Learning Forum

[Tonmoy]

Dear Dr. Basu,

Thank you a lot for getting back to me. I was expecting your response as, to the best of knowledge, you are an expert implementing LS-Dyna for structural applications. I have read several of your papers (on PML, which I am going to do in future) and also studied the example files you have provided in the old LSTC website. Though I did not understand much of them, but they were brilliant (much like a tutorial)!

Now, as you have suggested, I tried both the *LOAD_BODY and *BOUNDARY_PRESCRIBED on my model again. With *LOAD_BODY, after assigning DT=1E-5 in d3plot, the response I received from Dyna is quite close but not “overlapping” the analytical response. For capturing the dynamic response of the system the dt < T/10 is enough, right? In this case, the T of the beam was 0.00134 sec. Therefore, I thought the applied DT for d3plot was enough, but the results did not agree.

For the *BOUNDARY_PRESCRIBED_MOTION_NODE, I used the keywords below:

*BOUNDARY_PRESCRIBED_MOTION_NODE
1,1,1,1
*BOUNDARY_SPC_SET
1,0,0,1,1,1,1,1

However, the problem of moving the whole system toward the application of the motion remains if I am using this keyword. Could you suspect what might be a cause of this behavior?

I have gone through some of the examples in the LS-Dyna Example manual and will try to replicate models from that URL you have provided me.

(You are correct that the Y and Z DOFs were perpendicular to the beam section. The model was done through a 3 node beam element with ELFORM 4 to get accurate result. Also, I have not meshed up the beam as I wanted it to act as a SDOF system and meshing it introduces a lot of DOFs in there, which I verified by doing a Eigenvalue analysis).