There are some material models that are not available for both solvers. Whenever a question mark symbol is observed next to the Engineering Data cell, it must be properly addressed. By inspecting the materials, it should be clear where the problem is. For example, it might be a missing density value or a parameter which has not been set; something which might be required for the Explicit solver but not for the Implicit one. This is the case with hyperelastic materials using the Mooney-Rivlin material model. To get a value for the incompressibility parameter, the user must either have the experimental data and use curve fitting, use a value from another material specification, or just use the rubber model in the Explicit material database.

Another issue you might encounter is where a parameter that is required for the Explicit simulation can interfere with the Implicit solution and make it unable to solve. This often occurs since both systems share the same material data, and can be fixed by using different material assignments (if you are using the Geometry cell data transfer and have separate Mechanical instances). A problem with unsupported material model types is usually seen as an error message in the solver.log file or the Solution Information when a solve is attempted.

Another common example of a problem is having tabular data input for a material property in Implicit with, for example, 12 stress strain pairs. This would trigger an error in the explicit solver, which only supports 10 or less stress strain pairs. An easy workaround for this would be to take the curve formed by the 12 points and delete two points, relocating the others so that the curve shape remains the same.