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Development of an Intra-Layer Adaptive Toolpath Generation Control Procedure in the Laser Metal Wire Deposition Process
摘要： Recently developed concentric laser metal wire deposition (LMWD) heads allow metal addition processes which are independent of the deposition direction, thus enabling complex paths to be generated. The sensitivity of the process to height deviations has experimentally been observed to be greater with this type of head than with powder ones, therefore requiring more precise and local process control algorithms to be implemented. This work developed a methodology for measuring the part, layer by layer, using a 3D scanner based on structured laser light. Height corrections were applied to the mean and intra-layer height deviations by recalculating the deposition trajectories of the next layer to be deposited. Local height deviations were adjusted by varying the scanning speed, thus increasing the feed rate in the lower areas and decreasing it in the higher ones. Defects generated in the purpose, with height differences within the layer, were successfully corrected. A flat layer was re-established through the application of the control strategy. The internal integrity of the parts due to the scanning speed variation was analyzed, resulting in fully dense parts. The structured light measurement and height correction systems are found to be an affordable and time-efficient solution that can be integrated into an LMWD environment, thereby improving the process robustness.
关键词： cladding,coaxial wire feed,metal wire,additive manufacturing,monitoring,laser deposition,structured light scanning,height control
更新于2025-11-28 14:24:20
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Characteristics of multi-pass narrow-gap laser welding of D406A ultra-high strength steel
摘要： A universal and applicable method to predict bonding quality in narrow-gap laser beam filler wire welding of D406A ultra-high strength steel was presented. Defect-free joint could be achieved under the predicted optimal welding condition, while the production efficiency of narrow-gap laser beam filler wire welding under optimized welding condition was about 3.75 times that of traditional tungsten arc welding currently used in practical industry. Compared with the tungsten arc welding joint, microstructure in the fusion zone of laser welded joint was more uniform, which brought out a less fluctuation in the microhardness of fusion zone along the thickness direction. The tensile strength of as-welded laser welding joint was slightly higher than that of as-welded tungsten arc welding joint while the elongation of the former increased by 15.9% over that of the latter. A binocular stereo three-dimensional scanning method was adopted to compare the residual distortion of D406A joints between laser welding and tungsten arc welding. Notably, the distortion of laser welded joint was about 21% of that of the tungsten arc welding joint. Narrow-gap laser filler wire welding is a feasible substitute for conventional tungsten arc welding in the fabrication of welded construction of D406A steel.
关键词： ultra-high strength steel,welding distortion,filler wire,narrow-gap laser beam welding,microstructure
更新于2025-11-28 14:24:20
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Microstructural Characteristics of Laser Metal Deposited Magnesium Alloy AZ31
摘要： Up to now, only a limited amount of metallic materials is investigated for laser additive manufacturing (LAM). However, the demand to widen the application possibilities by enlarging the range of materials for LAM is growing fast. By now, titanium and aluminium alloys are in the focus of research. In contrast, magnesium alloys are rarely used in the field of additive manufacturing, although they possess a low density in combination with a high specific strength. Currently, magnesium structures are mainly produced by casting but during the last years, the use of wrought alloys also increased. A reason for the rare use of magnesium alloys for LAM technologies might be the high flammability of magnesium powders. This difficulty can be avoided by using magnesium wire for laser metal deposition (LMD). In the present study, the microstructural characteristics of a LMD processed AZ31 magnesium alloy are investigated. For this purpose, optical microscopy and scanning electron microscopy were used. With the help of EDX and EBSD analysis, a change of the chemical composition and micro texture with structure height was identified. The relationship of microstructure and local mechanical properties was investigated with the help of Vickers micro hardness testing. Based on the obtained results it can be concluded that the microstructural characteristics of laser additive manufactured magnesium alloys differ from those of titanium and aluminium alloys. Thus, a wider application spectrum of LMD and magnesium alloys can be opened up.
关键词： laser metal deposition,local mechanical properties,microstructure,magnesium alloy,wire,microtexture
更新于2025-11-28 14:24:20
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Young’s Modulus Measurement of Metal Wires Using FBG Sensor
摘要： A novel Young’s modulus measurement scheme based on fiber Bragg gratings (FBG) is proposed and demonstrated experimentally. In our method, a universal formula relating the Bragg wavelength shift to Young’s modulus is derived and metal wires are loaded strain by using the static stretching method. The Young’s modulus of copper wires, aluminum wires, nickel wires, and tungsten wires are separately measured. Experimental results show that the FBG sensor exhibits high measurement accuracy, and the measurement errors relative to the nominal value is less than 1.0%. The feasibility of the FBG test method is confirmed by comparing it with the traditional charge coupled device (CCD) imaging method. The proposed method could find the potential application in the material selection, especially in the field that the size of metal wires is very small and the strain gauges cannot be qualified.
关键词： Young’s modulus,static stretching method,metal wire,Fiber Bragg grating
更新于2025-11-28 14:23:57
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Fluorescence spectra of colloidal self-assembled CdSe nano-wire on substrate of porous Al <sub/>2</sub> O <sub/>3</sub> /Au nanoparticles
摘要： We present a self-assembly method to prepare array nano-wires of colloidal CdSe quantum dots on a substrate of porous Al2O3 film modified by gold nanoparticles. The photoluminescence (PL) spectra of nanowires are in situ measured by using a scanning near-field optical microscopy (SNOM) probe tip with 100-nm aperture on the scanning near-field optical microscope. The results show that the binding sites from the edge of porous Al2O3 nanopores are combined with the carboxyl of CdSe quantum dots’ surface to form an array of CdSe nanowires in the process of losing background solvent because of the gold nanoparticles filling the nano-holes of porous Al2O3 film. Compared with the area of non-self-assembled nano-wire, the fluorescence on the Al2O3/Au/CdSe interface is significantly enhanced in the self-assembly nano-wire regions due to the electron transfer conductor effect of the gold nanoparticles’ surface. In addition, its full width at half maximum (FWHM) is also obviously widened. The method of enhancing fluorescence and energy transfer can widely be applied to photodetector, photocatalysis, optical display, optical sensing, and biomedical imaging, and so on.
关键词： porous Al2O3 film,colloidal self-assembled method,CdSe nano-wire,enhanced photoluminescence
更新于2025-11-25 10:30:42
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Hot wire chemical vapor deposition for silicon photonics: An emerging industrial application opportunity
摘要： In this work different silicon photonic devices, including straight waveguides, multi-mode interference devices and Mach-Zehnder interferometers, were fabricated and characterized on hot-wire chemical vapor deposition (HWCVD) silicon nitride (SiN) layers deposited at temperatures below 350 °C. These layers presented a hydrogen concentration of 13.1%, which is lower than that achieved with plasma enhanced chemical vapor deposition at these deposition temperatures. The lowest reported optical propagation losses of 6.1 dB/cm and 5.7 dB/cm, 1550 nm and 1310 respectively, for straight SiN waveguides prepared by HWCVD was measured. We demonstrated that silicon nitride SiN, prepared using HWCVD, is a viable material for silicon photonics fabrication.
关键词： Multimode interferometer,Silicon photonics waveguides,Silicon photonics,Hot wire chemical vapor deposition,Silicon nitride,Mach-Zehnder interferometer
更新于2025-11-21 11:20:42
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Role of chamber pressure on crystallinity and composition of silicon films using silane and methane as precursors in hot-wire chemical vapour deposition technique
摘要： Hot-wire chemical vapour deposition is a versatile technique to deposit a-Si:H and nc-Si films at higher deposition rate (~5-10 ?/sec) as compared to Plasma enhanced chemical vapour deposition (1-2 ?/sec). We report the deposition of highly crystalline Si films at very high deposition rate (≥ 40?/sec) by adding methane to silane during thermal/catalytic decomposition. A series of films were deposited by varying the chamber pressure between 10-100 Pa at a substrate temperature of 300 °C and filament temperature 2000 °C. The hydrogen diluted silane (10% silane in hydrogen) and pure methane were used as precursors and gas flow rate ratio was kept constant at 10. Films prepared at lower pressure (≤ 20 Pa) were more crystalline and do not contain any trace of carbon atoms. Bandgap was found to increase from 1.24-1.63 eV when pressure was increased. It was observed that chamber pressure plays a key role in determining the crystallinity, disorder and composition of these films. Addition of methane to hydrogen diluted silane increased deposition rate and crystallinity of Si films at low pressure (≤ 20 Pa). Above 20 Pa pressure, carbon atoms signature was obtained. SiC films were obtained when pressure was > 100 Pa.
关键词： Deposition rate,Si films,Crystallinity,Hot-wire chemical vapour deposition
更新于2025-11-21 11:01:37
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Electron Transport Properties of Graphene-Based Quantum Wires
摘要： We study the electronic transport in quantum wire structures made of graphene. By using the nonequilibrium Green function method, the transmission is studied for varies sizes samples. Our results show that the transmission sensitive depends on the size of the system and exhibits fluctuations due to the mismating of propagating modes between the central region and the leads. The number of resonant transmission peaks increases with the increase of length of the wire, while the width of the leads mainly affect the transmission in the region of low energy. A central energy gap in the transmission spectrum is more likely to appear in the quantum wire system than in the uniform armchair graphene nanoribbons. Moreover, the energy gap can be widened for a certain size of the quantum wire system by changing the width of the leads. These results may have potential applications in designing graphene-based devices.
关键词： graphene,quantum wire,transmission
更新于2025-09-23 15:23:52
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Study on Charge transportation and scaling behavior of CsPbI3 microwires
摘要： Cesium lead iodide (CsPbI3) has been prepared by a new experimental hazard free precipitation technique. X-ray diffraction spectra have been interpreted with Rietveld refinement which assures the orthorhombic phase of CsPbI3. Energy dispersive X-ray fluorescence spectra confirms the formation of ternary compound. Orthorhombic to cubic phase transition has been studied by observing hysteresis loop in R(T)-T plot for forward-reverse temperature scan. The intra-grain and inter-grain contribution of CsPbI3 to dielectric relaxation has been accounted by fitting the complex impedance plot (Cole-Cole plot). The value of FWHM in Z″(ω)-lnf or M″(ω)-lnf plot is greater than 1.141 decades which reveals the non-Debye type relaxation within material. The broad relaxation peak signifies that there is a distribution of relaxation time over a mean value. Moreover, Z″ & M″ have been plotted in scaled coordinate to check whether the distribution of relaxation time is temperature dependent or not. The frequency dependent relative permittivity represents the decreases of polarizations with frequency which have been successfully analyzed by Koop’s theory. Here, activation energies are equal for different formalism, suggests that the same type charge carriers involved in conduction as well as relaxation process. Ac conductivity has been interpreted by using Jonncher’s power law and frequency exponent (n) increases with temperature which suggests the presence small polaron hopping mechanism.
关键词： Joncher’s power law,dielectric relaxation,Rietveld,Hysteresis,Cole-Cole plot,CsPbI3 micro-wire
更新于2025-09-23 15:23:52
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Preparation and measurement of subwavelength bilayer metal wire grid polarizers on flexible plastic substrates
摘要： This paper presents a process for the fabrication of subwavelength bilayer metal wire grid polarizers and describes the performance characterization of polarizers that were produced using the proposed method. These polarizers have a period of 278 nm and were fabricated on flexible plastic substrates using nanoimprint lithography followed by an aluminum deposition process. Transmission efficiency in excess of 0.55 and an extinction ratio of more than 32 dB were achieved in the visible range when the aluminum layer thickness of the polarizer was 70 nm. When a polarization analyzer with a six-channel sensor prototype was tested, an average error of 0.2002? was obtained, with a maximum error of 1.105? and a standard deviation of 0.7255?. The proposed fabrication method will be suitable for many applications in optics, including the manufacture of compound eye structures.
关键词： Extinction ratio,TM transmission,Nanoimprint lithography,Bilayer metal wire-grid polarizers
更新于2025-09-23 15:23:52