Extremely high values of g-force due to impact in abaqus explicit

[Bharathsf]

Hi,
I have modeled a crash analysis of an Unmanned air vehicle on a rigid ground in abaqus explicit. I took the vertical velocity of the UAV as 700 mm/s (0.7 m/s) and the horizontal velocity 12000 mm/s. I want to find the g-force at the point of impact as soon as the impact takes place. The problem is when i plotted spatial acceleration vs time graph in abaqus to find out the g-force I am getting deceleration of the order of 0.22x10^9 mm/s^2 at the time of impact and the g-force is 22000 which I am sure is a very high value..i dont know what exactly is the problem..I have plotted spatial acceleration (vertical component-y axis in my case) A2 vs time. Is there any other option for the acceleration or am i making a mistake in taking the units of acceleration in the graph?
I have taken the units while modelling as
Length-mm
time-s
Mass-Tonne
Density-tonne/mm^3.

Please help

Bharat

PS-sorry for the bad english

 

[burningDiesel]

Depending on how heavy your object is, 22000 can be real result (although a bit high yes). Are we talking model planes of few hundred grams, or military drones?

 

[Bharathsf]

Thanks for the answer its a model plane totaling about 3.8 kgs including all the payloads..but if the g-force is so high at impact,will the stresses also be very high? because I am getting stress values about 150 Mpa..

Thank you

Bharat

 

[burningDiesel]

Then it's indeed pretty high. Can't say what's wrong though.

 

[isponmo]

Hi Bharathsf,

Did you finally manage to find a solution to your problem? I get exactly the same issue with an impact analysis in which two elastic bodies bump into each other. The accelerations turn out to be huge and are competely different to the experimental results...

Best regards.