Reference mesh with Part and Instance, Initial conditions, NODE REF COORDINATE

[blazejpop]

I'm trying to define a reference mesh for my explicit analysis, but I want to define my model in terms of Parts and Instances in Abaqus CAE and then write the "*Initial conditions, Type=NODE REF COORDINATE, Input=xxx.inp" line in the inp file.
The problem is that Abaqus will not let me to do this and will complain with "***ERROR: Unknown global id: xxx (first referenced node number)".

I have renumbered the nodes, so that the part of interest has its own, uniquely numbered set of nodes, but it keeps complaining about that.
I worked this issue around with specifying my model in terms of Nodes and Elements only, deleting Parts and Instances blocks in the inp file. In such a way it takes the reference mesh into account.

I would really want to use the first way of modeling, with Parts and Instances, since I will need to include some additional parts in the model after the initial analyses.

Does anyone know if this is possible in Abaqus or I have to follow the second way of building the model?

 

[FEA way]

You can run data check analysis and query nodes in the generated odb to find out how they are numbered/labeled. This way you should be able to determine proper input for the keyword that causes problems here.

By the way, it's possible to write the input file without parts and assemblies so that you don't have to edit it manually. Just go to the "Edit Model Attributes" window and select "Do not use parts and assemblies in input files".

 

[blazejpop]

Hello FEA way! Thank you for the reply.

I followed your advice and queried the nodes of the instance, for which I want to use the reference mesh, in the odb file generated after the Data Check analysis of my model.
They are labeled in such a way: INSTANCEOFINTEREST-1.11299, where the nodes numbers go from 10001 to some bigger number. And this is one of the two parts in the model. The other one is just a rigid, one-element plate.

When I include nodes, referenced in the way written as "INSTANCEOFINTEREST-1.11299", in the reference mesh input file, Abaqus gives me the error:

***ERROR: FIRST ENTRY INSTANCEOFINTEREST-1.10001 IS NOT A NODE NUMBER WHICH IS REQUIRED 
           FOR *INITIAL CONDITION, TYPE= NODE REF COORDINATE

And such error appears for each of the referenced nodes.

When I include nodes, referenced just as "11299", Abaqus gives me just one error, mentioned in my original post:

***ERROR: Unknown global id: 10001

I want to use Parts and Instances because later I will need to import the initial state of the instances and, as far as I know, it must be done with Parts and Instances, not the one where there are only nodes and elements defined.

 

[FEA way]

Which version of Abaqus do you use ? It seems that in the newest release this error doesn’t appear.

 

[blazejpop]

I am using version 2019. If this is true, I hope I could get the access to the newer one.

 

[blazejpop]

Well, it turns out it doesn't work in Abaqus 2021.
I created a new mesh and Abaqus gives me the same error as mentioned in my first post if I want to conduct the calculations with parts and instances ("***ERROR: Unknown global id: 23121"). However the node listed as unknown is now not the first one in the list, but somewhere in the middle.

If I check the "Do not use parts and assemblies in input files" it works as it's supposed to.

 

[blazejpop]

It turns out this case can be described according to a certain saying in computer science: "It's not a bug, it's a feature." I got the answer to my question in the DS forum so I'm forwarding it here. One of the users said he remembers how it was implemented -- this feature was developed many years ago specifically for some important client company which didn't use parts and instances in their workflow. Thus, it's not likely to be amended anytime soon to allow this.