The tensile behavior of bulk AlSi10Mg components, fabricated by selective laser melting (SLM), was investigated by uniaxial tensile testing and image-based finite element simulation. The initial ...morphological features of the structures were imaged by micro X-ray tomography. Moreover, the reconstructed model and as-designed model were compared to quantify the process-induced defects, which remained unavoidable due to complex manufacturing processes. The un-melted AlSi10Mg powders, sticking to the melting pool after condensation, intensified the deviation of side edges. Futhermore, the unevenly distributed process-induced defects resulted in anisotropic mechanical properties of AlSi10Mg alloy. Two finite element models were developed from X-ray tomography images and CAD model, which were simulated by finite element solver ABAQUS/Standard to discuss the effect of initial morphological features on the mechanical behavior of these samples. The geometric defects have slightly reduced Young's modulus and yield strength, but remarkably increased the equivalent plastic strain of the bulk structures. Furthermore, the ultimate strength and elongation, predicted by the image-based finite element model and the ductile failure criterion, was much lower than the values predicted by the as-designed model due to the influence of geometric defects.
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•Morphological features of AlSi10Mg alloy were imaged by micro X-ray tomography.•Reconstructed and as-designed models were aligned for defects quantification.•An image-based FEM was proposed based on process-induced defects.•The impact of geometric defects on mechanical properties of AlSi10Mg was studied.
Dual‐ion batteries (DIBs) attract great interest because they allow two types of ions for reversibly intercalating into electrodes, resulting in various advantages. However, there are three critical ...problems using graphite‐based cathodes, namely, low active material proportion in the electrodes, current collector corrosion, and massive cathode variation. For addressing these problems, an ultra‐lightweight 3D carbon current collector (CCC) is developed to fabricate all‐carbon electrodes as both cathodes and anodes. Compared with the conventional DIBs using Al and Cu foils as current collectors, the DIBs with 3D CCC of electrically conductive pathways and sufficient ionic diffusion channels deliver enhanced specific capacity stabilized around 140 and 120 mAh g−1 at 0.5 and 1C, respectively. The electrochemically inert 3D CCC could essentially promote the energy density when calculating the entire electrode mass, along with long‐life cycle stability of 1000 cycles at 5C and no electrochemical corrosion on either anodes or cathodes. With an in situ optical microscope, the cathode expansion is found to massively reduce because the porous 3D CCC could effectively alleviate the huge volume. The results suggest a novel strategy for achieving low‐cost and high energy density DIBs with both mechanically and electrochemically stable features.
Ultra‐lightweight 3D carbon current collectors are employed to construct all‐carbon electrodes used in dual‐ion batteries. The critical problems including metal corrosion, low mass ratio of active materials, and massive volume expansion in the cathodes based on metal current collectors are well addressed, promising a novel strategy for achieving high energy density batteries with both mechanically and electrochemically stable features.
•Vibration behaviors of lattice-core sandwich cylinder were revealed.•LSC is stiffer and has higher fundamental frequency than LSC.•Suggested equivalent method is accurate to predict vibration ...behaviors of LSC.
To study mechanical behaviors of advanced carbon fiber reinforced composite (CFRC) sandwich cylinder with lattice cores, uni-axial compression and free vibration experiments were carried out. Load carrying capacity and local failure modes of the lattice-core sandwich cylinder (LSC) were revealed. Natural frequencies and vibration modes of CFRC LSC were revealed by experiments for the first time. For usual LSC in astronautic engineering, the first order vibration is in the plane of the cross section, turning from a circle to an oval. An equivalent method was proposed to predict the primary frequency and mode shape of the LSC, which is in excellent accordance with the experiment. Compared with grid stiffened cylinder (GSC), LSC of the same weight and dimension always has higher primary frequency, indicating that LSC is much stiffer and could be designed even lighter in astronautic applications.
Origami structures are of great interest in microelectronics, soft actuators, mechanical metamaterials, and biomedical devices. Current methods of fabricating origami structures still have several ...limitations, such as complex material systems or tedious processing steps. We present a simple approach for creating three-dimensional (3D) origami structures by the frontal photopolymerization method, which can be easily implemented by using a commercial projector. The concept of our method is based on the volume shrinkage during photopolymerization. By adding photoabsorbers into the polymer resin, an attenuated light field is created and leads to a nonuniform curing along the thickness direction. The layer directly exposed to light cures faster than the next layer; this nonuniform curing degree leads to nonuniform curing-induced volume shrinkage. This further introduces a nonuniform stress field, which drives the film to bend toward the newly formed side. The degree of bending can be controlled by adjusting the gray scale and the irradiation time, an easy approach for creating origami structures. The behavior is examined both experimentally and theoretically. Two methods are also proposed to create different types of 3D origami structures.
With the advent of flexible/wearable electronic devices, flexible lithium-ion batteries (LIBs) have attracted significant attention as optimal power source candidates. Flexible LIBs with good ...flexibility, mechanical stability, and high energy density are still an enormous challenge. In recent years, many complex and diverse design methods for flexible LIBs have been reported. The design and evaluation of ideal flexible LIBs must take into consideration both mechanical and electrochemical factors. In this review, the recent progress and challenges of flexible LIBs are reviewed from a mechano-electrochemical perspective. The recent progress in flexible LIB design is addressed concerning flexible material and configuration design. The mechanical and electrochemical evaluations of flexible LIBs are also summarized. Furthermore, mechano-electrochemical perspectives for the future direction of flexible LIBs are also discussed. Finally, the relationship between mechanical loading and the electrode process is analyzed from a mechano-electrochemical perspective. The evaluation of flexible LIBs should be based on mechano-electrochemical processes. Reviews and perspectives are of great significance to the design and practicality of flexible LIBs, which is contributed to bridging the gap between laboratory exploration and practical applications.
•A variety of geometries of specimens, including the modified shear-compression, shear-tension, and thin-walled tubular specimen are designed to create different stress states.•A hybrid ...experimental–numerical method is developed to evaluate quantitatively the effect of stress stare on the initiation of ASB within Ti–6Al–4V.•A phenomenological model of ASB initiation considering stress triaxiality and Lode parameter is proposed. The proposed model can predict the initiation of ASB with good accuracy under the test condition of this work.
Shear failure is frequently accompanied with the formation of an adiabatic shear band (ASB) under dynamic loading condition. The results obtained by a previous study (Guo et al., 2019) indicate that temperature increase does not play a primary role in the formation of ASB. Moreover, the shear strain to ASB initiation is closely related to the stress state. In this paper, a hybrid experimental–numerical method is developed to evaluate quantitatively the effect of stress stare on the initiation of ASB within Ti–6Al–4V. A variety of geometries of specimens, including the modified shear-compression, shear-tension, and thin-walled tubular specimen are designed to create different stress states. Combined with high-speed photography, split Hopkinson bar systems are utilized to measure the mechanical response of these specimens. Critical shear strains of ASB initiation are acquired based on the high- speed photos. The stress state for each test condition is obtained by numerical simulation. A phenomenological model of ASB initiation considering stress triaxiality and Lode parameter is proposed. Compared to the experimental results, the proposed model can predict the initiation of ASB with good accuracy under the test condition of this work.
Fluted-core sandwich structures, consisting of fiber-reinforced plastics, are frequently utilized in the aerospace industry owing to their excellent strength-to-weight ratio. However, the thin-walled ...structures are prone to local buckling, which reduces their load-bearing capacity and eventually leads to material failure. The current study presents analytical models for predicting the local buckling of fluted-core sandwich panels subjected to uniform compressive load. The proposed method is based on a discrete plate analysis approach, which considers the face-sheets between two webs as rotationally-restrained plates, wherein the rotational restraint stiffness is determined based on the geometric configuration and material properties. Herein, two boundary conditions, i.e., simply-supported and clamped, along the loaded edges were studied. Several deflection functions were proposed based on the classical Rayleigh–Ritz method, satisfying the boundary conditions. The experimental tests and finite element simulations were carried out to analyze the local buckling behavior, rendering excellent consistency and demonstrating the reliability of the proposed method. The effects of geometric parameters on the local buckling behavior were systematically studied and the results revealed that the current analytical models with high computational efficiency are reliable, exhibiting promise of eventual success in the optimization of preliminary engineering designs.
•Local buckling analysis of the fluted-core composite panels was presented.•The buckling of rotationally-restrained plates was studied using Rayleigh–Ritz method.•Compressive local buckling behaviors were explored by experiment and FEA methods.•Effects of geometric parameters on local buckling behavior were discussed.
Safety is an essential topic to the architecture, engineering and construction (AEC) industry. However, traditional methods for structural health monitoring (SHM) and jobsite safety management (JSM) ...are not only inefficient, but also costly. In the past decade, scholars have developed a wide range of deep learning (DL) applications to address automated structure inspection and on-site safety monitoring, such as the identification of structural defects, deterioration patterns, unsafe workforce behaviors and latent risk factors. Although numerous studies have examined the effectiveness of the DL methodology, there has not been one comprehensive, systematic, evidence-based review of all individual articles that investigate the effectiveness of using DL in the SHM and JSM industry to date, nor has there been an examination of this body of evidence in regard to these methodological problems. Therefore, the objective of this paper is to disclose the state of the art of current research progress and determine the relevant gaps, challenges and future work. Methodically, CiteSpace was employed to summarize the research trends, advancements and frontiers of DL applications from 2010 to 2020. Next, an application-focused literature review was conducted, which led to a summary of research gaps, recommendations and future research directions. Overall, this review gains insight into SHM and JSM and aims to help researchers formulate more types of effective DL applications which have not been addressed sufficiently for the time being.
The microstructure evolution of electrodes with a mini-cylindrical battery was studied by deep learning combined with a cross-section polisher and scanning electron microscope.
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•The ...evolution of electrode microstructure at different states of charge is studied, considering the influence of the battery structure.•A larger representative region of the electrode is obtained by a combination of scanning electron microscopy (SEM) and a cross-section polisher (CP).•A modified U-Net neural network approach is proposed to improve the accuracy of segmentation.
The evolution of the microstructure of a battery electrode is closely related to battery performance. Characterization and visualization of the evolution of the microstructure is essential for optimization of manufactured electrodes. The validity of the battery structure representation affects the accuracy of the extracted microstructure parameters. In this study, a mini-cylindrical battery is designed to allow microstructure parameters to be obtained at different states of charge, bearing in mind the influence of the real battery structure. An argon-ion cross-section polisher is used to obtain a large area of the electrode for observation. In addition, an image segmentation method based on a modified U-Net neural network is developed to enhance the quality of the extracted microstructure. The relationship between porosity and thickness at different states of electrode charge is presented through experiments and deep learning of images. This method provides new insight into the evolution of electrode microstructure and can potentially guide the manufacturing of lithium-ion batteries.
Smart structures with manipulatable properties are highly demanded in many fields. However, there is a critical challenge in the pursuit of transparent windows that allow optical waves (wavelength of ...µm–nm) for transmitting while blocking microwave (wavelength of cm) in terms of absorbing electromagnetic energy, specifically for meeting the frequency requirement for the 5th generation (5G) mobile networks. For fundamentally establishing novel manipulatable microwave absorbing structures, here, new polymeric aqueous gels as both optically transparent materials and microwave absorbing materials are demonstrated, in which polar networks play significant roles in attenuating electromagnetic energy. By manipulating the hydrogen bonding networks, the resulting optically transparent solid‐state gels are able to offer the capabilities for absorbing microwaves. Interestingly, such gels can be switched into an optically opaque state via converting the amorphous state into a polycrystal state when the temperature is decreased. Such ionic conductive gels can endow the assembled sandwich windows with effective microwave absorbing capability in the range of 15–40 GHz, covering a branch of 5G frequency bands. The results highlight a new strategy for using ionic conductive gels to design and fabricate manipulatable microwave stealth structures for various applications.
Novel transparent ionic conductive gels are developed to fabricate optically manipulatable microwave stealth structures, which can be employed as transparent windows while blocking microwaves in terms of absorbing electromagnetic energy. Such smart gels can endow the assembled windows with effective microwave absorbing capability in the range of 15–40 GHz, advancing smart windows with upgraded manipulatable capabilities and functions.
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