Abstract:

An approach, based on congruent transformation, for modal transform of the structure under different boundary conditions is proposed.The main purpose is to use this approach to transform the elastic mode got from the modal test of a specimen fixed on vibrostand to the mode in free free state of the same specimen.Two kinds of specimen constraints are considered:statically determinate and statically indeterminate. In the first case, modal matrix is constituted of elastic mode and rigid body mode of the specimen.In the second case,released inertia force attachment mode should be added to form the matrix mentioned above.Reasonableness of the approach is expounded and two examples are carried out to demonstrate the feasibility and effectiveness of the approach as well.

Key words: modal transform, mode, congruent transformation