How to get shock response at free end of cylinder using NASTRAN 1

[vivek7]

hello friends
1st of all i want to tell how can we get the shock response of any object let cylinder by test ......then to simulate the same condition in NASTRAN or Ansys what shoud be BC's i shoud use to get faith ful result....
one end of shell fixed to shock table using some plate fixture.. then table is dropped from certain height.... and input vaues the cylinder experience is ( about 12g for 8ms.. sine wave)...got its response at middle and other free end of shell using sensors...... output comes in terms of g letit be 14 ,20g... depending upon material,damping,stiff etc....
so in NASTRAN what the BC's i haveto apply at fixed end where i m applying 12g for 8ms..... or something else i should try to get faith ful result.....
thanks...

 

[40818]

You have not made it very clear as to your models make-up, which makes it impossible to judgde boundary conditions. If your truly after the shock amplification effects then your looking at a dynamics rather than statics platform.

 

[cbrn]

Hi,
in Nastran I don't know, but I see you also mentioned Ansys: in this system, you would have plenty of ways to setup an analysis for this, and the most realistic I think would be free-falling transient analysis just like in the experiment. Key for success would be correct definition of material and appropriate setup of contacts.

Regards

 

[Spirit]

Vivek7

there are basically 2 options: following the older versions of NASTRAN, you could attach the clamped end of your tube to a seismic mass (x10E6 times the mass of your item) and impose the measured acceleration profile to the seismic mass.
The newer versions anyway (from 2001 on, I think) allow you to impose the prescribed acceleration directly at the mounting points by means of SPC1 cards.
What you should in any case do is a transient respose analysis (SOL 112).
Looking up in the manuals should give you all the details you need, otherwise ask.


Cheers


Spirit

'Ability is 10% inspiration and 90% perspiration.'