ANSYS and its use in Shipbuilding & Naval Architecture

Uses of Finite Element Software in Shipbuilding

ANSYS is a general purpose software used for different type of structural analyses and also for
various Engineering fields. Presently different types of analyses are trying to highlight which are
commonly used for Shipbuilding and Offshore structures such as Bulk Carrier, Tanker, Jack Up,
Floating Dock, Naval Vessel etc.
The new Bulk Carrier and Tanker common Rules under the guidance of IACS has specially
emphasized on detail structural calculation by using Finite Element Method. The new
guidelines have come for the Direct Strength Analysis (DSA) procedure in which 35 Load cases
have to be simulated due to wave load as well as Cargo load variation for 3-Hold computer
model. By using ANSYS Macro DSA can be done for Bulk Carrier and Tanker structure. With
ANSYS software the entire DSA time has been reduced drastically.
The ultimate strength of the ship hull girder beyond which the hull will collapse can be analyzed
by using ANSYS. Hull girder failure is caused by buckling, ultimate strength and yielding of
plating and attached stiffeners, which participate in the longitudinal strength. A methodology for
computing the ultimate moment carrying capacity of ship hull girder when subjected to
longitudinal bending moment (vertical hogging or sagging moment); horizontal at any section
are developed. So, the FEM nonlinear analysis has carried out by using ANYS 11, to investigate
the failure.
The Free vibration analysis has been performed for a Passenger vessel to estimate the natural
frequencies and mode shapes by using ANSYS. The hull girder frequencies were compared
with the engine, shaft, propeller frequencies etc, to check for any possible resonance. The
analysis was done for three loading conditions. 1. Light Ship Condition. 2. Fully loaded
departure from port. 3. Fully loaded arrival to port, which cover the major variation of loading
during voyage. Engine room has been separately modeled and analyzed to capture the local
vibration mode in addition with the full ship analyses.
A Non-linear Transint dynamic analysis has been done to determine the damage for the
collisions between two ships. A supply vessel with a specified velocity hits the corner of an
offshore barge. The implicit solver of ANSYS has been utilised for the reqiured analysis. The
geometric, material and contact non-linear properties are being considered.
Wave slamming is an important parameter for designing the forward part of the Ship structure.
The slamming loads are highly dynamic in nature, characterized by very short duration of the
load, usually 10-20 milli-seconds. Transient dynamic analysis carried out for nearly 2000 cases
and proposes a simple method based on this study, for design of structures subjected to
slamming loads. The method also provides for accounting any acceptable value of permanent
deformation criteria for plate thickness and presence of in-plane stresses.
Ships and Submarines structures in their fighting role are susceptible to Underwater shock
generated due to explosion of torpedoes, mines, depth charges etc. The damage inflicted by
Non-Contact Underwater explosion consists of direct shock wave damage of hull, whipping
damage of keel, mechanical damage to onboard equipment and associated systems. The use
of ANSYS and its capability, backed up with the in-house developed software, for Underwater
Explosion analysis of structures.
ANSYS is used for docking study, Crane foundation analysis, bollard analysis, Mast analysis,
local structure stress analysis etc. In a nutshell, ANSYS can help the Ship and Offshore
Structure Designer to design the structure safely with minimum design time utilisation. The
scantlings can be optimized and the new innovative design can be achevied with the help of
ANSYS.