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Polarization-Insensitive Laser Scanning and Profiling using Amplitude-Modulated CW Scheme
摘要： Laser scanners have emerged as powerful instrument for high-precision 3D geometry measurement. However, such attractive laser scanners have failed to address to drop of receiving power due to laser’s interaction with the surface of the object under measurement. This is a serious weakness of laser scanning systems since it can result in data deterioration and data loss in the acquired 3D point clouds. Numerous studies have been carried out on laser illumination on rough surfaces and have shown that interference between backscattered lights within the laser beam spot forms speckles which affect the level of the receiving power. In this article, we propose a laser scanner having a rapid and continuous polarization scrambling function and cope with the drop in the receiving power. This is the first report of speckle reduction with depolarization approach for laser scanning used for industrial measurement.
关键词： Interference,Optical polarization,Shape measurement,Laser radar,Surface roughness
更新于2025-09-19 17:13:59
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Strategy of Residual Stress Determination on Selective Laser Melted Al Alloy Using XRD
摘要： Selective laser melting (SLM) is known to generate large and anisotropic residual stresses in the samples. Accurate measurement of residual stresses on SLM-produced samples is essential for understanding the residual stress build-up mechanism during SLM, while a dramatic fluctuation can be observed in the residual stress values reported in the literature. On the basis of studying the influence of surface roughness on residual stress measured using X-ray diffraction (XRD), we propose a procedure coupling XRD technique with pretreatment consisting of mechanical polishing and chemical etching. The results highlight that residual stresses measured using XRD on as-built SLM-produced samples with high surface roughness are significantly lower than those measured on samples with finished surface, which is due to the stress relaxation on the spiked surface of as-built samples. Surface distribution of residual stresses and the effect of scanning strategy were systematically investigated for SLM-produced AlSi10Mg samples. Microstructural morphology was observed at the interface between sample and building platform and was linked to the surface distribution of residual stresses. This procedure can help us accurately measure the residual stresses in SLM-produced samples and thus better understand its build-up mechanism during the SLM process.
关键词： X-ray diffraction (XRD),residual stresses,AlSi10Mg,selective laser melting,surface roughness
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Dust Abrasion Damage on Martian Solar Arrays: Experimental Investigation and Opportunity Rover Performance Analysis
摘要： A novel technique for parameterizing surface roughness in coastal inundation models using airborne laser scanning (lidar) data is presented. Two important parameters to coastal overland flow dynamics, Manning’s n (bottom friction) and effective aerodynamic roughness length (wind speed reduction), are computed based on a random forest (RM) regression model trained using field measurements from 24 sites in Florida fused with georegistered lidar point cloud data. The lidar point cloud for each test site is separated into ground and nonground classes and the z-dimensional (height or elevation) variance from the least squares regression plane is computed, along with the height of the nonground regression plane. These statistics serve as the predictor variables in the parameterization model. The model is then tested using a bootstrap subsampling procedure consisting of removal without replacement of one record and using the surviving records to train the model and predict the surface roughness parameter of the removed record. When compared with the industry standard technique of assigning surface roughness parameters based on published land use/land cover type, the RM regression models reduce the parameterization error by 93% (0.086–0.006) and 53% (1.299–0.610 m) for Manning’s n and effective aerodynamic roughness length, respectively. These improvements will improve water level and velocity predictions in coastal models.
关键词： lidar,Manning’s n,random forest (RM),land cover,Aerodynamic roughness
更新于2025-09-19 17:13:59
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Collaborative Optimization of Density and Surface Roughness of 316L Stainless Steel in Selective Laser Melting
摘要： Although the concept of additive manufacturing has been proposed for several decades, momentum in the area of selective laser melting (SLM) is ?nally starting to build. In SLM, density and surface roughness, as the important quality indexes of SLMed parts, are dependent on the processing parameters. However, there are few studies on their collaborative optimization during SLM to obtain high relative density and low surface roughness simultaneously in the literature. In this work, the response surface method was adopted to study the in?uences of di?erent processing parameters (laser power, scanning speed and hatch space) on density and surface roughness of 316L stainless steel parts fabricated by SLM. A statistical relationship model between processing parameters and manufacturing quality is established. A multi-objective collaborative optimization strategy considering both density and surface roughness is proposed. The experimental results show that the main e?ects of processing parameters on the density and surface roughness are similar. We observed that the laser power and scanning speed signi?cantly a?ected the above objective quality, but the in?uence of the hatch spacing was comparatively low. Based on the above optimization, 316L stainless steel parts with excellent surface roughness and relative density can be obtained by SLM with optimized processing parameters.
关键词： 316L stainless steel,multi-objective optimization,relative density,selective laser melting,surface roughness
更新于2025-09-19 17:13:59
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Roughness and wettability properties of plain and silica-coated copper surfaces textured with picosecond laser
摘要： Many recent studies have investigated the mechanism of wettability transition of laser-textured copper surfaces on di?erent materials. Furthermore, several such studies have focused on approaches to accelerate wettability transition from hydrophilicity to hydrophobicity, such as temperature annealing and the use of chemical solutions. However, few researchers have focused on maintaining the initial hydrophilicity of laser-textured surfaces. This study presents a hybrid surface modi?cation method involving chemical bath deposition and ultrafast laser. First, the selected copper substrates are modi?ed using the sol-gel method through dip coating. Subsequently, the coated copper surfaces are irradiated with a picosecond laser. After laser texturing, bumpy structures are formed, and SiO2 nanoparticles can be sintered on the surfaces. Thus, the original hydrophilicity can be maintained, and the surface roughness can be enhanced simultaneously. By using this hybrid modi?cation method, a heterogeneous surface with high-precision patterns can be obtained. Moreover, the mechanism of wettability transition of laser-textured copper surfaces with di?erent laser ?uences is discussed using the Wenzel and Cassie Baxter wetting model by analyzing the chemical composition and surface morphology of the treated surfaces.
关键词： Roughness,Copper,Laser texturing,Wettability,Picosecond laser,Sol-gel
更新于2025-09-19 17:13:59
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Investigation of Laser Polishing of Four Selective Laser Melting Alloy Samples
摘要： Selective laser melting (SLM) is a layer by layer process of melting and solidifying of metal powders. The surface quality of the previous layer directly affects the uniformity of the next layer. If the surface roughness value of the previous layer is large, there is the possibility of not being able to complete the layering process such that the entire process has to be abandoned. At least, it may result in long term durability problem and the inhomogeneity, may even make the processed structure not be able to be predicted. In the present study, the ability of a fiber laser to in-situ polish the rough surfaces of four typical additive-manufactured alloys, namely, Ti6Al4V, AlSi10Mg, 316L and IN718 was demonstrated. The results revealed that the surface roughness of the as-received alloys could be reduced to about 3 μm through the application of the laser-polishing process, and the initial surfaces had roughness values of 8.80–16.64 μm. Meanwhile, for a given energy density, a higher laser power produced a laser-polishing effect that was often more obvious, with the surface roughness decreasing with an increase in the laser power. Further, the polishing strategy will be optimized by simulation in our following study.
关键词： laser polishing,additive manufacturing,selective laser melting,typical alloys,surface roughness
更新于2025-09-19 17:13:59
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Laser Beam Polishing of Polymers
摘要： Fused layer manufacturing (FLM) is an additive manufacturing process in which parts are built in layers by localized extrusion of molten polymer through a nozzle. It offers a high degree of geometrical flexibility as well as a wide range of suitable materials. Unfortunately, a characteristically high surface roughness is limiting the number of possible applications. The following article provides investigations regarding the remelting of FLM surfaces via laser beam polishing as an effective method for achieving a reduced roughness.
关键词： FLM-printed parts,polymers,laser beam polishing,surface roughness,additive manufacturing
更新于2025-09-19 17:13:59
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Laser Polishing of Ti6Al4V Fabricated by Selective Laser Melting
摘要： Selective laser melting (SLM) is emerging as a promising 3D printing method for orthopedic and dental applications. However, SLM-based Ti6Al4V components frequently exhibit high roughness values and partial surface defects. Laser polishing (LP) is a newly developed technology to improve the surface quality of metals. In this research, LP is applied to improve the surface ?nish of components. The results show that the laser beam can neatly ablate the aggregates of metallic globules and repair cracks and pores on the surface, resulting in a smooth surface with nanocomposites. Overall, the results indicate that using LP optimizes surface morphology to favor fatigue behavior and osteoblastic di?erentiation. These ?ndings provide foundational data to improve the surface roughness of a laser-polished implant and pave the way for optimized mechanical behavior and biocompatibility via the laser process.
关键词： laser polishing,additive manufacturing,biocompatibility,mechanical properties,surface roughness
更新于2025-09-19 17:13:59
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Laser polishing of tool steel using a continuous-wave laser assisted by a steady magnetic field
摘要： Continuous-wave (CW) lasers are widely used in laser polishing, but with CW laser polishing, it is difficult to reduce the surface roughness to 0.2 μm from an original value exceeding 1.0 μm. The aim of this study is to develop an innovative method of laser polishing assisted by a steady magnetic field to overcome that bottleneck and produce smoother surfaces. Two experiments confirm the hypothesis that the molten pool overflows during melting peaks to flow into valleys in CW laser polishing, resulting in secondary roughness that causes the aforementioned quality bottleneck. To either reduce or eliminate this secondary roughness, a steady magnetic field is used during CW laser polishing to suppress the overflow of the molten pool. A three-dimensional surface profiler, a scanning electron microscope, and a nanometer indentation tester are used to characterize and analyze the microstructure and properties of the materials. The experimental results show that the Lorentz force due to the steady magnetic field plays an important suppression role in reducing the secondary roughness.
关键词： laser polishing,steady magnetic field,Lorentz force,molten pool overflow,continuous-wave laser,surface roughness
更新于2025-09-19 17:13:59
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Evaluation of Terrestrial Laser Scanner and Structure from Motion photogrammetry techniques for quantifying soil surface roughness parameters over agricultural soils
摘要： The surface roughness of agricultural soils is mainly related to the type of tillage performed, typically consisting of oriented and random components. Traditionally, soil surface roughness (SSR) characterization has been difficult due to its high spatial variability and the sensitivity of roughness parameters to the characteristics of the instruments, including its measurement scale. Recent advances in surveying have greatly improved the spatial resolution, extent, and availability of surface elevation datasets. However, it is still unknown how new roughness measurements relates with the conventional roughness measurements such as 2D profiles acquired by laser profilometers. The objective of this study was to evaluate the suitability of Terrestrial Laser Scanner (TLS) and Structure from Motion (SfM) photogrammetry techniques for quantifying SSR over different agricultural soils. With this aim, an experiment was carried out in three plots (5 × 5 m) representing different roughness conditions, where TLS and SfM photogrammetry measurements were co-registered with 2D profiles obtained using a laser profilometer. Differences between new and conventional roughness measurement techniques were evaluated visually and quantitatively using regression analysis and comparing the values of six different roughness parameters. TLS and SfM photogrammetry measurements were further compared by evaluating multi-directional roughness parameters and analyzing corresponding Digital Elevation Models. The results obtained demonstrate the ability of both TLS and SfM photogrammetry techniques to measure 3D SSR over agricultural soils. However, profiles obtained with both techniques (especially SfM photogrammetry) showed a loss of high-frequency elevation information that affected the values of some parameters (e.g. initial slope of the autocorrelation function, peak frequency and tortuosity). Nevertheless, both TLS and SfM photogrammetry provide a massive amount of 3D information that enables a detailed analysis of surface roughness, which is relevant for multiple applications, such as those focused in hydrological and soil erosion processes and microwave scattering.
关键词： roughness parameters,TLS,soil surface roughness,SfM photogrammetry,agricultural soils
更新于2025-09-16 10:30:52