Belleville washers
Belleville washers
(OP)
Hi guys,
I need an info on Belleville washers. I want to know what is the max number of times a single belleville washer can be used/reused. I want to know this because the mechanics where I work were once told to only use the same washer twice. We have a LOT of washers here and I wonder if they could use them more than 2 times.
Thanks a lot for your time,
Simon
I need an info on Belleville washers. I want to know what is the max number of times a single belleville washer can be used/reused. I want to know this because the mechanics where I work were once told to only use the same washer twice. We have a LOT of washers here and I wonder if they could use them more than 2 times.
Thanks a lot for your time,
Simon





RE: Belleville washers
then there may be a problem of keeping track of how many time they have been re-used
RE: Belleville washers
Based on this impression, it would appear that this is an issue which the manufactures are talking about without really being prompted to do and as such it suggests a couple of things. 1) it feels as if there has been problems in the past, which could very well explain why your mechanics warned you about this, but 2) it would also appear that the manufactures may have responded to this by producing better products and backing them up with test data. I would say that Tmoose might have the right idea, check with the manufacture of the washers that you're using and see what they have to say about the fatigue life of their particular products.
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RE: Belleville washers
RE: Belleville washers
This site has an FAQ asking you're question.
http:
Regards
desertfox
RE: Belleville washers
Thank again
RE: Belleville washers
Do the research and ensure the Belleville Washer application suits the components needed.
Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada
RE: Belleville washers
If you want to educate yourself on the application and design of disk spring components here is a link to the Schnoor handbook.
Key Bellevilles has a CD for the design and application of disk springs
http://schnorr.com/docs/Handbook.pdf
RE: Belleville washers
Roark's Equations has a section explaining Belleville washers. You can work out the stress for yourself, and analyse for fatigue. They are springs. They are under a lot of stress.
RE: Belleville washers
That said I have seen failures with them in my current job, but they are subjected to far greater forces (400 Tonne presses) and in a harsh environment (concrete products).
RE: Belleville washers
IMO, you can get a lot of cycles from them. IMO, the nasty vibrations and harmonics from machining largely contributes to the failure of the washers, not just the fatigue limits.
RE: Belleville washers
These washers flex to some extent every time the actuator operates if it is operating at or near its rated torque and only flex to the maximum extent so as to trip the torque switch if the design torque value is exceeded.
These belleville washers certainly are "reused" time and time again without ever being disassembled.
rmw
RE: Belleville washers
The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.
RE: Belleville washers
"Wildfires are dangerous, hard to control, and economically catastrophic."
Ben Loosli
RE: Belleville washers
The mfg will probably say change them every time - since they are in the business of "selling" them.
For non-critical apps - I am sure they can be re-used. But if you are building space shuttles or holding jet engines on airplanes or building race cars - I think I would use new ones every time.
RE: Belleville washers
Some moderately strict MIL spex allow reusing nylon locking nuts multiple times, or until the prevailing torque drops below some nominal value.
Some Bellevilles are designed so as to not exceed their yield strength when squashed completely flat, so would be hard to damage in that regard by tightening very hard.
RE: Belleville washers
When a Belleville spring is compressed to flat or even beyond flat, three types of stresses are usually needed to be taken into account. One is a compressive strength at the top inside diameter of the spring and the other two are tensile strength (one at the bottom large outside diameter and one at the top inside diameter of the disc). Therefore, for cyclic operation only the tensile stresses should be taken into account. However, most if not all Belleville spring manufacturing processes include a preset (scraging or set remove as it is sometimes called) process as that last process that induces favorable residual compressive stresses at the points where tensile stress governs the design. Therefore, much higher loads are able from such a spring compared to a spring that didn't include a preset process in it's manufacturing process.
RE: Belleville washers
I set up a spreadsheet using the Belleville spring equations from Roark's, and some similar equations from the SAE spring handbook. I wanted to design my own Belleville springs. As a sanity check, I pulled out my Schnorr catalogue, and I punched in their values. My spreadsheet and Schnorr were in fairly close agreement. I was happy.
Your preset would increase the maximum stress a bit, but the Schnorr washers can be compressed flat, according to my calculations. Couldn't you just punch them out of (fairly) soft metal and then heat treat them?
I wound up designing some delrin lens preloaders, and I left strict instructions to not compress them flat.
RE: Belleville washers
rmw
RE: Belleville washers
Knowing the formulations, the loads and deflections on a spring, a competent designer can easily calculate/estimate the stresses and the fatigue life. To answer a question, preliminary specific data is needed including the spring dimensions, loads and deflections. The fact that none of this is given by trudels and your post proves my point.