Pull Out Force Calculation in Aluminum

[williedawg]

Have done a lot of reading on the 'net trying to find a definitive answer for calculating the Pull Out Force of a screw in Aluminum.

Here are the knowns

5/16-18 SHCS Class 2 Gr 8

6061 Aluminum plate 3/4" thick (40ksi ?)

Length of engagement = 5/8"

On another site (engineersedge.com) there is reference to a formula for calculating Stress Area of a given Screw & corresponding female thread that makes use of the data from Machinery's Handbook.

http://www.engineersedge.com/thread_strength/thread_bolt_stress.htm

The referenced formula is also set up for direct user input by clicking on the link at the bottom of that page.

Going through the calculations, I arrived at .4663sqin for the Stress Area and a Pull-Out of 18,651# (using 40ksi)

The online calculator gives the same numbers.

The 18k + number seems quite large,...is this a valid number?
Even though this isn't a hanging load, should a "safety factor" be used with this? 50% rating?

What's the general consensus on this type of application?

Thanks for any input

Willie

 

[metman]

40ksi shear strength seems a little high for 6061 but I could be wrong. Don't have data handy. Someone will answer this.

A conservative value for shear strength is 0.577xUTS.

And yes use a factor of safety depending on the application. How important is it for it not to fail? Also you should consider fatigue if it is to have repeated loading/unloading and for Aluminum there is no endurance limit.

 

[CoryPad]

Shear strength for 6061-T6 is 30 ksi.

Your force would be ~ 15 000 pounds.