A foil journal bearing, having: a shaft; a top foil surrounding the shaft in a circumferential direction; a corrugated bump foil surrounding the top foil in the circumferential direction, wherein the corrugated bump foil includes a plurality of adjacent corrugations that each include sidewalls that extend from a radial inner end to a radial outer end of the corrugated bump foil; and a bearing sleeve surrounding the corrugated bump foil, wherein: at least one of the sidewalls of at least one of the corrugations includes an undulation disposed between the outer and inner radial ends of the sidewall; and the undulation is defined by an undulation outer end and an undulation inner end.