Respected Sir, This is the most beautiful and elaborate explanation of the Stribeck Curve. I had invested a lot of time in trying to understand the nature of curve through a lot of books but could not succeed until I found out this video . Thank you very much for putting up this lecture on youtube. As a professor in IIT Delhi, the country's elite technical institution of the country your youtube channel will help the engineering students of the country to learn from you. Please also share your knowledge in other subjects like Mechanical Behaviour of Materials and Materials engineering that you teach at IIT. It would be a blessing for the entire engineering students of the country to learn it from you and through your TH-cam Channel. May Lord Shiva give you Grand Success in all your endeavours. 🙏🙏🙏🙏🙏
Sir, I am really appreciate the effort you put on preparing this video, I have been struggling with this lubrication regimes concept for days, reading different blogs and witching different movies but none of them explains the concept as you did, now I am satisfied. The way you use and how you approach this concept was strategic and clear. Much respect!!
Thank you so much for this video, really helpful. I was wondering what formula for the friction coefficient can we use. in case i want to compare an experimental results curve with another theoretical curve?
Hi Prof., can you provide some insight on how friction reduces when speed increases from mixed to EHL? Also, share thoughts on the film formation mechanism in the EHL region. Can EHL be applicable to flat-on-flat contacts?
Thanks for asking. As relative speed increases, greater amount of fluid is pulled between the two surfaces because of the stick wall boundary condition between the fluid and the surfaces. More liquid coming in causes a hydrodynamic pressure at the interface and hence greater load bearing capacity is created. This causes the surfaces to move apart with thicker fluid film. Hence, the coefficient of friction decreases because there is no solid to solid contact anymore. In EHL, the above action happens but one more thing happens which is that the contacting surfaces deform elastically providing even thicker liquid film formation. For example, this is also the cause of hydroplaning when you drive at high speed through a pool of water when it is raining. The tyres deform and provide more water coming in between the tyre and the road surface. This effect is large when the tyres of the vehicle are little worn-out or smooth.
Minimum film thickness can be calculated if you know the Sommerfeld number or the Bearing Characteristic Number for a journal bearing. A numerical method was developed and based on the results, there are some graphs to find out the minimum film thickness in a journal bearing. A good book to follow is "Principles and Applications of Tribology by Bharat Bhushan". Another book is "Fundamentals of Fluid Film Lubrication By Bernard J. Hamrock, Steven R. Schmid, Bo O. Jacobson. This book can be downloaded from the internet.
Respected Sir, Which book can we read the correct explanation of all the lubrication regimes with real world examples that also give detailed explanation about the curve? Kindly tell
Good day to Engineering Materials-Tribology-Design, may I ask whether the stribecj effect only applicable to lubrication system ? or to pure friction as well? thank you so much
This is only applicable when there is liquid lubricant present. For hydrodynamic lubrication, need enough lubricant presence otherwise only mixed-lubrication or boundary lubrication regime will occur.
@@engineeringmaterials-tribo5142 I see, I have dry friction condition and saw stribecj-coulomb friction model for low-speed regime where the lubrication effect is an additional model to dry friction model together// Thus, I got messed up whether Stribecj effect is needed for dry friction as well to show smooth or obvious stick-slip motion or behaviour in the practice? Than you Engineering Materials-Tribology-Design for replying my comment /
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Very clear explanation and give a vivid example to show the complex concept to understand
Respected Sir, This is the most beautiful and elaborate explanation of the Stribeck Curve. I had invested a lot of time in trying to understand the nature of curve through a lot of books but could not succeed until I found out this video . Thank you very much for putting up this lecture on youtube. As a professor in IIT Delhi, the country's elite technical institution of the country your youtube channel will help the engineering students of the country to learn from you. Please also share your knowledge in other subjects like Mechanical Behaviour of Materials and Materials engineering that you teach at IIT. It would be a blessing for the entire engineering students of the country to learn it from you and through your TH-cam Channel. May Lord Shiva give you Grand Success in all your endeavours. 🙏🙏🙏🙏🙏
Sir, I am really appreciate the effort you put on preparing this video, I have been struggling with this lubrication regimes concept for days, reading different blogs and witching different movies but none of them explains the concept as you did, now I am satisfied.
The way you use and how you approach this concept was strategic and clear. Much respect!!
👍😊
Kudos👌
excellent describing. easy to understand
Thank you so much for this video, really helpful. I was wondering what formula for the friction coefficient can we use. in case i want to compare an experimental results curve with another theoretical curve?
Friction coefficient is always calculated as the ratio of tangential force to the normal force. Please let me know if your question is different.
Sir very useful information and explained very nicely, easy to understand
Thanks👍
Hi Prof., can you provide some insight on how friction reduces when speed increases from mixed to EHL? Also, share thoughts on the film formation mechanism in the EHL region. Can EHL be applicable to flat-on-flat contacts?
Thanks for asking. As relative speed increases, greater amount of fluid is pulled between the two surfaces because of the stick wall boundary condition between the fluid and the surfaces. More liquid coming in causes a hydrodynamic pressure at the interface and hence greater load bearing capacity is created. This causes the surfaces to move apart with thicker fluid film. Hence, the coefficient of friction decreases because there is no solid to solid contact anymore.
In EHL, the above action happens but one more thing happens which is that the contacting surfaces deform elastically providing even thicker liquid film formation. For example, this is also the cause of hydroplaning when you drive at high speed through a pool of water when it is raining. The tyres deform and provide more water coming in between the tyre and the road surface. This effect is large when the tyres of the vehicle are little worn-out or smooth.
What is the equation or formula for friction coefficient and dynamic viscosity
thanks
Sir, how to calculate the effective film thickness? Thank you for this wonderful lecture 🙏
Minimum film thickness can be calculated if you know the Sommerfeld number or the Bearing Characteristic Number for a journal bearing. A numerical method was developed and based on the results, there are some graphs to find out the minimum film thickness in a journal bearing. A good book to follow is "Principles and Applications of Tribology by Bharat Bhushan". Another book is "Fundamentals of Fluid Film Lubrication By Bernard J. Hamrock, Steven R. Schmid, Bo O. Jacobson. This book can be downloaded from the internet.
Respected Sir, Which book can we read the correct explanation of all the lubrication regimes with real world examples that also give detailed explanation about the curve? Kindly tell
Among good books is one by Khonsari and Booser (Applied Tribology). Also read book by B Bhushan (Principles and Applications of Tribology).
thank you for useful information
You are welcome!👍
i wasn't understand why 2. part of the stribeck curve has lower friction coefficent than region 3. thank you
I did not get your question correctly. Could repeat and re-phrase your question? Which are part 2 and 3 you are referring to?
Good day to
Engineering Materials-Tribology-Design, may I ask whether the stribecj effect only applicable to lubrication system ? or to pure friction as well? thank you so much
This is only applicable when there is liquid lubricant present. For hydrodynamic lubrication, need enough lubricant presence otherwise only mixed-lubrication or boundary lubrication regime will occur.
@@engineeringmaterials-tribo5142 I see, I have dry friction condition and saw stribecj-coulomb friction model for low-speed regime where the lubrication effect is an additional model to dry friction model together// Thus, I got messed up whether Stribecj effect is needed for dry friction as well to show smooth or obvious stick-slip motion or behaviour in the practice? Than you Engineering Materials-Tribology-Design for replying my comment /
@@limkwerly8508 For dry friction, use Amonton's law and Coulomb's law.
@@engineeringmaterials-tribo5142 I see, noted that , than you Engineering Materials-Tribology-Design
for replying me ~~
Great 👍
Thank you 👍