In this study, SiCp/AlSi30 matrix composites were produced by ultrasonic vibration combined with laser metal deposition process. The effect of SiC mass fraction on the constitutional phases, microstructure and mechanical properties of aluminum matrix composites was investigated. When the mass fraction of SiC is less than 10%, the interaction between the liquid aluminum alloy and SiC particles is limited, and the ceramic particles maintain their original shapes. When the mass fraction of SiC reaches 15%, some SiC particles will react with molten Al alloy to form long needle-like Al4SiC4. The addition of SiC reinforcements promotes non-uniform nucleation of Si phase, resulting in a refinement of the primary Si size. Due to the combined effect of high hardness reinforcements and grain refinement, the elevated mechanical properties were obtained for 10% SiCp/AlSi30 composites. The microhardness showed 25.3% improvement upon unreinforced AlSi30. Furthermore, 10% SiCp/AlSi30 composites also reduced the coefficient of friction (COF) by 19% and the wear rate by 25% compared to the AlSi30 alloy fabricated by ultrasonic-assisted laser metal deposition.

Laser cladding is an advanced surface modification technology, which has the characteristics of small effect on the heat affected zone of the matrix, fine microstructure and small deformation degree of the matrix, and it has been widely used in the field of remanufacturing. Rare earth elements can improve the microstructure of nickel-based alloy coating and make the coating grain fine and purify grain boundary. The research progress of rare earth oxides in laser cladding nickel-based alloy coatings is summarized in this paper. The types and properties of rare earth oxides were summarized, and the effects of rare earth oxides on the grain size, dilution rate and crack of nickel base alloy coating were studied by combining the mechanism of rare earth oxides. The hardness, wear resistance, corrosion resistance and oxidation resistance of the coating were analyzed, and the effects of rare earth oxides on hard phase of the coating were also discussed. Finally, the existing problems and future development direction of rare earth oxide coating on laser cladding nickel-based alloy are prospected.

Aluminum alloy has the characteristics of low density, high specific strength and good corrosion resistance, which can well meet the lightweight needs of aerospace vehicles, and the aluminum alloy parts manufactured by selective laser melting (SLM) technology have good comprehensive properties and have been widely used in the aerospace field. However, there are some problems in the forming process, such as poor defect control, poor surface quality, cumbersome post-treatment process and so on. This paper selects AlSi10Mg aluminum alloy fabricated by SLM to conduct a solid process optimization study for defect elimination, in order to obtain the optimized process parameters with the least defects and further study the surface roughness optimization method. Results show that lower porosity (9.2%) and better internal forming quality can be obtained by optimizing the process parameters (mainly including scanning power, scanning speed, scanning spacing). The main influencing factors of the surface quality of the formed parts are scanning power, scanning speed, scanning spacing, etc. It is found that appropriately increasing the scanning power can obtain better surface quality.

The size of the overlap rate affects the surface flatness of the multi-overlap laser cladding layer. In order to study the effect of overlap rate on the surface flatness of laser cladding on inclined substrates and obtain the critical overlap rate for flat surfaces, an elliptical model was used to fit the cross-section of the tilted substrate cladding layer, which was verified by experiments. The overlap model of the inclined substrate was established, and the calculation method of the critical lap rate to obtain the best flatness on the inclined substrate was derived. The effect of different overlap rates on the flatness of the clad layer is investigated at a substrate inclination of 30°. Results show that a smaller overlap rate leads to a decrease in the flatness of the clad layer and a larger overlap rate leads to an increase in the height of the clad layer due to the continuous accumulation of the clad layer, and that a flat clad layer can be obtained with almost no change in the height of the clad layer at the critical overlap rate.

In order to improve the low efficiency and high labor cost of FGM surfacing, this paper adopts plasma surfacing technology and uses H13 steel powder as welding material to conduct surfacing test on hot work die steel base metal (5CrNiMo). The influence of welding current on weld depth, weld width, microstructure and crack sensitivity of surfacing layer was studied, and the forming mechanism of welding crack was discussed. Results show that the weld depth and weld width increase with the increase of welding current. The microstructure of the surfacing layer is composed of martensite, residual austenite and carbide. With the increase of welding current, the martensite dendrites in the middle of the surfacing layer become coarser gradually. During multilayer welding, the austenite content in the upper part of interlayer interface is obviously higher than that in the lower part. When the welding current changes, the crack sensitivity of H13 surfacing layer is large. When the welding current is 150A, the surfacing sample with fewer cracks can be obtained. The cracks in surfacing layer can be divided into stress induced cracks and defect induced cracks according to their forming mechanism. By means of plasma surfacing, fast surfacing of hot working die is realized, which provides guidance for plasma surfacing of filling hot working die.

In order to realize the accurate recognition of weld target by welding robot under complex working conditions, laser vision sensing technology is applied to robot weld recognition. Taking the laser vision sensor as the core hardware, we build the welding image acquisition system, use the PCI bus card to detect whether the sensor and external indicator are connected, obtain the laser welding image within the specified time through the PXR800 image acquisition card, and use the serial port communication program to complete the efficient image transmission. The bilateral filter and fuzzy operator are used to denoise and enhance the image, optimize the image corner and the center of the laser stripe, and use the equality constraint equation to modify the image coordinate value after Kalman filter to complete the task of high-precision weld recognition. Simulation results show that laser vision sensing can help the robot improve the accuracy of weld recognition and enhance the anti-interference ability, which plays a positive role in the popularization and application of welding robot.

Nickel-zinc ferrite composite material as an excellent absorbing material with high flexibility and machinability, is widely used in shielding electromagnetic interference in communication. To improve the cutting quality of ferrite composite sheets, laser cutting process with sub-nanosecond pulsed laser was selected in this work. The scanning strategy of laser cutting was improved firstly. Compared with the conventional multi-pass strategy, the improved multi-pass strategy with periodic scanning-cooling suppressed the heat accumulation significantly. The width of the HAZ (heat affected zone) of kerf reduces from 567.39 μm to 249.42 μm, a decrease of 56%. Response surface model was used to analyze the comprehensive effects of average laser power (P), beam scanning speed (v), and the number of scans in each cycle of scanning-cooling (n1) on the width of HAZ and cutting efficiency. The parameters were analyzed for proper process window. High average power, high scan speed, and few scan times are beneficial to reduce the width of HAZ while taking into account the cutting efficiency. Results of parameter optimization showed that the improved processing could cut off 0.2 mm nickel-zinc ferrite composite sheet in 9 cycles with the average power is 19.7-21.1 W, the scanning speed is 1 750-1 800 mm/s, the number of scans in each cycle is 20-24, and the width of the HAZ is about 200 μm.

Xinjiang, as the key node of "power transmission from West to East" in China, has a large power grid coverage area. Affected by the bad weather in Xinjiang, the electric power fittings subject to conventional treatment failure prematurely during service. In order to further improve the service life of fittings, laser hardening is used to improve the surface wear resistance of the material, and the effect of laser hardening treatment on the microstructure and hardness of the U-ring is studied. According to the actual working conditions of U-rings, the wear test is carried out and the wear results are analyzed. Finally, the residual loading capacity of the worn U-ring is tested. The results show that the microstructure of laser hardened layer is needle-like and lath martensite, the average hardness of the hardened layer is 638 HV, and the depth is about 2.1 mm. The average wear mass of the unstrengthened U-ring in group one is 19.8 g, and the average wear mass of the laser-strengthened U-ring in group three is 0.9 g, the mass loss of laser-strengthened U-ring is 4.5% of the unstrengthened U-ring. According to the failure load test, the residual loading capacity of laser hardening U-ring is still higher than its nominal failure load.

Based on ablation threshold theory, the ablation characteristics of face gear with femtosecond laser are studied and the ablation threshold of face gear is obtained. The theoretical width and depth of femtosecond laser ablation in monopulse and multi-pulse ablation are calculated and simulated. The dynamic recoil pressure mechanism diagram of plasma shock wave is obtained by coupling the change of residual temperature of plasma surface with the change of propagation radius of plasma shock wave with the change of time. The influence of dynamic recoil pressure of plasma shock wave on the morphology of ablated pits, scanning tunnels and ablated planes during femtosecond laser processing are obtained. Experimental results show that the straightness of tunnel decreases with the increase of scanning speed when femtosecond laser scanning the opposite gear. Under the condition of high power, the accuracy of the ablated tooth surface is higher by increasing the spacing between adjacent scanning tracks. These results provide a reference for the influence of plasma dynamic recoil pressure on the surface accuracy of femtosecond laser machining of face gears under different parameters.

Vibration and ablation are two main mechanisms of pulsed laser cleaning insulator surface pollution, but the actual mechanism will be different under different laser parameters. A thermo-stress coupled finite element model was established by COMSOL to simulate temperature and stress fields, and the vibration and ablation mechanism and cleaning effect of pulse laser scanning with different pulse power during one cycle were explored. The feasibility of simulation results was verified by laser cleaning experiment. The simulation results show that the pollution removal threshold of vibration and ablation mechanism is about 123 W, and both vibration and ablation increase with the increase of pulse power. At 150 W, the cleaning depth is 40% of the pollution thickness, and at 200 W, it reaches 92% of the pollution thickness. At 250 W, the cleaning mechanism reaches the critical state and the cleaning depth reaches the cleaning thickness. Above 250 W, the ablative mechanism dominates. Taking 300 W as an example, the insulator has obvious damage. Experimental results show that when the power of the equipment is 200 W, the pulsed laser can remove the pollution on the insulator surface obviously, and the pollution on the insulator surface bounces under the force and has obvious gasification phenomenon. Only a small amount of pollution remained in the insulator base, and no damage was observed.

A finite element model of micro-scale laser shock peening (μLSP) was established utilizing ABAQUS.Process of μLSP of T2 pure copper was numerically simulated. The dynamic response of displacement, plastic strain, and equivalent stress as well as the distribution rule of residual stress during μLSP were analyzed. The results show that the dynamic yield limit of copper can be reached in a very short time after the shock wave acting at the surface. The diameter of the displacement-affected region at the surface of copper is about twice the laser spot diameter, and the maximum displacement of around 0.85 μm is achieved at 27 ns. With the increase of shock wave pressure, work hardening occurs in copper, and the maximum plastic strain and equivalent stress of about 0.062 and 297 MPa appear at the near-surface of the loaded region. The laser irradiated region of copper mainly shows residual compressive stress after μLSP which is about 199 MPa and has an influence depth of 40 μm. Residual tensile stress exists at the edge of laser irradiated region, indicating the appearance of “residual stress hole”. Meanwhile, the experimental results of μLSP are basically consistent with the numerical simulation results, which verify the reasonability and reliability of the finite element model.

As one of the core components of hydraulic system, the surface size of oil distribution plate is directly related to the performance of the hydraulic system. Aiming at the problems of difficulty in extracting partial surface contour features and large measurement error, this paper proposes a spherical segmentation and size measurement method based on additional image edge detection. Firstly, the Sobel operator is adopted to sharpen the edge of the oil distribution plate image, and the contour of the spherical part is extracted to form the mask. Then, the four-step phase shift diagram of the spherical part is segmented by mask, the four-step phase shift method is adopted to solve the phase principal value, and the dual-frequency heterodyne method is adopted to unfold the phase. Finally, the three-dimensional point cloud data of the spherical part of the oil distribution plate is calculated and spherical fitting is carried out through the system calibration. Experimental results show that the spherical partial point cloud image can be segmented clearly by using this method. The measurement accuracy based on point cloud data fitting is 99.238%, which is higher than the measurement accuracy based on height segmentation, RANSAC (Random Sample Consensus) segmentation, region growing segmentation and manual box selection method, and the high-precision measurement of spherical size of oil distribution plate is realized.

Laser remote sensing detection technology has the advantages of fast information transmission, convenient operation, high precision and long-distance detection, and it can make up for the shortcomings of seismic exploration in complex terrain areas, such as difficult construction and slow seismic data acquisition. Utilization the characteristics of high sensitivity, high detection efficiency and off-axis detection of wavefront sensor, which used in seismic wave laser remote sensing detection to refinement the signal processing complexity caused by slow change of Michelson interference method in previous studies. By setting up the laser remote sensing detection system, the longitudinal waves in seismic waves are observed and analyzed, and the relationship between ground amplitude and wavefront sensor measurement spot is discussed. Experiments show that the system has better response to low frequency seismic waves, which solves the interference of natural frequency of the instrument itself. The characteristics of off-axis detection make the acquisition of reflection signals more convenient, which provides experimental reference for seismic wave laser remote sensing detection.

The root mean square of mid-spatial-frequency wavefront (PSD1) is a key parameter used to evaluate the quality of mid-spatial-frequency wavefront of optical components. Before numerical calculation, the wavefront data should be filtered in frequency domain. Because the filtered data is easy to lead to data truncation in and outside the region to be measured, large edge high-frequency error and Gibbs noise are introduced, which seriously affects the accuracy of calculation. In order to reduce the impact of truncation, this paper optimally fills the truncated data to reduce the spatial frequency mutation inside and outside the truncated region. A four-way extended average algorithm is proposed by comparing the existing spatial preprocessing methods. Experimental results show that the proposed method can well restore the mid-frequency segment surface shape of optical elements and significantly improve the PSD1 measurement accuracy, and the mean error of the proposed method is less than 5% compared with the standard value.

The ocean is a treasure trove of rich resources, which is particularly important for the development and utilization of marine resources. Technologies such as water and air cross-medium detection, communication, and underwater target determination have always been the focus of attention of relevant workers with any difficulty. As a kind of mechanical wave, sound is a good propagation carrier in water. Therefore, it is an appropriate method to achieve detection and communication across the water-air interface by extracting underwater acoustic wave information. However, there is still a lack of complete underwater acoustic signal propagation models and experiments. In this case, this paper proposes a simulation model of water surface ripple vibration generated by underwater acoustic signal based on finite element method, which detects water surface ripple with laser Doppler vibration measurement technology. Accurate underwater acoustic information can be obtained by both experiments and simulations. With the conditions of the same underwater acoustic signal parameters, the amplitude of the water surface ripples obtained by the experiment and the simulation is the same, which verifies the feasibility of laser Doppler vibration measurement technology to obtain underwater acoustic wave information and the correctness of the established simulation model. It provides an experimental basis and theoretical basis for realizing breakthroughs in water-space cross-medium detection and communication.

To improve the on-line monitoring ability for lithium battery temperature, a distributed Raman fiber temperature measurement system was set up by dual-channel demodulation scheme, which adopted an external trigger mode to realize the coordinated working state. Results show that the temperature accuracy of each direction reaches ±1 ℃ within the distance of 10 m at normal temperature. After 8 tests, the temperature errors are all within 0.17 ℃, indicating that the system can maintain good stability at room temperature and meet the design conditions. The system can meet the requirements of temperature measurement for lithium battery, accurately feedback the abnormal local temperature, and effectively prevent various accidents cause by lithium battery. Within 10 m sensing distance, the maximum error is only 2 m, which meets the temperature measurement requirements of lithium batteries. Simulation test results show that the system can identify and locate faults accurately, which proves that the system has excellent distributed testing performance. The DTS system can achieve a resolution of ±1 m that can quickly respond to the temperature change caused by lithium battery failure.

In view of the problems of slow manual detection speed and poor precision in the detection of the dimensions of irregular workpieces, an automatic measurement method of inner concave polygon based on point cloud data density extraction is proposed. First of all, the two-eye structure light scanning method is used to obtain the original data of the point cloud on the surface of the part. Secondly, using KD-tree to establish point cloud topology relationships and to perform radius filtering. Thirdly, using greedy algorithm to rebuilt mesh surface. Finally, the base plane bias and density extraction are used to realize the edge feature point and noise classification of the point cloud, and the dimension characteristics of the inner concave polygon aperture are extracted and the size is calculated. The algorithm is verified by the curved automobile dashboard with the characteristics of the inner concave hexagon. The experimental results show that the algorithm can extract features with limited degree and the accuracy of internal feature size measurement is 60 μm. Compared to traditional measurement methods, a single inner concave hexagonal measurement time can be reduced to 1 s, enabling automated and fast dimensional measurement of irregular workpieces.

Aiming at generation of kerfs with groove and uplift profiles during laser scribing (LS) with nanosecond on Al5083, the relationships between two kinds of profiles and corresponding acoustic signals were investigated in this paper. A laser scribing experiment on Al5083 plate with nanosecond and ultraviolet laser was carried out, and microstructures of profiles was observed to explore the formation mechanism of kerfs with two different kinds of profiles, and acoustic emission (AE) signals were collected to analyze the differences. Wavelet Packet transformation (WPT) and support vector machine (SVM) analysis were performed to classify. The observation results illustrated the forming mechanism of uplift profile including the blocking of splash of molten metal and the generation of pores during solidification. AE signals analysis showed the variance and envelope area of WPT coefficients corresponding uplifts were significantly higher than those of grooves. Using WPT spectrum as feature vector after adding tags, SVM with Gaussian kernel was employed to classify. The accuracy reaching 92.57%, which verified the feasibility of WPT and SVM in the monitor of kerf profile during LS based on AE. This experiment provides a technical path for constructing LS monitor system based on AE.

Fingerprint plays an important role in forensic science, but latent print age estimation has been a difficult challenge. This paper proposes a model that is based on the fluorescence intensity of the amino acid solution reacted with 1,2-indanedione and other characteristics as well as the decision tree algorithm. First, a certain gradient concentration of 8 pure amino acid solutions is prepared, and fingerprints of 10 donators are collected to obtain samples with the age of 0, 3, 7, 14, 21, 30 days. The decision tree model is constructed based on the characteristic values of the sample which is reacted with 1,2-indanedione after being irradiated with a green laser and the fluorescence intensity observed with an orange filter, but the effect is not good. After excluding data less than 14 days age, the model is built again, the ACC Score reached 81%, and the ACC scores of the horizontal comparison with SVM (support vector machine) MLP (multilayer perception) model are 55% and 31%, respectively. The decision tree model is the optimal model. The model is tested with real fingerprint data greater than or equal to 14 days as the test set, and the ACC Score is 67%, which provides an idea for the judgment of latent print age.

Among the laser powered unmanned aerial vehicles (UAVs), the method of laser tracking and aiming at the photovoltaic panels of the UAV has become one of the hotspots. In this paper, a particle filter algorithm based on improved butterfly optimization is proposed to solve the problem of large tracking deviation of laser tracking and aiming UAV. Firstly, an adversarial learning strategy is introduced in the initialization stage of the butterfly optimization algorithm, which improves the algorithm optimization performance. Secondly, the position update formula of the butterfly optimization algorithm is optimized to improve the algorithm optimization speed. Finally, the particle filter algorithm introduced by the butterfly optimization algorithm is applied to the tracking and aiming of the laser powered UAV to realize the optimal tracking of the UAV photovoltaic panel by the laser. MATLAB results show that the particle filter algorithm based on the improved butterfly optimization can improve the accuracy of the laser emitted by the laser during the laser tracking and aiming process, effectively reduce the tracking and aiming error, and improve the effect of laser tracking and aiming at the photovoltaic panel of the UAV.

Objective: Evaluating the efficacy and safety of intense pulsed light (IPL) and red light combined with tacrolimus ointment in the treatment of facial seborrheic dermatitis (SD). Methods: 201 patients with facial SD were randomly divided into experimental group A, B, C and control group. Control group was treated with tacrolimus ointment, experimental group C, B, and A were treated with red light, IPL, red light and IPL on the basis of the former. The course of treatment was 8 weeks. The therapeutic effect and the adverse reactions were evaluated after the treatment. Rseults: The symptoms and signs were significantly improved after treatment with IPL and red light (P＜0.05). Experimental group B inhibited seborrhea and experimental group A improved the skin lesion area and pruritus more obviously. There was no significant difference in the improvement degree of erythema (P>0.05).There was statistically significant difference in effective rate among the four groups (P<0.05).After combined treatment, cuticle moisture content, transepidermal water loss and quality of life were improved, and patient satisfaction was higher. There were no serious adverse reactions in the four groups. Conclusion: IPL and red light combined with tacrolimus ointment are safe and effective in the treatment of facial SD.