibrillation. The sensitivity and specificity were 92.65% and 91.18% respectively (P<0.05). Conclusion: Three-dimensional ultrasound (LVEDV, LVESV, RVEDV, RVESV high expression), NLR (high expression), and D-dimer (high expression) are the influencing factors of poor prognosis in non-valvular atrial fibrillation, which can provide quantitative reference for predicting the prognosis of non-valvular atrial fibrillation.