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Grinding performance improvement of laser micro-structured silicon nitride ceramics by laser macro-structured diamond wheels
摘要： Silicon nitride ceramics are widely used in various industrial ?elds because of their excellent characteristics: high hardness, high elastic modulus, abrasion resistance, and high heat resistance. Diamond wheel grinding is the predominant and most productive method to machine silicon nitride ceramics. However, a lot of heat is generated due to high friction between a diamond grinding wheel and extremely rigid silicon nitride during grinding. This causes surface/subsurface damage, wheel wear, etc., which impairs the surface quality of silicon nitride. This impairment can restrict the use of silicon nitride ceramic components. To improve the surface quality and service life of grinding wheels, a laser macro-micro combination structured grinding (LMMCSG) method was presented. The results indicated that the grinding force ratio and surface roughness when using LMMCSG were respectively 31% and 40% lower than the grinding force ratio and surface roughness when using conventional grinding. Moreover, the LMMCSG method e?ectively reduced the wheel wear and workpiece subsurface damage.
关键词： Macro–micro combination,Laser structured grinding,Wheel wear,Silicon nitride ceramic,Grinding force ratio,Surface roughness
更新于2025-09-11 14:15:04
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Effect of Centrifugal Shot Peening on the Surface Properties of Laser-Cut C45 Steel Parts
摘要： This article presents the results of experimental studies of the impact of centrifugal shot peening parameters on the roughness, microstructure, and microhardness of the surface layer of laser-cut C45 steel parts. Residual stress distributions and the presence of iron oxides on the surface of these elements were also examined. Centrifugal shot peening tests were performed on an FV-580a vertical machining center while using a specially designed peening head. The parameters that were varied during centrifugal shot peening included tangential speed of the tool vg and feed rate vf. The use of centrifugal shot peening for finish machining of laser-cut C45 steel parts allowed for obtaining a four-fold reduction in the surface roughness parameters Ra and Rz. As a result of shot peening, the geometrical structure of the surface of the steel parts was modified and it acquired new beneficial features, such as large values of the rounding radii of the micropeaks and high material ratios (Rmrmax = 92%). At the same time, the surface layer was hardened (microhardness increased by 16%) and a compressive residual stress layer was produced on the surface of the workpieces. Additionally, as the shot impacted the processed surface, combustion products were “blasted” or “sheared” off it. Shot peening using the proposed technique can be successfully performed while using CNC machines.
关键词： laser cutting,residual stress,microhardness,centrifugal shot peening,microstructure,surface roughness
更新于2025-09-11 14:15:04
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Optimierter Laserspeckle-basierter Rauheitsmessprozess für bewegte, spiegelnde Oberfl?chen
摘要： This article describes the upcoming development of a parametric-optical laser measurement system for characterization of surfaces inline some production process. The measurement system is based on previously known approaches for characterization of specular surfaces using coherent light and auto-correlation on the resulting speckle intensity distribution. In order to apply these methods inline, a significantly increased measurement rate has to be reached, compared to existing solutions. This shall be achieved by modifications of the measurement process, use of hardware acceleration for image capturing and processing, and optimization of the processing algorithms.
关键词： speckle,Surface,hardware acceleration,FPGA,scattered light,roughness,laser,metrology
更新于2025-09-11 14:15:04
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Surface topography following pulsed laser texturing: Implications for adhesion and wettability
摘要： A model for predicting surface topography following nanosecond pulsed laser texturing of metals is applied to calculating the areal surface roughness, Sa, average ablation depth, Da, and Wenzel roughness factor or adhesion area ratio, r, for a range representative cases relating to adhesion and wettability. Optimisation of the laser scanning strategy, number of laser passes and focused spot size is performed by considering the ratio of increases in Sa and r with respect to the average ablation depth: ???? ????? values of ???? ????? focused spot size in both the scanning and lateral directions. Increases in Sa, r and ???/???? can be achieved by performing multiple laser passes, while r and ???/???? can be increased independently of Sa and ???? ????? by reducing the focused laser spot size. These results suggest that r and Sa can be optimised effectively and independently in line with a given application. Finally, laser texturing experiments are performed on AA 6082 aluminium alloy and 316L austenitic stainless steel specimens with the aim of confirming model outcomes, after which tensile tests are performed on adhesive-bonded joints prepared with the same laser treatments. Further to demonstrating the benefits of laser texturing, it is shown that optimum results are not necessarily associated with a single value of Sa or r, but are instead a compromise between maximising these parameters and limiting the ablated volume.
关键词： Adhesion,Topography,Surface Roughness,Laser Texturing,Wetting
更新于2025-09-11 14:15:04
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Effect of Sampling Interval and Anisotropy on Laser Scanning Accuracy in Rock Material Surface Roughness Measurements
摘要： Three-dimensional laser scanning is an advanced technique for fracture roughness measurements. The surface roughness of fractures (discontinuities) accurately measured is of practical importance for proper evaluation of the mechanical properties of a fractured rock material. It is also appropriate to perform a more systematic study on the effect of a sampling interval on the roughness measurement accuracy. This effect was investigated based on the 3D-point-cloud data of a fracture surface acquired with laser scanning. A series of 2D profiles corresponding to twelve directions were extracted from concentric circular sampling windows of different diameters. The roughness measurement accuracy is quantified by the three parameters, viz the mean square first derivative Z2 , structure function SF , and roughness profile index R p . The sampling interval effect was investigated for its different values by analyzing the three parameters of different profiles. It was established that SF was very sensitive, while Z2 and R p were less responsive to the sampling interval. It exerts a much weaker influence on the rock material fracture roughness in comparison with anisotropy.
关键词： sampling interval effect,rock material fracture,rock discontinuity,surface roughness,three-dimensional laser scanning
更新于2025-09-11 14:15:04
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Study on magnetic abrasive finishing of AlSi10Mg alloy prepared by selective laser melting
摘要： Selective laser melting (SLM) technology is playing an increasingly important role in today’s manufacturing industry. However, the surface quality of SLM samples is relatively poor and cannot be directly applied to industrial production. Therefore, this paper focuses on the post-treatment process of SLM AlSi10Mg alloy. First, the rough machining is performed by a grinding process (GP), and then, the magnetic abrasive finishing (MAF) is used for finish machining. The experiment results show that the combination of GP and MAF can effectively reduce the surface roughness and improve the surface quality of SLM AlSi10Mg alloy. The GP reduced the surface roughness to drop from 7 μm (after SLM forming) to about 0.6 μm, and the rough surface with defects such as spheroids and pits evolved into the fine surface with scratches and pores. The MAF reduced the surface roughness to a minimum of 0.155 μm, which resulted in excellent surface morphology. The surface hardness after the GP was higher, and the MAF reduced the hardness of the GP surface.
关键词： Grinding process,Hardness,AlSi10Mg alloy,Selective laser melting,Surface roughness,Magnetic abrasive finishing
更新于2025-09-11 14:15:04
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Ultra-precise surface processing of LYSO scintillator crystals for Positron Emission Tomography
摘要： The Lutetium-Yttrium Oxyorthosilicate (LYSO) is one of the most widely used scintillation crystal in the high-performance Positron Emission Tomography (PET) systems. The quality of the surface ?nish of the LYSO has an important impact on the light output, the decoding performance, the energy resolution and timing resolution of the PET detectors and systems. In this paper, we present an ultra-precise method for processing the surface of LYSO crystals. The hardness and elastic modulus of the crystals were initially measured using Nano indentation technology. The scintillators were ?xed onto the plate in sparse, serried and continuous arrangements and polished using an alumina (Al2O3) and cerium oxide (CeO2) polishing solution with particles of varying size. We used a magnetorheological-polishing technique to polish the LYSO crystals. The polishing solution here included hydroxyl iron powder and hard abrasives. The hardness and elastic modulus of the crystals in question was, respectively, 11.18 ± 0.50 and 155.78 ± 4 gigapascals (GPa). A 3D optical surface pro?ler (3D-OPS) and an atomic force microscope (AFM) were used to evaluate the quality of the polished surfaces. The average roughness of Ra 0.55 nm measured by 3D-OPS was achieved using a precise plate grinding and polishing technique. The magnetorheological-polishing method also obtained an excellent roughness of Ra 0.75 nm (3D-OPS). Our report of the use of these processing technologies can serve as a foundation for further in-depth research regarding the optimal techniques for scintillator surface processing.
关键词： Ultra-precision,LYSO crystal,Surface roughness,Positron Emission Tomography
更新于2025-09-11 14:15:04
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Effect of Proton Radiation on Ultra-Wide Bandgap AlN Schottky Barrier Diodes
摘要： Lateral Pd/n-AlN Schottky barrier diodes (SBDs) were fabricated and subjected to 3 MeV proton irradiation at various fluences. Electrical and material characterization analysis was performed before and after each radiation fluence to quantify the change in device characteristics. It was found that the SBDs performed reliably up to a proton irradiation fluence of 5×1013 cm-2, with little or no change in the key device performance such as current, turn-on voltage, ideality factor, and breakdown voltage, etc. The electrical characteristics of the SBDs was well predicted using a standard thermionic emission theory. The performance of the SBDs showed a significant degradation after a high-fluence irritation of 5×1015 cm-2, where the current of the SBDs dropped two orders of magnitude. Material and surface characterizations, including atomic force microscopy and X-ray diffraction, indicated a consistent degradation in the AlN bulk crystal quality and a drastic increase in surface roughness. These results provide valuable information on the radiation properties of AlN electronics and can serve as important references for the future development of high performance AlN devices for extreme environment applications.
关键词： surface roughness,leakage current,radiation effects,Aluminum nitride,breakdown voltage,barrier height,Schottky barrier diodes,ideality factor,turn on voltage
更新于2025-09-11 14:15:04
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A Coupling Model for Soil Moisture Retrieval in Sparse Vegetation Covered Areas Based on Microwave and Optical Remote Sensing Data
摘要： Soil moisture is an important component of natural water cycles and plays a crucial role for the healthy development of ecological environment in arid and semiarid areas. Microwave remote sensing techniques are promising to rapidly monitor regional soil moisture. However, major difficulties associated with retrieving soil moisture via microwave remote sensing are attributed to effects of surface roughness and vegetation cover. The objective of this paper is to investigate the potentials of combined roughness parameters and develop a model that mostly relies on the satellite data and requires minimum a priori information for soil moisture inversion over sparse vegetation covered areas through combing Radarsat-2 synthetic aperture radar (SAR) and GF-1 data. For the purpose, the impacts of vegetation on the radar backscattering coefficient were removed by the water-cloud model (WCM) and a new roughness parameter Zs (Zs = S3/L is defined as a combined roughness parameter) was proposed by simulating relationships between surface roughness parameters, soil moisture, and backscattering coefficients using advanced integral equation model (AIEM). On the basis, a coupling model of soil moisture inversion for blown-wind areas of the Uxin Banner in Inner Mongolia, China, was in turn developed with Radarsat-2 HH and VV polarization data, and the soil moisture content (SMC) values for sparse vegetation covered surfaces were retrieved with limited use of in situ roughness parameters. The in situ measurements and satellite data set were used to validate the reliability of the developed model. The results showed that the retrieved soil moisture levels fell below in situ soil moisture levels before the vegetation effect was removed, and the precision of retrieved soil moisture was effectively improved when the vegetation effect was corrected by the WCM, with the root-mean-square error and mean absolute error decreasing from 7.45% and 6.24% to 5.12% and 3.44%, respectively. According to the map of retrieved soil moisture levels generated for the study area, most of SMCs were below 35% in accordance with field observations. These study results can serve as a foundation for monitoring soil moisture and water environments in arid and semiarid regions.
关键词： Combined roughness parameter,sparse vegetation,coupling model,radiative transfer model,soil moisture retrieval
更新于2025-09-11 14:15:04
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Experimental investigations on super-smooth polishing of strontium titanate based ceramics substrates
摘要： Strontium titanate (SrTiO3) is a new type of multi-function electronic ceramic material. SrTiO3 ceramic substrates with a high dielectric constant can be obtained by non-pressurised sintering using ultrathin blanks, which result in the characteristics of thin, soft, brittle and warped. So that SrTiO3 ceramics substrates need to be polished to improve surface quality and dimensional precision before application. In this research, polish experiments with various processing parameters on the surface roughness, the material removal rate and the surface morphologies of SrTiO3 ceramic substrates were conducted. The results show that the SrTiO3 ceramic substrate with a highest quality surface was obtained in the condition: employing a brown polyurethane pad to polish the substrates at a polishing velocity of 45 r/min. Meanwhile, the slurry flow rate, the concentration of the polishing slurry and the polishing pressure were 20 ml/min, 4 wt% and 15.043 kPa, respectively, which rates with an overall and a partial surface roughness of Ra 0.01 μm and Ra 4 nm, respectively. While some new micro-scratches were generated on the surface of the SrTiO3 ceramics substrate in the polishing process because the embedding and scratching of abrasive particle led to expose the inherent pores and grain boundaries.
关键词： ceramic substrate,material removal rate,strontium titanate,polishing,surface roughness
更新于2025-09-10 09:29:36