Lattice structures possess well load-bearing and energy absorption properties, which are widely used in biomedical, vehicle engineering, aerospace, and other relative fields. In this work, a series of uniform and grade lattice structures were fabricated via topology optimization design and Selective Laser Melting (SLM). Also, their surface morphology, compressive deformation behavior, and energy absorption properties were investigated. The results show that the SLM technology has the ability to fabricate micro-struts and can fabricate lattice structures with a minimum relative density of 0.20. The compressive deformation mechanism of the uniform lattice structures is the overall elastic buckling firstly and then achieving densification, while the compressive deformation mechanism of the grade lattice structures is the deformation compaction layer by layer to achieve densification. The energy absorption of the lattice structure is proportional to relative density while have not relationship with the structural type. The energy absorption efficiency is affected by the density distribution of lattice structures, and grade lattice structures have higher energy absorption efficiency than the uniform ones.

Al-TiC and Al-TiC-Y2O3 cladding layers were prepared on the AZ91D alloy by laser cladding technology. The effects of Al∶TiC mass ratio and Y2O3 addition on the microstructure, phase composition, hardness, and corrosion resistance of the cladding layer were studied. The results show that the Al-TiC cladding layer with different Al∶TiC mass ratio and the Al-TiC-Y2O3 composite cladding layer with different Y2O3 addition have achieved good metallurgical bonding with AZ91D alloy matrix; the main phases of Al-TiC cladding layer are Ti3AlC, TiC, Mg2Al3, and Al3Mg2. Al3Y and Al4MgY phases are newly produced in Al-TiC-Y2O3 cladding layer after adding Y2O3. When the mass ratio of Al: TiC is 8∶1, 4∶1, and 2∶1, the hardness of the corresponding Al∶TiC cladding layer is about 2.75, 3.24, and 3.94 times that of AZ91D alloy, while the hardness of Al-TiC-Y2O3 cladding layer is further improved after adding Y2O3. The corrosion resistance of Al∶TiC cladding layer with different Al∶TiC mass ratio is higher than that of AZ91D alloy, and the corrosion resistance of cladding layer is the best when the Al∶TiC mass ratio is 8∶1. On this basis, Al-TiC-Y2O3 composite cladding layer with Y2O3 is 0.6%, which has the highest hardness and the best corrosion resistance.

Laser additive manufacturing is one of the key technologies that promote the rapid development of the manufacturing industry. The extremely high forming freedom makes it play an important role in aerospace and other major equipment fields. With the popularization of the concept of carbon neutralization and carbon peak, the development of green manufacturing technology determines the international competitiveness of the manufacturing industry in the future. Laser additive manufacturing technology, as a typical green manufacturing technology, can greatly improve the utilization rate of materials. In this study, the airworthiness analysis idea for the development of allowable value and design value of additive manufacturing materials is introduced. The development and application status of laser additive technology based on lightweight design are presented. The challenges of laser additive manufacturing technology in the field of civil aviation are analyzed, which provides some ideas for the development of lightweight design technology for laser additive manufacturing technology in the field of civil aviation.

To tackle the problem of complexity and time-consuming in simulating the metal 3D printing process, a modified inherent strain method is adopted to achieve accurate and rapid prediction of residual deformation in 3D printing process while taking the metal selective laser melting (SLM) processing process as the research object. Considering the periodicity of 3D printing process, thermal-elastic-plastic coupling analysis is carried out for two successive printing layers, and then the equivalent modified inherent strain load of 3D printing process is extracted based on the modified inherent strain theory. The extracted modified inherent strain is applied to the elastic finite element model layer by layer to realize efficient simulation of 3D printing process and accurate prediction of its residual deformation. At last, the accuracy and efficiency of the modified inherent strain method in predicting 3D printing residual deformation are verified by comparing the results of the thermo-solid coupling analysis and the 3D printing experiment.

The influence of welding speed on joint formation, microstructure evolution, and mechanical properties of 2 mm thick QP980 high strength steel were studied by using a laser beam with a spot diameter of 0.1 mm. It was found that with the decrease of welding speed, the cross section morphology change from nail shape to hourglass shape, and finally to straight cylinder shape. The weld melting zone is composed of coarse martensite, and the heat affected zone is mainly composed of fine martensite. The hardness is higher than that of the base metal. The hardness of the tempering zone is lower than that of the base metal due to the decomposition of martensite in the original base metal. However, with the increase of welding speed, the decomposition degree of martensite decreases gradually. Due to the hardening of the weld, the elongation after fracture of the welded joint decreases. The tensile fracture morphology at different welding speeds shows that it is ductile fracture.

Objective: The fiber laser was used to weld 304 stainless steel and copper dissimilar materials to improve tensile strength of welds. The welding mechanism was analysed. Methods: The tensile strength of stainless steel/copper welds under different positions of laser beam was tested .The microstructure of the weld was observed by optical microscope, and the elements in the welds were analyzed by energy spectrum analyzer (EDS). Results: The experimental results showed that the maximum tensile strength of welds is 186 MPa when the laser beam is 0.15 mm close to the stainless steel side. Conclusion: The laser beam absorption rate on stainless steel is higher than that copper. The laser beam near the stainless steel side makes the stainless steel melt first, and then the heat conduction affect on copper to form a molten pool, and the stainless steel penetrates into the copper side to form a dissimilar metal welds.

Active thermal protection component is an important structure in the field of aerospace. Fiber laser welding is the preferred manufacturing technique for this kind of structure. Stringent service environment puts forward higher comprehensive requirements for weld forming, surface protection, and porosity defects. Based on the side protective fiber non-penetrate deep penetration laser welding process test, the effects of phosgene spacing, gas transmission angle, protective gas output length and gas flow rate on weld formation, and weld protection and porosity were systematically analyzed by means of ultra-depth of field microscope, digital RT detection, and gray scale processing. The results show that the shielding gas flow rate and distance between the laser and the protective gas have a great influence on the weld morphology and porosity. Under the condition of positive distance between the laser and the protective gas, the weld porosity is low, and the porosity is positively correlated with the shielding gas flow rate. Based on the optimized gas protection parameters, the nozzle structure was optimized, and the 3D component of active thermal protection groove was manufactured by laser welding, which passed the bench test.

In order to study the influence of remelting power on the microstructure and properties of Inconel 718 nickel-based self-lubricating coating, laser cladding technology is adopted to prepare Inconel 718 cladding coating on 27SiMn steel plate, and three different laser power remelting cladding samples are selected. The surface morphology and metallographic structure of the cladding layer are observed by super depth of field microscope, the microhardness of the cladding layer is measured by microhardness tester, and the friction and wear properties of the cladding layer are tested and evaluated by pin-disk friction and wear testing machine. The results show that the grain size of the cladding layer is obviously refined after laser remelting. With the increase of remelting power, the grain size of the cladding layer decreases firstly and then increases. When the remelting power is 1 260 W, the grain size at the top of the cladding layer is the most uniform and fine. After remelting, the hardness of the cladding layer is greatly improved, and the hardness can be increased by 22% compared with that of the specimen without remelting. From the wear morphology, the wear mechanism of the sample is mainly abrasive wear, and the friction coefficient and wear weight loss of the sample are obviously reduced after remelting. The analysis of friction and wear test data shows that the specimen has the best wear resistance when the remelting power is 1 260 W.

The UV nanosecond marking system is used to experimentally study the direct marking of DM code on silicon wafer surface. The control variable method is used to study the influence of different pulse duty cycle, repetition frequency, and spot overlap ratios on the thermal damage, surface topography, and DM code reading effect of the marking materials. The results show that the pulse duty cycle and repetition frequency have obvious effects on the ring width and heat affected zone of the marking area, and the reading rate and reading time of DM code are affected by duty cycle, repetition frequency, and spot overlap rate at the same time. The single-pulse energy in the range of 10.7 μJ~20 μJ can mark uniform, delicate, stable, and high-readability dust-free marks that meet the SEMI standard.

In this paper, on the basis of the tunable electromagnetically induced transparent (EIT), a temperature sensing system composed of plasmonic side-coupled resonant cavity is proposed. Utilizing the finite difference Time domain (FDTD) method, we investigated that the central wavelength of the transmission window can be precisely regulated by changing the amount of liquid injected into the cavity. The temperature sensing performance of this system was investigated in conjunction with the sensitivity of surface plasmon polaritons (SPPs) to the dielectric properties of the surrounding environment. It is achieved that the resonance wavelengths for injected chloroform and alcohol are both linear with the change of ambient temperature, and the best temperature sensitivity corresponding to chloroform can reach 0.425 nm/℃, which is higher than that of alcohol. The results may provide theoretical guidance for the development of highly integrated optical switching, sensing, and slow light devices.

In order to improve the counting accuracy of laser particle counter, a signal preprocessing method based on matched filter is designed. The characteristics of the particle signal are analyzed, and the typical waveform of the particle is obtained by the method of normalization and accumulation. Using the typical signal as a matching template, the original signal of laser particle counter and the matching template are discretely convolved to obtain an output signal with a high signal-to-noise ratio. The experimental results show that the signal-to-noise improvement ratio is better than 1.6 for particle signals with original amplitude of 55~262 mV and root mean square value of noise of about 6.74 mV. This method effectively improves the signal-to-noise ratio of the output signal, and provides a good foundation for the accurate detection and recognition of particles.

In order to detect defects on the surface of soft pack batteries, a system based on line structured light is developed for the inspection of the surface of soft pack batteries. Firstly, a laser triangulation-based inspection system is built; the camera, light plane and moving position are calibrated to obtain the surface streak image of the battery through the camera and line structured light; the centerline of the streak is extracted by applying the Steger method. Then the morphological characteristics of the battery surface are restored through 3D reconstruction, and the type of defect is judged by combining with the surface streak characteristic curve. The experimental results show that the system can detect the type of defects and the degree of damage on the surface of soft pack batteries, and meet the needs of soft pack battery surface inspection.

In order to improve the accuracy of depth measurement of UAV in outdoor scene, a laser sensor based vision depth estimation method for binocular UAV in outdoor scene is proposed. The echo signal equation is used to decompose the echo pulse signal of the UAV, and the problem of superposition echo when the laser sensor receives the echo signal is solved. Based on the principle of laser imaging in laser sensor, the echo signal of UAV is detected and imaged, which solves the problem that it is difficult to extract small target because of the coverage of adjacent target. Inverse convolution neural network is used to reconstruct the image network, and the scope of Skip is reset for seamless stitching of the extracted image features. Experimental results show that the proposed method can estimate the depth of outdoor scene with the ratio of parallax pixels above 50%, and the depth estimation is better than the contrast method.