[MBDyn-users] What is the exact definition of the "AssRes" and the "AssJac" member function of the Elem class defined in base/elem.h?
Resch Reinhard
Reinhard.RESCH at accomp.it
Tue Jan 25 15:05:54 CET 2011
Dear ladies and gentlemen,
I am trying to implement a user defined element which imposes a configuration dependent force to the system.
Especially the reaction forces of a hydrodynamic journal plain bearing should be imposed in this way.
For this purpose the member functions "AssRes" and "AssJac" have to be provided by the user defined element.
I guess that for a simple linear time invariant element with stiffness matrix K and damping matrix D the member function "AssRes" should return the residuum -f = -K*y - D * diff(y,t).
I also guess that the member function "AssJac" should return diff(f,diff(y,t)) + dCoef * diff(f,y) = D + dCoef * K.
Where the factor "dCoef" seems to be a so called "derivative coefficient" which is defined by the following equation:
delta(y) = dCoef * delta(diff(y,t))
y ... the vector of the node position and rotation angles of the nodes connected to the element
f ... the residuum e.g. the imposed forces and torques at the nodes connected to the element
delta(y) ... the increment of y for the current time step
diff(y,t) ... the derivative of y versus the time e.g. the vector of velocities and angular velocities of the nodes connected to the element
delta(diff(y,t)) ... the increment of diff(y,t) for the current time step
diff(f,y) = K ... the derivative of the force f versus y; in this case it is simply the stiffness matrix of the element
diff(f,diff(y,t)) = D ... the derivative of the force f versus the diff(y,t); in this case it is simply the damping matrix of the element
It would be fine if you could answer my question.
Best regards
Reinhard Resch
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mail: reinhard.resch at accomp.it
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