headform drop test ABAQUS

[jonny17]

Hi everyone
I am relatively new to abaqus and am trying to simulate a headform drop test onto firstly an unyielding surface and later a variety of third generation turf systems.
Would anyone be able to suggest the best way to obtain acceleration outputs from the centre of gravity of the headform (i.e. 'the accelerometer')? Currently I have tried constraining a node at the CoG and fielding A3 history outputs but have somehow managed to output both positive and negative acceleration when it should only have a deceleration peak.

Any help into the steps anyone would take would be appreciated.
Thanks

 

[rstupplebeen]

Could acceleration be due to ringing of the part? Some more details such as boundary conditions mesh type are there muliple part? Images alwase help.

Rob Stupplebeen

https://sites.google.com/site/robertkstupplebeen/

 

[jonny17]

The floor is constrained by encastre boundary conditions and meshed with R3d4 elements. The headform is given a predefined intial velocity of -2.7m/s to represent the final velocity from a free fall height of 0.376m and is meshed with C3d8r elements. Is there an easy way of getting a history output for A3 at the centre of mass? I used double-analysis precision to try to eliminate noise and butterworth filtering in the results but acceleration at all nodes appears to produce a positive negative output such as in the attached picture

 

[rstupplebeen]

I am sorry it took so long to wright back...

It does look like ringing. Here are my suggestions in the order I would try them.

1. If I remember the DOT and DOD use a steel headform inside a helmet that is dropped onto concrete. I would start with concrete as the floor and go stiffer from there. The slight 'give' sometimes does wonders for these analyses.
2. Model the head as the test will be performed. If you are using a dummy try to model that starting simple then increase complexity from there.
3. Damping either material or global may be needed. Even the air damps the system.

I hope this helps.


Rob Stupplebeen

https://sites.google.com/site/robertkstupplebeen/