Bolt Thread Pullout (failure) in alu 6063-T6

In summary: Aluminium has a yield strength of ~205 MPa (metric tons), so the allowable stress is 6.8*205=12,700 MPa. The bolts will be able to withstand a load of up to 12,700 MPa.In summary, the bolts will be able to withstand a load of 350 kg with no issue. The bolt material is 6063-T6, the bolt diameter is M12x50 DIN 912, and the thread lubrication is not specified. The bolt will only be installed once, and there is no mention of helicoil. The thread height should be not less than 2d of the screw, and the screws will work inside the aluminium plate with no issue.
  • #1
Yevhenii
7
0
TL;DR Summary
Thread in alu 6063-T6
I need advice how to calculate thread pull out in aluminium 6063-T6.
12 bolts screwed into an aluminium plate (thread depth 25 mm) must withstand a load of 350 kg.

Thanks in advance
 
Engineering news on Phys.org
  • #2
What is the bolt material? What bolt diameter? Will the bolts gall in 6063-T2?
What thread lubrication? How many times will it be removed and replaced?
You might use a long stainless steel thread insert such as recoil or helicoil. That will increase the effective thread diameter in the 6063-T2.
 
  • #3
Will be screwed only one time. I want to know how it will work without helicoil threads. Bolt diameter M12x50 DIN 912, will be installed without grease.
I calculated before - the shear stresses in the bolt and aluminum plate are less than the maximum allowable stresses.
Also I heard, that if you want to install steel screws inside soft materials (aluminium) thread height should be not less than 2d of screw.
How I can make sure that these screws will work inside alu plate?
Thanks
 
  • #4
If you tighten a fastener by turning the nut, then the fastener is called a bolt. If you turn the head and shank of the fastener, then it is called a screw. So you are using screws to attach the plate.

Yevhenii said:
Also I heard, that if you want to install steel screws inside soft materials (aluminium) thread height should be not less than 2d of screw.
That should be the length of the engaged thread, not the height which better refers to the thread profile.

Yevhenii said:
How I can make sure that these screws will work inside alu plate?
As the screw is turned and tightened, imperfections in the thread will deform and damage the threaded aluminium. A more reliable way would be to thread a stud into the aluminium, without axial load, then clamp the plate in place with an external nut. The thread in the aluminium should have a high profile, so it should be coarse. The nut end of the stud should have a fine thread.

A coarse thread helicoil, with a screw will not be as strong as the coarse stud with fine nut. A coarse screw threaded into aluminium will require a higher torque to reach the same tension as a fine nut on a stud.
 
  • #5
Would probably be fine. You are correct that the minimum thread engagement should be at least 25mm here.

The general formula for determining allowable stress is P=S*A, with P=load, S=tensile strength of Al, and A=tensile stress area.

For an internal thread this area is defined as:
1614958991470.png

with n=threads per inch, Le=length of engagement, Dsmin=minimum major diameter of the external thread, Enmax=maximum pitch diameter of internal thread.

350kg is a mass, not a load. Presumably this is pure tension with no shock loading, thermal loading, etc, so your load would be (9.81*350) N; divide by 12 to find your load per bolt and make sure that's less than the allowable load by looking up the yield strength of Al-6063, the necessary internal & external thread dimensions, and using the above equations. I'll leave it up to you to confirm.

This information can be found in Machinery's Handbook.
 
  • Like
Likes Yevhenii

FAQ: Bolt Thread Pullout (failure) in alu 6063-T6

What is bolt thread pullout failure in alu 6063-T6?

Bolt thread pullout failure in alu 6063-T6 refers to the failure of a bolted joint where the threads of the bolt strip or pull out of the material, resulting in a loss of clamping force and potential structural failure.

What causes bolt thread pullout failure in alu 6063-T6?

The main cause of bolt thread pullout failure in alu 6063-T6 is the mismatch of material strength between the bolt and the aluminum material. The aluminum material is relatively soft compared to the bolt, causing the threads to strip under high loads or vibrations.

How can bolt thread pullout failure in alu 6063-T6 be prevented?

To prevent bolt thread pullout failure in alu 6063-T6, it is important to use bolts with the appropriate strength for the material being used. Additionally, using proper torque values and thread lubricants can help distribute the load evenly and reduce the risk of thread stripping.

What are the signs of bolt thread pullout failure in alu 6063-T6?

The most common signs of bolt thread pullout failure in alu 6063-T6 include loosening of the bolt, visible deformation or damage to the threads, and a decrease in clamping force. In severe cases, the bolt may completely strip out of the material.

Can bolt thread pullout failure in alu 6063-T6 be repaired?

In most cases, bolt thread pullout failure in alu 6063-T6 cannot be repaired. The best course of action is to replace the damaged bolt with a stronger one or use alternative methods of fastening, such as welding or adhesive bonding. It is important to properly address any signs of thread pullout failure to prevent further damage or potential safety hazards.

Back
Top