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Shock analysis of a stern ramp using Dynamic Design Analysis Method

Yunbo Yu ; Meng Zhang
Göteborg : Chalmers tekniska högskola, 2016. 77 s. Report. X - Department of Shipping and Marine Technology, Chalmers University of Technology, Göteborg, Sweden, 2016.
[Examensarbete på avancerad nivå]

In naval battles, a shock load caused by underwater explosion leads to malfunction of the equipment onboard, which makes naval ships vulnerable and lead to a loss of the ability to accomplish their missions. Shock analysis of the critical equipment is therefore imperative for naval ships. Among the solutions for shock resistant design, field tests are prohibitively expensive and time-consuming when applied to large naval equipment under harsh and varied shock loads. Hence, the dynamic design analysis method (DDAM) is developed as an alternative method, which can be performed in commercial finite element software. DDAM is theoretically based and confirmed by laboratory and large scale field testing and has been a sound technique for naval applications over decades. The aim of the thesis is to evaluate the performance of a naval ship stern ramp under non-contact underwater explosion using DDAM and study the parameter sensitivity for DDAM performed in FE software. Three methods for shock analysis including the static G method, DDAM and transient analysis are compared from the perspective of theory but emphasis is on DDAM. Prior to the analysis of the stern ramp, two commercial softwares (ANSYS and FEMAP) are compared in terms of implementation of DDAM by case studies. The difference and discrepancy are evaluated and ANSYS is chosen for the analysis of the stern ramp. The two phases of the DDAM analysis, modal analysis and the response spectrum analysis, are then conducted to obtain the structural response. Results under shock loads from the three directions (vertical, fore and aft, athwartships) are investigated in three initial simulations. The vertical case turns out to be the most critical one. The static G method is also used to analyze the stern ramp as a comparison. Afterwards, parameters that influence the results are evaluated through a series of simulations with the results of the critical case as a reference. Feasible reinforcements are also explored. From the simulations, it is found that the number of modes in use has the most significant influence on the results. Advice for DDAM parameter settings are given according to this. The possible reinforcement for the shock resistant design are also recommended.



Publikationen registrerades 2016-09-28.

CPL ID: 242461

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