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Performance analysis on mechanical and machinability attributes of Al6061-B4C-T6 composites processed via hot extrusion

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Proceedings of the Institution of mechanical Engineers, Part B: Journal of engineering Manufacture 2024年第9期238卷 1386-1400页

作者： Tinga, Sibel Karakoç, Halil Yağmur, Selçuk Saravana Kumar, M. Şeker, Ulvi Çıtak, Ramazan Department of Metallurgy and Materials Engineering Gazi University Ankara Turkey Department of Mechanical Program Hacettepe University Ankara Turkey Department of Manufacturing Engineering Gazi University Ankara Turkey Graduate Institute of Manufacturing Technology National Taipei University of Technology Taipei Taiwan

In this study, composite materials with Al6061 alloy matrix and B4C particles reinforcement were produced by hot extrusion process. Fabricated composites were examined for the mechanical and machinability attributes. Al6061 alloy powders (4C particles (4C (3%, 6%, and 9% by weight) of and then cold pressed under 200 MPa pressure. The cold pressed powder metal block was extruded hot after preheating at 550°C for 1 h. Further, the composites were subjected to T6 aging heat treatment after hot extrusion. Microstructure, density, hardness, tensile strength, and wear properties were examined. The effects of cutting speed and cutting force on the machinability were also investigated. In addition, surface roughness and chips formation were examined. High density (99.6%) values were achieved with the extrusion process. With increasing B4C particles ratio, the hardness and tensile values were increased which was substantiated by the fracture morphology of the tensile specimens. It has been observed that tool smearing was high in the machining of the low-reinforced (3% B4C) composite. The highest cutting force was measured as 236 N at a feed rate of 0.27 mm/rev and a cutting speed of 250 m/min. It has also been observed that the average surface roughness decreased with increasing cutting speed and it increased with increasing feed rate. © IMechE 2023.

关键词： Microstructure

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ANALYSIS OF WIND TURBINE ACOUSTIC SIGNALS IN TERMS OF DETECTING AMPLITUDE MODULATION AND FREQUENCY DEVIATION 10

ANALYSIS OF WIND TURBINE ACOUSTIC SIGNALS IN TERMS OF DETECT...

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10th Convention of the European Acoustics Association, EAA 2023

作者： Czapla, Marcjanna Wszolek, Tadeusz Department of Mechanics and Vibroacoustic Faculty of Mechanical Engineering and Robotics AGH University of Science and Technology Poland

ISBN: (纸本)9788888942674

The phenomenon of amplitude modulation has been subject of numerous scientific studies [1-4]. However, the problem remains of determining the depth of AM's impact on the increase in annoyance of wind turbine noise. The results of this research showing the characteristic features and depth of AM in different frequency bands. In addition, it has been shown that, in the recorded results, modulation (deviation) of the frequency of the modulated band occurs simultaneously with amplitude modulation. Cyclical changes in the density distribution of spectra in time and space have been demonstrated. Examples have been presented show that defined metrics to determine the variability of modulation frequency depending on the observer's position relative to the signal source. One such parameter that can demonstrate objective frequency offset is the popular shimmer indicator. © 2023 First author et al. This is an open-access article distributed under the terms of the Creative Commons Attribution 3.0 Unported License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

关键词： Frequency modulation

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Position-aware pushing and grasping synergy with deep reinforcement learning in clutter

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CAAI Transactions on Intelligence Technology 2024年第3期9卷 738-755页

作者： Min Zhao Guoyu Zuo Shuangyue Yu Daoxiong Gong Zihao Wang Ouattara Sie Intelligent Robotics Laboratory Faculty of Information TechnologyBeijing University of TechnologyBeijingChina Beijing Key Laboratory of Computational Intelligence and Intelligent Systems BeijingChina Laboratory of Biomechatronics and Intelligent Robotics(BIRO) Department of Mechanical and Aerospace EngineeringNorth Carolina State UniversityRaleighNorth CarolinaUSA

The positional information of objects is crucial to enable robots to perform grasping and pushing manipulations in *** effectively perform grasping and pushing manipu-lations,robots need to perceive the position information of objects,including the co-ordinates and spatial relationship between objects(e.g.,proximity,adjacency).The authors propose an end-to-end position-aware deep Q-learning framework to achieve efficient collaborative pushing and grasping in ***,a pair of conjugate pushing and grasping attention modules are proposed to capture the position information of objects and generate high-quality affordance maps of operating positions with features of pushing and grasping *** addition,the authors propose an object isolation metric and clutter metric based on instance segmentation to measure the spatial re-lationships between objects in cluttered *** further enhance the perception capacity of position information of the objects,the authors associate the change in the object isolation metric and clutter metric in cluttered environment before and after performing the action with reward function.A series of experiments are carried out in simulation and real-world which indicate that the method improves sample efficiency,task completion rate,grasping success rate and action efficiency compared to state-of-the-art end-to-end *** that the authors’system can be robustly applied to real-world use and extended to novel *** material is available at https://***/NhG\_k5v3NnM}{https://***/NhG\_k5v3NnM.

关键词： deep learning deep neural networks intelligent robots

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Advancement in Smart Cane Technology: Enhancing Mobility for the Visually Impaired Using ROS and LiDAR 6

Advancement in Smart Cane Technology: Enhancing Mobility for...

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6th International Conference on robotics and Automation in Industry, ICRAI 2024

作者： Zafar, Saqib Maqbool, Hafiz Farhan Ahmad, Naveed Ali, Arham Moeizz, Abdul Ali, Faizan Taborri, Juri Rossi, Stefano University of Tuscia Department of Economics Engineering Society and Business Organization VT Viterbo01100 Italy University of Engineering and Technology Lahore Department of Mechanical Mechatronics and Manufacturing Engineering Faisalabad Campus Lahore38000 Pakistan National Center of Robotics and Automation Human-Centred Robotics Lab Pakistan

ISBN: (纸本)9798350355703

Visual impairment affects the ability to navigate independently in an unknown environment due to reliance on human/dog assistance, potential miscommunication, and discomfort during mobility. To make the visually impaired (VI) individuals self-reliant and confident in their mobility the proposed system has been developed that contains a light detection and ranging (LiDAR) sensor for obstacle detection and two omni-wheels coupled with the DC gear encoder motors for precise movement in any direction without lifting the cane. Hector Simultaneous Localization and Mapping (SLAM), A, and steering wheel algorithms have been implemented in the robot operating system (ROS) for real-time environment mapping, efficient path planning, and navigating in an unknown indoor static environment, respectively. The Raspberry Pi 3B+ and Arduino Mega 2560 are used in the master-slave configuration for decision-making on path planning and controlling the maneuverability of the system in real-time. The proposed system in the paper is successfully tested on one subject in two indoor environments. The results demonstrate that the system serves as an assistive mobile robot, helping the VI individual to navigate confidently in an unknown environment and reach the destination without assistance. © 2024 IEEE.

关键词： Motion planning

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Gait dynamic stability evaluation on inclined surfaces for inverted or everted feet walking

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Fuss und Sprunggelenk 2024年第4期22卷 254-268页

作者： Raza, Anam Mahmood, Imran Sultana, Tayyaba Sultana, Salma Dehghani-Sanij, Abbas A. Department of Zoology Government College University Faisalabad Pakistan Mechatronics and Control Engineering Department Faisalabad Campus UET Lahore Pakistan Institute of Design Robotics and Optimisation School of Mechanical Engineering University of Leeds United Kingdom

Background: This study investigates gait dynamic stability on inclined surfaces while walking with foot rotational impairments such as everted and inverted feet. Walking stability is assessed during gait transitional periods i.e. weight loading and unloading phases. Methods: Foot rotational impairments (eversion and inversion) are imitated using wedged foot insoles. A total of ten healthy subjects performed five trials for each of the inverted, everted, and normal feet conditions. Experimental data was collected using a twelve-camera motion capture system and a force plate installed on an inclined platform. Lower limb joint kinematics were computed in Visual-3D motion analysis software to evaluate the degree of foot rotational impairments. Gait dynamic stability was assessed by analysing the centre of mass and centre of pressure signals as neuromechanical input and output responses respectively. Both signals were modelled in time and frequency domains and stability margins were quantified by applying Nyquist and Bode (N&B) methods from control engineering theory. Results: Stability margins quantified from N&B methods illustrated the loading phase as stable and the unloading phase as unstable gait transitions. During the loading phase, both rotational impairments illustrated a decrease in stability (p < 0,05) for the ramp ascent walk and an increase in stability (p < 0,05) for the ramp descent walk. However, there was no difference observed for the respective unloading phases. Results from neuromotor outputs (CoP-velocity) illustrated a strong interlimb correlation (p < 0,001) during gait transitional periods, implying a compensatory stability interaction exists between opposite limbs. Further, stabilities quantified from outputs were found greater in magnitudes than the instability quantified from inputs illustrating the robustness of neuromotor balance control. Conclusions: Results support the hypothesis that gait stability gets affected while walking with rotation

关键词： Balance control Foot Gait stability Inclined walk Rotational impairments

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Design and Implementation of a Variable Camber Mechanism for a Small Fixed-Wing UAV (Unmanned Aerial Vehicle)

Design and Implementation of a Variable Camber Mechanism for...

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2024 IEEE International Conference on robotics and Biomimetics, ROBIO 2024

作者： Islam, Md Azizul Rodriguez, Jacob Saha, Achintya K. Hwang, Yongwon Jo, Bruce W. Tennessee Tech. University Department of Mechanical Engineering CookevilleTN United States Kwangwoon University Dept. of Robotics Korea Republic of Tennessee Technological University Department of Mechanical Engineering CookevilleTN United States

ISBN: (纸本)9781665481090

Inspired by nature and avionic birds, this paper introduces effective airfoil morphing mechanisms followed by its detailed design, implementation, and control aspects. Unlike conventional fixed-wing aircraft that use control surfaces such as flaps and ailerons for flight control, the concept of morphing is a more substantial and conformal shape change that has the advantages of enhanced aerodynamic performances, including longer flight time and range, radar signature, from reduced D (drag force) or improved L (lift force)/D, L and D ratio. Camber is the curvature in the airfoil, and camber morphing is one way of adjusting the camber rate or curvature to modify the flight profile by adjusting L and D. Various works have shown the effectiveness of camber morphing;however, the actual implementation and control of effective mechanisms have not been fully developed for UAVs since camber morphing requires specific internal mechanisms that are light and simple and conformally change the camber rate accordingly. This paper shares detailed design, implementation, and expected costs for converting from conventional to morphing UAVs in future applications. © 2024 IEEE.

关键词： Cambers

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Droplet breakup and size distribution in an airstream: Effect of inertia

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Physical Review Fluids 2024年第8期9卷 084004-084004页

作者： Someshwar Sanjay Ade Pavan Kumar Kirar Lakshmana Dora Chandrala Kirti Chandra Sahu Center for Interdisciplinary Program Department of Chemical Engineering Department of Mechanical and Aerospace Engineering

We experimentally investigate the morphology and breakup of a droplet as it descends freely from a height and encounters an airstream. The size distributions of the child droplets are analyzed using high-speed shadowgraphy and in-line holography techniques. We find that a droplet falling from various heights exhibits shape oscillations due to the intricate interplay between inertia and surface tension forces, leading to significant variations in the radial deformation of the droplet, influencing the breakup dynamics under an identical airstream condition. Specifically, the droplet undergoes vibrational breakup when introduced at a location slightly above the air nozzle. In contrast, as the release height of the droplet increases, keeping the Weber number defined based on the velocity of the airstream fixed, a dynamic interplay between the inertia of the droplet and the aerodynamic flow field comes into play, resulting in a sequence of breakup modes transitioning from vibrational breakup to retracting bag breakup, bag breakup, bag-stamen breakup, retracting bag-stamen breakup, and eventually returning to vibrational breakup. Our experiments also reveal that the size distribution resulting from retracting bag breakup primarily arises from rim and node fragmentation, leading to a bimodal distribution. In contrast, bag and bag-stamen breakups yield a trimodal size distribution due to the combined contributions of bag, rim, and node breakup mechanisms. Furthermore, we utilize a theoretical model that incorporates the effective Weber number, considering different release heights. This model accurately predicts the size distribution of the child droplets resulting from the various breakup modes observed in our experiments.

关键词： Atomization Drop breakup Drop coalescence Drops & bubbles

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Evaluation on the microhardness of Ni-TiO2 nanocomposite coatings on AISI 1022 substrate

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Materials Today: Proceedings 2022年 62卷 811-817页

作者： Natarajan, P. Mohanraj, M. Sathish Kumar, R. Thirumoorthy, A. Prabhakaran, S. Department of Mechanical Engineering Government College of Engineering Salem 636011 India Department of Automobile Engineering Hindustan Institute of Technology and Science Chennai 603103 India Department of Mechanical Engineering Velalar College of Engineering and Technology Thindal Erode 638012 India Department of Robotics and Automation Engineering PSG College of Technology Coimbatore 641004 India

The surface strength and performance of the material depends mainly on the appropriate coating techniques and also on the selection of the appropriate process parameters. From in this, electroplating is broadly used to protecting the material's surface and hence increases the life of industrial components. The present study pulse electrodeposition of Ni-TiO2 nanocomposite coating was developed on the surface of AISI 1022 Carbon Steel from watts bath. Such nanocoatings greatly enhanced the better hardness, wear and corrosion resistance in the automotive industry. The present work purpose to examine the influence of the coating process parameters on the microhardness (MH) of Ni-TiO2 nanocomposite coating on AISI 1022 Carbon Steel with the aid of response surface methodology (RSM). The Pulse frequency (Hz), Current density (A/cm2) and Duty cycle (%) parameters are considered and integrated into the RSM three factors and three level orthogonal arrays to determine the optimized condition for improved hardness of the coating. The contribution of the coating parameters was studied with the help of analysis of variance (ANOVA). The result revealed frequency: 20 Hz, current density: 0.2 A/cm2 and duty cycle: 30% coated specimen uniformly distributed cauliflower structure than compared to the frequency: 30 Hz, current density: 0.2 A/cm2 and duty cycle: 20%. To explore that uniformly coated specimen EDX, field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) respectively. © 2022

关键词： Titanium dioxide

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A Phase-change-material-based Variable Stiffness Sheath Inspired by a Multi-layer Wave Spring Structure for Flexible Upper Gastrointestinal Endoscopic Robots

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IEEE robotics and Automation Letters 2025年第6期10卷 6504-6511页

作者： Song, Dezhi Luo, Xiangyu Yu, Xiangyang Zhang, Bo Yang, Zhengbao Hu, Chengzhi Shi, Chaoyang Tianjin University Key Laboratory of Mechanism Theory and Equipment Design of Ministry of Education School of Mechanical Engineering Tianjin300072 China Tianjin Hospital of ITCWM Tianjin Nankai Hospital Department of Gastrointestinal Surgery Tianjin300100 China Waseda University Future Robotics Organization Tokyo1620044 Japan The Hong Kong University of Science and Technology Department of Mechanical and Aerospace Engineering Hong Kong Southern University of Science and Technology Department of Mechanical and Energy Engineering Shenzhen518055 China

Continuum robots in flexible gastrointestinal endoscopy require transitioning between flexible and rigid states. Phase-change-material-based variable stiffness (VS) methods exhibit a significant stiffness change ratio but are typically time-consuming. These materials are commonly fabricated as simple cylindrical or tubular structures and integrated with continuum joints, overlooking how the VS module's structural characteristics affect stiffness modulation and bending performance. To balance motion flexibility and operational stability, this work presents a stiffness-tunable sheath inspired by a multi-layer wave spring structure, fabricated utilizing thermoplastic material. A water-based active heating/cooling method is employed, wherein the circulation of hot/cold water through silicone tubes helically wrapped around the VS sheath enables rapid thermal regulation. Structural parameters selection of the VS sheath based on the orthogonal design method has been performed to enhance rigid-state stiffness and reduce maximum stress during 90° flexion in a flexible state. Experimental results showed the proposed VS sheath achieves a stiffness change ratio of up to 16.5 times within 30s. After being integrated with a continuum joint, the sheath demonstrates an average positioning error of 1.48mm within a ±90° bending range in a flexible state, without structural compromise or interference with the continuum joint's bending. In a rigid state, the proposed design can resist 400g external payload with a deflection of less than 6mm. The efficacy of this design has been validated through ex-vivo experiments on a porcine stomach. © 2016 IEEE.

关键词： Endoscopy

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Droplets Measurement with High-Speed Camera and Defocusing Method

Droplets Measurement with High-Speed Camera and Defocusing M...

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2024 Annual Conference on Transactions of the American Nuclear Society, ANS 2024

作者： Cohn, Ayden Liu, Yang Shi, Shanbin Lan, Eymon Nuclear Engineering Program Department of Mechanical Engineering Virginia Tech 635 Prices Fork Road BlacksburgVA24061 United States Nuclear Engineering Program Department of Mechanical Aerospace and Nuclear Engineering Rensselaer Polytechnic Institute 110 8th Street TroyNY12180 United States

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