Selective laser melting (SLM) technology has great advantages in processing hollow thin-walled structures. Hollow thin-walled structures with equal stiffness are calculated and designed by stiffness theory, and the correctness of the design is verified by the combination of experiment and numerical simulation. The results show that under bending load, the deformation area is mainly concentrated near the center line of the maximum bending moment. Under the same force, the displacement of the three kinds of hollow rectangular section thin-walled structural parts is almost the same. For single thin-walled structural parts, because the elastic modulus is lower than that of solid block parts, the displacement produced by its center is smaller than that of hollow rectangular section thin-walled structural parts. The bending process of the finite element model of thin-walled structure is simulated, and the simulated results of equivalent stress and strain are consistent with the experimental results. The research conclusion can provide theoretical support for the section design of thin-walled structures processed by SLM.

In order to study the effect of laser power on the microstructure and properties of tin-based Babbitt cladding layers, 800 W, 1 000 W and 1 200 W laser powers were used to prepare tin-based babbitt cladding layers on the surface of 20 steel. Phase constituents, microstructure, microhardness, and wear property of the Babbitt coatings with different laser power were investigated using XRD, SEM, microhardness tester, and friction-wear tester, respectively. The results showed that with the increase of laser power, the temperature of the molten pool increases, the cooling rate decreases, and the particle size of the SnSb hard spot particles increases gradually with the increase of laser power. The size of SnSb phase is smaller when the laser power is low, and the distribution is uniform. With the increase of laser power, the size and number of SnSb phase increases, and the hardness and wear resistance of the cladding layer also decrease. The average microhardness of the Babbitt alloy coatings of 800 W laser power is about 35.7 HV, the average friction coefficient is 0.257, and the wear mechanism are abrasive wear and surface fatigue wear.

In view of the problem that cladding defects are easy to occur when laser cladding is used to repair the tooth surface of small modulus gear, which affects the quality of repair, the equipment and process of laser machining of small modulus gear are summarized and analyzed by using the conflict resolution principle of TRIZ theory. The corresponding innovative process method and optimization route are then obtained. Through the evaluation model, the best innovation principle is selected, and the solution of physical contradiction is finally adopted to effectively distribute the beam energy, and the original single beam is changed to multiple beams. The beam with different energy density is applied to different parts to effectively improve the characteristics of Gaussian light source. Experimental verification to get through a single variable method, under the double channel diameter 1 mm spot of laser cladding coating microtek austenitic precipitation less, granular cementite precipitate is more, the coating hardness and wear resistance is higher than single channel laser cladding, the tooth surface has higher resistance to agglutination, pitting and wear resistance, strength of gear tooth surface after repairing process requirements.

Laser directed energy deposition provides a flexible, fast, and agile processing for high-entropy alloys. Reasonable single-pass process parameters are the key to ensure processing. In order to study the influence of process parameters on the deposition morphology of FeCoCrNi high-entropy alloy in the laser directed energy deposition process, response surface methodology was used. The influence of laser power, powder feeding rate, and scanning rate on the dilution rate and aspect ratio was studied. Prediction models of dilution ratio and aspect ratio were established. The results show that the dilution rate and aspect ratio are negatively correlated with powder feeding rate, and positively correlated with laser power and scanning rate. The experimental results indicate that the prediction errors of dilution ratio and aspect ratio are 2.29% and 4.45% respectively, and the established models are in good agreement with experiments.

5A06 aluminum alloy bottom-locking joint with a thickness of 3 mm was welded by beam one-dimensional weaving laser. The influence of beam weaving width, beam weaving frequency, welding speed, and beam defocusing distance on porosity rate of the weld were analyzed. The results show that as the beam weaving width and beam defocusing distance increase, the porosity rate decreases significantly. As the beam weaving frequency increases, the porosity rate firstly decreases and then increases. The best beam weaving frequency range is from 150 Hz to 250 Hz. As the welding speed increases, the porosity rate firstly increases and then decreases. The porosity rate and depth-to-width ratio of the weld are generally exponential growth relationships. The porosity rate can be controlled within 5% when the depth-to-width ratio of the weld is less than 1.5. On the basis of porosity analysis, the optimization process specification was obtained. By using this specification, the product sample was welded, and the porosity rate of the weld meet the Class I requirements of the relevant standard.

This paper clarifies the effect of laser wire filler welding process parameters of dissimilar steel on weld formation. Using 2 mm 45 steel of unequal thickness and 6 mm 316L stainless steel as the test materials, the laser wire filling welding method was used for welding, and the welding seam formation and the mechanical properties of the welded joint were studied with different butt gaps. The results show that with the increase of the butt gap, the residual height gradually decreases, and the weld morphology transitions from nail-shaped to H-shaped. As the butt gap increases, defects are formed in the weld. The hardness of the weld center decreases with the increase of the butt gap, and the highest hardness of the welded joint is located in the heat-affected zone of 45 steel. The tensile strength of the welded joint firstly increases and then decreases with the increase of the butt gap. When the butt gap is 0.6 mm, the surface morphology is good and the tensile strength is the highest, and the fracture position of the welding test is on the 2mm45 steel side.

An important prerequisite for surface tension self-assembly is to limit droplets to the target area using wettability contrast structure. In this paper, a method for fabricating wettability contrast structure on composite substrate surface using microsecond pulsed laser is presented. This method can control the percentage of superhydrophobic coating removal area on the surface of composite substrate by changing the laser processing parameters, and then regulate the wettability of the processing area. The mathematical model and simulation model of removal area proportion are established, and the influence of processing parameters on removal area proportion and wettability is studied. The results show that the removal area proportion of processing area is inversely proportional to processing speed and scanning line spacing. Different wettability zoning structures are prepared with different processing parameters and their contact angles are measured. The experimental results show that with the increase of machining speed from 100 mm/s to 9 000 mm/s, the distance between scan lines increases from 20 μm to 150 μm, the percentage of removal area in the processing area decreases, and the contact angle gradually increases from below 5 degrees to 127 degrees. As the absolute distance between the substrate surface and the laser focal plane increases from 0 to 3 mm, the contact angle of the machined area increases from below 5 degrees to over 170 degrees. The results of self-assembly experiments on microchips show that the wettability contrast structure prepared by this method can realize droplet limitation and microchips self-assembly. The research results in this paper provide a new idea for manufacturing self-assembly substrate with controllable wettability.

Laser texturing has many advantages in the current micro-texturing, but most of the researches are about the formation of micro-concave. In this paper, nanosecond fiber laser was used to create micro-concave/convex texture on the surface of 304 stainless steel. The effect of laser processing parameters on the surface morphology of micro-concave/convex texture was studied. The results show that with the increase of power, the central bulge height of the micro-texture firstly increases, then decreases and finally turns into a pit. At laser power of 25 W, the height increases firstly and then decreases with the pulse width increases, while at laser power of 30 W and 35 W, the height decreases firstly and then increases and then decreases. At laser power of 20 W, with the increase of pulse width, the pulse width firstly decreases, then increases, then decreases, and the variation range is small. At laser power of 40 W, the bulge disappear. The diameter of texture increases with the increase of laser power and pulse width. With the increase of the number of pulses, the concave depth at the central bulge of the micro-convex texture also increases, the height of micro-convex texture decreases. When the number of pulses is 1, the laser power is 25 W and the pulse width is 10 000 ns, the micro-protrusion texture with the height of 35.362 μm, and the diameter of 174.057 μm can be obtained.

To realize the laser marking of Si wafers with clear identification and high cleanliness, this paper focuses on developing a laser marking process that is clear, splash free, debris free, and deep enough to meet the requirements of the subsequent processing process of semiconductor wafers. A 532 nm laser is used to study the influence of laser process parameters such as average power, pulse repetition frequency, and scan speed on laser marking of the Si wafer. The clarity, the depth, the height of the bump, and the heat affected zone of laser markings are evaluated by visual inspection, microscope, and white light interference three-dimensional profilometer. The research shows that compared with the low pulse frequency level below 50 kHz, the influence of average power and scan speed on the laser marking are lower. In the process window with average power 20%, pulse repetition frequency 60~80 kHz, and scan speed of 2 500~3 500 mm·s-1, parameter combination can be optimized to realize clear identification, no splash, and debris pollution laser marking on the silicon wafer, and the laser marking dots depth is 0.5~5 μm and the bump is less than 1 μm.

Laser shock forming is an effective method for preparation of micro and nano structures on foils by using laser shock wave and the confining effect of die, which has attracted extensive attention in recent 20 years. In most reports on laser shock forming process, there are two issues. The first issue is that the laser spot spans several microstructure features, which causes difference in shock wave over different features. The other issue is that the laser repetition rate used is less than 1000 Hz, which limits the speed of laser shock forming. In this paper, a laser with repetition rate of 40 kHz and spot diameter of 50 μm were employed to form a groove with width of 200 μm and length of 6 mm on an aluminum foil. The fluctuation of the height and crosssection shape of the formed microstructure in the laser scanning range were analyzed. The results showed that the height of the formed microstructure is relatively stable in the whole laser scanning range.There is certain transition in the height of the formed microstructure at the beginning and end of the microstructure, and the transition length of the end stage is much longer than that of the beginning stage. The formed microstructure crosssection can be fitted by circular arc.

For TA15 titanium alloy material, a three-dimensional thermal-mechanical coupling finite element simulation model of laser forming was established. The material temperature field and deformation field under different processing parameters were obtained. By building a bending testing system, the temperature and deformation field of the titanium alloy under different processing parameters were obtained, and compared with the simulation results. The validity of the numerical model was verified. Based on the distribution of temperature and plastic strain in the thickness direction of the sheet, the dominant mechanism in laser forming was clarified. The edge effect in laser forming was studied, and a back-and-forth scanning processing method that can be used to suppress the edge effect was proposed.

In this paper, according to the requirements of SEMI standard for 12-inch wafer marking, the 1066 nm fiber laser wafer marking system was used to study the laser marking process of the bare silicon wafer and the coated wafer. The power percentage of the laser was changed by the control variable method. Dot-style SEMI fonts were marked on the wafers, and the quality and readability of the marks were evaluated. The study found that the laser power range corresponding to the bare silicon wafer mark from scratch to severe sputtering is 11.77~19.25 W, and the power range corresponding to the coated silicon wafer is 4.40~11.77 W. The Dot morphology is more in line with the SEMI standard requirements. The melting threshold of the coated wafer become smaller, but the processing window become narrower, the roundness of the marking characters and barcode Dot are poor, and the spatter is not easy to control. The OCR reading rates of the two wafers are basically same.

In order to prevent the damage of insulator base during laser cleaning, the damage test of ceramic insulator under laser irradiation was carried out in this paper. A 1 064 nm pulsed laser was irradiated on the surface of a porcelain insulator to explore the damage rule of the porcelain insulator under different energy density, pulse number and irradiation time. A scanning test was carried out on the surface of the porcelain insulator, and the laser damage threshold of the porcelain insulator was determined by image method. The experimental results show that with the increase of laser energy density, pulse number, and irradiation time, the diameter of insulator surface pit gradually increases and finally tends to a constant value, which is about 1.3 times of the diameter of focused spot. When the scanning speed decreases, the damage morphology changes from speckle to stripe, and the roughness increases with the increase of energy density and the decrease of velocity. Based on the damage criterion of porcelain insulator with image method, the damage energy density threshold was obtained.

Magnesium alloy has many excellent properties such as low density, high specific strength and specific stiffness, good mechanical processing performance, and good biocompatibility. Magnesium alloy has become a potential new generation of biodegradable bone plate materials, but its poor corrosion resistance limits its development. In this paper, the effect of laser shock peening (LSP) on the corrosion resistance of AZ31B magnesium alloy was studied by using different laser power densities of 1.35 GW/cm2, 2.99 GW/cm2, 3.92 GW/cm2, the polarization curves were obtained by electrochemical measurement technique of dynamic potential scanning in 3.5% (mass fraction) NaCl solution for comparison of corrosion resistance before and after laser shock. The influence mechanism of laser shock peening on the corrosion resistance of AZ31B magnesium alloy was studied by microstructure. The surface hardness of the sample increases with the increase of laser power density. The surface hardness of the 2.99 GW/cm2 sample is 81.2 HV, which is 35.8% higher than that of the original sample. XRD patterns show that compared with the original sample, the diffraction peak of the sample after laser shock treatment shifts to the high angle direction, the intensity of the diffraction peak decreases, and the FWHM increases. The 2.99 GW/cm2 sample has the best corrosion resistance, corrosion potential is-0.602 41 V, corrosion current density is 1.021 5 × 10-4 A / cm2, corrosion potential increased by 50.47% compared with the original sample, and corrosion current density decreased by 42.90%.

A gas concentration measurement system based on wavelength modulation spectroscopy (WMS) technology is the main tool for ammonia escape monitoring in coal-fired power plants. In this paper, we designed a numerical simulation experiment to optimize the modulation parameters of NH3 molecular absorption spectroscopy, and it was found that the optimal modulation depth of WMS measurement system is 0.238 8 cm-1 under the condition of 200 ℃. In the temperature range of -20~500 ℃, the optimal modulation depth decreases nearly linearly with the increase of temperature, and the relationship between the optimal modulation depth, am, and the Celsius temperature, T, can be precisely described by the equation am=0.291 8-3.265 14×10-4T+2.282 14×10-7T2. These results are of great significance for the optimization of the modulation parameters of the ammonia escape monitoring system in coal-fired power plants.

Airy beams have three major properties: non-diffraction, self-acceleration, and self-healing, among which the self-acceleration property is the most attractive. To fully understand the Airy beam's self-acceleration characteristics and to ensure its trajectory's integrity, the relative position and rotation angle of the cubic phase in the phase diagram was changed based on geometric transformation to explore the transmission characteristics of the Airy beam. Fourier optics was used to derive the corresponding spectral formula. The results show that the phase map geometric transformation modulation can significantly change the position of the propagation trajectory and the spatial deflection of the Airy beam. This study provides a more comprehensive understanding of the field and application of the self-accelerating properties of Airy beams and provides new ideas for the understanding of controlling other accelerated beams.

Thulium fiber laser is a new type of laser with excellent lithotripsy potential, which has received wide attention in the field of urology in recent years. This paper discusses its performance characteristics, lithotripsy principles, lithotripsy safety and clinical applications. Compared with holmium laser, it has higher lithotripsy efficiency and safety, and its clinical application is expected to promote a new change in the field of urolithiasis treatment in urology.