By laser cladding magnesium-cobalt alloy on the surface of titanium alloy, the problems of wear on the surface of titanium alloy material and insufficient damping performance of the material in the aerospace field are solved. The laser power and magnesium-cobalt mixture ratio were compared and the experimental results were analyzed. The experimental results show that when the laser power is 235.2 w and the mixing ratio of magnesium and cobalt is 1∶300, the cladding effect is the best. The experimental samples under these conditions were characterized by scanning electron microscopy and eds elemental spectrum analysis. the results showed that ti elements in the matrix and co and mg elements in the cladding layer infiltrated each other after laser cladding, and the elements were evenly distributed in the matrix and cladding layer. The further test results show that the co and mg concentrations in the cladding layer have been increased to a certain extent by completely cladding the cladding material onto the surface of the substrate.

Focus on the question of specific powers for laser cladding, adjusted the ratio of material, The Fe55 alloy powder for laser cladding was prepared by vacuum gas atomization(VIGA). The influence of different atomized gas pressure and diameter of metal delivery tube on powder particle size distribution was studied. Under the optimum technological parameters, the composition and impurity content of the powder were tested. The morphology and phase structure of powder were observed and analyzed by SEM and XRD. The flowability of powder was tested by hall flow meter. Finally, the powder was subjected to laser cladding tests on 42CrMo substrate, and the hardness of the cladding coating was tested. The results show that when the atomizing gas pressure is 4.0 kPa and the diameter of the metal delivery tube is 6.0 mm, the powder particle size is mainly distributed between 80~600 mesh. The powder has lower impurity content, of which the oxygen content is 274 PPM, the nitrogen content is 296 PPM, and the sulfur content is 157 PPM. Powder morphology is mostly spherical or nearly spherical, with fewer satellite spheres. The powder phase structure is mainly composed of α-Fe、M-(FeCr) solid solution. The flowability of powder is 17 s/50 g. The powder exhibits good laser cladding properties, and the hardness of the cladding coating is between HRC 54.5~57.6.

In order to reduce the influence of residual stress on the quality of laser cladding layers, ANSYS software was adopted to establish a single-track model, the effect of process parameters on residual stress of cladding layers were investigated by using orthogonal test, and the optimized process parameters were obtained. The results show that scanning speed and laser power have greatly effect on residual stress, and next come spot diameter. The residual stress was calculated under the optimized process parameter combination, which is reduced to 192MPa. It provides guidance for selecting process parameters in experiments.

The mathematical model of laser cladding pool on titanium alloy surface was established using fluent software. The generation and development of molten pool under high intensity laser radiation are numerically simulated. The influence of laser irradiation time on the temperature field and flow field velocity distribution on the molten pool is analyzed. The width and depth of simulated molten pool and actual laser cladding channel was compared. The results showed that the temperature, flow velocity and geometric size of the molten pool developed rapidly within 0.1 second. And then the maximum temperature and maximum velocity of the molten pool tended to be stable after 0.2 second. The highest temperature is the surface center of the laser molten pool and the maximum fluid velocity is the surface edge. It is agree with the gaussian mode of laser energy source. Due to the heat loss and mass loss of the fluctuation and the splashing of the free molten pool, the width of the simulated molten pool is significantly larger than that of the actual melting channel.

Copper and its alloys are applied to the mold manufacturing industry due to its excellent thermal conductivity, and selective laser melting(SLM)technology can effectively form high-performance complex structure molds. At present, there are few researches on SLM forming copper and its alloys. The process parameters of SLM forming pure copper are systematically studied, and the microstructure, phase and mechanical properties of the pure copper blocks formed under the optimum process window are obtained. Under the optimal combination of laser power of 360 W and scanning speed of 600 mm/s, a pure copper sample with a density close to 88% was obtained. The Vickers hardness of the surface and side views were 42.9±6.8 and 32.8±4.5 HV, respectively. The average tensile strength and elongation of the samples were 95.0 ± 24.2 MPa and 8.9 ± 3.8%, respectively. This study provides theoretical and technological reference for the application of SLM formed pure copper to industry, especially mold manufacturing.

18Ni300 maraging steel was formed by selective laser melting(SLM)technology, the microstructure and mechanical properties of the deposited and heat treated states were investigated of the samples fabricated by SLM with 18Ni300 raw powder material. The results showed that the evolution mechanism of cell-columnar dendrites from the bottom to top of the micro-melting pool of the as-built sample is determined by the ratio of the temperature gradient to the solidification rate (G/Vs) at the front of the solid-liquid interface. However, the mutual transition of the hexagonal cell, the elongated cell and the strip structure existing in the microstructure is accomplished by geometric topology transformation. After heat treatment, the cell, columnar and sub-micron structures in the microstructure of the as-built sample disappeared, and precipitates fine lath martensite with fine granular precipitate. The mechanical properties test showed that the Vickers micro-hardness and tensile strength increased significantly after solution aging heat treatment, but the elongation decreased. At the same time, the fracture morphology presented a typical ductile fracture.

TC4 titanium alloy was prepared by selective laser melting forming. The microstructure of TC4 titanium alloy in the as-deposited and heat-treated state was analyzed. The tensile strength and elongation of TC4 titanium alloy in heat treated state were tested by tensile test. The results show that the as-deposited titanium alloy has almost all non-equilibrium phase α' under rapid condensation and the structure is fine. When the solution heat treatment process is 960 ℃, 2 h, AC, the titanium alloy structure is converted from the non-equilibrium phase α' to the equilibrium phase α, the structure is coarsened into a strip shape, and the tensile strength of the sample can reach 1 056 MPa. The elongation rate reaches 16.9%, and the entire section has uniform and evenly distributed equiaxed dimples, which are typical ductile fractures. TC4 titanium alloy obtains better strength-plastic matching under heat treatment.

We analyze the causes of longitudinal cracks from macroscopic and microscopic aspects in selective laser melting. The result shows that the mainly reason is the low energy of laser scanning. Then, testing the performance of the scanning optical system, the problem is focused to the optical system delays. To ensure that the cracks disappeared on the printed parts, adjusted the parameters of the optical system delay. Finally, according to the results of the samples (the density of the samples is 99.7% and the tensile strength is 626 MPa), to verified the laser too low scanning energy at this position is one of the factors in the longitudinal crack of the selective laser melting.

This work studies selective laser melting of 2Cr13 stainless steel. The main contents include the development of forming process parameters and the solidification behavior of molten pool under different process parameters. Besides, the microstructure observation test blocks are prepared and observed, mechanical property test blocks are prepared and tested, including Brinell Hardness, bending strength and room temperature tensile properties. The results show that when the forming process parameters are set as laser power 200 W, layer thickness 30 μm, spot spacing 75 μm, exposure time 110 μs, line spacing 115 μm, the density of the molded part reaches 99.75%. There is no hole in the formed part and the longitudinal section is lapped in the form of fish scales. The deposited parts have high strength, but the plasticity is poor and the performance shows an anisotropy. The lateral performance is similar to that of the forging but the longitudinal performance is weaker.

The performance of plasma-sprayed double-layer structure thermal barrier coatings (TBCs)can be effective improved by laser remelting. The present situation of domestic and foreign researches on plasma-sprayed double-layer structure TBCs by laser remelting is reviewed. Conventional laser remelting, step by step strengthen processing and one step strengthen processing are three types of main processing methods. The major problems of laser remelting plasma-sprayed TBCs were introduced and its solving measures were also pointed out. Finally, the development trends were also discussed.

Taking Q345B steel plate with a thickness of 10 mm as the base material, a series of studies investigated the influence of main process parameters of laser-DP TIG hybrid welding on the formation of welding seams, so as to provide experimental basis for the optimization of composite welding process. The experimental results showed that the laser acts as a shock and agitation on the molten pool, which improves the fluidity of the molten pool and forms a flat weld, and weld width is dominated by arc current; the laser power has little change to the weld width, and the weld penetration depths increases with the increase of laser power; the welding melt depth as well as the width increase first and then decrease with the increase of defocusing amount(-2~3mm); the welding penetration is bigger while the laser is in front of the arc.

The butt welding test was carried out on the 6 mm thick 5454-H24 /6106-T6 aluminum alloy sections by fiber laser-CMT hybrid welding processes. After the optimization of the process parameters, the well-formed welding joints were obtained. On this basis, the 1, 2 and 3 repair welding were performed respectively. The microstructure and mechanical properties of the joints after multiple repairs were analyzed, and the thermal crack sensitivity of the joints was evaluated. The results show that the weld cross section of the obtained butt joint and the three repairs joints are both typical "Y" type. As the number of repair welding increases, the weld width increases, and the corresponding heat affected zone (HAZ) range is wider. The microstructure of the weld zone is enlarged and the tendency of the pores is increased. The tensile strength and yield strength of the hybrid welded joint are reduced, and the welded joint is broken at the weld. After repair welding, the microhardness of the heat affected zone on the 6106 side decreased, while no obvious decrease occurred in the heat affected zone on the 5454 side. After the repair welding, the thermal crack sensitivity increases. Three repair welds can be carried out under the condition that the process is well controlled and the welding defects are reduced.

For the pressure-bearing stainless steel pipe for oil field, the laser welding and high-frequency welding test are carried out using 1Cr17Mn6Ni5N stainless steel (16Cr stainless steel) steel plate. The macroscopic morphology and microstructure of the weld were observed by OM and SEM, and the mechanical properties of the welded joint were tested. The results show that the laser weld has good weld formation, uniform microstructure, little difference between hardness and base metal, good bending performance and resistance. The tensile strength is 701 MPa. The high-frequency welding seam has the wrong side, the microstructure is not uniform, the ferrite content is high, the weld hardness is higher than the base metal 60 HV, the weld is cracked during bending, and the tensile strength is 679 MPa. It can be seen that laser welding of 16Cr stainless steel can obtain a good welded joint, so the laser welding method is selected to continue the process research.

A heat transfer model for low-frequency oscillation laser welding of 7075-T6 aluminum alloy was established. Then, the welding temperature field was obtained by means of numerical simulation. The effects of such welding parameters as laser oscillation frequency, oscillation amplitude, laser power and welding speed on the temperature fields both for conventional laser welding and for oscillation laser welding were studied and compared. The results showed that in conventional laser welding, the temperature field is totally symmetric, the welding temperature rises continuously; however, in oscillation laser welding, the temperature field is asymmetric, and the welding temperature goes up and then down for several times until it reaches the steady state. At the same laser power and welding speed, both the peak melting pool temperature and the heating rate for oscillation laser welding are lower than those for conventional laser welding. In low-frequency oscillation laser welding, the heating rate increases with the increasing of laser oscillation frequency and oscillation amplitude. As oscillation amplitude increases, the peak melting pool temperature decreases, and the width of the melting pool increases.

Laser welding of Q235 steel to 6061 aluminum alloy were weld by laser in overlap joint. In order to increase the strength, effect of laser power, velocity, defocus was investigated. The microstructure of the specimen under different parameters were observed using scanning electron microscopy and energy disperse spectroscopy. Tensile test was performed. Results obtained show that the best joints can be acquired at 850 W in laser power and 30 mm/s in welding speed. Increasing the focus amount can increase the penetration depth. The brittle phase always occurred at the interface in the joints of different power. The main component is Fe2Al5 phase, FeAl3 phase and FeAl phase.

In order to improve the accuracy of numerical simulation of CFRTP/stainless steel laser welding process, the thermal contact finite element model is established considering the influence of interface contact thermal conductivity on the welding temperature field.The temperature field was numerically simulated by ANSYS software. The influence of process parameters on weld width and temperature field was studied. The results show that the relative error of the weld width prediction value can be reduced from 17.8% of the traditional model to 6.7% using this model.It is closer to reality and can be used to guide test and industrial production.

The numeral calculations of laser action was carried out by using one-dimensional heat conduction model. Different polishing effect on polycarbonate surface with different values of scanning speed were compared on the condition that the range of the laser power density for polycarbonate polishing was in the order of 104 W/cm2. The results show that the optimal processing parameters are as follows: the defocusing amount is 5 cm, the peak power density is 3.1×104 w/cm2, and the scanning speed is 20 mm/s, and the surface roughness of the PC sample can decrease from 5 μm to 2 μm without deterioration. With the increasing of the times of laser scanning, the surface roughness of the sample further decreased, and reached the minimum value around 10 times. The study is helpful for reducing the roughness of the PC surface.

Aiming at the process problems of poor surface quality of metal laser 3D printing, laser cladding and other laser deposition forming processes, it is difficult to directly install the machine, using a fiber-semiconductor coupled laser to polish the iron-based laser cladding layer. The influence of laser polishing on the surface morphology and physical and mechanical properties of laser deposition forming was studied. Firstly, the macroscopic morphology and roughness of the laser polishing cladding were tested, analyzed and characterized by hand-held microscope and white-light interferometer. Then, the microstructure of the cladding layer was tested and analyzed by scanning electron microscope (SEM). The microhardness value of the cladding layer along the depth direction was tested by X-ray stress tester. The results show that laser polishing cladding macroscopic morphology is smooth and the roughness of the laser cladding layer is significantly reduced. The effects of different polishing times on the surface quality is compared. After the first polishing, the microstructure of the middle of the cladding layer is planar cell crystal, and the microstructure of the middle of the cladding layer is the fine equiaxed crystal after two times polishing. The surface residual stress of the cladding layer is compressive stress after the first polishing, the surface residual stress of the cladding layer is tensile stress after the two times polishing. After two times of polishing, the microhardness is 1.3 times higher than the original cladding and 3.5 times higher than that of the substrate.

A modified finite element simulation method was used to predict the surface residual stress and surface deformation of TC17 Titanium Alloy under multiple Laser Shock Peening(LSP). In order to verify the modified method, a bench-mark simulation was performed verified with available experimental results and the predicted results were well correlated with those from experimental data. With the aid of the modified method, the influences of the number of impacts and laser power density have been analyzed. The simulated results show that surface residual stress and deformation increase with the increase of impact number and gradually reach saturation after 3 impacts, nonuniform distribution increases with the increase of impact number. The surface residual stress and deformation increase with the increase of the laser power density.

In order to study the influence of laser power on laser quenching of 27SiMn steel for hydraulic support post, ANSYS finite element software was used to simulate the process of laser quenching, and the temperature field distribution under different power was obtained. The laser quenching experiment on 27SiMn steel was carried out under the same conditions as the numerical simulation, and the macrostructure, microstructure and microhardness were analyzed. The results show that the depth of quenching zone obtained by numerical simulation and experiment is basically the same. In the numerical simulation, the peak temperature of the workpiece increases with the increase of the laser power, and the cross section of the whole temperature field is semilunar. The morphology of the hardened layer obtained by the experiment is similar to the simulation result and is semilunar. After quenching, fine and dense martensite microstructure is formed on the surface of the matrix, and the hardness of the hardened layer is increased by more than 2.5 times than that of the matrix, and the depth and hardness of the hardened layer gradually increased with the increase of laser power.

A simple and compact high peak power pumped single-stage dual-pass Nd:YVO4bounce slab amplifier is reported. In order to suppress the amplified spontaneous emission (ASE) during high peak power pumping, the upper and lower surfaces of the slab crystal are plated with germanium, and a dual-pass amplifying optical path is designed which grazing incidence total reflection center point does not overlap with the center point of the pumping area. The amplifier is used to amplify seed laser with a repetition rate of 200 Hz, a single pulse energy of 10 μJ and a pulse width of 24 ns. At a maximum pumping energy of 35 mJ, an amplified output laser with a single pulse energy of 2.7 mJ, a pulse width of 24.3 ns and a beam quality factor M2 of about 1.2 is obtained, the energy extraction efficiency is 7.7%.

It is difficult to accurately construct the internal conductive network of the traditional filled conductive polymers. For the first time, the selective laser sintering is applied to fabricate filled conductive polymers. Firstly, porous graphite skeleton is rapidly prepared by selective laser sintering technology, and then the composite of porous graphite matrix and phenolic resin matrix is realized by hot pressing forming process, and a new type of filled conductive polymers is obtained. The influence of the basic characteristic structure parameters of Y-shaped honeycomb porous graphite skeleton on the electrical properties of the new filled conductive polymers is studied. The Z-direction resistivity calculation model of the new filled conductive polymers is presented and verified by the design experiment. The results show that the new process is feasible. By changing the structure parameters of the basic characteristic unit, the number of internal conductive paths and the parallel series mode of the new filled conductive polymers can be changed, and the active regulation of the electrical properties of the new filled conductive polymers is realized. This provides a new method for the preparation of filled conductive polymers.

Photoacoustic tomography is a technology that reconstructs the distribution of light energy in tissue through detecting photoacoustic signals. In recent years, the field of research has been greatly developed and widely used in anatomy, functional science and molecular imaging. However, one of the great challenges is that the efficiency of light to sound conversion is very low due to photoacoustic effect, resulting in a low signal-to-noise ratio (SNR) of photoacoustic signal, and the quality of reconstructed photoacoustic image is not high. Conventional approach to enhance the SNR of photoacoustic signal is the data averaging method, but severely limits the imaging speed. Without sacrificing signal fidelity and imaging speed, firstly, uses empirical mode decomposition (EMD) to realize adaptive decomposition of photoacoustic signals. Then uses conditional mutual information as criterion to determine intrinsic mode function (IMF) which needs noise reduction, and then de-noises the selected intrinsic mode functions to obtain the de-noising photoacoustic signal. Finally, the de-noised photoacoustic image is obtained by using the reconstruction algorithm. The simulation and experimental results show that the proposed method, which combines empirical mode decomposition with conditional mutual information, can achieve better improvement of signal-to-noise ratio of photoacoustic signals and the contrast of reconstructed images than the traditional methods. The effectiveness of the de-noising algorithm is proved. At the same time, this method provides a possibility of development a real-time low-cost PA imaging system with low power laser source and low power amplification signal SNR.

Positioning and orientation system (POS) based on UAV platform is integrated with differential GNSS high-precision positioning technology and INS navigation technology to provide position and attitude reference for aerial remote sensing based on direct geo-reference. It is the key to obtain high-quality remote sensing imaging. Aiming at the low-precision IMU adopted by the light and small UAV, the error model is researched and analyzed, and the 24th-order Kalman filter is established. Finally, the GNSS/INS loose combination mode is used to obtain high-precision POS data. The measured data shows that the POS data obtained under this error model can be combined with the radar data of the UAV to meet the laser point cloud accuracy requirements and effectively reduce the cost of the airborne laser scanning system.

Aiming at the production of idiopathic scoliosis support which has a long processing cycle and needs modulus of mud in patients, and the machining process is very long. Some measures should be taken to solve these problems. The selective sintering 3D printing technology is applied to the manufacturing of idiopathic scoliosis support. After testing, the selective sintering technology can greatly shorten the processing time of the support, reduce the processing steps, and have certain advantages in testing the scaffolds morphology, and improve the efficiency of manufacturing of idiopathic scoliosis support. The patient is scanned mainly by means of a hand-held scanner, and a segmented scoliosis correction support is established based on the scan result. Combining Geomagic and Rhino software, simulation and topology optimization design through ANSYS Workbench, based on the topology optimization results of the model, the remove part is filled with honeycomb holes filling to reduce weight. The model is subjected to engineering stress verification, and the bearing capacity of the support before and after optimization is compared. The test results show that the innovatively proposed segmented scoliosis support can achieve lightweight function under the condition of setting certain constraints and ensuring the correcting function of the support. The topology optimization structure can achieve the weight reduction function, and the weight loss reaches 8.36%. After topological optimization, the load capacity of the front chest plate is 97.61% of the original structure, and the back plate is 96.62%.

The simulation method and test method of high power narrow pulse laser diode driver are introduced. The laser driver principle function is verified with Energy-storage method in multisim. Based on the theories of power integrity and signal integrity, the core device diagram is simulated with IBIS models or SPICE models of these devices. Finally, the test method of peak power and average power of output light pulse is expound. The final test results show that the functional simulation and the back-end simulation coincide with the design parameters of the current and pulse.

Objective: To observe the effect of ultrasound-guided tumescence anesthesia solution on postoperative pain of endovenous laser ablation of lower extremity varicose vein. Methods: 90 cases of patients with lower extremity varicose vein were divided randomly into study group and control group, 45 cases in each group, two groups were treated by endovenous laser ablation, study group was assisted by ultrasound-guided tumescence anesthesia solution, and control group was assisted by traditional epidural anesthesia. Clinical efficacy, nerve block, perioperative heart rate (HR) and mean arterial pressure (MAP), postoperative visual analogue score (VAS) and postoperative recovery of daily activities were compared between the two groups. Results: ①The total effective rate in the study group was 91.11%, higher than that in the control group (86.67%), but there was no statistically significant difference in clinical efficacy between the two groups (P>0.05).②The onset time of nerve block in the study group was shorter than that in the control group (P0.05).③At the beginning of the operation and 15, 30 min after the operation, HR in the two groups was lower than that before the operation (P0.05).④There was no statistically significant difference in VAS score at postoperative anesthesia recovery between the two groups, but VAS scores at 2, 4, 6, and 8 h after surgery in the study group were lower than those in the control group (P<0.05).⑤The recovery rates of daily activities in the study group at 1 d, 2 d and 3d after surgery were all higher than those in the control group (P<0.05). Conclusion: The use of tumescence anesthesia solution in the treatment of lower extremity varicose veins by intracavitary laser can alleviate postoperative pain better than traditional epidural block anesthesia.

Objective: To study the effects of laser photocoagulation combined with calcium dobesilate and Xueshuantong on microcirculation and inflammatory factors in patients with diabetic retinopathy(DR). Methods: 86 patients with DR in our hospital were selected as research objects.According to the number table, the patients were divided randomly into control group and combination group, 43 cases in each group. On the basis of conventional treatment for diabetes mellitus, the control group was treated with laser photocoagulation, the combination group was treated with laser photocoagulation combined with calcium dobesilate and Xueshuantong. Hemangioma, macular, blood spots, visual acuity,visual field gray value, peak flow velocity(PSV), end-diastolic velocity(EDV), resistance index(RI) of central retinal artery and posterior ciliary artery, and fasting plasma glucose (FPG), 2 h postprandial blood glucose(2 h PG), glycosylated hemoglobin(HbA1c), blood calcium, blood plasma viscosity, erythrocyte aggregation index, erythrocyte deformation index, platelet aggregation rate, hypoxic induction factor-1 (HIF-1) and vascular endothelial growth factor (VEGF), interleukin 1β(IL-1β), matrix metalloproteinase 9 (MMP-9) before and after treatment were supervised in the two groups. Clinical efficacy was compared between the two groups. Results: ①The total effective rate 95.35%) of the combination group was significantly higher than that of the control group72.09%)(P＜0.05). ②Compared with those before teeatment, FBG, P2hBG and HbA1c decreased after treatment in the two groups, (P0.05). ③Compared with those before teeatment, Hemangioma, macular, blood spots, visual acuity,visual field gray value, PSV, EDV, RI of central retinal artery and posterior ciliary artery, blood plasma viscosity, erythrocyte aggregation index, erythrocyte deformation index, platelet aggregation rate, HIF-1, VEGF, IL-1β, MMP-9 improved after treatment in the two groups(P<0.05), and the improvements of combination group were significantly better than those of control group(P＜0.05).Conclusion: Compared with laser photocoagulation alone, laser photocoagulation combined with calcium dobesilate and Xueshuantong has better clinical curative effect on DR, It can significantly improve the microcirculation and inflammatory reaction of patients, and has high clinical value.