Originally Posted by
davidad
It can fatigue and crack as will aluminum and less often steel. If it was welded properly (shield gas in and outside the tube until the temp dropped below 800F) it should be ok.
Steel fatigues and cracks, too, if subjected to stress above a certain point - which is likely for lightweight steel frames.
I would think a recumbent trike would generally be overbuilt enough to keep stresses in the frame low, but it varies from bike to bike.