From Scott Bairs peer reviewed paper: " A More Complete Description of the Shear Rheology of HTHS Journal Bearing Lubrication. May 2007 TLT magazine." COPYRIGHT STLE
Scott Bair is a STLE member and from Center for HP Rheology, GT, George Woodruff School of Mechanical Engineering.
There has been much discussion here of viscosity and best this and that. Let me share that most here ( even many of the BITOG authors) have no idea what a complex subject this is as relates to Journal bearings in a IC automotive engine.
This article is one the best I have read and am still digesting. It describes what I have been dealing with in testing, R&D and racing engines for years. Our recent work on the RS4 program is defined by many of these formulas and wonderful work Scott has produced. I am just a humble lube testing analyst and appreciate the in depth work of Scott here.
Scott hits a home run by my measure and had support from a grant by Valvoline for the work.
I highly recommend that those who can access this paper and study it.
Basically we know that in the ongoing search for a magic vis for best wear protection and efficiency has been a blind mans bluff for many.
The Abstract states that: " High Pressure viscometers which have been used in the past for rheological properties of EHD can now be used to obtain flow curves for motor oils that extend much deeper in the shear- thinning regime than conventional HTHS viscometers.......Sufficiently accurate theory exists to possibly design lubricants for both high load capacity and low friction by balancing pressure and shear rate - effects."
4 defining viscosity measures for those who dig a little deeper here to ruminate on. From the paper, edited for my typing limits.
"1) Isoviscous. The viscosity independent of pressure and shear rate.
2)Piezoviscous, Newtonian. Viscosity depends of pressure only.
3)Nonpiezo, Shear Thin. Viscosity dependent on shear rate only.
4)Piezoviscous, Shear Thin. Viscosity depending on both pressure and shear rate."
Enjoy, Terry
Scott Bair is a STLE member and from Center for HP Rheology, GT, George Woodruff School of Mechanical Engineering.
There has been much discussion here of viscosity and best this and that. Let me share that most here ( even many of the BITOG authors) have no idea what a complex subject this is as relates to Journal bearings in a IC automotive engine.
This article is one the best I have read and am still digesting. It describes what I have been dealing with in testing, R&D and racing engines for years. Our recent work on the RS4 program is defined by many of these formulas and wonderful work Scott has produced. I am just a humble lube testing analyst and appreciate the in depth work of Scott here.
Scott hits a home run by my measure and had support from a grant by Valvoline for the work.
I highly recommend that those who can access this paper and study it.
Basically we know that in the ongoing search for a magic vis for best wear protection and efficiency has been a blind mans bluff for many.
The Abstract states that: " High Pressure viscometers which have been used in the past for rheological properties of EHD can now be used to obtain flow curves for motor oils that extend much deeper in the shear- thinning regime than conventional HTHS viscometers.......Sufficiently accurate theory exists to possibly design lubricants for both high load capacity and low friction by balancing pressure and shear rate - effects."
4 defining viscosity measures for those who dig a little deeper here to ruminate on. From the paper, edited for my typing limits.
"1) Isoviscous. The viscosity independent of pressure and shear rate.
2)Piezoviscous, Newtonian. Viscosity depends of pressure only.
3)Nonpiezo, Shear Thin. Viscosity dependent on shear rate only.
4)Piezoviscous, Shear Thin. Viscosity depending on both pressure and shear rate."
Enjoy, Terry