Modified damping using projection methods for explicit transient problems

Explicit transient methods are applicable to problems where inertial forces are negligible due to a sufficiently slow rate of deformation. Accelerated loading rates can improve numerical efficiency at the risk of introducing high amplitude vibrations. Damping is required to suppress the numerically undesirable dynamic response. The commonly used mass proportional damping most strongly attenuates lower frequency modes, thus impeding the overall progress of large deformations. A new modification of mass proportional damping makes use of a projection method such that damping force is orthogonal to a selected deformation mode. This allows the selected mode to be undamped. The new method is implemented into an explicit finite element program, and its application to problems typical of metal forming applications demonstrate its success.