I have very very simply 3D solid model. 

I am stretching 5mm wide, 1mm thick and 20mm long hyper-elastic rubber tape.

20mm rubber tape is stretched to 160mm, strain = (160-20)/20 = 7

Case 1:

Displacement boundary condition  at the end of rubber tape :140 mm.

Solution converge very quickly

Case 2:

Calculated force required for stretch from Case 1 and applied it to rubber end.

Applied only force without displacement boundary condition. 

Solution not coverage: even it does not reach 10mm,

Why displacement boundary works but not external force not work in the same model ?