Questions tagged [stresses]

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4
votes
1answer
4k views

Why is the point of failure load lower than the peak load? [closed]

In a tensile test the peak load was 69kN, but the point of failure load was 60kN. Why is it lower?
15
votes
2answers
11k views

Why do we even use engineering stress?

Surprisingly this hasn't been asked before, so I must be missing something simple. We use engineering stress and engineering strain in this eq. Stress = (Young's modulus) × (strain). This eq. is ...
8
votes
2answers
8k views

Interpretation of shear flow/shear center of L-profile

I have calculated the shear flows and center of an L shaped profile. I assume they are correctly calculated (I followed the same steps as during the lectures for an I shaped profile). However, I have ...
7
votes
4answers
2k views

Why do stress concentrations really occur?

From doing some research I've learned that internal stresses inside an object can "concentrate" on sharp edges, as shown in the above picture. For that reason we often make fillets so that the change ...
4
votes
1answer
865 views

Why is the Stress vs strain diagram preferable to the Load vs displacement diagram?

I’m really unsure what is the difference between stress vs. strain and load vs displacement graphs and why stress-strain is better. I know that the units are different: stress is in MPa and the load ...
3
votes
2answers
139 views

How exactly do forces transfer in different directions?

If we imagine the load being placed at the top of the below triangle, I realise that the downwards force is transferred into one which goes in a 'south east' and 'south west' direction down to the end ...
23
votes
5answers
5k views

Why exactly does a washer help distribute the stress around a bolt?

Usually the reason for having a washer under a bolt head is stated to be that it helps to evenly distribute the stress to the clamped material surface. But why is this? I would understand if the ...
3
votes
2answers
8k views

Properties of an hexagonal shape vs round tube shape

In a bike frame build, are there any differences between hexagonal cross-section tube instead of the typical round tubes? Assuming that both are made from the same aluminium alloy and have the same ...
4
votes
4answers
3k views

Calculating maximum internal pressure from maximum rated external pressure?

Is there a calculation / rule of thumb that can determine a containers rough maximum negative pressure (vacuum) from it's rated internal pressure (assuming a single layer construction so there is no ...
2
votes
4answers
8k views

What is the difference between tau = VQ/It and tau = V/A?

What is the difference between the formulas $\tau = VQ/It$ and $\tau = V/A$ for finding shear stress due to transverse loading? I understand that the use of first moment of area, is the only reason ...
2
votes
1answer
137 views

How to calculate residual strength of a corroded structure from their stress values?

Currently, I have an actual entire corroded bridge model in the FEM analysis in Abaqus I want to estimate the residual strength of this bridge due to corrosion from the output results in the Abaqus, I ...
1
vote
1answer
308 views

Shear Stress Formula

Could anyone tell me what the variables in this formula are? $$\tau=\frac{S\;a\; \bar{v}}{I\; t}$$ I believe it is used for shear stress and that $I$ is moment of inertia but unsure on the other ...
0
votes
2answers
270 views

Thick walled cylinder theory - Stress/strain in ballooned out tube

I want to work out how much I can expand a piece of rubber tubing before it ruptures. The wall is 0.75mm and the ID 5mm. Hence I am working out the stress/strain from thick-walled cylinder theory ...
0
votes
2answers
837 views

How to calculate external pressure resistance in spheres and cylinders?

Although I have seen a lot of literature online about how internal pressure resistance is calculated (i.e the pressure in a gas tank) I haven't found anything about the opposite scenario (i.e the ...