Abstract
The Peak Stress Method (PSM) is an engineering, FE-oriented application of the notch stress intensity factor (NSIF) approach to fatigue design of welded joints, which takes advantage of the singular linear elastic peak stresses from FE analyses with coarse meshes. Originally, the PSM was calibrated by using 3D, eight-node brick elements, taking advantage of the submodeling technique. Recently, the PSM has been calibrated by using ten-node tetra elements, which are able to directly discretize complex 3D geometries without the need for submodels. The PSM was validated for pure axial or bending loadings as well as pure torsion loadings; recently it has been extended to multiaxial loadings by adopting a design stress, the so-called equivalent peak stress, in conjunction with a reference design fatigue curve. After having briefly recalled the calibration of the PSM with tetra elements, the paper presents some applications of the PSM relevant to steel plate-to-tube welded details of industrial interest under in-phase bending-torsion fatigue loadings. Experimental data have been re-analysed using the PSM based on tetra elements. Eventually a good agreement between experimental and theoretical results has been obtained in terms of fatigue crack initiation location as well as total fatigue life.
Highlights
In the fatigue design of welded joints, the approaches based on Notch Stress Intensity Factors (NSIF) assume both the weld toe and the weld root as sharp V-notches, i.e. with a notch tip radius ρ = 0 and notch opening angles typically equal to 135° and 0°, respectively [1,2]
The peak stress method (PSM) employs the singular, linear elastic peak stresses evaluated at the toe and root sides by means of FE analyses with coarse meshes to rapidly estimate the mode I, mode II and mode III NSIFs
The 3D Peak Stress Method (PSM) has been calibrated by using ten-node tetra elements, which are able to discretize complex 3D geometries, making the PSM applicable directly without the need for submodels
Summary
https://doi.org/10.1051/matecconf/201930019002 notch tip can be quantitatively described by means of the relevant NSIFs, which can be defined according to Gross and Mendelson [3] by means of Eq (1). In previous expression, λi is the stress singularity exponent tied to mode I, II and III for i = 1, 2 and 3, respectively, which depends on the notch opening angle 2α, while the stress components σθθ, τrθ and τθz are calculated along the notch bisector line (θ =0 in Fig. 1a).
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