Which spring washers to avoid Creep 2

[kittt]

Hello everyone,

There appear to be several types of spring washers out there:

Belleville Washers:

http://lh4.ggpht.com/_EhOQGW2GHBg/Sngf58FY0AI/AAAAAAAAHuA/7XVYi9spfRo/BellevilleSprings2.gif

Cut washers:

http://www.shop4fasteners.co.uk/aca...tion_spring_washers_stainless_steel_a2_a4.jpg

Wavy washers:

http://www.sdp-si.com/estore/CoverPg/Hardware/Wave_Spring_Washers.jpg

Do you guys know which type would be best to use when joining 2 Carbon Fiber structural parts while minimizing creep and stress relaxation?

Thank you in advance for any comments or feedback.

Cheers,
Christopher

 

[MintJulep]

Either the Belleville or wavey springs should work. Cut or split washers no.

Either option will increase the contact stress due to the small contact area, unless you use a flat washer between the springs and the carbon fiber part.

They don't really "minimize" creep or relaxation. If properly sized and things are properly tightened they can compensate for some amount of fastener preload loss due to creep and relaxation.

 

[racookpe1978]

Nordlock work well (They are essentially a matched set of paired washers cut with ramps on each face so any unlocking vibration can't be relaxed and the bolt stays at the original tension) - But I've only used them on steel-steel applications, not on carbon fibre jobs or flanges.

They are more expensive than internal or external toothed "lockwashers"... which don't really work at all.

 

[MintJulep]

Nordlocks solve a completely different problem then the OP is trying to solve.

 

[hydtools]

Bellville or wave washer. Definitely use a flat washer between the spring washer and carbon fiber material. Spring washers can only accommodate creep, not prevent it. Large flat washers will distribute the clamp load and reduce creep.

Ted