Surface Topography Evolution of Engineered Surfaces during Sliding Wear

2021 ◽  
Vol 901 ◽  
pp. 199-207
Author(s):  
Deepak K. Prajaapti
Keyword(s):  
Surface Topography ◽  
Contact Pressure ◽  
Sliding Wear ◽  
Wear Model ◽  
Maximum Increase ◽  
Real Area Of Contact ◽  
Engineered Surfaces ◽  
Milled Surface ◽  
Very High ◽  
Insight Into

Due to experimental limitations, sometimes it is challenging to tackle the thorough change in asperity characteristics (contact pressure, real area of contact, asperity radius), which demands a more suitable analytical model for prediction of such characteristics. This work demonstrates an approach for modeling sliding wear that provides an insight into the evolution of surface topography with operational cycles. The wear model is applied on various engineered surfaces to study the change in surface topography with wear cycles. It is concluded that different engineered surfaces nearly with same roughness demonstrate totally different behavior during sliding wear. It is observed that milled surface in comparison to turned, honed and grinding surfaces experiences minimum contact pressure due to very high correlation length. Within the range of wear cycles, maximum increase in the asperity radius is observed for milled surface.

Simulation of Sliding Wear in Mixed Lubrication

2007 ◽  
Vol 129 (3) ◽  
pp. 544-552 ◽  
Author(s):  
Dong Zhu ◽  
Ashlie Martini ◽  
Wenzhong Wang ◽  
Yuanzhong Hu ◽  
Bohdan Lisowsky ◽  
...  
Keyword(s):  
Surface Topography ◽  
Contact Pressure ◽  
Sliding Wear ◽  
Numerical Models ◽  
Elastohydrodynamic Lubrication ◽  
Numerical Approach ◽  
Engineering Practice ◽  
Wear Process ◽  
Local Contact ◽  
Wear Law

Sliding wear is a significant surface failure mode in many mechanical components. The magnitude of changes in surface topography due to wear may be comparable to or larger than the original surface roughness and elastic deformation. However, wear has rarely been incorporated into the numerical models used as predictive tools in engineering practice. This paper presents a numerical approach to simulate the wear process based on the deterministic mixed elastohydrodynamic lubrication (EHL) model developed and modified by Zhu and Hu (2001, Tribol. Trans., 44, pp. 383–398). It is assumed that wear takes place at locations where the surfaces are in direct contact, and the wear rate at those local contact spots is proportional to the relative sliding speed, the local contact pressure, and inversely proportional to the hardness of the surface. At each simulation cycle, the distributions of lubricant film thickness and contact pressure are calculated by using the mixed EHL model. The material removal at each contact location is evaluated and the surface topography modified correspondingly. The renewed surface topography is then used for the next cycle. The model is formulated such that any mathematically expressed wear law can be implemented, and therefore, the simulation can be applied to a wide variety of engineering applications.

Insight into the formation of a continuous sheath structure for the PS phase in tri-continuous PVDF/PS/HDPE blends

RSC Advances ◽  
2016 ◽  
Vol 6 (1) ◽  
pp. 439-447 ◽  
Author(s):  
Rui Dou ◽  
Shuanglin Li ◽  
Yan Shao ◽  
Bo Yin ◽  
Mingbo Yang
Keyword(s):  
Ternary Blends ◽  
Continuous Structure ◽  
High Level ◽  
Very High ◽  
Insight Into ◽  
Sheath Structure

A hierarchical tri-continuous structure is formed and controlled in PVDF/PS/HDPE ternary blends. A very high level of PS continuity, about 80%, is achieved only with a PS volume composition as low as 11 vol%.

Development of a Simulation Model to Investigate Tool Wear in Ti-6Al-4V Alloy Machining

2011 ◽  
Vol 223 ◽  
pp. 535-544 ◽  
Author(s):  
Volker Schulze ◽  
Frederik Zanger
Keyword(s):  
Tool Wear ◽  
High Strength ◽  
State Variables ◽  
Wear Model ◽  
Fem Model ◽  
Load Variations ◽  
Wear Rates ◽  
Simulation Results ◽  
Mechanical Machining ◽  
Very High

Titanium alloys like Ti‑6Al‑4V have a low density, a very high strength and are highly resistant to corrosion. However, the positive qualities in combination with the low heat conductivity have disadvantageous effects on mechanical machining and on cutting in particular. Ti‑6Al‑4V forms segmented chips for the whole range of cutting velocities which influences tool wear. Thus, optimization of the manufacturing process is difficult. To obtain this goal the chip segmentation process and the tool wear are studied numerically in this article. Therefore, a FEM model was developed which calculates the wear rates depending on state variables from the cutting simulation, using an empirical tool wear model. The segmentation leads to mechanical and thermal load variations, which are taken into consideration during the tool wear simulations. In order to evaluate the simulation results, they are compared with experimentally obtained results for different process parameters.

The role of surface topography and normal load in the initiation of ratchetting-peak friction, seizure, scuffing, and elastic shakedown

2021 ◽  
pp. 1-12
Author(s):  
Vimal Edachery ◽  
V. Swamybabu ◽  
Gurupatham Anand ◽  
Paramasamy Manikandan ◽  
Satish V. Kailas
Keyword(s):  
Steady State ◽  
Surface Topography ◽  
Sliding Wear ◽  
Friction And Wear ◽  
Critical Parameter ◽  
Normal Load ◽  
Sliding Direction ◽  
Elastic Shakedown ◽  
Lubrication Conditions

Abstract Surface topography is a critical parameter that can influence friction and wear in engineering applications. In this work, the influence of surface topography directionality on seizure and scuffing initiation during tribological interactions is explored. For this, unidirectional sliding wear experiments were carried out in immersed lubrication conditions for various normal loads. The tribological interactions were studied using EN31-60 HRC flats and SAE52100-60HRC pins in a sphere on flat configuration. The results show that, in some cases, the sliding interactions in the initial cycles lead to a high friction coefficient of up to ∼0.68 in lubricated conditions, which was termed as ‘peak friction’, and this was accompanied by scuffing. The existence of peak friction was found to be dependent on surface topography directionality, especially when the directionality in topography was parallel to the sliding direction. Continuous ratchetting was found to be the cause of peak friction which was accompanied by seizure and scuffing. When the topography directionality was perpendicular or independent of sliding direction, elastic shakedown occurred at earlier cycles and prevented peak friction initiation, scuffing and also facilitated for higher steady-state friction values.

scholarly journals Dental calculus: Nano-characterization

2012 ◽  
Vol 59 (3) ◽  
pp. 154-159
Author(s):  
Djurica Grga ◽  
Marina Marjanovic ◽  
Igor Hut ◽  
Bojan Dzeletovic ◽  
Djuro Koruga
Keyword(s):  
Magnetic Field Gradient ◽  
Dental Calculus ◽  
Oral Diseases ◽  
Force Microscopy ◽  
Atomic Force ◽  
Light Matter Interaction ◽  
The Magnetic Field ◽  
Very High ◽  
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Emerging technologies and new nanoscale information have potential to transform dental practice by improving all aspects of diagnostics and therapy. Nanocharacterization allows understanding of oral diseases at molecular and cellular levels which eventually can increase the success of prevention and treatment. Opto-magnetic spectroscopy (OMS) is a promising new technique based on light-matter interaction which allows insight into the quantum state of matter. Since biomolecules and tissues are usually paramagnetic or diamagnetic materials it is possible to determine the dynamics of para-and diamagnetism at different teeth structures using that method. The topography of the surface of a sample can be obtained with a very high resolution using atomic force microscopy (AFM), which allows observation of minimal changes up to 10 nm, while magnetic force microscopy (MFM) is used to record the magnetic field gradient and its distribution over the surface of a sample. The aim of this study was to determine the possibility of AFM and MFM for the characterization of dental calculus, and a potential application of OMS for the detection of subgingival dental calculus.

The carrot and the stick

2008 ◽  
Vol 9 (2) ◽  
pp. 179-203 ◽  
Author(s):  
Christoph Bartneck ◽  
Juliane Reichenbach ◽  
Julie Carpenter
Keyword(s):  
Error Rate ◽  
Computer Screen ◽  
Human Partner ◽  
Collaborative Game ◽  
Real Robot ◽  
Very High ◽  
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This paper presents two studies that investigate how people praise and punish robots in a collaborative game scenario. In a first study, subjects played a game together with humans, computers, and anthropomorphic and zoomorphic robots. The different partners and the game itself were presented on a computer screen. Results showed that praise and punishment were used the same way for computer and human partners. Yet robots, which are essentially computers with a different embodiment, were treated differently. Very machine-like robots were treated just like the computer and the human; robots very high on anthropomorphism / zoomorphism were praised more and punished less. However, barely any of the participants believed that they actually played together with a robot. After this first study, we refined the method and also tested if the presence of a real robot, in comparison to a screen representation, would influence the measurements. The robot, in the form of an AIBO, would either be present in the room or only be represented on the participants’ computer screen (presence). Furthermore, the robot would either make 20% errors or 40% errors (error rate) in the collaborative game. We automatically measured the praising and punishing behavior of the participants towards the robot and also asked the participant to estimate their own behavior. Results show that even the presence of the robot in the room did not convince all participants that they played together with the robot. To gain full insight into this human–robot relationship it might be necessary to directly interact with the robot. The participants unconsciously praised AIBO more than the human partner, but punished it just as much. Robots that adapt to the users’ behavior should therefore pay extra attention to the users’ praises, compared to their punishments.

Abstract WP82: Transcranial Doppler Detection of Microembolic Signals During the Advancement and Deployment of Pipeline Embolization Devices in Unruptured Intracranial Aneurysm Repair

Stroke ◽  
2017 ◽  
Vol 48 (suppl_1) ◽  
Author(s):  
Andres Hughes ◽  
Mark J Dannenbaum ◽  
Peng R Chen ◽  
Arthur L Day ◽  
Huimahn A Choi ◽  
...  
Keyword(s):  
Transcranial Doppler ◽  
Neurological Complication ◽  
Initial Study ◽  
Relative Safety ◽  
High Incidence ◽  
Device Placement ◽  
The Mean ◽  
Aneurysm Repair ◽  
Very High ◽  
Insight Into

Introduction: Pipeline embolization devices (PED) have become an essential tool in the endovascular treatment of complex intracranial aneurysms. A high-density stent like device, the PED functions to redirect blood flow and facilitate the growth and remodeling of the artery. Postoperative ischemic stroke proves to be the most common neurological complication associated with treatment, ranging from about 3-6% with most occurring within 30 days. Transcranial Doppler (TCD) monitoring has been used in the past to evaluate similar procedures by measuring the occurrence of microembolic signals (MES). Due to the delivery and manipulation of the PED and its thrombotic nature, microembolic events have been postulated to form during device placement and contribute to thromboembolism. Our initial study is the first to detect and measure MES during a PED procedure. Methods: Patients undergoing endovascular PED treatment were simultaneously monitored with TCD. MES were detected, separated from artifacts, and counted for each step. Results: Embolic signals were detected in all patients and were highest during deployment. With 3 PED deployments in the paraophthalmic ICA of 2 patients, the mean MES during PED deployment was 515 +/- 46. Average emboli per second during deployment was 1.62 +/- 0.59 verses 0.30 +/- 0.12 emboli per second observed prior to microcatheter insertion and manipulation. Conclusion: A very high incidence of MES was observed during the procedure and PED deployment. The little success thus far in elucidating a possible mechanism to account for PED’s associated complications warrants more investigation. Determining the occurrence of MES might reveal insight into the relative safety of each step and on the formation of distal thromboembolisms.

scholarly journals Future Facilities for Gamma-Ray Pulsar Studies

2004 ◽  
Vol 218 ◽  
pp. 399-406
Author(s):  
D. J. Thompson
Keyword(s):  
Particle Acceleration ◽  
Neutron Stars ◽  
Gamma Ray ◽  
Large Area ◽  
Space Telescope ◽  
High Energies ◽  
Interaction Processes ◽  
Very High ◽  
Insight Into

Pulsars seen at gamma-ray energies offer insight into particle acceleration to very high energies, along with information about the geometry and interaction processes in the magnetospheres of these rotating neutron stars. During the next decade, a number of new gamma-ray facilities will become available for pulsar studies. This brief review describes the motivation for gamma-ray pulsar studies, the opportunities for such studies, and some specific discussion of the capabilities of the Gamma-ray Large Area Space Telescope (GLAST) Large Area Telescope (LAT) for pulsar measurements.

scholarly journals Effects of Feed per Tooth and Radial Depth of Cut on Amplitude Parameters and Power Spectral Density of a Machined Surface

Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1323
Author(s):  
Qing Zhang ◽  
Song Zhang
Keyword(s):  
Spectral Density ◽  
Surface Topography ◽  
Power Spectral Density ◽  
End Milling ◽  
Spectral Energy ◽  
Depth Of Cut ◽  
Power Spectral ◽  
Radial Depth ◽  
Milled Surface ◽  
Step Over

Surface topography and roughness significantly affect the functional properties of engineering parts. In this study, a mathematical model simulating the surface topography in end milling is presented and verified by milling experiments. The three dimensional (3D) surface amplitude parameters (arithmetic average deviation Sba and root mean square deviation Sq) of the milled surface were calculated by using the model and the effects of the product (p) and ratio (r) of radial depth of cut ae and feed per tooth fz on amplitude parameters were researched. To evaluate the lateral characteristics of the milled surface, one dimensional (1D) power spectral densities (PSD) along both feed and step-over direction were calculated and investigated. It was found that fz affects 1D PSD along both directions, whereas ae affects 1D PSD along the step-over direction. An angular spectrum, derived from the area power spectral density (APSD), was employed to research the spatial distribution of spectral energy on the milled surface. Furthermore, the influences of p and r on the PSD properties were researched. It was found that r is the significant factor that influences the direction of surface energy spectrum distribution.

In-Situ Observations of the Effect of Electron Irradiation on the Defect Microstructure of Alumina

1997 ◽  
Vol 3 (S2) ◽  
pp. 601-602
Author(s):  
S.-J. Chen ◽  
U. Dahmen ◽  
D.G. Howitt
Keyword(s):  
High Temperature ◽  
Electron Irradiation ◽  
Shear Bands ◽  
Valuable Insight ◽  
High Velocity Impact ◽  
Dislocation Densities ◽  
In Situ Observations ◽  
Very High ◽  
Insight Into

The interaction of radiation produced point defects with a dislocation microstructure at high temperature is of considerable interest and careful high voltage microscopy experiments can provide valuable insight into the mechanisms. Veyssière and Westmacott carried out in-situ experiments monitoring the partial dislocation climbs in Ni3Al induced by thermal vacancies as well as by Frenkel pairs produced during irradiation.1 We report here the results of some preliminary experiments we performed on alumina (A12O3) single crystals with high dislocation densities to study the modification of the microstructure by electron irradiation at high temperature.The dislocation microstructures were produced by shock wave deformation using a high-velocity impact technique. The technique is capable of producing a very high density of defects consisting primarily of basal twins, and slips on the basal, pyramidal and rhombohedral planes in alumina. The dislocations are all of glide type, mostly forming shear bands. A typical microstructure prior to irradiation is shown in figure la.

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