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Some improvements on the one-step inverse isogeometric analysis by proposing a multistep inverse isogeometric methodology in sheet metal stamping processes

arXiv

引用

arXiv 2020年

作者： Reza Isazadeh, Amir Shamloofard, Mansoor Assempour, Ahmad Center of Excellence in Design Robotics and Automation Department of Mechanical Engineering Sharif University of Technology Azadi Avenue P.O. Box 11365-9567 Tehran Iran

The isogeometric methodology has been successfully implemented in one-step inverse analysis of sheet metal stamping processes. However, these models are not capable of analyzing forming processes that require severe deformation and several forming stages. This paper presents a multistep inverse isogeometric methodology to enhance the precision of one-step models in predictions of the initial blank, strain distributions, and drawability of the formed parts. This methodology deals with the minimization of potential energy, deformation theory of plasticity, and considering membrane elements. The presented methodology utilizes the NURBS basis functions to create the final, middle, and blank geometries and also to analyze sheet metal deformation. The characteristics of the applied formulations make it possible to simultaneously observe the effects of changing part parameters on its formability. One advantage of this approach is that the linear system of governing equations is solved without concerning about the convergence. Besides, the presented methodology can successfully generate the middle geometry and to restrict the movements of physical nodes along the middle surface, by presenting a new NURBS-based mapping and sliding constraint technique. The performance of the presented model is experimentally and numerically evaluated under two classical problems, including the forming of a rectangular box and a two-step drawing of a circular cup. Results comparisons indicate the credibility of the presented model in prediction of forming parameters at a low computation time. Copyright © 2020, The Authors. All rights reserved.

关键词： Potential energy

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Study of stinging nettle fibers as a reinforcing of composite materials based on its growing region 1

Study of stinging nettle fibers as a reinforcing of composit...

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1st International Conference on Design, Energy, Materials and Manufacture, ICDEMM 2018

作者： Suryawan, I.G.P.A. Suardana, N.P.G. Winaya, I.N.S. Suyasa, I.W.B. Lokantara, I.P. Department of Mechanical Engineering Udayana University Kampus Bukit Jimbaran Bali Indonesia Doctoral Program of Enviromental Science Udayana University Bali Denpasar Indonesia Doctoral Program of Engineering Science Udayana University Bali Denpasar Indonesia

Stinging nettle is a perennial herbaceous plant belonging to the Urticaceae family, In Bali Indonesia called jelatang. This species is considered a weed in intensive agriculture as its fast vegetative growth and high densities enable increased spread and soil coverage. In Tabanan Bali Indonesia several places to grow are in Denbantas altitude 200-500 meters and in Bedugul altitude 1000 -1500 meters above sea level. Nettle fibers are natural fibers that can be utilized as reinforcement for composite materials. Natural fibers have been used worldwide as a potential replacement for glass fiber reinforced composites, over the last few years has been applied in the automotive sector, aircraft interior and interior of the building. Properties of the natural fiber is lighter, easier to handle, not abrasive, and low cost. The objective of this study was to compare the composition and the tensile strength of the fiber nettle based growing areas from Bedugul and Denbantas. The method used is a fiber tensile test equipment, fourier transformer infrared red (FTIR), thermo-gravimetric analysis (TGA) and scanning electron microscope (SEM). From the research of nettle fibers that stinging nettle from Denbantas has a better tensile strength than Bedugul nettle. The TGA test the visible fiber from Denbantas is superior when used as a composite reinforcement. © Published under licence by IOP Publishing Ltd.

关键词： Scanning electron microscopy

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Chemistry across multiple phases (CAMP) version 1.0: An integrated multi-phase chemistry model

arXiv

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arXiv 2021年

作者： Dawson, Matthew L. Guzman, Christian Curtis, Jeffrey H. Acosta, Mario Zhu, Shupeng Dabdub, Donald Conley, Andrew West, Matthew Riemer, Nicole Jorba, Oriol Barcelona Supercomputing Center Barcelona Spain Department of Atmospheric Sciences University of Illinois at Urbana-Champaign UrbanaIL United States Department of Mechanical Science and Engineering University of Illinois at Urbana-Champaign UrbanaIL United States Atmospheric Chemistry Observations and Modeling Laboratory National Center for Atmospheric Research BoulderCO United States Advanced Power and Energy Program University of California IrvineCA United States Department of Mechanical and Aerospace Engineering University of California IrvineCA United States

A flexible treatment for gas- and aerosol-phase chemical processes has been developed for models of diverse scale, from box models up to global models. At the core of this novel framework is an"abstracted aerosol representation" that allows a given chemical mechanism to be solved in atmospheric models with different aerosol representations (e.g., sectional, modal, or particle-resolved). This is accomplished by treating aerosols as a collection of condensed phases that are implemented according to the aerosol representation of the host model. The framework also allows multiple chemical processes (e.g., gas- and aerosol-phase chemical reactions, emissions, deposition, photolysis, and mass-transfer) to be solved simultaneously as a single system. The flexibility of the model is achieved by (1) using an object-oriented design that facilitates extensibility to new types of chemical processes and to new ways of representing aerosol systems;(2) runtime model configuration using JSON input files that permits making changes to any part of the chemical mechanism without recompiling the model;this widely used, human-readable format allows entire gas- and aerosol-phase chemical mechanisms to be described with as much complexity as necessary;and (3) automated comprehensive testing that ensures stability of the code as new functionality is introduced. Together, these design choices enable users to build a customized multiphase mechanism, without having to handle pre-processors, solvers or compilers. Removing these hurdles makes this type of modeling accessible to a much wider community, including modelers, experimentalists, and educators. This new treatment compiles as a stand-alone library and has been deployed in the particle-resolved PartMC model and in the MONARCH chemical weather prediction system for use at regional and global scales. Results from the initial deployment to box models of different complexity and MONARCH will be discussed, along with future extension to more

关键词： Aerosols

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Multiscale investigation of seismic precursors before major earthquakes

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Mechanics Research Communications 2025年 147卷

作者： Friedrich, Leandro Ferreira Padilha, Mariana Hamdan Lacidogna, Giuseppe Iturrioz, Ignacio Graduate Program in Engineering Universidade Federal do Pampa Av. Tiaraju 810 CEP Alegrete97546-550 Brazil Department of Structural Geotechnical and Building Engineering Politecnico di Torino 24 Corso Duca degli Abruzzi Torino10129 Italy Mechanical Post-Graduate Program Universidade Federal do Rio Grande do Sul Sarmento Leite 425 CEP Porto Alegre90050-170 Brazil

In various mechanical systems, the study of damage processes can be approached from the perspective of continuous phase transition phenomena, a subject typically explored within the framework of statistical physics. This viewpoint enables a more refined interpretation of failure precursors, which are of great importance in the field. The present study investigates failure precursors through two case studies: the material failure process by using the Fiber Bundle Model and the seismicity of the 2023 Turkey Mw7.7 earthquake. To identify the criticality, two approaches are considered: (1) Natural Time (NT) analysis and (2) the Method of Critical Fluctuation-Based (MCF-B) approach. By comparing the evolution of precursors in both cases, the findings highlight their potential for predicting critical situations. © 2025 Elsevier Ltd

关键词： Large scale systems

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Dynamics and domain randomized gait modulation with bezier curves for sim-to-real legged locomotion

arXiv

引用

arXiv 2020年

作者： Rahme, Maurice Abraham, Ian Elwin, Matthew L. Murphey, Todd D. Department of Mechanical Engineering Northwestern University EvanstonIL60208 United States Robotics Institute Carnegie Mellon University PittsburghPA15213 Corresponding United States

We present a sim-to-real framework that uses dynamics and domain randomized offline reinforcement learning to enhance open-loop gaits for legged robots, allowing them to traverse uneven terrain without sensing foot impacts. Our approach, D2-Randomized Gait Modulation with Bezier Curves (D2-GMBC), uses augmented random search with randomized dynamics and terrain to train, in simulation, a policy that modifies the parameters and output of an open-loop Bezier curve gait generator for quadrupedal robots. The policy, using only inertial measurements, enables the robot to traverse unknown rough terrain, even when the robot’s physical parameters do not match the open-loop model. We compare the resulting policy to hand-tuned Bezier Curve gaits and to policies trained without randomization, both in simulation and on a real quadrupedal robot. With D2-GMBC, across a variety of experiments on unobserved and unknown uneven terrain, the robot walks significantly farther than with either hand-tuned gaits or gaits learned without domain randomization. Additionally, using D2-GMBC, the robot can walk laterally and rotate while on the rough terrain, even though it was trained only for forward walking. Copyright © 2020, The Authors. All rights reserved.

关键词： Modulation

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Detection and Location Estimation of Object in Unmanned Aerial Vehicle using Single Camera and GPS

Detection and Location Estimation of Object in Unmanned Aeri...

引用

Power, Control and Computing Technologies (ICPC2T), Conference on

作者： Snehil Sanyal Shashank Bhushan K Sivayazi Department of Mechanical Engineering Defence Institute of Advanced Technology Pune India Center for Artificial Intelligence & Robotics (CAIR) Defence Research & Development Organization (DRDO) Bengaluru India

ISBN: (数字)9781728149974

ISBN: (纸本)9781728149981

It is important for an Unmanned Aerial Vehicle (UAV) to detect any object in its view. This enables the UAV to locate the object with respect to itself and is required for locking and tracking the object. Object detection and location estimation makes the UAV capable of manipulating the environment as well as to follow the target. In the present work, object detection has been carried out using You Only Look Once (YOLO) to detect the object in the image stream of the Robot Operating System (ROS) bag file. The GPS information of the UAV is used to further calculate the GPS coordinates of the object. The images are acquired using a single monocular camera.

关键词： Cameras Object detection Global Positioning System Drones Three-dimensional displays Estimation

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PointAtrousGraph: Deep Hierarchical Encoder-Decoder with Point Atrous Convolution for Unorganized 3D Points

PointAtrousGraph: Deep Hierarchical Encoder-Decoder with Poi...

引用

IEEE International Conference on robotics and Automation (ICRA)

作者： Liang Pan Chee-Meng Chew Gim Hee Lee Advanced Robotics Centre National University of Singapore Department of Mechanical Engineering National University of Singapore Computer Vision and Robotic Perception (CVRP) Lab National University of Singapore

ISBN: (数字)9781728173955

ISBN: (纸本)9781728173962

Motivated by the success of encoding multi-scale contextual information for image analysis, we propose our PointAtrousGraph (PAG) - a deep permutation-invariant hierarchical encoder-decoder for efficiently exploiting multi-scale edge features in point clouds. Our PAG is constructed by several novel modules, such as Point Atrous Convolution (PAC), Edgepreserved Pooling (EP) and Edge-preserved Unpooling (EU). Similar with atrous convolution, our PAC can effectively enlarge receptive fields of filters and thus densely learn multi-scale point features. Following the idea of non-overlapping maxpooling operations, we propose our EP to preserve critical edge features during subsampling. Correspondingly, our EU modules gradually recover spatial information for edge features. In addition, we introduce chained skip subsampling/upsampling modules that directly propagate edge features to the final stage. Particularly, our proposed auxiliary loss functions can further improve our performance. Experimental results show that our PAG outperform previous state-of-the-art methods on various 3D semantic perception applications.

关键词： Three-dimensional displays Picture archiving and communication systems Convolution Semantics Image edge detection Task analysis Decoding

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Chitosan-polyvinyl alcohol (PVA) based composite biofilm: The effect of solvent and nanofiller

引用

AIP Conference Proceedings 2024年第1期3073卷

作者： Bintang Junita Siom Jayanudin Mekro Permana Pinem Endarto Yudo Wardhono Master’s Program in Chemical Engineering Postgraduate School Universitas Sultan Ageng Tirtayasa Jl. Jenderal Sudirman KM. 3 Cilegon 42435 Indonesia Chemical Engineering Department Universitas Sultan Ageng Tirtayasa Jl. Jenderal Sudirman KM. 3 Cilegon 42435 Indonesia Mechanical Engineering Department Universitas Sultan Ageng Tirtayasa Jl. Jenderal Sudirman KM. 3 Cilegon 42435 Indonesia

Environmental issues are the most critical and urgent factor for the increasing use of biopolymers in broader applications. Research on chitosan as a bioplastic material opens vast opportunities to improve its weak mechanical properties. These include blending with biopolymer/synthetic polymers as a matrix or incorporating with nanofillers. The use of organic solvents in dissolving chitosan is also interesting for further research. In this study, we synthesized a chitosan/PVA-based biofilm composite in five different ratios (100/0, 80/20, 60/40, 40/60, 0/100) in acetic acid and citric acid with the addition of 10% weight glycerol to get the optimum composition of mechanical properties. This optimum film would be conducted with SiO2 nanoparticles (NPs) and Cellulose Nano Crystals (CNCs) to evaluate the reinforcement effects. Various properties, including surface morphology, functional, mechanical properties, and thermal behavior, were characterized. The experimental result showed that the tensile strength of the composite film in acetic acid was higher than in citric acid. With the addition of 2.5% w/w of SiO2 NPs, the tensile strength of the composite film got its maximum value, 21.01 MPa, and the maximum of 25.77 MPa with 10% w/w of CNCs, which was 115,7% higher than with of the pure chitosan/PVA film in the ratio of 80/20 which was the optimum. The effect of adding CNC and SiO2 NPS has the opposite effect. The addition of filler CNCs will improve mechanical properties, while SiO2 NPs tend to decrease mechanical properties. All film characterizations demonstrated that the physicochemical interaction between CNCs and chitosan/PVA molecules improved their mechanical and thermal properties.

关键词：

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Robust and Efficient Estimation of Absolute Camera Pose for Monocular Visual Odometry

Robust and Efficient Estimation of Absolute Camera Pose for ...

引用

IEEE International Conference on robotics and Automation (ICRA)

作者： Haoang Li Wen Chen Ji Zhao Jean-Charles Bazin Lei Luo Zhe Liu Yun-Hui Liu T Stone Robotics Institute and Department of Mechanical and Automation Engineering The Chinese University of Hong Kong China TuSimple China KAIST South Korea Wuhan University China

ISBN: (数字)9781728173955

ISBN: (纸本)9781728173962

Given a set of 3D-to-2D point correspondences corrupted by outliers, we aim to robustly estimate the absolute camera pose. Existing methods robust to outliers either fail to guarantee high robustness and efficiency simultaneously, or require an appropriate initial pose and thus lack generality. In contrast, we propose a novel approach based on the robust "L 2 -minimizing estimate" (L 2 E) loss. We first define a novel cost function by integrating the projection constraint into the L 2 E loss. Then to efficiently obtain the global minimum of this function, we propose a hybrid strategy of a local optimizer and branch-and-bound. For branch-and-bound, we derive effective function bounds. Our approach can handle high outlier ratios, leading to high robustness. It can run reliably regardless of whether the initial pose is appropriate, providing high generality. Moreover, given a decent initial pose, it is suitable for real-time applications. Experiments on synthetic and real-world datasets showed that our approach outperforms state-of-the-art methods in terms of robustness and/or efficiency.

关键词： Robustness Pose estimation Cameras Cost function Three-dimensional displays

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Analytical and numerical modeling of a clamped-clamped micro beam under electric actuation 4

Analytical and numerical modeling of a clamped-clamped micro...

引用

2018 4th International Conference on Smart Material Research, ICSMR 2018

作者： Mustafa, Aalim M Mahgoub, Ahmed K Mechanical Engineering Department Prince Mohammad Bin Fahd University Dhahran Saudi Arabia Engineering Technology Program PSEP King Fahd University of Petroleum and Minerals Dhahran Saudi Arabia

This paper studies the deflection of a clamped-clamped micro beam actuator subjected to an electric voltage. Two approaches were applied to model the micro beam under study: the first one is analytical and the second is numerical. A solution to the analytical model was developed to investigate the mechanical behaviour of the micro beam-based MEMS device under electric actuation and simulations was done using Wolfram Mathematica® software. On the other hand, a finite element model (FEM) simulation was performed using COMSOL Multiphysics® for data validation for the micro beam model, and the results showed very good agreement. The effect of changing beam length, thickness and height from the ground on both the maximum beam displacement and pull-in voltage was also analyzed. © Published under licence by IOP Publishing Ltd.

关键词： Multiphysics

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