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direction in lumped-structure connection
Posted 25.10.2024, 10:26 GMT-4 4 Replies
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How is it define the direction under lumped-structure interaction in user defined x,y,z? I thought it was normalized direction so it could have -1 to 1 value depending on the position. For example: if I'm considering a cylinder with radius r=2 centered at 0,0,0 where I attach some mass-spring system in the circumference. This mean that given a point with angle theta has x,y component depending on cos(theta) and sin(theta). This point should depend on its position like x=rcos(theta), y=rsin(theta) and z=z_point, or only its direction as x=cos(theta), y=sin(theta), z=0; (i thought this one) when i m computing I get or no influence of my mass-spring system or a problem in the solver. I have tried to a simple case in 2D but I still do not understand. I attach file.
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Hi Filippo,
The Lumped-Structure Connection has a User Defined option to define the direction. Since the Lumped Mechanical System is 1D displacement, the direction defines the 1D axis. Consider a 2D Steel section excited only in the x direction with a lumped resonator attached. If the direction (x,y) is (0,1), we would expect no displacement in the resonator mass because it is not excited in the direction to displace the mass at all. If the direction is (1,0), we would expect maximum displacement. Other directions will have some component of displacement less than the maximum. The attached model here shows this. Hope it helps.
Best, -Mark
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thanks for the answer Mark, i have checked all the component if they were correct but or it does not converged due to maximum umber of segregated iteraction (which try to increases) or the presence of mass-spring system is not affecting the structure. In 2d everyhing works perfectly but when i move to 3d model and in particular to cylinder it's not working anymore. In the first post i have attached my model.
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In the model, there are no frequencies listed in the study step. I am not sure what frequency you are solving for as this may affect the convergence. With regard to the error for maximum number of segregated iterations, you could try switching to a fully coupled solver. This should be more robust.
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Dear Mark, thanks so much for replying me, it actually works in the first mph file called mylastone.mph attached in the first post even though PARDISO switched to out-of-core mode. Is there another way to simulated these local resonators instead of using the following setup: In Lumped mechanical module: displacement node where input disp. is from muticoupling, spring, mass and free node connected in series defined as subsystem. i thought another way where displacement node is set in the same way but i add external source between mass and the free node where for the first port i have used intop1. and for port 2 i set 0 as displacement since is free node. the issues is that intop1 can only that one component of the displacement as intop1(u) but i need 2 displacement intop1(u) and intop1(v) since i m considering both direction in the x,y of my spring-mass system . i thought i add another external source with the other component but it's not working.
Best FIlippo