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Reliable Fatigue Design of Welded Joints following the Eurocode-3
Conceptual Analysis and Possible Improvements
G. Coussan (1) , J-M. Nianga (2) and N. Recho (3)
(1) & (2) HEI, 13 rue de toul; 59046 Lille cedex, France
(3) EPF, 3bis rue lakanal, 92330 Sceaux, France
« ESIS TC2 Oxford 2012 », 4th of April 2012, COUSSAN.G, guillaume.coussan@hei.fr page 1 of 13
Plan => Introduction => Numerical Simulation =>
Reliability analysis => Conclusion
Plan
• Introduction
• Parameters choice and mesh box
• Eurocode problem
• Simulation results and fatigue design
• Geometrical stress equation
• Reliability approach
• Conclusion
« ESIS TC2 Oxford 2012 », 4th of April 2012, COUSSAN.G, guillaume.coussan@hei.fr page 2 of 13
Plan => Introduction => Numerical Simulation =>
Reliability analysis => Conclusion
« ESIS TC2 Oxford 2012 », 4th of April 2012, COUSSAN.G, guillaume.coussan@hei.fr page 3 of 13
Geometrical stress determination according to eurocode 3. The geometrical stress corresponds to the value obtained by extrapolation at the weld toe of a straight line (the dot line on the figure) formed by the two stress values crossing the stress curve at the points of abscissa 0,4T and 1,0T.
Plan => Introduction => Numerical Simulation =>
Reliability analysis => Conclusion
« ESIS TC2 Oxford 2012 », 4th of April 2012, COUSSAN.G, guillaume.coussan@hei.fr page 4 of 13
Detail class and SN curve extract from Eurocode 3 (part 1-9). Thoses curves are used to determine the fatigue lifetime with the estimated stress level.
Plan => Introduction => Numerical Simulation =>
Reliability analysis => Conclusion
« ESIS TC2 Oxford 2012 », 4th of April 2012, COUSSAN.G, guillaume.coussan@hei.fr page 5 of 13
Parameters choice (T is the plate thickness, Rc is the weld toe radius, e is the weld thickness and θ is the weld angle) and mesh-box.
Plan => Introduction => Numerical Simulation =>
Reliability analysis => Conclusion
« ESIS TC2 Oxford 2012 », 4th of April 2012, COUSSAN.G, guillaume.coussan@hei.fr page 6 of 13
Extracted results from one of the simulations (Rc = 0,5mm ; θ = 60° ; e = 14mm ; pure traction ) showing the problem with eurocode definition of geometrical stress, the Kt value beeing below 1.
Plan => Introduction => Numerical Simulation =>
Reliability analysis => Conclusion
« ESIS TC2 Oxford 2012 », 4th of April 2012, COUSSAN.G, guillaume.coussan@hei.fr page 7 of 13
New method to determine the geometrical stress relie on a 2% stress gap between concave and convex configuration.
Plan => Introduction => Numerical Simulation =>
Reliability analysis => Conclusion
« ESIS TC2 Oxford 2012 », 4th of April 2012, COUSSAN.G, guillaume.coussan@hei.fr page 8 of 13
Fatigue design to study the parameters effect on the new geometrical stress.
Parameters System answers
Rc (mm) theta (°) e (mm) loading (% moment)
X1 (mm) Sigma X1 (Mpa) Kt
Configuration 1 0,5 30 8 0 0,37 86,6 1,73
Configuration 2 0,5 30 14 50 0,37 79,8 1,60
Configuration 3 0,5 60 8 50 1,23 67,0 1,34
Configuration 4 0,5 60 14 0 1,30 72,7 1,45
Configuration 5 5 30 8 50 2,89 54,4 1,09
Configuration 6 5 30 14 0 3,02 55,7 1,11
Configuration 7 5 60 8 0 5,27 52,5 1,05
Configuration 8 5 60 14 50 5,17 51,7 1,03
Configuration 9 0,5 30 8 50 0,37 79,8 1,60
Configuration 10 0,5 30 14 0 0,37 86,7 1,73
Configuration 11 0,5 60 8 0 1,25 72,5 1,45
Configuration 12 0,5 60 14 50 1,25 67,1 1,34
Configuration 13 5 30 8 0 3,00 56,0 1,12
Configuration 14 5 30 14 50 2,90 54,3 1,09
Configuration 15 5 60 8 50 5,11 52,0 1,04
Configuration 16 5 60 14 0 5,37 52,0 1,04
Medium configuration 2,75 45 11 25 3,19 55,9 1,12
Plan => Introduction => Numerical Simulation =>
Reliability analysis => Conclusion
« ESIS TC2 Oxford 2012 », 4th of April 2012, COUSSAN.G, guillaume.coussan@hei.fr page 9 of 13
Direct parameters effect on Kt.
Plan => Introduction => Numerical Simulation =>
Reliability analysis => Conclusion
« ESIS TC2 Oxford 2012 », 4th of April 2012, COUSSAN.G, guillaume.coussan@hei.fr page 10 of 13
Plan => Introduction => Numerical Simulation =>
Reliability analysis => Conclusion
« ESIS TC2 Oxford 2012 », 4th of April 2012, COUSSAN.G, guillaume.coussan@hei.fr page 11 of 13
Equation that allows a prediction of the new geometrical stress.
Plan => Introduction => Numerical Simulation =>
Reliability analysis => Conclusion
« ESIS TC2 Oxford 2012 », 4th of April 2012, COUSSAN.G, guillaume.coussan@hei.fr page 12 of 13
Plan => Introduction => Numerical Simulation =>
Reliability analysis => Conclusion
« ESIS TC2 Oxford 2012 », 4th of April 2012, COUSSAN.G, guillaume.coussan@hei.fr page 13 of 13
Conclusion: -New method to determine geometrical stress with reliability analysis. -Better consideration of geometrical configuration. -Fatigue design possibly without numerical simulation for the geometrical stress determination.
Studies to come: -Taking into account non-linear effects. -Feeding reliability analysis with experimental data. Used software: CAST3M, Abaqus, Statgraphics, Excel.
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