How to realize an "archimedean spiral" movement

[blacky130787]

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 !!!!

 

[Mustaine3]

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.

 

[blacky130787]

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?

 

[Mustaine3]

You can do it like this:

*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

 

[blacky130787]

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 !!!!