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Modelling the heating process of CFRP by cw-laser radiation with special focus on the heat transfer by thermal radiation between the carbon fibers
摘要： In our talk, we present results of numerical calculations that describe the thermal development within a laser-impacted laminate structure made of carbon layers embedded in a polymer matrix. The FEM-calculations show, that a significant part of the heat transfer is caused by radiative heat transfer between the carbon layers at elevated temperatures. In addition to the FEM calculations, we derive analytical relationships that allow the calculation of equivalent material parameters, especially an equivalent temperature-dependent, anisotropic thermal conduction coefficient. Thus, larger structures in the mm- and cm-range consisting of multiple carbon layers can be described by a simpler geometry of a homogenous material without the need to consider the individual carbon layers having a diameter of a few μm.
关键词： heat conduction,equivalent thermal conduction coefficient,inter fiber thermal radiation,CFRP composite,FEM-calculations
更新于2025-09-12 10:27:22
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Design of terahertz spectroscopy based optical sensor for chemical detection
摘要： In this article, a new design of circular cladding with a rotated-hexacore in photonic crystal fiber (RH-CPCF) has been suggested for chemical sensing application in the THz regime. The five layers circular cladding and two layers rotated-hexacore in circular shape are designed here. All numerical results are obtained with a procedure of finite element method and perfectly match layered boundary condition in terahertz (THz) wave propagation. After the simulation result, the proposed RH-CPCF shows the high relative sensitivity is 76.44%, 77.16% and 73.20% for three chemicals such as Ethanol (n = 1.354), Benzene (n = 1.366) and Water (n = 1.330) at 1 THz. On the other hand, the low confinement losses are 2.33 × 10?03 dB/m, 3.07 × 10?06 dB/m and 2.84 × 10?02 dB/m for same in three chemicals at 1 THz. Moreover, effective area, effective mode index and total power fraction in core air holes are also briefly described here. In addition, this proposed circular photonic crystal fiber (RH-CPCF) can be used especially for chemical sensing in biomedical, industrial quality control, material research, micro-optics and many communication applications in THz technology.
关键词： Terahertz sensor,Sensitivity,Optical loss profile,Photonic crystal fiber,Optical sensor,FEM based analysis
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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Distortion minimization of laser beam welded components by the use of finite element simulation and Artificial Intelligence
摘要： Welded components often require costly efforts to compensate for the thermally induced distortions. This is usually done by applying a specific pre-deformation or by reworking, for example by thermal straightening. These approaches are not practicable for joining complex structures. Therefore, a method that is capable of minimizing the distortions of a complex frame structure with multiple welds is presented. A meta-model by means of an Artificial Neural Network is used to predict the local distortions depending on the welding parameters within sub-areas. A genetic algorithm is utilized to efficiently find suitable welding parameters for the global structure. It could be shown that by applying the method, distortion minimized parameters from more than one billion potential parameter combinations are identified both efficiently and reliably.
关键词： Component distortions,Artificial Intelligence,Metamodeling,Genetic algorithms,FEM simulation,Artificial Neural Networks,Laser beam welding
更新于2025-09-12 10:27:22
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Residual stress and welding distortion of Al/steel butt joint by arc-assisted laser welding-brazing
摘要： The thermo-elastic?plastic finite element method (FEM) is used to simulate the thermo-mechanical behavior of Al/steel tungsten inert gas (TIG) arc-assisted laser welding-brazing (A-LWB) butt joint. The influence of material nonlinearity, geometrical nonlinearity and work hardening on the welding process is studied, and the differences in the welding temperature field, residual stress and welding distortion by A-LWB and by single laser welding-brazing (SLWB) are analyzed. The results show that the thermal cycle, residual stress distribution and welding distortion by the numerical simulation are in good agreement with the measured data by experiments, which verifies the effectiveness of FEM. Compared with the SLWB, A-LWB can make the high-temperature distribution zone of weld in width direction wider, decrease the transverse tensile stress in the weld and reduce the distribution range of longitudinal tensile stress. And the welding deformation also decreases to some extent.
关键词： arc-assisted laser welding-brazing (A-LWB),residual stress,welding distortion,Al/steel,temperature field,finite element method (FEM)
更新于2025-09-12 10:27:22
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Mechanical modeling and characterization of suspended cooled silicon bolometers for sub-millimeter and millimeter waves polarization detection
摘要： Silicon bolometers for space and astronomy applications, fabricated in standard CMOS-SOI technology are now successfully used as cryogenic detectors working at very low temperature, typically in the range of 0.05–0.1 K. They feature a remarkably high electromagnetic absorption, high temperature sensitivity and low noise. However, the mechanical behavior of suspended silicon bolometers results from the fabrication process parameters and a good understanding of these mechanisms is necessary to better control their deformation. In this work, silicon bolometer pixels with a pitch of 1200 μm and 500 μm for millimeter-wave (mm-wave) polarization detection have been fabricated and their mechanical behavior is investigated at room temperature and cryogenic temperature. First, a mechanical model was developed based on simulated and experimental deformations at room temperature of multi-layer cantilever test structures with different Young’s modulus and thickness (Ei, hi). The actual multi-layer suspended structures are modeled as an equivalent composite layer with an effective Young’s modulus (Eeff), an effective thickness (heff) and residual stresses (σ0, σ1). The residual stress values are positive, corresponding to a tensile stress in the fabricated multilayer stack. The impact of the a-Si passivation thickness on the total stress is discussed. The equivalent model is used in the simulation of the full pixel structure and results in excellent agreement with optical measurements of the deflection at room temperature. At cryogenic temperatures, mechanical deformations can hardly be measured, so the mechanical behavior of a 500-μm pixel was simulated at 0.1 K assuming that tensile residual stresses coming from defects are independent on temperature, and a good mechanical stability of the pixel was obtained. The optical performance simulation of this 500-μm pixel is discussed and showed that the mechanical deformations result in a degradation of the Noise Equivalent Power (NEP) from 1.59 × 10?18 to 1.05 × 10?17 W/Hz1/2 for an optical load of 6 × 10?15 W at 0.1 K.
关键词： Multilayer mechanical model,Cantilever,Doped silicon,FEM,Bolometer
更新于2025-09-11 14:15:04
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Laser-induced plume investigated by finite element modelling and scaling of particle entrainment in Laser Powder Bed Fusion (LPBF)
摘要： Although metal vaporisation has been observed in several laser processes such as drilling or welding, vapour plume expansion and its induced side effects are not fully understood. Especially, this phenomenon is garnering scientific and industrial interest since recent investigations in Laser Powder Bed Fusion (LPBF) have designated metal vaporisation as main source of denudation and powder spattering. The present study aims to provide a new insight on the dynamics of laser-induced vaporisation and to assess the potential of different gases for particle entrainment. A self-consistent finite element model of laser-induced keyhole and plume is thus presented for this purpose, built from a comprehensive literature review. The model is validated with dedicated experimental diagnostics, involving high-speed imaging to measure the ascent velocity of the vapour plume. The transient dynamics of vapour plume is thus quantified for different laser incident intensities and gas flow patterns such as the mushroom-like structure of the vapour plume are analysed. Finally, the model is used as a tool to quantify the entrainment flow expected in LPBF and an analytical model is derived to define a velocity threshold for particle entrainment, expressed in term of background gas properties. Doing so it is possible to predict how denudation evolves when the gaseous atmosphere is changed.
关键词： metal vapour plume,laser beam melting (LBM),high-speed imaging,finite element modelling (FEM)
更新于2025-09-11 14:15:04
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Evaluation of Assembly Gap from 3D Laser Measurements via FEA Simulation
摘要： This study evaluated the characteristics of temperature field distribution of the concrete box girder based on the middle bridge of Xiaosha River, and the effects of temperature in severely cold area were determined through experiments and finite element model (FEM) analysis. An FEM model of the concrete box girder considering the temperature field was established based on heat transfer theory to verify the accuracy of the model. Moreover, the calculation of the vertical temperature distribution and the temperature distribution along the web plate was conducted. The distribution along the through-thickness direction of the bottom plate and the temperature drop caused by cold waves was evaluated. Results suggest that the published codes and guidebooks were relevant. The effect of the most unfavorable condition of temperature load was also calculated. The result drawn from this research shows that the distribution of temperature field at the cross sections in the severely cold area differed greatly from that in the current code. However, the temperature difference in the top flange was not evident, whereas it was much larger in the bottom flange. The temperature in the web was higher than that in the top flange under solar radiation and was lower during cooling. The results of the temperature effect were much more critical than the result calculated using the vertical temperature gradient in the current code. The tensile stress produced by temperature load may cause cracks. Consequently, sufficient attention should be paid to the damage of thermal effects when calculating the concrete box girder in the northwest of the severely cold area.
关键词： concrete box girder,temperature effect,temperature field distribution,FEM,severely cold area,bridge engineering
更新于2025-09-11 14:15:04
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[IEEE 2018 3rd International Symposium on Instrumentation Systems, Circuits and Transducers (INSCIT) - Bento Gon?alves, Brazil (2018.8.27-2018.8.31)] 2018 3rd International Symposium on Instrumentation Systems, Circuits and Transducers (INSCIT) - Finite Element Modelling design and optimization of Love Wave mesoporous transducers for biochemical detection in liquid medium
摘要： We study numerically by a Finite Element Modeling (FEM) approach the design and the optimization of a Love wave transducer coated with a mesoporous sensitive layer. This association could allow to realize an easy functionalizable transducer for biochemical detection in liquid medium. The FEM approach is a good way to design the transducer by estimating many physical parameters in order to obtain a device which could work properly for a given application. Especially, by using a porous layer coated on an acoustic Love wave transducer, we need to be sure that the propagation parameters are still compatible with a usable device. In this paper, after a description of the reduced finite element model of the Love wave transducer, we show that the first experimental results are in a good agreement with the simulations. An “ultra-reduced” FEM approach of the Love wave transducer is carried out for easier consideration of the porous sensitive coating. Finally, experimental transducers are coated with TiO2 porous sensitive layers by the sol gel technique: the porosity is varied in the range from 10% to 25 %, the pore size from 10 nm to 200 nm, and the thickness from 100 nm to 500 nm. Simulated and experimental results are in good accordance, and allow us to conclude that such transducer could achieve a good propagation of the acoustic wave for biochemical sensing.
关键词： liquid medium,biochemical detection,SAW transducers,mesoporous layer,FEM simulation
更新于2025-09-11 14:15:04
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[IEEE 2018 EMF-Med 1st World Conference on Biomedical Applications of Electromagnetic Fields (EMF-Med) - Split, Croatia (2018.9.10-2018.9.13)] 2018 EMF-Med 1st World Conference on Biomedical Applications of Electromagnetic Fields (EMF-Med) - Modeling of Joule heating in tissues induced by high- and low-voltage pulse combinations for gene electrotransfer
摘要： Gene electrotransfer is a promising technique for safe and efficient gene therapy. It relies on locally delivered electric pulses to transfer previously injected foreign DNA into the cell. Applied pulses tissue (electroporation) and concomitant heat generation due to Joule effect. In our study we used finite element method to calculate electric field and temperature distribution during typical electrotransfer pulsing protocol (i.e. combination of 100 microsecond high-voltage pulse and 400 millisecond low-voltage pulse with pulse lag time of 1 second) in isotropic tissue (e.g. liver) and anisotropic tissue (e.g. skeletal muscle). For parallel plate electrodes results show negligible temperature rise in tissue bulk due to high voltage pulse and up to a few °C rise due to the low-voltage 400 ms-long pulse, depending on tissue conductivity.
关键词： COST EMF-MED,gene therapy,Joule heating,FEM,electric field,electroporation,gene electrotransfer
更新于2025-09-10 09:29:36