Welding simulations: assessment of welding residual stresses and post weld heat treatment Etienne Bonnaud and Jens Gunnars, Inspecta Technology AB Third Nordic Conference on Design and Fabrication of Welded Structures, 2016-09-29, Stockholm 1
Outline 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 Influence of Post Weld Heat Treatment Conclusion 2
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Outline 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 Influence of Post Weld Heat Treatment Conclusion 5
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 6
Background Weld Residual Stresses Measurements 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 7
Background Weld Residual Stresses Modelling Weld cross section: - geometry - bead size and numbers Material has experienced: - heating and cooling - compression and tension - plastic strains Weld residual stresses simulation: - thermal and mechanical analyses - axial stress - areas in compression and in tension 8
Outline 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 Influence of Post Weld Heat Treatment Conclusion 9
Pressure Vessel Analysis description As welded Bending upwards Bending downwards 10
Pressure Vessel Results Bending only Hoop stress: -205 MPa -> 200 MPa Welding only Hoop stress: -301 MPa -> 421 MPa 11
Pressure Vessel Results: bending followed by welding Bending Downwards: Bending Upwards: Hoop stress: -305 MPa -> 421 MPa Hoop stress: -299 MPa -> 421 MPa 12
Pressure vessel Results: welding followed by bending Bending Downwards: Bending Upwards: Hoop stress: -197 MPa -> 195 MPa Hoop stress: -218 MPa -> 219 MPa 13
Outline 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 Influence of Post Weld Heat Treatment Conclusion 14
Core Shroud Support Set up and Model 15
Core Shroud Support Final Results Simulation result - field plot Path plots Deep hole drilling measurement 16
Core Shroud Support Post Weld Heat Treatment Before Post Weld Heat Treatment After Post Weld Heat Treatment 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 17
Outline 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 Influence of Post Weld Heat Treatment Conclusion 18
Support plate root failure 19
Support plate Post Weld Heat Treatment 20
Conclusions 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. 21
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