Why Kinetic Energy is not accurate ?

Ashish_21705

Hello Everyone,

I want to understand the Input Kinetic energy concept in Radioss. I have made an small example where I am impacting shell tank 2mm steel with a Rigid-Plane. Please find the attached example.

 

The mass what I have given only to the Impactor is 1.331 tons which I have analytical calculated 0.5*m*v2 and it should give me 149 KJ but rather it has given output 155 KJ after calculation which is based on the mass of the whole model that is 1.4 tons.

 

According to me it doesn’t make any sense that output Kinetic energy is according to the total mass of the model not just the Impactor itself.  Please see picture below :-

 

 

Can somebody explain me this ??

 

Thanks !

 

Rogerio Nakano_21179

Hi

In the Engine you are setting

 

/INIV/TRA/Y/1
15000.0000000000
20000000 25000000

in this nodes range, you are selecting all nodes in the model, then the velocity is applied to all nodes

 

I hope this is helpful

Regards

 

 

Ashish_21705

Hello Rogerio,

Thanks for your response !

 

Yes actually you are right only these nodes i have given velocity 15000 mm/sec but these nodes have mass 1.31 tons according to it output should be 146 KJ but in the picture if u see above its more 155 KJ which means it is giving output according to the total mass i.e 1.4 tons. Which should not be the case right ?

 

Output K.E should be only according to the nodes where velocity is applied.

 

Thanks & Regards,

Ashish

 

 

Adriano_Koga

Ashish_21705 said:

Hello Rogerio,

Thanks for your response !

 

Yes actually you are right only these nodes i have given velocity 15000 mm/sec but these nodes have mass 1.31 tons according to it output should be 146 KJ but in the picture if u see above its more 155 KJ which means it is giving output according to the total mass i.e 1.4 tons. Which should not be the case right ?

 

Output K.E should be only according to the nodes where velocity is applied.

 

Thanks & Regards,

Ashish

 

 

for what i understood from rogerio's reply is that all your nodes fall in the ID range for initial velocity, meaning all of them got the initial velocity os 15000mm/s. That's why all of then have KE accounted.

I believe your plate nodes should be in a different ID range in case you don't want them to have initial velocity.

Ashish_21705

Adriano A. Koga_21884 said:

for what i understood from rogerio's reply is that all your nodes fall in the ID range for initial velocity, meaning all of them got the initial velocity os 15000mm/s. That's why all of then have KE accounted.

I believe your plate nodes should be in a different ID range in case you don't want them to have initial velocity.

Hello Adriano,

 

Thanks for your reply !

 

Actually these ID range 20000000 25000000 i have setted only for Impactor in my model not anything else included may be you can also check my test_dummy.zip file. Thats why my question is then why energy output is more than the expected value. Thanks !

 

Regards,

Ashish