Welding simulations: assessment of welding residual ...

Welding simulations: assessment of welding

residual stresses and post weld heat treatment

Etienne Bonnaud and Jens Gunnars, Inspecta Technology AB

2016-09-281

Third Nordic Conference on Design and Fabrication of Welded Structures, 2016-09-29, Stockholm

Outline

2

Presentation of Inspecta

Overview of welding simulations

Case study 1: Pressure Vessel manufacture

• Bending before welding

• Welding before bending

Case study 2: Core Shroud Support of a Nuclear Power Plant

• Comparison between simulations and measurements

• Influence of Post Weld Heat Treatment

Case study 3: Two-stroke diesel engine support plate

• Root failure


Conclusion

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2016-09-283

Inspecta Group

Industries Thermal Power & Heating, Renewables, Nuclear Power,

Oil & Gas, Chemical, Pulp & Paper, Metals & Mining,

Manufacturing, Rail, Ports, Infrastructure, Real Estate

Service areasInspection, Certification, Testing, Design Review,

Quality Assurance, Revisions & Outages, Risk Management,

Advisory & Consultancy, Asset Integrity Engineering,

Advanced NDT, Life Time & Aging Management,

Contract R&D, Training

Countries Sweden, Finland, Norway, Denmark,

Poland, Estonia, Latvia, Lithuania

Revenue 200 MEUR

Employees 1600 engineers

Offices 80

2016-09-284

■ Main Competence Areas:

• Solid mechanics and structural integrity

• Materials technology, corrosion and welding

• Risk assessment and project management

■ Services Areas

• Design verification and optimization, design verification to codes and standards

• Structural and fatigue analysis, fracture mechanics, plasticity, buckling, dynamics

• Asset Integrity Engineering

• Inspection planning, corrosion management, in-depth degradation assessments

• Risk based inspection planning (RBI), Non-Intrusive Inspection (NII)

• Fitness-for-service (FFS) evaluation of defects and damage found at revisions

• Component life assessments, Life time extension strategies, structural integrity

• Project management

• Risk, reliability and safety assessments

• Welding technology, welding simulation

• Quality assurance, NDT requirements

• Contract R&D

Inspecta TECH – Advisory & Consultancy

Outline

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• Root failure


Conclusion

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Background – Weld Residual Stresses

Effects from welding processes:

- rapid heating and cooling cycles

- material submitted to compression and tension

- solidification and high temperatures

- effects from boundary conditions

- large plastic strains

- residual stresses arise - compressive and tensile

Consequences for component reliability:

increased hazard for

- stress corrosion cracking

- fatigue

- fracture

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Background – Weld Residual Stresses Measurements

7

Destructive methods – relaxation techniques:

• Hole drilling and measurement by strain gauge

• Incremental Deep Hole Drilling (IDHD) technique

• Contour method

• Slitting, Layer removal

Uncertainty in all methods is >20% in challenging cases

and assumptions for evaluation

Non-destructive methods – diffraction techniques:

• Neutron diffraction

• X-ray diffraction (standard, synchrotron high energy)

Research: Ultrasonic methods, magnetic methods

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Background – Weld Residual Stresses Modelling

Weld cross section:

- geometry

- bead size and numbers

Weld residual stresses simulation:

- thermal and mechanical analyses

- axial stress

- areas in compression and in tension

Material has experienced:

- heating and cooling

- compression and tension

- plastic strains

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Outline

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• Root failure


Conclusion

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Pressure Vessel – Analysis description

10

Bending downwards

Bending upwards

As welded

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Pressure Vessel – Results

11

Bending only

Hoop stress: -205 MPa -> 200 MPa

Welding only

Hoop stress: -301 MPa -> 421 MPa

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Pressure Vessel – Results: bending followed by welding

12

Bending Downwards: Hoop stress: -305 MPa -> 421 MPa

Bending Upwards: Hoop stress: -299 MPa -> 421 MPa

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Pressure vessel – Results: welding followed by bending

13

Bending Downwards: Hoop stress: -197 MPa -> 195 MPa

Bending Upwards: Hoop stress: -218 MPa -> 219 MPa

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Outline

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• Root failure


Conclusion

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Core Shroud Support – Set up and Model

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Core Shroud Support – Final Results

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Simulation result - field plot

Deep hole drilling measurement

Path plots

Core Shroud Support – Post Weld Heat Treatment

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• Circumferential stress at room temperature

• After buttering but before attachment weld

• Post Weld Heat treatment according to standards (7 hours at 620ºC)

Important stress release in the Carbon Steel

Before Post Weld Heat Treatment After Post Weld Heat Treatment

Outline

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• Root failure


Conclusion

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Support plate – root failure

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Support plate – Post Weld Heat Treatment

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Conclusions

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• Weld residual stress simulations give reliable results.

• Very good agreement between simulations and measurements confirms that both simulations and experiments give accurate results.

• Post Weld heat treatment is usually beneficial but can also be detrimental.

• 20 years of experience within weld residual stresses simulations at Inspecta.

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Thank you for your attention!

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Welding simulations: assessment of welding residual ...

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