Abstract
Modal differential substructure that can quickly predict effects of structural modifications has been proposed by the author. This method utilizes simulation results of the model before the structural modification. Because the method does not require the user to decide the section of structural modification beforehand, the user can determine the section after checking the calculation result.In a certain case, however, where the model has to handle very many modes, the eigenvalue problem becomes insoluble due to singularity of the mass matrix. This report elucidates the reason of the problem and shows a procedure to avoid it.
