期刊：
Multiscale and Multidisciplinary Modeling, Experiments and Design,2024年:1-10 ISSN：2520-8160
通讯作者：
Dandan Song
作者机构：
[Tao Yang] Henan Communication Vocational and Technical College, Institute of Automobile Engineering, Zhengzhou, China;College of Automobile and Mechanical Engineering, Changsha University of Science Technology, Changsha, China;[Dandan Song] Henan Communication Vocational and Technical College, Institute of Automobile Engineering, Zhengzhou, China<&wdkj&>College of Automobile and Mechanical Engineering, Changsha University of Science Technology, Changsha, China
通讯机构：
[Dandan Song] H;Henan Communication Vocational and Technical College, Institute of Automobile Engineering, Zhengzhou, China<&wdkj&>College of Automobile and Mechanical Engineering, Changsha University of Science Technology, Changsha, China
摘要：
Considering natural stochastic power fluctuation as well as existing of fast varying local loads, power quality and stability problems are unavoidable in low-voltage microgrid power systems, especially in isolated operating modes. The main goal of this research is to design a power management system based on a wavelet filter, in which the frequency components of excess power, i.e., the difference between the generated power and the consumed power, are separated from each other and the high-frequency components are assigned to the supercapacitor and the low-frequency components to the battery. Using this method, the supercapacitor has the most effective performance in the hybrid energy storage system, which reduces the fluctuation of the battery charge level and increases its lifespan. For this purpose, two optimized PI controllers are used to make batteries and supercapacitors to store generated reference currents by the proposed energy management system. In this regard, the coefficients of the PI controllers have been optimized using the grey wolf optimization method. The proposed algorithm examined in the case study hybrid DC-microgrid system in Simulink/Matlab. The simulation results confirm that the proposed supervisory algorithm improves the microgrid dynamic and static performance under different operating conditions.
摘要：
The dynamic response description of materials in high-speed impact fields is of practical significance to structural design and practical engineering application. In this paper, an electromagnetic impact (EI) loading process was proposed to acquire dynamic stress-strain relationships of 2A10 aluminum alloys. A modified Johnson-Cook (J-C) material model was obtained by combining with Quasi-static experiments and verified by numerical simulations. Comparing the J-C model obtained by a Split Hopkinson pressure bar, the simulative results about maximum deformation displacements showed the modified J-C model was more in line with actual experimental results. The accuracy under the discharge energy of 4 and 5 kJ was improved by 50% and 11%, respectively. In addition, electromagnetic impact loading characteristics and microstructure evolution of materials were studied. The discharge current with an attenuated sine wave caused that electromagnetic impact forces demonstrated a bimodal trend. The maximum impact velocities reached up to 4.7 m/s and 6.7 m/s under the discharge energy of 4 and 5 kJ, respectively (the maximum strain rates are 655.0 and 932.3 s-1, respectively). The high-speed impact effect led to the emergence of adiabatic shear bands (ASBs) during deformation microstructure evolution. Due to higher impact speed, the deformation concentration degree was more remarkable under the energy of 5 kJ.
摘要：
Porous structures have attracted much attention because of the advantages of lightweight and strong energy absorption efficiency. This work proposes a spherical porous structure (SPS) and a square porous structure (SQPS), and the SPS sample is manufactured by selective laser sintering (SLS) technique with the material nylon 11. Their axial compression results of experiment and simulation show that the compressive strength of hollow cylinders is greater than that of porous spheres, and porous spheres are always crushed during compression. SPS exhibits the rapid collapse characteristics of porous spheres layer by layer, and it shows four sharp valley forces and significant negative stiffness characteristic. In addition, the specific energy absorption (SEA) value of SPS is higher than that of SQPS 30.84%. The compression capacity of porous spheres is stronger than that of porous cubes. This study furtherly discuss the mechanical behavior of SPS with different structural parameters. The negative stiffness characteristic, energy absorption efficiency and deformation mode of SPS depends on the strength combination of porous spheres and hollow cylinders, and smaller overall cell size, more cell layers, and thicker cells contribute to improving the anti-compression properties of SPS. The SEA values of SPS- T1.6 and SPS- F7 are 12.52% and 12.16% higher than that of SPS. In summary, SPS shows novel mechanical properties, providing a reference for the design of new energy absorbers.
摘要：
Combined with the convolutional neural network (CNN) model, an intelligent structural reliability analysis method based on evidence theory is developed to improve the accuracy and efficiency of reliability analysis. Firstly, the uncertainties in engineering structures are described by the Frame of Discernment (FD) and the Basic Probability Assignment (BPA). Secondly, the Optimal Latin Hypercube Design (OLHD) is adopted to obtain the sample focal elements and the Sequential Quadratic Programming (SQP) method is utilized to carry out the extremum analysis of the sample focal elements. Thirdly, the sample focal elements can be reclassified as the belief focal element, the intersect focal element and the failure focal element. Fourthly, the local-densifying method of sample space is applied to ensure the uniformity of sample focal elements and the convolution neural network model is trained by these focal elements. Then, the classifications of the undetermined focal elements could be obtained by the convolution neural network model and the confidence interval can be obtained based on the classification results of all focal elements. Finally, two numerical examples and one engineering application are introduced to investigate the effectiveness of the proposed method.
摘要：
The diverse folding motion of the origami structures induces a series of extraordinary properties, which enriches their application prospects in engineering. In this paper, we propose a class of open-section origami tubes with multiple extraordinary mechanical properties, and explore their potential applications. First, three types of origami tubes with one degree of freedom are developed. Their motion patterns are studied through the kinematic analysis, which induces several extraordinary mechanical properties. The Poisson's ratio of the proposed structure undergoes multiple sign-flipping, which can be tuned by the geometric parameters of panels. Also, the origami tubes exhibit multiple mechanical properties under compression such as mono/bistable and zero stiffness mode, which can be tuned by the rotational stiffness assignment of the creases. The self-locking behavior of the tandem origami tubes is also discussed, which shows the remarkable programmability on the number and position of locking. Based on the proposed origami cells, the piecewise-stiffness structure and quasi-zero-stiffness structure are constructed, and their performance is verified through the prototype tests.
摘要：
In this paper, a high-accuracy measurement method for rotor-stator axial clearance in narrow spaces is proposed. The optical path structure based on all-fiber microwave photonic mixing is established. To improve the accuracy and expand the measurement range, the total coupling efficiency over the entire measurement range at different working distances of fiber probe was evaluated by Zemax analysis tool and theoretical model. The performance of the system was verified by experiments. The experimental results show that the measurement accuracy of axial clearance is better than 10.5 um within the range of 0.5–20.5 mm. The measurement accuracy has been effectively improved compared to previous methods. Additionally, the probe size is reduced to a mere diameter of 2.78 mm, which is more suitable for axial clearance measurement in narrow spaces inside rotating machines.
摘要：
In-situ additive manufacturing (AM) is well known for integrating of material synthesis and near-shaping fabrication. However, the insufficient metallurgy has become a widespread challenge owing to the molten pool's short lifetime. Our previous research proved that employing alternating dual-electron beams can effectively manipulate the molten pool length, thereby prolonging its duration time. However, it is difficult for the preset alternating dual-heat source parameters under current open-loop operations to guarantee the desired molten pool length for the time-variation of the AM process. Therefore, this study further proposes a closed-loop control of alternating dual-electron beams to maintain a stable molten length, thereby ensuring internal metallurgical quality and external forming morphology. Specifically, based on a self-developed atmospheric pressure vapor-prevention visual sensor, a machine-vision closed-loop control system for the molten pool length was established. The influence of the alternating dual-beam parameters on the molten pool length was studied and modeled, and the deflection voltage was selected as the controlled variable owing to its good dynamic performance and wide manipulation range. Given the nonlinearity and time variance of the AM process, a FuzzyPID controller with the ability to adjust control parameters in real-time was designed. The experimental verification results indicated that the developed controller could effectively control the molten pool to the expected length and exhibited good robustness in the disturbance test. Finally, a multi-layer multi-pass component was successfully fabricated with a closed-loop-controlled molten pool length of 24 mm. This study significant for promoting the industrial application and intelligent development of in-situ AM technology.
关键词：
Mg-RE alloy;Hot tensile deformation;Microstructure;Fracture damage model
摘要：
Hot tensile tests are employed herein to explore the microstructural evolution and fracture damage of a hot-extruded Mg-9.1Y-1.8Zn (wt%) alloy at deformation temperatures of 250-400 degrees C and strain rates of 0.005-0.1 s(-1). The deformed microstructure and fracture morphology are systematically studied using electron backscatter diffraction (EBSD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The flow stress tends to decline with increasing tensile temperature or decreasing strain rate. Under all the tested conditions, discontinuous dynamic recrystallization (DDRX) is characterized by a bulged grain boundary and plays a critical role. Particle-stimulated nucleation (PSN) induced by the twisted long-period stacking ordered structure (LPSO) is another essential nucleation mechanism for DRX, especially at low strain rates. Since DRX is more straightforward at high temperatures, the fracture mechanism can be easily observed to change from intergranular to transcrystalline at tensile temperatures exceeding 250 degrees C. However, the effects of strain rate on the fracture mechanism seem inconspicuous at strains rates of 0.005-0.1 s(-1). Based on the Oyane-Sato criterion, a fracture damage model is established based on the experimental and numerically simulated results. The results signify that the developed damage model can accurately forecast fracture damage during hot tensile deformation, which is valuable for optimizing the hot forming processing of the tested Mg-RE alloy.
关键词：
科教融合;创新复合型人才;人才培养模式Integration of Science and Education
摘要：
Abstract: China has entered a new journey of comprehensively building a socialist modernized country and marching towards the new goal of the second hundred years’ struggle, and the cultivation of talents should insist on facing the frontiers of science and technology in the world, facing the main battlefield of the economy, facing the major needs of the country, and facing the life and health of the people. Cultivating innovative and complex talents has become an important talent cultivation goal of higher education institutions. The synergistic development of scientific research and teaching is an important path to cultivate innovative and complex talents. Based on the concept of science and education integration, the paper explores the innovative and complex talent cultivation mode of enhancing scientific research ability and innovative practice ability by “discipline competition”, and improving general knowledge ability and comprehensive quality by “artisanal academy” of the academy system.#@#@#摘要: 我国进入了全面建设社会主义现代化国家、向第二个百年奋斗新目标进军的新征程，人才培养要坚持面向世界科技前沿、面向经济主战场、面向国家重大需求、面向人民生命健康。培养创新复合型人才已然成为高等院校重要的人才培养目标。科研与教学协同发展是培养创新复合型人才的重要路径。文章基于科教融合的育人理念，探索以“学科竞赛”提升科研能力和创新实践能力，以书院制“匠心学堂”提高通识能力和综合素质的创新复合型人才培养模式。
摘要：
Cyclists are vulnerable road users and often suffer head-neck injuries in car-cyclist accidents. Wearing a helmet is currently the most prevalent protection method against such injuries. Today, there is an ongoing debate about the ability of helmets to protect the cyclists' head-neck from injury. In the current study, we numerically reconstructed five real-world car-cyclist impact accidents, incorporating previously developed finite element models of four cyclist helmets to evaluate their protective performances. We made comparative head-neck injury predictions for unhelmeted and helmeted cyclists. The results show that helmets could clearly lower the risk of severe (AIS 4+) brain injury and skull fracture, as assessed by the predicted head injury criterion (HIC), while a relatively limited decrease in AIS 4+ brain injury risk can be achieved in terms of the analysis of CSDM0.25. Assessment using the maximum principal strain (MPS0.98) and head impact power (HIP) criteria suggests that helmets could lower the risk of diffuse axonal injury and subdural hematoma of the cyclist. The helmet efficacy in neck protection depends on the impact scenario. Therefore, wearing a helmet does not seem to cause a significant neck injury risk level increase to the cyclist. Our work presents important insights into the helmet's efficacy in protecting the head-neck of cyclists and motivates further optimization of protective equipment.
通讯机构：
[Zhe Wang] S;[Yonggang Tong] C;School of Foreign Studies, Changsha University of Science and Technology, Changsha 410114, China<&wdkj&>College of Automotive and Mechanical Engineering, Changsha University of Science and Technology, Changsha 410114, China<&wdkj&>Hunan Provincial Key Laboratory of Safety Design and Reliability Technology for Engineering vehicles, Changsha University of Science and Technology, Changsha 410114, China
摘要：
The single-phase TiNbZrMox (x = 0, 0.3, 0.5, 0.7, 1) high-entropy alloys (HEAs) were prepared by arc melting. The relation between molybdenum, microstructure, mechanical properties and wear resistance was investigated by X-ray diffractometer (XRD), scanning electron microscope (SEM), universal tensile tester, hardness tester, friction tester, and wear tester. The results showed that TiNbZrMox alloys were composed of a single BCC phase. With the increase of Mo elements, the crystallite size of the as-cast alloy decreased first and then increased, both the alloy strength and hardness were increased and compressive strain plasticity was decreased. TiNbZrMo0.5 has the best comprehensive performance with a yield strength of 1.0 GPa, compressive strength of 1.3 GPa, and hardness of 429 HV; compared with TiNbZrMo0, yield strength increased by 77.32%, compressive strength increased by 25.14%, and hardness increased by 70.24%; and its specific wear rate decreased by 50%, while it's compressive plasticity only decreased by 5%. (C) 2022 Elsevier B.V. All rights reserved.
作者机构：
[Hu, Yongle; Ji, Xixi; Tong, Yonggang; Wang, Kaiming; Zhang, Hao; Ren, Ziyi; Fang, Jingzhong] Changsha Univ Sci & Technol, Coll Automot & Mech Engn, Changsha 410114, Peoples R China.;[Yang, Lingwei] China Aerodynam Res & Dev Ctr, Hyperveloc Aerodynam Inst, Mianyang 621000, Peoples R China.;[Chen, Hui] Changsha Univ Sci & Technol, Sch Civil Engn, Changsha 410111, Peoples R China.;[Liang, Xiubing] Acad Mil Sci PLA China, Natl Inst Def Technol Innovat, Beijing 100072, Peoples R China.
通讯机构：
[Yonggang Tong] C;[Xiubing Liang] N;College of Automotive and Mechanical Engineering, Changsha University of Science and Technology, Changsha 410114, China<&wdkj&>National Institute of Defense Technology Innovation, Academy of Military Science PLA China, Beijing 100072, China
摘要：
Normal strengthening methods through precipitations and deformation obviously enhance the strength of metallic materials while resulting in the sacrifice of ductility, and synergistic improvement of strength and ductility is currently an urgent requirement. Herein we developed a cryogenic deformation combined with an annealing method to fabricate CoCrNiMo0.2 medium entropy alloy, which achieved an ultrahigh strength of 1.8 GPa with synergistic improvement in strength and ductility. Microstructure, mechanical performance, and strengthening mechanisms of the developed alloys were investigated compared with that prepared by the regular room temperature deformation method. It was found that high-density nan-otwins were produced in CoCrNiMo0.2 MEA via cryogenic deformation. Fine grains, hard precipitations, and high volume fraction of nanotwins greatly strengthened the alloy, obtaining a yield and ultimate tensile strength of 1400 MPa and 1800 MPa. Ductility improvement of the developed alloy was mainly attributed to the production of deformation nanotwins due to the lower stacking fault energy, which greatly increases the dislocation storage ability, and thus, the ductility of the alloy was enhanced.(c) 2023 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.
关键词：
Introduction;Materials and Methods;Results;Discussion;Conclusion;Abstract;Data Availability;Additional Points;Ethical Approval;Consent;Disclosure;Conflicts of Interests;Authors’ Contributions;Funding Statement;Acknowledgements;Acknowledgments;Supplementary Materials;Reference;Dataset Description;Dataset Files;Abstract;Introduction;Introduction and Materials;Introduction and Methods;Materials;Materials and Methods;Methods;Results;Discussion;Results and Discussion;Discussion and Conclusion;Results and Conclusion;Conclusion;Conclusions;Data Availability;Additional Points;Ethical Approval;Consent;Disclosure;Conflicts of Interest;Authors’ Contributions;Funding Statement;Acknowledgements;Supplementary Materials;References;Appendix;Abbreviations;Preliminaries;Introduction and Preliminaries;Notation;Proof of Theorem;Proofs;Analysis of Results;Examples;Numerical Example;Applications;Numerical Simulation;Model;Model Formulation;Systematic Palaeontology;Nomenclatural Acts;Taxonomic Implications;Experimental;Synthesis;Overview;Characterization;Background;Experimental;Theories;Calculations;Model Verification;Model Implementation;Geographic location;Study Area;Geological setting;Data Collection;Field Testing;Data and Sampling;Dataset;Literature Review;Related Works;Related Work;System Model;Methods and Data;Experimental Results;Results and Analysis;Evaluation;Implementation;Case Presentation;Case Report;Search Terms;Case Description;Case Series;Background;Limitations;Additional Points;Case;Case 1;Case 2 etc.;Concern Details;Retraction Details;Copyright;Related Articles
摘要：
As the emergence of the connected and autonomous vehicles (CAVs), the platooning technology is believed to play a key role in the future intelligent transportation system. However, current studies mainly focus on the beneficial sides of CAV platoons, and less attention is given to their negative effects. This study develops a mixed equilibrium model for CAV platoons and human-driven vehicles (HDVs), which consider both the positive and negative sides of CAV platooning. On the positive side, CAV platoons are assumed to follow user equilibrium (UE) route choice for their information advantages, while HDVs to follow stochastic user equilibrium (SUE). CAV platoons are also presumed to improve the road capacity. On the negative side, the speed of CAV platoons is slower than that of HDVs for safety stakes, which will impede the latter to overtake. The HDVs is split up into overtaking and nonovertaking flows with different speeds. Furthermore, the model is built up as a mixed UE-SUE equilibrium problem and reformulated as a nonlinear complementarity problem. In addition, an optimal path platooning method is proposed to reduce the negative effects, by integrating travel costs of both CAV platoons and HDVs into its objective function. Numerical results show that the introduction of CAV platoons may increase the travel cost at the initial stage, and the proposed method can effectively reduce the platooning disturbance, thus helps promoting the wider applications of CAV platoons.
