The trowel shovel, the key component of the nudus harvester, is easy to wear and corrode after working in seawater for a long time, which leads to the failure of the parts. To improve its hardness and corrosion resistance, a reinforcement layer can be applied to its surface to extend its lifespan. In this study, XL-F2000T laser was used to cladding 10%, 20% and 30% WC and Ni on the surface of 06Cr17Ni12Mo2 stainless steel as reinforced coatings. Use MHVD-1000AT hardness testing equipment to measure the hardness of the cross section. The phase composition was analyzed by Shimadzu XRD. The corrosion resistance in 3.5% NaCl solution was tested by CS Studio electrochemical workstation. The findings suggest that a WC+Ni60 composite coating can significantly enhance the surface hardness of 06Cr17Ni12Mo2 stainless steel. While the average hardness increases with WC content, the cross-sectional hardness of the sample clad with 30%WC+Ni60 displays significant fluctuation, whereas the hardness of the 10%WC+Ni60 cladding layer remains relatively stable. Furthermore, each cladding layer′s self-corrosion potential Ecorr is positive relative to the substrate, with 10%WC+Ni60 exhibiting superior corrosion resistance. Comprehensive comparative analysis shows that 10%WC+Ni60 can ensure both high, consistent hardness and excellent corrosion resistance.

In order to improve the hardness and wear resistance of Q235 steel, Ni-Ti-Cr-(CNTs) composite coatings was prepared on the surface of Q235 steel by laser cladding technology, and the effects of laser cladding parameters on the forming quality, microstructure and mechanical properties of the composite coatings were studied. Results indicate that the principal phases of the composite coatings consist of TiC, Fe2Ti, Cr7C3, FeNi, (Fe,Ni), and Cr, with the laser cladding parameters exhibiting minimal impact on the primary phase compositions of the coatings. With lower laser specific energy, a poor bond between the coating edge and substrate is observed. However, as the laser specific energy increases, reinforced ceramic particles within the composite coating enlarge, and an escalated level of iron seeps into the composite coating from the substrate, consequently reducing its hardness and wear resistance. Compared with Q235 low carbon steel substrate, the maximum microhardness of the composite coatings is approximately 5 times greater and demonstrates significant improvements in wear resistance.

In order to achieve the explosion-proof function, most of the blast blower impellers use casting copper alloy as a whole component. This method consumes lots of manufacturing resources and is also expensive. The cladding of copper alloys on the surface of casting ironed impellers by L-DED (Laser Directed Energy Deposition) can effectively reduce resource consumption and save costs. However, the huge difference in physical properties between cast iron and copper alloys, coupled with the extremely low laser absorption of copper alloys lead to defects such as oxidation, cracking and difficulty in L-DED process. To achieve high-quality L-DED copper alloys on casting iron surfaces, the effect of temperature gradient control strategies such as preheating and slow cooling processes on the quality of L-DED were investigated. Additionally, we evaluated the effect of transition layers of NiCrBSi and Inconel 718 on deposition quality, by analyzing microstructure morphology and measuring the microhardness at the bonding interface. The study also covers the completion of L-DED process path planning for complex impeller surfaces. Ultimately, employing a preheating and slow cooling process and selecting suitable transition layers enabled successful achievement of L-DED CuSn15 alloy on the surface of a cast iron impeller, devoid of cracks, holes or other defects.

Reducing the weight of automobile components is of significant importance in achieving energy efficiency and emission reduction. To meet the performance requirements and specific strength necessary for their intended use, key components must possess superior service performance. Due to the advantages of light weight, high strength and easy processing, aluminum alloy is always used in the processing and manufacturing of automobile parts, such as steering knuckle, control arm, wheel hub, etc. Taking the steering knuckle part as an example, due to its complex structure, it is difficult to meet the dual requirements of manufacturing accuracy and service strength by using traditional processing technology, but additive manufacturing can solve this problem effectively. In this paper, the A357 aluminum alloy was prepared by selective laser melting, and its microstructure, mechanical properties and fatigue failure mechanism were studied in detail. The results show that the microstructure of A357 aluminum alloy is equiaxed and columnar grains with an alternate distribution. The tensile strength of the alloy is 337-351 MPa, and the elongation after fracture is 10.3%-11.0%. As the fatigue load decreases, the number of cyclic load applications gradually increases. Under the stress state of 100 MPa, the number of cyclic load applications can reach as high as 3.08×106 times.

The 7075 aluminum alloy, belongs to the Al-Zn-Mg-Cu series of ultra-high strength aluminum alloy, finds extensive application in aerospace structural component manufacturing. However, the wide solidification range of this alloy poses challenges when utilizing selective laser melting (SLM) technology for printing and forming, as it often leads to crack defects that severely compromise the load-bearing performance of the components. This study focuses on addressing the cracking issue encountered during the SLM printing process of the 7075 aluminum alloy. To mitigate this problem, the original 7075 aluminum alloy powder undergoes a microalloying treatment using ball milling and powder mixing techniques involving Ti and Zr composite addition. By incorporating 0.7% (by mass fraction) Zr and 0.5% (by mass fraction) Ti, all internal cracks and defects within the alloy are effectively eliminated. Additionally, the microstructure characteristics undergo a transformation from coarse columnar grains to an alternating distribution of coarse and fine grains, resulting in a significantly refined grain size. The introduction of Ti and Zr elements facilitates the formation of a coherent Al3(Ti, Zr) phase with the alloy matrix. This not only promotes grain size refinement but also enhances precipitation strengthening, thereby substantially improving the mechanical properties of the printed alloy. As a result, the tensile strength and elongation at break reach (413±8) MPa and 23%, respectively.

This study makes use of CAE software to establish a multiphysics field model concerning the flow, solidification, and heat transfer processes of laser-selected 316L stainless steel powder melt pools. The research aims to examine the morphology evolution of the melt pool and analyze the impact of variable process parameters on melt pool morphology, thermal field, and flow field. It was found that the peak temperature at the observation point of the melt pool, the maximum flow rate of the melt pool, the melt width, the melt depth and the laser energy absorbed by the powder increased with the increase of laser power at the scanning speed of 600 mm/s, and decreased with the increase of scanning speed at the laser power of 110 W. During the evolution of the melt pool (P=180 W, v=800 mm/s), when t=0.05 ms, the shape of the melt pool is approximately circular; when t=0.30 ms, the shape of the melt pool changes from circular to elliptical, and the temperature of the melt pool remains stable, after which, the shape of the central part of the melt pool is always approximately elliptical; when t=0.65 ms, the depth of the melt pool gradually increases, and the solidification speed When t=1.0 ms, the temperature of the melt pool gradually decreases, and the temperature is lower than the solid-phase line temperature 1 658 K when the melt channel is formed. Under conditions of a 600 mm/s scanning speed and 110 W laser power, the resulting melt channel demonstrates relative continuity and smoothness, reflecting good quality.

The study explores the impact of varying Ni composition on the microstructure and phase change temperature of 22MnB5 hot-formed steel jointed through laser welding. Employing optical microscopy, tensile testing machines, and JMatPro software, it examines the weld joints created with filler wires of differing Ni content. The results showed that post heat treatment, the joints formed with low-Ni steel wire comprise a mix of martensite and delta-ferrite, attaining a tensile strength of 1357 MPa. Conversely, those created with high-Ni wire yield a fully martensitic microstructure following heat treatment, reaching a joint strength of 1516 MPa-equivalent to 92% strength coefficient. Notably, a higher Ni concentration in welding wire complicates the formation of δ-ferrite during solidification; however, it accelerates the generation rate of γ-austenite.

To enhance the analysis of the relationship between thermal cycle and crystallization in laser welding of amorphous alloys, a transient thermal model was established using ANSYS software′s Workbench platform, and the temperature field change process of laser welding of Zr63.7Cu17.5Ni13.1Ti3.9Fe1.8 amorphous alloy was analyzed. The temperature field and the sizes of melting zone and heat affected zone in the weld zone were obtained by simulation. The thermal cycle curves of several characteristic points were obtained by adding temperature probes. The thermal analysis was carried out according to the thermal cycle curves and DSC curves. Through the test results and analysis, it is found that the simulation results are in good agreement with the experimental metallographic images of the corresponding region, and the cause of crystallization in the heat affected zone is explained through the thermal cycle curve. Therefore, the study shows that given optimized and reasonable boundary conditions, temperature field simulation can predict the morphology and crystallization region of Zr-based amorphous alloy during laser welding. This insight could prove valuable for optimizing the welding process and guiding subsequent laser welding of the Zr-based amorphous alloy.

The present study investigates the welding of Ti60 titanium alloy T-joints using double laser welding technology. The objective is to examine the surface and internal quality of the joint, analyze the microstructure of each area using an optical microscope, measure the hardness of the joint, and assess the tensile properties of the joint at varying temperatures. The experimental results show that the T-joint exhibits excellent surface and internal quality after being welded with the specified process parameters, with no noticeable defects. Due to variations in the thermal cycle state during welding, the microstructure of each joint area differs across the welding process. Specifically, as the distance from the center of the weld decreases, the grain size gradually increases while the β phase decreases. Moreover, the α and α′ phases experience a gradual increase. In terms of micro-hardness, the heat-affected zone exhibits the highest values, followed by the weld zone, and finally the base metal zone with the lowest values. Tensile testing at different temperatures indicates that the tensile fracture occurs within the base metal. Furthermore, with increasing tensile temperature, both the tensile strength and yield strength decrease gradually, while elongation increases. Notably, the rate of change with temperature is greater above 550 ℃ compared to below.

To investigate the influence of laser cutting processing parameters on the cutting quality of 304 stainless steel with a thickness of 1 mm, a Box-Behnken experiment was designed. A 2 kW fiber laser cutting machine was employed to perform this process while a 3D measurement microscope and precision electronic scale were utilized to gauge the sectional roughness and slag thickness respectively. The study sought to analyze how different process parameters (namely: laser power, cutting speed, auxiliary gas pressure, defocusing amount) influenced the cutting quality. The experimental results show that both laser power and cutting speed significantly impacted the slag thickness, whereas laser power and defocusing amount considerably affected roughness. Drawing upon these experimental results, the response surface method was adopted to develop a three-dimensional response surface model representing both surface roughness and slag thickness. According to the fitting results of the response surface model, and taking the minimum slag thickness and roughness as the index, the laser cutting process parameters were optimized using a genetic algorithm. This yielded a set of optimal process parameters: laser power at 1,175 W, cutting speed at 3.55 m/min, auxiliary gas pressure at 1.55 MPa, and defocusing amount at 0.48 mm.

In order to explore the effect of scanning speed on the microstructure and properties of Ni-based coatings, coatings were prepared by laser cladding technology at different scanning speeds. The coatings were characterized by XRD(X-ray diffraction), Vickers hardness tester and friction tester. The main phases of the coating were found to be ［Fe Ni］ and Fe. The hardness of the coating is obviously higher than that of the substrate. The uniformity of the coating is the best under the scanning speed of 10 mm/s, and the hardness reaches 430 HV. In the friction test, the wear resistance of the coating first increased with the increase of the scanning speed. At the turning point of 10 mm/s, the wear amount of the coating was 51.7 mg, and then the wear resistance of the coating decreased with the increase of the scanning speed. This phenomenon is also similar in hardness testing. The coating with the best performance can be prepared only by the appropriate scanning speed when preparing the coating. The optimal scanning speed in this experiment is 10 mm/s.

In this study, nine sets of process schemes were designed to utilize nanosecond pulse lasers in conjunction with high-speed galvanometers for the purpose of clearing surface stains from automobile brake discs. Typical experimental studies were carried out on three groups of optimal morphology parameters, the results show that the surface after laser cleaning is bright and smooth, and the minimum surface roughness reaches Ra (1.2 ± 0.3) μm. The thickness of the cleaning layer is about (80 ± 11) μm in the three groups of optimal parameters, and the surface microhardness increased from the original (360 ± 13) HV to (598 ± 26) HV. Despite encountering residual tensile stress post-cleaning, there was a marked enhancement in surface wear resistance, accompanied by a reduction in the friction coefficient from 8.56 to 3.26.

This research investigates the parallel cutting process of silicon wafer using a green picosecond laser, spatial light modulator, and GS feedback algorithm. It examines the influence of several factors such as the overlap ratio of adjacent beams in multiple beams, defocus magnitude of beams, and the energy of single pulses from defocused beams on the depth and flatness of slits. The results show that the laser overlap ratio should be controlled between 70% ~ 80%, which can maximize the single cutting depth and make the bottom of the cutting groove flat. The positive defocus of the array beam is helpful to improve the flatness of the bottom of the cutting groove. The defocus amount is determined by the Rayleigh length of the focused beam and the beam aberration. Under these experimental conditions, optimal results are yielded when the defocus quantity is maintained at 1 to 2 times the Rayleigh length. After the multi-beam is defocused, the cutting depth is reduced. In a certain range, the cutting depth can be effectively improved by increasing the single pulse energy of the defocused beam in the multi beam without affecting the flatness of the bottom of the cutting groove.

This study utilizes laser alloying technology to develop MoSi2 composite layers enhanced with Al and Nb elements on a Cr12 substrate. Utilizing OM, SEM, EDS, and XRD, the research investigates the influence of multi-component addition of Al and Nb elements on the low-temperature oxidation characteristics of MoSi2 composite layers. The resulting microstructure of the laser-alloyed MoSi2 layer reveals a sequence from the surface layer of equiaxed crystals, dendrites, columnar crystals, and cellular crystals. Incorporation of Al and Nb elements displays an enhancement in the oxidation resistance of the MoSi2 composite layer. Even after exposure to 550 ℃ air for 24 days, the alloy layer shows no signs of decomposition into powder. The surface oxidation products lack MoO3 phase, and the weight increase in the oxidized layer is attributed to Fe and Al oxidation reactions. The protective mechanism of Al2O3 and the compactness of the alloy layer effectively inhibit the low-temperature pesting of MoSi2.

This paper investigates the microstructure alterations of aluminum surfaces subjected to ultrasonic vibration-assisted laser processing. It encompasses an analysis on laser ablation thresholds computation on material surfaces and scrutinizes experimentally the influence of laser pulse frequency and ultrasonic vibration on the diameter of laser ablation craters. Results revealed that ultrasonic vibration application led to a decrease in crater diameter by 0.67 μm to 2.82 μm, an elevation in the ablation threshold from 5.76 J/cm2 to 6.52 J/cm2, and an increase in trajectory width from 46.3 μm to 62.2 μm at a scanning speed of 100 mm/s. Furthermore, it enabled the formation of a unique ellipsoidal structure exhibiting reduced surface roughness.

This study introduces a particle shading tracer technique to measure flow velocity in microporous channels in industrial applications, based on the principle of utilizing tracer particles to ascertain average flow velocity. Tracer particles, typically 5 ~ 15 μm particles prevalent in industrial system fluid mediums, are employed. To enhance the relative intensity of the tracer particles′ shading signal and counteract the potential drowning effect of field electromagnetic interference, a microporous window was designed to control the laser cross-section size. The velocity of fluid medium is determined by assessing the particle′s transit time through the laser beam and analyzing its speed. The measuring device was designed and its method validated through experiments. When the Stokes number of 5~15 micron particles in the flow field is controlled below 0.1 and the flow velocity is in the range of 0.27~2.76 m/s, the deviation from the theoretical value of the measured local flow velocity in the microfluidics is less than 8%. It is proved that the method is suitable for measuring the average velocity of the flow field in the industrial system.

The construction of mining subsidence basin is of great significance to the study of surface deformation characteristics and failure mechanism. While airborne LiDAR point cloud′s application in constructing subsidence basins remains experimental, this paper proposes a novel approach considering the significant effects of vegetation and topography on mountain subsidence basins. After analyzing the impact of slope variation factors and point cloud vegetation density on basin precision, we introduce a coarse difference filtering method based on a sliding window. This is followed by deploying wavelet theory to filter out high-frequency errors, determining the subsidence basin boundary through sample statistics, and ultimately constructing a highly precise subsidence basin. The results show that the mean square error of the subsidence basin decreases from 0.195 m to 0.072 m, with the maximum error dropping from 1.342 m to 0.245 m. This provides a fresh methodology for constructing subsidence basins in mountainous regions.

In order to solve the problem that traditional vital sign measurement is limited in use scenarios and realize non-contact vital sign measurement, this paper proposes a method to measure human vital signs by using laser frequency modulated continuous wave ranging system. In this paper, the life signal measured by the laser frequency modulated continuous wave ranging system is smoothed and filtered to remove the random movement signal of the body, and then the processed signal is decomposed by ensemble empirical mode to separate the heartbeat signal and respiratory signal. The vital signs of healthy adults were measured under normal static conditions and breath-holding conditions. The experimental results show that the respiratory rate measured by the algorithm provided in this paper is 17-20 times /min and the heart rate is 75-90 times /min. The experimental results are consistent with biological laws and reflect the feasibility of the algorithm, which is expected to provide reference value for some special scenes, such as neonatal vital signs monitoring and non-contact vital signs measurement of severe burn patients.

This paper addresses the challenges of point cloud data, which possess attributes such as large volume, high redundancy, and an unstructured nature. In light of time consumption and poor robustness issues arising when directly applying the Iterative Closest Point (ICP) algorithm to point cloud data with inadequate initial pose, an enhanced point cloud registration algorithm is proposed. First, the voxel grid filtering algorithm is used to simplify the point cloud; then extract the 3D Scale Invariant Feature Transform (3DSIFT) feature points of the point cloud, and combine with Fast Point Features Histograms (FPFH) to extract the features, next, use the direction vector threshold algorithm to remove the wrong matching point pairs, then, according to these features, the Random Sample Consensus (RANSAC) algorithm combine with the SVD algorithm is used to calculate the transformation parameters and complete the rough registration; Finally, the improved ICP algorithm based on KD-tree acceleration is used to complete the fine registration. The results show that the average registration accuracy of the proposed algorithm is 17.96%, 47.39%, 69.88% and 79.78% of the four comparison algorithms, and the registration time is shortened on the basis of weighing the registration accuracy.

Addressing the issues of low efficiency and imprecision in current multi-line LiDAR point cloud fusion methods, this paper presents an innovative algorithm based on the Inertial Measurement Unit (IMU) and an enhanced Iterative Closest Point (ICP) technique. First, voxel filtering is used to downsample the point cloud, then the discrete points in the LiDAR point cloud are eliminated by the Statistical-Outlier-Removal filter, and the IMU information is introduced to complete the distortion correction of the point cloud; Further, the improved sampling consistency initial alignment (SAC-IA) algorithm and the improved ICP algorithm are applied for the initial and accurate registration of the feature point clouds of the current and historical frames. The algorithm is tested in two different scenes, in the outdoor experimental environment, compared with the traditional Normal Distributions Transform (NDT), Fast Point Feature Histograms (FPFH) and NDT-ICP algorithms, the root mean square errors of the registration of this algorithm are 87.60%, 59.25% and 87.88%, respectively. In the indoor environment, the root mean square errors are 74.69%, 37.90% and 81.32%, respectively. These results demonstrate the superior accuracy of point cloud registration offered by our algorithm, affirming its capability to achieve high-precision fusion between point clouds of two frames.

In order to solve the problems such as the low registration efficiency of the iterative nearest point algorithm and the accuracy depending on the good initial posture of the point cloud, this paper proposes a point cloud coarse registration method based on the internal shape descriptor and the improved fast point feature histogram. Firstly, voxel filtering is used to preprocess the initial point cloud, and then the internal shape description sub-algorithm is adopted to extract the feature points of the initial point cloud and find the normal vector corresponding to the feature point, and the fast point feature histogram is used to extract the feature vector of the feature point. According to the difference between the angle of the feature vector and the normal vector, the feature points are coarsely registered, which provides a good initial posture for the fine registration of the iteration of the nearest point registration algorithm. Experimental results show that the point cloud registration algorithm proposed in this paper can provide a better initial posture for the fine registration of the nearest point algorithm. Compared with several traditional registration methods, the proposed method overcomes the limit of the number of point clouds of registration, and further improves the efficiency and accuracy of registration.

This study assesses the efficacy of iRoot BP Plus in conjunction with Er∶YAG laser application in live pulpotomy for young permanent teeth. Patients aged 8-10 years with anterior crown fractures were selected and randomly assigned to either a laser group or a conventional group. The former underwent depulpation with Er∶YAG laser, while the latter used a turbo handpiece. Postoperative success rates of live pulp preservation at 12 months, pulpotomy duration, hemostasis time, and intraoperative pain were compared between groups. Laser pulpotomy (20 teeth) and turbine pulpotomy (20 teeth) were each conducted on 40 healthy children. After a 12-month follow-up, the success rates for the laser and conventional groups were 85% and 80% respectively, indicating no statistically significant difference (P>0.05). However, the Er∶YAG laser group exhibited longer pulp cutting time but shorter hemostasis time than the conventional group, with both parameters being statistically significant (P<0.05). Additionally, the VAS/VPS scores of the Er∶YAG laser group were lower than those of the conventional group, implying less intraoperative pain (P<0.05). Despite similar overall efficacy between Er∶YAG laser and turbine methods for live pulpotomy in young permanent teeth, the former offered significantly reduced intraoperative hemostasis time and patient discomfort. Given its ease of use and cost-effectiveness, Er∶YAG laser represents a potentially beneficial supplementary technique for pulpotomy.