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 7075 aluminum thread pull-out force question Post Reply Forum
 Posted by: N74DV ® 03/03/2004, 02:08:29 Author Profile Mail author Edit Basically what I'd like to know it if I have a 1/2-13 steel bolt threaded into a 7075 aluminum block about 1", what force would it take to fail the threads in the aluminum and pull out the bolt? Not looking for an exact number here just an estimate.     DJ V. Mesa, AZ

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 Thread Stress, Pull-Out, Engagment Calculation and Formula Re: 7075 aluminum thread pull-out force question -- N74DV Post Reply Top of thread Forum
 Posted by: Administrator ® 03/03/2004, 10:53:49 Author Profile Mail author Edit Just so everybody knows, after I publish a few hydraulic - flow formula and calculators, I will be publishing a series on this topic "Thread Stress, Pull-Out, Engagment Calculation and Formula".Here is my work in progress, the calculators are still being worked on:   BTW, nice posts everybody! Modified by Administrator at Wed, Mar 03, 2004, 15:28:18

 Re: 7075 aluminum thread pull-out force question Re: 7075 aluminum thread pull-out force question -- N74DV Post Reply Top of thread Forum
 Posted by: BJH ® 03/03/2004, 10:30:17 Author Profile Mail author Edit Attached is some helpful info regarding thread-stripout...hope it proves helpful...Thread Engagement To Prevent Stripping Reference:Electro-Mechanical Design Handbook by Ronald A. Walsh Page 10.31:Same Materials: Material the same for both internal and external threaded partsE = 2 (Ats) / [π * Dm { ½ + (n (Pd – Dm) / sq root of 3))}] where…E = length of engagement (inches) Dm = maximum minor diameter of internal thread (inches) N = number of threads per inch Ats = tensile stress area of screw or bolt (inches squared) Pd = minimum pitch diameter of external thread (inches) ------------------------------------------------------------ Different Materials:(i.e. internal thread of lower strength than externally threaded part); Page 10.44Relative Strength: R = Ase * (Se) / Asi * (Si) where…R = relative strength factor (no units) Ase = shear area of external thread (inches squared) Asi = shear area of internal thread (inches squared) Se = tensile strength of external thread material (psi) Si = tensile strength of internal thread material (psi)If R <= 1, then length of engagement is adequate. If R > 1, then the length of engagement (G) to prevent strip-out is given as… G = E RNote: Ase = π * n * E * Dm [ ( 1/2n) + {(Pd - Dm) / sq root 3}]Asi = π * n * E * Dm [ ( 1/2n) + {(Dm - Dp) / sq root 3}] where…Dp = maximum pitch diameter of internal thread Dm = minimum major diameter of external thread

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 Re: 7075 aluminum thread pull-out force question Re: 7075 aluminum thread pull-out force question -- N74DV Post Reply Top of thread Forum
 Posted by: Cragyon ® 03/03/2004, 09:45:19 Author Profile Mail author Edit You can do the following (this is onlt an estimate), stress = load/area The area is the thread stress area, you can look in  a chart or, use the following calculator /thread_stress_area_a.htm . (Use major diameter for an external thread anbd minor diameter for an internal thread your calculations) Determine the yield strength of you weakest part (the aluminum). Then,   yield stress = [load maximum]/(thread stress area * number of threads of engagement) or, load maximum = [yield stress] * [thread stress area * number of threads of engagement)     Modified by Cragyon at Wed, Mar 03, 2004, 10:46:03

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