Multiaxial fatigue in welded structural details in ship ... Source pictures: Google.com . 3 Metocean...

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1 Multiaxial fatigue in welded structural details in ship and offshore structures Delft University of Technology Maritieme Innovatie Markt 2015 Paula van Lieshout MSc

Transcript of Multiaxial fatigue in welded structural details in ship ... Source pictures: Google.com . 3 Metocean...

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Multiaxial fatigue in welded structural details in ship and offshore structures Delft University of Technology Maritieme Innovatie Markt 2015 Paula van Lieshout MSc

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Cyclic loading

Fluctuating stresses/strains

Crack initiation

Crack growth/ propagation

Failure/Costs of

maintenance

Multiaxial fatigue Phenomenon description of fatigue

Low Cycle Fatigue

High Cycle Fatigue

Source pictures: Google.com

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Metocean analyses

Hydrodynamic analyses

Global structural response

Local structural response

Fatigue analyses

General overview General approach of fatigue problems

Source pictures: Google.com

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• Principal stresses change size and direction during a load cycle

• Structural geometry or loading induced

• The process of welding introduces additional uncertainties

• Weld material, Base material, Heat Affected Zone (HAZ)

• Nominal stress, Hot spot Stress, Notch Stress

• Mean/Residual stress

Multiaxial fatigue Multiaxiallity in welded structures

Sources: Maddox, S.J., 2010; SBM Offshore; Google.com; DNV –RP-C203, 2012

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Multiaxial fatigue in welded structures What is the problem?

Source: Sonsino, 2009

Overestimation 1:15!?

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• Uniaxial fatigue approaches provide non-conservative results for multiaxial fatigue

problems

• Multiaxial fatigue methods are mainly developed by the automotive and aerospace

industry

• Thin plated structures

• Different material types

• Often non-welded or different weld types and welding techniques are applied

• Existing multiaxial fatigue approaches require complex calculations and it is difficult to

make a physical interpretation of them

Multiaxial fatigue in welded structures What is the problem?

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• The results obtained with existing multiaxial fatigue methods show large variations in their

fatigue lifetime estimates

• There is no consensus on which method(s) should be used

• There is insufficient validation with experimental data for marine structures

Multiaxial fatigue in welded structures What is the current state-of-the-art?

Sources: pictures Backstrom & Marquis, 2004; Google.com

? Predicted mean life (cycles)

Experim

enta

l lif

e (

cycl

es)

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• Identify details sensitive to non-proportional multiaxial fatigue in a ship/offshore structure

• Make a selection of models for multiaxial fatigue analyses

• Carry out their experimental validation with a specimen which is representative for the

maritime industry (e.g. dimensions, material type, configuration)

• Recommend an approach for the assessment of non-proportional multiaxial fatigue in

ship/offshore structures

• Improve

• Develop a simplified approach for practical application

Multiaxial fatigue in welded structures Research goals and objectives

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Scope of work

Source pictures: Carpinteri & Spagnoli, 2009; Dong, 2009; FGB, 2015; Google.com

Project content

Scope of work

Fundamental Experimental Numerical

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Involvement of industrial practice

• The project obtains governmental STW funding (which is supported by 10 Dutch

industrial partners) and additionally as a Joint Industry Project (JIP) by international

industrial partners

My PhD research in a wider context

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Multiaxial fatigue in welded structural details in ship and offshore structures Delft University of Technology Maritieme Innovatie Markt 2015 Paula van Lieshout MSc