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[IEEE 2018 IEEE International Conference on Computational Electromagnetics (ICCEM) - Chengdu (2018.3.26-2018.3.28)] 2018 IEEE International Conference on Computational Electromagnetics (ICCEM) - Monostatic GTD Model for Double Scattering due to Specular Reflections or Edge Diffractions
摘要： GTD model is a good candidate to extract the features of radar targets, which describes the frequency dependence of scattering centers for many geometries or mechanisms and can represent the attribute information of the geometrical structures. The mechanisms associated with this model have been proven to include single reflection, single diffraction and multiple reflections from dihedral and trihedral corner reflectors. However, multi-scattering mechanisms from more complex structures are not studied adequately. In this paper, we expand the GTD model to any double scattering due to specular reflections or edge diffractions, and derive the related frequency-dependence factor. Finally, a simulation validates the theory.
关键词： specular reflection,multiple scattering mechanism,frequency-dependence factor,flat surface,straight edge,doubly-curved surface,GTD model,curved edge,edge diffraction,singly-curved surface
更新于2025-09-23 15:22:29
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Optical properties of diamond-like carbon films prepared by pulsed laser deposition onto 3D surface substrate
摘要： It is difficult to grow uniform film by pulsed laser deposition because the spatial distribution of the laser-induced plume is a forward-directed cone-shape. A 3D-motional deposition setup was founded, and the correlative mathematical model of the film thickness on the 3D curved surface was deduced. Based on simulation and optimization, the diamond-like carbon (DLC) film was grown onto the large curved silicon substrate. According to the infrared transmittance spectra, the optical constants of the DLC film samples at different regions on the curved substrate were similar, indicating that the DLC film prepared onto the curved surface was homogeneous. Meanwhile, the deviation of average transmittance in the medium infrared band was below 2.3%, which could improve the imaging performance of the infrared detection. This research is useful to expand the application of the pulsed laser deposition in the optical field.
关键词： uniform transmittance,Raman spectroscopy,3D curved surface,Pulsed laser deposition,DLC film,infrared spectrum
更新于2025-09-23 15:21:01
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Surface based variable thickness slicing modeling for laser metal deposition
摘要： Laser metal deposition (LMD) has been a promising additive manufacturing technology widely used in mold rapid manufacturing. In order to improve the capacity of LMD for complex curved surface structures, a surface based variable thickness slicing (S-VTS) model is proposed to adaptively generate the LMD process based on the geometric characteristics of structures. Two deposition strategies in scanning and overlapping directions are designed to enable variable thickness of each cladding layer by dynamically adjusting the scanning speed and overlapping rate. To improve the surface quality and forming efficiency, the discrete particle swarm optimization (DPSO) algorithm is adopt to optimize the process parameters of S-VTS model, including the number of cladding layer, scanning pass, and segment per pass. Several experiments are conducted to form the cuboid samples with wavy and freeform surface and verify the feasibility of the S-VTS model. The results demonstrate that under the open-loop control condition, the geometric accuracy, surface quality, and efficiency of the proposed method is improved in comparison with uniform thickness slicing (UTS) deposition. Moreover, heterogeneous microstructure is always generated by the S-VTS method in terms of grain size and growth direction.
关键词： Variable thickness slicing (S-VTS),Laser metal deposition (LMD),Curved surface,Mold
更新于2025-09-23 15:19:57
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Control and prediction of forming quality in curved surface multi-track laser cladding with curve paths
摘要： This research investigated the influence of different processing parameters in curved surface multi-track laser cladding with curve paths. Mathematical models of flatness ratio, incomplete fusion, and pore area in the clad were developed by central composite design with altering the input laser power, scanning speed, gas flow, and overlapping rate. Response surface methodology was used to analyze the correlation of different processing parameters affecting the selected responses. A clad with better flatness ratio was achieved by properly increasing the laser power and gas flow while reducing the overlapping rate. Appropriately increasing the laser power and overlapping rate while reducing the scanning speed and gas flow effectively diminished the incomplete fusion. Less pore area in the clad was obtained by appropriately increasing the laser power and overlapping rate while reducing the scanning speed and gas flow. Afterwards, desired processing parameters set was obtained by the optimization with the target of maximizing the flatness ratio and also minimizing the incomplete fusion and pore area. Experimental validation with this processing parameter setup provided satisfactory clad, and the error rate for the flatness ratio, incomplete fusion, and pore area was 1.708%, 5.714%, and 6.522%, respectively. This paper provides the theoretical guidance for the prediction and control of the flatness ratio, incomplete fusion, and pore area in curved surface multi-track laser cladding with curve paths.
关键词： Central composite design,Response surface methodology,Curved surface,Laser cladding
更新于2025-09-19 17:13:59
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Investigation of Geometric Characteristics in Curved Surface Laser Cladding with Curve Path
摘要： Laser cladding on curved surfaces is essential in industrial applications for restoration and remanufacturing of high-value parts. This study investigated the in?uence of di?erent factors on clad width, clad height, and dilution rate in curved surface laser cladding with curved path. Mathematical models were developed using central composite designs to predict these geometric characteristics by controlling laser power, scanning speed, gas ?ow, and altering the outside radius of the cylindrical substrate. Analysis of variance and response surface methodology indicated that clad width increased with increasing laser power and reducing scanning speed. Clad height positively correlated to laser power and negatively correlated to the outside radius of the cylindrical substrate. Increasing the laser power while decreasing the scanning speed led to an increase in dilution rate. Afterwards, the geometric characteristics of the clad were improved by optimizing these factors with the target to maximize clad width and height as well as to minimize dilution rate. The di?erence between model predictions and experimental validations for clad width, clad height, and dilution rate were 3.485%, 3.863%, and 6.566%, respectively. The predicted accuracy was veri?ed with these models, and they were able to provide theoretical guidance to predict and control the geometric characteristics of curved surface laser cladding with a curved path.
关键词： central composite design,curved surface,forming control,curve path,laser cladding
更新于2025-09-16 10:30:52
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Ellipsometry - Principles and Techniques for Materials Characterization || The Development of Three-Intensity Measurement in PSA Ellipsometry and Photoelastic Modulation Ellipsometry
摘要： A three-intensity measurement technique in a polarizer-sample-analyzer (PSA) ellipsometry will be introduced. The alignment of the azimuth angle of polarizer and analyzer to the incident plane will be discussed. Its applications to measure the ellipsometric parameters for deducing the optical parameters will be stated. In addition to the PSA ellipsometry, one can insert a photoelastic modulator (PEM) in the PSA ellipsometry for developing a PEM ellipsometry. There is no moving part in the system and its measuring speed is only limited by a modulator. An in situ/real-time and post-flight ellipsometry can be established for monitoring the dynamically varying process.
关键词： real time,curved surface,alignment,calibrations
更新于2025-09-09 09:28:46