On the Assessment page for the module Moodle site you will find five frequency response functions for the frequency range 20 to 100 Hz in the EXCEL spreadsheet "FRF_Data". These are receptances excited by a shaker placed at Position 1 on a front sub-frame mounted across the body of a car.

The five positions are equi-distant across the sub-frame. Both the excitation and the responses were in the vertical direction with "up" considered positive. The magnitudes are in mm/N and the phases are in degrees. The phases are defined such that a lead angle is positive. The phases are in the range -180 to 180 degrees.

(i) You are to conduct a modal analysis on this data to obtain:

(a) The number of significant modes of vibration in the frequency range and estimates of their natural frequencies.

(b) Estimates of the mode shapes for the five positions for each of the modes. You should normalise these on Position 1.

(ii) Comment on each of the modes of vibration.