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Tribology - Science topic

Everything on tribology, tribocorrosion and the technology of interacting surfaces moving in relation to each other.
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I have written a numerical model for calculating the elastic deformation of two elastic bodies in 3D static contact. The code takes the applied laod, Young's Modulus, Poisson ratio, and surface profile of each body. Calculates influence coefficients based on the equation provided by Love [1]. The problem is solved by conjugate gradient descent and elastic deformation is calculated by Discrete Fourier Transform- Discrete Convolution method.
I tested the model on ball-on-flat and ball-on-ball geometries with the same material properties of each body. I am facing the problem that the elastic deformation contour is diagonal instead of concentric in these cases. The pressure distribution normalized at Hertz Contact pressure and contact width is correct, but the deformation is not. I have double-checked by Kernal/influence coefficient matrix but can not seem to understand this behavior. I have attached the 3D plots of the example (ball-on-ball), the 3D plot of the influence coefficient at 1 point, and the contour of calculated deformation.
Any help, guidance to solve, or help in understanding the problem would be greatly appreciated.
Thanks.
A.E.H. Love. Stress produced in a semi-in nite solid by pressure on part of the boundary. Philosophical Transactions of the Royal Society of London, 377:54{59, 1929.
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Influence coefficients are used in numerical simulations to determine how much influence a given node or point in the domain has on other nodes or points. These coefficients are often calculated based on the nodes' relative positions and the system's physical laws, such as the heat equation or Navier-Stokes equations for fluid dynamics.
As you've noticed, one common issue with influence coefficients is handling the boundaries or corners of the domain. In many cases, the influence coefficients near the boundaries will differ from those in the interior because the boundary conditions affect the system's behaviour.
One way to handle this is by using different formulas or methods to calculate the influence coefficients near the boundaries and interior. For example, you might calculate the first row of the influence coefficient matrix using x1 and y1 for the corners, and then use a different method for the interior points.
Another potential issue is that some numerical methods assume periodic boundary conditions, meaning that the system wraps around from one domain edge to the other. As you've described, this can result in 'continued influence' on the other edge of the domain. If your system doesn't have periodic boundary conditions, you might need to use a different method that properly handles the actual boundary conditions of your system.
It's hard to give more detailed advice without knowing the specifics of your system and the method you're using. However, I hope this gives you a starting point for understanding and resolving your issues.
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I am working on Numerical modelling to simulate tribological interactions while marble cutting. If anyone familiar please guide me little bit on this.
Thanks and Regards,
Bhargav Prajwal
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Hi guys,
Can anyone help me to understand, how shall i simulate the isotropic confining pressure in PFC3D using the wall servo command for triaxial testing in soil?
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Dear Scholars/Researchers,
Greetings of the day!
It gives us immense pleasure to announce that we are in the process of editing the book entitled “Additive Manufacturing of Bio-Implants - Design and Synthesis” for Springer.
Contributing book chapters are solicited in the following areas: • Additive manufacturing of biomaterials (such as Metallic, non-metallic, polymers, etc.) for various applications; • Development of Biomimetic Materials; • Medical Implants and Biomedical Device Design; • Biomechanical Characterization of additive manufactured Hard and Soft human Tissues; • Bioprinting and Nano-Biomaterials. • Corrosion performance of additive manufactured biomaterials • Biological Characteristics of additively manufactured biomaterials • Tribological characteristics of Additive manufactured biomaterials
•  Quality Assurance of additively manufactured bioimplants
I would like to invite you to contribute a Chapter to this book title. The 'Tentative Title' and 'Abstract' for the research contribution are invited on and before 20th April 2023. I look forward to hearing from you.
Book Title: “Additive Manufacturing of Bio-Implants - Design and Synthesis” Editors:
1. Dr. Amit Mahajan, Khalsa College of Engineering & Technology, Department of Mechanical Engineering, Amritsar, India 2. Dr. Sandeep Devgan, Khalsa College of Engineering & Technology Department of Mechanical Engineering, Amritsar, India 3. Dr. Redouane Zitoune, Institute Clement Ader, Toulouse University, Toulouse, France
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@ U. Ashok kumar
Dear sir,
I have sent an email on your respective email. But it is undelivered.
Kindly submit your abstract and title before 20thApril at amitmahajan291@gmail.com.
Thanks
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Machining of steel metal will result in surface integrity which is related to tribological effects. Does the content and final phase occurring in iron-carbon alloys on steel surfaces have an impact on tribology?
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The influence of the carbon content on the tribology of its alloys with iron is very strong. The carbon content changes the hardness of steels, creating both very hard carbide inclusions and very soft graphite inclusions in cast irons and steels, and all this is reflected in both the coefficient of friction and wear resistance. The influence of the carbon content is also manifested in the ability of steel to harden, which also has a dramatic effect on tribology.
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What information do we get from 2D optical graph of wear track related to tribology?
Please check the attached file for 2D optical graph.
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No, the pin of the indenter was not broken.
A single indenter was used.
What would be the answer if hard particles were embedded in the matrix?
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Hello,
I am doing some tribological tests with a reciprocal sliding tribological test.
To calculate the wear rate, the wear volume is needed with high accuracy. Do you have any accurate and easy method(s) to evaluate that wear volume? I have already tried some imaging with 3D digital microscopy but the initial roughness of the substrate makes the measurement difficult.
Thank you in advance,
Alexandre
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It depends on which kind of tribological test you did (pin on disk, ball on ring, ...), depends on the shape of the pin/ball after the test (if damaged or not) and it depends on the substrate-materials you used for your experiments. In all cases you can use the classical technique by calculating the tribo area by optical microscope, or using the Optical 3D Profilometer, or using the mecanichal Profilometer, etc ...
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Suppose i am performing ball on disc tribological tests under lubricated conditions containing nanoparticles. After the test i wash the sample with Acetone or Benzene, will the EDS analysis show the trace of nanoparticles???
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I suggest you to do not wash you sample after testing even if you use lubricant in order to no destroy the thin layer of tribofilm formed during the test.
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Hello fellow researchers
i am working on cermets tribology and using pin on disk methods with disk made of cermet sliding against a diamond pin.the tribometer data gives wear volume(mm3),wear rate(mm3/m) and cof with an interval of 0.328 seconds.the sliding istance is approximately 200m.thus we have a lage amount of plotted data.i have a few confusions which i want to clarify
1)total Wear volume is the total sum of all all data points?( i assume it is) or an average of all data points should be considered
2)Total wear rate?average or sum?( i assume sum is the right option)
3) cof?( i assume an average of all datapoints should be taken)
another question regarding wear coefficient k=wearvol(mm3)*hardness vickers(in mpa)/load(N)*total sliding distance(mm)
wear vol=i took sum of all data plots
hardness=avg hardness of test samples
load=40N(as aplied)
distance=Distance in mm
one measurement gave a wear cof of 1.5e-06 which is good for cemented carbides(i assume)
am i following the correct methodology here?
please find enclosed image of some readings for guidance.
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@mohamadou Diew Thank yo so much for the explanations. A manual calculation by adding all set points of mm3 and dividing by total distance covered.
I have 2 load 10 and 40 newton. Same sliding speed for alls amples. Should i quoute specific wear rate or just wear rate
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During dry sliding wear tests, the worn surfaces of magnesium alloys are oxidized at a specific load and sliding velocity. I want to know that in magnesium matrix composites, adding reinforcing particles (such as B4C) can prevent or postpone this oxide formation or not
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I would want to thank you again for your thorough response to my query.
Per your suggestion, we have performed an FT-IR analysis on generated wear debris for both Mg alloy and its composite with B4C particles. The detected tribochemical compounds were MgCO3, Mg(OH)2, and MgO. As anticipated, the CO32- bands in MgCO3 increased. Now, I would appreciate it if you could clarify why increasing CO32- bands in composites might lessen their oxidative wear probability.
Best regards
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Dear fellow contact mechanicians,
I just stumbled over a problem in analytic mechanics of plane Cattaneo problems in the presence of bulk stress.
It is said that the Ciavarella-Jäger principle for "small enough bulk stress" applies to this problem in the following form:
q(x) = \mu*(p(x; P, beta = 0) - p(x; P - Q/mu, beta)),
where q(x) is the tangential contact traction distribution, p(x) the pressure distribution, P the normal line load, Q the tangential line load, mu the friction coefficient and beta a "rotation angle" proportional to the bulk stress, which I will discuss in a minute.
The second term on the right side in above equation corresponds to a "fictious" normal contact problem of the same contacting bodies under the load (P - Q/mu) and with a relative rotation by beta.
The condition of "small enough bulk stress" is basically that the contact area for this "fictious" problem (which corresponds to the stick region in the actual Cattaneo problem), completely lies within the actual contact area. Moreover, a non-zero value of beta will increase the contact length on one side and decrease it on the other side. So, e.g., for Q = 0 the condition of "moderate bulk stress" is actually that beta = 0, i.e., there is no bulk stress.
Now, we know that tangential contact problems have a loading history. Even the Cattaneo problem has a history: first the normal load is applied, and then an increasing tangential load. However, when beginning to apply the tangential load, Q equals zero, so any (constant) bulk stress will violate the "moderate bulk stress condition".
Or to put it more generally: For any non-zero constant bulk stress, the "moderate bulk stress condition" is violated at the beginning of tangential loading.
Does that change anything about the final contact configuration at the end of the Cattaneo loading?
Or am I missing something?
Thank you very much for your help!
Kind regards,
Emanuel
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Well thank you, but that paper doesn't answer my question, as the authors just put moderate bulk stress ("We restrict attention to cases in which the direction of slip is the same at either end of the contact") and calculate from there. And for now, I am only interested in the Cattaneo loading, not the cyclic case.
My question is, what happens, if the contact switches from non-moderate to moderate bulk stress? Consider Q = 0. Then, the "moderate bulk stress condition" is that there is actually no bulk stress; you can look it up in Barber's book, but it is logical, as any bulk stress will lead to opposite slip directions at the two contact ends.
Now, does that change anything about the contact solution if Q gets large enough during the Cattaneo loading for the bulk stress to be actually moderate?
I guess, the point is, that slip will always just propagate inside from the contact edges, unless loading is reversed, even if the bulk stress is not moderate, and so, no point will ever switch from slip to stick (although at one edge the slip direction is continously reversed), but I am not able to prove that rigorously.
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I found the following statement in a book on page 581:
"If, in a particular timestep a converged result is obtained with a negative calculated film thickness, then the most negative film thickness is set to zero."
Dowson, D., Priest, M., Dalmaz, G., & Lubrecht, A. A. (Eds.). (2003). Tribological Research and Design for Engineering Systems: Proceedings of the 29th Leeds-Lyon Symposium. Elsevier.
What exactly happens when the film thickness is zero? Can anyone explain this to me? I will greatly appreciate it.
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The significance of the film thickness less than 0 in this case is that it indicates that the contact is operating in the mixed EHL regime.
In the reference, the authors are discussing the solution for the lubricant load carrying capacity in an EHL contact simulation. The negative film thickness is occurring as the fluid film pressures alone are not sufficient to support the contact loads (in the preceding paragraph, the authors are discussing mixed EHL, with a load carrying capacity provided by the fluid film and direct asperity interactions).
If the fluid film thickness calculation at a node is less than 0, the authors suggest that the lubricant load carry capacity is neglected and the film thickness is set to 0, but the elastic deformation of the solid is retained for the given node. The elastic deformation of the solid at the node gives the solid-to-solid load carrying capacity to balance the loads applied to the contact in addition to the fluid film pressures at other nodes.
Work from Patir and Cheng and others has shown that the lubricant film load carrying capacity can be significant in the mixed regime of lubrication, but here they seem to be neglected for simplification.
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I'm currently working on ball-on-disk tribological test using different oils.
Is there a direct relation between the coefficient of friction and the lubrication regime of the coupled surfaces?
Is the resulting coefficint of friction related to the materials properties or the lubricant properties? Or both of them?
Thank you to all that would help me.
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Your question spans quite a big field, but I will try to answer succinctly.
There is no simple formula relationship between the coefficient of friction and the lubrication regime. You could look at the Stribeck curve and see the trend for coefficient of friction as the contact moves through the regimes, but this is more indicative than conclusive. To calculate it, you would probably need numerical simulations of the lubricant and surface load carrying capacities.
One approach would be to evaluate the ratio of the film thickness relative to the composite surface roughness. As a rough guide, where this ratio is large the regime is probably hydrodynamic, between 3 and 1.5 is probably mixed and less than 1.5 is probably boundary.
Please also bear in mind that that regime of lubrication will vary in the contact, as the surfaces are non-conformal.
The coefficient of friction that you measure can be dependent on a lot of factors. The lubricant viscosity, surface roughness and material hardness are probably the main factors, but the importance of these will change depending on what regime of lubrication you are in. Any additive within the lubricant, temperature, pressure, directionality of the surface roughness and slide-to-roll ratio may also be important factors.
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I have a device with confriguration Au/PVDF/Au. The connections are taken from the gold electrode using copper tape and over that I have soldered copper wire and finally they are connected to DSO. When I am tapping the device (on gold electrode), then gold electrode is behaving as one tribo layer and my hand is behaving like a ground. So, now the device is behaving like a single-electrode TENG. How can I separate out piezosignal out of this tribo signal? If anybody have any idea then please share.
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your body is not always ground, it could have a charge. As our body stores charge like a capacitor, there should be always a device that gives a tapping movement. it should not touch with any other materials or a material that is near to zero in triboelectric series like wood. That is the only solution to separate your signal from each other( if it is an independent tapping system without the involvement of the body). As our body skin has highly negative in triboelectric series. in the link, I have sent you our independent characterization device that has the ability to characterize samples without the involvement of the body.
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Dear researchers,
I am working on Mg composites fabricated by powder metallurgy. I have investigated the wear behavior of Mg-based composites with variation in temperature. I observed that wear rate increased with an increase in the wear temperature. Can anyone explain me in detail, why is it happening? What is the mechanism? I am looking for your responses.
Thank you so much.
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Thank you, sir. But I don't understand your language.
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Hello,
in my research group we would like to evaluate how the asperities of two rough planes deform when we press them together. We would like to use Abaqus, due to its advanced contact mechanics algorithms. It is not clear to us, though, how to model rough surfaces with certain statistics in Abaqus. Anyone knows any CAD software/code that could generate these models and be easily integrated with Abaqus?
Best regards,
Rafael.
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Hello Rafael,
Even I am working on the same problem, please let me know if you have found the solution. It would be a great help.
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Is there a relation between thermophysical properties (density, specific heat, viscosity, thermal conductivity) of fluids on tribological properties (friction coefficient, friction force)?
Please recommend some useful books or literature? need feed back
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Is it possible to change or form new chemical bonding using frictional heating during high sliding operations?
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Yes, it is possible. It depends against which material the friction occures. For instence, PI against SS creats a new chemical bond, etc.
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Submit only Research Objective, Problem Definition, Precise Note & References.
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A pretty large topic... hopefully will not became a troll.
Concerning current researches on the topic, more concerned with mechanical engineering, I will nevertheless make a bit of an advertising (sorry): you can have a look on the topics of the World Tribology Conference series (the next one, number 7, is planned in France) see https://www.wtc-2022.org and previous issues of this series (2017 in China, 2013 in Italy...)
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I want to buy MXenes any recommendations
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Dear Muhammad Chhattal, the following RG thread may brings some help. My Regards
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A few years ago I and my colleague Peter Wall wrote a short summary for Switch Function and and Complementarity Problem based formulations in a chapter which is available Open Access:
Andreas Almqvist and Peter Wall (October 26th 2016). Modelling Cavitation in (Elasto)Hydrodynamic Lubrication, Advances in Tribology, Pranav H. Darji, IntechOpen, DOI: 10.5772/63533. Available from: https://www.intechopen.com/books/advances-in-tribology/modelling-cavitation-in-elasto-hydrodynamic-lubrication
Since there are many more models for cavitation in lubrication flows it would be interested to hear from the community which ones you think are the most suitable ones and in which situations they should/could be applied.
Cheers, Andreas
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Great question Andreas Almqvist! One which I've debated a lot!
The complementarity problem is an excellent and effective way of solving the problem of hydrodynamic cavitation. Have you (or someone else) applied this method to highly-loaded contacts (GPa pressures) such a line and point contact geometries out of interest? Great to see answers already from authors adapting the approach for their specific problems here too.
I see the expected pressure magnitude being one of the main drivers behind the choice of model for this phenomena. I have reviewed (a little) the modelling approaches to hydrodynamic cavitation with the late, great Duncan Dowson as part of this publication: . In this article we developed a 'moving mesh' type of approach for modelling the onset of cavitation but did not consider film reformation. This method can be applied to low pressure (MPa) and high pressure (GPa) problems without any difference in the implementation.
For lower pressure environments (MPa) the Elrod-Adams algorithm is still widely used as the baseline method for simulating cavitation including papers published by my group this year: . There are several publications optimising and adapting this method with varying degrees of success in the literature, too many to list here.
More recently this method has been combined with the complementarity condition to formulate the problem as described by Andreas and others. This also links to recent improvements in the solution approach by Woloszynski and the use of the Fischer-Burmeister equation to formulate the complementarity problem (see very recent work by Ron van Ostayen at TU Delft).
The complementarity method is a more stable than Elrod-Adams approach numerically because of the lack of switching functions and more robust mathematical formulation, but this does require a LCP solver which may be prohibitive to some. This is likely why Elrod-Adams remains widely used given it can be used with a standard PDE solver and setup readily with commercial codes, albeit with switching functions included making the problem numerically stiff.
There is also the issue of the change of variable approach from pressure to a derived field used explicitly for the cavitation problem, which then conflates the solution to the lubrication flow in terms of one variable. Therefore several authors use a pressure-only type approach such as that which I explored with Andreas here: . This article uses the Söderfjäll model to create a blending function reducing the density and viscosity of the lubricant rapidly to almost zero in the presence of negative pressure. This simulates the effect of cavitation solely on the lubricant properties and produces the required pressure distribution efficiently with rupture and reformation included. A similar but different approach was used by Gao et al in this paper: . The approach is very useful for where there are many regions of cavitation occurring within the domain.
Note that all the applications discussed so far are conventionally developed for low pressure (MPa) environments, and that in the classic high pressure (GPa) contact problems cavitation is managed with less rigour of the pressure profile shape/value. This is because of the large separation in magnitude between the max pressure and the vapour pressure in such contacts, with the requirement only being to resolve the pressure and pressure gradient to zero at the location of the onset of cavitation (JFO conditions).
For GPa problems the JFO conditions are conventionally achieved either with the use of a free boundary problem (see the classic multilevel solutions of Venner) or with the penalty approach of Wu (see more recent solutions by Habchi). Neither of these approaches fully resolve the problem of cavitation and this has led to several two-phase type models being developed which require very fine grids to resolve the flow. Multi-phase CFD simulations have also been developed recently by Imperial College London to investigate cavitation in much more depth for highly-loaded contacts and resolving all the flow (see Hartinger et al. and Hajishafiee et al.). These two- or multi- phase models also allow variance in the film thickness direction and are therefore not necessarily based on the Reynolds equation, making them more complex descriptions of the flow that are harder to solve numerically.
So the question comes down to whether resolving the full pressure shape/value is of importance to the outcome required, which itself is connected to the magnitude of the expected pressure. There is also the question of what type of solver you have readily available, whether a change of variable doesn't conflate the problem formulation, and if you're interested in very fine detail about the flow features.
Personally I would be in favour of the ALE or complementarity approaches for any problem/geometry but this certainly needs more development, hence my question at the start. I also think a review paper on the topic is well overdue!
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Chicken eggshell (Es) waste is an industrial byproduct, and its disposal constitutes a severe environmental risk. Eggshell is a new engineering reinforcement retaining excellent properties such as low density, renewable, eco-friendly, and high thermal stability. The researcher aims to study the effects of eggshell particle addition on microstructures, mechanical and tribological properties of aluminum/eggshell green metal matrix composites (MMCs) but how?
what are the drawbacks of the addition of waste eggshells with (MMCs) composite?
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what are the drawbacks of the addition of waste eggshells with (MMCs) composite?
It is possible to tell the advantages and disadvantages of Al-EggShell only after knowing the properties of the waste Egg Shell.
However the Egg Shell consists of "calcium carbonate (CaCO3)" having Density 2.71g/cc, and Melting point 1,300 °C.
Thus it can be used with aluminum (bcoz its density is 2.65g/cc). But dont know whether the bonding between matrix and reinforcement take place or not.
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some metal surfaces, rubbed against each other squeaks in a shrilling high frequency. Why? What is the role of surface roughness, friction factor, geometric shape, stress distribution,solid and medium sound velocity, strength, resilience and microstructure to frequency spectrum of the sound? Are there any set of differential equations that describe this phenomena? How to construct a model concerning the phenomena?
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Re the explanation of
Michael Swanwick
, see the following reference.
[1] Jim Woodhouse; Chapter 9 - Vibrations: tuning forks and train wheels, squealing brakes and violins; in Christine Bondi (editor); Penguin Books; 1991; pp. 202-222.
Regards,
Tom Cuff
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Good Afternoon to all ..
I hope you are all safe and healthy.......
I have one doubt please let me know what are the tribological properties we should take for while making of composite gear.....
I hope for your immediate response....
Kind Regards
S.Sathishkumar
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This link may be useful
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Hello Every one,
I have the velocity of two particles before and after impact and all the forces components during the impact. I need a formula that gives the surface penetration speed during tribological surface finishing. For forces and velocity, they are obtained after a DEM simulation but I need the surface penetration speed to calculate the amount of material removal.
Thanks
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Dear Mohamed iben houria,
The penetration of particles into the surface depends on the type of penetrating particles - electrons or a mechanical element. Penetration also depends on the type of the investigated base (material), its condition (polished, rough, hardened, annealed, platinum deformed, casting, the way of fastening, etc.), which parameters have a strong influence. In addition, the environment has an impact (environment, or vacuum with controlled gas). Of course, the limits of penetration also depend on the scanning mode (frequency, retention time, power, etc.).
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Dear all I need to do errosion simulationfor tribology application in ansys fluent, as I am not familiar very well, I have some question.
We have a surface which being hited by water and sand, I defined K-epsilon modeling, disceret phase modeling,
Now my question is how can I get angel to the particles? I want to define for example, liquid and particle hit to the surface with the angel of 30 degree, and go out from outlet with this angel but I could not find any thing related.
Any body can help?
And there is any important point that I should consider?
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thank you so much
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If material is hard enough then what will the effect of its hardness on the tribological properties of that material?
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Dear Muhammad Chhattal,
Tribological properties depend on the hardness, roughness, types of layers and the difference between them. In addition, this method is often influenced by the test method. It is known that with increasing hardness, wear resistance increases at the expense of reducing impact resistance. Friction is highly dependent on roughness. At high roughness and high hardness, brittle fractures are observed. At low roughness and high hardness the appearance of cracked distributed subforms of scales and chipping is established.
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I am a third year Biomedical Student at the University of Wollongong and I am currently completing an assignment on manufacturing processes involved in biomedical technology. I have selected the Total Hip Arthroplasty (THA) and recently read a journal 'Tribological assessment of a flexible carbon-fibre-reinforced poly(ether—ether—ketone) acetabular cup articulating against an alumina femoral head.' (Scholes, Inman, Unsworth and Jones, 2008) and am very intrigued by the CFR-PEEK design of the acetabular cup. I would like to understand the steps involved in developing such a piece.
Have there been any developments in using this material?
Thanks for your time!
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Dear Alexandra,
the paper "Antifriction and Mechanical Properties of the Thermoplastic Matrix
of Polyetheretherketone-Based Composites" may be useful for you.
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I have data from an experiment conducted to measure kinematic co-efficient of friction. But to know how much slipping force is required to slip the interfaces (steel plates) , I need static co-efficient of friction (the threshold value). Is there any relation available to calculate this?
Thanks!
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Abhishek Parida as suggested in my previous reply, you can find some equations as a starting point in the paper:
"Physical analysis of the state- and rate-dependent friction law. II. Dynamic friction" T. Baumberger and P. Berthoud, 1999
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Hello,
I wanna get ultrasonic vibrations using a screen generator of 300 watts and 33kHz frequency.
Is it possible to use that generator to study ultrasonic vibrations effect on tribological behavior of materials?
Or I need other materials for this purpose? like piezo actuators, amplifiers, ultrasonic generators?
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You have to explain some more about your questions.
For example, you said your current generator has the frequency of 33 kHz and the power of 300 watts. So the question is if such a generator is acceptable for your study? If so, it is ok. If not, you will need to a generator with suitable power/amplitude/frequency. For heavy applications, your will need more power.
You would need a higher level power if you are studying those tribological applications wherein the applied forces or frictions are considerable. Lower ultrasonic energy is usually damped/disappeared in heavy applications.
Let me know should you have still question.
Massoud
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Hi! I´m having problems trying to identify any compounds in this Raman spectrum. I´ve used a 532 nm laser.
This is a spectrum obtained from a steel ball, rubbed against a Bi2S3 coating. I´ve checked in other papers for the characteristic bands of Bi2S3, Bi2O3, magnetite, hematite, etc but I´m a little bit thrown off, specially for the bands at 1465 and 1520 cm-1.
Any ideas?
Thank you!!
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Germa'n,
I am not particularly familiar with the samples you are working with as I specialize in biological materials. However, a quick search online may provide you with some guidelines on how to resolve the peak positions for your measurements and make tentative assignment.
Since you explained that you rubbed a steel ball against a Bi2S3 coatings, I think it might be prudent looking up Raman peak tables for
1) steel (assuming - Chrome alloy steel balls, these comprise about 90% of all balls manufactured. This material is a high carbon (1.00%), chrome (1.36%) alloy steel) and
2) Bismuth sulfide
Additional, I would research a good internal standard or compounds that I would run to try to confirm peaks.I have uploaded a couple of reads you may find helpful. I suspect you are picking up on the chrome from the steel alloy and/or perhaps the D- G- bands formed from the sulfide-carbon bond ( )
Best of luck!
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XT-CF20 is a composite material composed of temperature-resistant co-polyester reinforced with 20% carbon fibers. This material is non-conductive with low tribology property. Could you propose a strategy to coat that material with Ni metal?
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Dear Atef S. Hamada , may be electroplating would work for your composite, and if not you could paint it with some conductive paint to favour the electroplating of Ni. Alternatively you could try plasma sputtering or thermal evaporation. Probably the most cost effective coating method would be electroplating, but it would depends on piece sizes, volume and throughput required.
Hope it helps.
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I want to simulate the tribological properties of solids, liquids, and fluids, please suggest good software.
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COMSOL can solve tribological problems. Some tutorials are already available.
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We had performed tribological experiments of magnetic fluids under the influnce of magnetic field. I want to perform the simulations of those experiments. Which is the best software for the simulation of effect of magnetic field on magnetic fluids? Suggestions are needed in this regard.
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Dear sir
You can try RMexpert and Mawell. Maxwell is very much suitable for time varying electromagnetic simulations, However RMexoert will gives you a rough idea
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We have created a TENG, using PTFE ball and Aluminum electrode in vertical Contact separation mode. The output measured using a high precision Multimeter was 0.3 V. But when we tried to measure current by connecting a resistor in series, and by short circuiting, the output was zero. Can someone point out the problem behind this ?
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As the cell voltage and currents are low, you can high end DC programmable electronic loads for measurements. It will measure mV and mA with very small loads
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Dear all,
I would like to conduct scratch and linear reciprocating tribo-test on my magensium alloy, which has a plasma electrolytic oxide (PEO) layer of about 20 um and 10 - 20 um of Parylene coating on top of it. So it is a double layer system.
I made a research on ASTM standard tests for scratch and linear reciprocating tribo-test and I found ASTM C1624 - 05 for the first and ASTM G133 - 05 for the second. However, I am not sure if these standards are applicable to a double layer coatings as in my system.
Are there some specific standard tribological tests for multilayer coatings?
Thanks!
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ASTM C1624 test standard is the most used standard for this. You can read the article below, this may help you and clear your doubts
An ASTM Standard for Quantitative Scratch Adhesion Testing of Thin, Hard Ceramic Coatings
Stephen T. Gonczy Nicholas RandallFirst published: 05 October 2005 https://doi.org/10.1111/j.1744-7402.2005.02043.x
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Tribology test conditions: Substrate thermoplastic, Counterpart steel ball. Using 1N normal force and 0.5N normal force, Speed 100 mm/s
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Oscar O'Dwyer Lancaster-Jones the friction need not always be with the lubricating surfaces right. It will be between the two bodies in sliding as in pin on disc case or ball on disc. In that case it may be wear asperities may get introduced between two surfaces as an abrasive this may also induce the higher friction right?
What do you think about it?
Thanks for this nice question Kashif Usman
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Hi dears
The empirical equation that i'm looking for, is required to be able to calculate the amounts of cohesion and internal friction angle by using Uniaxial compressive strength and elastic modulus.
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Theoretically you can not calculate these two parameters just using UCS. But, usually it is not necessary to consider the confining pressure effect of concrete. So you can fix the internal friction angle and calculate the cohesion accroding to MC failure criterion. Friction angle of concrete does not change a lot, in the range of 20°~30°.
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What according to you should be researched/accessed with respect to WC based solid lubricant tools? What is your view with respect to future research in this area? (For e.g. Tribological study etc..)
Thanks in advance..
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Thanks Soumitra Paul sir for your extensive in depth answer. I will surely go through the articles.
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What are the main tribological parameters for sliding and impact abrasion mechanisms, other than initial material hardness controlling the wear behavior ?
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Many variables can affect the mechanism and kinetics of wear of sliding surfaces such as: normal load, sliding speed, surface geometry, relative surface movement, surface roughness, type of material, hardness of material, vibration, third body particles and their characteristics, temperature, lubrication (chemical interaction between AW/EP additives and surfaces and formation of a structural layer, etc.).
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Can steel pin of the pin on disk tribometer setup be used in doing wear rate testing of sintered Alumina??
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Your requirement is assessing the wear rate of sintered alumina. There would be an application in mind which is prompting you to carry out the tribometry. Try to choose the counter-body (ball/pin), keeping the application in mind. Try to find out the counter-body in the actual application against which the sintered alumina component is interacting.
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Is there any range of load variation in four ball tribometer during anti wear test.
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There are two way that you can consider performing experiments.
1. The test were performed based on the standard ASTM D 4172. In the standard it clearly states that the load variations should be +/- 0.2 kg that means +/-1.92 N variation to consider test to be admissible and results to be reliable. Hence, the variation in 17 n is definitely a significant variation. This is condition is considering the variation in load during the testing.
2. If you are planning to design your experiments such that variation in the load is considered one of the parameters then you have freedom to do so.
Hence, if your question is based on 1 or 2, you have the answer for that.
Hope this helps
Thank you
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If no what could be the reason for obtaining two different tribolayer of different colors viz. light grey and light grey shiny during on the wear track?
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I take your terms ‘tribolayer’ and ‘glaze layer’ to refer respectively to diffusely and mirror-like reflecting surfaces. In effect the surface layer of the sample being tested is being smoothed at the micro level by the rub test and is becoming more mirror-like. In consequence light reflectance is more diffuse before and more directionally oriented after rubbing. In practice the surface reflectance is typically a proportionate combination of both modes. The light grey shiny wear-track after rubbing thus reflects more light directionally, and may appear slightly lighter and the rougher un-rubbed surface may appear slightly darker due to light scattering.
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Archard's law does not consider the hardness of both the material.
No Sliding velocity term present
No Temperature term
Non-linear behavior of Wear coefficient not considered.
Are there better laws that can predict wear better.
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If I capture what you are after correctly, then.
If you are struggling to use Archard Wear Law for your parameters, you can look into other predictive tools like a DOE to aid you. However, you need data on the parameters you are evaluating to create predictions. This is not any better than Archard Wear Law, just a different way.
There are three Laws of Wear; wear increases with sliding distance, wear increases with normal load, and wear decreases as the hardness of the sliding surface increases. These build Archard Wear Law. You can use these individually for predictions, but may not yield much value, unless you build your bespoke equation for your case. Archard Wear Law can be very useful if you have data on the wear coefficient.
Hope this helps.
Oscar
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Tribology of lithium.
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Lithium is a soft metal, with a Young's modulus in the range of 5 - 8 GPa. Yield strength is about 0.6 - 0.8 MPa. Elongation is about 50%. Therefore it is plastically deformed at very low stress levels. When exposed to air it will immediately oxidize to Li2O which is a brittle ceramic. Li will oxidize even at very low oxygen partial pressures (~10-40 bar). Therefore, if lithium is used as a solid state lubricant to reduce the friction between two mating surfaces, the lithium needs to be coated with an impervious layer of lubricant that completely prevents oxidation of lithium. Formation of Li2O will cause scoring of the surface.
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As there are a lot of works that are published over the years that compare the mechanical properties to abrasive wear behaviour. According to Lancaster model, the UTS, elongation (total) and hardness considered alone are can be sometimes related to abrasive wear behaviour. However, the combination of afore-mentioned mechanical properties can be related. similar study was conducted by Ratner et al. where they relate the stress and strain at rupture to abrasive wear that is in good agreement. On what basis we relate the mechanical properties with tribological properties.
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I think abrasive wear (both two and three body) and sliding wear must be looked at differently. I am not sure that Hemanth and Sergei are talking about the same tribosystem.
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The misconception of Cloud-cloud collision is unable to show continuous triboelectric effect and charge differentiation of clouds. Rather, now charge exchange. Rather, wikipedia mentioned charge exchange between uprising supercooled water and ice droplets and Graupel (soft haill).
But both are nearly same material (water and ice)- why and do they exchange charge? even if they dow, how only state and crystallinity change of a material can change its triboelectric properties? Is there any structure-property justification of triboelectric series, anyway?
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The plausible charge separation mechanism in convective clouds, leading to lightning, was suggested by Baker et al. (1987) (Q. J. R. Meteorol. Soc. 113, 1987, pp 1193–1215). The essence of the process is the interaction of particles with different growth rates and different electrical charges. The succinct summary is presented by Saunders in the paper “Charge Separation Mechanisms in Clouds”
>>Begin quote:
“A thunderstorm charging mechanism based on vapour deposition rate, first proposed by Baker et al. (1987), has been successful in helping to account for differences between the results from various laboratory studies. The concept follows on from the result described earlier that, during collisions leading to the removal of some surface mass from the larger particle, fast growing ice surfaces charge positively and conversely, sublimating surfaces charge negatively. Baker et al., suggested that an additional variable comes into play when two ice surfaces having different vapour diffusional growth rates come into brief contact, namely the surface state of the smaller particle in the collision process”.
End quote<<
(A copy of the paper is attached)
In summary, the traditional concepts of charge separation in triboelectric effect, observed in experiments with the Van de Graaff generator, do not have direct application in clouds due to thermodynamic and diffusion processes.
Additional reference:
Lightning: Physics and Effects (Vladimir Rakov and Martin Uman, Cambridge University Press, 2003).
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The coating will be base on Siloxane or PTFE or any other inorganic material. The coating will cure at room temp. or ypto 250 degree centigrade temperature. The continues temperature will be 450 degree centigrade.
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In precision glass molding PtIr coating is used with a Cr adhesion layer, which works upto 600 °C. You can search something in that area.
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I will study more on tribology for my Ph.D.
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In the general (macroscopic) understanding of friction outlined in the previous answers it is important to distinguish between sticking (the surfaces in contact are not in relative tangential motion to each other, for example in ideal rolling of a wheel or a tyre) and sliding (the surfaces are in relative tangential motion).
Under sticking conditions the friction force is a reaction force resisting motion, that means, the value of the force is exactly the one required to inhibit relative tangential motion. The (static) coefficient of friction \mu_s gives the maximum reaction force, \mu_s*N, before the surfaces start sliding.
So, a higher coefficient will allow you to apply a larger tangential force; in the tyre example you wish to have a higher coefficient of friction to get a higher torque "on the street".
Under sliding conditions the friction force opposing the relative motion is fixed at \mu_d*N (the dynamic coefficient of friction \mu_d often has a slightly smaller value than the static one). In sliding the friction force is dissipating mechanical energy to heat and wear, which in many applications will be undesired. That is why sliding surfaces are often lubricated to reduce the coefficient of friction.
PS: a COF close to zero is referred to as superlubricity, not superfluidity. Infact, the linguistic "similarity" to quantum effects like superfluidity and superconductivity is quite misleading.
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As they both follow Reynolds euqation and the same elastic deformation law, is there difference between the numerical model of them?
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If I understand your question and the term "soft EHL" (soft solid materials?) correctly, there will be some differences.
In traditional EHL, solids are made from hard materials. The contact surface is therefore relatively low, the contact pressure is high (1 GPa or more) and the film thickness is very thin (100-200 nm).
The situation is significantly different in soft EHL: large-size contacts, medium pressure, thicker film thickness.
This will necessarily have consequences on how to solve the problem numerically even if the fundamental equations are the same or almost the same. Reasons among others: the effect of pressure on lubricant viscosity, the extension of the deformed solids zone will be very different, which will very likely require a re-examination of the adimensionalisation and numerical resolution strategies,
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Researchers have explored relations between mechanical and tribological properties and still this process is on. I just wanted to ascertain if there is any possible relation ship between compressive strength and wear rate of metal matrix composites.
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Any wear process is very complex and depends on many factors, including material properties, ambient conditions, regime of lubrication and so on. So, wear rate reflects rather properties of the whole tribological system than properties of any single material. The only case of positive correlation between strength of material and wear factor has been stated for intensive abrasive wear (see Khrushchev's works ). In general, there is no relation between compressive strength and wear rate.
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Hello.
I have begun studying Contact Mechanics very recently, and I am having trouble in understanding the Reduced Young's Modulus (E*).
I have looked at several different books, and I haven't been able to understand why they define E* differently.
When two bodies of Young's Moduli E1 and E2, and Poisson's ratios of v1 and v2 are in contact, I have seen the following definitions:
1) as seen in the attachment 1.PNG:
1/E* = (1-v1²)/E1 + (1-v2²)/E2
2) as seen in the attachment 12.PNG:
1/E* = (1/2)*((1-v1²)/E1 + (1-v2²)/E2)
The first approach would result in a value of E* that is lower than both E1 and E2, while the second approach yields a value of E* that is between E1 and E2.
Another thing that makes me curious is that the first approach is more frequent in books, while I have only seen the second one in a couple of books and papers. But, for some reason, most of the online calculators for contact mechanics agree with the second approach.
Certainly, I am failing to understand this matter properly and, if possible, I would like to know the difference between both approaches with your assistance.
Thank you very much.
Sincerely,
Diogo
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Hi Diogo,
It backs to how you use E* and how the contacting curvatures are defined. You need both equivalent radius (Re) and Equivalent stiffness (E*) to calculate the contact pressure.
however, as Johnson has mentioned in "Contact Mechanics" or :
an equivalent radius Re defined by
Re = (R'R")^0.5 = 1/2 (AB)^-0.5
If the two bodies are solids of revolution, then
R', = R ; = R 1 and R; = R i = R 2 , whereupon A = B =1/2 ( l / R 1 + 1/R 2).
Thus contours of constant separation between the surfaces before loading
are circles centred at 0. After loading, it is evident from the circular symmetry
that the contact area will also be circular, Two cylindrical bodies of radii R 1
and R 2 in contact with their axes parallel to the y-axis have R ; = R 1 , R1'' ; = inf,
R2 = R 2 , R 2'' = inf, so that A =1/2 ( l / R 1 + 1/ R 2), B = 0. Contours of
constant separation are straight lines parallel to the y-axis and, when loaded,
the surfaces will make contact over a narrow strip parallel to they-axis. A special case arises when two equal cylinders both of radius
R are in contact with their axes perpendicular. Here R 1 = R , R ; = inf, R ; = R ,
R2'' = inf) a = n/2, from which A = B = 1/2R. In this case the contours of constant
separation are circles and identical to those due to a sphere of the same radius
R in contact with a plane surface (R2´ = R2´´ = inf).
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The knowledge of tribology is useful in reducing the unnecessary friction and wear between two rubbings surfaces or tribopair. Using tribology appropriate lubricant and lubrication mechanism can be adopted to minimize the friction and eliminate wear which would reduce the wastage of energy and enhance working life of tribopair.
Please add some more answers
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Hello everyone,
I am doing nano scratch experiments on metallic glasses (thin films). In particular I did a series of constant load scratches. Generally if one does scratch testing at different loads, the COF can be divided into several regimes. 1st, adhsion dominated elastic only (COF decreases with increasing load), 2nd elastic plastic transition zone (COF inceases with increasing load) and 3rd plastic zone (COF stabalizes). Now when doing several constant scratches in the range of 10-10.000uN, it can be seen that the COF first decreases from around 0.3 (10uN) to 0.007 at 1000uN and then increases again to about 0.12, where it stabalizes at around 4000-6000uN. Does anyone know how it is possible to gain such a low COF at 1000uN? Im using a Hysitron Ti980 triboindenter and a conical indenter with a hemispherical tip with a radius of about 5um (dimond tip). A similar behavior can be seen in DLC coatings, however with a higher COF. In addition, I did some ramping load scratches from 0 to 1000uN in which the COF does not drop so low, in fact the minimum is at about 0.7 to 0.8. The constant scratch data however is very reproducable and the low COF at 1000uN can be obtained many times over. I can not explain to mayself why, I hope anyone can shed some light onto this situation for me.
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In the tribology for each there is a called a critical load. Wich the load Will be without effect on the friction coefficient. And for each wear test there a steady state in the evolution of friction coefficient.
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1-hardness of hard material is not considered
2-not discuss multipass
3-not addressed the role of wear debris size and shape
4-hardness after experiment not considered.
I wish to know more points, apart from the above plz suggest.
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Archard equation W=k*Wn*s/H allows the calculation of wear volume, but one problem is the hardness H of the softer material at the sliding interfase. Since wear at the boundary/mixed or hydrodynamic regime only takes place in the few microns range, this hardness is not easy to measure, due to the fact that bulk hardness is the one that is involved using vickers and rockwell methods and usually during sliding the top surface suffers strain hardening. This is the reason why is preferable to use wear rate Wr=V/Wn*s
Where V is wear volume Wn is normal load and s sliding distance, being this equation independent of hardness.
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I want to find data about oil viscosity, water in oil, metallic wear debris particles for condition monitoring for electromechanical systems. The data should be monitored by online sensors because the sampling period of offline analysis is large. Let me know if you have any suggestion.
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Your order is in the lubricant centers of interest to you
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In my wear results, the effect of parameter will give different results for wear volume loss and wear rate. For instance, the wear volume loss is increase with the increase of applied load, However, if I use wear rate, the wear volume loss will divided with load and sliding distance which will make the wear rate decrease with increasing applied load. So which one I should use i.e. wear volume loss or wear rate to report my wear data?
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If the applied load and the sliding distance are the same for all tribo-tests, I think it is better that you analyze directly the wear volume and not the wear rate.
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For our final year project we thought of doing viscosity,wear and friction in nano Lubricant but our professor says there will be no change in viscosity. So what are the other options we have?
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Oil film thickness in the lubrication
Surface roughness
Tribofilm formed on the worn surfaces
Morphology of the worn surfaces (wear mechanisms)
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I want to coat over a small area with the diameter of the circular area being just 3 mm. The coating material is epoxy nanocomposite with a inorganic filler and the material has to be coated over the Pin of pin on disc tribometer.
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Hello Murali. You could coat with a diamond carbon PECVD (Plasma Enhanced Chemichal Vapor Deposition) coating or another of your choice. You would have to leave exposed only the region that will receive the coating.
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Suppose I test sliding wear resistance of a nanocomposite material using a pin on disc tribometer. Now once I get the specific wear rate can I use it to predict the wear rate of the same material when it is used as a coating over a substrate. Is there any standard to do the same ?
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You need to consider residual stresses of the coating as well.
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I cannot coat a pin because it is too small. Can I coat a large specimen and use it as disc wherein pin would be the counter face.
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It depends what kind of application process are you targeting...but in most of the cases it's an only way to go. I would do that ;)
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Any books/literature that will help me understanding the procedure?
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I think this link can help you,
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I am enrolled in 1st year PhD, in November 2018 at the Faculty of Science and Technology, Department of Science  of the material,, chemistry specialty of the University of khenchela- Algiers.
The subject that I intend to develop in my thesis is Synthesis and structural, electrochemical and tribological characterization of a nanostructured titanium-based compound (Ti-Ni) for biomedical applications .
i'm searching for co superviseur to make an international convention to start my research in TiNi
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Dear Abdenour Guerraoui
Please find rules and regulations of your university, how it is possible to have co-supervisor from outside country. if yes, then you may find well suitable persons
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I want to improve the wear resistance of a clinical implant that its tribologic properties are significant. but I don't know precisely which implant has poor wear resistance
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From my point of view the implants that has poor wear resistance are the hip and knee implant replacement.
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Two experiments were carried out: one with mineral oil and other with vegetable oil. In case of mineral oil the trend of Stribeck curve is followed but in vegetable oil it is opposite. Each test was done five times hence no experimental error is possible.
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Claude Le Gressus
There are two distinct mechanisms of sliding friction. One is related to solids with pronounced surface asperity when only largest asperities are in a physical contact between each other. Then friction losses are caused predominately by plastic and elastic deformations as well as wear of these asperities. Another mechanism of friction is governed predominately by surface energy and chemical bonding between solids in the contact wherein friction losses are caused by creation of new surfaces in the back of a sliding solid body with heat release in removing the surfaces at the front of it as well as in propagation of self-healing shear cracks or voids aka Schallamach waves along the interface between the solids. Occurrence of such voids we observed in extrusion of clay paste through a transparent tubular die, see [ Kulikov OL, Hornung K. (2002) J. Non-Newtonian Fluid Mech., 107:133–144 ]. We demonstrated in our experiments that flow instability known as sharkskin as well as stick-slip occurrences are suppressed and molten polyethylene slips along walls of a tubular die if the die's inside is coated with silicon rubber. Remarkably, that even a very thin elastic coating can be used to ignite slip, see [ Kulikov O, Hornung K. (2004) J. of Non-Newt. Fluid Mechanics.V.124 (1-3), pp.103-114 ]. Moreover, an onset of slip and magnitude of friction losses depend on elasticity of the coating, see [ Kulikov O, et al. (2007) Rheologica Acta, V. 46(5) p.741 ]. That is, with more elastic material of the coating the slip onset happens at lower shear stress with lesser friction losses. These findings were developed later on into advanced lubricants for engines and machines that almost eliminate wear and friction losses, see my project and references in it. What is bad is that this engine oil extends longevity of engines and saves fuel up to 30% - nobody needs it.
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In tribology of polymer cases we know that:
In contrast to other materials, the tribological properties of polymers depend on the tensile strength and the toughness rather than on the hardness. Due to their thermal properties, polymers are very sensitive to frictional heating. Please suggests in case of friction stir welding of polymer, property mainly depend on tensile strength or toughness or hardness?
Your opinion is highly appreciated
Regards
Sudhir
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Among three kinds of polymeric materials; thermoplastics, thermosets, and elastomers, only thermoplastics are the weldable polymers. It is due to their ability to be reshaped after heating below their degradation temperature.
Several researchers such as Bilici and Yukler are depending tensile strength especially lab shear.
Bilici MK, Yukler AI (2012) Effects of welding parameters on friction stir spot welding of high density polyethylene sheets. Mater Des 33:545–550
I hope this help you.
Regards
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A fish in river forming tribo couple where 2nd and 3rd system is water.
Can you tell me some more example where 2nd and 3rd system is same.
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We need 4 elements: 1. body, 2. counterbody, 3. interfacial medium, and 4. environment medium. For example, humidity affects significantly the Friction behavior of ceramics and polymers. Regards.
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On conducting ball on disc test, i found friction and wear rate of pure copper sample increases initially with load then it starts decreasing with load. On analyzing the SEM micrographs ( cannot share due to plagiarism issues), i found initially with increase in load abrasive wear occurs then on further increasing the load adhesion becomes the major wear event. Is there any other study, which supports my result? If it is there, Plz give me the reference.
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Rather than load what is more relevant is contact pressure. The contact area may increase due to wear of the ball and this as a consequence decreases the the contact pressure.
Alternatively it might be that both loads and contact pressure are increasing but wear dimities due to adhesive wear as already mentioned... basically if the contact pressure is high enough, the wear particles are "welded" back to the disc or ball rather than being removed from the contact area.
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gravel road is three body abrasive wear,
smooth road is two body abrasive wear.
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I think abrasion will cause the friction to increase as a function of the road. Thus there will be frictional component that is perpendicular to the tire thread and this will help in the peeling off of large particular that will be highly abrasive as the speed increases.
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I had a mineral oil of 460cSt (containing sulphur and phosphorus), after addition of nanparticles (carbon nano tubes and graphene) the viscosity decreased significantly. literatures says that the presence of asphaltenes and nanoparticles may lead to a decrease in viscosity.
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Yes. However, the concentration of asphaltenes varies considerably from light oil to heavy and extra-large heavy oil such as bitumen.
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In normal tribological condition when silding speed increase wear volum loss increase but at certain increasing speed wear volum loss deacrease, why?
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Hello! It could happen because in the friction pair with increasing of sliding speed the friction coefficient, as rule, decreases and therefore there is possible the decreasing of volume wear too, due to the direct-proportional dependance of friction coefficient and wear.
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We found that sliding of cartilage against an artificial meniscus could increase friction during the swing phase and long term elevated friction could cause cartilage wear.
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Again the biomechanics differ from young to old age. Older people suffer from high friction and we should adjust the flexibility
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I have deposited pure Cr and W films by unbalanced magnetron sputtering method and then prepared films by doping them with Ag. The hardness and modulus of these coatings are lower than that of the pure films. What can be the main reason behind this ? Usually addition of another element increases hardness and modulus.I would really appreciate any research article or help from experts.
Thank you !!
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Two points. First, While the modules is a function of atomic properties such as electronic bonding, the hardness is a function of film properties such as thickness and grain structure, e.g., dislocation mobility. Secondly, when you report hardness and modulus values, be sure to quote the appropriate precision, based on the statistics of the measurement, and don’t just quote the output from the machine. Your table shows the values to one, two, three, and four significant figures. I doubt the precision is three significant figures, let alone four. Also, the accuracy of the values, which is another issue altogether, depends on the models used to compute hardness and modulus.
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Hello, just a quick question, why do we use tests in the tribological laboratories of bovine serum, diiodomethane ... to check the wettability of dlc ?
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Diiodomethane is typically used to determine the surface energy of materials and coatings. It is used because it is a non-polar liquid - for the calculation of surface energy (and its polar and dispersive components) you need at least two liquids, a polar one (typically water) and a non-polar one (typically diiodomethane). See e.g.: https://www.kruss-scientific.com/fileadmin/user_upl