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Force output of rigid body (Steel ball impactor) is zero througout the time.

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Hi all,


I am running a simple drop-ball model of a steel ball falling with a certain speed into a plain concrete beam. 

I am interested in knowing the force exerted by the beam on the steel ball. I have the RCFORC output working fine now after I added a CONTACT_FORCE_TRANSDUCER_PENALTY. 

However, when I try SECFORC (by defining a solid set and a set of nodes) the outcome of the total force is a constant zero. SECFORC works just fine for the concrete beam. 


I am wondering why force is a constant zero for my rigid steel ball? 

Also, what is the best way to know the exact (most accurate) force exerted on the ball due to the impact? because I need to create a "modified" concrete material that exerts less force on impactors for my research, that is why I need to know the force on the ball. 


Thank you!

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Negative Volume
Posts: 639
Joined: 5 years ago

Hi @moaown,

The section force of the rigid ball is zero because rigid parts cannot deform, so there is not way for that section to register force. The rcforc is just the contact force between the two parts which is possible when one part is rigid. Theoretically, the force in the contact should equal the force on the beam and the force on the ball (equal and opposite force remember). So you can use either your rcforc or the beam force to gauge this.

Alternatively, you could prescribe a deformable material to the ball if it’s a solid, like steel, and then measure the secforc on it. This will change your force compared to the rigid ball slightly.