g-acceleration

[flyforever85]

I have an component made of aluminum, density is 0.0002538 lb sec2/in4 to keep units consistent with E in psi and size in in. I have to test this component in different crash conditions up to 12g

I checked abaqus manual,it say to insert the acceleration which is 386.09 in/sec2 (1 g) x 12 ~ 4633 in/sec2

I calculated the force the component is subject to as F=mxa = 0.0542 lb sec2/in x 4633 in/sec2 ~ 251.11 lbf

With this acceleration I barely see any stress within the component, we are talking about 500 psi! Yes the component is pretty bulky.

Am I making any mistake?

Thanks

 

[FEA way]

Which type of load did you choose ? Body force, gravity (from Load group) or acceleration (from BC group) ? You should choose gravity and enter your value of 4633 there.

 

[flyforever85]

THat's what I did. The component is a gear box and my colleague told me to insert also the weights of all the component stored inside the gearbox and add gravity to them as well. I have to look out to attach a mass point

 

[FEA way]

Yes, to include the parts that you don’t want to mesh you should add their masses attached to point connected with the rest of the geometry.

When it comes to the reason why stresses are so low we need more information to find out what’s wrong. Can you share some pictures here ? It would be good to see how your model looks like, where are BCs applied, how it is meshed and so on. Please also attach results and provide some details about the analysis itself (step settings). The more information the better and easier to help.

 

[flyforever85]

I wish I could but I can't since it's a design that belongs to the company. I just wanted to be sure the idea behind the modelling is correct.

 

[FEA way]

Ok, pictures may not be necessary but can you say more about the analysis settings ? Especially how your model is loaded and constrained.

For now I can only suggest some general checks that you can try to verify the correctness of your analysis:
- first of all check all units including material properties and model dimensions
- make sure that there’s no hourglassing or volumetric locking in your model
- check boundary conditions
- try different type of elements
- read all warnings printed in the analysis files
- check contacts and ties, use eigenfrequency extraction analysis if necessary