Answer: Factor of Safety for Bolt Shear & Tensile Stress

In summary, the bolt shown in the angled joint has an ultimate tensile strength of 500 MPa and a shear strength of 300 MPa with a diameter of 8 mm. The factor of safety in operation can be determined by considering the shear and tensile stress acting together and using the experimental results to determine the relationship between them. A linear relationship between shear stress and tensile stress may not always be accurate and the eurocode suggests a parabolic or elliptical relationship.
  • #1
maali5
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Homework Statement



The material for the bolt shown in the angled joint above has an ultimate tensile strength of 500 MPa and a shear strength of 300 MPa. The diameter of the bolt is 8 mm. Determine the factor of safety in operation.


Homework Equations





The Attempt at a Solution



Shear stress= 5,5 . cos 60 (pi . 8 . 2/4)

= 0.0547kn

= 54.70 mPA



Shear Fs= 300/ 54.7 = 5.48



b) Tensile Stress = 5,5 . sin 60 (pi . 8. 2.4) = 94. 7 Mpa


Tensile Fs = 500/94.7 5.27



Is this correct?
 

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  • #2
You have considered tension and shear independently, but actually they are acting together. To solve, you need to know the shear/tension strength characteristic. The graph of shear stress/ ult shear stress versus tensile stress/ ult tensile stress is sometimes assumed linear, but that is a 'safe' assumption. The experimental results were used to determine at least the relationship for the eurocode and is approximately parabolic or elliptical (I can't remember which without looking it up in ec3)
 

1. What is factor of safety for bolt shear and tensile stress?

The factor of safety for bolt shear and tensile stress is a measure of how much stronger a bolt is compared to the maximum load it will experience. It is calculated by dividing the ultimate strength of the bolt by the maximum load it will experience.

2. Why is factor of safety important for bolts?

Factor of safety is important for bolts because it ensures that the bolt can withstand the expected load without failing. It also takes into account any potential variations in material strength, environmental factors, and other uncertainties.

3. How is factor of safety calculated for bolt shear and tensile stress?

The factor of safety is calculated by dividing the ultimate strength of the bolt by the maximum load it will experience. The ultimate strength can be found in engineering handbooks or by conducting tests. The maximum load can be determined by analyzing the forces acting on the bolt in the specific application.

4. What is a safe factor of safety for bolt shear and tensile stress?

The safe factor of safety for bolt shear and tensile stress varies depending on the application and industry. Generally, a factor of safety of 2 or higher is considered safe, meaning the bolt is at least twice as strong as the maximum load it will experience.

5. How does factor of safety affect the strength of a bolt?

The factor of safety directly affects the strength of a bolt. A higher factor of safety means the bolt is stronger and can withstand greater loads without failing. A lower factor of safety means the bolt is weaker and may be more prone to failure. Therefore, it is important to choose a suitable factor of safety for the specific application to ensure the strength and reliability of the bolt.

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