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How to realize an "archimedean spiral" movement

How to realize an "archimedean spiral" movement

How to realize an "archimedean spiral" movement

(OP)
Hey guys,

I would like to realize a special movement of my Reference Point in ABAQUS. It should follow a curve which is an "archimedean spiral".

My problem is that i don´t know how to realize a variable length of the radius dependent on the circular angle PHI. The radius r in a cartesian coord-system is as followed:

x-direction: a*PHI*cos(PHI)
y-direction: a*PHI*sin(PHI)

with thwe constant parameter "a"

Do you have any suggestion how to realize a movement like this? Becaus i don´t know how to realize a variable amplitude :(

Sorry for my bad english ;)

Thanks for your help !!!!

RE: How to realize an "archimedean spiral" movement

You have to think also about the variation in time.

When you know before how the position changes with time, you can make tables x vs. t and y vs. t in Excel and use them as amplitudes.
Or you write a user subroutine.

RE: How to realize an "archimedean spiral" movement

(OP)

Thanks Mustaine3 !
Yes i know the time at each Position. But how do i have to add severeal BC for one and the same RP? In the past i tried to create 2 different BC for one Mode ( one for U1 direction and another for U2 direction) Bug there was an error message that these two BC were in conflict to each other.

Or can i create 1 tabular amplidude witz 2 dependences ( x vs t and y vs t)? Bug how can i tell abaqus to use e.g. x vs t for U1 and y vs t for U2 ? Do you know what i mean?

RE: How to realize an "archimedean spiral" movement

You can do it like this:

CODE -->

*Amplitude, Name=x-amp
0, 0, 1, 8
*Amplitude, Name=y-amp
0, 0, 1, 5
:
:
*Boundary, Amplitude=x-amp
13, 1, 1, 1
*Boundary, Amplitude=y-amp
13, 2, 2, 1
*Boundary
13, 3, 6, 0 

RE: How to realize an "archimedean spiral" movement

(OP)
Thank for your helf Mustaine 3 !!!

It works very well. Thats the same way i tried in the past, but it didn´t work. But know everything works. THANKS !!!!

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