7075 aluminum thread pull-out force question
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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: /thread_strength/thread_bolt_stress.htm   BTW, nice posts everybody! Modified by Administrator at Wed, Mar 03, 2004, 15:28:18

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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: 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 parts E = 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 10.44 Relative 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 R Note: 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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