steel on steel ( without lubrication at interface i.e. dry interface):- coefficient of static friction (0.5-0.8) drops to 0.4 at initiation of sliding. And with lubrication between them coefficient of static friction drops from 0.16 to 0.04 at start of sliding.

You could use standard 'mu' values available in handbooks unless the process of generating friction causes surface modification. Your problem statement is somewhat unclear. When you say projectile, is the projectile 'impacting' the mild steel tube axially? Does the projectile get lodged in the axial tube? I am asking these questions since rate dependency becomes critical when events happen in a very short frame of time. Also, the physics is no longer quasi static if we consider dynamic events. May be, if you could explain your problem in detail we could have some interesting discussions. Only the bests for you! Cheers!

Thanks to all for response.Dear Sathya Prasad, i am doing a impact related problem a heavy weight mild steel projectile axially impact on a thin mild steel tube.in modelling with abaqus i need coeff.of friction in between both projectile and tube.velocity of impact also higher. Dear Chitaranjan i think i need coeff. of dynamic friction.Is any handbook is available related to coeff. of friction between surface.

Dear Sanjay:

There are lots of experimental values for coefficient of friction values. Example: a simple Google search immediately showed

Search Results

"Featured snippet from the web

The coefficient of static friction for steel is around 0.6–0.15 and the coefficient of kinetic friction is around 0.09–0.6."

To start with, you could use a dummy value and check the convergence of your FE deck. However, my discussion below is more fundamental. The physical response of the structure depends on the speed at which the projectile hits the tube. The following could happen:

1. If the projectile is heavy, large and impacts with a moderate velocity and the tube is somewhat thin: Then the tube would buckle / crumple. Nothing much for friction to do.

2. If same as above, but with high velocity: There would be severe damage on the tube leading to tube rupturing and flowering life petals of a flower. It might even be lovely to look at and could find a place in the flower vase. :-)

3. If same as #1, but slow velocity:

3a. If the tube is ductile: Then it would catch the projectile like a baseball glove catching the ball. The tube would expand where it catches and there is enough time for the projectile to travel inside the tube. Lots of heat would be generated due to friction, and if the heat is high enough, the projectile would get welded into the tube.

3b. If the tube is brittle: The tube would break into pieces and dissipate the impact energy by forming a large number of new surfaces.

3c. If the tube is made of non-linear material such as rubber: Something else would happen. God knows!

3d. If the tube had less diameter than the projectile, the projectile would suffer Newton's third law and bounce back, assuming the tube to be strong and resilient

3e. If the projectile has less diameter than the tube, it would travel through, but bounce off the wall as it travels, generating sparks that you can enjoy watching.

3f. If your tube is as thin as a coke can, it would crumple like an appalam (papad for North Indians and something like fresh potato chips for the rest), making a similar noise.

3g. The direction in which the projectile hits also matters - axial or radial or tangential?...and so on.

Best would be to sketch your problem and imagine as to what could happen. Then play with a few values of friction coefficients, assuming that those really play a significant role. Once you are happy that the model reasonably behaves the way you had expected, hunt down for appropriate mu values. The reason is, frictional resistance depends on the surface roughness and the normal force, which are generally two independent parameters. In your case, the surface roughness itself could be a function of the normal force and velocity, in which case the problem becomes a little tricky. The bullet lays the track and travels; kind of the bullet slides inside the tube like a toboggan, damaging on the surface on which it is travelling. Contrast this with friction in a bearing where the lubricant and surface finish ensure that nothing untoward happens to the rubbing surfaces.

Not sure if I have been able to convince you, but with the very little problem description, this is the best I could come-up with after compensating for the lack of problem completeness with my vivid imagination that suddenly started running amok.

Please do continue the discussions. I am sure someone would offer some good ideas. I shall also try.

Only the bests to you!

Cheers!