The Fixed Support is preventing one end of the tube from moving at all, which means that the elements near that support have to bend a lot as the pressure is applied. That is an unnatural motion in the simulation compared with the real vessel wall.

I recommend replacing the Fixed Support with Displacement on the same face that allows radial freedom. This is best accomplished by creating a Cylindrical Coordinate System at the center of the vessel.  Delete the Fixed Support and apply Displacement so that Z and Y are zero, but X (radial) is Free. That will allow the entire tube wall to expand as the pressure increases.