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Microstructure transformations and improving wear resistance of austenitic stainless steel additively fabricated by arc-based DED process

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Defence Technology（防务技术） 2024年第8期38卷 194-204页

作者： Ashish Yadav Manu Srivastava Prashant K.Jain Sandeep Rathee Hybrid Additive manufacturing Laboratory Mechanical Engineering DepartmentPDPM Indian Institute of Information TechnologyDesign&ManufacturingJabalpur482005Madhya PradeshIndia FFF Laboratory Mechanical Engineering DepartmentPDPM Indian Institute of Information TechnologyDesign&ManufacturingJabalpur482005Madhya PradeshIndia Department of mechanical Engineering National Institute of TechnologySrinagarIndia

In this study, austenitic stainless steel(ASS) was additively fabricated by an arc-based direct energy deposition(DED) technique. Macrostructure, microstructure, mechanical characteristics at different spatial orientations(0°, 90°, and 45°), and wear characteristics were evaluated at the deposited structure top, middle, and bottom regions. Results show that austenite(γ) and delta-ferrite(δ) phases make up most of the microstructure of additively fabricated SS316LSi steel. Within γ matrix, δ phase is dispersed both(within and along) grain boundaries, exhibiting a fine vermicular morphology. The bottom, middle,and top regions of WAAM deposited ASS exhibit similar values to those of wrought SS316L in the tensile and impact test findings. Notably, a drop in hardness values is observed as build height increases. During SEM examinations of fractured surfaces from tensile specimen, closed dimples were observed, indicating good ductility of as-built structure. Wear test findings show signs of mild oxidation and usual adhesive wear. By depositing a mechanically mixed composite layer, an increase in the oxidation percentage was discovered to facilitate healing of worn surfaces. The findings of this study will help in design, production and renovation of products/components that are prone to wear. WAAM-deposited ASS has remarkable strength and ability to withstand impacts;it can be used in the production of armour plates for defence applications, mainly military vehicles and aircraft.

关键词： Metal additive deposition Defence applications Arc-based DED Characterization Wear behaviour Fractography

Spectrum analysis of interval process model and its application in uncertain vibration analysis

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Science China(Technological Sciences) 2024年第8期67卷 2549-2564页

作者： LI JinWu JIANG Chao NI BingYu State Key Laboratory of Advanced design and manufacturing Technology for Vehicle College of Mechanical and Vehicle EngineeringHunan UniversityChangsha 410082China

In recent years, the authors have extended the traditional interval method into the time dimension to develop a new mathematical tool called the “interval process model” for quantifying time-varying or dynamic uncertainties. This model employs upper and lower bounds instead of precise probability distributions to quantify uncertainty in a parameter at any given time point. It is anticipated to complement the conventional stochastic process model in the coming years owing to its relatively low dependence on experimental samples and ease of understanding for engineers. Building on our previous work, this paper proposes a spectrum analysis method to describe the frequency domain characteristics of an interval process, further strengthening the theoretical foundation of the interval process model and enhancing its applicability for complex engineering problems. In this approach, we first define the zero midpoint function interval process and its auto/cross-power spectral density(PSD) functions. We also deduce the relationship between the auto-PSD function and the auto-covariance function of the stationary zero midpoint function interval process. Next, the auto/cross-PSD function matrices of a general interval process are defined, followed by the introduction of the concepts of PSD function matrix and cross-PSD function matrix for interval process vectors. The spectrum analysis method is then applied to random vibration problems, leading to the creation of a spectrum-analysis-based interval vibration analysis method that determines the PSD function for the system displacement response under stationary interval process excitations. Finally, the effectiveness of the formulated spectrum-analysis-based interval vibration analysis approach is verified through two numerical examples.

关键词： interval process spectrum analysis power spectral density(PSD) time-varying uncertainty uncertain vibration analysis

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Elastic three-dimensional phononic topological insulators with Dirac hierarchy

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Science China(Physics,Mechanics & Astronomy) 2024年第5期67卷 54-62页

作者： Shao-Yong Huo Qiu-Shuang Yang Jiu-Jiu Chen Hong-Kang Li Long-Chao Yao Fu-Chun He Chun-Ming Fu College of mechanical Engineering University of South ChinaHengyang 421001China State Key Laboratory of Advanced design and manufacturing for Vehicle Body College of Mechanical and Vehicle EngineeringHunan UniversityChangsha 410082China

Three-dimensional(3D)phononic topological insulators(TIs)featuring two-dimensional(2D)surface states and one-dimensional(1D)hinge states have opened up a new route for multi-dimensional robust wave transport,providing unprecedented methods for integrated acoustic sensors and energy harvesting ***,aiming at the elastic 3D phononic TI with gapless surface states and hinge states,the realization of elastic 3D phononic TIs with gapless surface states and hinge states is a significant challenge due to the complicated multi-mode polarization of elastic waves in 3D *** this study,we demonstrate an elastic 3D phononic TI with a Dirac hierarchy by elaborately operating the corresponding spatial symmetries of the chiral honeycomb ***,a 3D double Dirac cone of elastic wave can be achieved by doubling the lattice along the outof-plane direction to fold two iso-frequency Weyl *** topological phase transitions and 2D gapless two-fold Dirac surface states of elastic wave are realized by breaking the half-lattice spatial translation ***,based on the Brillouin zone folding along the in-plane direction,the 2D gapless two-fold surface Dirac cones are folded into four-fold surface Dirac ***,by inducing the relative radius of adjacent holes to break the in-plane spatial inversion symmetry,the fourfold surface Dirac cones are gapped and associated with a surface state inversion,in which the gapless 1D hinge Dirac dispersion is *** research offers a route for engineering the hierarchies of TIs in 3D elastic wave systems and provides new possibilities for designing 3D ultrasonic devices with unconventional functions.

关键词： Dirac topological hierarchy

Path Tracking Controller design of Automated Parking Systems via NMPC with an Instructible Solution

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Chinese Journal of mechanical Engineering 2024年第3期37卷 353-367页

作者： Liang Chen Zhaobo Qin Manjiang Hu Yougang Bian Xiaoyan Peng State Key Laboratory of Advanced design and manufacturing Technology for Vehicle College of Mechanical and Vehicle EngineeringHunan UniversityChangsha 410082China Wuxi Intelligent Control Research institute of Hunan University Wuxi 214115China

Parking difficulties have become a social issue that people have to *** parking system is practicable for quick par operations without a driver which can also greatly reduces the probability of parking *** paper proposes a Lyapunov-based nonlinear model predictive controller embedding an instructable solution which is generated by the modified rear-wheel feedback method(RF-LNMPC)in order to improve the overall path tracking accuracy in parking ***,A discrete-time RF-LNMPC considering the position and attitude of the parking vehicle is proposed to increase the success rate of automated parking ***,the RF-LNMPC problem with a multi-objective cost function is solved by the Interior-Point Optimization,of which the iterative initial values are described as the instructable solutions calculated by combining modified rear-wheel feedback to improve the performance of local optimal ***,the details on the computation of the terminal constraint and terminal cost for the linear time-varying case is *** closed-loop stability is verified via Lyapunov techniques by considering the terminal constraint and terminal cost ***,the proposed RF-LNMPC is implemented on a selfdriving Lincoln MKZ platform and the experiment results have shown improved performance in parallel and vertical parking *** Monte Carlo analysis also demonstrates good stability and repeatability of the proposed method which can be applied in practical use in the near future.

关键词： Automated parking Path tracking controller Nonlinear model predictive control Monte Carlo analysis

Surface roughness classification using light scattering matrix and deep learning

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Science China(Technological Sciences) 2024年第2期67卷 520-535页

作者： SUN Hao TAN Wei RUAN YiXiao BAI Long XU JianFeng State Key Laboratory of Intelligent manufacturing Equipment and Technology School of Mechanical Science and EngineeringHuazhong University of Science and TechnologyWuhan 430074China Wuhan Digital design and manufacturing Innovation Center Co. LtdWuhan 430074China

High-quality optical components have been widely used in various applications;thus,extremely high beam quality is ***,surface roughness is a key indicator of the surface *** this study,the angular distribution of light scattering field intensity was obtained for surfaces having different roughness profiles based on the finite difference time domain(FDTD)method,and the results were compared with those obtained using the generalized Harvey-Shack(GHS)*** was shown that the FDTD approach can be used for an accurate simulation of the scattered field of a rough surface,and the superposition of results obtained from many surfaces that have the same roughness level was in good agreement with the result given by the analytic GHS model.A light scattering matrix(LSM)method was proposed based on the FDTD simulation results that could obtain rich surface roughness *** classification effect of LSM was compared with that of the single-incidence scattering distribution(SISD)based on a ResNet-50 deep learning *** classification accuracy of the model trained with the LSM dataset was obtained as 95.74%,which was 23.40%higher than that trained using the SISD ***,the effects of different noise types and filtering methods on the classification performance were analyzed,and the LSM was also shown to improve the robustness and generalizability of the trained surface roughness ***,the proposed LSM method has important implications for improving the data acquisition scheme of current light scattering measurement systems,and it also has the potential to be used for detection and characterization of surface defects of optical components.

关键词： surface roughness FDTD simulation GHS theory deep learning light scattering matrix

Safe Efficient Policy Optimization Algorithm for Unsignalized Intersection Navigation

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IEEE/CAA Journal of Automatica Sinica 2024年第9期11卷 2011-2026页

作者： Xiaolong Chen Biao Xu Manjiang Hu Yougang Bian Yang Li Xin Xu State Key Laboratory of Advanced design and manufacturing for Vehicle Body the College of Mechanical and Vehicle EngineeringHunan UniversityChangsha 410082China State Key Laboratory of Advanced design and manufacturing for Vehicle Body the College of Mechanical and Vehicle EngineeringHunan UniversityChangsha 410082 Wuxi Intelligent Control Research institute(WICRI)of Hunan University Wuxi 214115China College of Intelligence Science and Technology Institute of Unmanned SystemsNational University of Defense TechnologyChangsha 410073China

Unsignalized intersections pose a challenge for autonomous vehicles that must decide how to navigate them safely and *** paper proposes a reinforcement learning(RL)method for autonomous vehicles to navigate unsignalized intersections safely and *** method uses a semantic scene representation to handle variable numbers of vehicles and a universal reward function to facilitate stable learning.A collision risk function is designed to penalize unsafe actions and guide the agent to avoid them.A scalable policy optimization algorithm is introduced to improve data efficiency and safety for vehicle learning at *** algorithm employs experience replay to overcome the on-policy limitation of proximal policy optimization and incorporates the collision risk constraint into the policy optimization *** proposed safe RL algorithm can balance the trade-off between vehicle traffic safety and policy learning *** intersection scenarios with different traffic situations are used to test the algorithm and demonstrate its high success rates and low collision rates under different traffic *** algorithm shows the potential of RL for enhancing the safety and reliability of autonomous driving systems at unsignalized intersections.

关键词： Autonomous driving decision-making reinforcement learning(RL) unsignalized intersection

Digital Twin Modeling Enabled Machine Tool Intelligence:A Review

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Chinese Journal of mechanical Engineering 2024年第2期37卷 29-54页

作者： Lei Zhang Jianhua Liu Cunbo Zhuang School of mechanical Engineering Tianjin University of CommerceTianjin 300134China Laboratory of Digital manufacturing School of Mechanical EngineeringBeijing Institute of TechnologyBeijing 10081China

Machine tools,often referred to as the“mother machines”of the manufacturing industry,are crucial in developing smart manufacturing and are increasingly becoming more *** twin technology can promote machine tool intelligence and has attracted considerable research ***,there is a lack of clear and systematic analyses on how the digital twin technology enables machine tool ***,digital twin modeling was identified as an enabling technology for machine tool intelligence based on a comparative study of the characteristics of machine tool intelligence and digital *** review then delves into state-of-the-art digital twin modelingenabled machine tool intelligence,examining it from the aspects of data-based modeling and mechanism-data dual-driven ***,it highlights three bottleneck issues facing the *** these problems,the architecture of a digital twin machine tool(DTMT)is proposed,and three key technologies are expounded in detail:Data perception and fusion technology,mechanism-data-knowledge hybrid-driven digital twin modeling and virtual-real synchronization technology,and dynamic optimization and collaborative control technology for multilevel ***,future research directions for the DTMT are *** work can provide a foundation basis for the research and implementation of digital-twin modeling-enabled machine tool intelligence,making it significant for developing intelligent machine tools.

关键词： Machine tool Digital twin Smart manufacturing Synchronization

Robust boundary-induced bulk propagations in elastic waveguides with nonplanar surfaces

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Science China(Physics,Mechanics & Astronomy) 2024年第4期67卷 88-96页

作者： Baizhan Xia Jielong Zhang Zihan Jiang Jianting Liu State Key Laboratory of Advanced design and manufacturing for Vehicle Body Hunan UniversityChangsha 410082China College of mechanical and Vehicle Engineering Hunan UniversityChangsha 410082China

Trivial elastic waveguides induced by line defects and nontrivial elastic waveguides protected by topological edge states have been extensively examined in planar waveguide *** these investigations,little is known about topologically protected bulk states and their resulting robust transmission properties,especially in nonplanar elastic waveguides with folded,curved,and twisted *** Dirac waveguides with robust boundary-induced bulk states are *** states arise from the truncated boundaries of bulks with linear Dirac conical dispersions,differing from topologically protected edge states ensured by the bulk-edge *** proof is provided,in which boundary-induced bulk states show robustly high-throughput transmissions along the waveguides,even with folded,curved,and twisted *** results not only open up new avenues for examining novel topological phenomena about bulk but also offer new platforms for developing topological devices with nonplanar surfaces.

关键词： elastic waveguides boundary-induced bulk propagations Dirac conical dispersions nonplanar surfaces

Effect of Y_(2)O_(3) on microstructure and properties of CoCrFeNiTiNb high entropy alloy coating on Ti-6Al-4V surface by laser cladding

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Journal of Rare Earths 2024年第3期42卷 586-599,I0006页

作者： Zhen Li Wei Zhao Kedong Yu Ning Guo Guangchun Xiao Zhiming Wang Hui Zhang College of mechanical Engineering Qilu University of Technology(Shandong Academy of Sciences)Jinan250353China Shandong institute of mechanical design and Research Jinan250031China

The effects of Y_(2)O_(3) on the microstructure, microhardness, wear resistance, high-temperature oxidation resistance, hot corrosion resistance, and electrochemical corrosion behaviour of CoCrFeNiTiNb high entropy alloy coatings formed on Ti-6Al-4V alloy surfaces were studied. The results show that the addition of Y_(2)O_(3) changes the proportion of the phase but does not change its type. The average grain size is only 1/4.7 of that of the high entropy alloy(HEA) coating, and the fine-grained strengthening leads to increases in the microhardness and wear resistance of 21.8% and 26.9%, respectively. The addition of Y_(2)O_(3) enhances the denseness and bonding properties of the oxide and corrosion product layers, reducing the oxidation and hot corrosion rates by 60.3% and 40.3%, respectively. The addition of Y_(2)O_(3) doubles the corrosion resistance which is attributed to the refinement of the grains, the increased proportion of HCP and TiN, and the weakening of galvanic coupling corrosion.

关键词： Laser cladding High entropy alloy coatings Rare earths Wear properties High temperature properties Electrochemical corrosion