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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) - In-situ Microscopy Characterization of Cu(In,Ga)Se <sub/>2</sub> Potential-Induced Degradation
摘要： During irradiation UO2 nuclear fuel experiences the development of a non-uniform distribution of porosity which contributes to establish varying mechanical properties along the radius of the pellet. Radial variations of both porosity and elastic properties in high burnup UO2 pellet can be investigated via high frequency acoustic microscopy. For this purpose ultrasound waves are generated by a piezoelectric transducer and focused on the sample, after having travelled through a coupling liquid. The elastic properties of the material are related to the velocity of the generated Rayleigh surface wave (VR). A UO2 pellet with a burnup of 67 GWd/tU was characterized using the acoustic microscope installed in the hot cells of the JRC-ITU at a 90 MHz frequency, with methanol as coupling liquid. VR was measured at different radial positions. A good agreement was found, when comparing the porosity values obtained via acoustic microscopy with those determined using SEM image analysis, especially in the areas close to the centre. In addition, Young’s modulus was calculated and its radial pro?le was correlated to the corresponding burnup pro?le and to the hardness radial pro?le data obtained by Vickers micro-indentation
关键词： Nuclear fuels,piezoelectric devices,Vickers microhardness,Young’s modulus,nuclear power
更新于2025-09-19 17:13:59
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Laser Finishing of Ti6Al4V Additive Manufactured Parts by Electron Beam Melting
摘要： In this work, the feasibility of laser surface ?nishing of parts obtained by additive manufacturing (AM) was investigated. To this end, a 450 W ?ber laser (operating in continuous wave, CW) was adopted to treat the surface of Ti-6Al-4V samples obtained via electron beam melting (EBM). During the tests, di?erent laser energy densities and scanning speeds were used. In order to assess the quality of the treatment, either the as-built or the treated samples were analyzed by means of a three-dimensional (3D) pro?lometer, digital microscopy, and scanning electron microscopy. Analysis of variance (ANOVA) was performed to check which and how process parameters a?ected the ?nishing. The results show that, in the best conditions, the laser treatment reduced surface roughness by about 80%.
关键词： surface roughness,microhardness,EBM,?ber laser
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) - Rough and Straightforward Estimation of the Mismatching Loss by Partial Shading of the PV Modules Installed on an Urban Area or Car-Roof
摘要： During irradiation UO2 nuclear fuel experiences the development of a non-uniform distribution of porosity which contributes to establish varying mechanical properties along the radius of the pellet. Radial variations of both porosity and elastic properties in high burnup UO2 pellet can be investigated via high frequency acoustic microscopy. For this purpose ultrasound waves are generated by a piezoelectric transducer and focused on the sample, after having travelled through a coupling liquid. The elastic properties of the material are related to the velocity of the generated Rayleigh surface wave (VR). A UO2 pellet with a burnup of 67 GWd/tU was characterized using the acoustic microscope installed in the hot cells of the JRC-ITU at a 90 MHz frequency, with methanol as coupling liquid. VR was measured at different radial positions. A good agreement was found, when comparing the porosity values obtained via acoustic microscopy with those determined using SEM image analysis, especially in the areas close to the centre. In addition, Young’s modulus was calculated and its radial pro?le was correlated to the corresponding burnup pro?le and to the hardness radial pro?le data obtained by Vickers micro-indentation
关键词： Nuclear fuels,piezoelectric devices,Vickers microhardness,Young’s modulus,nuclear power
更新于2025-09-19 17:13:59
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CO2 Laser Cutting Performance on Ultra High Strength Steel (UHSS)
摘要： Evolution of a new breed steel, Ultra High Strength Steel (UHSS), has been adapted by the automotive industry after being used for heavy trucks. Higher tensile strength and improved mechanical properties of UHSS are the main reason for its selection particularly in Body In White (BIW) construction at critical chassis area. Laser cutting process is noted as the final trimming method for this harden material as die pressing resulted as an ineffective process. UHSS cutting performance using CO2 laser with variation on laser power, cutting speed, assist gas type and assist gas pressure was determined to identify the effect of these parameters on the cutting quality. Cutting quality assessment was carried out according to EN ISO 9013 standard where kerf width, perpendicularity and microhardness were evaluated based on parameters set at 1.7 mm thickness of 22MnB5 UHSS boron steel. The quality of these cuttings was evaluated as the results show that thermal exposure dependent on energy density and gas type reflect the outcome where higher thermal exposure introduced bigger kerf with better perpendicularity. It was also found that isothermal effects such as Heat Affected Zone (HAZ) and martensitic transformation were also clearly visible since nitrogen produced a better cutting quality and material integrity consumption at the cutting edge.
关键词： Perpendicularity,22MnB5,Microhardness,CO2 laser,Kerf width
更新于2025-09-19 17:13:59
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Underwater wire-feed laser deposition of the Ti–6Al–4V titanium alloy
摘要： Underwater wire-feed laser deposition (UWLD) of the Ti-6Al-4V alloy was firstly carried out utilizing a laser deposition nozzle, and the deposition appearance, geometry characteristics, microstructure and microhardness of deposited tracks were studied. At a lower gas flow rate, the absorption of residual water and scattering of aerosol particles on laser beam caused UWLD instability and decreased molten metal wettability. Upon increasing the gas flow rate, the aerosol particle density decreased, increasing the laser density and decreasing the cooling rate of molten metal; thus, the height and deposition angle of UWLD track decreased as the corresponding width and fusion depth increased. The microstructures of the deposited metal at a gas flow rate of 10 L/min were composed of the coarse lath α phase in upper region and the acicular martensite α′ with different size scales in middle and bottom regions. With increasing the gas flow rate to 20 L/min, the microstructure was primarily acicular martensite along with a small amount of α phase, and the martensite exhibited a larger grain size and stronger texture. At a gas flow rate of 20 L/min, the deposited process was stable and uniform deposition track without oxidation layer was obtained for UWLD Ti-6Al-4V alloy.
关键词： Ti-6Al-4V alloy,Laser propagation mechanism,Microstructure,Microhardness,Underwater wire-based laser deposition,Geometrical characteristics
更新于2025-09-19 17:13:59
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Distribution of Al Element of Ti–6Al–4V Joints by Fiber Laser Welding
摘要： In the process of laser welding, the uneven distribution of solute elements caused by element burning loss and ?ow of molten pool a?ects the quality of joints. In this paper, butt welding experiments were conducted on the 3 mm thick Ti–6Al–4V specimens with di?erent preset ratios of Al and Si powders by using 4 kW ?ber laser. The distribution of Al solute element and its in?uence on the microstructure and mechanical properties of the ?nal weld joint were investigated. The results showed that the self-di?usion of Al element and the ?ow of molten pool a?ects the alloy elements distribution in laser welding. And the microhardness of the welded joint with Ti–6Al–4V and 90% Al + 10% Si powders was signi?cantly higher than that with only Ti–6Al–4V, with the di?erence of about 130HV. At the same time, in the joint with 90% Al and 10% Si powders, the acicular α’ size was ?ner, and basketweave microstructure was present as well. This research is helpful to better understand the distribution of Al solute element and its in?uence on the joint quality during laser welding of Ti–6Al–4V alloy, which provides a certain reference for improving the weld or surface properties of Ti–6Al–4V alloy during laser processing.
关键词： Ti–6Al–4V alloy,structure morphology,laser welding,elements distribution,microhardness
更新于2025-09-16 10:30:52
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Hierarchical Composite Materials (Materials, Manufacturing, Engineering) || 4. Fabrication of stainless steel-based FGM by laser metal deposition
摘要： Recent advancement in materials processing has resulted in the evolution of advanced composite known as functionally graded materials (FGMs). FGMs are multilayered structures with composition and/or microstructure that vary spatially across the volume of the material. This chapter presents an overview of the concept of FGMs in terms and its history. The present and potential applications of FGMs are briefly described, as well as various classification methods. Processing of FGM using laser metal deposition (LMD) is also discussed as well as the influence of LMD process parameters on the quality of laser-processed materials. Studies that have been conducted on metal–metal FGM produced by LMD are presented. Finally, a study on the microstructure and microhardness of laser deposited compositionally graded 316L/17-4PH was also presented.
关键词： Laser metal deposition,Advance composite,Microstructure,Microhardness,Functional graded material
更新于2025-09-16 10:30:52
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Effect of Process Parameters and Heat Input on Weld Bead Geometry of Laser Welded Titanium Ti-6Al-4V Alloy
摘要： Laser beam welding is one of the most favorable welding technique and its importance in industry is demanding due to higher welding speeds and lower dimensions and distortions in the welds. Moreover, its high strength to weld geometries and minimal heat affected zones makes favorable for various industrial applications. In the present study, laser welding of titanium alloy was investigated to observe the effects of parameters on the bead geometry and metallurgical properties. The laser power and welding speeds were varied to identify their impact on the formation of weld geometry. The width and depth of the fusion zone is varied with welding conditions. The finer grains identified in weld zone and the width of heat affected zone was significantly changes with laser welding power. The mechanical properties of the weld joint are controlled by obtaining optimum weld bead geometry and width of the head affected zone in the welds.
关键词： Heat input,Fusion zone,Microstructure,Mechanical properties,Laser welding,Microhardness,Weld bead geometry,Titanium alloy
更新于2025-09-16 10:30:52
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Properties of indirect composites polymerized with laboratory light-emitting diode units
摘要： This study evaluated the light intensity of light-emitting diode (LED) units and the effects of five laboratory polymerization units on hardness and flexural strength. Two indirect composite materials (Cesead N and Solidex Hardura) were polymerized with five units (α-Light II, Hyper LII, LED Cure Master, Twinkle LED, and α-Light V). The light intensity of the devices was measured with a spectroradiometer. After light exposure, Knoop hardness number, flexural strength, and elastic modulus were determined. Evaluation of light intensity, using a wavelength range of 400 to 500 nm, revealed that the α-Light V and Hyper LII units had the highest light intensity. For the top surface of the two composites, the Knoop hardness number was significantly higher for the α-Light V and Hyper LII. For the two composite materials, flexural strength did not differ among the five polymerizing units. The present results indicate that the Cesead N and Solidex Hardura composites can be adequately polymerized with laboratory LED units.
关键词： microhardness,light source,light emitting diode,indirect composite,laboratory light polymerization
更新于2025-09-16 10:30:52
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Laser energy density dependence of performance in additive/subtractive hybrid manufacturing of 316L stainless steel
摘要： An enormous amount of research effort goes into the manufacturing process for additive manufacturing (AM) or subtractive manufacturing (SM) process for property microstructure. Moreover, additive/subtractive hybrid manufacturing (ASHM), which combines additive and subtractive processes in a single machine, has provided an important opportunity to increase the high percentage of stock utilization and produce complex functional components. However, the system comprehensive investigation and the study of ASHM-manufactured parts by various process parameters have rarely been reported. The present paper depicted the effect of laser energy density (ψ) on the phase change, density, microstructure, Vickers hardness, and tensile testing within the ASHM specimens. It was observed that the highest Vickers microhardness, the largest tensile strength, and the attendant ductility were gained at ψ =222 J/mm3, the most excellent value, which was put down to the high density and relatively fine grains. The results of this study have a better knowledge of the ASHM method to produce a high surface state and mechanical behavior 316L SS component by governing laser energy density (ψ).
关键词： Additive/subtractive hybrid manufacturing,Laser energy density,Microstructure,Densification,Vickers microhardness,Tensile properties
更新于2025-09-16 10:30:52