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Residual Stress Modelling and Experimental Analyses of Ti6Al4V ELI Additive Manufactured by Laser Engineered Net Shaping
摘要： This paper focus on the experimental analyses and modelling of the residual stresses build up during laser additive manufacturing by Laser Engineered Net Shaping. Currently, additive manufactured parts employ heat treatment for the reduction of internal stresses, but then additional advantages are also possible from heat treatment. The experimental analyses focus on stress relieving heat treatment temperatures to reduce the residual stresses during laser processing of LENS Ti6Al4V ELI specimens. LENS parts out of Ti6Al4V ELI will illustrate the mechanical property possibilities resulting from the selected stress relieving heat treatments in this study. The primary aim of heat treatment in this case of Ti6Al4V ELI is the reduction of internal stresses. Due to the mechanical behaviour of Ti6Al4V as built additive manufactured parts, the heat treatment seems to be necessary to increase the mechanical behaviour, such as the fatigue performance and the breaking elongation. Optical Microscope, Scanning Electron Microscope and Vickers hardness test was employed to carry out detailed study of the resulting microstructures and Hardness. The model by COMSOL Multiphysics was employed to predict the residual stresses of as built LENS Ti6Al4V ELI and to better understand the residual stresses amounts in the Ti6Al4V ELI alloy that need to be minimized by heat stress relieving heat treatment methods. The results included the β-phase that formed in the stress relieving heat treatment process that was transformed to martensite α during the cooling process and a fine basket-weave structure emerged. The microhardness of LENS Ti6Al4V ELI alloy gradually decreased with increasing stress relieving heat treatment temperature. The computed model revealed the maximum stress of 1.78x109 MPa, the Model strongly recommended the LENS process parameters suitable to obtain Ti6Al4V ELI samples with minimal residual stresses and a further possible method to alleviate the attained residual stresses in the model to the desired elasticity.
关键词： Modelling,Additive manufacturing,Residual stresses,Heat treatment,Microstructure evolution,Laser Engineered Net Shaping (LENS)
更新于2025-09-12 10:27:22
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[IEEE 2019 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD) - Ottawa, ON, Canada (2019.7.8-2019.7.12)] 2019 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD) - Alternative approach to optimizing optical spacer layer thickness in solar cell using evolutionary algorithm
摘要： This work is inspired by Darwin's biological evolution theory: natural selection. We propose to use genetic evolutionary algorithm to optimize the search for the optimal thickness in solar cells with regards to maximizing short-circuit current density. Optical spacer layer thickness need to be optimized in order to achieve maximum absorption of the incoming light by the solar cell. In order to obtain the best optical spacer thickness, we perform multiple simulations with different number of population, number of generations, mutation probability, number of bits, and selection and crossover methods. Our preliminary experiments show that the introduction of evolutionary algorithm result in a satisfactorily accurate search method when compared to brute-force. The future works on utilizing the full ability of evolutionary algorithm will be presented at the conference.
关键词： finite difference time domain,evolutionary algorithm,organic solar cell,optical modelling
更新于2025-09-12 10:27:22
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Extrinsic calibration and kinematic modelling of a laser line triangulation sensor integrated in an intelligent fixture with 3 degrees of freedom
摘要： This article presents the kinematic modelling for the extrinsic calibration of a laser line profile sensor integrated in an intelligent fixture. It aims to characterize the real 3D shape of flexible parts when they are clamped to ensure suitable stiffness for machining processes, aiding to define the machining path to improve the precision of the process. This tool consists of two linear axes and a rotary axis (3 DOF) which enables scanning the area of the part to be processed automatically. In order to carry out the accuracy evaluation of the intelligent fixture, some methods present in the state of the art have been considered and compared. Moreover, in order to design and identify the most suitable calibration procedure a previous simulation process is carried out based on sensitivity analysis. To complete the study, a test piece has been scanned with the intelligent fixture and compared with an external metrological frame employed as a ground truth. In addition, a characterization of the geometric performance of the fixture's linear actuators is carried out to check the geometric performance and its influence on the extrinsic calibration process accuracy. The results of this article show the importance of performing simulation processes in order to define the best measurement scenario for extrinsic calibration. Besides, it demonstrates the influence of the method used to perform extrinsic calibration in order to obtain good precision in the measures, where the geometric performance of the drives have a decisive influence.
关键词： Point cloud processing,Kinematic modelling,Kinematic calibration,Inverse problem,Triangulation sensor
更新于2025-09-12 10:27:22
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Fabrication and performance of AC-coupled LGADs
摘要： Detectors that can simultaneously provide ?ne time and spatial resolution have attracted wide-spread interest for applications in several ?elds such as high-energy and nuclear physics as well as in low-energy electron detection, photon science, photonics and imaging. Low-Gain Avalanche Diodes (LGADs), being fabricated on thin silicon substrates and featuring a charge gain of up to 100, exhibit excellent timing performance. Since pads much larger than the substrate thickness are necessary to achieve a spatially uniform multiplication, a ?ne pad pixelation is di?cult. To overcome this limitation, the AC-coupled LGAD approach was introduced. In this type of device, metal electrodes are placed over an insulator at a ?ne pitch, and signals are capacitively induced on these electrodes. At Brookhaven National Laboratory, we have designed and fabricated prototypes of AC-coupled LGAD sensors. The performance of small test structures with di?erent particle beams from radioactive sources are shown.
关键词： Charge transport and multiplication in solid media,Detector modelling and simulations II (electric ?elds, charge transport, multiplication and induction, pulse formation, electron emission, etc),Solid state detectors,Timing detectors
更新于2025-09-12 10:27:22
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AIP Conference Proceedings [AIP Publishing INTERNATIONAL SYMPOSIUM ON GREEN AND SUSTAINABLE TECHNOLOGY (ISGST2019) - Perak, Malaysia (23–26 April 2019)] INTERNATIONAL SYMPOSIUM ON GREEN AND SUSTAINABLE TECHNOLOGY (ISGST2019) - FEM simulation of deformations in strings of shingled solar cells subjected to mechanical reliability testing
摘要： Among several emerging interconnection technologies, shingled solar cell interconnection is the technology to realize highest power densities in solar modules. Its main feature is the replacement of ribbon stringing with direct interconnection by a slight overlapping of the solar cells using electrically conductive adhesives (ECA) as joint material. To succeed in a highly competitive market, this type of interconnection still has to prove its reliability, which requires a sound understanding of the loads this ECA joint faces during module lifetime. This study applies structural mechanic simulations based on the Finite Element Method (FEM) to investigate the impact of external loads according to IEC 61215 on a string of shingled solar cells within a solar module laminate. Linear elasticity is compared to the more realistic viscoelastic modelling of the encapsulant (EVA) and the ECA with the objective of reducing computational effort, which is caused by viscoelasticity. We found that linear elasticity can be applied in comparative studies to investigate the potential of different geometric designs to reduce mechanical stress in the joint. When it comes to the calculation of absolute values for stress and strain the strong viscoelastic properties of EVA and ECA cannot be neglected.
关键词： viscoelastic modelling,shingled solar cells,mechanical reliability testing,ECA joint,FEM simulation
更新于2025-09-12 10:27:22
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The role of photovoltaics in a sustainable European energy system under variable CO <sub/>2</sub> emissions targets, transmission capacities, and costs assumptions
摘要： PyPSA-Eur-Sec-30 is an open-source, hourly resolved, networked model of the European energy system that includes one node per country as well as electricity, heating, and transport sectors. The capacity and dispatch of generation and storage technologies in every country can be cost optimized under different CO2 emissions constraints. This paper presents an overview of the most relevant results previously obtained with the model, highlighting the influence of solar photovoltaic (PV) generation on them. For 95% CO2 emissions reduction, relative to 1990 level, PV generation supplies in average 33% of the electricity demand. Southern European countries install large PV capacities together with electric batteries, while northern countries install onshore and offshore wind capacities and use hydrogen storage and reinforced interconnections to deal with wind fluctuations. The strong daily generation profile of solar PV heavily impacts the dispatch time series of backup generation and storage technologies. The optimal PV and wind capacities are investigated for variable CO2 emissions, transmission interconnection among neighbouring countries, and cost assumptions.
关键词： energy system modelling,CO2 emissions targets,sector coupling,storage,grid integration,transmission grid
更新于2025-09-12 10:27:22
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Modelling of a Multipurpose Photovoltaic Generator Block Using ATP-EMTP
摘要： One of the major references to deal with electromagnetic transients is the ATP-EMTP program whose associated tools, ATPDraw (a graphical interface) and MODELS (a programmable language), have pushed its use to other electrical system analysis. In this context, this article aims to show the development of a computational block to represent the photovoltaic generator in ATP, with its respective mask and configuration in ATPDraw. Starting from the classical mathematical foundation, a photovoltaic module is developed from data available in manufacturers’ manuals. The ideality equations are then modified to attend different purposes: applying new values of temperature and irradiation, choosing series and/or parallel association of modules, including different values of series and parallel resistances. The final multipurpose photovoltaic generator is validated by comparison of its results with those found in the related technical literature.
关键词： Photovoltaic module,MODELS,Modelling,ATPDraw,ATP-EMTP
更新于2025-09-11 14:15:04
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Stress-induced refractive index changes in laser fibers and preforms
摘要： Refractive index profile of the core is a key design parameter in fiber lasers and amplifiers. During manufacturing, the initial information of the index profile is obtained from the preform, while ultimately the performance is defined by the index profile of the fiber. Depending on stresses and diffusion, the two profiles may be different. It is possible to predict more accurately the laser fiber refractive index when we apply a stress-induced index change model to the measured preform index profile data. The improved capability to predict the fiber index from preform increases the confidence in achieving the designed index profile in fiber, which enables faster process feedback and higher fiber yields.
关键词： laser fiber,tension,optical fiber,modelling,thermal stress,preform,Refractive index change,DND,stress
更新于2025-09-11 14:15:04
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Structural 3D Reconstruction of Indoor Space for 5G Signal Simulation with Mobile Laser Scanning Point Clouds
摘要： 3D modelling of indoor environment is essential in smart city applications such as building information modelling (BIM), spatial location application, energy consumption estimation, and signal simulation, etc. Fast and stable reconstruction of 3D models from point clouds has already attracted considerable research interest. However, in the complex indoor environment, automated reconstruction of detailed 3D models still remains a serious challenge. To address these issues, this paper presents a novel method that couples linear structures with three-dimensional geometric surfaces to automatically reconstruct 3D models using point cloud data from mobile laser scanning. In our proposed approach, a fully automatic room segmentation is performed on the unstructured point clouds via multi-label graph cuts with semantic constraints, which can overcome the over-segmentation in the long corridor. Then, the horizontal slices of point clouds with individual room are projected onto the plane to form a binary image, which is followed by line extraction and regularization to generate ?oorplan lines. The 3D structured models are reconstructed by multi-label graph cuts, which is designed to combine segmented room, line and surface elements as semantic constraints. Finally, this paper proposed a novel application that 5G signal simulation based on the output structural model to aim at determining the optimal location of 5G small base station in a large-scale indoor scene for the future. Four datasets collected using handheld and backpack laser scanning systems in di?erent locations were used to evaluate the proposed method. The results indicate our proposed methodology provides an accurate and e?cient reconstruction of detailed structured models from complex indoor scenes.
关键词： mobile laser scanning,point clouds,5G signal simulation,3D reconstruction,indoor modelling
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Computational Modelling of Metasurfaces for Strongly Divergent Beams
摘要： The content of the paper discusses the computational modelling of metasurfaces for strongly divergent beams, focusing on the design and application of metasurfaces with building blocks that can efficiently control light beams with high divergence. It highlights the potential of these metasurfaces in various applications, including optical tweezers, laser beam shaping, and imaging systems. The paper also explores the challenges and limitations in designing such metasurfaces, particularly in achieving high efficiency over a broad range of angles and wavelengths.
关键词： imaging systems,computational modelling,metasurfaces,optical tweezers,divergent beams,laser beam shaping
更新于2025-09-11 14:15:04