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© CADFEM 2016
FEA within Ship and Submarine Design James Underwood
Principal Naval Architect & Structures Group Manager,
BMT Defence Services Ltd
1st CADFEM ANSYS Simulation Conference, United Kingdom
2nd & 3rd November 2016 – Oxford Spires Hotel, Oxford
BMT Group Overview
A network of knowledge and resources
ENERGY & ENVIRONMENT
TRANSPORT DEFENCE3 sectors
• BMT Designers &
Planners
• BMT Defence
Services
• BMT Design &
Technology
• BMT Fleet
Technology
• BMT Hi-Q Sigma
• BMT Isis
• BMT Reliability
Consultants
• BMT Asia Pacific
(Indonesia)
• BMT Cordah
• BMT Oceanica
• BMT WBM
• BMT ARGOSS
• BMT Scientific
Marine Services
• BMT Fluid
Mechanics
• BMT Asia Pacific
(Malaysia)
• BMT Navcon
Defence EnergyEnvironment
• BMT Asia Pacific
(Hong Kong)
• BMT Asia Pacific
(Singapore)
• BMT Consultants
India
• BMT JFA
• BMT Ship &
Coastal Dynamics
• BMT WBM
(Machinery Group)
Ports,
Infrastructure
and Resources
Ship Design,
Surveys and
Vessel
Performance
• BMT Nigel Gee
• BMT SMART
• BMT Surveys
• Verweij & Hoebee
BMT Group
Structure - sector
BMT Defence Services
A subsidiary of BMT Group
• Established in 1988 in
Bath, UK,
• Two offices in Bath, with
a further three offices in
Fareham, Weymouth,
and Barrow-In-Furness.
Locations
285 people based
in Bath, UK
55 people based
in Fareham,
Weymouth and
Barrow, UK
BMT Defence Services
Services
NAVAL DESIGN & ENGINEERING
SYSTEMS ENGINEERING
ACQUISITION SUPPORT
COMBAT SYSTEMS
IN-SERVICE SUPPORT
HYDRODYNAMICS
TECHNICAL ASSURANCE
STRUCTURAL DESIGN & ANALYSIS
TECHNOLOGY MANAGEMENT
SOFTWARE DEVELOPMENT
HUMAN FACTORS
Whole Ship Stress Analysis
Global Stress Analysis
• Focus on stress analysis in relation to Classification
Society rules and prescribed reserve factors to ensure ship
safety at sea under varying loading conditions.
• Fatigue analysis of ship at sea under varying loading
conditions.
• FEA:
− Linear Elastic analysis of the whole ship under wave induced bending
moment;
− Load applied through application of forces to transverse frames along
the keel of the vessel or as surface pressure loads;
− Shell and Beam element modelling.
− Stress and buckling analysis of structure.
− Fatigue assessment of design details using sub-modelling with loading
derived from global model.
Images:
Flight Deck: http://www.public.navy.mil/surfor/ddg86/Pages/News-Archive.aspx
Bow Slamming: https://uk.pinterest.com/pin/484840716108123118/
Whole Ship Stress Analysis
Whole Ship Ultimate Strength Assessment
Ultimate Bending Strength Assessment
• Focus on ultimate limit state analysis for vessel under
wave induce bending moment in both the intact and
damage condition.
• FEA
− Non-linear collapse analysis of the hull structure under global
bending moment;
− Shell element model;
− Load applied by applying pure bending moment to longitudinal
section of vessel;
− Model includes weld induced manufacturing imperfections and
residual stresses.
− Structure will progressively fail from region in compression
around side shell until complete failure occurs.
Images: MOL Comfort: http://dev.twentytwowords.com/large-cargo-ship-snaps-in-two-in-rough-
seas-both-pieces-remain-afloat-5-pics/
Frigate FEA: Benson S. Progressive Collapse Analysis of Lightweight Ship Structures.
Doctoral Thesis; November 2011.
Destroyer FEA: Downes J, Ham WL, Dow RS. Assessment of the residual strength of a
lightweight naval vessel. Proceedings of Practical Design of ships and Offshore Structures
2013 (PRADS 2013).
Whole Ship Ultimate Strength Assessment
Whole Ship Ultimate Strength Assessment
Structural Integration
• Replenishment at Sea (RAS) of liquid and solid stores to re-
store front line warships from auxiliaries within a hostile
area.
• Auxiliary lines run from bespoke RAS Mast to RAS
connection points on receiving ship.
• Loading required to contend with line loads whose tension
is maintained by series of active winches.
• Structural capability to comply with Classification Society
rules based on an allowable stress approach in relation to
prescribed reserve factors.
• FEA:
− Linear elastic analysis for peak stress in structure of mast and its
integration up to two decks below weather deck.
− Shell and beam element modelling.
− Buckling assessment of mast structure.
− Fatigue analysis of mast structure.
− Model built using ANSYS Mechanical APDL, though subsequent study
showed significant modelling time savings by using ANSYS SpaceClaim
and Workbench.
RAS Mast
Structural Integration
RAS Mast
Structural Integration
RAS Mast
Submarine Pressure Hull Design
• Pressure hull design undertaken to required dive depth
multiplied by required safety factors.
• Focus on ultimate collapse strength of the pressure hull
and end closure structures.
• Failure due to instability of the pressure hull or end
closure dome.
Concept end closure studies:
• Current end closures of large diameter submarines are
either hemispherical or torospherical in form,
manufactured through the welding of segments of very
thick plate into which double curvature has been cold
pressed.
• Current process is therefore very complex and
expensive.
• BMT investigated concepts surrounding alternative end
closures including flat sandwich bulkhead and faceted
dome form.
End Closure Analysis
Submarine Pressure Hull Design
End Closure Analysis
Submarine Pressure Hull Design
End Closure Analysis
Submarine Pressure Hull Design
End Closure Analysis
Submarine Pressure Hull Design
End Closure Analysis
Copyright Statement
Copyright © 2016 by BMT Defence Services
All rights reserved. No part of this publication may be reproduced,
distributed, or transmitted in any form or by any means, including
photocopying, recording, or other electronic or mechanical methods,
without the prior written permission of BMT Defence Services.
Where content has not been produced by BMT Defence Services, we
have sought the appropriate authorisation for its use and does not
constitute an infringement of copyright.
Thank You.