Please refer the link provided below for the details of the experimental setup.

The tribometer carries out sliding wear test for a given material against a rotating disc ( usually made of alloy steel HRC 65) and measures the frictional force [provides the friction coefficient which is equal to the ratio of the frictional force (in N) to the applied load (in N)].

If you are aware of the tool material, you can replace the disc (existing on the equipment) with a disc made of the tool material to get the exact frictional coefficient.

http://ducom.com/test-instruments/tribometers/rotary-pinball-on-disk-tribometer/

Dear Anand Pai,

thank you for your important hint and valuable answer!!

Yours Peter

Peter:  I would wonder whether the real friction coefficient changes as the can extrusion progresses.  

The extrusion process could be taken up as a case of sliding friction. Normally the friction coefficient for such interactions depends on

i) Load/ Stress on the work material

ii) Interaction between the mating surfaces (Disparity in hardness and mechanical properties between work and tool materials, surface morphology etc.)

iii) Speed of interaction (in this case the rate of extrusion)

iv) Distance of interaction (length of the extrusion)

During extrusion, there will be a ductile flow of the work material with a possibility of change over in its mechanical properties like Hardness and strength. However the tool material can be assumed to potentially retain its properties over the working process.

Hence a series of wear tests on the tribo-meter could be carried out incorporating the parameters mentioned above (from Extrusion Process) for :

• varying load (to account for variation of stress within the "can" material during the mechanical working)
• distance and speed may remain the same if the extrusion setup and the rate of extrusion are pre-set for the apparatus.

This would give the range of values the friction coefficient is supposed to attain and a RMS (Root Mean square) or mean value could be taken as the standard friction coefficient.

I have attached a paper on friction models for your kind reference.

Dear Anand Pai,

again thank you very much for this comprehensive answer including the impotant publication. you helped me a lot!!

Thank you

Peter

Dear Peter,

I have determined the friction factor in this case using a rather complex approach where I use contrast pins inside the workpiece to trace metal flow and then compares metal flow with that obtained in FEM-simulation. I found that the friction factor increases throughout the course of the process. Please send me an email about (saerch on my name on internet and you will find my address)  this and I will provide you more informastion about this work.

Best regards Henry Valberg

Dear Henry,

thank you for your answer!

Unfortunately I could not find your email. So I give you mine

[email protected]

Would be very Kind of you sending  to me your results.

Best wishes

your Peter