Experimental modal analysis of an automotive drivetrain subframe

Scientific Essay from the year 2016 in the subject Engineering - Mechanical Engineering, grade: A, KTH Royal Institute of Technology (School of Engineering Sciences), course: Experimental Structure Dynamics, language: English, abstract: Within the framework of this project, the dynamic behaviour of a sub frame sup- porting the rear differential of vehicles is investigated. The original structure, consisting of sub frame and assembled gear, used hard plastic bushings. This setup caused noise inside the passenger cabin, which was not tolerated by customers. In order to obtain a better understanding of the noise's source, an experimental modal analysis of the structure is performed. After draping a point cloud over the structure, the frequency response functions between these points are measured. The complex exponential method, including Prony's method, provides algorithms which are used to extract the structure's modes. Within the frequency range of approx. 50 to 550 Hz seven eigenmodes are extracted. Two of them show strong interaction between sub frame and differential, while the residual modes are dominated by the frame's mode shapes.