Abstract: In order to extract the model parameters for the digital twin of spiral bevel gear accurately, the model test for the spiral bevel gear is performed to obtain the model frequency, model shape, and frequency response function of the free model. The calculated self-modal assurance criterion matrix (Auto MAC) proves that the modal vibration pattern extracted by the modal test is accurate. The physical properties of the spiral bevel gear are refined to approximate the test modal frequencies of each order. Furthermore, the modal frequency, modal shape and frequency response function of the free mode are obtained by modal simulation. Compared with the modal test results, the maximum modal frequency error is 1.235%. The cross-modal assurance criterion matrix (Cross MAC) for the test and digital twin modal shapes are calculated, showing that the digital twin modal shapes are in close agreement with the experimental modal shapes. The comparison of test and simulated frequency response functions further validated the accuracy of the modal analysis of the digital twin. The modal simulation of the digital twin can not only identify the modal parameters that cannot be tested due to the experimental conditions; by comparing the experimental and simulated modal Cross MAC with the experimental modal Auto MAC, the modal parameters with slightly large experimental errors can also be identified. The comparison of tests and simulations demonstrates that the spiral bevel gear digital twin model constructed is accurate, and can solve the problem of measurement inaccuracy and inability due to test condition constraints.

Key words: modal analysis, spiral bevel gear, digital twin, modal shape, modal test