Impulse load assessment

[pegus]

Good day,

I wonder how impulse loads are considered during a mechanical validation of a structure.
In this case, we need to design a structure based on some impulse loads that we received from our peers. These loads are high from .0001 seconds to .01 seconds after this time they got to zero. I know that considering these loads as statically will lead into really conservative designs. But I wonder how these loads should be considered.
A peer of my work mentioned to perform transient structural analysis in a FEA software (ANSYS), this with the intention of consider inertia and damping effects of the structure. Does this means that he just need to input these impulse loads into this software to obtain the real stresses? or do we need to make another consideration to these loads before consider them into the analysis?

Thanks in advance,

P.P.

 

[rb1957]

LS Dyna analysis ?

Its not That easy … several parameters (high strain rates) are not readily available (depending on material) and need testing to develop them.

You could also consider testing … a key question we get these days from certification folks is "what is the test validation of your FEM ?" … ie FEA without close test experience isn't worth very much.

another day in paradise, or is paradise one day closer ?

 

[pegus]

Thanks for the response!

Is there any reference sources you can share? I would like to learn more about it.

We are basically going to analyze a rectangular flat wall.

I was researching about the ansys tools, and I found that an explicit analysis suits better for forces acting in less of 1 second. But we need a detailed material model that you mention, I saw that ansys offers some material models for this kind of analysis. Does this sounds as the analysis you were mentioning?

Thanks in advance,

P.P.

 

[rb1957]

sure, LS Dyna is not in the ANSYS suite, I'm sure ANSYS has some similar analysis.

There should be plenty of references for impact analysis from the general (ANSYS manuals, tutorials) to the specific (impact analysis on walls, like for hurricane projectiles).

another day in paradise, or is paradise one day closer ?

 

[drawoh]

pegus,

If your structure is fairly simple, you can analyse it numerically in MathCAD, Octave or with a spreadsheet. Your structure's reaction to impact is to vary displacement in an approximate sine curve. It does not matter much that your forcing function is not a sine curve.

--
JHG