convert Proof loads to Safe Working Loads. 1

[fasterfasteners]

Hi guys,

I have been designing a new type of nut that folds around a thread as opposed to being wound on from the end, The fastener is being manufactured out of Nylon 6/6.

We have recently completed some tensile tests on the load strength and some proof load tests for deformation under load.

The tensile test results for the nuts were a mean failure of 659kgs or 1452 pounds (50 tests) and proof loading test were a pass at 510kgs or 1124 pounds (10 tests, fasteners were inspected and measured under a macro scope to determine deformation - probably not particularly relevant to Nylon).

The test methodology was to AS/NZ 4291.2:1995 or ISO 898.1 (note that this standard relates to mechanical property of steel nuts). I realize that this particular standard is not really relevant to Nylon nuts nor does the room temperature component of this test reflect the individual characteristics of nylon at differing temperatures.

However as there seems to be no standard for nylon nuts; we are using this standard, to produce statistical data.

So my question is " how can I relate the data from either the tensile tests or the proof load tests to give a safe working load?"

Thanks

Jason

 

[CoryPad]

I think the data you have generated is good for a single application of a force. So, you could use the "Proof Load" you calculated plus a safety factor.

However, most fasteners are preloaded, so you need to determine deformation and load carrying capacity over time for these parts.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[dimjim]

You will also need some data as to different
humidity levels.

 

[fasterfasteners]

thanks guys, thats got me sorted

Jason
fasterfasteners.com