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Статті в журналах з теми "Interface à contact intermittent":
1
Labardi, M., P. Tripathi, S. Capaccioli, and R. Casalini. "Intermittent-contact local dielectric spectroscopy of nanostructured interfaces." Nanotechnology 33, no. 21 (February 28, 2022): 210002. http://dx.doi.org/10.1088/1361-6528/ac52be.
Анотація:
Abstract Local dielectric spectroscopy (LDS) is a scanning probe method, based on dynamic-mode atomic force microscopy (AFM), to discriminate dielectric properties at surfaces with nanometer-scale lateral resolution. Until now a sub-10 nm resolution for LDS has not been documented, that would give access to the length scale of fundamental physical phenomena such as the cooperativity length related to structural arrest in glass formers (2–3 nm). In this work, LDS performed by a peculiar variant of intermittent-contact mode of AFM, named constant-excitation frequency modulation, was introduced and extensively explored in order to assess its best resolution capability. Dependence of resolution and contrast of dielectric imaging and spectroscopy on operation parameters like probe oscillation amplitude and free amplitude, the resulting frequency shift, and probe/surface distance-regulation feedback gain, were explored. By using thin films of a diblock copolymer of polystyrene (PS) and polymethylmethacrylate (PMMA), exhibiting phase separation on the nanometer scale, lateral resolution of at least 3 nm was demonstrated in both dielectric imaging and localized spectroscopy, by operating with optimized parameters. The interface within lamellar PS/PMMA was mapped, with a best width in the range between 1 and 3 nm. Changes of characteristic time of the secondary (β) relaxation process of PMMA could be tracked across the interface with PS.
2
Peng, Wei, James Kiely, and Yiao-Tee Hsia. "Wear Analysis of Head-Disk Interface During Contact." Journal of Tribology 127, no. 1 (January 1, 2005): 171–79. http://dx.doi.org/10.1115/1.1843832.
Анотація:
To achieve a higher storage density in a hard disk drive, the fly height of the air bearing slider, as part of the magnetic spacing, has to be minimized. At an ultralow fly height, the intermittent–continuous contact at the head–disk interface (HDI) is unavoidable and directly affects the mechanical and magnetic performance of the hard disk drive, and is of great interest. The HDI wear has a nonlinear and time-varying nature due to the change of contact force and roughness. To predict the HDI wear evolution, an iterative model of Coupled Head And Disk (CHAD) wear, is developed based on the contact mechanics. In this model, a composite transient wear coefficient is adopted and multiple phases of the wear evolution are established. A comprehensive contact stiffness is derived to characterize the contact at the HDI. The abrasive and adhesive wear is calculated based on the extended Archard’s wear law. The plastic and elastic contact areas are calculated with a three-dimensional (3D) sliding contact model. Based on the CHAD wear model, for the first time, the coupling between head and disk wear evolutions is thoroughly investigated. Accelerated wear tests have also been performed to verify the disk wear effect on the slider wear. A wear coefficient drop with time is observed during the tests and it is attributed to a wear mechanism shift from abrasive to adhesive wear. A shift in the type of contact from plastic to elastic accounts for the wear mechanism change.
3
Lotfi, Mohammad, Saeid Amini, and Hossein Ashrafi. "Theoretical and numerical modeling of tool–chip friction in ultrasonic-assisted turning." Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering 233, no. 4 (November 15, 2018): 824–38. http://dx.doi.org/10.1177/0954408918812271.
Анотація:
Decrease of friction in tool–chip contact zone is a key subject in metal cutting operation. Therefore, effect of ultrasonic vibration in this area is analyzed by using experimental and simulation methods. In this study, a theoretical model is firstly developed based on the shear friction model, and then sticking–sliding contact zones plus their contact lengths are defined in order to simulate conventional and ultrasonic-assisted turning. Accordingly, shear angle, sticky length, and cutting forces were measured in experiments as input parameters for the calculation of friction coefficients. As a result, intermittent contact of vibrated tool decreases the time of thermal conduction in tool–chip interface, resulting in a significant reduction in friction coefficient and contact length, particularly, in sticky region.
4
Ayala, Jose R. Ruiz, Kwangjin Lee, Mujibur Rahman, and J. R. Barber. "Effect of Intermittent Contact on the Stability of Thermoelastic Sliding Contact." Journal of Tribology 118, no. 1 (January 1, 1996): 102–8. http://dx.doi.org/10.1115/1.2837063.
Анотація:
In many sliding systems, the sliding surfaces are not coextensive, so that points on one surface experience alternating periods of contact and separation. This intermittent process can be expected to influence the sliding speed at which the system is susceptible to frictionally-induced thermoelastic instability (TEI). This question is explored in the context of a simple system consisting of a rotating thin-walled cylinder whose end face slides against a rigid surface. The results show that at low Fourier number—i.e., when the frequency of the process is high compared with the thermal transient of the system—only the time-averaged frictional heat input is important and the critical speed is an inverse linear function of the proportion of time in sliding contact. At higher Fourier number, lower critical speeds are obtained, but the dependence on Fourier number is relatively weak.
5
Maeno, Takashi, and David B. Bogy. "Effect of the Rotor/Stator Interface Condition Including Contact Type, Geometry, and Material on the Performance of Ultrasonic Motor." Journal of Tribology 116, no. 4 (October 1, 1994): 726–32. http://dx.doi.org/10.1115/1.2927326.
Анотація:
The purpose of this paper is to show the dynamic contact characteristics and the motor performance of several types of ultrasonic motors. First, we compare the performance of “intermittent” and “traveling” contact type ultrasonic motors by using the locally deforming rotor model. We show that the motor performances are the same when the shape of the stator’s amplitude, and the rotor’s interpenetration are the same. Then, we show that the performance of these two types of motors are different according to the effects of inertia and actual three dimensional displacement by using the FE (finite element) analysis. Finally, the effects of the teeth and a surface layer at the contact interface on the performance of the ultrasonic motor, including T-N (torque-speed) characteristics and friction loss, are analyzed.
6
Polycarpou, A. A., and A. Soom. "A Two-Component Mixed Friction Model for a Lubricated Line Contact." Journal of Tribology 118, no. 1 (January 1, 1996): 183–89. http://dx.doi.org/10.1115/1.2837076.
Анотація:
A two-component, two-dimensional friction model for a lubricated line contact, operating in boundary and mixed lubrication regimes, is developed. The friction is explicitly decomposed into the solid and the fluid shear components. The solid component is due to the asperity interactions and the fluid shear arises from the lubricant present at the interface. The friction model includes the sliding velocity, the instantaneous separation of the sliding bodies, normal to the sliding direction, the normal load and fluid properties. The model is based on unsteady friction experiments carried out under constant normal loads and time-varying sliding velocities. The model is applied to quasi-steady sliding, unsteady continuous and intermittent sliding, including sticking and momentary reversals of motion. In each case it becomes possible to track the instantaneous fluid shear and solid friction components.
7
Li, Yufeng, and Aric R. Kumaran. "The Determination of Flash Temperature in Intermittent Magnetic Head/Disk Contacts Using Magnetoresistive Heads: Part II—Experimental Investigation." Journal of Tribology 115, no. 1 (January 1, 1993): 179–84. http://dx.doi.org/10.1115/1.2920973.
Анотація:
The flash temperature during intermittent head/disk contacts was measured using specially fabricated magnetoresistive heads. Microasperities were intentionally created on disk substrates, and ZrO2 was sputtered on disc surfaces as overcoat. It was found that with a disk spinning speed of 20 m/s, flash temperature could reach 50 to 100°C for transient contact (head was moving in disk radial direction), but less than 40°C for dwell on track contact (head was stationary). The contact times were in the range from submicroseconds to several microseconds, contact widths on the order of several micrometers, and temperature sensitivity coefficients in the range from 0.15 to 0.7 for a 2.5–μ high magnetoresistive sensor.
8
Li, Yufeng, and Aric R. Kumaran. "The Determination of Flash Temperature in Intermittent Magnetic Head/Disk Contacts Using Magnetoresistive Heads: Part I—Model and Laser Simulation." Journal of Tribology 115, no. 1 (January 1, 1993): 170–78. http://dx.doi.org/10.1115/1.2920972.
Анотація:
The feasibility of using a magnetoresistive magnetic head to determine the flash temperature of intermittent magnetic head/disk contacts is investigated. A finite difference model is developed to study the effects of the magnetoresistive sensor height, the contact power intensity and the contact duration on the temperature response characteristics of the magnetoresistive sensor. A pulsed neody-minum:yttrium-aluminum-garnet laser is used as the heat source to simulate the contact and verify the model. The simulation results agree well with the theoretical model. Based on the theoretical model and laser simulation, a temperature sensitivity coefficient ζ is proposed to determine the surface temperature rise.
9
Annakodi, Vivek Anand, Ramachandra Arvind Singh, Subramanian Jayalakshmi, Yupeng Zhang, Muhammed Anaz Khan, Koppula Srinivas Rao, and Rajashekhara Shabadi. "Patterning SS304 Surface at Microscale to Reduce Wettability and Corrosion in Saline Water." Metals 12, no. 7 (July 3, 2022): 1137. http://dx.doi.org/10.3390/met12071137.
Анотація:
Stainless steel 304 (SS304) experiences corrosion when it is exposed to a saline atmosphere, which attains severity due to its high surface wettability. Topographical modification of metallic surfaces is an effective route to reduce wettability and thereby mitigate liquid-mediated corrosion. In this work, topographical modification of stainless steel 304 flat surface in the form of micropillars was done (pillar width: 100 μm, inter-pillar distance: 100 μm and height: 80 μm). Micropillars were fabricated by a chemical etching process. Wetting and corrosion of the micropillars was studied over long-time duration in comparison with flat surface, before and after intermittent and continuous exposures to saline water for 168 h. Wetting was characterized by measuring the static water contact angle on the test surfaces and their corrosion by electrochemical polarization tests (electrolyte: 3.5 wt.% sodium chloride solution). The relationship between the nature of wetting of the test surfaces and their corrosion was examined. Micropillars showed predominantly composite wetting over a long time, which imparted an effective resistance against corrosion over a long time to the SS304 surface. When compared to the flat surface, the corrosion rates of the micropillars were lower by two orders of magnitude, prior to and also upon long-time contact with the NaCl solution. Micropillars lowered corrosion due to composite wetting, i.e., solid-liquid-air interface that reduced the area that was in contact with the NaCl solution. The efficiency of corrosion inhibition (η) of micropillars was 88% before long-time contact, 84% after intermittent contact, and 77% after continuous contact with NaCl solution. Topographical modification in the form of micropillars that can impart composite wetting is an effective route to induce long-term anticorrosion ability to the SS304 surface.
10
Santhosh, B., S. Narayanan, and C. Padmanabhan. "Nonlinear Dynamics of Shrouded Turbine Blade System with Impact and Friction." Applied Mechanics and Materials 706 (December 2014): 81–92. http://dx.doi.org/10.4028/www.scientific.net/amm.706.81.
Анотація:
Dry friction dampers are passive devices used to reduce the resonant vibration amplitudes in turbine bladed systems. In shrouded turbine blade systems, in addition to the stick- slip motion induced by dry friction during the contact state in the tangential direction, the interface also undergoes intermittent separation in the normal direction. The problem can thus be treated as a combination of impact and friction. In this work, the dynamics of dry friction damped oscillators which are representative models of dry friction damped bladed system is investigated. A one dimensional contact model which is capable of modeling the interface under constant and variable normal load is used. The steady state periodic solutions are obtained by multi - harmonic balance method (MHBM). Frequency response plots are generated for different values of normal load using the arc length continuation procedure. The MHBM solutions are validated using numerical integration. A single degree of freedom (dof) model under constant normal load with constant and variable friction coefficients, a dry friction damped two dof system under constant normal load and a two dof system under variable normal load are investigated. In the presence of variable normal load, the system shows multivalued frequency response and jump phenomenon. The optimal value of the normal load which gives minimum resonant response is also obtained.
Дисертації з теми "Interface à contact intermittent":
1
Cruz, Fierro Oscar Eduardo de la. "Contributions to the Study of Intermittent Contact Haptic Interfaces." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS071.
Анотація:
Les interfaces à retour d'effort sont des systèmes robotisés permettant d'interagir gestuellement de façon naturelle avec des environnements virtuels ou distants. Ces dispositifs sont utilisés dans différents contextes tels que la téléopération (e.g. nucléaire, sous-marine, spatiale), le manufacturing, les jeux vidéo, l'éducation, la médecine ou la rééducation, pour ne citer que quelques exemples. Pour les applications en réalité virtuelle, les utilisateurs manipulent généralement ces interfaces à l'aide d'une poignée qui est reliée mécaniquement au robot. Ce lien a une influence importante puisqu'il conduit l'utilisateur à ressentir la présence du robot même en espace libre (frottements, vibrations, inertie de la structure mécanique du robot), ce qui réduit le réalisme de l'interaction. Les interfaces à contacts intermittents (CI) constituent une alternative prometteuse pour essayer de surmonter ces inconvénients. Elles proposent de suivre les mouvements de l'utilisateur à faible distance en espace libre et de ne venir à son contact que lorsque l'on veut appliquer un retour d'effort. Elles visent de cette façon à améliorer le réalisme des interactions. Cette thèse s'intéresse à l'étude et à l'amélioration des performances d'une telle interface CIForce feedback interfaces are robotic systems allowing natural motion interactions with virtual or remote environments. They are employed in several domains such as remote handling (e.g. nuclear, subsea, space), manufacturing, entertainment, education, medicine and rehabilitation, just to mention the most popular. In virtual reality (VR) applications, the user typically holds a handle that is mechanically linked to the end-effector of the robot. This link has a non-negligible influence since the presence of the robot can be felt (friction, inertia and vibrations of the mechanical structure) even in free space, decreasing the realism of the interaction. Intermittent-contact haptic interfaces (IC-HIs) represent a promising approach to cope with this issue. These interfaces track and closely follow (without contact) the user movements in free space and come to his/her contact only when force feedback is required. This way IC interfaces aim to improve the realism of the interactions. The thesis presented concerns the study and improvement of such IC-His
2
Gonzalez, Franck. "Contributions au développement d'une interface haptique à contacts intermittents." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066068/document.
Анотація:
Les interfaces haptiques permettent à un opérateur d'interagir avec un environnement virtuel ou distant via le sens du toucher.La majorité des interfaces de l'état de l'art restent au contact de l’utilisateur pendant toute la durée de la manipulation. La liaison permanente entre le robot et l’opérateur nuit à la qualité de l’interaction, notamment en réduisant la transparence en espace libre. Ce problème est d’autant plus prégnant dans le cadre des interfaces haptiques dextres.Cette thèse a pour objectif d'étudier la possibilité d'augmenter la transparence et le réalisme de l'interaction à travers le développement d’interfaces à contacts intermittents. Il s’agit de déconnecter le robot de l'utilisateur lorsqu’aucun contact avec l’environnement n’est nécessaire. Un état de l’art des performances de la manipulation humaine, des interfaces haptiques dextres ainsi que des travaux relatifs au contact intermittent, est d’abord présenté. Un effecteur plan pour le contact intermittent est ensuite conçu. Il est installé à l’extrémité distale d'une interface haptique et plusieurs solutions sont envisagées pour sa loi de commande. Les performances de dix utilisateurs sont comparées dans le cadre d'une tâche de détection de contact en utilisant d'une part l'effecteur adapté au contact intermittent, d'autre part une interface haptique classique. L'élaboration d'une interface permettant une interaction plus naturelle avec l'environnement est ensuite initiée par l'élaboration d'une méthodologie de choix des zones de contact de la main à prendre en compte dans la conception d'une interface haptique. Des perspectives sont finalement données quant à l'extension de ces résultats à une interface haptique dextre à contacts intermittentsHaptic interfaces allow an operator to interact with a virtual environment through the sense of touch. Nowadays, most existing interfaces are mechanically connected to the user's hand throughout the simulation. Therefore he or she interacts with the virtual environment by means of a handle. Thus the interaction is neither natural nor intuitive, and the permanent connection between the robot and the operator is the source of perturbations which prevent the interaction from being perfectly transparent and realistic. The goal of this study is to increase transparency as much as possible by disconnecting the robot from the user when s/he is not in contact with the virtual environment, through the design of a dexterous haptic interface allowing for a more natural interaction than with a classical interface taking into account only one contact point. A state-of-the-art of dexterous haptic interfaces and another for intermittent contact devices are first gathered, and the human performances that should be taken into account for the design of a dexterous haptic interface are analysed. A bidirectional end-effector for intermittent contact is then devised. It is set up at the tip of a haptic interface and several solutions are tested for its control. The performances of six users are compared on the context of a contact detection task, first using the intermittent contact end-effector, then using a classical haptic device. A methodology for the choice of the hand contact areas that should be taken into account in the design of a dexterous haptic interface to enhance the naturalness of the interaction is proposed. Finally, some perspectives are given as for the extension of this study for the design of a dexterous encounter-type haptic interface
3
Guda, Vamsi Krishna. "Contributions à l'utilisation de cobots comme interfaces haptiques à contact intermittent en réalité virtuelle." Thesis, Ecole centrale de Nantes, 2022. http://www.theses.fr/2022ECDN0033.
Анотація:
La réalité virtuelle (RV) est de plus en plus utilisée dans des simulations industrielles mais la possibilité de toucher les objets manque rapidement par exemple pour juger de la qualité perçue dans la conception de véhicule automobile. Les interfaces haptiques actuels ne permettent de restituer aisément la notion de texture, l’approche envisagée est donc une interface à contact intermittent. Un cobot vient positionner une surface mobile à l’endroit du contact avec un objet virtuel pour permettre un contact physique avec la main de l’opérateur.Les contributions de cette thèse portent sur plusieurs aspects : le placement du robot, la modélisation de l’opérateur, la gestion du déplacement et de la vitesse du robot et la détection des intentions de l’opérateur. Le placement du robot est choisi pourpermettre d’atteindre les différentes zones de travail et pour assurer une sécurité passive en rendant impossible au robot de heurter la têteet le buste de l’opérateur en position normale de travail, i.e. assis dans un fauteuil. Un modèle de l'utilisateur, incluant un torse et desbras, est conçu et testé pour suivre les mouvements de l'utilisateur en temps réel. L’interaction est possible sur un ensemble de pose prédéfinies que l’utilisateur enchaine comme il le désire. Différentes stratégies sont proposées pour prédire les intentions de l'utilisateur. Les aspects clés de la prédiction sont basés sur la direction du regard et la position de la main de l'utilisateur. Une étudeexpérimentale ainsi que l'analyse qui en découle montrent l’apport de la prise en compte de la direction du regard. L’intérêt d’introduire des points dit « de sécurité » pour éloigner le robot de l’opérateur et permettre des déplacements rapides du robot est mis en évidenceVirtual reality (VR) is evolving and being used in industrial simulations but the possibility to touch objects is missing, for example to judge the perceived quality in the design of a car. The current haptic interfaces do not allow to easily restore the notion of texture, therefore an approach is considered “intermittent contact interface” to achieve this. A cobot positions a mobile surface at the point of contact with a virtual object to allow physical contact with the operator's hand. The contributions of this thesis concern several aspects: the placement of the robot, the modeling of the operator, the management of the displacement and the speed of the robot and the detection of the operator's intentions. The placement of the robot is chosen to allow reaching the different working areas and to ensure passive safety by making it impossible for the robot to hit the head and chest of the operator in a normal working position, i.e. sitting in a chair. A model of the user, including a torso and arms, is designed and tested to follow the user's movements in real time Interaction is possible on a set of predefined poses that the user chains together as desired. Different strategies are proposed to predict the user's intentions. The key aspects of the prediction are based on the gaze direction and the hand position of the user. An experimental study as well as the resulting analysis show the contribution of taking into account the gaze direction. The interest of introducing "safety" points to move the robot away from the operator and allow fast robot movements is highlighted
4
Mercado, Garcia Victor Rodrigo. "Contribution to the Study of Usability and Haptic Feedback of Encountered-Type Haptic Displays." Thesis, Rennes, INSA, 2021. https://tel.archives-ouvertes.fr/tel-03789676.
Анотація:
Les interfaces à contact intermittent (ICIs) sont des dispositifs robotisés qui suivent la main de l'utilisateur et se placent en position de rencontre lorsque l'utilisateur souhaite toucher des objets dans une réalité virtuelle (RV) immersive. Malgré ces avantages, plusieurs défis doivent encore être résolus en matière d'utilisabilité et de retour haptique. Cette thèse présente une série de contributions pour tirer profit des ICIs à travers des axes de recherche l'utilisabilité et le retour haptique.La première contribution dans l'axe de l'utilisabilité a étudié la conception de techniques de sécurité pour les ICIs basés sur le retour visuel. Ensuite, une série de techniques d'interaction pour l'exploration de surface avec les ICIs est présentée. Ces techniques ont exploré plusieurs combinaisons de facteurs liés au contrôle des ICIs afin de donner aux utilisateurs la sensation de toucher une grande surface dans la RV.Concernant l'axe du retour haptique, nous présentons une approche pour le rendu de grandes surfaces multi-texturées. Cette approche est basée sur un accessoire cylindrique rotatif, multi-texturé, attaché à l'effecteur d'un ICIs. Finalement, la thèse présente une contribution à la manipulation d'objets dans la RV en utilisant un objet tangible détachable et un ICIs. Cette contribution permet de créer, détruire et reconfigurer des objets tangibles dans des environnements virtuels immersifsEncountered-Type Haptic Displays (ETHDs) are robotic devices that follow the users' hand and locate themselves in an encountered position when users want to touch objects in immersive virtual reality (VR). Despite these advantages, several challenges are yet to be solved in matters of usability and haptic feedback. This thesis presents a series of contributions to leverage ETHDs through research axes for both usability and haptic feedback.The first contribution in the usability axis studied the design of safety techniques for ETHDs based on visual feedback. Then, a series of interaction techniques for surface exploration with ETHDs is presented. These techniques explored several combinations of factors related to ETHD control to give users the sensation of touching a large surface in VR.Concerning the haptic feedback axis, we introduce an approach for large, multi-textured surface rendering. This approach is based on a rotating, multi-textured, cylindrical prop attached to an ETHD's end-effector. Finally, the thesis presents a contribution to object manipulation in VR using a detachable tangible object and an ETHD. This contribution permits creating, destroying and reconfiguring tangible objects in immersive virtual environments
5
Chabrier, Anthony. "Etude théorique et expérimentale d'une interface à retour d'effort augmenté." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066383/document.
Анотація:
Les interactions physiques comportent divers gestes dextres et sont sources d’échanges d’informations très variées. Différentes interfaces haptiques ont été développées pour reproduire ces mouvements dextres et ces interactions. Cependant il est impossible actuellement de concevoir une interface simulant tous les types d’interactions avec un retour haptique réaliste. Je propose d’identifier les interactions les plus importantes et les zones de la main les plus intéressantes à stimuler, et ensuite d’étudier comment associer certains dispositifs pour améliorer le ressenti de l’utilisateur. Il semble intéressant de développer une interface se concentrant sur : la transition entre les mouvements de l’utilisateur en espace libre et au contact d’un objet, le retour d’effort, et enfin la déformation locale et globale de la pulpe, et ce sur 4 zones : les phalanges distales du pouce, de l’index et de l’annulaire, et le côté extérieur de l’index. Afin de rendre cela réalisable dans le cadre d’une thèse, j’ai entrepris de développer une interface à retour d’effort à contacts intermittents sur le pouce et l’index, tout en prenant en compte l’ajout futur d’un retour plus complet. Pour cela, j’ai tout d’abord élaboré un effecteur instrumenté permettant d’acquérir, sans contact, la position de la dernière phalange d’un doigt en 6D. Puis j’ai dimensionné une interface de type gant à deux doigts, capable de déplacer, en 6D, ces effecteurs dans l’ensemble de l’espace de travail des doigts et de générer un retour d’effort quand cela est nécessaire. Enfin j’ai étudié la commande de ce système lors de ses différentes phases de fonctionnement et ses performances ont été évaluéesPhysical interactions involve highly dexterous movements and exchanges of diverse information. Numerous haptic interfaces were developed with the aim to reproduce these dexterous gestures and each of these interactions. However, it is technically impossible to date to design an interface simulating all of them with a realistic haptic feedback.I propose to identify the most important interactions and the hand areas the most interesting to stimulate, and then to study how associate different devices to improve the feeling of an operator. I decided to focus on: the transition between user’s movements in free space and in contact with an object, force feedback, and finally local and global deformation of the fingers’ pulp, with an emphasis on the four following areas: distal phalanges of the thumb, index and middle finger, plus the external side of the index finger. To make this possible during a PhD, I finally decided to focus on an intermittent contact force feedback interface for the thumb and index fingers, by taking into account the future integration of more complete feedback. Therefore, I first developed instrumented end-effectors able to remotely measure the 6D configuration of the distal phalanx of the fingers without any contact with them. Then I dimensioned and designed a glove-type haptic interface with two fingers. This device allows controlling the position and orientation of the intermittent contact end-effectors in 6D throughout the whole fingers workspace. It is also able to generated force feedback when necessary. Finally, I studied the control laws of this interface in all its operating phases and its performances were evaluated
6
Dubourg, Fabien. "Nanomécanique et dynamique des polymères par microscopie de force en contact intermittent." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2002. http://tel.archives-ouvertes.fr/tel-00007198.
Анотація:
Ce mémoire présente une étude des propriétés de polymères à petite (nano) échelle, par les modes de modulation d'amplitude (« Tapping ») et de modulation de fréquence (« Non-contact » résonant) de la Microscopie à Force Atomique. Il débute par la détermination des origines physiques du contraste d'images obtenues sur une surface de copolymère tri- séquencé : la reconstruction d'une section d'image grâce aux courbes d'approche- retrait permet d'en attribuer le contraste aux seules variations de la réponse viscoélastique du copolymère (i.e. de montrer l'absence de contribution topographique au contraste). L'étape suivante est une évaluation des constantes physiques des deux nanophases du même copolymère tri- séquencé par l'analyse de courbes d'approche- retrait en mode modulation d'amplitude. Pour cela nous modélisons analytiquement et numériquement l'interaction non-linéaire et dissipative entre nano-pointe oscillante et polymère. Puis un résultat expérimental charnière montre qu'en mode modulation d'amplitude avec un facteur de qualité Q suffisamment élevé un matériau de raideur locale très faible peut apparaître dur et sa topographie être mesurée sans déformation. Cela signifie que, sur un échantillon suffisamment mou, la variation contrôlée du facteur de qualité Q permet d'accéder sélectivement aux propriétés mécaniques ou topographiques. La dernière partie concerne la dépendance d'échelle de la viscoélasticité d'un polymère fondu enchevêtré. On utilise le mode modulation de fréquence avec un facteur Q très élevé : lorsque l'indentation de la pointe dans le polymère et leur temps d'interaction atteignent des valeurs seuils, la puissance nécessaire pour maintenir une amplitude d'oscillation constante présente une augmentation abrupte. On montre que cette augmentation de la dissipation est due au passage d'une relaxation moléculaire rapide (<10-8 s, mouvement de type Rouse à faible indentation) à une relaxation beaucoup plus lente (>10-5s, désenchevêtrement lorsque la taille de l'objet indenté dépasse celle de la maille du réseau de chaînes). Cette transition correspond à une variation de profondeur d'indentation de quelques angströms.
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Dubourg, Fabien. "Nanomécanique et dynamique des polymères par microscopie de force en contact intermittent." Phd thesis, Bordeaux 1, 2002. http://www.theses.fr/2002BOR12630.
Анотація:
Ce travail est une étude des propriétés de matériaux polymères à l'échelle du nanomètre par les modes dynamiques de modulation d'amplitude dit " Tapping " et de modulation de fréquence dit " Non-Contact Résonant" de la microscopie à force atomique. Il débute par la détermination des origines physiques du contraste d'images obtenues sur des surfaces de coplymères triséquencés. Ce contraste se révèle être dû aux variations nanométriques des propriétés viscoélastiques. L'étape suivante est une évaluation des constantes physiques des deux nanophases du copolymère triséquencé par l'analyse des courbes d'approche-retrait en modulation d'amplitude. Pour cela nous décrivons les effets sur l'oscillateur des interactions conservatives et non-conservatives entre la pointe et le polymère. Puis un résultat expérimental charnière montre qu'en mode modulation d'amplitude avec un facteur de qualité Q suffisamment élevé un matériau de raideur locale très faible peut apparaître dur pour l'oscillateur, si bien que sa structure non-déformée peut être déterminée. Ce durcissement apparent implique une réduction de l'aire de contact pointe-surface et par conséquent un Q élevé peut conduire à une amélioration de la résolution sur les matériaux mous en mode modulation d'amplitude. De plus ces résultats montrent que la variation du facteur de qualité Q permet d'accéder sélectivement aux propriétés mécaniques ou topographiques. La troisième et dernière partie est une étude de la dynamique dépendante d'échelle d'un polymère fondu enchevêtré, le polyisoprène ou caoutchouc d'Hévéa. Cette étude utilise le mode modulation de fréquence avec un facteur de qualité Q très élevé. Une transition entre deux types de mouvements moléculaires de temps de relaxation très différents est créée et détectée par l'oscillateur. La transition entre une relaxation moléculaire locale de type Rouse et une relaxation par reptation forcée amène un changement radical de l'énergie à fournir pour maintenir une amplitude d'oscillation constante de la nanopointe.
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Jason, Bronwin Anastasia. "An adaptive user interface model for contact centres." Thesis, Nelson Mandela Metropolitan University, 2008. http://hdl.handle.net/10948/989.
Анотація:
Contact centres (CC), are the primary interaction point between a company and its customers and these are rapidly expanding in terms of both workforce and economic scope. An important challenge for today's CC solutions is to increase the speed at which CCAs retrieve information to answer customer queries. CCAs, however, differ in their ability to respond to these queries and do not interact with the computer user interface (UI) in the same way as they each have different capabilities, experience and expertise. Studies have provided empirical support that user performance can be increased when the computer UI characteristics match the user skill level. Adaptive user interfaces (AUIs) are the key to creating personalised systems. Their sole task is to provide an interface most suitable to users' needs whilst facilitating the users' varying skill levels. The aim of this research was to develop an AUI model for CCs to support and improve the expertise level of CCAs. A literature review of CCs, user expertise, AUIs and existing AUI models resulted in the proposal of an AUI model for CCs. The proposed AUI model was described in terms of its architecture, component-level and interface design. An AUI prototype was developed as a proof-of-concept of the proposed AUI model. A literature review on existing AUI evaluation approaches resulted in an evaluation strategy for the proposed AUI model. The AUI prototype was evaluated according to the evaluation strategy that was identified. User testing incorporating eye-tracking and a post-test questionnaire was used to determine the usefulness and usability of the AUI prototype. Significant results were found with regards to user satisfaction ratings, the learnability of the AUI prototype and its effectiveness. This dissertation makes an important contribution in the design of an AUI model that supports and improves the expertise level of CCAs. The model could be used to assist the development of CC applications incorporating AUIs. Future research is however needed to evaluate the effect of the proposed AUI model in a larger CC environment.
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Quinn, Amy May. "The study of contact phenomena using ultrasound." Thesis, University of Bristol, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271847.
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Singh, Akash. "An intelligent user interface model for contact centre operations." Thesis, Nelson Mandela Metropolitan University, 2007. http://hdl.handle.net/10948/d1011399.
Анотація:
Contact Centres (CCs) are at the forefront of interaction between an organisation and its customers. Currently, 17 percent of all inbound calls are not resolved on the first call by the first agent attending to that call. This is due to the inability of the contact centre agents (CCAs) to diagnose customer queries and find adequate solutions in an effective and efficient manner. The aim of this research is to develop an intelligent user interface (IUI) model to support and improve CC operations. A literature review of existing IUI architectures, modelbased design and existing CC software together with a field study of CCs has resulted in the design of an IUI model for CCs. The proposed IUI model is described in terms of its architecture, component-level design and interface design. An IUI prototype has been developed as a proof of concept of the proposed IUI model. The IUI prototype was evaluated in order to determine to what extent it supports problem identification and query resolution. User testing, incorporating the use of eye tracking and a post-test questionnaire, was used in order to determine the usability and usefulness of the prototype. The results of this evaluation show that the users were highly satisfied with the task support and query resolution assistance provided by the IUI prototype. This research resulted in the design of an IUI model for the domain of CCs. This model can be used to assist the development of CC applications incorporating IUIs. Use of the proposed IUI model is expected to support and enhance the effectiveness and efficiency of CC operations. Further research is needed to conduct a longitudinal study to determine the impact of IUIs in the CC domain.
Книги з теми "Interface à contact intermittent":
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Kikuchi, Masato. A non-contact computer interface. Manchester: UMIST, 1994.
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Olofsson, U., and R. Lewis. Wheel-rail interface handbook. Boca Raton, FL: CRC Press, 2009.
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Vladimír, Kolář. Contact stress and settlement in the structure-soil interface. Prague: Academia, 1991.
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Association, International Heavy Haul. Guidelines to best practices for heavy haul railway operations: Wheel and rail interface issues. Virginia Beach, Va: International Heavy Haul Association, 2001.
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McKay, Iain. The strategic desktop: Usability engineering for the contact centre workstation. Edinburgh: Spotlight, 2003.
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Clack, Timothy, and Marcus Brittain. Archaeologies of Cultural Contact: At the Interface. Oxford University Press, 2022.
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Olofsson, U., and Lewis R. Wheel-Rail Interface Handbook. Elsevier Science & Technology, 2009.
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R, Lewis. Wheel - Rail Interface Handbook. Taylor & Francis Group, 2009.
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Lipski, John M. Palenquero and Spanish in Contact: Exploring the Interface. Benjamins Publishing Company, John, 2020.
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Lipski, John M. Palenquero and Spanish in Contact: Exploring the Interface. Benjamins Publishing Company, John, 2020.
Частини книг з теми "Interface à contact intermittent":
1
Voigtländer, Bert. "Intermittent Contact Mode/Tapping Mode." In Scanning Probe Microscopy, 205–21. Berlin, Heidelberg: Springer Berlin Heidelberg, 2015. http://dx.doi.org/10.1007/978-3-662-45240-0_15.
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Voigtländer, Bert. "Intermittent Contact Mode/Tapping Mode." In Atomic Force Microscopy, 231–53. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-13654-3_14.
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Tadros, Tharwat. "Contact Angle." In Encyclopedia of Colloid and Interface Science, 147. Berlin, Heidelberg: Springer Berlin Heidelberg, 2013. http://dx.doi.org/10.1007/978-3-642-20665-8_55.
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Storz, Matthias, and Peter Vielsack. "Numerical Sensitivity of a Dynamical System with Dry Friction and Unilateral and Intermittent Constraints." In Contact Mechanics, 427–30. Boston, MA: Springer US, 1995. http://dx.doi.org/10.1007/978-1-4615-1983-6_58.
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Collins, W. D., M. S. Khalil, S. Quegan, D. Smith, and D. A. W. Taylor. "Interface Pressures in Contact Zones." In European Consortium for Mathematics in Industry, 121–24. Wiesbaden: Vieweg+Teubner Verlag, 1992. http://dx.doi.org/10.1007/978-3-663-09834-8_20.
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Wang, Yansong. "Friction in Conformal Contact Interface." In Encyclopedia of Tribology, 1311–15. Boston, MA: Springer US, 2013. http://dx.doi.org/10.1007/978-0-387-92897-5_31.
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Langbein, Dieter. "Interface Tension and Contact Angle." In Springer Tracts in Modern Physics, 21–39. Berlin, Heidelberg: Springer Berlin Heidelberg, 2002. http://dx.doi.org/10.1007/3-540-45267-2_2.
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Fitzgerald, R. H. "Calcar/Collar Contact in Cemented Total Hip Arthroplasty." In Implant Bone Interface, 147–48. London: Springer London, 1990. http://dx.doi.org/10.1007/978-1-4471-1811-4_20.
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Pastor, Elsa. "Direct Flame Contact." In Encyclopedia of Wildfires and Wildland-Urban Interface (WUI) Fires, 1–7. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-319-51727-8_64-1.
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Pastor, Elsa. "Direct Flame Contact." In Encyclopedia of Wildfires and Wildland-Urban Interface (WUI) Fires, 221–26. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-319-52090-2_64.
Тези доповідей конференцій з теми "Interface à contact intermittent":
1
Mugisha, Stanley, Matteo Zoppi, Rezia Molfino, Vamsi Guda, Christine Chevallereau, and Damien Chablat. "Safe Collaboration Between Human and Robot in a Context of Intermittent Haptique Interface." In ASME 2021 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/detc2021-71518.
Анотація:
Abstract In the list of interfaces used to make virtual reality, haptic interfaces allow users to touch a virtual world with their hands. Traditionally, the user’s hand touches the end effector of a robotic arm. When there is no contact, the robotic arm is passive; when there is contact, the arm suppresses mobility to the user’s hand in certain directions. Unfortunately, the passive mode is never completely seamless to the user. Haptic interfaces with intermittent contacts are interfaces using industrial robots that move towards the user when contact needs to be made. As the user is immersed via a virtual reality Head Mounted Display (HMD), he cannot perceive the danger of a collision when he changes his area of interest in the virtual environment. The objective of this article is to describe movement strategies for the robot to be as fast as possible on the contact zone while guaranteeing safety. This work uses the concept of predicting the position of the user through his gaze direction and the position of his dominant hand (the one touching the object). A motion generation algorithm is proposed and then applied to a UR5 robot with an HTC vive tracker system for an industrial application involving the analysis of materials in the interior of a car.
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Peng, Wei, James Kiely, and Yiao-Tee Hsia. "Wear Analysis of Head-Disk Interface During Contact." In ASME/STLE 2004 International Joint Tribology Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/trib2004-64050.
Анотація:
To achieve a higher storage density in a hard disk drive, the fly height of the air bearing slider, as part of the magnetic spacing, has to be minimized. At an ultra-low fly height, the intermittent / continuous contact at the head–disk interface (HDI) is unavoidable and directly affects the mechanical and magnetic performance of the hard disk drive, and is of great interest. The HDI wear has a non-linear and time-varying nature due to the change of contact force and roughness. To predict the HDI wear evolution, an iterative model of Coupled Head And Disk (CHAD) wear, is developed based on the contact mechanics. In this model, a composite transient wear coefficient is adopted and multiple phases of the wear evolution are established. A comprehensive contact stiffness is derived to characterize the contact at the HDI. The abrasive and adhesive wear is calculated based on the extended Archard’s wear law. The plastic and elastic contact areas are calculated with a 3-D sliding contact model. Based on the CHAD wear model, for the first time, the coupling between head and disk wear evolutions is thoroughly investigated. Accelerated wear tests have also been performed to verify the disk wear effect on the slider wear. A wear coefficient drop with time is observed during the tests and it is attributed to a wear mechanism shift from abrasive to adhesive wear. A shift in the type of contact from plastic to elastic accounts for the wear mechanism change.
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Petrov, E. P. "Multiharmonic Analysis of Nonlinear Whole Engine Dynamics With Bladed Disc-Casing Rubbing Contacts." In ASME Turbo Expo 2012: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/gt2012-68474.
Анотація:
A method has been developed for frequency domain analysis of steady state forced response in gas turbine engines in the presence of rubbing and snubbing contacts between bladed discs and casing and between other rotor and stator engine components. The multiharmonic contact interface elements have been derived for modelling the nonlinear contact interactions: (i) at bearings and (ii) bladed disc-casing rubbing contacts with using flexible models for rotor and stator structures. The elements allow for the asymmetry of the casing, the discrete blade contacts with casing, individual blade-casing gap values, nonlinear dependency of the contact forces on rotor-stator incursion and friction forces, intermittent contacts between blades and the casing. High accuracy and computational efficiency of the methods and models developed has been demonstrated on a set of test cases and on an example of analysis of a realistic gas turbine structure.
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Ito, Takahiro, Jun Shimizu, Hideyuki Nakayama, and Yutaka Kukita. "Effects of Contact Line Condition on Excitation of Internal Waves Confined by a Cylindrical Wall." In 12th International Conference on Nuclear Engineering. ASMEDC, 2004. http://dx.doi.org/10.1115/icone12-49187.
Анотація:
Standing internal waves can be excited when fluids overlaid in a stationary enclosure are subjected to harmonic, vertical oscillations. The oscillatory deformation of the fluid-fluid interface near the wall, due to the limited mobility of the fluid-fluid-wall contact line, can play an important role in the excitation of waves. The contact line may or may not move depending on the amplitude of fluid excitation. When it moves, it may do so only in a limited portion of each cycle. We analyze numerically the wave excitation associated with such nonlinear, intermittent motions of the contact line. The analytical results consistently reproduce the experimental results, and give insight into the interactions between the contact line motions and the waves on the interface.
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Chuprakov, Dimitry, and Romain Prioul. "Hydraulic Fracture Height Containment by Weak Horizontal Interfaces." In SPE Hydraulic Fracturing Technology Conference. SPE, 2015. http://dx.doi.org/10.2118/spe-173337-ms.
Анотація:
Abstract Weak formation bedding planes create a unique mechanism for hydraulic fracture height containment. They arrest the vertical growth of hydraulic fracture. The propagation across them may or may not occur. To quantify this fracture behavior, first we developed an analytical model of the elastic T-shaped fracture contact with frictional and cohesional interfaces. The model evaluates the fracture blunting and the shear activation of the interfaces. It predicts the buildup of the net pressure necessary for the fracture to cross the given interface. Next we conduct numerical simulations of the 3D fracture propagation in a formation with closely spaced horizontal interfaces. These simulations manifest intermittent and decelerated fracture growth in height, especially with low-viscosity fracturing fluids. This mechanism of fracture height containment is independent of the multilayer stress-contrast mechanism used conventionally. Combined with the stress mechanism, the fracture height containment model could alleviate the problem of height growth overestimation in some fracturing simulation cases.
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Frammelsberger, Werner, Guenther Benstetter, Thomas Schweinboeck, Richard Stamp, and Janice Kiely. "Advanced Analysis of Thin and Ultrathin SiO2 Films and SiO2/Si Interfaces with Combined Atomic Force Microscopy Methods." In ISTFA 2003. ASM International, 2003. http://dx.doi.org/10.31399/asm.cp.istfa2003p0406.
Анотація:
Abstract In this work a procedure is presented to look beneath the surface of a SiO2 film and to study the impact of the SiO2/Si interface morphology on the tunneling current, with high lateral resolution, by use of combined Conductive Atomic Force Microscopy (C-AFM) and Intermittent-Contact AFM (IC-AFM) measurements. Evidence is given that interface structures do have direct influence on the distribution of high current spots in MOS capacitors.
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Wang, Zhaofeng. "Flip-Chip Bump Interface Failure Mechanisms In Plastic BGA Packages and Failure Analysis Process Flow." In ISTFA 2008. ASM International, 2008. http://dx.doi.org/10.31399/asm.cp.istfa2008p0036.
Анотація:
Abstract The present paper studies several failure mechanisms at both UBM and Cu substrate side for flip-chip die open contact failures in multi-chip-module plastic BGA-LGA packages. A unique failure analysis process flow, starting from non-disturbance inspection of x-ray, substrate and die level C-SAM, bump x-section followed by a bump interface integrity test including under-fill etching and bump pull test and/or substrate etch has been developed. Four different types of failure mechanism in multiple chip module that are associated with open/intermittent contact, ranging from device layout design, UBM forming process defect, to assembly related bump-substrate interface delamination have been identified. The established FA process has been proved to be efficient and accurate with repeatable result. It has facilitated and accelarated new product qualification processes for a line of high power MCM modules.
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Kiely, James, and Yiao-Tee Hsia. "A Novel Method of Characterizing Slider Dynamic Motion During Intermittent Head-Disk Contact." In World Tribology Congress III. ASMEDC, 2005. http://dx.doi.org/10.1115/wtc2005-63195.
Анотація:
Characterization of slider motion induced by contact is becoming a critical aspect of developing advanced head-disc interfaces. While vertical motion induced by contact has been studied, very little is known about down-track motion. We have introduced a new technique where the down-track motion is captured and the dynamics in three dimensions are analyzed. We have applied this technique to measure the position of a slider as it transitions from flying to making full contact with the media surface. We find that slider motion varies considerably with varying levels of interference and that motion in all three directions is considerable. Spectral decomposition is used to identify the vibration modes that are excited in each direction, and we find that for most of the test velocities, vertical modes give rise to motion in the two orthogonal directions. In addition, we present a depiction of the vertical, down-track, and off-track position changes by plotting the position of the slider in real space coordinates to help visualize more completely the slider trajectory. Analysis of motion identifies that at some levels of interference, a majority of motion is repeatable, but that non-repeatable components increase with the amount of interference. Additionally, down-track motion is the only component whose magnitude increases monotonically with increasing interference.
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Gu, Weiwei, Zili Xu, and Lv Qiang. "Forced Response of Shrouded Blades With Intermittent Dry Friction Force." In ASME Turbo Expo 2008: Power for Land, Sea, and Air. ASMEDC, 2008. http://dx.doi.org/10.1115/gt2008-51041.
Анотація:
The gap friction damper model is presented in this paper, which is employed to simulate the friction forces at the contact points of the shroud interface. Using the harmonic balance method (HBM), the friction force can be approximated by a series of harmonic functions. The governing differential equations of blade motion are transformed into a set of nonlinear algebraic equations, which can be solved iteratively to yield the steady-state response. The results show that the forced response is attenuated due to the additional damping introduced by frictional slip. The predicted results agree well with those of the Runge-Kutta method. In addition, the effect of parameters of damping structures such as the gap size, friction coefficient and normal load on the forced response of blades were studied. The results show that increasing the damper gap size causes a increase in resonant response. However, the increment isn’t obvious. In addition, an increase in friction coefficient or normal load decreases the forced response of blade.
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Lee, Sung-Chang, and Andreas A. Polycarpou. "Predicting Fly-Height Modulation and Contact Forces in Ultra-Low Flying Head-Disk Interfaces Using a Tri-State Switching Dynamic Contact Model." In STLE/ASME 2001 International Joint Tribology Conference. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/trib-nano2001-104.
Анотація:
Abstract In order to achieve higher recording densities up to 1 Tbit/In2 using conventional recording technologies, the recording slider will need to “fly” within 5 nm or less from the rotating disk. In such ultra-low flying height regimes, intermittent head/disk contact is unavoidable. Head/disk contact can cause large vibrations of the recording slider in the normal and lateral (off-track) directions as well as damage the disk due to large dynamic contact forces. This paper describes a simple continuum mechanics-based model that includes the dynamics of a flying head/disk interface (HDI) as well as the contact dynamics. Specifically, a lumped parameter one degree-of-freedom, three state nonlinear dynamic model representing the normal dynamics of the HDI and an asperity-based contact model are developed. The effects of realistic (dynamic microwaviness) and harmonic input excitations, contact stiffness (surface roughness) and air-bearing force during contact on fly-height modulation (FHM) and contact force are investigated. Based on the tri-state model predictions, design guidelines for reduced FHM and dynamic contact force are suggested.
Звіти організацій з теми "Interface à contact intermittent":
1
McMichael, L. Contact Interface Verification for DYNA3D Scenario 1: Basic Contact. Office of Scientific and Technical Information (OSTI), May 2006. http://dx.doi.org/10.2172/898003.
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McMichael, L. Contact Interface Verification for DYNA3D Scenario 2: Multi-Surface Contact. Office of Scientific and Technical Information (OSTI), May 2006. http://dx.doi.org/10.2172/898011.
3
Khounsary, A. M., D. Chojnowski, L. Assoufid, and W. M. Worek. Thermal contact resistance across a copper-silicon interface. Office of Scientific and Technical Information (OSTI), October 1997. http://dx.doi.org/10.2172/554855.
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Phelan, P. E., R. C. Niemann, and T. H. Nicol. Thermal contact resistance for a CU/G-10CR interface in a cylindrical geometry. Office of Scientific and Technical Information (OSTI), July 1996. http://dx.doi.org/10.2172/285441.
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Lever, James, Susan Taylor, Arnold Song, Zoe Courville, Ross Lieblappen, and Jason Weale. The mechanics of snow friction as revealed by micro-scale interface observations. Engineer Research and Development Center (U.S.), December 2021. http://dx.doi.org/10.21079/11681/42761.
Анотація:
The mechanics of snow friction are central to competitive skiing, safe winter driving and efficient polar sleds. For nearly 80 years, prevailing theory has postulated that self-lubrication accounts for low kinetic friction on snow: dry-contact sliding warms snow grains to the melting point, and further sliding produces meltwater layers that lubricate the interface. We sought to verify that self-lubrication occurs at the grain scale and to quantify the evolution of real contact area to aid modeling. We used high-resolution (15 μm) infrared thermography to observe the warming of stationary snow under a rotating polyethylene slider. Surprisingly, we did not observe melting at contacting snow grains despite low friction values. In some cases, slider shear failed inter-granular bonds and produced widespread snow movement with no persistent contacts to melt (μ < 0.03). When the snow grains did not move and persistent contacts evolved, the slider abraded rather than melted the grains at low resistance (μ < 0.05). Optical microscopy revealed that the abraded particles deposited in air pockets between grains and thereby carried heat away from the interface, a process not included in current models. Overall, our results challenge whether self-lubrication is indeed the dominant mechanism underlying low snow kinetic friction.
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Mozley, Peter, James Evans, and Thomas Dewers. Area of Interest 1, CO2 at the Interface: Nature and Dynamics of the Reservoir/Caprock Contact and Implications for Carbon Storage Performance. Office of Scientific and Technical Information (OSTI), October 2014. http://dx.doi.org/10.2172/1177773.
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Lever, James, Susan Taylor, Garrett Hoch, and Charles Daghlian. Evidence that abrasion can govern snow kinetic friction. Engineer Research and Development Center (U.S.), December 2021. http://dx.doi.org/10.21079/11681/42646.
Анотація:
The long-accepted theory to explain why snow is slippery postulates self-lubrication: frictional heat from sliding melts and thereby lubricates the contacting snow grains. We recently published micro-scale interface observations that contradicted this explanation: contacting snow grains abraded and did not melt under a polyethylene slider, despite low friction values. Here we provide additional observational and theoretical evidence that abrasion can govern snow kinetic friction. We obtained coordinated infrared, visible-light and scanning-electron micrographs that confirm that the evolving shapes observed during our tribometer tests are contacting snow grains polished by abrasion, and that the wear particles can sinter together and fill the adjacent pore spaces. Furthermore, dry-contact abrasive wear reasonably predicts the evolution of snow-slider contact area and sliding-heat-source theory confirms that contact temperatures would not reach 0°C during our tribometer tests. Importantly, published measurements of interface temperatures also indicate that melting did not occur during field tests on sleds and skis. Although prevailing theory anticipates a transition from dry to lubricated contact along a slider, we suggest that dry-contact abrasion and heat flow can prevent this transition from occurring for snow-friction scenarios of practical interest.
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Lever, James, Emily Asenath-Smith, Susan Taylor, and Austin Lines. Assessing the mechanisms thought to govern ice and snow friction and their interplay with substrate brittle behavior. Engineer Research and Development Center (U.S.), December 2021. http://dx.doi.org/10.21079/1168142742.
Анотація:
Sliding friction on ice and snow is characteristically low at temperatures common on Earth’s surface. This slipperiness underlies efficient sleds, winter sports, and the need for specialized tires. Friction can also play micro-mechanical role affecting ice compressive and crushing strengths. Researchers have proposed several mechanisms thought to govern ice and snow friction, but directly validating the underlying mechanics has been difficult. This may be changing, as instruments capable of micro-scale measurements and imaging are now being brought to bear on friction studies. Nevertheless, given the broad regimes of practical interest (interaction length, temperature, speed, pressure, slider properties, etc.), it may be unrealistic to expect that a single mechanism accounts for why ice and snow are slippery. Because bulk ice, and the ice grains that constitute snow, are solids near their melting point at terrestrial temperatures, most research has focused on whether a lubricating water film forms at the interface with a slider. However, ice is extremely brittle, and dry-contact abrasion and wear at the front of sliders could prevent or delay a transition to lubricated contact. Also, water is a poor lubricant, and lubricating films thick enough to separate surface asperities may not form for many systems of interest. This article aims to assess our knowledge of the mechanics underlying ice and snow friction.
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Heymsfield, Ernie, and Jeb Tingle. State of the practice in pavement structural design/analysis codes relevant to airfield pavement design. Engineer Research and Development Center (U.S.), May 2021. http://dx.doi.org/10.21079/11681/40542.
Анотація:
An airfield pavement structure is designed to support aircraft live loads for a specified pavement design life. Computer codes are available to assist the engineer in designing an airfield pavement structure. Pavement structural design is generally a function of five criteria: the pavement structural configuration, materials, the applied loading, ambient conditions, and how pavement failure is defined. The two typical types of pavement structures, rigid and flexible, provide load support in fundamentally different ways and develop different stress distributions at the pavement – base interface. Airfield pavement structural design is unique due to the large concentrated dynamic loads that a pavement structure endures to support aircraft movements. Aircraft live loads that accompany aircraft movements are characterized in terms of the load magnitude, load area (tire-pavement contact surface), aircraft speed, movement frequency, landing gear configuration, and wheel coverage. The typical methods used for pavement structural design can be categorized into three approaches: empirical methods, analytical (closed-form) solutions, and numerical (finite element analysis) approaches. This article examines computational approaches used for airfield pavement structural design to summarize the state-of-the-practice and to identify opportunities for future advancements. United States and non-U.S. airfield pavement structural codes are reviewed in this article considering their computational methodology and intrinsic qualities.
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Shmulevich, Itzhak, Shrini Upadhyaya, Dror Rubinstein, Zvika Asaf, and Jeffrey P. Mitchell. Developing Simulation Tool for the Prediction of Cohesive Behavior Agricultural Materials Using Discrete Element Modeling. United States Department of Agriculture, October 2011. http://dx.doi.org/10.32747/2011.7697108.bard.
Анотація:
The underlying similarity between soils, grains, fertilizers, concentrated animal feed, pellets, and mixtures is that they are all granular materials used in agriculture. Modeling such materials is a complex process due to the spatial variability of such media, the origin of the material (natural or biological), the nonlinearity of these materials, the contact phenomenon and flow that occur at the interface zone and between these granular materials, as well as the dynamic effect of the interaction process. The lack of a tool for studying such materials has limited the understanding of the phenomena relevant to them, which in turn has led to energy loss and poor quality products. The objective of this study was to develop a reliable prediction simulation tool for cohesive agricultural particle materials using Discrete Element Modeling (DEM). The specific objectives of this study were (1) to develop and verify a 3D cohesionless agricultural soil-tillage tool interaction model that enables the prediction of displacement and flow in the soil media, as well as forces acting on various tillage tools, using the discrete element method; (2) to develop a micro model for the DEM formulation by creating a cohesive contact model based on liquid bridge forces for various agriculture materials; (3) to extend the model to include both plastic and cohesive behavior of various materials, such as grain and soil structures (e.g., compaction level), textures (e.g., clay, loam, several grains), and moisture contents; (4) to develop a method to obtain the parameters for the cohesion contact model to represent specific materials. A DEM model was developed that can represent both plastic and cohesive behavior of soil. Soil cohesive behavior was achieved by considering tensile force between elements. The developed DEM model well represented the effect of wedge shape on soil behavior and reaction force. Laboratory test results showed that wedge penetration resistance in highly compacted soil was two times greater than that in low compacted soil, whereas DEM simulation with parameters obtained from the test of low compacted soil could not simply be extended to that of high compacted soil. The modified model took into account soil failure strength that could be changed with soil compaction. A three dimensional representation composed of normal displacement, shear failure strength and tensile failure strength was proposed to design mechanical properties between elements. The model based on the liquid bridge theory. An inter particle tension force measurement tool was developed and calibrated A comprehensive study of the parameters of the contact model for the DEM taking into account the cohesive/water-bridge was performed on various agricultural grains using this measurement tool. The modified DEM model was compared and validated against the test results. With the newly developed model and procedure for determination of DEM parameters, we could reproduce the high compacted soil behavior and reaction forces both qualitatively and quantitatively for the soil conditions and wedge shapes used in this study. Moreover, the effect of wedge shape on soil behavior and reaction force was well represented with the same parameters. During the research we made use of the commercial PFC3D to analyze soil tillage implements. An investigation was made of three different head drillers. A comparison of three commonly used soil tillage systems was completed, such as moldboard plow, disc plow and chisel plow. It can be concluded that the soil condition after plowing by the specific implement can be predicted by the DEM model. The chisel plow is the most economic tool for increasing soil porosity. The moldboard is the best tool for soil manipulation. It can be concluded that the discrete element simulation can be used as a reliable engineering tool for soil-implement interaction quantitatively and qualitatively.