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friction coefficient of UHMW and HDPE

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kjoiner

kjoiner

Mechanical
Oct 31, 2002
459
I'm mainly looking for the fricion coefficient of HDPE but I would like a second source for the friction coefficient for UHMW as well. I don't see HDPE friction listed in my sources so I was wondering if anyone in plastics would be able to provide it. The sources I'm working with give a friction coefficient for UHMW of .14. Could someone verify this?

My application is a bearing strip that will be riveted to its mounting surface. My only concern with switching to UHMW is that it tends to creep and I don't want to have a problem with it working loose over time. If UHMW is no worse than HDPE then I should be fine. Can someone provide some insight into comparing the creep issues with these two materials.

Thank you for your help

Kyle Joiner
 
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Thanks for the link. It looks like the coefficient for HDPE is .28 vs .15 for UHMW. Do you have any info on the creep properties of UHMW? Thanks

Kyle
 
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It's more of a stress relaxation problem than a creep one. Creep occurs when a material is subjected to constant load and continuously deforms over time.

Stress relaxation occurs when a material is subjected to an applied fixed deformation, the initial stress set up decays over time.

When the rivets are fitted they will compress the polymer causing a compressive stress. Assuming that the rivet is perfectly stiff (compared to the polymer) then it won't change length over time.

The stress in the polymer will start to reduce due to stress relaxation but as the rate of relaxation is governed by the stress level it should never quite reach zero.

In this case the rivets should never actually become 'loose' but the holding force could drop off enough to allow slight movement of the part under working condtions which could in turn could cause wear around the mounting holes.

UHMW-PE slab parts are often secured with bolts rather than rivets which I would recommend in wear strip applications as they make replacing the strips easier.

regards

Bryan Deacon
Ticona UK Limited
 
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