Department of Solid Mechanics. Pål Efsing & Bo Alfredsson SKC Convent

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1 Department of Solid Mechanics Pål Efsing & Bo Alfredsson SKC Convent

2 Current activities at the department of Solid Mechanics include - Continuum mechanics - Materials mechanics - Fracture mechanics - Reliable structures - Much of the effort lies in the gray zone between Materials Science and Structural Mechanics - Better understanding of mechanical properties and behavior of components as well as ageing effect assist the industry strive for safer, longer, and more efficient operation of the currently operated NPPs Solid Mechanics track within Master program Engineering Mechanics with 25+ graduates annually PhD program with 3 4 graduates annually

3 Track Solid Mechanics in Engineering Mechanics master program Red text = Compulsary course Blue background = Solid mechanics course White background = Course given by another department Theory and Methodology of Science, 4 hp Re. Method. Engng Mech, 3.5 hp Applied elasticity with FEM, 9 hp FEM modelling 8 hp Material Mechanics, 9 hp Autumn year 1 FEM project, 3 hp Testing Techniques in Solid Mechanics, 6 hp Fracture Mechanics and Fatigue, 9 hp Introduction to Biomechanics, 9 hp Dynamic Problems in Solid Mechanics, 7. 5 hp Pool course, 6 hp 9 hp Computational Material Mechanics, 6 hp Fatigue, Reliability and Design, 9 hp Spring year 1 Autumn year 2

4 Three on-going Ph. D. projects in the area: Modeling of Inter Granular Stress Corrosion Cracking in LWR-environments Improved continuum mechanics models into IG-SCC modelling Project started 1 of September 2012 PhD-Student Michel Sedlak In part sponsored by SKC

5 Modelling of IG-SCC Cohesive element behaviour

6 Mechanical modelling of IG-SCC: Couplings between physical processes Crack tip load K(σ(P, ),a) Adsorption rate at tip h(k,c) Degradation Φ 1 (c ad ) Propagation a(k,φ 1 ) Bulk material E,ν Diffusion & Concentration c(u y (K,E,ν),a,h)

7 Residual strains and stresses in welded components in Alloy 690 A number of studies have revealed a sensitivity to EAC for the current choice of Nickel based replacement material for SG-tubing as well as thick walled components - Investigation of the relationship between local plastic strain estimated by EBSD and local nano-indentation hardness in Alloy 690, Presented at 17 th Env Deg in Materials in Nuclear Power Systems, Augusti 2015 PhD student Rickard Shen Project start in August 2011 Project sponsored by E.On, Fortum and Vattenfall

8 Thermal ageing/ferritic decomposition under long term operation A fine network of δ-ferrite in an austenite matrix is formed during solidification of cast stainless steels Microstructure, composition, propensity for thermal aging (TA), and macroscopic effect on mechanical properties varies with manufacturing technique and heat treatment Diffusion causes spinodal decomposition of δ-ferrite and precipitation of secondary phases Mechanical properties and especially fracture resistance is lowered so that ductile fracture can no longer be assumed, limiting service life of components Project sponsored by SSM, RAB, FKA, OKG and Studsvik Project start in 2012, PhD student Martin Bjurman

9 Influence of irradiation on the structural integrity of Reactor Pressure Vessels: Influence of Nickel and Manganese on both the ductile to brittle transition area as well as ductile material properties Co-operation with SSM, Ringhals AB, Rolls Royce, Reactor physics/kth, CTH, SCK/CEN/Belgium, Univ. Of Manchester and Oxford University etc. Recently started program on Unstable matrix defects in irradiated Low Alloy Steel Researcher: Magnus Boåsen

10 Other relevant activities: Analysis of microstructural evolution and the mechanical properties of highly irradiated stainless steel - Radiation induced stress corrosion cracking, IASCC in SS - Swelling of SS due to internal transmutation ex. Boron to Helium - Oxide formation and oxide/metal interface reactions at highly irradiated stainless steels Co-operation with Ringhals, OKG and FKA, SSM, VTT/Finland, Pacific Northwest Labs in Richland/WA. & EPRI, Palo Alto/CA - Partially to be coupled to KTH effort with-in MåBIL Hydrogen embrittlement in high strength steels - Environmental effects of fracture mechanical properties Collaboration with steel and component manufacturers