ANSYS Coupled Thermal-Structural Analysis Fails After Adding Anand Viscoplastic

[dasaret.bakillari]

I am running a coupled transient thermal/structural analysis of a power electronic package consisting of several layers. For each layer, I defined the required thermal and mechanical material properties.

When I run the analysis without the Anand viscoplastic model, the simulation completes successfully. However, as soon as I assign the Anand model to one of the layers (die attach/solder layer), the solver fails with errors related to undefined material properties.

Initially, I received errors related to the thermal property KXX for elements belonging to the layer where the Anand model was assigned. I then tried using two separate engineering data sets: one for the transient thermal analysis (without Anand) and one for the transient structural analysis (with Anand enabled). In that case, the thermal analysis runs, but the structural analysis fails with errors related to missing mechanical properties such as EX.

Has anyone experienced similar issues when using the Anand viscoplastic model in coupled thermal-structural analyses in ANSYS Mechanical? 
If it helps, I am using Workbench 2024 R2

[John Doyle]

Hard to say for sure, but it might be a book keeping issue.  For layered shells/solids, the MAT number you give to SECDATA for the solder layer must match the material ID for which you defined both MP  and TB,RATE,ANAND.   If a layer references a MAT that has no complete property set for the active element (e.g., missing EX, or missing thermal data for a coupled-field element), MAPDL reports undefined material properties.