I would recommend doing experimental test using a four-ball machine instead of the pin-on disk. The four-ball machine is a common choice for testing lubricants. Also the lubricant has to be characterized for thermal stability, corrosion effect, biodegrability and some other properties.  Therefore knowing the viscosity only is not enough.

 @Sergei Tarasov

Yes of course it is necessary to go for thermal stability, corrosion effect, biodegradability and some other basic rheological properties of Biolubricants.

Four ball testing machine is suitable for testing the load carrying capacity. But for friction, wear and coefficient of friction it is necessary to go for pin on disk.

And my doubt is, weather it is necessary to do the experiment with pin on disk, to know friction and wear behaviour of Biolubricants even after knowing viscosity of Biolubricants, since viscosity plays a dominant role in it.

My opinion is that pin-on-disk scheme is not suitable for tribological testing because of burying the leading pin's edge into a counterbody. Also determining coefficient of friction using an experimental setup is totally useless  for practice because CoF is not a characteristic of materials but rather a function of many parameters such as contact type, roughness, load, speed, temperature and so on. In case of testing the lubricant one can only determine the load-bearing capacity and this is real characteristic  of lubricating efficiency. In case of testing the lubrication efficiency it is usual route is to obtain the Stribeck curve.

@Sergei Tarasov

Thank you sir for sharing your opinion.

The answer to your question: It really depends on your specific system you are dealing or simulating. If there is complete lubricant film between the moving parts, then, no wear should occur and the rheological characteristics of the fluid should be sufficient. So, what are those rheological characteristics?: Do you know the viscosity-temperature and the viscosity-pressure relationships? Viscosity change significantly with Temperature (local temperature) and it could be affected by pressure. In order to say that you know "all the rheological properties," you need to know that relationship in the range of interest. If you have contact between the moving parts, then you have, what it is called: boundary lubrication. On a boundary lubrication situation, the chemical-physical interaction of the molecules with the rubbing surfaces plays a significant role in your system, and it cannot be predicted using only the lubricant rheological information. So, what to test?... Well, that depends on the kind of system you are dealing, and your lab testing should simulate, as close as possible, your actual system. If you are simulating a knee replacement, the relative motion is reciprocating, with variable speeds, so your test, should be using that motion, and applying the corresponding contact pressures and speeds as in the existent system. I could extend more... I recommend you look into: "Design of Friction and Wear Experiments" by Horst Czichos (Chapter of a ASM Handbook).  Hopefully useful. 

Hi,

I'm totaly agree with Mr. Jose Castillo. All depends on friction condition of your friction node. Pin on disc is not good bio-tribometer. The kinematic condition are not corresponding with any kind of natural joints. I have done some experiments on that tester and the result not corresponding to reciprocating movement test.

Also 4 ball is not good. Contact pressure in that case will be huge. It could destroy a macro particles of bio-lubricant.

The viscosity of lubricant will have an effect on friction and wear, but it is not so simple. On pin on disc you have mixed friction.

Use a tester with relatively close kinematic and load condition.

Look for attached publication (sorry it's not in english). We build a special device for similar investigation.

Article Stanowisko do badań tribologicznych w zlożonym ruchu cyklicz...

Article Influence of kinematic conditions of slide/roll friction on ...

@ Jose_Castillo Sir,

Thanks for your valuable comments on my question. The rheological properties that are known with respect to biolubricants are - viscosity, viscosity index, flash and fire points, pour point, acid value and iodine values. 

Actually i am looking forward for experimental studies on tribological characteristics of some biolubricants for AISI 304L material. But as per your comments is it not so important to go for it?

@ Piotr Kowalewski Sir

Thanks for your valuable comments on my question.

Yes, I agree that On pin on disc there will be mixed friction. And 4 Ball tester is for determining the load carrying capacity. Does it not make better contribution in conducting experiments for AISI 304L in presence of biolubricants using pin on disk to find friction force and wear rate.?

May I know that special device for similar investigation?

I was interest in "bio-lubricant" which are used for bio-tribological investigation of endoprosthesis such: ringer solution, bovine serum, distilled water etc.. So "the special device" I used, was the knee kinematic friction tester. Our own konstruction (look at pub.).

Correct me If I'm wrong, but looking at your previous work, I think your definition of "bio-lubricant" is quite different. :-)

@ Piotr Kowalewski

Yes, Sir as you said the definition of "bio-lubricants" are quite different in my case, I am interested in synthesis and testing bio-lubricants(cutting fluids) in Machining process. So as preliminary requirements I am going for tribological property evaluation of these Bio-lubricants.

I agree with Jose Castillo too.

It all depends on the use of lubricant in the system (friction pair). If you are dealing with high contact pressure (point or linear contact) viscosity doesn't play main role. That property (anti wear, anti friction properties for boundary friction) is called lubricity and the best way (especially to compare with some other fluid) is to use 4-ball tester. You can use ball-on disk (rotational motion) or ball-on-flat (reciprocating motion) to evaluate wear and friction coefficient in your tribological pair. If contact is rather linear or friction is typically hydrodynamic (or EHD) you can use block-on-ring tester.

@Krzysztof Gocman

Thank you sir, for your answer

It is essential to study the different regimes of the lubrication to assess the performance of a lubricant.

i) hydrodynamic

ii) elasto-hydrodynamic

 iii) partial or mixed

iv) boundary.

Hence a reciprocating tribometer is suggested to  used for the evaluation of tribological properties of lubricants.