Step up transformer for low frequency AC with DC offset
The EE definition for a transformer is: -


  "A transformer couples two or more AC signals through a magnetic
  field. Often used as galvanic isolation and to transform one AC
  voltage to another".


This means it won't step up the DC content of your signal. You'll need an amplifier and a power supply. 

The desired output is: Vf(t)=80Sin(2πft+ϕ)+40

The peak-to peak output is 160 volts then add another 40 volts on top of that to accommodate the DC offset. It's going to be a specialist bit of design and nothing really easily found off-the-shelf.