@dichtstoff Thank you for the reply. I carried out some additional tests in both Abaqus and CalculiX. Here’s a summary of the results:
As you can see, the closest I managed to get to the analytical solution (23.625 mm) in both programs is with C3D8R elements and surface traction. Much to my surprise, neither second-order nor incompatible mode hexahedrons helped in this case. Perhaps the analytical solution is simplified in some way or solid elements can’t reach that level of accuracy in this case.
Anyway, I will share the analytical solution soon since I plan to publish a YouTube tutorial for this analysis. But I’m not sure if this solution will be useful for you since it’s just a single already derived formula taken from a quite old Polish book.