Hi there! I have a strange problem with switching boundary conditions between step 1 and 2 in ABAQUS/standard. Here is a quick description of what I'm trying to do:
Imagine two objects with one being made of a soft material enclosing the other which is made of a different material (like a fruit with its seed).
Step-1
In the first step, I define deformations for all of the nodes on the outer surface of the outer object as displacement BC's (DOF1,2,3), while I define zero BS's for the internal object. The rest of the nodes in the space between the stiff object and the outer surface of the soft object with the predefined values, will move around accordingly.
Step-2
In the second step, I would like to release the zero BSc on the stiff core of the model, and fix some areas on the surface of the soft object at their final values at step 1 (call this node set "A"). So I want all the node locations to start from the values they gained at the end of the first step, but I don't want this to be a BC throughout the second step. I just want them to evolve from whatever value they had at the end of the first step, except for node set "A" which has to be fixed at those values. But here is the problem:
To lock node set "A" at its initial location at t=0 of the 2nd step, I know I can use the FIXED option, but the problem is the rest of the nodes. I don't want them to return to their zero values at the beginning of the FIRST step, which is what happens. Because if I use the FIXED option along with OP=NEW to remove the rest and keep set "A" nodes fixed where they are, it zeros all the deformations I created in the first step which I want to keep. If I use FIXED with OP=MOD, I get the conflicting BC's error since some of these had BC's in the first step (even though these are the same values I'd like to retain). If I don't use FIXED at all, then again OP=NEW releases all the nodes back to the undeformed state.
In short: how do I fix some nodes at their respective values in the beginning of step 2, while being able to release the rest of the zero and nonzero BC's defined in the first step, and let those nodes start from the final locations at the end of step 1?
I will greatly appreciate your response!! Thanks!
PS: I have found out that I can use either *Restart, READ, or the *Import card and break down the analysis into two separate steps. But I still have the same problem of everything starting from zero in the second step. Is there something I'm missing here? Thanks
Imagine two objects with one being made of a soft material enclosing the other which is made of a different material (like a fruit with its seed).
Step-1
In the first step, I define deformations for all of the nodes on the outer surface of the outer object as displacement BC's (DOF1,2,3), while I define zero BS's for the internal object. The rest of the nodes in the space between the stiff object and the outer surface of the soft object with the predefined values, will move around accordingly.
Step-2
In the second step, I would like to release the zero BSc on the stiff core of the model, and fix some areas on the surface of the soft object at their final values at step 1 (call this node set "A"). So I want all the node locations to start from the values they gained at the end of the first step, but I don't want this to be a BC throughout the second step. I just want them to evolve from whatever value they had at the end of the first step, except for node set "A" which has to be fixed at those values. But here is the problem:
To lock node set "A" at its initial location at t=0 of the 2nd step, I know I can use the FIXED option, but the problem is the rest of the nodes. I don't want them to return to their zero values at the beginning of the FIRST step, which is what happens. Because if I use the FIXED option along with OP=NEW to remove the rest and keep set "A" nodes fixed where they are, it zeros all the deformations I created in the first step which I want to keep. If I use FIXED with OP=MOD, I get the conflicting BC's error since some of these had BC's in the first step (even though these are the same values I'd like to retain). If I don't use FIXED at all, then again OP=NEW releases all the nodes back to the undeformed state.
In short: how do I fix some nodes at their respective values in the beginning of step 2, while being able to release the rest of the zero and nonzero BC's defined in the first step, and let those nodes start from the final locations at the end of step 1?
I will greatly appreciate your response!! Thanks!
PS: I have found out that I can use either *Restart, READ, or the *Import card and break down the analysis into two separate steps. But I still have the same problem of everything starting from zero in the second step. Is there something I'm missing here? Thanks
