Mike Rife
Ansys Employee
No you do not need to define the hysteresis heat via HGEN. Please see the MAPDL Help -> Coupled Field Analysis Guide chapter 2.6.5 that is an example of viscoelastic heating of a rubber cylinder. It includes the MAPDL input file you can use as a guide.
p.s. depending on the version the chapter sub-section may be a bit different.