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Disc Springs are conically-shaped precision components designed to be axially loaded. Disc Springs are often incorrectly referred to as belleville disc springs, belleville springs, belleville washers or simply conical washers. Disc Springs are unique and differ from other types of springs in that the force/deflection curves of Disc Springs are consistent and repeatable, and the minimum fatigue life can be reliably determined (per the standardized calculations of DIN EN (formerly DIN )). Disc Springs can be statically loaded either continuously or intermittently, or dynamically subjected to continuous load cycling. They can be used singly or in multiples stacked parallel, in series or in a combination thereof to achieve the desired force-deflection characteristic.
Disc Springs are preferred over other types of springs (such as coil springs, belleville washers, belleville springs and conical washers) when used in critical applications such as safety valves, clutch & brake mechanisms for elevators, and supports for industrial pipe systems due to their predictability, reliability and unparalleled fatigue life.
The advantages of Disc Springs compared to other types of springs include the following:
SPIROL offers the full range of DIN EN (formerly DIN ) Group 1 and 2 Disc Springs in Series A, B, and C. In addition to the DIN specified sizes, SPIROL stocks its own standard size range in outside diameters from 8mm to 200mm in order to meet the diverse needs of its customers. SPIROL standard Disc Springs meet all material, dimensional tolerance, and quality specifications as laid out in DIN EN (formerly DIN ) but in diameter and thickness combinations that are not included in the DIN standard.
SPIROL also offers a line of austenitic Stainless Steel Disc Springs.
SPIROL supplies single Disc Springs, as well as Pre-stacked Disc Springs in custom configurations, packaged in shrink wrap with a perforated tab for easy of assembly.
Select from our expansive standard offering, or take advantage of our complimentary Application Engineering support and allow us to work with you to help determine the most appropriate Disc Spring or Disc Spring Stack for your specific application and assembly needs!
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Disk Spring for thermal effects compensation
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(Aerospace)
(OP)
15 Mar 21 05:31Hello,I have an Ultem Flange that has to be connected to a Titanium container with a screw made of steel.I am presenting only a portion of the bolted joint for simplification:First of all I have to point out that my preload is limited by the ULTEM and hence it's only preloaded to N.I was looking for a solution to 2 problems:1. Preload decrease due to exposure to cold temperature (del_T=-25 celcius degrees).2. Preload decrease due to the (unknown) ULTEM creep in compression.As a result I thought that adding a "spring" element with a moderate stiffness may compensate the deflections with only quite small load decrease. So I decided (as a result of limited space) to try to use (for the first time) Disc Spring for this purpose, as described in the picture above.I have some questions regarding this design:1. Is there a problem of stacking 10 Disks in parallel?I couldn't find an adequate standard Disk Spring (for a #10 bolt) that may give me such forces.It's important to point out that I have a limitation of maximum outer diameter (of the Disk Spring) of 12 mm that isn't seen in the picture above, and that's why I can't use a massive disk spring.2. Is there another elegant solution I didn't think of and that is preferable?3. Just to make sure I have no mistake - is the ULTEM surface will have a reaction force that is equal to the bolt axial load (that is equal to the equivalent spring force exerted by the induced deflection)? I read somewhere that as a result of internal friction between the disks the ULTEM experiences a lower force than the exerted force (of the bolt), but when I drew a Force Body Diagram I found out that for an equilibrium the reaction in the ULTEM surface has to be equal to the bolt axial force.I am looking forward to your good advice!Have a nice day
(Aerospace)
15 Mar 21 06:10I think they'd be more effective if every other washer was flipped; that way each washer is pushing against something at it apex and at its periphery
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm
(Mechanical)
15 Mar 21 08:44HiI know nothing about Ultem however you need to take account of the stiffness of the materials you are clamping and the bolt / disc spring stiffness.Putting it bluntly if the disc spring stiffness is much greater than the stiffness of the Ultem then all that will happen is the disc springs will not compress but instead will just embed themselves into the Ultem and you will not achieve the preload you are looking for, however without the modulus of elasticity of the Ultem and properties of the other materials present it&#;s impossible to tell.If the materials being clamped have similar properties to the bolt/ disc washers then yes the load in the bolt is what the Ultem would experience.Another way to look at what I am saying is imagine your joint as you have shown it but instead of Ultem replace it with say putty and think about what happens when I tighten the joint.Further more you also need the expansion coefficients of the materials to do any kind of analysis.
&#;Do not worry about your problems with mathematics, I assure you mine are far greater.&#; Albert Einstein
(Aerospace)
(OP)
15 Mar 21 18:46Hey IRstuff
I think that if I flip every other washer (serial connection) the equivalent stiffness will decrease. I calculated that for achieving N preload I need at least 8 parallel disc springs (each one's force at 75% deflection is 300 N).
(Aerospace)
(OP)
15 Mar 21 19:00Hey desertfoxI attached the Data Sheet of Ultem .The N was determined after calculating which load can be sustained for prolonged durations without yielding and it's actually around 30Mpa. On the other hand a creep can't be avoided.I used in my calculations the stiffness and Coefficient of thermal expansions of the joint components, and found out that the expected reduction in preload due to temperature change alone is about 10%.I never used disc springs in my design, and I think that my main question is if the application is correct. It seems to me that stacking 10 disc springs in parallel is exaggerated and may bring some problems I don't think of.
[Post Deleted](Materials)
15 Mar 21 19:30There are losses in efficiency when you go to tall stacks, We used to use alternating pairs.Yes it makes the stack taller, but it works smoother.Just remember that this is a spring, there will be a force vs height relationship that you need to watch.The washer on the Ultem is critical, it will need to be extra thick and strong, it cannot have any deflection.
= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed
(Mechanical)
15 Mar 21 20:24Hi eli28Reading your last post if you haven&#;t included the disc springs in your original calculations for the joint under going thermal change then the calculation isn&#;t valid because the stiffness of the bolt will change because of its increased length when you add the disc springs and the springs themselves will contract under reduced temperature. Can you post your calculations in here ?
&#;Do not worry about your problems with mathematics, I assure you mine are far greater.&#; Albert Einstein
(Mechanical)
If you are looking for more details, kindly visit beveled washers.
15 Mar 21 20:31 eli28, you might check with, you might check with Solon Mfg . They supply disc springs and good advice.Regards,Mike
The problem with sloppy work is that the supply FAR EXCEEDS the demand
(Mechanical)
15 Mar 21 21:12"Is there a problem of stacking 10 Disks in parallel?"Fast acting, consistent pull force Machine tool automatic tool holders often use stacked good quality bellevilles and magic grease.0:31 here -A few pictures in this brochure-
(Aerospace)
16 Mar 21 16:41Quote:
I think that if I flip every other washer (serial connection) the equivalent stiffness will decrease.
Sorry, no. A stack of Bellevilles all facing the same direction makes most of them ineffectual; only the one washer with its circumference touching the destination surface is really doing anything.
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm
(Chemical)
16 Mar 21 19:48If they are all facing the same direction each washer will add to the the force required to cause a unit of deflection (plus additional friction forces between washers due to shear). So, a very stiff spring, with a lot of damping.
If the washers alternate directions, each washer will add to deflection caused by a unit of applied force. So, the spring becomes less stiff.
(Mechanical)
17 Mar 21 12:16"A stack of Bellevilles all facing the same direction makes most of them ineffectual; only the one washer with its circumference touching the destination surface is really doing anything."Springs in series vs springs in parallel.
(Aerospace)
(OP)
20 Mar 21 12:06 desertfoxHey againIt took me a while to reply, but I attached a detailed document with photos and explanations.After I added disk springs I got a reduction of 65 N due to temperature decrease.The calculation without the Spring Disks gave a reduction of around 150 N.
(Mechanical)
20 Mar 21 17:24Hi eli28Thanks for the detailed analysis, if I understand it correctly you are setting the bolt preload at N which is the maximum that the Ultem material can take before yielding.Now with that preload you are saying the joint is cooled and so the bolt preload also reduces and with the disc springs fitted you have calculated that the preload loss is 67.5N but what I cannot see in the calculation is what the external load on the joint is liable to be? Now the external load is important because the relative stiffnesses of the bolt and joint materials will dictate how much of the external load each component will see, so if you preload the Ultem to its maximum it can take, then any amount of the external load imposed on the joint materials will cause the Ultem material to yield and your joint will be lost.
&#;Do not worry about your problems with mathematics, I assure you mine are far greater.&#; Albert Einstein
(Aerospace)
(OP)
20 Mar 21 18:06Hey,
I am going to give you an additional information that was achieved prior to dealing with the thermal effects.
I started by FBD for calculating the required force (with safety of factor) the bolted joint should bear - N per bolt.
I checked that the ULTEM stress isn't above 40 Mpa (its yield is around 100 Mpa) when using N preload.
The limitation of 40 Mpa is for avoiding significant creep.
I have a separate analysis (in my work) in which I can see that after adding the external load, the part of the load taken by the members (by the way, surprisingly it's around 80% of the total external load) is OK and the ULTEM is far enough from yielding (around 60 Mpa).
Now, after making sure that these criteria are met - I moved forward to thinking of failure modes like thermal effects etc.
(Mechanical)
20 Mar 21 19:49Hi eli28Well it seems to me you have it well sorted, obviously the 80% of the external load isn&#;t going to separate the joint or yield the Ultem but was is the magnitude of the external load?
&#;Do not worry about your problems with mathematics, I assure you mine are far greater.&#; Albert Einstein
(Electrical)
20 Mar 21 21:35You've put a lot of effort into this joint. Might I suggest one of these to prove the results all over all temperatures.They aren't cheap but they are accurate. They can be used to perfectly tighten fasteners regardless of any and all rotary friction aspects as they measure only the bolt elongation and stress. You can tighten fasteners to the exact torque regardless of compression of the bolted materials or thread lubricants. Furthermore they allow you to come back and see if it has changed which seems would answer your question about the Ultem creep. With the optional temp sensor you could monitor the joint across all expected temperatures. You can map how fast and how serious the creep might be. There are a couple of companies that sell these instruments though they seem to all be on the same price train together.. I see these as the oscilloscope of fastener users. The option exists of renting one or hiring a service to measure for you too.
Keith Cress
kcress - http://www.flaminsystems.com
(Aerospace)
(OP)
21 Mar 21 03:56desertfox, I am not sure I understood your last question :)
(Aerospace)
(OP)
21 Mar 21 04:00itsmoked thank you very much!
I didn't know about this kind of instrument.
Do you have any experience with this specific company? Which company is the leading one in this field?
(Mechanical)
21 Mar 21 05:44Hi eli28What is the value or magnitude of the external force, you stated that when you added the external force you calculated that 80% was taken or seen by the joint materials, however I couldn&#;t see a value for it.
&#;Do not worry about your problems with mathematics, I assure you mine are far greater.&#; Albert Einstein
(Electrical)
21 Mar 21 10:17Hi eli28;I was working in the little town of Scotts Valley in the Silicon Valley outskirts. There was a company across the street from mine called StressTel. As far as I know they were the inventors of the stress based bolt torquing hand-tools. It seems a decade or so ago they where bought by another company Krautkramer then Krautkramer and all its acquisitions were slurped up by Waygate Technologies. Waygate just looks like a tech suck-up company.Meanwhile. The company who's brochure I linked above 'Dakota Ultrasonics' has sprung up about a sling-shot's distance from where StressTel was but is in much nicer digs. I suspect this is a case of bought-out employees rolling an advanced and updated version of whatever StressTel was selling and going back in business. Personally I'd go with Dakota as the current tech leader in the subject matter and also the company selling the product is the company actually building the product so you can contact The People rather than a company who buys the product from someone else.Besides. My dog liked walking around their building - their lawn and the deer that were frequently standing on it.
Keith Cress
kcress - http://www.flaminsystems.com
(Aerospace)
(OP)
21 Mar 21 16:47desertfox, the external load for each bolt is estimated to be N.
(Aerospace)
(OP)
21 Mar 21 16:51Thanks (itsmoked) for replying and explaining your choice :)
(Mechanical)
22 Mar 21 07:48Hi eli28Is the external load compressive on the clamped joint or tensile?My only other comment depending how you preload the screw is that if you use a ordinary torque wrench then the tolerance for torque error is +/- 25% however if you use a device like itsmoked suggested the error should be a lot less.I mention the error tolerance because I think 25% could cause the Ultem material to yield if it goes in the wrong direction.
&#;Do not worry about your problems with mathematics, I assure you mine are far greater.&#; Albert Einstein
(Aerospace)
(OP)
22 Mar 21 18:26Hey, the loads are in both directions.
It means the joint experiences tensile and compressive force.
About the tolerance in preload when using the traditional torque meter - I am also worried about it and I am sure the suggested solution given above is excellent.
Now is the difficult part - convincing the project managers to buy it.
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