Implement Residual-Mass DDAM (2005-341A-R37)
- Newport News Shipbuilding
NSRP ASE Investment: $70K
The RM-DDAM (Residual Mass-Dynamic Design Analysis Method) implementation project performed efforts that would encourage industry adoption of the modification of the Navy’s standard shock analysis method DDAM (Dynamic Design Analysis Method). These efforts included establishing Navy acceptance requirements and conducting efforts to satisfy those requirements so that the Navy and industry as a whole could implement the new technology. RM-DDAM provides an efficient approach to satisfying the DDAM mass recovery requirements and additionally makes available a set of model quality metrics that improve design assessment and analysis optimization (e.g. guides selection of sufficient modes and diagnoses closely spaced mode conditions).
The study utilized two challenging FEM (Finite Element Method) models to test the RM extension to DDAM. For models without amplified response (resonant) modes RM-DDAM was found to issue predictions at all levels of mode recovery conservative relative to a legacy DDAM analysis with complete mode recovery. Conservatism decreases as the level of mode recovery is increased. RM-DDAM permitted a 90% reduction in the modal recovery effort at the cost of a modest 13% conservatism when used on a challenging large plate model.
Adoption of RM-DDAM will reduce analysis cost while increasing confidence in the analysis results. The study demonstrated RM-DDAM to be a valuable improvement to the legacy DDAM process. The study also found that assessment metrics that arise from RM-DDAM are better than the current technology as they reveal the presence and character of unwanted resonances and inform design refinement.
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