The Dynamic Design Analysis Method (DDAM) is a methodology developed by the U.S. Navy for testing shock loading from underwater explosions. Both Altair HyperWorks and SOLIDWORKS Simulation Premium can test your designs using this method. In this blog, we’ll take a look at some of the key features in both tools.
In order to run an analysis using DDAM, the following four steps must be completed in the following order:
- Modal Analysis
- Shock Load Generation
- Response Spectrum Analysis
- Results Reporting
Step 1: Modal Analysis
Both HyperWorks and SOLIDWORKS Simulation calculate resonant frequencies and mass participations. Below are the modal results of the same 3’ x 4’ aluminum sheet mounted on the deck of a ship.
With the same geometry and setup, the results will be roughly equivalent between these two tools.
Many users may find that it’s easier to make design changes and run these studies in SOLIDWORKS Simulation due to its CAD-embedded interface. On the other hand, if models are large, some of the advanced meshing features in HyperWorks can help you save time overall.
Step 2: Shock Load Generation
After you retrieve the modal analysis results from the previous step you must then use these results to generate a shock load. HyperWorks gives you a special utility to generate the shock load using the DDAM utility shown below.
Since this utility is not available in SOLIDWORKS Simulation, resourceful Simulation users will need to consult the equations listed in the NRL Memorandum Report 1396 in order to generate their shock loads. I’ve created a spreadsheet as an example of how this could be done.
Step 3: Response Spectrum Analysis
Once you have the shock load from the previous step, you can now run a Response Spectrum Analysis and measure peak stresses and deflections. As expected, the results from running this final study look practically identical between both tools.
Step 4: Results Reporting
Both software packages are capable of producing results that should satisfy the requirements of DI-ENVR-81030.
On the other hand, some further degree of customization of the SOLIDWORKS Simulation results and exports will likely be needed to make sure the data is recognized, and the requirements are completely satisfied. SOLIDWORKS Simulation can export a printout of the input data (SS_Sample.DAT) in several formats to include details like node point locations.
Nodal forces and connector forces may be missing from these exports and may need to be exported manually from some plots in the SOLIDWORKS Simulation interface.
The comprehensive suite of tools available with Altair HyperWorks allows users to run their analysis using DDAM from start to finish. The DDAM utility is a great bonus for users who don’t want to wrestle with determining their shock loads. Some of the advanced results reporting capability give users flexibility when it comes to submitting their results.
Also, Altair’s suite of tools allows users to run shape optimizations on their DDAM projects. Due to many of these advantages.
For users who are ok with generating their own shock loads and who prefer the intuitive SOLIDWORKS environment, SOLIDWORKS Simulation Premium can also do the job. This tool makes it easy to test design changes since studies can be automatically re-meshed and re-run after using SOLIDWORKS to change features and dimensions in your model.
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