Needed clarification in Transient Dynamic analysis (DTRAN) with acceleration

John_22412

Hi everyone,

I'm trying to simulate "Transient Dynamic analysis (DTRAN) with acceleration.
Displacement output is looking different as below,

Acceleration output plot from Input nodal point which is same as Input data as below

Input data from TABLED1

Displacement output plot from Input nodal point .

This makes confusion. couldn't identify the root cause.

Please have a look at it and let me know your suggestions/comments/experience.

Thanks you,
John.

Adriano_Koga

hi,

 

i didn't follow completely your model, but i understood that your input is acceleration, right?

You acceleration is only positive, so displacements would only increase.

How your first graph was generated?

John_22412

Adriano A. Koga_21884 said:

hi,

 

i didn't follow completely your model, but i understood that your input is acceleration, right?

You acceleration is only positive, so displacements would only increase.

How your first graph was generated?

Hi,

 

Thank you for reply.

First graph was generated from Nodal acceleration output on applied acceleration location.

Nodal output result is keep on going upward for any form of acceleration input.

please refer attached data. 

Im expecting displacement plot as attached below image.

 

Looking forward your feedback.

Thank you for your support.

Adriano_Koga

John_22412 said:

Hi,

 

Thank you for reply.

First graph was generated from Nodal acceleration output on applied acceleration location.

Nodal output result is keep on going upward for any form of acceleration input.

please refer attached data. 

Im expecting displacement plot as attached below image.

 

Looking forward your feedback.

Thank you for your support.

just saw your model here, and it looks like you're running a transient loadcase for simulating a half-sine shock event.

As the half sine acceleration is always positive (acceleration), if you integrate, you will have always positive velocity. Integrate again, and your parts will be "flying away".

 

But if you compare max acceleration in your structure, you will see an amplification of ~1.4 the input shock. This is pretty much expected, and could be calculated through an SRS.

Adriano_Koga

Adriano A. Koga_21884 said:

just saw your model here, and it looks like you're running a transient loadcase for simulating a half-sine shock event.

As the half sine acceleration is always positive (acceleration), if you integrate, you will have always positive velocity. Integrate again, and your parts will be "flying away".

 

But if you compare max acceleration in your structure, you will see an amplification of ~1.4 the input shock. This is pretty much expected, and could be calculated through an SRS.

despite the legend in HG, both graphs in the previous post are accel plots. Blue one is your input, and green one is the maximum value for the model (usually at the tip of your chassis).

 

Below the Displacement goes up and up.