The peak stress method combined with 3D finite element models for fatigue assessment of toe and root cracking in steel welded joints subjected to axial or bending loading

Meneghetti, Giovanni; Guzzella, Carlo; Atzori, B.

doi:10.1111/ffe.12171

Cited by 40 publications

(23 citation statements)

References 31 publications

(127 reference statements)

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“…It is worth recognising that the mesh pattern of Fig. 46,47 It should be noted that Eqs 14 and 15 have to be recalibrated in the case of FE meshes consisting of higher-order elements or characterized by significantly different mesh patterns as compared to the reference one reported in Fig. The standard FE mesh patterns adopted in the case of sharp V-notches can be found in previous contributions 43,44 ; • the mesh density ratio a/d must exceed 3 in order to have K Ã FE ¼ 1:38±3%, where a is the semi-crack length.…”

Section: T H E P E a K S T R E S S M E T H O D T O R A P I D L Y E V mentioning

confidence: 99%

Rapid finite element evaluation of the averaged strain energy density of mixed‐mode (I + II) crack tip fields including the T‐stress contribution

Campagnolo

Meneghetti

Berto

2016

Fatigue Fract Eng Mat Struct

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The strain energy density (SED) averaged over a material dependent control volume has been demonstrated to control fracture and fatigue behaviour of different materials in many engineering design situations. A method to rapidly calculate the averaged SED at the tip of long cracks under in‐plane mixed mode (I + II) loading has been recently proposed. It was based on the peak stresses evaluated from finite element (FE) analyses, according to the peak stress method (PSM). The aim of this work is to extend this FE approach to short cracks. In the present paper short cracks are distinguished from long cracks by considering that the stress fields within the control volume of short cracks are no longer governed solely by the stress intensity factors (SIFs), but the contribution of higher order terms, and primarily the T‐stress, becomes significant to estimate the averaged SED. Therefore the averaged SED is calculated using the linear elastic nodal stresses evaluated by FEM either at the crack tip, to account for the SIF contribution, and at selected FE nodes of the crack free edges, to include the T‐stress contribution. The proposed approach is referred to as nodal stress approach. The advantage of the nodal stress approach is two‐fold: there is no need of mesh refinements in the close neighbourhood of the points of singularity, so that coarse FE meshes can be adopted; moreover, geometrical modelling of the control volume in FE models is no longer necessary. Infinite plates weakened by central small cracks subjected to mixed mode I + II loading and a lap joint geometry have been analysed taking into consideration different crack lengths, mode mixities and average finite element sizes of the employed meshes. A comparison between approximate values of the averaged SED according to the nodal stress approach and those derived directly from the FE strain energy adopting very refined FE meshes has been successfully performed within a range of applicability.

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Section: T H E P E a K S T R E S S M E T H O D T O R A P I D L Y E V mentioning

confidence: 99%

Rapid finite element evaluation of the averaged strain energy density of mixed‐mode (I + II) crack tip fields including the T‐stress contribution

Campagnolo

Meneghetti

Berto

2016

Fatigue Fract Eng Mat Struct

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“…Fatigue assessment of butt‐welded joints made of structural steels according to the peak stress method. Comparison between the design scatter band reported in Refs and experimental results analysed in the present paper.…”

Section: Assessment Of Weld Toe and Weld Root Fatigue Failuresmentioning

confidence: 81%

“…It should be noted that in the case of as‐welded joints, Eq. simplifies to:

normalΔ σ_{italice italicq, italicpeak} = f_{italicw 1} \cdot normalΔ σ_{11, italicpeak}

…”

Section: Introductionmentioning

confidence: 99%

Fatigue strength assessment of partial and full‐penetration steel and aluminium butt‐welded joints according to the peak stress method

Meneghetti

Campagnolo

Berto

2015

Fatigue Fract Eng Mat Struct

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A B S T R A C T In fatigue design of welded joints, the local approach based on the notch stress intensity factors (NSIFs) assumes that the weld toe profile is a sharp V-notch having a tip radius equal to zero, while the root side is a pre-crack in the structure. The peak stress method (PSM) is an engineering, FE-oriented application of the NSIF approach to fatigue design of welded joints, which takes advantage of the elastic peak stresses from FE analyses carried out by using a given mesh pattern, where the element type is kept constant and the average element size can be chosen arbitrarily within a given range. The meshes required for the PSM application are rather coarse if compared with those necessary to evaluate the NSIFs from the local stress distributions. In this paper, the PSM is extended for the first time to butt-welded joints in steel as well as in aluminium alloys, by comparing a number of experimental data taken from the literature with the design scatter bands previously calibrated on results relevant only to fillet-welded joints. A major problem in the case of butt-welded joints is to define the weld bead geometry with reasonable accuracy. Only in few cases such geometrical data were available, and this fact made the application of the local approaches more difficult. Provided the local geometry is defined, the PSM can be easily applied: a properly defined design stress, that is, the equivalent peak stress, is shown (i) to single out the crack initiation point in cases where competition between root and toe failure exists and (ii) to correlate with good approximation all analysed experimental data.Keywords butt-welded joints; fatigue design; local approaches; peak stress method (PSM); strain energy density (SED). N O M E N C L A T U R E2a = length of the lack of penetration c w = parameter which accounts the influence of the nominal load ratio d = mean size of a finite element e 1 , e 2 = parameters for the determination of the strain energy density (SED) f w1 , f w2 = weight parameters of the peak stresses h = bead height k = inverse slope of the design scatter band r,θ = polar coordinates t = thickness of the welded plate w toe = bead width BC = Boundary conditions E = elastic modulus EBM = Electron beam welding FE = Finite element FEM = Finite element method K 1 , K 2 = mode I and II notch stress intensity factors (NSIFs) K Ã FE = normalised K 1 in the application of the peak stress method K ÃÃ FE = normalised K 2 in the application of the peak stress method

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“…(3) and (4). In the recent literature, the PSM has been coupled to the averaged strain energy density (SED) criterion to assess the fatigue strength of welded joints subjected to axial [15,36,38,39], torsion [37,40] and multiaxial [41,42] loading conditions.…”

Section: Residual Stress Analysis On Welded Joints By Means Of Numerimentioning

confidence: 99%

Rapid Calculation of Residual Notch Stress Intensity Factors (R- NSIFs) by Means of the Peak Stress Method

Colussi¹,

Ferro²,

Berto³

et al. 2018

Residual Stress Analysis on Welded Joints by Means of Numerical Simulation and Experiments

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The intensity of the residual singular stress distribution can be quantified by the residual notch stress intensity factor (R-NSIF), which might be a useful stress parameter to include in local approaches for fatigue strength assessments of welded joints. In order to calculate the residual stress fields by means of welding process simulations, the mesh adopted in numerical models has necessarily to be very fine. Unfortunately, the nonlinear and transient behavior of the welding simulation makes numerical analyses extremely demanding in terms of computational time, particularly, if large welded structures and/or multipass welds have to be simulated. In this scenario, the use of methods aimed at reducing the computational effort to estimate local stresses and strains in welded structures can be effective. Among these, the peak stress method has been proposed to estimate the notch stress intensity factors (NSIFs) at sharp V-notches, using coarse finite element patterns. In this work, the peak stress method (PSM) has been used to calculate the R-NSIF of a full penetration welded T-joint. It has been shown that the PSM can successfully be used to estimate R-NSIFs values, provided that the stress redistribution induced by plasticity in the zone very close to the notch tip is negligible.

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The peak stress method combined with 3D finite element models for fatigue assessment of toe and root cracking in steel welded joints subjected to axial or bending loading

Cited by 40 publications

References 31 publications

Rapid finite element evaluation of the averaged strain energy density of mixed‐mode (I + II) crack tip fields including the T‐stress contribution

Rapid finite element evaluation of the averaged strain energy density of mixed‐mode (I + II) crack tip fields including the T‐stress contribution

Fatigue strength assessment of partial and full‐penetration steel and aluminium butt‐welded joints according to the peak stress method

Rapid Calculation of Residual Notch Stress Intensity Factors (R- NSIFs) by Means of the Peak Stress Method

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