The brake squeal noise is a high-frequency noise over 1 kHz range generated by the contact between the brake pad and the disk. The purpose of this paper was to investigate the behavior of the squeal noise characteristics of the brake system from an instability point of view, according to the variation of major parameters such as friction coefficient between the flexible pad and the disk, brake pressure, and Young’s modulus of disk. Full nonlinear perturbed modal analysis using commercial finite element analysis program was performed to derive complex eigenvalue results of the model. And the sensitivity behavior was observed. Increasing the coefficient of friction or Young’s modulus of disk tended to make the squeal mode of the model more unstable. However, the change in brake pressure has a complicated nonlinear relationship with the squeal mode of the model. The judgment technique conducted in this study should be considered to be used in the design of the vibration point of the disk and pad of railway vehicles in the future.

The purpose of this study was to investigate the excitation force that generates the vibration of the reduction gear case for railroad vehicles. This excitation force is difficult to measure directly. The inverse stiffness method was used using the acceleration response measured in the experiment and the vibration response function derived from the finite element analysis. It was assumed that the excitation force acting on the reduction gear operates in the X, Y, and Z directions for each bearing, and a total of 12 excitation forces were investigated. When deriving the excitation force, singular value decomposition was applied to the vibration response function to increase the accuracy of the result. The results of the excitation force according to the number of degrees of freedom of the response were compared. Additionally, the magnitude of the estimated excitation force according to the singular value category used was compared, and it was confirmed that a too low singular value indicates a different excitation force.