Hello,

I am currently working on a heat treatment simulation of case hardening using Abaqus/CAE 2025. My approach involves two sequential simulations:

First, I perform a diffusion analysis using a Mass Diffusion step with DC3D8 element types. This results in a specific carbon concentration distribution (represented by CONC and NNC11).

In the second stage, I conduct a quenching simulation. For this, I am using the C3D8T element type within a Coupled Temp-Displacement step to account for thermal analysis as well as subsequent strains and stresses. The mesh is identical in both simulations, with the exception of the element type.

My goal is to import the carbon concentration results from the diffusion analysis into the quenching simulation. However, I have encountered the following issues:

• When using the Predefined Field (From File) option—both with and without the "mesh compatibility" setting—significant deviations in the concentration values occur.
• Importantly, these discrepancies persist even when the element types are kept identical between the two analyses.
• An attempt to import the values at the integration points via a list using the UEXTERNALDB subroutine did not lead to the desired results.

Does anyone have an explanation for these discrepancies? Furthermore, what would be the recommended solution to transfer the concentration data as accurately as possible between these two simulation steps, given that the mesh geometry is identical? 

I would appreciate any help and insight.