The shape error evaluation methods of the foils for a multi-leaf foil bearing

The geometric parameters of the elastic foil bearing are important basis for designing the foil bearing. Whether the main shape indices of the pressed foils meet the design requirements is the key to evaluate a manufacturing method. The inconsistent curvature radii of the top foils, the inconsistent bump heights of the bumps on the bump foil, the roundness error of the top foil, and the curve profile error of the bump foil may cause the pre-tightening assembly difference and different bearing capacity of each bearing shell. Aiming at the shape error evaluations of the foils for a multi-leaf foil bearing, first, the algorithm of geometric area optimization for circle roundness error is introduced and an evaluation method of arc roundness error is put forward according to the minimum zone principle in this paper. This method can be used to calculate the roundness error of the top foil for a multi-leaf foil bearing. The results show that the corresponding roundness error of the top foil decreases with the increasing of the pressing pressure. The relative roundness error is small (less than 7%), which changes a little with different pressing pressures. For the measurement of a bottom bump foil, the method of matching feature points is used in pre-location and then fine-positioning for the measured curve is implemented based on the least square method in order to eliminate the position error between the measured curve and the design curve. Thus, the curve profile error evaluation of the bottom bump foil for a multi-leaf foil bearing is implemented and the profile error of each bump can be obtained. According to the shape error evaluation values of the top foil and the bump foil, the quality control strategy and the error compensation by improving the mold structure can be further researched.