Статті в журналах з теми "Contact interface evolution"
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1
Marshall, M. B., R. Lewis, R. S. Dwyer-Joyce, U. Olofsson, and S. Björklund. "Experimental Characterization of Wheel-Rail Contact Patch Evolution." Journal of Tribology 128, no. 3 (March 21, 2006): 493–504. http://dx.doi.org/10.1115/1.2197523.
Повний текст джерелаАнотація:
The contact area and pressure distribution in a wheel/rail contact is essential information required in any fatigue or wear calculations to determine design life, re-grinding, and maintenance schedules. As wheel or rail wear or surface damage takes place the contact patch size and shape will change. This leads to a redistribution of the contact stresses. The aim of this work was to use ultrasound to nondestructively quantify the stress distribution in new, worn, and damaged wheel-rail contacts. The response of a wheel/rail interface to an ultrasonic wave can be modeled as a spring. If the contact pressure is high the interface is very stiff, with few air gaps, and allows the transmission of an ultrasonic sound wave. If the pressure is low, interfacial stiffness is lower and almost all the ultrasound is reflected. A quasistatic spring model was used to determine maps of contact stiffness from wheel/rail ultrasonic reflection data. Pressure was then determined using a parallel calibration experiment. Three different contacts were investigated; those resulting from unused, worn, and sand damaged wheel and rail specimens. Measured contact pressure distributions are compared to those determined using elastic analytical and numerical elastic-plastic solutions. Unused as-machined contact surfaces had similar contact areas to predicted elastic Hertzian solutions. However, within the contact patch, the numerical models better reproduced the stress distribution, as they incorporated real surface roughness effects. The worn surfaces were smoother and more conformal, resulting in a larger contact patch and lower contact stress. Sand damaged surfaces were extremely rough and resulted in highly fragmented contact regions and high local contact stress.
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.
Повний текст джерелаАнотація:
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
Tiezzi, Paolo, and Imin Kao. "Modeling of Viscoelastic Contacts and Evolution of Limit Surface for Robotic Contact Interface." IEEE Transactions on Robotics 23, no. 2 (April 2007): 206–17. http://dx.doi.org/10.1109/tro.2006.889494.
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4
Sahli, R., G. Pallares, C. Ducottet, I. E. Ben Ali, S. Al Akhrass, M. Guibert, and J. Scheibert. "Evolution of real contact area under shear and the value of static friction of soft materials." Proceedings of the National Academy of Sciences 115, no. 3 (January 2, 2018): 471–76. http://dx.doi.org/10.1073/pnas.1706434115.
Повний текст джерелаАнотація:
The frictional properties of a rough contact interface are controlled by its area of real contact, the dynamical variations of which underlie our modern understanding of the ubiquitous rate-and-state friction law. In particular, the real contact area is proportional to the normal load, slowly increases at rest through aging, and drops at slip inception. Here, through direct measurements on various contacts involving elastomers or human fingertips, we show that the real contact area also decreases under shear, with reductions as large as 30%, starting well before macroscopic sliding. All data are captured by a single reduction law enabling excellent predictions of the static friction force. In elastomers, the area-reduction rate of individual contacts obeys a scaling law valid from micrometer-sized junctions in rough contacts to millimeter-sized smooth sphere/plane contacts. For the class of soft materials used here, our results should motivate first-order improvements of current contact mechanics models and prompt reinterpretation of the rate-and-state parameters.
5
Pei, Yu, Babak Rezaei, Xuyang Zhang, Zichuang Li, Hangjia Shen, Minghui Yang, and Jiacheng Wang. "Interface catalysis by Pt nanocluster@Ni3N for bifunctional hydrogen evolution and oxygen evolution." Materials Chemistry Frontiers 4, no. 9 (2020): 2665–72. http://dx.doi.org/10.1039/d0qm00326c.
Повний текст джерелаАнотація:
Pt@Ni3N catalysts with plentiful contact between Ni3N and Pt species were fabricated by a facile strategy. The Pt@Ni3N with low amount of Pt clusters shows excellent electrocatalytic activity of HER and OER in alkaline media.
6
Chopra, Kriti, Bhawna Burdak, Kaushal Sharma, Ajit Kembhavi, Shekhar C. Mande, and Radha Chauhan. "CoRNeA: A Pipeline to Decrypt the Inter-Protein Interfaces from Amino Acid Sequence Information." Biomolecules 10, no. 6 (June 22, 2020): 938. http://dx.doi.org/10.3390/biom10060938.
Повний текст джерелаАнотація:
Decrypting the interface residues of the protein complexes provides insight into the functions of the proteins and, hence, the overall cellular machinery. Computational methods have been devised in the past to predict the interface residues using amino acid sequence information, but all these methods have been majorly applied to predict for prokaryotic protein complexes. Since the composition and rate of evolution of the primary sequence is different between prokaryotes and eukaryotes, it is important to develop a method specifically for eukaryotic complexes. Here, we report a new hybrid pipeline for predicting the protein-protein interaction interfaces in a pairwise manner from the amino acid sequence information of the interacting proteins. It is based on the framework of Co-evolution, machine learning (Random Forest), and Network Analysis named CoRNeA trained specifically on eukaryotic protein complexes. We use Co-evolution, physicochemical properties, and contact potential as major group of features to train the Random Forest classifier. We also incorporate the intra-contact information of the individual proteins to eliminate false positives from the predictions keeping in mind that the amino acid sequence of a protein also holds information for its own folding and not only the interface propensities. Our prediction on example datasets shows that CoRNeA not only enhances the prediction of true interface residues but also reduces false positive rates significantly.
7
Li, Dongwu, Chao Xu, Ruozhang Li, and Wenming Zhang. "Contact parameters evolution of bolted joint interface under transversal random vibrations." Wear 500-501 (July 2022): 204351. http://dx.doi.org/10.1016/j.wear.2022.204351.
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8
PEYRET, N., J. L. DION, G. CHEVALLIER, and P. ARGOUL. "MICRO-SLIP INDUCED DAMPING IN PLANAR CONTACT UNDER CONSTANT AND UNIFORM NORMAL STRESS." International Journal of Applied Mechanics 02, no. 02 (June 2010): 281–304. http://dx.doi.org/10.1142/s1758825110000597.
Повний текст джерелаАнотація:
The friction between interfaces at bolted joints plays a major role in the damping of structures. This paper deals with the energy losses caused by micro-slips in the joints. The aim of this study is to define in an analytical way these energy dissipation mechanisms which we examine through the analysis of a new benchmark: the flexural vibration of a clamped-clamped beam with original positioning of the interfaces. The joints exhibit the behavior of an interface under constant and uniform normal stress. The stress and strain values are computed at the joints under the assumption of quasi-static motion. This model allows us to understand the evolution of the slip and stick regions along the joint interfaces during the loading process. The expressions of the strain and stress fields during each phase of the loading process are derived. These lead to the quantification of the dissipated energy within the interface. Using this formula, a nonlinear loss factor can then be computed. In the final part of the paper, the dynamic response of the beam is calculated using this nonlinear loss factor.
9
Si, Ting, Tong Long, Zhigang Zhai, and Xisheng Luo. "Experimental investigation of cylindrical converging shock waves interacting with a polygonal heavy gas cylinder." Journal of Fluid Mechanics 784 (November 4, 2015): 225–51. http://dx.doi.org/10.1017/jfm.2015.581.
Повний текст джерелаАнотація:
The interaction of cylindrical converging shock waves with a polygonal heavy gas cylinder is studied experimentally in a vertical annular diaphragmless shock tube. The reliability of the shock tube facility is verified in advance by capturing the cylindrical shock movements during the convergence and reflection processes using high-speed schlieren photography. Three types of air/SF6 polygonal interfaces with cross-sections of an octagon, a square and an equilateral triangle are formed by the soap film technique. A high-speed laser sheet imaging method is employed to monitor the evolution of the three polygonal interfaces subjected to the converging shock waves. In the experiments, the Mach number of the incident cylindrical shock at its first contact with each interface is maintained to be 1.35 for all three cases. The results show that the evolution of the polygonal interfaces is heavily dependent on the initial conditions, such as the interface shapes and the shock features. A theoretical model for circulation initially deposited along the air/SF6 polygonal interface is developed based on the theory of Samtaney & Zabusky (J. Fluid Mech., vol. 269, 1994, pp. 45–78). The circulation depositions along the initial interface result in the differences in flow features among the three polygonal interfaces, including the interface velocities and the perturbation growth rates. In comparison with planar shock cases, there are distinct phenomena caused by the convergence effects, including the variation of shock strength during imploding and exploding (geometric convergence), consecutive reshocks on the interface (compressibility), and special behaviours of the movement of the interface structures (phase inversion).
10
Ding, H., B. Q. Chen, H. R. Liu, C. Y. Zhang, P. Gao, and X. Y. Lu. "On the contact-line pinning in cavity formation during solid–liquid impact." Journal of Fluid Mechanics 783 (October 26, 2015): 504–25. http://dx.doi.org/10.1017/jfm.2015.574.
Повний текст джерелаАнотація:
We investigate the cavity formation during the impact of spheres and cylinders into a liquid pool by using a combination of experiments, simulations and theoretical analysis, with particular interest in contact-line pinning and its relation with the subsequent cavity evolution. The flows are simulated by a Navier–Stokes diffuse-interface solver that allows for moving contact lines. On the basis of agreement on experimentally measured quantities such as the position of the pinned contact line and the interface shape, we investigate flow details that are not accessible experimentally, identify the interface regions in the cavity formation and examine the geometric effects of impact objects. We connect wettability, inertia, geometry of the impact object, interface bending and contact-line position with the contact-line pinning by analysing the force balance at a pinned meniscus, and the result compares favourably with those from simulations and experiments. In addition to adjusting the interface bending, the object geometry also has a significant effect on the magnitude of low pressure in the liquid and the occurrence of flow separation. As a result, it is easier for an object with sharp edges to generate a cavity than a smooth object. A theoretical model based on the Rayleigh–Besant equation is developed to provide a quantitative description of the radial expansion of the cavity after the pinning of the contact line. The accuracy of the solution is greatly affected by the geometrical information on the interface connected to the pinned meniscus, showing the dependence of the global cavity dynamics on the local flows around the pinned contact line. Vertical ripple propagation on the cavity wall is found to follow the dispersion relation for the perturbation evolution on a hollow jet.
11
Benedetti, Ivano, and M. H. Aliabadi. "Computational Modelling of Brittle Failure in Polycrystalline Materials Using Cohesive-Frictional Grain-Boundary Elements." Key Engineering Materials 577-578 (September 2013): 233–36. http://dx.doi.org/10.4028/www.scientific.net/kem.577-578.233.
Повний текст джерелаАнотація:
A 3D grain-level formulation for the study of brittle failure in polycrystalline microstructures is presented. The microstructure is represented as a Voronoi tessellation and the boundary element method is used to model each crystal of the aggregate. The continuity of the aggregate is enforced through suitable conditions at the intergranular interfaces. The grain-boundary model takes into account the onset and evolution of damage by means of an irreversible linear cohesive law, able to address mixed-mode failure conditions. Upon interface failure, a non-linear frictional contact analysis is introduced for addressing the contact between micro-crack surfaces. An incremental-iterative algorithm is used for tracking the micro-degradation and cracking evolution. A numerical test shows the capability of the formulation.
12
Theodorakis, Panagiotis E., Erich A. Müller, Richard V. Craster, and Omar K. Matar. "Modelling the superspreading of surfactant-laden droplets with computer simulation." Soft Matter 11, no. 48 (2015): 9254–61. http://dx.doi.org/10.1039/c5sm02090e.
Повний текст джерелаАнотація:
Spatio-temporal evolution of a droplet undergoing surfactant-driven superspreading facilitated by surfactant adsorption from the liquid–vapour (LV) interface onto the substrate through the contact-line, and replenishment of the LV interface with surfactant from the bulk.
13
Tian, Chenglin, Haitao Sun, Linchao Dai, Rifu Li, Bo Wang, Jie Cao, Jun Wang, and Qianting Hu. "Experimental Study on Mechanical Properties and Energy Evolution Law of Coal-Rock Composite Structure under Different Interface Connection Modes." Geofluids 2022 (March 17, 2022): 1–11. http://dx.doi.org/10.1155/2022/1288463.
Повний текст джерелаАнотація:
The stability of the coal-rock composite structure is of great significance to the safety production of deep mines, and the different interface connection modes of coal and rock have an important influence on its stability. Therefore, the following work was done in this article: Firstly, the mechanical structure model of coal-rock was established, and the influence of different interface connection modes on coal rock was analyzed. Secondly, the mechanical characteristics (plastic zone, stress, and displacement) of coal-rock composite structure under different interface connection modes were studied by numerical simulation, and the energy was quantitatively analyzed by FISH language in FLAC3D. The results were as follows: (1) The interface reduces the strength of rock and increases the strength of coal in the coal-rock composite structure. (2) In the loading process, the coal body is destroyed first and the destruction range increases gradually with the increase of stress. The failure mode is mainly a plastic shear failure, and the deformation of coal is much larger than that of rock in the composite structure. (3) The interface contact mode affects the mechanical behavior of coal and rock structure. The strong contact interface influences the strength, displacement, and energy accumulation of coal and rock structure, among which the influence on energy and displacement is greater, which is helpful to the improvement of strength. Therefore, it is suggested to adopt the strong contact interface in the study of coal and rock structure.
14
Tonazzi, Davide, Francesco Massi, Mario Salipante, Laurent Baillet, and Yves Berthier. "Estimation of the Normal Contact Stiffness for Frictional Interface in Sticking and Sliding Conditions." Lubricants 7, no. 7 (July 2, 2019): 56. http://dx.doi.org/10.3390/lubricants7070056.
Повний текст джерелаАнотація:
Modeling of frictional contact systems with high accuracy needs the knowledge of several contact parameters, which are mainly related to the local phenomena at the contact interfaces and affect the complex dynamics of mechanical systems in a prominent way. This work presents a newer approach for identifying reliable values of the normal contact stiffness between surfaces in contact, in both sliding and sticking conditions. The combination of experimental tests, on a dedicated set-up, with finite element modeling, allowed for an indirect determination of the normal contact stiffness. The stiffness was found to increase with increasing contact pressure and decreasing roughness, while the evolution of surface topography and third-body rheology affected the contact stiffness when sliding.
15
Kuchuk, A., V. Kladko, Z. Adamus, M. Wzorek, M. Borysiewicz, P. Borowicz, A. Barcz, K. Golaszewska, and A. Piotrowska. "Influence of Carbon Layer on the Properties of Ni-Based Ohmic Contact to n-Type 4H-SiC." ISRN Electronics 2013 (February 28, 2013): 1–5. http://dx.doi.org/10.1155/2013/271658.
Повний текст джерелаАнотація:
Nickel-based contacts with additional interfacial layer of carbon, deposited on n-type 4H-SiC, were annealed at temperatures ranging from 600 to 1000°C and the evolution of the electrical and structural properties were analyzed by I-V measurements, SIMS, TEM, and Raman spectroscopy. Ohmic contact is formed after annealing at 800°C and minimal specific contact resistance of about 2.0×10-4 Ω cm2 has been achieved after annealing at 1000°C. The interfacial carbon is amorphous in as-deposited state and rapidly diffuses and dissolves in nickel forming graphitized carbon. This process activates interfacial reaction between Ni and SiC at lower temperature than usual and causes the formation of ohmic contact at relatively low temperature. However, our results show that the specific contact resistance as well as interface quality of contacts was not improved, if additional layer of carbon is placed between Ni and SiC.
16
Xie, Linglin, Wenyu Tang, Hang Lin, Fan Lei, Yifan Chen, Yixian Wang, and Yanlin Zhao. "Apparent Deterioration Law and Shear Failure Mode of Rock–Mortar Interface Based on Topography-Sensing Technology." Materials 16, no. 2 (January 12, 2023): 763. http://dx.doi.org/10.3390/ma16020763.
Повний текст джерелаАнотація:
As an advanced spatial technology, topography-sensing technology is comprehensive, macroscopic, and intuitive. It shows unique advantages for rock structure interpretation and has important guiding significance for the research of the shear performances of rock–mortar interface under cyclic load in rock mass engineering. In this paper, cyclic shearing tests combined with the shear surface topography-sensing technology are employed to investigate the evolution characteristics of the interface morphology and the strength deterioration of the rock–mortar interface. Primarily, mortar and three types of rocks are used to prepare different rock–mortar interfaces, which are then applied to cyclic shear loading under two constant normal stresses. Subsequently, the shear strength degradation and dilatancy characteristics of rock–mortar interfaces with varying shear times are discussed. In addition, on the basis of the non-contact three-dimensional topography-sensing technology, the apparent three-dimensional point–cloud coordinate information of rock–mortar interface before and after each shear loading is obtained, and the apparent three-dimensional topography parameters of rock–mortar interface are calculated, according to which the influences of normal stress and lithology on the topography of interface subjected to cyclic shearing loading are analyzed.
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Kim, Jeong-Min, Keesam Shin, and Je-Sik Shin. "Microstructural Evolution and Growth of Intermetallic Compounds at the Interface between Solid Cast Iron and Liquid Al–Si Alloy." Metals 10, no. 6 (June 6, 2020): 759. http://dx.doi.org/10.3390/met10060759.
Повний текст джерелаАнотація:
Compound casting has received a great deal of attention as a useful method for fabricating a single complicated part from dissimilar metallic materials. For example, in the case of automobile cylinder blocks, research is being carried out to compound cast iron with aluminum alloys. In order to manufacture such as composite parts, it is essential to control the intermetallic compound formed at the interface between two metals. In this research, the type and growth behavior of compounds formed at the interface between cast iron and aluminum, or Al–Si alloy, were investigated. It was observed that the Al5Fe2 phase was mainly formed at the interface between the pure aluminum melt and the solid cast iron, and the thickness of the interfacial compound increased proportionally with increasing contact time. On the other hand, more complex phases were formed at the interface between the Al–Si alloy melt and the solid cast iron. In the case of a specimen having a contact time of 10 min, Al4.5FeSi, Al8Fe2Si and Al5Fe2 phases appeared to occupy the largest portion of the interfacial compound region. The total thickness of the interfacial compounds also increased in proportion to the contact time.
18
Qiu, Le, Hong-Sheng Qi, and Alastair Wood. "Two-dimensional finite element analysis investigation of the heat partition ratio of a friction brake." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 232, no. 12 (February 7, 2018): 1489–501. http://dx.doi.org/10.1177/1350650118757245.
Повний текст джерелаАнотація:
A two-dimensional coupled temperature–displacement finite element model is developed for a pad-disc brake system based on a restricted rotational pad boundary condition. The evolution of pressure, heat flux, and temperature along the contact interface during braking applications is analysed with the finite element model. Results indicate that different rotational pad boundary conditions significantly impact the interface pressure distribution, which in turn affects interface temperature and heat flux distributions, and suggest that a particular pad rotation condition is most appropriate for accurately modelling friction braking processes. The importance of the thermal contact conductance in the analysis of heat transfer in friction braking is established, and it is confirmed that the heat partition ratio is not uniformly distributed along the interface under normal and high interface thermal conductance conditions.
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Wang, Chunlan, Yongle Song, and Hao Huang. "Evolution Application of Two-Dimensional MoS2-Based Field-Effect Transistors." Nanomaterials 12, no. 18 (September 18, 2022): 3233. http://dx.doi.org/10.3390/nano12183233.
Повний текст джерелаАнотація:
High-performance and low-power field-effect transistors (FETs) are the basis of integrated circuit fields, which undoubtedly require researchers to find better film channel layer materials and improve device structure technology. MoS2 has recently shown a special two-dimensional (2D) structure and superior photoelectric performance, and it has shown new potential for next-generation electronics. However, the natural atomic layer thickness and large specific surface area of MoS2 make the contact interface and dielectric interface have a great influence on the performance of MoS2 FET. Thus, we focus on its main performance improvement strategies, including optimizing the contact behavior, regulating the conductive channel, and rationalizing the dielectric layer. On this basis, we summarize the applications of 2D MoS2 FETs in key and emerging fields, specifically involving logic, RF circuits, optoelectronic devices, biosensors, piezoelectric devices, and synaptic transistors. As a whole, we discuss the state-of-the-art, key merits, and limitations of each of these 2D MoS2-based FET systems, and prospects in the future.
20
Cui, Jianlei, Huanhuan Mei, Jianwei Zhang, Zhengjie Fan, Jun Yang, Wenjun Wang, Hironori Tohmyoh, and Xuesong Mei. "Interfacial Contact Behavior between CNTs and AgNW with Molecular Dynamics Simulation." Materials 13, no. 6 (March 12, 2020): 1290. http://dx.doi.org/10.3390/ma13061290.
Повний текст джерелаАнотація:
The behavior at an interface between carbon nanotubes (CNTs) and silver nanowire (AgNW) could hardly be observed experimentally on an atomic scale, and the interaction is difficult to accurately calculate due to nanometer size effects. In this work, the contact behavior is studied with the molecular dynamics (MD) simulation, which indicates that the CNTs and AgNW can move towards each other to form aligned structures with their interfaces in full contact. In these different composite systems, nanotubes may either keep their form of an inherent cylindrical structure or completely collapse into the nanoribbons that can tightly scroll on the AgNW periphery while wrapping it in a core-shell structure. Thus, the atomic configuration evolution that is affected by the van der Waals (vdW) interaction is closely analyzed to assist the understanding of interfacial contact behavior.
21
Ackroyd, B., S. Chandrasekar, and W. D. Compton. "A Model for the Contact Conditions at the Chip-Tool Interface in Machining." Journal of Tribology 125, no. 3 (June 19, 2003): 649–60. http://dx.doi.org/10.1115/1.1537747.
Повний текст джерелаАнотація:
A high-speed photographic study has been made of the chip-tool interface and its evolution when cutting pure metals with optically transparent sapphire tools. The use of a high speed camera in conjunction with an optical microscope has enabled details of the interface, including the velocity field along the interface, to be resolved at high spatial and temporal resolution while cutting at speeds between 1 mm/sec and 2000 mm/sec. The results show the chip-tool contact along this interface to be composed of four distinct regions: a region of stagnation at the cutting edge, a region of retardation adjoining the stagnation region, a region of sliding beyond the retardation region, followed by a region of metal transfer or “sticking” that is located furthest away from the cutting edge alongside the boundary of the contact. The chip and tool appear to be in intimate contact over the stagnation, retardation, and sliding regions, with sliding occurring at the interface over much of this zone of intimate contact. These observations have provided direct experimental evidence for a model of the contact conditions proposed by Enahoro and Oxley based on analytical considerations. Cutting experiments with non-oxide tools such as aluminum and high speed steel suggest that this description conditions is equally applicable to tool materials other than sapphire.
22
Yang, Jinwen, Jianming Zhao, and Xiaosheng Liu. "Numerical Study on the Evolution of Agglomerate Breakage and Microstructure of Angular Gravel in Cyclic Soil-Structure Interface Test." Advances in Civil Engineering 2019 (February 6, 2019): 1–24. http://dx.doi.org/10.1155/2019/7232613.
Повний текст джерелаАнотація:
The discrete element method (DEM) was used to study the behavior of crushable angular gravel in the cyclic soil-structure interface test. Two shapes of agglomerates were simulated by filling two scanned angular gravels with spheres connected by bonds that were given the shear and normal strength complying with Gaussian distribution to simulate random flaws. The proportion of these two shapes to constitute a numerical sample was named composite pattern. Good agreement in terms of macromechanical behavior between DEM simulation and laboratory test results has been attained. Agglomerate breakage is deeply influenced by the interface shearing behavior and mainly occurs on the interface and the space nearby. Graphs of interface after shearing are introduced to directly and clearly reflect microbehavior of breakage. The evolution of microstructure including anisotropies and coordination numbers is significantly influenced by normal stress and agglomerate breakage, and composite pattern determines the magnitudes of shear force anisotropy and coordination numbers. The evolution of contact orientation distribution is the forming cause of the “adjustment phase,” during which once the shearing direction changes, the values of contact normal anisotropy and normal force anisotropy will slump to their nadir and then rise back again.
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LEVER, JAMES H., SUSAN TAYLOR, ARNOLD J. SONG, ZOE R. COURVILLE, ROSS LIEBLAPPEN, and JASON C. WEALE. "The mechanics of snow friction as revealed by micro-scale interface observations." Journal of Glaciology 64, no. 243 (December 4, 2017): 27–36. http://dx.doi.org/10.1017/jog.2017.76.
Повний текст джерелаАнотація:
ABSTRACTThe 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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Li, Yufeng, and Aric Menon. "A Model of Slider/Disk Interface Wear for Proximity Recording." Journal of Tribology 118, no. 4 (October 1, 1996): 813–18. http://dx.doi.org/10.1115/1.2831613.
Повний текст джерелаАнотація:
Slider/disk interface wear is inevitable for ultra-low flying hard disk drives and is the central issue for proximity recording. While disk wear has been addressed in the literature, slider wear has been largely considered to be trivial and is ignored. However, with the improvement of disk overcoat and introduction of diamond-like-carbon overcoat on slider air bearing surface, the surface hardnesses of the slider and disk are approaching each other and, therefore, the slider surface wear becomes significant or, in some conditions, even dominant. In this study, a theoretical model is developed for semi-steady-state slider/disk interface evolution of proximity recording which takes account of both the disk and slider wear. It includes the effects of the air bearing characteristics, pitch stiffness, material properties, and surface topography of both the slider and disk. Numerical results are illustrated for typical proximity recording interface, where the evolutions of the slider, disk, contact force, and pitch angle are evaluated for various air bearing stiffnesses, material properties, and surface topographies. This model is intended to provide some fundamental understanding of the slider/disk interface evolution during proximity recording process.
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Kogut, L., and I. Etsion. "Elastic-Plastic Contact Analysis of a Sphere and a Rigid Flat." Journal of Applied Mechanics 69, no. 5 (August 16, 2002): 657–62. http://dx.doi.org/10.1115/1.1490373.
Повний текст джерелаАнотація:
An elastic-plastic finite element model for the frictionless contact of a deformable sphere pressed by a rigid flat is presented. The evolution of the elastic-plastic contact with increasing interference is analyzed revealing three distinct stages that range from fully elastic through elastic-plastic to fully plastic contact interface. The model provides dimensionless expressions for the contact load, contact area, and mean contact pressure, covering a large range of interference values from yielding inception to fully plastic regime of the spherical contact zone. Comparison with previous elastic-plastic models that were based on some arbitrary assumptions is made showing large differences.
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Greco, Giuseppe, Fabrizio Roccaforte, R. Lo Nigro, C. Bongiorno, S. Di Franco, P. Prystawko, M. Leszczyński, and Vito Raineri. "Evolution of Structural and Electrical Properties of Au/Ni Contacts onto P-GaN after Annealing." Materials Science Forum 717-720 (May 2012): 1295–98. http://dx.doi.org/10.4028/www.scientific.net/msf.717-720.1295.
Повний текст джерелаАнотація:
In this paper the structural and electrical evolution of Au/Ni contacts to p-type gallium nitride (GaN) upon annealing in different atmospheres was monitored. Rapid annealing of the contacts in an oxidizing atmosphere (N2/O2) resulted into a lower specific contact resistance (ρc) with respect to annealing in non-reacting ambient (Ar). The formation of a nickel oxide (NiO) layer was observed on the surface of the sample annealed in N2/O2 ,while was not present at the interface with p-GaN. The improvement of the contacts was associated with a reduction of the Schottky barrier height from 1.07 eV (Ar annealing) to 0.71 eV (N2/O2 annealing), as determined by the temperature dependence of the ρc. Local electrical measurements demonstrated the formation of inhomogeneous barriers. The electrical measurements were correlated with the different microstructure of the annealed contacts.
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Pisarenko, Tatiana A., G. S. Kraynova, and A. M. Frolov. "Kinetics of the Fractal Mesodefect Structure of Melt-Spun Fe70Cr15B15(Sn) Alloys during Annealing." Solid State Phenomena 247 (March 2016): 101–5. http://dx.doi.org/10.4028/www.scientific.net/ssp.247.101.
Повний текст джерелаАнотація:
We have studied the effect of tin microalloying on the kinetics of the fractal mesodefect structure of melt-spun Fe70Cr15B15(Sn) alloys during thermal loading. It is established that the morphology evolution of ribbon interfaces correlates with the kinetics of physical properties. Symmetry character of melt-spun alloys is identified by the form of fractal dimensionality spectrum. Reduction of the fractal dimension is observed at stages of both vitrification and nanocrystallization. Residual alloying by tin of the contact interface of ribbon changes a topology of the localized states that lowers the temperature of vitrification.
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Zhang, Si Feng, Xiu Guang Song, Yan Mei Li, and Kai Yao. "Study on the Interface Mechanical Characteristic of Geotechnical Prestressed Anchorage Bolt under Step Loading by Model Test." Applied Mechanics and Materials 90-93 (September 2011): 1859–64. http://dx.doi.org/10.4028/www.scientific.net/amm.90-93.1859.
Повний текст джерелаАнотація:
The development and evolution regularity of the interface shear stress for the inner bond section of geotechnical prestressed anchorage structure is directly related to the ultimate bearing capacity and its long-term durability. By adopting the similar model test and embedding the strain brick at each interfaces of inner bond section, the interface mechanical properties under step loading were systematically studied. Conclusions can be drawn as follows: the interface shear stress along the axial direction of rod is not evenly distributed, and the interface distribution shape at different radial distance from the rod axis also varies. With the gradual increase of external load, the shear stress peak point continues to move into the deep areas, and resulting in the occurrence of gradual damage mode. In the process, the peak value of shear stress also augment gradually. Along radial direction of the rod, the shear stress concentration phenomenon just distributes within a small radius around the rod body. Adopting the two stage linear function to describe the relationship of shear stress and shear displacement at contact surface is suitable.
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Liang, Mengfan, Ziyi Xiong, Yongmao Hu, Yingli Liu, Tao Shen, Shuhong Sun, and Yan Zhu. "Surface evolution of Janus Cu-Ag nanoparticles: Influence of atom arrangements and interface structures." Functional Materials Letters 13, no. 07 (October 2020): 2050037. http://dx.doi.org/10.1142/s179360472050037x.
Повний текст джерелаАнотація:
In this paper, the effect of the atom ratio and interface structure on the surface evolution of Janus Cu–Ag Nanoparticles (NPs) were studied by molecular dynamics (MDs) simulation during sintering process. The results show that Cu/Ag alloys tend to form the Cu-core@Ag-shell NPs with stable configuration in the case of excessive Ag. However, the different arrangements of atoms and interface lead to Janus Cu–Ag NPs exhibiting unique coalescence during the contact stage of sintering process, and the interface with Cu/Ag two-type atoms is more likely to diffuse. Moreover, the systems gradually change from separate NPs to a uniform Cu/Ag alloy as the temperature rising, meanwhile the shrinkage ratio of the Janus Cu–Ag NPs is stable at 80%.
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Li, Zhi Xin, Shi Ming Ji, Li Zhang, Qiao Ling Yuan, and Ming Sheng Jin. "Numerical Investigation on the Micro-Slip along Friction Interfaces." Advanced Materials Research 215 (March 2011): 286–90. http://dx.doi.org/10.4028/www.scientific.net/amr.215.286.
Повний текст джерелаАнотація:
Damping in built-up structures is often caused by energy dissipation or energy loss due to micro-slip along frictional interfaces interaction, which provides a beneficial damping mechanism and plays an important role in the dynamics vibration behavior of such structures, especially the contact stiffness and damping coefficient accounting for the kinematics joint. A detailed study the mechanics derived from the interaction interface between the different components has some embarrassment. And a careful study on the micro-slip phenomenon has been carried out using the finite element method. A classical joint configuration, the plane translation joint, has been used as the model problems. The focus of this paper is to evaluate the effect of dry friction coefficient, the external mechanics on the damping response of frictional joint interfaces interaction, to understand the evolution of the slip-stick regions along a joint interface during loading, and to quantify the amount of energy dissipation/loss during cyclic loading and its dependence on structural and loading parameters.
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Nishihara, K., J. G. Wouchuk, C. Matsuoka, R. Ishizaki, and V. V. Zhakhovsky. "Richtmyer–Meshkov instability: theory of linear and nonlinear evolution." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 368, no. 1916 (April 13, 2010): 1769–807. http://dx.doi.org/10.1098/rsta.2009.0252.
Повний текст джерелаАнотація:
A theoretical framework to study linear and nonlinear Richtmyer–Meshkov instability (RMI) is presented. This instability typically develops when an incident shock crosses a corrugated material interface separating two fluids with different thermodynamic properties. Because the contact surface is rippled, the transmitted and reflected wavefronts are also corrugated, and some circulation is generated at the material boundary. The velocity circulation is progressively modified by the sound wave field radiated by the wavefronts, and ripple growth at the contact surface reaches a constant asymptotic normal velocity when the shocks/rarefactions are distant enough. The instability growth is driven by two effects: an initial deposition of velocity circulation at the material interface by the corrugated shock fronts and its subsequent variation in time due to the sonic field of pressure perturbations radiated by the deformed shocks. First, an exact analytical model to determine the asymptotic linear growth rate is presented and its dependence on the governing parameters is briefly discussed. Instabilities referred to as RM-like, driven by localized non-uniform vorticity, also exist; they are either initially deposited or supplied by external sources. Ablative RMI and its stabilization mechanisms are discussed as an example. When the ripple amplitude increases and becomes comparable to the perturbation wavelength, the instability enters the nonlinear phase and the perturbation velocity starts to decrease. An analytical model to describe this second stage of instability evolution is presented within the limit of incompressible and irrotational fluids, based on the dynamics of the contact surface circulation. RMI in solids and liquids is also presented via molecular dynamics simulations for planar and cylindrical geometries, where we show the generation of vorticity even in viscid materials.
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Stavropoulou, Eleni, Christophe Dano, and Marc Boulon. "Experimental investigation of the mechanical behaviour of soft carbonate rock/grout interfaces for the design of offshore wind turbines." E3S Web of Conferences 92 (2019): 13006. http://dx.doi.org/10.1051/e3sconf/20199213006.
Повний текст джерелаАнотація:
Since a few years, in France, the development and construction of offshore wind farms in different sites of the country is investigated. The wind turbines will be installed in soft carbonate rock formations (calcarenite, limestone), the mechanical properties of which can vary in a significant way according to the location of the site. Once installed, the bored piles will be sealed with grout in the hosting rock. It is well known that the mechanical behaviour of piles is mainly governed by the behaviour of the interface at the contact between the structure and the hosting rock. The study of the mechanical behaviour of these interfaces, being the weakest points in terms of mechanical resistance, is of great importance for the improvement of the design methods of such infrastructures. The shear response of the rock/grout interface is studied with laboratory experiments in the 3SR lab (Grenoble). The interface's mechanical properties are characterised by a series of shear tests under Constant Normal Stiffness (CNS), these conditions being the most representative of the in-situ conditions. Interface samples of a roughness representative of the in-situ drilling traces, are tested under different levels of applied normal stiffness. The shear response is studied for both monotonic and cyclic shear paths, while all tests are performed under wet conditions. The failure mechanisms are explored, taking into account the contrasting mechanical properties of the two materials composing the interface, as well as, the evolution of the geometrical profile of the interface. The correlation between roughness and the mechanical response of the interface is investigated and the importance of an existing roughness is discussed.
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De Santis, E., G. Gasparini, A. Paoli, and S. Cudoni. "Bone-Prosthesis Implant Relation in Total Cementless Hip Arthroprosthesis." HIP International 2, no. 1 (January 1992): 27–34. http://dx.doi.org/10.1177/112070009200200105.
Повний текст джерелаАнотація:
The best relation between bone and prosthetic implant occurs when an adequate bone surface preparation and a correct implant placing ensure wide interface contact, with homogeneous load distribution (primary stability). This is necessary premise to achieve osteointegration (secondary stability) which is conditioned by factors connected with the implant (materials, surface work, lining) and with the hosting bone (pathological onset, sex, age). The evolution of bone-implant relation leads to the formation of fibrous or osseous interface; the stimulus which act on the interface (in relation with primary stability, distance between surfaces, bony heritage, etc…) infact determine a fibroblastic or osteoblastic evolution of mesenchymal elements colonizing the interface during the initial phases. In successive phases the prevailing apposition (hyperthropy) or resorption (focal or diffuse atrophy) processes is equally conditioned by mechanical factors (the position and dimension of the implant).
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Komvopoulos, K., and N. Ye. "Elastic-Plastic Finite Element Analysis for the Head-Disk Interface With Fractal Topography Description." Journal of Tribology 124, no. 4 (September 24, 2002): 775–84. http://dx.doi.org/10.1115/1.1467088.
Повний текст джерелаАнотація:
An elastic-plastic contact analysis based on a finite element model and real surface topographies was performed to elucidate the evolution of deformation at the head-disk interface. The topographies of the head and disk surfaces were represented by an equivalent profile generated using a modified two-variable Weierstrass-Mandelbrot function, with fractal parameters determined from images of head and disk surfaces. A region of the equivalent rough surface profile was selected for analysis based on topography scale considerations and contact simulation results. The evolution of plasticity and the likelihood of cracking in the overcoat and the magnetic layer are interpreted in light of results for the subsurface von Mises equivalent stress, equivalent plastic strain, and maximum first principal stress. The finite element model provides insight into the elastic-plastic deformation behavior of the layered medium in terms of the thickness, mechanical properties, and residual stress in the carbon overcoat.
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Rowson, Matthew, Chris J. Bennett, Mohammed A. Azeem, Oxana Magdysyuk, James Rouse, Ryan Lye, Joshua Davies, Simon Bray, and Peter D. Lee. "Observation of microstructure evolution during inertia friction welding using in-situ synchrotron X-ray diffraction." Journal of Synchrotron Radiation 28, no. 3 (March 19, 2021): 790–803. http://dx.doi.org/10.1107/s1600577521001569.
Повний текст джерелаАнотація:
The widespread use and development of inertia friction welding is currently restricted by an incomplete understanding of the deformation mechanisms and microstructure evolution during the process. Understanding phase transformations and lattice strains during inertia friction welding is essential for the development of robust numerical models capable of determining optimized process parameters and reducing the requirement for costly experimental trials. A unique compact rig has been designed and used in-situ with a high-speed synchrotron X-ray diffraction instrument to investigate the microstructure evolution during inertia friction welding of a high-carbon steel (BS1407). At the contact interface, the transformation from ferrite to austenite was captured in great detail, allowing for analysis of the phase fractions during the process. Measurement of the thermal response of the weld reveals that the transformation to austenite occurs 230 °C below the equilibrium start temperature of 725 °C. It is concluded that the localization of large strains around the contact interface produced as the specimens deform assists this non-equilibrium phase transformation.
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Gong, Z. Q., and K. Komvopoulos. "Contact Fatigue Analysis of an Elastic-Plastic Layered Medium With a Surface Crack in Sliding Contact With a Fractal Surface." Journal of Tribology 127, no. 3 (June 13, 2005): 503–12. http://dx.doi.org/10.1115/1.1866167.
Повний текст джерелаАнотація:
Contact fatigue of a layered medium consisting of an elastic surface layer and three elastic-plastic underlying layers in sliding contact with a rigid and rough surface was analyzed with the finite element method. To include multiscale roughness effects and self-affine surface features, the topography of the rough surface was characterized by scale-invariant fractal geometry. A contact algorithm was used to identify the critical segment of the rough surface to be used in the contact fatigue simulations. The tensile and shear stress intensity factors and the direction and dominant mode of crack growth were determined from the crack-tip stresses. The effect of surface cracking on the evolution of plasticity in the second layer and the significance of topography (fractal) parameters on crack growth are interpreted in terms of the contact pressure, stress intensity factors, and maximum equivalent plastic strain. It is shown that a transition from tensile to shear dominant mode of fatigue crack growth occurs as the crack tip approaches the interface, resulting in further crack growth almost parallel to the layer interface. The obtained results illustrate the important role of surface roughness in contact fatigue of layered media.
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Laariedh, Farah, Mihai Lazar, Pierre Cremillieu, Jean Louis Leclercq, and Dominique Planson. "Investigations on Ni-Ti-Al Ohmic Contacts Obtained on P-Type 4H-SiC." Materials Science Forum 711 (January 2012): 169–73. http://dx.doi.org/10.4028/www.scientific.net/msf.711.169.
Повний текст джерелаАнотація:
Transfer Length Method (TLM) based-structures were fabricated on 0.8 µm-thick epitaxial p-type Silicon Carbide (4H-SiC) layers. TLM mesas were defined by a 2 µm height using an SF6/O2 reactive ion etching. TLM metal patterns were obtained by a lift-off procedure and electron beam deposition of Ni, Ti, Al and Pt. The patterned samples were annealed in Argon ambient at temperature ranging from 700°C up to 1000°C in a RTA furnace with a rapid heating ramp (up to 50°C/s) to complete the ohmic contact with the p-type SiC layer. Specific contact resistances were extracted from current/voltage measurements. To identify and follow the profile evolution of constituting element in the contacts and at the SiC/contact interface, the ohmic contacts were characterized using Secondary Ion Mass Spectrometry and Energy-Dispersive X-Ray spectroscopy before and after annealing. Ohmic contacts are obtained only for the Ni/Ti/Al and Ni/Ti/Al/Ni stacking layers and not for the Ti/Al/Ti/Ni and Ti/Al/Ti/Pt/Ni compositions. The specific contact resistance of Ni/Ti/Al/Ni stacking layers was observed to decrease from 2.7×10-4 Ω.cm2 at 700°C and 6.3×10-5 Ω.cm2 at 750°C to a minimal value of 1.5×10-5 Ω.cm2 at 800°C. Ohmic contacts are obtained with a reproducibility of 80 %.
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Tasnim, Farita, Atieh Sadraei, Bianca Datta, Mina Khan, Kyung Yun Choi, Atharva Sahasrabudhe, Tomás Alfonso Vega Gálvez, et al. "Towards personalized medicine: the evolution of imperceptible health-care technologies." foresight 20, no. 6 (November 12, 2018): 589–601. http://dx.doi.org/10.1108/fs-08-2018-0075.
Повний текст джерелаАнотація:
Purpose When wearable and implantable devices first arose in the 1970s, they were rigid and clashed dramatically with our soft, pliable skin and organs. The past two decades have witnessed a major upheaval in these devices. Traditional electronics are six orders of magnitude stiffer than soft tissue. As a result, when rigid electronics are integrated with the human body, severe challenges in both mechanical and geometrical form mismatch occur. This mismatch creates an uneven contact at the interface of soft-tissue, leading to noisy and unreliable data gathering of the body’s vital signs. This paper aims to predict the role that discreet, seamless medical devices will play in personalized health care by discussing novel solutions for alleviating this interface mismatch and exploring the challenges in developing and commercializing such devices. Design methodology/approach Since the form factors of biology cannot be changed to match those of rigid devices, conformable devices that mimic the shape and mechanical properties of soft body tissue must be designed and fabricated. These conformable devices play the role of imperceptible medical interfaces. Such interfaces can help scientists and medical practitioners to gain further insights into the body by providing an accurate and reliable instrument that can conform closely to the target areas of interest for continuous, long-term monitoring of the human body, while improving user experience. Findings The authors have highlighted current attempts of mechanically adaptive devices for health care, and the authors forecast key aspects for the future of these conformable biomedical devices and the ways in which these devices will revolutionize how health care is administered or obtained. Originality/value The authors conclude this paper with the perspective on the challenges of implementing this technology for practical use, including device packaging, environmental life cycle, data privacy, industry partnership and collaboration.
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SHAO, JIANG YAN, CHANG SHU, and YONG TIAN CHEW. "A HYBRID PHASE-FIELD BASED LATTICE BOLTZMANN METHOD FOR CONTACT LINE DYNAMICS." International Journal of Modern Physics: Conference Series 19 (January 2012): 50–61. http://dx.doi.org/10.1142/s2010194512008586.
Повний текст джерелаАнотація:
A hybrid phase-field based lattice Boltzmann method (LBM) is proposed in this paper to simulate the contact line dynamics. The flow field is obtained through the lattice Boltzmann equation (LBE). Concurrently, the interface capturing is accomplished by directly solving Cahn-Hilliard equation, which is the governing equation of interface evolution. A symmetric spatial discretization scheme is adopted to enhance the stability. Compared with the conventional algorithms which solve two sets of LBEs, the present method has several advantages such as reduction of the number of variables in the solution process, decoupling the mobility with relaxation time and enabling a more direct manner to implement wetting boundary conditions. The proposed algorithm is first validated through recovering the analytical profile of a surface layer. It is then applied to simulate droplet spreading on surfaces with different wettability.
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Klapperich, C., K. Komvopoulos, and L. Pruitt. "Tribological Properties and Microstructure Evolution of Ultra-High Molecular Weight Polyethylene." Journal of Tribology 121, no. 2 (April 1, 1999): 394–402. http://dx.doi.org/10.1115/1.2833952.
Повний текст джерелаАнотація:
The friction and wear properties of unmodified ultra-high molecular weight polyethylene (UHMWPE) were investigated experimentally. Dinks of semicrystalline UHMWPE were slid against polished CoCrWNi pins in bovine serum at ranges of contact pressure and sliding speed typical of those encountered in total joint replacements. The coefficient of friction was monitored continuously during testing, and the wear rate was determined from surface profilometry measurements of worn disk surfaces accounting for strain relaxation. Scanning electron microscopy (SEM) results demonstrated that surface deterioration comprises adhesion, third-body abrasion by polyethylene wear debris, and delamination wear. The contribution of these mechanisms to the overall wear rate and the formation of wear debris depends predominantly on the contact pressure and secondarily on the sliding speed. Transmission electron microscopy (TEM) yielded new insight into the evolution of the microstructure morphology of UHMWPE during sliding. Cross sections parallel to the wear tracks obtained from various depths were analyzed with the TEM to develop a spatial mapping of the subsurface microstructure as a function of contact pressure. Alignment of crystalline regions (lamellae) in the polyethylene microstructure parallel to the sliding surface was found to occur during sliding even at relatively low contact pressures. SEM observations suggested that the highly oriented microstructure is the precursor to delamination wear, leading to the formation of wear particles larger than those produced by adhesion and third-body abrasion at the contact interface.
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Rodríguez-Tembleque, Luis, M. H. Aliabadi, and R. Abascal. "Anisotropic Contact and Wear Simulation Using Boundary Elements." Key Engineering Materials 618 (July 2014): 73–98. http://dx.doi.org/10.4028/www.scientific.net/kem.618.73.
Повний текст джерелаАнотація:
Wear is present in all mechanical interface interaction problems contact, fretting, orrolling-contact, and it is one of the main reasons for inoperability in mechanical components. Thepresented work is a review of recent research carried out by the authors [1, 2, 3]. A boundary-element-based methodology to compute anisotropic wear on 3D contact, fretting, or rolling-contact conditionsis presented. Damage on the geometries of the solids and the contact pressures evolution under or-thotropic tribological properties can be predicted using this contact framework, where the formulationuses the Boundary Element Method to compute the elastic inuence coefcients. Contact problem isbased on an Augmented Lagrangian formulation, and restrictions fullment is established by a set ofprojection functions. The boundary element anisotropic wear formulation presented is illustrated withsome examples, in which some studies about the inuence of anisotropic wear on contact variablesevolution are shown.
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Liu, Yu, Qianqi Xu, Xiaodan Sun, Guotao Yang, and Guotang Zhao. "Simulation of Delamination Evolution of Slab Ballastless Track under Vertical Impact." Shock and Vibration 2021 (June 28, 2021): 1–13. http://dx.doi.org/10.1155/2021/4022875.
Повний текст джерелаАнотація:
During the running of a high-speed train, the wheel may bounce on the rail due to the track irregularity. The wheel bounce could generate a vertical impact, leading to the initiation and expansion of delamination between layers of the track structure. In this paper, the evolution of the interfacial damage and delamination subjected to the vertical impact is simulated using finite element analysis (FEA). In the FEA, a bilinear cohesive zone model (CZM) is adopted to simulate the interface between the track slab and the CA mortar layer. For different levels of impact energy, the contact force, vertical deformation, absorbed energy, area of interfacial damage, and area of delamination are calculated and compared. The effects of the tangential and normal stiffness of the interface on the distribution of interfacial damage and delamination are investigated. The results show that the contact force, vertical deformation, absorbed energy, area of interfacial damage, and area of delamination increase with the increase of the impact energy. The area of interfacial damage in the compression stage is closely related to the tangential stiffness, whereas the area of delamination depends on the normal stiffness. The normal stiffness that gives the largest area of delamination is recommended to be taken as the lower bound of the normal stiffness for both controlling the delamination and preventing an exceedance of the track irregularity limit.
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YAN, ZHE, KAIXIANG JIANG, PENGWEI FAN, WENJUAN FANG, CUNZHOU ZHU, PENG PAN, HUI CAO, and YOUQIANG ZHANG. ""SLIDING FRICTION BETWEEN AMORPHOUS COTTON FIBER AND CHROMIUM SURFACES: A MOLECULAR DYNAMICS STUDY "." Cellulose Chemistry and Technology 56, no. 3-4 (May 5, 2022): 215–25. http://dx.doi.org/10.35812/cellulosechemtechnol.2022.56.20.
Повний текст джерелаАнотація:
"It is challenging to experimentally determine the micro-friction mechanism of cotton fiber and metal in the sliding process. The influence of load and temperature on the interface behavior during dry friction between amorphous cotton fiber and chromium, the contact interface evolution and friction coefficient are studied using reactive molecular dynamics. The simulation results show that chromium–oxygen bonds are formed on the contact interface of the friction system during the sliding process. Furthermore, the relationship between friction coefficient, temperature, and load varies with the mechanical state of cotton cellulose. The relationship is positive when the cotton cellulose is in the glassy state. However, when cotton cellulose is in a highly elastic state, its friction coefficient is negatively related to the load. This study systematically evaluated the effects of temperature and load on the slip process from the atomic scale, provided a reason for the wear of the hard materials of the friction pair, and provided theoretical support for the study of this type of friction mechanism."
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LEVER, JAMES H., SUSAN TAYLOR, GARRETT R. HOCH, and CHARLES DAGHLIAN. "Evidence that abrasion can govern snow kinetic friction." Journal of Glaciology 65, no. 249 (December 18, 2018): 68–84. http://dx.doi.org/10.1017/jog.2018.97.
Повний текст джерелаАнотація:
ABSTRACTThe 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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Maestro, Armando, Eva Santini, Dominika Zabiegaj, Sara Llamas, Francesca Ravera, Libero Liggieri, Francisco Ortega, Ramón G. Rubio, and Eduardo Guzman. "Particle and Particle-Surfactant Mixtures at Fluid Interfaces: Assembly, Morphology, and Rheological Description." Advances in Condensed Matter Physics 2015 (2015): 1–17. http://dx.doi.org/10.1155/2015/917516.
Повний текст джерелаАнотація:
We report here a review of particle-laden interfaces. We discuss the importance of the particle’s wettability, accounted for by the definition of a contact angle, on the attachment of particles to the fluid interface and how the contact angle is strongly affected by several physicochemical parameters. The different mechanisms of interfacial assembly are also addressed, being the adsorption and spreading the most widely used processes leading to the well-known adsorbed and spread layers, respectively. The different steps involved in the adsorption of the particles and the particle-surfactant mixtures from bulk to the interface are also discussed. We also include here the different equations of state provided so far to explain the interfacial behavior of the nanoparticles. Finally, we discuss the mechanical properties of the interfacial particle layers via dilatational and shear rheology. We emphasize along that section the importance of the shear rheology to know the intrinsic morphology of such particulate system and to understand how the flow-field-dependent evolution of the interfacial morphology might eventually affect some properties of materials such as foams and emulsions. We dedicated the last section to explaining the importance of the particulate interfacial systems in the stabilization of foams and emulsions.
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Madhavan, V., S. Chandrasekar, and T. N. Farris. "Direct Observations of the Chip-Tool Interface in the Low Speed Cutting of Pure Metals." Journal of Tribology 124, no. 3 (May 31, 2002): 617–26. http://dx.doi.org/10.1115/1.1398546.
Повний текст джерелаАнотація:
An experimental study of the chip-tool interface and its evolution in the low speed cutting of metals has been carried out. Specially prepared transparent glass and sapphire tools have been used to cut commercially pure metals such as lead, aluminum and copper. The chip-tool interface has been observed in situ using optical microscopy and recorded on film and video tape. By observing the motion of inhomogeneities in the chip, and profilometry of the chip and tool surfaces, it has been established that there is intimate sliding contact between the chip and the tool at and near the cutting edge. Farther away from the cutting edge and close to the end of the chip-tool contact, metal transfer and sticking are observed between the chip and tool surfaces. It has been shown that metal deposition on the rake face initially occurs near the point at which the chip curls out of contact with the tool and progressively extends outward and away from the cutting edge in conjunction with an increase in the length of contact as cutting progresses. The sticking and sliding zones are unchanged when these pure metals are machined with tungsten carbide tools.
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Novakovic, R. M., S. Delsante, and G. Borzone. "Wetting and interfacial reactions: Experimental study of the Sb-Sn-X (X = Cu, Ni) systems." Journal of Mining and Metallurgy, Section B: Metallurgy 54, no. 2 (2018): 251–60. http://dx.doi.org/10.2298/jmmb180124013n.
Повний текст джерелаАнотація:
Experimental studies of the Cu-Sb-Sn and Ni-Sb-Sn systems have been carried out by the wetting tests, followed by the analysis of the microstructural evolution occurring at the interface between the liquid alloy and solid substrate. The wetting experiments on the Sb30Sn70 / (Cu, Ni) and Sb38.4Sn61.6 / (Cu, Ni) systems have been performed by using a sessile drop apparatus. The wetting behaviour of the two alloys in contact with Cu-substrate differs from that observed in the case of Ni-substrate. The Sb-Sn alloy / substrate interface was characterised by SEM-EDS analyses. For each system, the solidliquid interactions and the phases formed at the interface were studied with the help of the corresponding phase diagrams.
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Zheng, Zhen, Junyang An, Ruiling Gong, Yuheng Zeng, Jichun Ye, Linwei Yu, Ileana Florea, Pere Roca i Cabarrocas, and Wanghua Chen. "Coupled Investigation of Contact Potential and Microstructure Evolution of Ultra-Thin AlOx for Crystalline Si Passivation." Nanomaterials 11, no. 7 (July 12, 2021): 1803. http://dx.doi.org/10.3390/nano11071803.
Повний текст джерелаАнотація:
In this work, we report the same trends for the contact potential difference measured by Kelvin probe force microscopy and the effective carrier lifetime on crystalline silicon (c-Si) wafers passivated by AlOx layers of different thicknesses and submitted to annealing under various conditions. The changes in contact potential difference values and in the effective carrier lifetimes of the wafers are discussed in view of structural changes of the c-Si/SiO2/AlOx interface thanks to high resolution transmission electron microscopy. Indeed, we observed the presence of a crystalline silicon oxide interfacial layer in as-deposited (200 °C) AlOx, and a phase transformation from crystalline to amorphous silicon oxide when they were annealed in vacuum at 300 °C.
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Yune, Young Gill, and M. D. Bryant. "Thermal Evolution of Hot Spots in Thermally Nonlinear Carbon Graphite Sliders." Journal of Tribology 111, no. 4 (October 1, 1989): 591–96. http://dx.doi.org/10.1115/1.3261982.
Повний текст джерелаАнотація:
Frictional heating of a thermal mound (or hot spot) present on the interface between a carbon graphite block sliding against a fast moving conductor is simulated. Heating of this mound due to frictional power dissipation is modeled as a collection of internal heat sources uniformly distributed within a very shallow volume (or layer) located directly beneath the sliding contact interface. The thermal mound, assumed to be motionless on and originating from the carbon graphite block, possesses the extreme temperature dependent thermal conductivity and heat capacity common to carbon graphite materials. Evolution of thermal mound temperatures from cold to hot is studied as a function of the intensity of the internal heat source distribution and the thickness of the heat source layer. For a fast moving conducting body sliding against the graphite block, it is shown that (a) an optimal heat source layer thickness exists, whereby temperatures maximize for this thickness and (b) for a sufficiently high heat source intensity, thermal instability of the mound is possible.
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Tian, Zengguo, Qian Zhi, Xiangyu Feng, Guopeng Zhang, Yafei Li, and Zhongxia Liu. "Effect of Preload on the Weld Quality of Ultrasonic Welded Carbon-Fiber-Reinforced Nylon 6 Composite." Polymers 14, no. 13 (June 29, 2022): 2650. http://dx.doi.org/10.3390/polym14132650.
Повний текст джерелаАнотація:
Ultrasonic welding (UW) of polymeric composites is significant in automobile industry; however, maintaining the perfect contact condition between workpieces is a great concern. In this study, effect of preloading and welding pressure on strengths of UWed 2.3-mm-thick short carbon fiber reinforced nylon6 (Cf/PA6) joints with poor contact between workpieces was investigated through stress simulation and energy dissipation at the faying interface. Results showed the application of preloading can increase the strength of normal joint by 18.7% under optimal welding parameters. Gaps between upper and lower workpieces decreased the joint strength significantly, especially for gaps greater than 1.5 mm. Preloading improved the strengths of the joints with gaps remarkably, where the strength of joints with 1.5 mm gap recovered to 95.5% of that the normal joint. When combining the weld nugget evolution, stress-deformation simulation during UW, and ultrasonic vibration transmission analysis, the improvement mechanism of the joint under preloading was mainly because the preloading compacted the contact between workpieces, which favored the energy transmission at faying interface.