Tensile strain / safety factors

Sep 29, 2021

giraffasaurusrex

Homework Statement: Hi all.. I would really appreciate any help anyone can give me! I have tried to solve the following and although I understand a) (I think!), I am really unsure between the two possible formulas to use for b), and my answer for c) just seems wrong..! If I am making an obvious mistake I'd love to know..

Thanks in advance!

A load of 50 kN is applied to the tensile member shown in fig. 3. The axis of the rivet is at 30° to the line of action of the load F.

a) calculate the tensile and shear stresses in a 20mm diameter rivet.
b) calculate the tensile strain in a 20mm diameter rivet.
c) if the ultimate tensile stress of the rivet material is 350MPa and it's modulus of elasticity is 150GPa, find the safety factor for the above rivet in operation.

Relevant Equations: Stress=force/area
Strain=Lx/Lo
Elasticity=stress/strain
(Area=πd sq/4)

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Sep 29, 2021

Chestermiller

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Your normal and tangential components of force look OK. What is the shear stress and tensile stress in the bolt?

Sep 29, 2021

giraffasaurusrex

Oh no! Thank you, yes I see the mistake now - I want to say I was focusing on B and C but that would be shameless self promotion (:
This would be the F/A I forgot wouldn't it..? Thank you so much!

2. How is tensile strain calculated?

Tensile strain is calculated by dividing the change in length of an object by its original length. This is then multiplied by 100 to express it as a percentage. The formula for tensile strain is: ε = (ΔL / L) x 100%, where ε is the strain, ΔL is the change in length, and L is the original length.

4. How do safety factors affect the design of structures?

Safety factors play a crucial role in the design of structures, as they help engineers determine the appropriate materials and dimensions to use in order to ensure the safety and stability of the structure. A higher safety factor means that the structure is more resistant to failure, but it also means that more material may be needed, which can increase cost and weight.

5. What is the recommended safety factor for structures?

The recommended safety factor for structures can vary depending on the type of structure and the materials used. Generally, a safety factor of 2-3 is considered standard for most structures. However, for structures that are subject to high loads or critical applications, a higher safety factor may be necessary.