Interface forces extraction

Prasad Reddi_20512

My requirement from the load path is to monitor contact forces over a load path. As per the problem description in the attached picture, I would like to extract contact forces on each part No. 1, 2, 3 when a impactor hits the part 1. I came across a card /INTER/SUB, but the card contents are not clear to understand. Main_ID1, Second_ID, Main_ID2 are the ones with no proper explanation about the definition's and usage. Can someone throw light in this area? If there is any other alternative apart from /INTER/SUB to extract contact forces, that will be great to know.

Looking forward to hear about the response. 

 

PaulAltair

Hi, yes, /INTER/SUB is what you would use for this

Not sure where you were looking in the help? The definitions of each field (Main_ID1, Second_ID, Main_ID2) are given in the /INTER/SUB help along with diagrammatic example for Type 7.

The approach would vary depending on your primary contact (Type25 or Type7?)

Each Sub interface may be considered a transducer for forces between 2 groups (the entities involved must already be inside an existing contact)

If you have a Type 7 (Self Contact?) on your Mass, Parts 1-3, we can call that contact 1

Example here for Part 1:

You would create 2 x /INTER/SUB contacts referencing contact 1 as the 'inter_ID'

  For the first: Main_ID1 would be a surface group of Part 1, Second_ID would be node group of Mass

  For the second: Main_ID1 would be a surface group of Mass, Second_ID would be a node group of Part 1

You then can add /TH/INTER request for both of these sub interfaces and sum them to get total force between Mass and Part 1

You can repeat process for Parts 1-2,2-1 and 2-3,3-2

If you have a Type 25 Interface then the approach is similar, but you should take into account whether your primary Type 25 uses secondary nodes or not as to whether to also include a node set in the /INTER/SUB