EFFECT OF INITIAL CONTACT LOCATION ON MULTIASPERITY NANOCONTACT: QUASICONTINUUM SIMULATION

NANO ◽  
2014 ◽  
Vol 09 (01) ◽  
pp. 1450004
Author(s):  
WU-GUI JIANG ◽  
SHUANG XU ◽  
ZHENG-WEI WANG
Keyword(s):  
Contact Process ◽  
Copper Substrate ◽  
Wave Crest ◽  
Initial Contact ◽  
Displacement Curve ◽  
Quasicontinuum Method ◽  
Contact Stage ◽  
Wave Trough ◽  
Contact Models ◽  
Microscopic Deformation

Two nanocontact models with different initial contact locations are built to simulate the process of the multiasperity nanocontact for investigating the effect of initial contact location on the nanocontact process by using the quasicontinuum method. The indenter is initially located on the top of the middle wave crest (MWC) of the substrate and the top of the wave trough on the left side (LWT) of the substrate, respectively. The microscopic deformation mechanism, the load–displacement curve and the nanohardness–displacement curve are examined. It is found that the deformation mechanisms in the two multiasperity contact models are different. During the initial contact stage, in the MWC model, the twinning deformation dominates the whole contact process, while in the LMT model many Lomer-Cottrell locks are generated in the copper substrate, which inhibits the occurrence of twinning deformation.

Directional Stability and Control of Ships in Waves

1972 ◽  
Vol 16 (03) ◽  
pp. 205-218
Author(s):  
Haruzo Eda
Keyword(s):  
Automatic Control ◽  
Gain Control ◽  
Small Region ◽  
Wave Crest ◽  
Following Seas ◽  
Directional Stability ◽  
Wave Trough ◽  
Calm Water ◽  
Hull Forms ◽  
And Control

The stability and oscillatory motions of ships (automatically steered and unsteered) in the horizontal plane were examined on a digital computer for the case of regular following seas. Available hydrodynamic data for Series 60 hull forms were used. Analysis of directional stability was made for the case of zero encounter frequency (i.e., the ship runs at high speeds equal to the wave celerity). The ship (which is hydrodynamically stable without automatic control in calm water) is directionally unstable in following seas except for the small region near the ascending node of the waves. Addition of automatic control can give the ship directional stability when it is located on the wave trough, but not when it is located on the wave crest. At relatively high frequency (i.e., at low speeds in following seas), the rudder and control system are almost incapable of reducing oscillatory motion. Violent rudder activity in following seas can be decreased by reducing the yaw-rate-gain control constant and by increasing the rudder-response-time constant.

The Operation of Cool Edit Pro in Corpus-Based Spoken Language

2013 ◽  
Vol 694-697 ◽  
pp. 2383-2387
Author(s):  
Jie Chen ◽  
Jing Chen
Keyword(s):  
Sound Wave ◽  
Native Speaker ◽  
Spoken Language ◽  
Short Wave ◽  
Wave Crest ◽  
Sharp Wave ◽  
Wave Trough ◽  
Long Wave ◽  
Autonomic Learning ◽  
Language Corpus

Corpus refers to the database of language materials. Cool Edit Pro is a media edit software. This paper explores how to construct spoken language corpus, how to use cool edit pro 2 to make sound wave contrast and give the experimenters an intuitive observation from their own speech waveforms. The key is to offer the obvious waveforms contrast among the sampling waveform of the native speaker, the original and unmodified one of the experimenter and the new waveform of the experimenter after modifications and teachers instructions, which makes the oral autonomic learning more possible and scientific. From long wave or short wave, wave trough or wave crest, smooth wave or sharp wave, the experimenters deviations can be easily identified from the standard during the autonomic practices and efficiently make corrections. Additionally, experimenter also can observe the improvements frequently, which means this experiment more instructive.

Wave Measurements at Eastern Green Canyon During Hurricane Ike

2009 ◽  
Author(s):  
Oriol Rijken ◽  
Adam Bangs
Keyword(s):  
Wave Height ◽  
Wave Energy ◽  
Repetitive Sequences ◽  
Wave Crest ◽  
Hurricane Ike ◽  
Wave Trough ◽  
Wave Measurements ◽  
Wave Event ◽  
Measurement Location ◽  
Insight Into

Wave measurements were obtained at an Eastern Green Canyon location during hurricane Ike in September 2009. The eye of the hurricane passed approximately 68 nautical miles to the South West of the measurement location. The significant wave height was above 30 ft for about 20 hours and above 40 ft for about 5.5 hours. The wave time series provide an insight into the wave field as the storm approaches and leaves the location. One of the interesting features observed was that there were repetitive sequences, where each sequence consisted of a period of increased wave energy followed by periods of reduced wave energy. Each sequence lasted approximately one hour. Measured wave crest, wave trough and wave height distributions are discussed. One unique wave event was observed. This event was characterized by a predictably-sized crest followed by a very deep trough.

Nonlinear Crest Height Distribution in Three-Dimensional Ocean Waves

2008 ◽  
Author(s):  
Felice Arena ◽  
Alfredo Ascanelli
Keyword(s):  
Water Depth ◽  
Three Dimensional ◽  
Ocean Waves ◽  
Second Order ◽  
Wave Crest ◽  
Height Distribution ◽  
Order Model ◽  
Rayleigh Law ◽  
Wave Trough ◽  
Finite Water Depth

The interest and the studies on nonlinear waves are increased recently for their importance in the interaction with floating and fixed bodies. It is also well known that nonlinearities influence wave crest and wave trough distributions, both deviating from Rayleigh law. In this paper a theoretical crest distribution is obtained taking into account the extension of Boccotti’s Quasi Determinism theory, up to the second order for the case of three-dimensional waves, in finite water depth. To this purpose the Fedele & Arena [2005] distribution is generalized to three-dimensional waves on an arbitrary water depth. The comparison with Forristall second order model shows the theoretical confirmation of his conclusion: the crest distribution in deep water for long-crested and short crested waves are very close to each other; in shallow water the crest heights in three dimensional waves are greater than values given by long-crested model.

scholarly journals WAVE-INDUCED FLOW AND NEARSHORE SUSPENDED SEDIMENT

1988 ◽  
Vol 1 (21) ◽  
pp. 108 ◽  
Author(s):  
J.C. Doering ◽  
A.J. Bowen
Keyword(s):  
Sediment Transport ◽  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Sediment Concentration ◽  
Accurate Prediction ◽  
Wave Crest ◽  
Wave Trough ◽  
Induced Flow ◽  
Wave Induced ◽  
Velocity Skewness

It has been realized for nearly one hundred years that the transport of sediment is related to the characteristics of a wave, in particular its shape. Cornish (1898) noticed that the shoreward velocity associated with a wave crest was more effective at moving coarse sediment than was the seaward velocity associated with the wave trough. Cornish's observation was consistent with the theory of Stokes (1847), which predicts the onshore velocity associated with the wave crest is stronger and of shorter duration than the offshore velocity associated with the wave trough. This horizontal asymmetry of the cross-shore flow, which is a reflection of the wave shape, is known as velocity skewness. It has been suggested that "the existence of the beach depends on small departures from symmetry in the velocity field balancing the tendency for gravity to move material offshore"(Bowen, 1980). Although the concept of velocity skewness has been incorporated into detailed predictors of sediment transport (Bowen, 1980; Bailard and Inman, 1981) it is only one of many facets that needs to be understood in order to make the accurate prediction of sediment transport realizable. A comprehension of sediment transport is hampered by both an incomplete knowledge of the hydrodynamics and a lack of instrumentation to directly measure instantaneous sediment concentration and the accurate prediction of sediment transport is probably the most enigmatic problem in coastal engineering. Occasionally, suspended sediment concentration has been inferred from in situ pumps and hand-held tubes, but these methods lack the temporal and spatial resolution necessary to elucidate the details of the interaction between the waveinduced flow and the sediment. Recently, a miniature optical backscatter sensor (MOBS), which provides a time series of suspended sediment concentration at a "point", was developed by Downing et al. (1981). During a recent field experiment a vertical array of 5 of these optical backscatter sensors and a colocated flow meter was deployed close to the sea bed. These colocated measurements provide a unique opportunity to investigate the response of near-bed suspended sediment concentration to the wave-induced flow.

Analysis of the German Navy Stability Standard BV 1030 With Respect to Operability in Heavy Weather

2014 ◽  
Author(s):  
Stefan Krüger ◽  
Hannes Hatecke ◽  
Andreas Rinke ◽  
Klaus Tammen
Keyword(s):  
Fuel Efficiency ◽  
Wave Crest ◽  
Ship Motions ◽  
Safety Level ◽  
Wave Trough ◽  
Close Cooperation ◽  
Hull Forms ◽  
The Stability ◽  
German Navy ◽  
The University

The stability standard of the German Navy — the BV 1030 — was developed in the mid-sixties of the last century in close cooperation with the German Navy Authorities (now BAIINBw) and the University of Hamburg. Other than the stability standards used for commercial shipping, the BV 1030 is based on righting and heeling lever balances for each individual loading condition of each individual ship. Different types of heeling moments have to be assumed in several combinations and they have to be balanced against the righting levers of the ship. Not only the still water stability curve is subject to this lever balance, but also wave crest and wave trough situations are subject to the stability analysis. The BV 1030 stability standard further requires a minimum stability if the ship is on the wave crest. Since this stability standard is in force, the German Navy never experienced a stability accident. The development of new hull forms with the focus on fuel efficiency has widely brought up new problems in heavy weather, for example the vulnerability for parametric rolling. It was therefore of interest for the German Authorities (BAIIN) whether the existing stability standard has sufficient safety to cover also these phenomena connected to more modern hull forms. Therefore an analysis was carried out in close cooperation between BAIINBw, MARS and TUHH where the operability of several ships of the German Navy was analyzed with numerical sea keeping computations. The nonlinear sea keeping code E4ROLLS was used which allows the computation of time series of the ship motions in irregular, short crested seas. From these computations, operational limits could be derived, or, vice versa, the required stability to guarantee a certain operability. The results showed that the concept of the German BV 1030 stability standard provides a significantly higher safety level compared to IMO standard for commercial ships. The results did also show that for modern hull forms, some adjustments to the existing safety standard were found to be useful to better cope with righting arm fluctuations in longitudinal waves.

Initial Contact Behavior of Nanograined Ni-25at.%Al Film During Nanoindentation

2004 ◽  
Vol 841 ◽  
Author(s):  
Han. Li ◽  
Alfonso H. W. Ngan
Keyword(s):  
Thin Film ◽  
Repeated Loading ◽  
Initial Contact ◽  
Al Alloy ◽  
Alloy Thin Film ◽  
Thin Film Sample ◽  
Film Sample ◽  
Microscopy Imaging ◽  
Contact Stage ◽  
Average Grain Size

ABSTRACTCyclic indentation was performed on standard fused quartz, single crystal Ni3Al (111) and nanocrystalline Ni-25at. %Al alloy thin film with average grain size of a few nanometers. For the thin film sample, it is found the scattering of the effective Young's modulus at small depths goes far beyond the expectation from effects due to surface roughness alone. Three representative deformation mechanisms during initial contact stage were identified to be responsible for the scattering with the assistance of immediate pre and post indentation atomic force microscopy imaging. Furthermore, repeated loading was found to stiffen the thin film sample, but not the bulk ones.

Molecular Dynamics Simulation of a Rigid Sphere Indenting a Copper Substrate

2012 ◽  
Author(s):  
Ding Jia ◽  
Longqiu Li ◽  
Andrey Ovcharenko ◽  
Wenping Song ◽  
Guangyu Zhang
Keyword(s):  
Molecular Dynamics ◽  
Md Simulation ◽  
Copper Substrate ◽  
Three Dimensional ◽  
Atomic Scale ◽  
Dynamics Simulation ◽  
Rigid Sphere ◽  
Displacement Curve ◽  
Loading And Unloading ◽  
Force Displacement

Three-dimensional molecular dynamics (MD) simulation is used to study the atomic-scale indentation process of a spherical diamond tip in contact with a copper substrate. In the indentation simulations, the force-displacement curve is obtained and compared with a modified elastic solution of Hertz. The contact area under different indentation depths is also investigated. The force-displacement curve under different maximum indentation depths is obtained to investigate elastic-plastic deformation during the loading and unloading processes.

Nonlinear Crest Height Distribution in Three-Dimensional Ocean Waves

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
Felice Arena ◽  
Alfredo Ascanelli
Keyword(s):  
Water Depth ◽  
Three Dimensional ◽  
Ocean Waves ◽  
Order Theory ◽  
Second Order ◽  
Wave Crest ◽  
Height Distribution ◽  
Random Waves ◽  
Weakly Nonlinear ◽  
Wave Trough

The interest and studies on nonlinear waves are increased recently for their importance in the interaction with floating and fixed bodies. It is also well-known that nonlinearities influence wave crest and wave trough distributions, both deviating from the Rayleigh law. In this paper, a theoretical crest distribution is obtained, taking into account the extension of Boccotti’s quasideterminism theory (1982, “On Ocean Waves With High Crests,” Meccanica, 17, pp. 16–19), up to the second order for the case of three-dimensional waves in finite water depth. To this purpose, the Fedele and Arena (2005, “Weakly Nonlinear Statistics of High Random Waves,” Phys. Fluids, 17(026601), pp. 1–10) distribution is generalized to three-dimensional waves on an arbitrary water depth. The comparison with Forristall’s second order model (2000, “Wave Crest Distributions: Observations and Second-Order Theory,” J. Phys. Oceanogr., 30(8), pp. 1931–1943) shows the theoretical confirmation of his conclusion: The crest distribution in deep water for long-crested and short-crested waves are very close to each other; in shallow water the crest heights in three-dimensional waves are greater than values given by the long-crested model.

scholarly journals A computational simulation study on the dynamic response of high-speed wheel–rail system in rolling contact

2018 ◽  
Vol 10 (11) ◽  
pp. 168781401880921 ◽  
Author(s):  
Xiaoqi Ma ◽  
Lin Jing ◽  
Liangliang Han
Keyword(s):  
High Speed ◽  
Lateral Displacement ◽  
Equivalent Stress ◽  
Contact Process ◽  
Contact Forces ◽  
Rolling Contact ◽  
Initial Contact ◽  
Vertical Acceleration ◽  
Rail System ◽  
Train Speed

The dynamic wheel–rail responses during the rolling contact process for high-speed trains were investigated using the explicit finite element code LS-DYNA 971. The influence of train speed on the wheel–rail contact forces (including the vertical, longitudinal, and lateral forces), von Mises equivalent stress, equivalent plastic strain, vertical acceleration of the axle, and the lateral displacement of the initial contact point on the tread, were examined and discussed. Simulation results show that the lateral and longitudinal wheel–rail contact forces are very smaller than the corresponding vertical contact forces, and they seem to be insensitive to train speed. The peak value of dynamic vertical wheel–rail contact force is approximately 2.66 times larger than the average quasi-static value. The elliptical wheel–rail contact patches have multiple stress extreme points due to the plastic deformation of the wheel tread and top surface of the rail. The vertical acceleration value of the axle in the steady condition is around ±5 m/s2 for the perfected wheel–rail system with the running speed below 300 km/h.

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