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SSRN 2023年

作者： Zheng, Kaiyuan Lei, Yuchao Wu, Jiazhu Zhao, Penghui Luo, Yaoen Zhang, Yi State Key Laboratory of Advanced Design and Manufacturing Technology for Vehicle Hunan University Changsha410082 China Key Laboratory for Intelligent Laser Manufacturing of Hunan Province Hunan University Changsha410082 China School of Mechanical Engineering Guizhou University Guiyang550025 China

High-speed laser material deposition (HLMD) technology significantly enhances deposition efficiency while maintaining quality. The core of designing HLMD lies in formulating the laser-powder coupling, through considering nozzle structural and deposition process parameters. In this study, we constructed a laser-powder coupling model that accounts for the impact of aerodynamic drag on powder particle movement and the heating effect of laser of flying powders. The model delineates the coupling mechanism between the laser beam and a discontinuous coaxial powder stream (DCPS), comprised of individual single powder streams (SPSs). Simulations were executed to assess the effects of nozzle structural parameters and deposition process parameters on the DCPS spot size and SPS particle temperature distribution. Simultaneously, a data pretreatment method, involving gray processing, normalization, and renormalization of the thermal images successively, was applied to measure the particle temperature distribution, and validate the laser-powder coupling model. The simulation results indicate that the DCPS spot size is predominantly influenced by nozzle structural parameters, including the nozzle exit diameter and injection angle. The SPS particle temperature distribution, meanwhile, is chiefly impacted by deposition process parameters like mean particle diameter, powder mass flow rate, and laser power. To achieve molten powder and uniform particle temperature distribution on the deposition plane within the DCPS, nozzle structural parameters and deposition process parameters were jointly designed, aligned with nozzle manufacturing prerequisites. The deposition rate of HLMD designed by this method is 1.7 times that of conventional laser material deposition, during processing of 316L stainless steel. This paper pioneers a new design methodology for HLMD, presenting a promising avenue for future applications. © 2023, The Authors. All rights reserved.

关键词： Temperature distribution

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Effects and Mechanisms of Heteroatom-Doped Hierarchical Porous Carbon on Hydrogen Storage Properties of Mgh2

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SSRN 2024年

作者： Li, R. Zhang, Jian Zhou, Xiao-Jie Pang, Xiaotong Ji, X.X. Duan, Junfei Lu, Xian-Zheng Chen, Xiao-Min Li, J.H. Zhou, D.W. Hunan Provincial Key Laboratory of Intelligent Manufacturing Technology for High-performance Mechanical Equipment Changsha University of Science and Technology Changsha410114 China School of Materials Science and Engineering Changsha University of Science and Technology Changsha410114 China State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body Hunan University Changsha410082 China

In this paper, the nitrogen doped (N-HPC), nitrogen and phosphorus co-doped hierarchical porous carbon (NP-HPC) are prepared by cross-linking phytic acid and poly pyrrole/aniline precursor, respectively. They are mixed with MgH2 by high-energy ball milling, and then their effects and mechanisms on the hydrogen absorption and desorption properties of MgH2 are investigated. Meanwhile, the hydrogen storage properties of MgH2 added with graphite (G) are also compared. The results show that the additions of NP-HPC, N-HPC, and G all exhibit the catalytic effect on the hydrogen absorption and desorption of MgH2. As for the hydrogen desorption, the catalytic effect is enhanced in the order of N-HPC, G and NP-HPC. Compared with pure MgH2, the hydrogen desorption temperature is reduced by 65.3°C, 79.6°C and 91.1°C, respectively. Among them, the MgH2 + NP- HPC system can release 5.17 wt% hydrogen at 300 °C within 30 min. First-principle calculations reveal that the P-doped and vacancy-containing carbon materials significantly reduce the H2 recombination barrier from the surface of MgH2 and distort the atomic structure of near-surface layer of MgH2, which in turn weakens the Mg-H bond strength. This may be the intrinsic reason for the excellent catalytic effect of NP-HPC and vacancy-containing G on the hydrogen desorption performance of MgH2. © 2024, The Authors. All rights reserved.

关键词： Magnesium compounds

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Numerical Study on the Performance, Combustion Characteristics, and Energy Flow Distribution of Gasoline-Powered vehicle Under Synthetic Actual Driving Test Cycle

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SSRN 2023年

作者： Qiao, Junhao Liu, Jingping Jia, Dongdong Fu, Jianqin Liu, Shenghui Li, Yangyang Guan, Jinhuan Wang, Shuqian State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body Hunan University Changsha410082 China College of Biological and Chemical Engineering Zhejiang University of Science and Technology Hangzhou310023 China State Key Laboratory of Automotive Safety and Energy Tsinghua University Beijing100084 China Hunan University China

In order to meet the requirements of vehicle performance prediction and optimization, a synthetic actual driving test cycle (ADTC) is proposed to accurately predict the related performance, and energy distribution characteristics of vehicles with urban road conditions. Meanwhile, a multi-physical field vehicle energy management simulation model is built and has been carefully verified. Thus, the relevant characteristic parameters of the vehicle under the ADTC are numerically analyzed, and the interfering factors of energy items are revealed and compared. The results show that the synthetic ADTC can more accurately reflect the vehicle's operating conditions and provide guidance for more detailed vehicle optimization. The BTE of the engine under ADTC varies in the range of 14.88 % to 30.54 %, that is lower than WLTC and NEDC. Besides, the proportion of combustion loss is WLTC, ATDC and NEDC from the largest to the smallest, which is mainly related to the complexity of speed variation. In particular, the ratio of exhaust loss and combustion heat loss to total energy is very large under any test cycle. The purpose of this study is to achieve real-time control of vehicle performance under transient conditions and achieve the goal of emission reduction energy utilization optimization. © 2023, The Authors. All rights reserved.

关键词： vehicle performance

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A Crystal-Plasticity Cyclic Constitutive Model for the Ratchetting of Polycrystalline Material Considering Dislocation Substructures

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Acta Mechanica Solida Sinica 2020年第2期33卷 268-280页

作者： Xuehong Ren Shaopu Yang Guilin Wen Wenjie Zhao State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body Hunan UniversityChangsha 410082China State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao UniversityShijiazhuang 050043China

A crystal-plasticity cyclic constitutive model of polycrystalline material considering intra-granular heterogeneous dislocation substructures,in terms of three dislocation categories:mobile dislocations,immobile dislocations in the cell interiors and in the cell walls,is proposed based on the existing microscopic and macroscopic experimental *** multiplication,annihilation,rearrangement and immobilization of dislocations on each slip system are taken as the basic evolutionary mechanism of the three dislocation categories,and the cross-slip of screw dislocations is viewed as the dynamic recovery mechanism at room *** slip resistance associated with the isotropic hardening rule results from the interactions of dislocations on the slip ***,a modified nonlinear kinematic hardening rule and a rate-dependent flow rule at the slip system level are employed to improve the predictive capability of the model for ratchetting *** predictive ability of the developed model to uniaxial and mul-tiaxial ratchetting in macroscopic scale is verified by comparing with the experimental results of polycrystalline 316L stainless *** ratchetting in intra-granular scale which is obviously dependent on the crystallographic orientation and stress levels can be reasonably predicted by the proposed model.

关键词： Ratchetting Dislocation substructures Crystal plasticity Polycrystalline materials Constitutive model

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Interaction of the Initial β-Mg17Al12 Phase with α-Matrix Grains in the AZ91 Magnesium Alloy During Hot Extrusion

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SSRN 2025年

作者： Zhao, Dijia Shao, Yuman Lü, Shulin Yan, Zhaoxiang Guo, Wenbo Li, Shilong Li, Jianyu Xu, Shiwei Wu, Shusen Nie, Jianfeng State Key Laboratory of Materials Processing and Die & Mould Technology Huazhong University of Science and Technology Wuhan430074 China State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body Hunan University Changsha410082 China Department of Materials Science and Engineering Monash University VIC3800 Australia

Secondary phase particles in magnesium alloys can facilitate particle-stimulated nucleation and pinning the grain boundary migration during the dynamic recrystallization (DRX) process. But a conflict exists between these two effects. By optimizing the hot extrusion process and preserving the irregular island-shaped β-Mg17Al12 phase (β-phase) derived from the eutectic reaction in the AZ91 magnesium alloy billet, we revealed the interaction of the initial β-phase with the α-matrix during extrusion. In the early stages of extrusion, the irregular, island-shaped, coarse β-phase causes significant dislocation accumulation in the adjacent α-matrix due to the hardness difference. As dislocations accumulate, the β-phase fragments and transforms into spindly fibrous bands, effectively illustrating a pinning effect. The morphological change of the β-phase not only promotes the DRX process but also inhibits the growth of DRXed grains, thereby refining the grain size. This research helps to expand the design strategies for extruded magnesium alloys. © 2025, The Authors. All rights reserved.

关键词： Magnesium alloys

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Experimental Characterization and Theoretical Prediction of Asymmetric Failure Behaviors Under Complex Stress States in 3d Printed Continuous Carbon Fiber Reinforced Composites

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SSRN 2024年

作者： Sun, Guangyong Luo, Junjie Zou, Ke Luo, Quantian Li, Qing State Key Laboratory of Advanced Design and Manufacturing Technology for Vehicle Hunan University Changsha410082 China Analytical Instrumentation Center of Hunan University Hunan University Changsha410082 China School of Aerospace Mechanical and Mechatronic Engineering The University of Sydney SydneyNSW2006 Australia

Due to a filament-by-filament and layer-by-layer structure produced by 3D printing technique, mechanical properties of 3D printed materials diverge considerably from those of traditional continuous carbon fiber reinforced polymer (C-CFRP) composites. This study performs experimental characterization through off-axis tensile, compressive and V-notch shear tests. A range of advanced imaging techniques, such as digital image correlation (DIC), SEM and CT is adopted to investigate anisotropic mechanical properties and failure mechanisms of the 3D printed C-CFRP composites under complex stress states. Further, the applicability of conventional failure criteria including Tsai-Wu, Tsai-Hill, Hoffman, Maximum Stress, Hashin, Puck and LaRC05 is assessed. The experimental results revel that the filament-by-filament and layer-by-layer features intrinsic to 3D printed C-CFRP composites lead to an uneven yet organized distribution of voids. This nature contributes to the claw mark strain patterns, parallel track inter-fiber failure patterns, and distinct compression failure modes such as delamination and interlayer crack under loading perpendicular to the fiber direction. The voids in the 3D printed C-CFRP materials are partially responsible for the significant asymmetry as off-axis angles increase. Notably, the conventional failure criteria exhibit limited capability for predicting the off-axis tensile strength accurately. This phenomenon can be attributed to the redistribution of initially prominent fiber waviness as the fibers encounter tensile loads. Based on the experimental results, the inter-fiber failure within LaRC05 is modified for obtaining an enhanced failure criterion for off-axis tensile strength. This study is expected to provide fundamental understanding on structural characteristics and mechanical properties for 3D printed C-CFRP composites. © 2024, The Authors. All rights reserved.

关键词： Tensile strength

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Collision Mitigation in Cyclist Injury-Based Motion Planning for Automated vehicles

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SSRN 2024年

作者： Yuan, Qiuqi Xiao, Zhi Zhu, Xiaoming Li, Jianyu Xiao, Peijie Xu, Shiwei School of Mechanical and Vehicle Engineering Hunan University Changsha410082 China State Key Laboratory of Advanced Design and Manufacturing Technology for Vehicle Hunan University Changsha410082 China Suzhou Research Institute Hunan University. Suzhou215144 China Shanghai Motor Vehicle Inspection Certification & Tech Innovation Center Co. Ltd. Shanghai201805 China

Automated vehicles (AVs) are expected to improve road traffic safety significantly. However, existing motion planning algorithms for AVs ignore the protection of vulnerable road users (VRUs) in corner cases (e.g., collisions are unavoidable). This work aims to reduce the severity of cyclist head injuries in the cases of an impending collision between AVs and two-wheelers by proposing a motion planning algorithm that combines injury prediction and optimization planning. First, we used the vehicle-two-wheeler simulated collision database to create a data mining-based prediction model for cyclist head injuries. Subsequently, a motion planning methodology that minimizes head injuries was proposed using this model. The proposed motion planning algorithm was tested under four typical cases. Simultaneously, we examined the effect of the initial speed of AV, the algorithm's starting position, and the algorithm's predictive-time domain on the algorithm's performance. The results demonstrate that the motion planning algorithm proposed in this study can considerably lower the severity of cyclist head injuries. The lower the initial speed of the AVs and the larger the predictive-time domain and the starting position of the algorithm, the greater the degree of reduction in the cyclist head injuries during the collision. It indicates that using the human injury prediction model based on data mining as the decision-making basis for the motion planning of AVs can significantly enhance road traffic safety. © 2024, The Authors. All rights reserved.

关键词： Bicycles

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Experimental study on the energy loss from flow and electrical of vanadium battery with constant pump frequency 2

Experimental study on the energy loss from flow and electric...

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2023 2nd International Conference on New Energy, Energy Storage and Power engineering, NESP 2023

作者： Sun, Yanzhao Zou, Tao Li, Dianhong Li, Juntao School of Electrical Engineering and Automation Wuhan University Hubei Wuhan430072 China Big Pawer Electrical Technology Xiangyang Co. Ltd. Hubei Xiangyang441057 China Hubei Key Laboratory of Power System Design and Test for Electrical Vehicle Hubei University of Arts and Science Hubei Xiangyang441053 China Hunan Vanadium Valley New Energy Technology Co. Ltd. Hunan Changsha410116 China

When the vanadium battery was running, pump frequency and current density were two frequently adjusted parameters. When the pump frequency was constant, the main flow-electrical parameter variation needs to be further studied. To this end, a 10 kW vanadium battery was built. When the current density was relatively high during the charge-discharge, the flow-electrical parameters of the cathode and anode including the temperature, flow resistance, turning voltage difference, capacity loss, energy loss and energy efficiency were studied. Besides, the compositions of capacity and energy were introduced, and the loss calculation scheme was proposed. Firstly, in flow analysis, the flow resistance was defined, which represents the flow state of the electrolyte. It was found that the flow resistance was nearly linear with the temperature. Secondly, in electric analysis, the turning voltage difference increased with the current density increasing. For the same current density, the total energy loss of charge was less than the discharge, and the energy loss of bypass was less than the internal resistance. With the current density increasing, the energy efficiency decreased. The research can be provided insight into the optimizing operation for the vanadium battery. © Published under licence by IOP Publishing Ltd.

关键词： Current density

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A Study on Anisotropic Hardening of 7075 Aluminum Alloy Based on Non-Associated Flow Rules

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SSRN 2024年

作者： Wu, Xiaodong Zhang, Wenkang Changsha Normal University Changsha410205 China State Key Laboratory of Advanced Design and Manufacturing Technology for Vehicle Hunan University Changsha410082 China College of Engineering Anhui Agricultural University Hefei230036 China

Accurate description of the anisotropic plastic deformation is the key to realize reliable finite element simulation of metal sheet forming process. The anisotropic yield criterion based on the assumption of isotropic hardening often results in significant errors. This paper, therefore, observes the anisotropic hardening phenomenon based on the non-associated flow rules and studies the anisotropy of 7075-O aluminum alloy. The mechanical response of 7075-O aluminum alloy in three different directions was obtained through tensile tests, and the metal hardening was described with the Swift-Voce hardening criterion. As shown by the results, 7075-O aluminum alloy exhibits certain plastic anisotropy. The anisotropic evolution of 7075-O aluminum alloy was presented accurately with SY2009 model. Finite element simulation and comparison were conducted for the tensile tests of 7075-O aluminum alloy with Abaqus based on the VUMAT subroutine. It has been proved by the results that simulated values of the SY2009 hardening model match the experimental curve with high accuracy. In addition, this method was used to predict the performance of lugs by 7075-O aluminum-alloy circular cup deep drawing, and the results demonstrated that this method can be used to accurately predict the position and height of lugs. Therefore, the SY2009 model has important guiding significance for the production of metal sheets. © 2024, The Authors. All rights reserved.

关键词： Aluminum alloys

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Ultralow Thermal Conductivity of Single-Atom Doped Carbon Aerogel Synthesized with a Facile Ambient-Pressure-Drying Strategy

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SSRN 2023年

作者： Luo, Yi Yu, Linfeng Men, Jing Feng, Junzong Jiang, Yonggang Li, Liangjun Qin, Guangzhao Feng, Jian Science and Technology on Advanced Ceramic Fibers and Composites Laboratory College of Aerospace Science and Engineering National University of Defense Technology Changsha410073 China State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body College of Mechanical and Vehicle Engineering Hunan University Changsha410082 China

Carbon aerogel is an attractive material for thermal insulation due to the porous character and high stability at high temperature. However, the wide application of carbon aerogel for thermal insulation is hindered by supercritical-drying technology and high thermal conductivity of the pure carbon skeleton. Herein, a facile ambient-pressure-drying technology is developed for synthesizing Fe-N4 doped carbon aerogel through catalyzing the polymerization reaction of monomers under a Fe sol, with copolymer F127 as enhancement phase for wet-hydrogel. The prepared carbon aerogel has an ultralow thermal conductivity of 0.048 W/ (m ∙ K) at room temperature, with negligible 2% shrinkage during ambient-pressure-drying process and excellent mechanical behavior with stress of 0.58 MPa at 10% strain. The thermal conductivity of carbon-fiber reinforcement carbon aerogel is 0.158 W/ (m ∙ K) at 1100 °C, and has an elasticity modulus of 108.3 MPa. Based on an ideal model, density functional theory calculations reveal that doping Fe-N4 can significantly enhance the anharmonicity of carbon-based materials and thus reduce the lattice thermal conductivity by more than 10 times. This work presents a facile and low-cost method for synthesizing carbon aerogel with single-atom doping for promising applications in thermal insulation. © 2023, The Authors. All rights reserved.

关键词： Density functional theory

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