MODAL METHODS FOR TRANSIENT DYNAMIC ANALYSIS IN LS-DYNA

Modal analysis methods offer an opportunity for tremendous cost savings compared to traditional explicit approaches to transient dynamic analysis. Modal methods approximate the structural response of a body by a linear combination of pre-computed mode shapes, eliminating the need for explicit element processing. LS-DYNA’s new modal analysis capability is combined with existing rigid body features to offer the additional advantage of large rigid body motion with superimposed linear modal response. This allows a portion of an LS-DYNA model to be represented by modes, while other parts of the model are treated with standard nonlinear explicit methods. LS- DYNA has also been enhanced to compute several types of modes, including eigen modes, constraint modes, and attachment modes. These modes are written to binary databases which can be viewed using LS-POST, and used as input to subsequent modal analyses. This paper introduces these new features for modal analysis, focusing on modeling procedures, input parameters, and examples of potential cost savings.