A parametric study on creep–fatigue strength of welded joints using the linear matching method

• The parametric study is implemented using the linear matching method and FEM.
• Creep–fatigue strength of the steel AISI type 316N(L) weldments of types 1 and 2.
• Function for cycles to failure is dependent on geometric parameters of weld profile.
• Function for cycles to failure is dependent on dwell period and normalised moment.
• Function for FSRF dependent on dwell period takes into account the effect of creep.

This paper presents a parametric study on creep–fatigue strength of the steel AISI type 316N(L) weldments of types 1 and 2 according to R5 Vol. 2/3 Procedure classification at 550 °C. The study is implemented using the Linear Matching Method (LMM) and is based upon a latest developed creep–fatigue evaluation procedure considering time fraction rule for creep-damage assessment. Parametric models of geometry and FE-meshes for both types of weldments are developed in this way, which allows variation of parameters governing shape of the weld profile and loading conditions. Five configurations, characterised by individual sets of parameters, and presenting different fabrication cases, are proposed. For each configuration, the total number of cycles to failure N in creep–fatigue conditions is assessed numerically for different loading cases including normalised bending moment M∼ and dwell period Δt. The obtained set of N is extrapolated by the analytic function, which is dependent on M∼,Δt and geometrical parameters (α and γ). Proposed function for N shows good agreement with numerical results obtained by the LMM. Thus, it is used for the identification of Fatigue Strength Reduction Factors (FSRFs) intended for design purposes and dependent on Δt, α, γ.