Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here




Hey guys gonna be doing a study into the effects of surface finish (abraided and non-abraided)on the frictional characteristics between aluminium 7075, and Polyurethane(1.4u)
in dynamic conditions.
Any info on experimental techniques would be greatly appreciated


Dry or lubricated condition?


Dry conditions


Don't know your sliding speed range. Polyurethane won't handle high sliding speed and no lubrication.  High speed as well as load can rapidly raise surface temperature above the mp of polyurethane. So you will need to pre- determine your load and sliding speed range. As a quick general background, hard surface -v- soft surface and what may happen at high sliding speed you might want to look at Thread342-92753.
Assuming you intend to work with relatively light loads and slow to dead slow surface speeds, I doubt that surface finish will make a huge difference to dynamic friction, once bedding in has occurred.


Thanks rnd2 really appreciate that info, i cant see it having a big effect either.
Might as well be bold and ask you if you could suggest a speed range, got a presentation next week and am struggling to find any sources.


This website may assist with basic comparisons. It at least gives you a base friction co-efficient for natural polyurethane of 1.26 static and 1.14 dynamic according to ASTM 1894-90. Unmodified, not a good dry sliding material, but improves with lubricity additives, in this case 0.42 and 0.3 respectively and a useful direct comparison can be made, as apparently the same ASTM test standard was used.
Like many plastics, material characteristics vary  as each manufacturer strives to develop properties to enhance their product.
Speed and load wise? Hmmm.
We are currently testing bone dry bearing material brand XXXX (not polyurethane).
Shaft speed is 44 rpm
Shaft dia. is 55mm
Bearing length is 110mm
Bearing load is 15 Kg
This load and speed is not particularly onerous for this particular material, and each 200 hour period the load will increase with 5 Kg increments until failure. BUT, I doubt that unmodified polyurethane could cope even at the modest 15 Kg load and shaft speed.
So, best guess, a continuous rotating shaft surface speed of approx 0.04 m/s, a bearing pressure of approx 0.052 MPa or 7.5 psi might be just be too much for natural polyurethane.
Hope that helps.


You might want to compare a burnished finished to a ground finish.
The P/V value should be documented.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close