- 标题
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Effect of Deposition Pressure, Nitrogen Content and Substrate Temperature on Optical and Mechanical Behavior of Nanocomposite Al-Si-N Hard Coatings for Solar Thermal Applications
摘要： Hard and optically transparent nanocomposite Al-Si-N thin films were deposited using DC magnetron sputtering at different process parameters. There was a significant effect of these parameters on the film properties affecting its mechanical and optical behavior. The nitrogen content or pressure, deposition pressure and substrate temperature strongly influence the phase formation which governs the hardness and optical transparency of the coating. Hardness was measured between 18 and 30 GPa. The band gap could be varied in the range of 3.8-4.2 eV by varying nitrogen pressures in the chamber during deposition. The films showed (0-80)% transparency in UV and visible region depending on the sputtering conditions.
关键词： mechanical behavior,optical coating,nanocomposite hard coatings
更新于2025-09-23 15:21:21
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Effect of Grain Size on the Fracture Behavior of Organic-Inorganic Halide Perovskite Thin Films for Solar Cells
摘要： Organic-inorganic halide perovskite (OIHP) thin ?lms at the heart of the new perovskite solar cells (PSCs) are very brittle, limiting the mechanical reliability of PSCs. Here we show that ?ne-grained MAPbI 3 (prototypical OIHP) ?lms with grain size (~290 nm) smaller than the typical ?lm thickness (~500 nm) tend to fracture intergranularly, resulting in low toughness (0.41 J.m ?2 ). In contrast, MAPbI 3 /substrate interfacial fracture occurs in ?lms with grains larger (~730 nm) than the ?lm thickness, resulting in much higher toughness (1.14 J.m ?2 ). Thus, coarse-grained OIHP ?lms are deemed desirable for not only improved PSCs performance and stability but also mechanical reliability.
关键词： Thin ?lms,Solar cells,Halide perovskites,Mechanical behavior,Grain boundaries
更新于2025-09-23 15:21:01
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Analysis of the Mechanical Behavior of AISI 4340 Steel Cylindrical Specimens Heat Treated with Fiber Laser
摘要： This paper describes a method for analyzing and improving mechanical behavior of a cylindrical workpiece made of AISI 4340 steel, by its heat treatment with a 3kW fiber laser source. Research and expertise acquired in recent years have shown that improving the mechanical properties of AISI 4340 steel by heat treatment significantly reduces the design dimensions and thus optimizes the final weight of the product. Understanding the impact that a laser heat treatment can have on mechanical properties and the fatigue life can lead to significantly optimizing the design dimensions. This research investigates the effect and control of laser heat treatment parameters to optimize the mechanical behavior of an AISI 4340 steel cylindrical standard-specimen, which has a diameter of the calibrated part of 9.00-mm. The control of the case depth and its uniformization were guided by experimental and numerical modeling. Tensile tests, fatigue tests (hysteresis loops), microhardness, optical microscopy, and scanning electron microscopy measurements were used to evaluate each condition of the experimental design. Results indicate that laser heat treatment increases fatigue endurance by more than 20% compared to non-hardened samples. Moreover, it is shown with a model of neural prediction, and a rigorous analysis of variance, that the numerical values of the mechanical properties are in direct agreement with the laser hardening input parameters.
关键词： Fiber laser,Fatigue endurance,AISI 4340 steel,Mechanical behavior,Heat treatment
更新于2025-09-23 15:21:01
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EBSD characterization of the L-605 Co-based alloy welds processed by pulsed Nd:YAG laser welding
摘要： Herein, pulsed Nd:YAG laser welding of the L-605 Co-based alloy was investigated. The effect of the welding heat input (HI) on the penetration depth, microstructure, and mechanical properties of the weld metal was studied. A field emission scanning electron microscopy equipped with an electron backscatter diffraction (EBSD) detector was used to perform microstructural characterization. The results indicated that use of the HI value in the range of 48–80 J/mm could result in the formation of sound welds with full penetration depth at bead-on-plate configuration. EBSD studies revealed that when a low HI value was used to fabricate the double-welded sample, the {1 0 0} direction of austenite grains in the weld metal was parallel to the transvers and welding directions. Regarding the single-welded sample with a high HI value, the ?1 0 0? direction was strongly oriented at an angle between 40° to 50° with respect to the welding direction. Improvement in the hardness of both single-welded and double-welded samples was observed, as compared to the based metal. The results of tensile tests showed that tensile strength of the weldments was higher or almost similar to that of the base metal. Overall, the changes in the HI values had no significant effect on mechanical behavior of the weldments.
关键词： EBSD analysis,Microstructure,Laser welding,Mechanical behavior,Co-based alloy
更新于2025-09-23 15:21:01
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Investigation on the microstructure and mechanical behaviors of a laser formed Nb-Ti-Al alloy
摘要： Nb-Ti-Al alloys have attracted much attention as a potential candidate for high-temperature structural applications beyond the scope of Ni-based superalloys. Previously, Nb-Ti-Al alloys were prepared by arc-melting or hot-pressing. In this study, laser forming of the Nb-23Ti-15Al alloy is explored, and the microstructure and mechanical behaviors are systematically investigated. The results indicate that the nearly defectless Nb-Ti-Al alloy with fine dendrites could be obtained through laser forming. Three phases, β, δ and Ti(O,C), present in the alloy, and the β/δ matrix displays a columnar microstructure. Moreover, the Ti(O,C) phase, a solid-solution of TiO or TiC, appears in the alloy. Ti(O,C) is formed due to the introduction of the O and C from the elemental powder, which has a face-centered cubic (FCC) structure and a moderate lattice parameter between that of TiO and TiC. Two morphologies of Ti(O,C), large cobblestone-like particles and small dispersive particles, are observed in the alloy. Forbidden reflections of δ phase occur due to double diffraction and slight superlattice reflections of β phase arise. Furthermore, refined β/δ phases and dispersed small Ti(O,C) result in higher microhardness and fracture toughness. In brief, our results indicate that laser forming is a potential method for manufacturing Nb-Ti-Al alloys with prominent properties.
关键词： Laser forming,Double diffraction,Mechanical behavior,Ti(O,C),Nb-Ti-Al alloy,Microstructure
更新于2025-09-23 15:19:57
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On the nanoscale behaviour of single-wall C, BN and SiC nanotubes
摘要： The paper presents a numerical study of defect-free single-wall carbon, boron nitride and silicon carbide armchair and zigzag nanotubes, through a simple stick-and-spring model, based on Morse and cosine potential functions. The study investigates the relaxed configuration of the tubes and gives a comprehensive evaluation of their elastic constants, which is performed by framing tensile, torsional and radial tests within the membrane behaviour of a Donnell thin shell model. Extensive comparisons with reference ab-initio results are given and used to refine some parameters of the potential functions for hexagonal silicon carbide nanomaterials.
关键词： ab-initio comparisons,mechanical behavior,elastic constants,stick-and-spring model,nanotubes
更新于2025-09-19 17:15:36
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Performance analysis of laser-induced biomimetic ceramic tools in interrupted cutting
摘要： Theoretical and experimental researches were conducted to analyze the performance of laser-induced biomimetic ceramic tools in interrupted cutting. The formation of biomimetic microscopic structure and its effects on the tool load and the mechanical behaviors were integrated in tool performance analysis. This work investigated the influences of the laser pulse angle and number on the ablation of the ceramic. A two-dimensional microstructure model was utilized when investigating the influences. The distribution variation of the heat source intensity was considered in the analysis of the influences. Fractal theory, damage mechanics and fracture mechanics were employed to analyze the mechanical behaviors for the biomimetic ceramic. These mechanical behaviors included the fractal dimension corresponding to the microcrack caused by laser, the initial integrated damage and the fracture toughness. A performance indicator was established for the biomimetic ceramic tool considering the tool load and the mechanical behaviors. It was found that the maximum depth caused by the laser pulses can be used to mirror the mechanical behaviors. The fractal dimension had a potential for the effective evaluation of the initial integrated damage and the fracture toughness. When the laser angle was 60° and the number of scans was 3, the biomimetic ceramic tool exhibited the best performance. The balance among the tool load, the initial integrated damage and the fracture toughness should be achieved to obtain the best tool performance.
关键词： Ceramic ablation,Mechanical behavior,Cutting performance,Biomimetic ceramic tool
更新于2025-09-16 10:30:52
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Wholea??field strain analysis and strength prediction of fiber laser machined CFRP laminate at elevated temperature
摘要： High power fiber laser was proved to be feasible to cut carbon fiber reinforced plastic (CFRP) laminate with high efficiency, while the machined quality on mechanical performance was not fully understood. This paper studied the effect of high temperature up to 220°C on tensile strength degradation and strain distribution of unidirectional CFRP laminate with open hole machined with fiber laser. Differential scanning calorimetry (DSC) was firstly employed to determine the glass transition temperature (Tg) of polymer-matrix composite. Digital image correlation technique was applied to evaluate whole-field strain distribution and crack propagation/evolution of CFRP laminate featured with open hole under tensile loading. Results showed that the tensile strength of laser machined CFRP laminate degraded significantly during working in high temperature above 100°C. The value of strains distributed around center hole was highly related to the elevated temperature and applied load levels. Splitting was the prevalent failure mode of CFRP laminate under elevated temperature up to 180°C. Finally, semi-empirical model was developed for evaluating tensile performance of laser machined CFRP laminate at elevated temperature based on regression analysis.
关键词： digital image correlation,laser cutting,mechanical behavior,strain distribution,CFRP
更新于2025-09-16 10:30:52
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Thermal damage of CFRP laminate in fiber laser cutting process and its impact on the mechanical behavior and strain distribution
摘要： Fiber laser cutting is a promising alternative to the conventional methods in machining CFRP with high efficiency, while the influence of machined quality on strain distribution and mechanical behavior of CFRP laminates is yet not fully understand. The aim of this paper is to study the effect of laser cutting parameters on thermal defects and related mechanical performance. DIC technique was successfully employed to assess full-field strain distribution under tensile loading. The relationship between strain distribution and failure evolution/mode was also investigated. Results showed that various thermal defects including matrix recession, resin decomposition, fiber burrs and delamination were observed on entry and exit surfaces, while microcracks, cavities and striations were prevalent on machined surface. Tensile strength of CFRP laminate with open hole was highly related to applied laser processing parameters. DIC technique indicated that the crack propagation and failure mode were in good agreement with the high level of strains developed around the hole. Matrix-fiber interface cracking, fiber breakage and splitting were the main failure modes at test cessation.
关键词： Strain distribution,Laser cutting,Mechanical behavior,CFRP
更新于2025-09-11 14:15:04
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Thermo-mechanical behavior assessment of smart wire connected and busbar PV modules during production, transportation, and subsequent field loading stages
摘要： Thermo-mechanical loads induce stresses in photovoltaic (PV) modules, leading to crack formation. In this context, the understanding of module’s thermo-mechanical behavior is important. To investigate the thermo-mechanical behavior of smart wire connected technology (SWCT) and busbar PV modules throughout their entire life, the present study is conducted that probes the stress distribution and deformation during production, transportation, and subsequent mechanical and thermal loading stages in a consecutive step-by-step manner using finite element modelling approach. Pre-stresses and non-linearities are considered in simulation models. Stresses and displacements experienced by different parts/layers are examined, and crack sensitive regions are identified. In addition, the SWCT and busbar modules are compared, and it is found that SWCT interconnection is relatively a less stress inducing process and less susceptible to thermal and dynamic affects. During production stage, stresses of 39.3 MPa and 40.4 MPa are generated in SWCT cells and copper wires respectively; while, stresses of 60 MPa and 87 MPa are generated in busbar cells and busbar respectively. Similarly, lower stresses are induced in SWCT PV modules during subsequent stages. The comparison results show advantages of SWCT module in terms of mechanical stability which can lead to improve the performance and reliability of PV modules.
关键词： Production,Mechanical and thermal loads,Thermo-mechanical behavior,Smart wire connected technology (SWCT) PV modules,Transportation,Busbar PV modules
更新于2025-09-09 09:28:46