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arXiv 2019年

作者： Lassaline, Nolan Brechbühler, Raphael Vonk, Sander J. W. Ridderbeek, Korneel Spieser, Martin Bisig, Samuel Feber, Boris Le Rabouw, Freddy T. Norris, David J. Dept. of Mechanical and Process Engineering Optical Materials Engineering Lab Eth Zurich Zurich8092 Switzerland Debye Institute for Nanomaterials Science Utrecht University Princetonplein 1 CC Utrecht3584 Netherlands Heidelberg Instruments Nano/SwissLitho Technoparkstrasse 1 Zurich8005 Switzerland

Gratings1 and holograms2 are patterned surfaces that tailor optical signals by diffraction. Despite their long history, variants with remarkable functionalities continue to be discovered3,4. Further advances could exploit Fourier optics5, which specifies the surface pattern that generates a desired diffracted output through its Fourier transform. To shape the optical wavefront, the ideal surface profile should contain a precise sum of sinusoidal waves, each with a well-defined amplitude, spatial frequency, and phase. However, because fabrication techniques typically yield profiles with at most a few dept. levels, complex 'wavy' surfaces cannot be obtained, limiting the straightforward mathematical design and implementation of sophisticated diffractive optics. Here we present a simple yet powerful approach to eliminate this design-fabrication mismatch by demonstrating optical surfaces that contain an arbitrary number of specified sinusoids. We combine thermal scanning-probe lithography6-8 and templating9 to create periodic and aperiodic surface patterns with continuous dept. control and sub-wavelength spatial resolution. Multicomponent linear gratings allow precise manipulation of electromagnetic signals through Fourier-spectrum engineering10. Consequently, we immediately resolve an important problem in photonics by creating a single-layer grating that simultaneously couples red, green, and blue light at the same angle of incidence. More broadly, we analytically design and accurately replicate intricate two-dimensional moiré patterns11, quasicrystals12,13, and holograms14,15, demonstrating a variety of previously impossible diffractive surfaces. Therefore, this approach provides instant benefit for optical devices (biosensors16, lasers17,18, metasurfaces4, and modulators19) and emerging topics in photonics (topological structures20, transformation optics21, and valleytronics22). Copyright © 2019, The Authors. All rights reserved.

关键词： Diffraction gratings

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Some interfacial interactions between isocyanates and metals that affect release in composite wood-panel production

Some interfacial interactions between isocyanates and metals...

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作者： Phanopoulos, Christopher Holvoet, Servaas Pratelli, Daniele Pans, Griet Shimizu, Kyoko Ng, Simon Bañuls-Ciscar, Jorge Abel, Marie-Laure Watts, John F. Huntsman Polyurethanes Global Res. Everslaan Everberg Belgium Materials Science Surface Analysis Lab. Dept. of Mechanical Engineering Sci. Univ. of Surrey Guildford Surrey United Kingdom SACHEM Japan GK Mizuhai Higashi Osaka Osaka Japan United Kingdom Atomic Energy Authority Culham Centre for Fusion Energy Abingdon Oxon United Kingdom JRC European Commission United Kingdom

Isocyanate- and polyurethane-based adhesives for composite wood-panel production are well known. They are useful for the manufacture of high-performance assemblies, particularly for moisture resistance, durability, and strength. However, isocyanate-based adhesives have several opportunities for improvements related to composite panel manufacture. Of particular note is the ability of isocyanates to bond, not only to wood, but to metal press platens used to produce the composite panels. Although several methodologies exist to overcome this, there is a lack of understanding of the nature of the interactions between isocyanates and metal. The purpose of the current study was to provide insights into these interactions and to help to develop strategies for releasable isocyanate-based resins. Variable-thickness isocyanate–metal and metal–wood assemblies were prepared and the interface exposed by various methods, e.g., surface analysis combined with cluster beam etching and simple peel tests. The interfaces were then analyzed by X-ray photoelectron spectroscopy or time-of-flight–secondary ion mass spectrometry (or both). These surface analytical methods have revealed several chemical interactions between the isocyanates and the metal surfaces, including carbamate-type links and metal–nitrogen linkages. Further, the surface analysis has revealed the compositional character of the locus of failure in wood–metal joints. The locus of failure depends on the presence of wood extractives. With nonextracted wood, the locus of failure is within the wood, which is characterized by a certain concentration of the penetrated resin. With solvent-extracted wood, the locus of failure is within the glue line. ©Forest Products Society 2018.

关键词： Metals

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CFD simulations of two rectangular water jets impinging on a water pool 48th

CFD simulations of two rectangular water jets impinging on a...

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48th AIAA Fluid Dynamics Conference, 2018

作者： Gao, Han Han, Xu Liu, Quanzhong Agarwal, Ramesh K. Dept. of Mechanical Engineering & Materials Science Washington University in St. Louis St. LouisMO63130 United States Dept. of Fluid Machinery and Control Engineering Harbin Institute of Technology Washington University in St. Louis St. LouisMO63130 United States

ISBN: (数字)9781624105531

ISBN: (纸本)9781624105531

CFD simulations of two water jets emanating from rectangular pipes of large aspect ratio and impinging on a water pool are performed using the commercial CFD software ANSYS Fluent. Reynolds-Averaged Navier-Stokes (RANS) equations with a number of turbulence models, namely the SA, k-ϵ and SST k-ω are solved. The computations are compared with the experimental data to assess the accuracy of various turbulence models. It is shown that majority of the details of the flow field during the initial phase of jets interaction and intermediate phase of jets merging are best captured by k-ϵ model but the final phase of combining of two jets into a single jet are best captured by the SST k-ω model due to its shear stress transport correction. The process of evolution of interaction of two jets from the initial phase to final phase is described in detail. © 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.

关键词： Jets

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HREM and Analytical TEM of the Rapidly Solidified Microstructure Evolved at the Extremes of the Coupled Crystal Growth Regime in Hypo-Eutectic Al-Cu Alloys

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Microscopy and Microanalysis 2018年第S1期24卷 34-35页

作者： Bathula, Vishwanadh Khanal, Subarna Wiezorek, Jorg M K Dept. of Mechanical Engineering and Materials Science University of Pittsburgh Pittsburgh PA USA Materials Science Division Bhabha Atomic Research Centre Mumbai India

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State-of-the-art of crack propagation modelling in tubular joints

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IOP Conference Series: materials science and engineering 2019年第1期700卷

作者： M Atteya O Mikkelsen H G Lemu Dept. of Mechanical and Structural Engineering and Materials Science University of Stavanger Norway

Offshore structures are conventionally designed for a service life between 20-30 years and mostly used beyond their service life. They are operated up to the point where costs of operations, maintenance and repair exceed the revenue generated by the offshore structure. The cyclic nature of environmental loading induces multi-axial stresses with high gradients in welded tubular joints that lead to fatigue cracks emanating from imperfections in the welded materials. Tubular joints may exhibit significant residual life after fatigue cracks formation due to crack propagating around the weld circumference. It is important to understand tubular joints behaviour and estimate the residual life beyond crack initiation as it promotes the safe operation of the offshore installation, inspection planning and life extension of the asset. This paper presents an overview of the residual life estimation of cracked tubular joints using numerical methods. The recent developments and possible enhancements to the modelling methods of cracked tubular joints are presented.

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Fatigue design challenges: Recent linear and nonlinear models

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IOP Conference Series: materials science and engineering 2019年第1期700卷

作者： D G Pavlou Dept. of Mechanical and Structural Engineering and Materials Science University of Stavanger Norway

Reliable fatigue design rules affect the proactive identification of safety parameters in engineering structures. Numerous fatigue crack initiation and propagation models, linear and nonlinear, have been developed for designing purposes or estimation of the remaining life of aging structures. Depending on the adopted assumptions, the accuracy varies for different loading histories, loading types, and materials. Semi empirical models are simple but yield significant inaccuracies. Models with better theoretical basis provide better accuracy, but implementation in real conditions is problematic. In the present work, a review of author's recent fatigue crack initiation and propagation models based on physical mechanisms is presented and improvements are proposed. Verification of the models on test results is provided and discussed.

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Improvement of the ungrounded force display using grooved cam

Improvement of the ungrounded force display using grooved ca...

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IEEE International Conference on Industrial Informatics (INDIN)

作者： Emi Kakuda Sho Yokota Akihiro Matsumoto Daisuke Chugo Hiroshi Hashimoto Graduate School of Science and Eng Toro University Kawagoe Japan Dept. of Mechanical Engineering Toyo University Kawagoe Japan School of Science and Technology Kwansei Gakuin University Hyogo Japan Master Program of Innovation for Design and Eng. Advanced Institute of Industrial Technology Tokyo Japan

This paper proposes the ungrounded force display using the grooved cam. Using the human illusion, the user can feel the force in the one direction when they use proposed device. It is mainly configured the cam and the slider. The slider follows the cam and moves translational movement. In this paper, we create the new prototype which solving the problems that emerged from the previous prototype. We evaluate the device using the two experiments. One is the subjective evaluation. Second one is the force presentation from the new prototype as the quantitative evaluation. We could solve problems of previous prototype by changing the cam type from plate to groove and blushless motor, and the new one produce the force more clearly than the previous prototype.

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Angle Control of Antagonistic Pneumatic Driven and Inflatable Arm Joint

Angle Control of Antagonistic Pneumatic Driven and Inflatabl...

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IEEE International Conference on Industrial Informatics (INDIN)

作者： Hirofusa Ogasawara Sho Yokota Akihiro Matsumoto Daisuke Chugo Hiroshi Hashimoto Graduate School of Science and Eng. Toyo University Kawagoe Japan Dept. of Mechanical Engineering Toyo University Kawagoe Japan School of Science and Technology Kwansei Gakuin University Hyogo Japan Master Program of Innovation for Design and Eng. Advanced Institute of Industrial Technology Tokyo Japan

The conventional robot arms applied in various fields are demanded to have high force output, high accuracy, high efficiency. But they are seldom applied in human life, because of large weight, rigidity, hazards to people caused by collisions. Therefore the soft robotic arm that is stretchable, light weight, softness without possible of hazards, and high precision control is suitable to deploy in human life. Thus the purpose of this research is to develop the soft robotic arm by using antagonistic pneumatic driven system. In order to realize this concept, the joint activation mechanism is the key component. This study focuses on the angle control of the joint. In this paper, the robot arm made by polyethylene is proposed. Air bags made of polyethylene inside the joint achieve antagonistic driven states. Helical tube made of polyethylene is adhered joint outside for realizing rigidity. It is characterized that control rigidity is realized by controlling the pressure in the helical tube and joint angle is preciously controlled in two degree of freedom by controlling pressure in the air bags. Furthermore, the joint angle can be controlled by controlling the air pressures in the air bags using stretch sensor measuring joint angle. The experimental result confirmed that the driving concept of the joint was well functioned, and the joint angle control was realized by feedback control.

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A Hybrid, Actively Compliant Manipulator/Gripper for Aerial Manipulation with a Multicopter

A Hybrid, Actively Compliant Manipulator/Gripper for Aerial ...

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IEEE International Workshop on Safety, Security, and Rescue Robotics (SSRR)

作者： Liam Kruse Justin Bradley Mechanical and Materials Engineering Dept. University of Nebraska-Lincoln Lincoln NE USA Computer Science and Engineering Dept. University of Nebraska-Lincoln NE USA

ISBN: (纸本)9781538655733

Unmanned Multicopters provide access to dangerous or difficult to reach areas and can accomplish tasks normally reserved for people. Aerial manipulation in this scenario could provide enhanced capabilities but is a challenging problem where design often comes down to choosing between arm-like manipulation or claw-like grippers - each of which has associated benefits and drawbacks. We present a novel, lightweight, low-cost hybrid manipulator/gripper combining characteristics of both arm-like manipulators and claw-like grippers to enable aerial manipulation during search and rescue missions using a multicopter unmanned air vehicle. The gripper is composed of tandem two degree-of-freedom fingers wherein each finger can be individually controlled, allowing for the manipulation of irregular geometric shapes and compensation for the drone's drift. We describe the design, manufacturing, and prototyping of our design and conduct a series of experiments grasping objects of different size, shape, and weight to demonstrate the versatility and benefits of our hybrid design.

关键词： Grippers Grasping End effectors Shape Payloads Drones

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Micro punch shear testing of unidirectional composites: A new test method 33

Micro punch shear testing of unidirectional composites: A ne...

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33rd Technical Conference of the American Society for Composites 2018

作者： Gillespie, John W. Ali, Molla A. Yen, Chian F. O’Brien, Daniel J. Haque, Bazle Z. Center for Composite Materials Dept. of Mech. Eng. Dept. of Civil and Env. Eng. Dept. of Materials Science and Eng. University of Delaware NewarkDE19716 United States Center for Composite Materials University of Delaware NewarkDE19716 United States Army Research Laboratory Aberdeen Proving GroundMD21005 United States Center for Composite Materials Department of Mechanical Engineering University of Delaware NewarkDE19716 United States

ISBN: (纸本)9781510872073

Punch shear damage of unidirectional (UD) composite is an important damage mode during the penetration and perforation of fiber-reinforced composites. A rate dependent progressive composite continuum damage model MAT162 in LS-Dyna® requires the punch shear strength and progressive damage softening parameters as input. A micro punch shear experimental test method has been developed for UD composite at sub-millimeter length scale for determining the punch shear properties and parameters. S Glass/DER353 epoxy UD composite ribbon specimens have been fabricated using the VARTM process. The samples have an nominal cross-sectional dimensions of 1000 × 57~70 , with about six (6) through-thickness fibers. The UD ribbon is adhesively bonded onto the specimen holder and a transverse load is applied across the width of the sample. Localized transverse shear loading is created within a narrow gap (153 ) between the punch and fixture support. Punch shear load-displacement data is reduced to engineering punch shear stress-strain. A large number of replicates are tested to quantify the stochastic non-linear progressive damage behavior. In order to identify the micromechanical damage mechanisms and quantify the fiber-matrix debonding length, fracture surfaces of micro punch shear __________ specimens have been thoroughly investigated using SEM and confocal microscopy. SEM micrographs clearly shows the initiation and propagation of mode II dominated fiber fracture, fiber-matrix debonding and matrix cracking. Confocal microscopy has been used to quantify the probability distribution functions associated with fiber-matrix debonding and pull-out. The experimental methodology using the micro punch shear test developed in this study can be used to study the effects of composite constituents (fiber, resin and interphase properties and FVF) on the non-linear progressive punch shear behavior of unidirectional composite punch shear strength. The statistical results and failure modes can also

关键词： Shear stress

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