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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) - Curve Correction of the Energy Yield by Flexible Photovoltaics for VIPV and BIPV Applications Using a Simple Correction Factor
摘要： High-power grinding mills are used in the cement and mining industries to crush clinker or copper ore and grind these materials to fine powder. The multi-megawatt speed-controlled mill drives operate at a very low angular speed. Synchronous motors with a high number of pole pairs are used as the prime movers. They are traditionally fed by load-commutated thyristorized cycloconverters. These are prone to failure modes that can lead to excessive torque pulsations and high overcurrents. The huge stator, which was built as a separate ring-shaped structure around the tubular mill, may then get mechanically displaced, and the operation of the plant is interrupted. A novel and reliable direct drive uses a voltage source inverter that operates at the unity power factor for increased efficiency. Synchronous optimal pulsewidth modulation ensures a low harmonic current distortion and reduced switching losses at a very low switching frequency. The optimization of the pulse patterns takes the anisotropic magnetic properties of a separately excited synchronous motor into account. The implementation in a 23-MW semiautonomous grinding mill installed in a Zambian copper mine is intended.
关键词： Alternators,ball milling,pulse width modulation inverters,gradient methods,software algorithms,variable speed drives,Fourier transform
更新于2025-09-19 17:13:59
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Research and Optimization of Surface Roughness in Milling of SLM Semi-Finished Parts Manufactured by Using the Different Laser Scanning Speed
摘要： The paper studies the potential to improve the surface roughness in parts manufactured in the Selective Laser Melting (SLM) process by using additional milling. The studied process was machining of samples made of the AlSi10Mg alloy powder. The simultaneous impacts of the laser scanning speed of the SLM process and the machining parameters of the milling process (such as the feed rate and milling width) on the surface roughness were analyzed. A mathematical model was created as a basis for optimizing the parameters of the studied processes and for selecting the sets of optimum solutions. As a result of the research, surface with low roughness (Ra = 0.14 μm, Rz = 1.1 μm) was obtained after the face milling. The performed milling allowed to reduce more than 20-fold the roughness of the SLM sample surfaces. The feed rate and the cutting width increase resulted in the surface roughness deterioration. Some milled surfaces were damaged by the chip adjoining to the rake face of the cutting tool back tooth.
关键词： face milling,surface roughness,AlSi10Mg,SLM
更新于2025-09-16 10:30:52
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Effects of Preheating Temperature at Primary Shear Zone in Laser Assisted Milling Process
摘要： In this paper, preheating temperature was investigated for the laser assisted machining (LAM) of Inconel 718 under different conditions for the milling test. The experimental results show that the requirement of laser power for the particularly preheating temperature proportionally increased with the table speed. The resultant cutting force for sufficient shearing work material in LAM was lower than conventional machining (CM) approximately 11, 21 and 28% for the cutting speed of 30, 50 and 75 m/min, respectively. The tool wear in LAM could be improved at relatively high cutting speed of 75 m/min and the hardness of machined surface in LAM was slightly higher than CM.
关键词： Laser assisted machining,Milling,Inconel 718,Preheating temperature
更新于2025-09-16 10:30:52
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Machinability of titanium alloy through laser machining: material removal and surface roughness analysis
摘要： Laser milling is a competent precision process especially when the work material is hard-to-machine such as titanium alloys. While performing the laser milling, a slight change in one of the laser parameters results in an abrupt change in the machining outcomes. A close match between the designed and the machined geometries is the essence of precision machining. A precise control over the material removal rate per laser scan is highly desirable but difficult to achieve. The difficulty level becomes higher if high surface finish is desired alongside the precision machining. In this research, the objective was set to perform the laser milling on titanium alloy (Ti-6Al-4V) with 100% control over material removal rate (MRR) per laser scan and minimum surface roughness (SR). Influence of the five laser parameters (laser intensity, pulse frequency, scan speed, layer thickness, and track displacement) on MRR and SR has been deeply investigated. Significance of each laser parameter is evaluated through ANOVA. Mathematical models for both the responses are developed to estimate the resulting responses at any parametric setting. Models have also been validated through confirmatory tests. Optimization of laser parameters is of great importance to remove the material exactly equal to the desired depth with minimum surface roughness. Therefore, the optimized combinations of laser parameters have been proposed which ensure the conformance of 100% MRR and minimum surface roughness with composite desirability > 0.9. Confirmatory experiments revealed that the optimized parameters are capable to produce the laser milling results as per the models’ predicted results. Additionally, the microstructure of the subsequent layers below the milled area has also been examined and compared with the microstructure of the bulk Ti-6Al-4V. By the use of optimized parameters, microstructure of the sub-layers remains unchanged as compared with the microstructure of the base metal. No evidence has been found altering the microstructure of the sub-layers.
关键词： Laser milling,Titanium alloy,Mathematical model,Surface roughness (SR),Optimization,Material removal rate (MRR)
更新于2025-09-16 10:30:52
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Inverse analysis of the residual stress in laser-assisted milling
摘要： In laser-assisted milling, higher temperature in shear zone softens the material potentially resulting in a shift of mean residual stress, which significantly affects the damage tolerance and fatigue performance of product. In order to guide the selection of laser and cutting parameters based on the preferred mean residual stress, inverse analysis is conducted by predicting residual stress based on guessed process parameters, which is defined as the forward problem, and applying iterative gradient search to find process parameters for next iteration, which is defined as the inverse problem. An analytical inverse analysis is therefore proposed for the mean residual stress in laser-assisted milling. The forward problem is solved by analytical prediction of mean residual stress after laser-assisted milling. The residual stress profile is predicted through the calculation of thermal stress, by treating laser beam as heat source, and plastic stress by first assuming pure elastic stress in loading process, then obtaining true stress with kinematic hardening followed by the stress relaxation. The variance-based recursive method is applied to solve inverse problem by updating process parameters to match the measured mean residual stress. Three cutting parameters including depth of cut, feed per tooth, and cutting speed, and two laser parameters including laser-tool distance and laser power, are updated with respected to the minimization of resulting residual stress and measurement in each iteration. Experimental measurements are referred on the laser-assisted milling of Ti–6Al–4 V and Si3N4. The percentage difference between experiments and predictions is less than 5% for both materials, and the selection is completed within 50 loops.
关键词： Residual stress,Ti–6Al–4V,Si3N4,Laser-assisted milling,Inverse analysis,Iterative gradient search
更新于2025-09-16 10:30:52
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Effect of laser texturing on the performance of ultra-hard single-point cutting tools
摘要： This paper investigates the cutting performance and anti-adhesive properties of textured single-point polycrystalline diamond (PCD) cutting tools in machining Aluminium 6082 alloys. The micro/nano textures were first milled using a fibre laser (1064-nm wavelength) at different power intensities, feed speeds and pulse durations, and finally characterised using scanning electron microscopy, white light interferometry and energy dispersive X-ray spectroscopy. The effect of different textures on the cutting performance was investigated in turning tests under dry cutting conditions. The test was stopped at regular lengths of cut to allow analysis of height of adhesion through 3D white light interferometry. The data processing of the cutting forces and the microscopical characterisation of the tested cutting tools enabled the evaluation of the effects of texture design, friction coefficient and adhesive properties. The results indicated that feed force in tools with grooves perpendicular to the chip flow direction (CFD) was more stable (20–40 N) than the benchmark (6–41 N). Similarly, the thrust force for tools with grooves parallel to CFD and grooves perpendicular to CFD showed a homogeneous trend fluctuating between 60 and 75 N as compared with the benchmark (ranging between 73 and 90 N). For texture depth in the order of 260 nm and post process roughness in the order of tens of nanometers, a reduction of average friction coefficient (0.28 ± 0.14) was reported when using lasered inserts with grooves parallel to the chip flow direction compared with the benchmark tools (0.34 ± 0.26) corroborated by reduced stiction of workpiece material on the rake face. In machining via textured tools with grooves perpendicular to CFD, the cutting forces were reduced by 23%, and the surface quality of the machined workpiece was improved by 11.8%, making this geometry the preferred choice for finishing applications. Using grooves parallel to CFD reduced the cutting forces by 11.76%, adhesion by 59.36% and friction coefficient by 14.28%; however, it increased the surface roughness of the machined workpiece, making this geometry suitable for roughing operations. For the first time, laser manufacturing is proposed as a flexible technique to functionalise the geometrical and wear properties of PCD cutting tools to the specific applications (i.e. roughing, finishing) as opposed to the standard industrial approach to use microstructurally different PCDs (i.e. grain size and binder %) based on the type of operation.
关键词： Adhesion,Dry cutting,Nanosecond pulse,Laser milling,Polycrystalline diamond insert,Laser surface texturing,Cutting forces
更新于2025-09-16 10:30:52
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Study on laser-induced oxidation modification coupled with micro milling of WC-Co cemented carbide
摘要： Cemented carbide is known as “industrial tooth” and has wide applications in terms of military, aerospace and other fields. In this study, a compound processing approach named laser-induced oxidation modification coupled with micro milling (LCMM) is proposed to solve its poor micro machining performance. The oxidation mechanism of WC-Co cemented carbide is revealed. Surface morphology and cross-section of WC-Co cemented carbide are investigated after laser irradiation under various average laser power and two reaction environment. Research results present that at the average power of 5 W, scanning speed of 0.5 mm/s and oxygen-rich oxygen condition, the laser-induced oxidation process is optimal. The thickness of oxide layer and sub-layer is 9.1 μm and 2.7 μm, and the material surface generates porous and loose oxide layer. In addition, comparative analyses are performed and discussed in detail considering milling force, tool wear and surface quality of machined micro slot. In comparison with conventional micro milling (CONM), cutting force of Fx and thrust force of Fy generated in removing the oxide layer in LCMM are reduced by 56% and 58% to maximum extent, respectively. The machined surface quality in LCMM is better than that in CONM with a slower rate of increase in surface roughness (Sa). At ap = 2 μm and fz = 1.5 μm/z, surface quality of machined micro slot in LCMM is superior to that at other milling parameters, and the surface roughness reach 57 nm. Tool wear rate in LCMM is greatly improved and tool wear mechanism mainly includes slight adhesion wear and abrasion wear. While, in CONM the wear mechanisms are severe abrasion wear, chipping and adhesion wear. The tool service life in LCMM can be promoted more than double.
关键词： Micro milling,Surface quality,Cemented carbide,Laser-induced oxidation,Tool wear
更新于2025-09-16 10:30:52
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Evaluation of internal defects generated in machine milled carbon fiber reinforced plastic using X-ray computed tomography
摘要： In this study, X-ray computed tomography (X-ray CT) was used to investigate internal defects generated on machine milled carbon fiber reinforced plastics (CFRP). Internal defects such as cracks, fractures, and deformation of the carbon fibers, which are invisible from the surface, were observed using the X-ray CT method. Defects were generated based on the machining method and direction of the fibers. A large number of defects were generated when using the conventional cut method along 45°, 90°, and the climb cut method along 90°. Few internal defects were observed when using the climb cut method along 45°; however, the machined surface was very rough. The mechanism for these phenomena was investigated by studying surface observations and cutting force, in addition to X-ray CT imaging. These results indicate that X-ray CT is a powerful tool for visualizing internal defects in CFRP, which differ significantly based on the direction of the fiber and machining method used.
关键词： Carbon fiber reinforced plastics,Surface roughness,Milling,Internal defect,X-ray computed tomography
更新于2025-09-16 10:30:52
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Nano-Scaled Lanthanum Hexaboride (LaB6) – Control of Properties in Dependence on Type of Manufacturing
摘要： This paper presents the influence of fabrication methods on the optical and photo-thermal properties of nano-LaB6. The nano particles (NPs) were manufactured via continuously operated ball milling or induction plasma technology. Whereas different grinding processes for LaB6 were also discussed using ethylene glycol (EG) and ZrO2 grinding media in previous works, the scaled-up plasma technology presents a new possibility to gain NPs with high yields and narrow size distribution. In our work, NPs < 100 nm are achieved by grinding experiments using ethanol, 1-methoxy-2-propanol and ethylene glycol. Furthermore, the change of grinding parameters was investigated intensively. Compared to milled NPs, nano-LaB6 in high purity are gained by plasma technology and shows differences in color, morphology (UHR-FESEM), absorption behavior and crystallite size (X-Ray). Acrylate terminated starPEG (poly ethylene glycol) was used as a high cross-linked network after in-situ UV polymerization to stabilize NPs homogenously. We also set the focus on photo-thermal conversion properties of LaB6 dispersions in ethylene glycol, i.e. transformation of the absorbed photon energy into heat, and temperature distribution around the laser spot which are characterized by an IR camera.
关键词： photo-thermal conversion,top-down,ball milling LaB6,LaB6 nano particles,SPR,plasma LaB6,LaB6 stabilization
更新于2025-09-16 10:30:52
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A Finite Element Model for Temperature Prediction in Laser-Assisted Milling of AerMet100 Steel
摘要： Laser-assisted milling (LAM) represents an innovative process to enhance productivity in comparison with conventional milling. The workpiece temperature in LAM not only affects the cutting performance of materials, but also the machined surface quality of the part. This paper presents a 3D transient finite element (FE) model for workpiece temperature prediction in LAM. A moving Gaussian laser heat source model is implemented as a user-defined subroutine and linked to ABAQUS. The thermal model is validated by machining AerMet100 steel under different process parameters (laser power, spindle speed and feed per tooth). Good agreement between predicted and measured workpiece temperatures indicates that the FE model is feasible. In addition, the effects of laser spot size and incident angle on workpiece temperature are analyzed based on the proposed model. This work can be further applied to optimize process parameters for controlling the machined surface quality in LAM.
关键词： workpiece temperature,AerMet100 steel,finite element model,laser-assisted milling
更新于2025-09-16 10:30:52