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Automatic Conversion of Toolbox Fasteners to Bolts

Question asked by Mikael Martinsson on Jun 24, 2014
Latest reply on Jun 26, 2014 by Mikael Martinsson

Hi.

Just explored this feature that arrived with SW2014.

In many ways it's great, but there are some questions.

 

First of all, my "old" reference for using bolt connectors is https://forum.solidworks.com/community/solidworks_simulation/simulation/blog/2009/10/15/calculating-preload-for-bolt-connectors

 

If I try with a standard M10 bolt I would, following the tip above, put in: 57,99 mm² as Ats (tensile stress area).

Preload for a reusable connection would be specified to: 0,75*Ats*Sp 

So for a 8.8 grade bolt it would be: 0,75*57,99*600 = 26095 N

 

With automatic conversion i get Ats = 69,02 mm² and a preload of 6424 N

 

According to help file: http://help.solidworks.com/2014/English/WhatsNew/c_wn2014_automatic_conversion_fasteners.htm

Tensile area is At = 0.7854 * [d - (0.9382 / n)]2

Preload is calculated: FI = 0.75 x At x 0.20 Yield Strength

 

With the "old" reference you calculate Dts = Dn - 0,938194*p

So for M10: 10-0,938194*1,5 = 8,59 mm² => Ats 8,59*8,59*pi/4 = 57,99 mm²

 

If I look up tables for M10, 57,99 is the normal value.

So why not use it in the automatic conversion?

 

And why only use 20% of yield as a pre tension force?

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