I made a model and used a single vertex that was fixed because it would solve relatively quickly. In that model, if I wanted to induce a "potato chip" deformation, I would use a two step solution, and in step 1, I would put a small force on the ends of the sheet to bow it slightly. This can ramp up as the temperature ramps up. Then in Step 2, the force is ramped down to zero. It might turn out that the sheet remains bowed.

You can create a model where there is a larger surface, let's call it the floor, that is in the same plane as the sheet body that gets the thermal load. The floor would be configured as a Rigid body.  You need a Fixed Joint to Ground to hold the floor. You then create a frictional contact between the sheet and the floor. The floor has to be the Target side of the contact pair.  You add Standard Earth Gravity to hold the sheet to the floor. The frictional contact will greatly slow down the solution progress.

If you further want to put a heating pad on top of the sheetmetal, that slows the whole process down even further. There will be a lot of struggle to obtain convergence.

Some of that can be alleviated if you do a 1/4 model, and enforce a symmetric deformed shape.