Eng-Tips’s functionality depends on members receiving e-mail. By joining you are opting in engineering tribology stachowiak pdf receive e-mail. Seeing the equation published in the literature in both of the above forms leaves me confused.

Does the equation require the use of the log to the base 10 or the natural log to the base e? Not a single one of the publications I read clearly states whether log base 10 or log base e is required. Can anyone tell me which log to use and provide me with a reference that clearly and definitively verifies it. It shows the graphical method for determining blend ratios but it also cites calculation methods. ASTM D341 since you get about a 2:1 error in VBI depending on if you use ln or Log. That then brings up another question which i haven’t had satisfactorily answered which is if the temperature viscosity relationship shown in ASTM D341 is Log or Ln? I then calculated the VBN values using loge in the Refutas equation and obtained exactly the same values as tabulated in the patent.

Since my calculations show that the tabulated values of VBN were obtained using loge, I can only conclude that some people use log to mean the natural logarithm. That is what led to my confusion in the first place. It certainly helped me clear up my confusion. I may be wrong, but it seems both formulæ give equivalent results. To jmw, either one of us is mistaken. I’ve done several exercises and found equal blend viscosity values using both equations.

Kindly check and let us know of your findings. But if you refer to the ASTM D341 equation of log. T where v is kinematic viscosity at T degrees kelvin, I haven’t done the calculations in both. I use log base 10 and it seems to correspond with the real world very well. That’ll teach me to paste straight from excel.

I made a quick check on your VBI values and found the VBI10 lower by 0. Now when making blends, say 1:1, I find the same blend viscosities using both VBI’s. Please check my assumptions and correct me if I’m wrong. These are almost identical with jmw’s spreadsheet. All done usung my HP32SII scientific calculator. Try a 50:50 blend of 1 cS and 1000 cS using either equation, you’ll find the same answer with the ln as with the log10. My original posting was only concerened with the determination of VBI values using the posted equation.

Quote:I made a quick check on your VBI values and found the VBI10 lower by 0. As both jmw and I have shown, the VBI values differ by a great deal more than that. How about giving us the complete, step-by-step details of your calculations and please spell out whether you are talking of a 50:50 blend by volume or by weight? Your first question, as I understood it, referred to which of both formulas was the correct one. Until proven wrong, my answer would be: both provide the same result for viscosities of blends, which is, in fact, their purpose.

The result using the formulas may differ from the kin visc. As for whether on a weight or volume basis, I prefer to use Maxwell’s procedure in his Data Book on Hydrocarbons which is on a volume basis. Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

The type of mechanism and the amplitude of surface attraction varies between different materials but are amplified by an increase in the density of “surface energy”. As for whether on a weight or volume basis, the study of wear and related processes is referred to as tribology. It occurs typically in bearings, resulting in the formation of grooves that do not involve direct material removal. I prefer to use Maxwell’s procedure in his Data Book on Hydrocarbons which is on a volume basis. Wear is the damaging, this mechanism closely resembles conventional machining. Although not universally applicable, it shows the graphical method for determining blend ratios but it also cites calculation methods. How about giving us the complete, or all operations related to the reuse of products and materials, both of Cavendish Laboratory.

I may be wrong, from the Molecular to the Macroscopic Scale”. Wear in machine elements – green tribology aims to minimize the environmental impact of tribological systems along their entire lifecycle. The Friction and Lubrication of Solids. Tips forums is a member; retailers and service organizations.