Threaded fastener calculations using ECSS-E-HB-32-23A 2

[oreillsi]

Hi all,

On a project I'm working on I've been instructed that our first approach to determining the MoS values on the fasteners in a design wasn't correct and told to use the ECSS document on threaded fasteners (ECSS-E-HB-32-23A). I'm trying to implement the method in a spreadsheet now but it's just not really "clicking" with me somehow, has anyone got any experience in using this handbook for fastener/ joint design and analysis? The document can be downloaded from this link here:

https://www.google.ie/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CCwQFjAA&url=http://

http://www.ecss.nl/forums/ecss/disp...5Svt8mU_DRhZBUXZg&sig2=d6NwJyucdIrxkZHRXZ-EOg

Some (not many) of the chapters in the document have sample calculations in them which really helps to demonstrate the method but for the rest it just doesn't seem too clear, does anyone know perhaps where i might be able to read some previous examples of this method being used? Maybe a report of a previous design of a spacecraft/spacecraft's payload which used this standard for its joint analysis??

Any help would be greatly appreciated

 

[CoryPad]

I have reviewed this handbook a few times over the years, I don't see anything out of the ordinary. It is similar to other methods, e.g. VDI 2230, Bickford, Fisher...

Anything specifically troubling you?

 

[oreillsi]

Thanks for the reply CoryPad.

I think the part which I'm struggling with is the fact that so many of the calculations in the document rely on input data such as prevailing torque, allowable applied torque, friction coefficients for the threads and underhead contact area and other such bits of information yet the document only provides these data for a few specific applications. For example the maximum and minimum prevailing torque is only provided for fasteners which are M5, M6 or M8 in size and even then much of the data is missing (also the designs I'm working on involve the use of M3 and M4 screws for which there is no data at all given).

From searching online I've found a few different sources which provide some data for different fastener sizes/types but most of the time the figures from the various sources do not agree with each other. I think I would have much more faith in the calculations if I could rely on the input data I'm using. Is there a source of data (preferably an online one) for fasteners which I don't know about and is generally accepted by industry? If so I'd love it someone could point me in the direction of this source please!

 

[CoryPad]

Oh, I see the problem. There really is no good source for these data, physical testing of your parts is the standard method. You can refer to industry consensus standards for some prevailing torque values (e.g. ISO 2320 or IFI 100/107) and supplier data sheets for friction coefficient (e.g. Magni, NOF, Dorken). Usually these values are specified in product standards or on product drawings. Check faq725-600 for good information sources.

 

[oreillsi]

That's great thanks for replying again! I'll look through the thread you linked and also at the examples of sources you gave. It's disappointing although not very surprising that there isn't a more regulated way of obtaining the data. Anyway, thanks again.