Dynamic Design Analysis Method

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Dynamic Design Analysis Method (DDAM) is a form of shock spectrum analysis that estimates the dynamic response of a component to shock loading caused by the sudden movement of a vessel. DDAM is used primarily to validate designs for U.S. Navy use. DDAM simulates the interaction between the shock-loaded component and its fixed structure. Utilizing NEi Nastran's DDAM users can determine the characteristics of underwater explosion phenomena including the effects of shock waves (depth charges, mines, missiles and torpedoes), surface ship or submarine body response to shock loading and application of shock spectra to component design.

NEi Nastran offers the best DDAM solution in the industry. It is simple to setup and does not involve restarts or the use of DMAP. Engineers can use DDAM to analyze the shock response at the mountings of various shipboard equipment such as masts, propulsion shafts, rudders, exhaust uptakes and other critical structures.

Methodology

User supplied shock coefficients are used to perform shock excitation calculations and generate shock spectrum data... you simply set up a normal modes analysis and add a single bulk data entry with all the parameters on it. Additionally, a modal cutoff percentage may be supplied to terminate calculations when a specific modal mass is reached. Shock spectrum data is then applied using standard modal summation conventions.

Importance

All mission-essential equipment onboard surface ships and submarines must be qualified for shock loads. NEi Nastran is fast, accurate, and fully NAVSEA compliant unlike other FEA packages. For example some programs are not in full NAVSEA compliance because they derive invariants like von mises stress from summed direct components versus calculating the invariant directly and then summing it.

Other Features

• Proven fully NAVSEA compliant technology.
• NEi Nastran has one of the most powerful Lanczos eigensolvers on the market allowing the analysis of huge models over 3 million DOF even when a large number if modes are required.
• Modal database/restart feature allows running a separate modal analysis and then using the results in separate DDAM runs skipping the time consuming modal extraction phase.
• Modal data sort by increasing modal effective mass, speeds processing time and reduces memory and disk space requirements.
• Extensive diagnostics ensure accuracy of results.
• Specialized DDAM training class available either onsite or at our new training facility. Click here to learn more!

Typical Applications

• Depth charge analysis
• Exhaust uptake design
• Mast analysis
• Military ship component design
• Mine detonation analysis
• Missile detonation analysis
• Propulsion shaft design
• Rudder optimization
• Shock design
• Torpedo detonation analysis