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how to define ramp force
Posted Apr 7, 2010, 11:44 a.m. EDT 4 Replies
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hai all,
i want, how to define ramp force with in a fixed time(means with in 6 seconds).
if any one knows please help me, it's very helpful to my project.
Nagamalli
i want, how to define ramp force with in a fixed time(means with in 6 seconds).
if any one knows please help me, it's very helpful to my project.
Nagamalli
4 Replies Last Post Apr 11, 2010, 12:57 p.m. EDT
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Posted:
1 decade ago
Hi
if you define a boandyry load such as Fx=DF*t then you have a ramping force, with scale "DF[N/s]", if you want it to stop after 6 seconds a Fx=DF*t*(t<=6) will do, but then you have some nice spikes that might give you some solver convergence issues, to be tested out, try to set a small time intervalle around the abrupt stop.
Better you can smoothen with a heaviside function search the doc for "flc1h" or a combination of cos or sin functions (to ensure a couple of continuous derivatives), this often helps for the solver convergence
Have fun Comsoling
Ivar
if you define a boandyry load such as Fx=DF*t then you have a ramping force, with scale "DF[N/s]", if you want it to stop after 6 seconds a Fx=DF*t*(t<=6) will do, but then you have some nice spikes that might give you some solver convergence issues, to be tested out, try to set a small time intervalle around the abrupt stop.
Better you can smoothen with a heaviside function search the doc for "flc1h" or a combination of cos or sin functions (to ensure a couple of continuous derivatives), this often helps for the solver convergence
Have fun Comsoling
Ivar
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Posted:
1 decade ago
Thanks for the response Ivar
Actually i am applying ramp force 1MN to 30MN with in 6 seconds.
is it possible to give the force with this function Fx=DF*t*(t<=6)
what i am saying is what is the meaning of DF*t* , i couldn't understand.
if possible, could explain clearly.........t is time
and DF means is it a function(like F=ma)?
Nagamalli
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Posted:
1 decade ago
Hi
Wellif I understand you correctyl youre force expression is something like
F[MN] = 1[MN]+(30-1)[MN]/(6[s])*t
with this formula you must stp your simulation after 6 seconds, because your force will continue to ramp.
Make a "function" out of this an use the plot functionality to check its shape and values.
If your simulation is to last > 6 sec, but you want to saturate at 30[MN] I would write:
F[MN] = 1[MN]+(30-1)[MN]*min(t/6,1)
does this help ?
HAve fun Comsoling
Ivar
Wellif I understand you correctyl youre force expression is something like
F[MN] = 1[MN]+(30-1)[MN]/(6[s])*t
with this formula you must stp your simulation after 6 seconds, because your force will continue to ramp.
Make a "function" out of this an use the plot functionality to check its shape and values.
If your simulation is to last > 6 sec, but you want to saturate at 30[MN] I would write:
F[MN] = 1[MN]+(30-1)[MN]*min(t/6,1)
does this help ?
HAve fun Comsoling
Ivar
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Posted:
1 decade ago
Thanks Ivar.
this should be useful my project.
Nagamalli