Effects of Welding on Energy Dissipation in a Watertight Bulkhead
Abstract
Surface combatants face a wide range of threats and perhaps the most destructive of these is the underwater explosion generated by a mine or a torpedo. The shock wave generated by an underwater explosion can cause severe damage or even a catastrophic failure. As the shock wave bits the ship, its energy is transmitted through the structural members of the ship. The purpose of this thesis is to examine how this energy is transmitted through the watertight bulkhead of a DDG and how the welded stiffeners affect the bulkhead's energy damping properties. To investigate the effects of the welding, the bulkhead was modeled both as a finite element model and as a scaled physical model. The modes and natural frequencies of the bulkhead were first calculated using PATRAN and NASTRAN. Using a one half scale model, the bulkhead was excited using random noise over a 250 Hz frequency span while measuring the accelerations at 60 points along the panel. These measured accelerations were then used to calculate the frequency response of the bulkhead and the damping ratios as a function of frequency. By plotting the damping ratios versus frequency for each measurement point on the bulkhead, there can be a better understanding of how energy waves propagate through a welded structure.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 2003
- Accession Number
- ADA417478
Entities
People
- Jon S. Erskine
Organizations
- Naval Postgraduate School