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Anisotropic tensile properties and high-cycle fatigue behavior of Ti6Al4V fabricated by single and dual laser-powder bed fusion

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Materials Science and Engineering: A 2025年 941卷

作者： Guotai Li Peichen Hu Yuzhan Fan Ming Wu Mingjun Chen Tianyu Yu State Key Laboratory of Robotics and System Harbin Institute of Technology Harbin Heilongjiang 150001 China Key Laboratory of Micro-systems and Micro-structures Manufacturing Ministry of Education Harbin Heilongjiang 150001 China Department of Computer Science KU Leuven 3001 Leuven Belgium Department of Mechanical Engineering KU Leuven 3001 Leuven Belgium

The development of multi laser-powder bed fusion (PBF) technology has significantly reduced the production time for large engine components. However, the impact of thermal effects and microstructural characteristics in the laser beam overlap region on the anisotropic mechanical behavior of metallic materials remains unclear. This study investigated the anisotropic tensile properties and high-cycle fatigue behavior of Ti6Al4V produced by both single laser-PBF (SL-PBF) and dual laser-PBF (DL-PBF). As-built DL-PBF samples exhibited high strength (1404 MPa) but low ductility (3.6 %). After heat treatment, the samples achieved a strength-ductility balance, with an ultimate tensile strength of 1089 MPa, and an elongation of 17.1 %. The mechanical properties of Ti6Al4V produced by DL-PBF were influenced by the α lath thickness, dislocation density and texture. The precipitation of small-angle grain boundaries during DL-PBF process was found to contribute to the strong anisotropy. Due to the influence of internal pore forming, the fatigue strength of the DL-PBF samples was lower than that of the SL-PBF samples. Pores in the dual-laser beam overlap region accelerated the fatigue crack propagation, resulting in a venation-like pattern. In contrast, cracks in the SL-PBF samples propagated in a circular pattern around internal pore. A high-speed camera was employed to capture the dual-laser beams dynamics during pore formation. This study provides a comprehensive analysis of the mechanical properties and pore formation mechanisms in the DL-PBF process.

关键词： Anisotropy Dual laser-powder bed fusion High-cycle fatigue Tensile properties Ti6Al4V

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Tunable unidirectional compact acoustic amplifier via space-time modulated membranes

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Physical Review B 2020年第2期102卷 024309-024309页

作者： Xiaohui Zhu Junfei Li Chen Shen Guangyu Zhang Steven A. Cummer Longqiu Li State Key Laboratory of Robotics and System Harbin Institute of Technology Harbin Heilongjiang 150001 China Department of Electrical and Computer Engineering Duke University Durham North Carolina 27708 USA

Space-time modulation has recently attracted considerable attention as it enables new possibilities in wave manipulation and control. Here we propose a tunable unidirectional acoustic amplifier based on a space-time modulated membrane system. The transfer matrix method is applied to design this system and optimize the modulation parameters for the realization of unidirectional amplification. Efficient one-way amplification of acoustic waves is demonstrated theoretically and numerically within a frequency range from 2260 to 2520 Hz, with overall dimension being less than 1/3 of the corresponding wavelength. Across this operation band, the amplification factor in the positive direction varies smoothly from 3.0 to 5.8, while the transmitted wave energy in the negative direction does not change significantly. Our work identifies a feasible approach to realize a tunable unidirectional acoustic amplifier via space-time modulated membranes, which offers a design platform for a number of applications in sensing, imaging, and communication.

关键词： Acoustic metamaterials Acoustic wave phenomena Sound waves

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Formation mechanism of a smooth, defectfree surface of fused silica optics using rapid CO2 laser polishing

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International Journal of Extreme Manufacturing 2019年第3期1卷 85-95页

作者： Linjie Zhao Jian Cheng Mingjun Chen Xiaodong Yuan Wei Liao Qi Liu Hao Yang Haijun Wang State Key Laboratory of Robotics and System Harbin Institute of TechnologyHarbin 150001People’s Republic of China Research Center of Laser Fusion China Academy of Engineering PhysicsMianyang 621900People’s Republic of China

Surface defects introduced by conventional mechanical processing methods can induce irreversible damage and reduce the service life of optics applied in high-power *** to mechanical processing,laser polishing with moving beam spot is a noncontact processing method,which is able to form a defect-free *** work aims to explore the mechanism of forming a smooth,defect-free fused silica surface by high-power density laser polishing with coupled multiple *** underlying mechanisms of laser polishing was revealed by numerical simulations and the theoretical results were verified by *** simulated polishing depth and machined surface morphology were in close agreement with the experimental *** obtain the optimized polishing quality,the effects of laser polishing parameters(*** rate,pulse width and polishing times)on the polishing quality were experimentally *** was found that the processing efficiency of fused silica materials by carbon dioxide(CO2)laser polishing could reach 8.68 mm2 s−1,and the surface roughness(Ra)was better than 25 ***,the cracks on pristine fused silica surfaces introduced by initial grinding process were completely removed by laser polishing to achieve a defect-free *** maximum laser polishing rate can reach 3.88μm s−1,much higher than that of the traditional mechanical polishing *** rapid CO2 laser polishing can effectively achieve smooth,defect-free surface,which is of great significance to improve the surface quality of fused silica optics applied in high-power laser facilities.

关键词： laser polishing mechanical processing smooth surface defect-free surface polishing rate

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Time-Optimal Trajectory Planning Based on Dynamics for Industrial Robot

Time-Optimal Trajectory Planning Based on Dynamics for Indus...

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Automation, Control and robotics Engineering (CACRE), International Conference on

作者： Rundong Wang Minxiu Kong Yanchun Cheng Marco Castellani School of Mechatronics Engineering Harbin Institute of Technology State Key Laboratory of Robotics and System University of Birmingham Department of Mechanical Engineering

ISBN: (数字)9781728198880

ISBN: (纸本)9781728198897

Given the trajectory of the industrial robot in Cartesian space, the existing methods only consider the kinematic constraints when optimizing the time trajectory planning, and ignore the maximum driving ability of the motor, which is likely to cause an overrun alarm and greatly reduce the trajectory accuracy. Therefore, this paper studies the timeoptimal trajectory planning algorithm based on dynamics. Firstly, the algorithm discretizes the path, calculates the Cartesian coordinates of each discrete point and the differential about the path length. Then, this algorithm considers the constraints of dynamics and kinematics, uses the principle of linear programming, recursively calculates the upper limit value of speed and the maximum acceleration value at each discrete point, and calculates the speed value at each discrete point and keeps it within its allowable ranges. Finally, this algorithm uses the speed to calculate the corresponding time of each discrete point, and according to the interpolation period, outputs the path position of each period, the position and orientation in the Cartesian space and joint parameters. The MATLAB program is written to verify the feasibility and efficiency of the algorithm.

关键词： industrial robot trajectory planning time-optimal dynamics multiple constraints

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A disordered composite metamaterial beam optimized using NSGA-Ⅱ:a structure with an adjustable hybrid bandgap

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European Journal of Mechanics - A/Solids 2025年 114卷

作者： Wentao Wu Xiaobiao Shan Chenghui Sun Guangdong Sui Tianci Jiang Huan Zhang State Key Laboratory of Robotics and System Harbin Institute of Technology Harbin 150001 China Institute of Ultra-precision Optoelectronic Instrument Engineering Harbin Institute of Technology Science Park No.2 Yikuang Street Nangang District Harbin 150080 China

To address the limitations of conventional periodic metamaterials in regulation and optimization, this study introduces a novel staggered supercell beam configuration designed to enhance low-frequency vibration isolation. The proposed supercell beam is composed of single cells with varying staggered degrees and inductances. Initially, the transmission matrix method was employed to model both symmetrical and staggered structures, enabling the determination of their attenuation constant and transmission coefficient. Subsequently, the Non-dominated Sorting Genetic Algorithm II (NSGA-II) was implemented for multi-objective optimization to identify Pareto frontiers. Theoretical analysis demonstrated that the staggered beam exhibits a lower attenuation constant than its symmetrical counterpart and, critically, introduces a new coupling bandgap at low frequencies. Experimental transmission coefficient measurements confirmed that the optimized staggered beam achieves superior low-frequency vibration isolation performance compared to the symmetrical beam. This improvement is attributed to the successful application of NSGA-II, which effectively balances bandgap width and attenuation constant—a challenge previously unresolved in the field, as evidenced by studies that have explored the maximum limits of attenuation constants and the influence of parameters such as resistance, piezoelectric sheet thickness, and lattice constant length on bandgap characteristics. The findings of this study demonstrate that the proposed disordered staggered supercell beam configuration, optimized with NSGA-II, achieves superior bandgap attenuation, offering significant potential for advancements in low-frequency vibration isolation research.

关键词： Metamaterials

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The energy-saving advantages of burst-and-glide mode for thunniform swimming

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Journal of Hydrodynamics 2018年第6期30卷 1072-1082页

作者： Dan Xia Wei-shan Chen Jun-kao Liu Xiang Luo School of Mechanical Engineering Southeast University State Key Laboratory of Robotics and System Harbin Institute of Technology

This paper explores the energy-saving advantages of the burst-and-glide swimming and compares it with the normal self-swimming for a thunniform swimmer. The virtual swimmer allows us to perform controlled numerical experiments by varying the swinging tail number and the duty cycle while keeping the other parameters fixed. 3-D Navier-Stokes equations are used to compute the viscous flow over the swimmer. The user-defined functions and the dynamic mesh technology are used to simulate the burst-and-glide swimming. The results show that with the increase of the swinging tail number or the duty cycle, the swimming velocity, the power and the efficiency all increase, but the velocity-power ratio decreases somewhat. Therefore, choosing smaller swinging tail number and duty cycle is beneficial in reducing the power and increasing the velocity-power ratio, and thus to obtain the same velocity, less power is consumed. And to swim the same distance, the energy can significantly be saved. The power consumption, the efficiency and the velocity-power ratio in the burst-and-glide case are 43.9%, 40.6% and 1.15 times of those in the normal swimming case, respectively. The flow structures clearly show the evolution process around the fish in the burst-and-glide swimming. The findings can be used to reasonably plan the swimming action and to take the advantage of the external flow field energy for the fishlike robot, to be more efficient and energy-saving.

关键词： Energy-saving advantages burst-and-glide mode normal self-swimming thunniform swimmer

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Design of a close-range radiotherapy particle implantation device

Design of a close-range radiotherapy particle implantation d...

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2019 IEEE International Conference on robotics and Biomimetics, ROBIO 2019

作者： Ban, Guang Li, Changle Zhang, Xuehe Liu, Gangfeng Liu, Yubin Zhao, Jie Zhang, Leifeng Fan, Yilun State Key Laboratory of Robotics and System Harbin Institute of Technology Harbin 150080 NO. 2 YiKuang Street HeiLongJiang Province China

ISBN: (纸本)9781728163215

The validity of brachytherapy has been proved in clinical tumor treatment, and robotic surgery system has been used in recent years to ensure surgical consistency. In our work, a new automatic radioactive particle implantation device with two degrees of freedom was proposed to apply in the brachytherapy robotic surgery system as an end effector. Furthermore, physical assembling and simple function verifying experiments were accomplished. This device can help simplify the operating steps during surgery, and improve the stability of the surgical system, and enhances the surgical efficiency. © 2019 IEEE.

关键词： Robotic surgery

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A new method for fiber bragg grating based needle shape sensing calibration

A new method for fiber bragg grating based needle shape sens...

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2019 IEEE International Conference on robotics and Biomimetics, ROBIO 2019

作者： Zhang, Leifeng Li, Changle Zhang, Xuehe Liu, Gangfeng Liu, Yubin Zhao, Jie Ban, Guang Fan, Yilun Harbin Institute of Technology State Key Laboratory of Robotics and System Harbin 150080 NO. 2 YiKuang Street HeiLongJiang Province China

ISBN: (纸本)9781728163215

Accurate placement of the needle is critical in percutaneous surgery. Needle shape reconstruction technology based on fiber Bragg gratings (FBGs) sensor is considered to have the potential to achieve this goal. In this paper, we present a temperature-insensitive calibration model for calibrating needles with FBG sensors to accurately estimate its deformation. In addition, we have designed a device for simultaneously calibrating the loading direction and shape. Preliminary results indicate that the proposed model is theoretically insensitive to temperature, but in fact it can only be used within a certain temperature range. The resolution of the loading direction increases as the degree of bending increases, with a maximum error of 8.58°. Shape reconstruction error can be less than 1.5mm with small needle bending. This calibration method can meet clinical applications. © 2019 IEEE.

关键词： Fiber Bragg gratings

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Object-oriented Map Exploration and Construction Based on Auxiliary Task Aided DRL

Object-oriented Map Exploration and Construction Based on Au...

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International Conference on Pattern Recognition

作者： Junzhe Xu Jianhua Zhang Shengyong Chen Honghai Liu College of Computer Science and Technology Zhejiang University of Technology Hangzhou China College of Computer Science and Technology Tianjin University of Technology Tianjin China State Key Laboratory of Robotics and System School of Mechanical Engineering and Automation Harbin Institute of Technology Shenzhen China

Environment exploration by autonomous robots through deep reinforcement learning (DRL) based methods has attracted more and more attention. However, existing methods usually focus on robot navigation to single or multiple fixed goals, while ignoring the perception and construction of external environments. In this paper, we propose a novel environment exploration task based on DRL, which requires a robot fast and completely perceives all objects of interest, and reconstructs their poses in a global environment map, as much as the robot can do. To this end, we design an auxiliary task aided DRL model, which is integrated with the auxiliary object detection and 6-DoF pose estimation components. The outcome of auxiliary tasks can improve the learning speed and robustness of DRL, as well as the accuracy of object pose estimation. Comprehensive experimental results on the indoor simulation platform AI2-THOR have shown the effectiveness and robustness of our method.

关键词： Navigation Object oriented modeling Pose estimation Semantics Object detection Reinforcement learning Robustness

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Delay estimation for cortical-muscular interaction via the rate of voxels change

Delay estimation for cortical-muscular interaction via the r...

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IEEE International Conference on systems, Man and Cybernetics

作者： Jinbiao Liu Gansheng Tan Yixuan Sheng Jiaole Wang Wenjie Lu Honghai Liu State Key Laboratory of Mechanical System and Vibration Shanghai Jiao Tong University Shanghai China State Key Laboratory of Robotics and System School of Mechanical Engineering and Automation Harbin Institute of Technology Shenzhen China School of Computing University of Portsmouth Portsmouth UK

ISBN: (数字)9781728185262

ISBN: (纸本)9781728185279

It is evident that corticomuscular coherence (CMC), representing the functional coupling between motor cortex and muscle tissues, plays a crucial role in neurophysiologic studies and applications. It is hypothesized that there is an unknown time delay comprising at least neural conduction time in the process of corticomuscular interaction. In this study, we developed a novel delay estimation method, defined as the rate of voxels change (RVC) for the estimation of time delay in two coupled physiological signals. The RVC is the dynamic variation of the local CMCs observed in different time offsets. Both simulation and physiological data confirm the capability of RVC in estimating cortical-muscular delay. The underlying mechanisms of individual discrepancy of the latency is also investigated via exploring the correlation between delays, brain activity and motor performance. Correlation analyses indicate an intrinsic link between the connectivity strength of the brain network and the length of time delay in cortical-muscular interactions.

关键词： Correlation Delay effects Delay estimation Muscles Brain modeling Physiology Data models

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