# Shear failure in threaded fasteners

• krithika
In summary: I am not sure what you are looking for. Can you elaborate?In summary, the bolt will not fail due to shear stress if the length of thread engagement of the bolt with nut is equal to the diameter of the bolt.
krithika
Hi
How can i derive an equation to prove that a bolt won't fail due to shear stress if the length of thread engagement of the bolt with nut is equal to the diameter of the bolt.

I got a formula, but i don't know whether it is useful in this case.

A_s,e = pi*n*L_e*K_nmax*[1/2n + 1/sqrt3*(E_s,min-K_nmax)]
where
L_e=Length of engagement
K_nmax=maximum inner diameter of nut
E_s,min=minimum pitch diameter of bolt

thanks

Are you talking shear stresses in the threads or in the bolt shank? You are listing the shear area for failure of the threads.

The equation you state is the calculation of the shear area of an external threaded fastener. It is in a slightly different form than what I am used to, but it is fine the way you have it. The easy thing about your question is that you are putting the constraint that the engagement is equal to 1D. That is the way most shear area tables for fasteners is made. The tables list shear area for threads when Le = 1D. Tables like this are available in texts like Bickford and others on fastener strength.

Thanks for your reply. I think the formula what is stated (FOR Shear area) is of no use. What I'm looking for is a derivation or a formula which can say that the bolt won't fail due to shear stress, if Length of engagement between = the dia of the bolt. But unfortunately i couldn't find it anywhere :(.

krithika said:
What I'm looking for is a derivation or a formula which can say that the bolt won't fail due to shear stress, if Length of engagement between = the dia of the bolt. But unfortunately i couldn't find it anywhere :(.

What does it mean if the bolt does not fail by shear in the threads?

Need to take into account the material fastner is made out of, nylon, mild steel, galvanised, zinc coated, high tensile, stainless steel.
Being able to shear will depend on how maluble the material is

To make things simple.
the length of engagement of bolt = diameter of the bolt.

But i don't know how to prove that it won't fail. I couldn't find a concrete material for this.
I am a kid in this field. So i need your advice.

The minimum recommended length of engagement is 0.75 to 1 times the bolt major diameter for threading into steel and other materials of comparable hardness; and 1 to 1.5 times the bolt major diameter for threading into brass, cast iron, and aluminum. These lengths of engagement specified are for full threads engaged, not overall bolt length.

## 1. What is shear failure in threaded fasteners?

Shear failure in threaded fasteners occurs when the applied load is parallel to the axis of the fastener and causes the threads to strip or break, resulting in a loss of clamping force and potential joint failure.

## 2. What are the common causes of shear failure in threaded fasteners?

Some common causes of shear failure in threaded fasteners include over-tightening, inadequate thread engagement, and poor material quality.

## 3. How can shear failure in threaded fasteners be prevented?

To prevent shear failure, it is important to use the correct torque and thread engagement for the specific fastener and application. Using high-quality materials and properly installing the fastener can also help prevent shear failure.

## 4. How does shear strength affect the performance of threaded fasteners?

Shear strength is an important factor in the performance of threaded fasteners as it determines the maximum load the fastener can withstand before shear failure occurs. Higher shear strength fasteners are able to withstand greater loads and are less likely to fail.

## 5. What are some signs of shear failure in threaded fasteners?

Some signs of shear failure in threaded fasteners include loose or stripped threads, reduced clamping force, and visible cracks or deformation in the fastener. It is important to regularly inspect fasteners for signs of shear failure to prevent potential joint failure.

• Engineering and Comp Sci Homework Help
Replies
3
Views
1K
• Mechanical Engineering
Replies
3
Views
562
• Engineering and Comp Sci Homework Help
Replies
9
Views
3K
• Mechanical Engineering
Replies
6
Views
1K
• Mechanical Engineering
Replies
15
Views
35K
• Engineering and Comp Sci Homework Help
Replies
1
Views
2K
• Engineering and Comp Sci Homework Help
Replies
48
Views
9K
• Mechanical Engineering
Replies
9
Views
3K
• Introductory Physics Homework Help
Replies
13
Views
9K
• Engineering and Comp Sci Homework Help
Replies
1
Views
20K