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Impacts of Defocusing Amount and Molten Pool Boundaries on Mechanical Properties and Microstructure of Selective Laser Melted AlSi10Mg
摘要： The influences of processing parameters such as volumetric energy density (ε) and, particularly, defocusing amount (DA) on densification, microstructure, tensile property, and hardness of the as-printed dense AlSi10Mg alloy by selective laser melting (SLM) were studied systematically. The molten pool boundaries (MPBs) were found overwhelmingly at regular and complex spatial topological structures affected by DA value to exist in two forms, while the “layer–layer” MPB overlay mutually and the “track–track” MPBs intersect to form acute angles with each other. The microstructure of MPBs exhibits a coarse grain zone near the MPBs and the characteristics of segregation of nonmetallic elements (O, Si) where the crack easily happened. The DA value (?2 to 2 mm) affected both the density and the tensile mechanical properties. High tensile strength (456 ± 14 MPa) and good tensile ductility (9.5 ± 1.4%) were achieved in the as-printed condition corresponding to DA = 0.5 mm. The tensile fracture surface features were analyzed and correlated to the influence of the DA values.
关键词： selective laser melting (SLM),mechanical properties,aluminum alloys
更新于2025-09-23 15:22:29
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Synthesis and Consolidation of Nanostructured Nb <sub/>2</sub> C–Al <sub/>2</sub> O <sub/>3</sub> Composite
摘要： Although an extremely hard ceramic material, niobium carbide has low fracture toughness to use wide applications. To fabricate nanostructured composite is common method to improve fracture toughness. Nanopowder mixture of Nb2C and Al2O3 were synthesized according to the reaction from Al4C3 and Nb powders by high-energy ball milling. The synthesized mixture of Nb2C and Al2O3 powders was consolidated by pulsed current activated sintering method within two min under the 80 MPa pressure. Nb2C and Al2O3 in the composite were nano-sized phases. The fracture toughness of a nanostructured Nb2C–Al2O3 composite of this study is better than that of previous study.
关键词： Rapid Sintering,Composite,Mechanical Properties,Nb2C–Al2O3,Nanomaterial
更新于2025-09-23 15:22:29
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The Effects of the Content of NiO on the Microstructure and Photocatalytic Activity of the NiO/TiO2 Composite Film
摘要： The NiO/TiO2 composite films with the NiO content of 3 %, 5 %, 10 %, 13 %, 15 % and 20 % were prepared by mechanical coating technology and subsequent oxidation process. The composition and microstructure of the films were analyzed by X-ray Diffraction (XRD), scanning electron microscope (SEM), and energy dispersive spectroscopy (EDS). The photocatalytic activity was evaluated and the effects of the content of NiO on microstructure and photocatalytic activity of the films were studied. The results show that NiO particles are dispersed in the Ti coatings, and the NiO concentration in the inner layer of the coatings is higher than in the outer layer. With the addition of NiO in the NiO/Ti coating, the ductility is deteriorated and the thickness is reduced of the NiO/Ti coatings. The films with NiO/TiO2/Ti composite microstructure are obtained by the oxidation of NiO/Ti coatings. Photocatalytic efficiency of the films is obviously enhanced with the help of the p-n junction heterostructure in the NiO/TiO2 films. The optimum content of NiO is about 13 %, and the degradation rate of methyl orange solution reaches the maximum value of 88.44 %.
关键词： mechanical coating technology,NiO content,photocatalytic activity,NiO/TiO2 composite films
更新于2025-09-23 15:22:29
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Fabrication, Modelling and Assessment of Hybrid 1-D Elastic Fabry Perot Microcavity for Mechanical Sensing Applications
摘要： 1-D multilayer dielectric films consisting of seven pairs of SiO2 and TiO2 alternating layers are deposited on a SiO2 substrate using the radio frequency sputtering technique. The thicknesses of the film layers are chosen to reflect the visible radiation around 650 nm. An elastic microcavity layer made of Polydimethylsiloxane was sandwiched between two Bragg reflectors. A fabrication process was then developed for elastic microcavity in order to tailor the thickness, establish the surface planarity and to increase reproducibility of the samples. Optical transmittance of the single Bragg reflector and the microcavity were both simulated and measured. A comparison between measurement data and Transfer Matrix Method calculations shows a favourable correlation. Furthermore, in order to assess the suitability of the microcavity as a force sensor, transmittance measurements were carried out as a function of the applied forces. The change in the elastic microcavity thickness due to applied forces resulted in cavity resonance peak shifts proportional to the applied forces.
关键词： Optical Characterization and Modelling,Silica and Titania,1D Elastic Photonic Crystal,Mechanical Sensor,RF sputtering,PDMS
更新于2025-09-23 15:22:29
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Composite modeling and parameter identification of broad bandwidth hysteretic dynamics in piezoelectric fast steering platform
摘要： Over a broadband range of frequencies, it is difficult to develop precise model of piezoelectric fast steering platforms (FSPs) due to the complex hysteretic and dynamic behaviors. This paper thus presents one approach of composite modeling and parameter identification by employing a composite hysteretic model. The proposed composite model consists of the Bouc-Wen hysteresis, electro-mechanical dynamics, creep dynamics and the high frequency mirror dynamics. Physical meanings can be found in the linear component which is beneficial to controller design and other further developments using the proposed model. A step-by-step approach is proposed to identify the composite hysteretic model. Finally, the FSP experiment is provided to validate the effectiveness of the proposed modeling and parameter identification approaches.
关键词： Electro-optical system,Creep effect,Hysteretic dynamics,Fast steering platform,Electro-mechanical dynamics,Piezoelectric actuator
更新于2025-09-23 15:22:29
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Design of a novel dual-axis micro manipulator with an asymmetric compliant structure
摘要： This paper presents a novel piezoelectrically actuated dual-axis micro manipulator with an asymmetric compliant structure. The mechanical design of the micro manipulator is first presented. A novel guiding bridge (GB)-type mechanism was proposed and utilized in the left part of the micro manipulator to improve the dynamic performance of the micro manipulator. The analytical model has been established based on pseudo-rigid-body (PRB) model and matrix-based compliance modeling (MCM) method. The kinematic and the precision of the micro manipulator have been analyzed, and the input and output couplings have been investigated. The prototype of the micro manipulator has been fabricated by wire electro discharge machining (WEDM). Then, open-loop experimental tests have been performed. The experimental results match well with the analytical calculation, and the amplification ratios are 11.12 and 4.64 for left part and right part, respectively. Proportional-integral (PI) controller has been used to regulate the output displacement and grasping force, and a series of closed-loop experiments have been conducted to investigate the performance of the micro manipulator. The results show that the position resolution for both the right and left parts is 0.15 μm, and the force resolution is 4 mN.
关键词： Mechanical design,Piezoelectric actuator,Micro manipulator,Compliant mechanism
更新于2025-09-23 15:22:29
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[IEEE 2017 International Renewable and Sustainable Energy Conference (IRSEC) - Tangier (2017.12.4-2017.12.7)] 2017 International Renewable and Sustainable Energy Conference (IRSEC) - Thermomechanical Investigation of PV Panels Behaviour under NOCT Conditions
摘要： Numerous works on the enhancement of photovoltaic cells’ efficiency can been found in the literature. However, studies related to its durability are limited. For instance, solar radiation induced internal thermal stresses on the structure of photovoltaic (PV) panels has received little attention. These effects cannot be ignored when analyzing the panel’s durability. The internal stresses are difficult to measure since a PV panel is a complex structure composed by different layers, which causes a non-uniform distribution of the temperature inside the panel. In this work, fully coupled thermo-mechanical finite element simulations were performed with the commercial code ABAQUS/CAE to estimate these stresses. Temperature variations and local stress states are estimated throughout the PV panel thickness under nominal operating conditions.
关键词： thermo-mechanical stresses,FE simulation,silicon solar cells,PV panels
更新于2025-09-23 15:22:29
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Characterization of CMP Slurries Using Densitometry and Refractive Index Measurements
摘要： We investigated the possibility of employing refractive index (RI) measurements for inline incoming slurry control at the point of use (POU), as an alternative to the widespread densitometry method. As such, it became necessary to determine if RI could detect smaller changes in slurry composition and, therefore, provide a tighter control. Three industrially-relevant silica-based slurries, namely, Fujimi PL-7106, Klebosol 1501-50, and CMC W7801, were characterized using both densitometry and RI measurements. Initial solutions of the three slurries were prepared and increasingly small amounts of ultrapurified water (UPW) were added to study the change in slurry properties. Results showed that both density and RI decreased linearly with the addition of water for all three slurries, with the 1501-50 being the most sensitive to water addition. A linear correlation between the two properties was found, with R2 values that exceeded 0.95 in all cases. Furthermore, the approximate limit of detection of both metrology tools was estimated based on the slope of the fitting line and resolution. When compared to densitometry, RI was found to be the far superior method for detecting smaller changes in water concentration.
关键词： semiconductor technology,slurry characterization,in-line monitoring and control,chemical mechanical planarization
更新于2025-09-23 15:22:29
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Pulsed Current Activated Sintering of Nanostructured ZrO <sub/>2</sub> and 3YSZ and Their Mechanical Properties
摘要： As nanostructured materials possess high strength, high hardness, excellent ductility and toughness, undoubtedly, more attention has been paid for the application of nanomaterials. When conventional sintering processes are used to sinter nano-sized zirconia powders, concomitant grain growth leads to the destruction of the nanostructure. This focuses attention on consolidation methods in which grain growth can be eliminated or significantly reduced. To accomplish this, rapid sintering methods have been widely used to sinter nano-sized powders. Nanopowders of ZrO2 and 3YSZ were fabricated and rapidly consolidated using high-energy ball milling and the pulsed current activated sintering (PCAS). The sintering behavior and crystallite size ZrO2 and 3YSZ powders were evaluated. A nanostructured dense 3YSZ compact with a relative density of up to 99% was readily obtained within one min. The hardness and fracture toughness of ZrO2 and 3YSZ sintered from powders milled for 10 h were 450 and 1160 kg/mm2, 3 and 4.4 MPa · m1/2. Not only hardness but also fracture toughness of 3YSZ are higher than those of ZrO2.
关键词： ZrO2,3YSZ,Mechanical Properties,Nanomaterials,Sintering
更新于2025-09-23 15:22:29
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Universal Testing Apparatus Implementing Various Repetitive Mechanical Deformations to Evaluate the Reliability of Flexible Electronic Devices
摘要： A requirement of flexible electronic devices is that they maintain their electrical performance during and after repetitive mechanical deformation. Accordingly, in this study, a universal test apparatus is developed for in-situ electrical conductivity measurements for flexible electrodes that are capable of applying various mechanical deformations such as bending, twisting, shearing, sliding, stretching, and complex modes consisting of two simultaneous deformations. A novel method of deforming the specimen in an arc to induce uniform bending stress in single and alternating directions is also proposed with a mathematically derived control method. As an example of the arc bending method, the changes in the resistance of the printed radio frequency identification (RFID) tag antennas were measured by applying repetitive inner bending, outer bending, and alternating inner-outer bending. After 5000 cycles, the increases in resistance of the specimens that were subjected to inner or outer bending only were under 30%; however, specimens that were subjected to alternating inner-outer bending showed an increase of 135% in resistance. It is critical that the reliability of flexible electronic devices under various mechanical deformations be determined before they can be commercialized. The proposed testing apparatus can readily provide various deformations that will be useful to inform the design of device shapes and structures to accommodate deformations during use.
关键词： mechanical deformation,printed electronics,reliability,test apparatus,flexible electronics
更新于2025-09-23 15:22:29