scholarly journals Hard-material Adhesion: Which Scales of Roughness Matter?

2021 ◽  
Author(s):  
L. A. Thimons ◽  
A. Gujrati ◽  
A. Sanner ◽  
L. Pastewka ◽  
T. D. B. Jacobs
Keyword(s):  
Numerical Analysis ◽  
Adhesive Force ◽  
Work Of Adhesion ◽  
Nanometer Scale ◽  
Hard Material ◽  
Diamond Coatings ◽  
Length Scales ◽  
Atomic Interactions ◽  
Contact Models ◽  
Sphere Contact

Abstract Background Surface topography strongly modifies adhesion of hard-material contacts, yet roughness of real surfaces typically exists over many length scales, and it is not clear which of these scales has the strongest effect. Objective: This investigation aims to determine which scales of topography have the strongest effect on macroscopic adhesion. Methods Adhesion measurements were performed on technology-relevant diamond coatings of varying roughness using spherical ruby probes that are large enough (0.5-mm-diameter) to sample all length scales of topography. For each material, more than 2000 measurements of pull-off force were performed in order to investigate the magnitude and statistical distribution of adhesion. Using sphere-contact models, the roughness-dependent effective values of work of adhesion were measured, ranging from 0.08 to 7.15 mJ/m2 across the four surfaces. The data was more accurately fit using numerical analysis, where an interaction potential was integrated over the AFM-measured topography of all contacting surfaces. Results These calculations revealed that consideration of nanometer-scale plasticity in the materials was crucial for a good quantitative fit of the measurements, and the presence of such plasticity was confirmed with AFM measurements of the probe after testing. This analysis enabled the extraction of geometry-independent material parameters; the intrinsic work of adhesion between ruby and diamond was determined to be 46.3 mJ/m2. The range of adhesion was 5.6 nm, which is longer than is typically assumed for atomic interactions, but is in agreement with other recent investigations. Finally, the numerical analysis was repeated for the same surfaces but this time with different length-scales of roughness included or filtered out. Conclusions The results demonstrate a critical band of length-scales—between 43 nm and 1.8 µm in lateral size—that has the strongest effect on the total adhesive force for these hard, rough contacts.

Investigation of the domain structure and hierarchy in potassium–sodium niobate lead-free piezoelectric single crystals

RSC Advances ◽  
2016 ◽  
Vol 6 (54) ◽  
pp. 49060-49067 ◽  
Author(s):  
Micka Bah ◽  
Natalya Alyabyeva ◽  
Richard Retoux ◽  
Fabien Giovannelli ◽  
Mustapha Zaghrioui ◽  
...  
Keyword(s):  
Single Crystals ◽  
Domain Structure ◽  
Lead Free ◽  
Nanometer Scale ◽  
Sodium Niobate ◽  
Potassium Sodium Niobate ◽  
Length Scales ◽  
Potassium Sodium ◽  
Domain Structures ◽  
Self Organized

We reported self-organized and hierarchized domain structures on various length scales ranging from micrometer to nanometer scale in K0.5Na0.5NbO3 crystals.

Combining Imaging Modalities in the Modeling of Multiparameter Devices

2013 ◽  
Vol 7 (4) ◽  
Author(s):  
Jens Vinge Nygaard
Keyword(s):  
Numerical Analysis ◽  
Fluid Mechanics ◽  
Modeling And Simulation ◽  
Medical Devices ◽  
Numerical Models ◽  
Imaging Modalities ◽  
Length Scales ◽  
Geometrical Information ◽  
Multiphysics Problems

Modeling and simulation of medical devices are typically established to identify parameter dependencies within the system of interest. Most devices are multiphysics problems considering solid and fluid mechanics, and electromagnetic mechanisms bridging time and length scales. Typically, the geometries of interest are described by complex morphologies of biological components. These factors all contribute to significant complexity of the developed numerical models. Access to imaging modalities capable of providing the geometrical information of relevance is central in the establishment and verification of numerical analysis. Here, data from image-based models obtained with MRI and μCT to risk access patients prone to realizing stroke, and to evaluate drug eluding scaffolds is presented.

Monte Carlo Modeling of Phonon Transport Using Scattering Phase Functions

2008 ◽  
Author(s):  
Neil Zuckerman ◽  
Jennifer R. Lukes
Keyword(s):  
Thermal Conductivity ◽  
Monte Carlo ◽  
Numerical Methods ◽  
Ballistic Transport ◽  
Simulation Method ◽  
Phonon Transport ◽  
Nanometer Scale ◽  
Boltzmann Transport ◽  
Length Scales ◽  
Scale Structures

The calculation of heat transport in nonmetallic materials at small length scales is important in the design of thermoelectric and electronic materials. New designs with quantum dot superlattices (QDS) and other nanometer-scale structures can change the thermal conductivity in ways that are difficult to model and predict. The Boltzmann Transport Equation can describe the propagation of energy via mechanical vibrations in an analytical fashion but remains difficult to solve for the problems of interest. Numerical methods for simulation of propagation and scattering of high frequency vibrational quanta (phonons) in nanometer-scale structures have been developed but are either impractical at micron length scales, or cannot truly capture the details of interactions with nanometer-scale inclusions. Monte Carlo (MC) models of phonon transport have been developed and demonstrated based on similar numerical methods used for description of electron transport [1-4]. This simulation method allows computation of thermal conductivity in materials with length scales LX in the range of 10 nm to 10 μm. At low temperatures the model approaches a ballistic transport simulation and may function for even larger length scales.

Nanometer-Scale Shock-Front Structure in Metals

1988 ◽  
Vol 141 ◽  
Author(s):  
Paul A. Taylor ◽  
Brian W. Dodson
Keyword(s):  
Shock Wave ◽  
Molecular Dynamics ◽  
Shock Front ◽  
Nanometer Scale ◽  
Many Body ◽  
Front Structure ◽  
Atomic Interactions ◽  
The Many ◽  
First Time ◽  
Structural Instabilities

AbstractMolecular dynamics shock wave simulations have been performed, which for the first time include a realistic many-body description of the atomic interactions. The structural instabilities observed in the shock-front structure are dramatically influenced by the many-body effects of these atomic interactions.

scholarly journals Development of soft-sphere contact models for thermal heat conduction in granular flows

AIChE Journal ◽  
2016 ◽  
Vol 62 (12) ◽  
pp. 4526-4535 ◽  
Author(s):  
A. B. Morris ◽  
S. Pannala ◽  
Z. Ma ◽  
C. M. Hrenya
Keyword(s):  
Heat Conduction ◽  
Granular Flows ◽  
Soft Sphere ◽  
Contact Models ◽  
Sphere Contact

GROWTH AND CHARACTERIZATION OF ATOMIC AND NANOMETER SCALE WIRES ON THE SILICON SURFACE

2000 ◽  
Vol 07 (05n06) ◽  
pp. 555-560 ◽  
Author(s):  
J. NOGAMI
Keyword(s):  
Transport Properties ◽  
Electronic Properties ◽  
Self Assembly ◽  
Silicon Surface ◽  
Growth Behavior ◽  
The Self ◽  
Nanometer Scale ◽  
Semiconductor Surfaces ◽  
Length Scales

Growth of metals on semiconductor surfaces can result in the self-assembly of a variety of 1D or 2D structures whose lateral dimensions range from one atom to tens of atoms. Over this range in length scales, STM gives information about the structure, the growth behavior and the electronic properties of these small structures. STM and STS data on several different systems are presented. In addition, ongoing and future efforts to measure the transport properties of these small structures are described.

Effect of Target Power and Bias on Adhesive Force of BCN Films

2011 ◽  
Vol 287-290 ◽  
pp. 2148-2151 ◽  
Author(s):  
Kai Bi ◽  
Jun Liu ◽  
Qi Xun Dai
Keyword(s):  
Scratch Test ◽  
Adhesive Force ◽  
Hard Material ◽  
Test Results ◽  
X Ray Diffraction ◽  
Adhesion Properties ◽  
Target Power ◽  
New Type ◽  
Boron Carbon Nitride ◽  
Boron Carbon

Boron carbon nitride (BCN) is a new type of super-hard material with excellent properties, and is very suitable for use as a wear-resistant protective coating and solid lubricant. In this report, we prepared BCN films on YG8 cemented carbide substrate by magnetron sputtering. The structure and composition of the films were analyzed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The adhesiveness of the films was studied by scratch test. Results from these analyses show that BCN films deposited on the YG8 substrate has good adhesion properties. We also demonstrated that target power and substrate bias have a great impact on the adhesiveness of the films, and reasonable process parameters can improve the adhesiveness of the films.

scholarly journals Evidence for intermolecular forces involved in ladybird beetle tarsal setae adhesion

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Naoe Hosoda ◽  
Mari Nakamoto ◽  
Tadatomo Suga ◽  
Stanislav N. Gorb
Keyword(s):  
Free Energy ◽  
Surface Free Energy ◽  
Adhesion Force ◽  
Intermolecular Forces ◽  
Adhesive Force ◽  
Work Of Adhesion ◽  
Polar Component ◽  
Adhesion Mechanism ◽  
Ladybird Beetle ◽  
Ladybird Beetles

AbstractWhy can beetles such as the ladybird beetle Coccinella septempunctata walk vertically or upside-down on a smooth glass plane? Intermolecular and/or capillary forces mediated by a secretion fluid on the hairy footpads have commonly been considered the predominant adhesion mechanism. However, the main contribution of physical phenomena to the resulting overall adhesive force has yet to be experimentally proved, because it is difficult to quantitatively analyse the pad secretion which directly affects the adhesion mechanism. We observed beetle secretion fluid by using inverted optical microscopy and cryo-scanning electron microscopy, which showed the fluid secretion layer and revealed that the contact fluid layer between the footpad and substrate was less than 10–20 nm thick, thus indicating the possibility of contribution of intermolecular forces. If intermolecular force is the main physical phenomenon of adhesion, the force will be proportional to the work of adhesion, which can be described by the sum of the square roots of dispersive and polar parts of surface free energy. We measured adhesion forces of ladybird beetle footpads to flat, smooth substrates with known surface free energies. The adhesive force was proportional to the square-root of the dispersive component of the substrate surface free energy and was not affected by the polar component. Therefore, intermolecular forces are the main adhesive component of the overall adhesion force of the ladybird beetle. The footpads adhere more strongly to surfaces with higher dispersive components, such as wax-covered plant leaves found in the natural habitat of ladybird beetles. Based on the present findings, we assume ladybird beetles have developed this improved performance as an adaptation to the variety of plant species in its habitat.

Influence of Alloying Additives on The Adhesive Properties of Steels: Atomic Level Simulation

2018 ◽  
Vol 14 (3) ◽  
pp. 5734-5740
Author(s):  
Ahmed Tamer AlMotasem
Keyword(s):  
Adhesion Force ◽  
Adhesive Force ◽  
Vanadium Content ◽  
Dynamics Simulation ◽  
Work Of Adhesion ◽  
Adhesive Properties ◽  
Alloying Additives ◽  
Iron Iron ◽  
Titanium Surfaces ◽  
Higher Temperature

In the present work we report atomistic molecular dynamics simulation results on adhesion force between self-mated iron/iron, iron/vanadium, iron-cementite and iron/titanium surfaces has been determined and we found that iron/cementite surface exhibits lower adhesive force than that of iron/iron surface. The results showed that adhesion, quantified by the work of adhesion, decreased as the vanadium content increased and highest reduction was obtained for 10 at.% vanadium and  7.5 at.% for titanium. Furthermore, the variation of adhesion force with temperature was studied in the temperature range between 300-700 K and we found that the adhesive force generally is lowered at higher temperature.

Establishment and verification of a contact model of flowing fresh concrete

2018 ◽  
Vol 35 (7) ◽  
pp. 2589-2611
Author(s):  
Yuan Zhao ◽  
Zhennan Han ◽  
Yali Ma ◽  
Qianqian Zhang
Keyword(s):  
Experimental Data ◽  
Numerical Analysis ◽  
Fresh Concrete ◽  
Dynamic Performance ◽  
Discrete Element ◽  
Contact Model ◽  
Two Phase ◽  
Content Type ◽  
Concrete Pumping ◽  
Contact Models

Purpose The purpose of this paper is to establish a new dynamic coupled discrete-element contact model used for investigating fresh concrete with different grades and different motion states, and demonstrate its correctness and reliability according to the rheological property results of flow fresh concrete in different working states through simulating the slump process and mixing process. Design/methodology/approach To accurately express the motion and force of flowing fresh concrete in different working states from numerical analysis, a dynamic coupled discrete-element contact model is proposed for fresh concrete of varying strength. The fluid-like fresh concrete is modelled as a two-phase fluid consisting of mortar and aggregate. Depending on the contact forms of the aggregate and mortar, the model is of one of the five types, namely, Hertz–Mindlin, pendular LB contact, funicular mucous contact, capillary LB contact or slurry lift/drag contact. Findings To verify the accuracy of this contact model, concrete slump and cross-vane rheometer tests are simulated using the traditional LB model and dynamic coupled contact model, for five concrete strengths. Finally, by comparing the simulation results from the two different contact models with experimental data, it is found that those from the proposed contact model are closer to the experimental data. Practical implications This contact model could be used to address issues such as (a) the mixing, transportation and pumping of fresh concrete, (b) deeper research and discussion on the influence of fresh concrete on the dynamic performance of agitated-transport vehicles, (c) the behaviour of fresh concrete in mixing tanks and (d) the abrasion of concrete pumping pipes. Originality/value To accurately express the motion and force of flowing fresh concrete in different working states from numerical analysis, a dynamic coupled discrete-element contact model is proposed for fresh concrete of varying strength.

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