scholarly journals Fatigue Life Assessment of Welded Joints by Combined Measurements Using DIC and XRD

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5802
Author(s):  
Yixun Wang ◽  
Kazushi Ueda ◽  
Ryota Nagao ◽  
Seiichiro Tsutsumi
Keyword(s):  
Fatigue Life ◽  
Welded Joints ◽  
Local Strain ◽  
Life Assessment ◽  
Image Correlation ◽  
Initial Stresses ◽  
Mean Stress ◽  
Fatigue Initiation ◽  
Weld Toe ◽  
Hammer Peening

The existing methods of assessing the fatigue life of welded joints fail to consider local strain ranges and mean stress at the weld toe. The present work proposes a novel approach to assessing the fatigue life of welded joints by conducting measurements with digital image correlation (DIC) and X-ray diffraction (XRD) in combination. Local strain ranges at the weld toe of gusset welded joints were measured by DIC. Hammer peening was conducted on the welded joints to introduce different initial stresses. The influence of mean stress was investigated by considering initial residual stress measured by XRD and a perfect plastic material model. The fatigue experiment was carried out on specimens with and without hammer peening. The results showed that hammer peening could offset adverse welding deformation effectively, and introduce significant residual compressive stress. The fatigue failure life increased by more than 15 times due to hammer peening. The fatigue initiation life assessed by the proposed method was close to that based on nominal stress, indicating that the proposed method is reliable for predicting the fatigue initiation life of welded joints.

scholarly journals Generalized SCF Formula of Out-Of-Plane Gusset Welded Joints and Assessment of Fatigue Life Extension by Additional Weld

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1249
Author(s):  
Yixun Wang ◽  
Yuxiao Luo ◽  
Yuki Kotani ◽  
Seiichiro Tsutsumi
Keyword(s):  
Fatigue Life ◽  
Fatigue Resistance ◽  
Welded Joints ◽  
Life Extension ◽  
Leg Length ◽  
Notch Stress ◽  
Out Of Plane ◽  
Weld Toe ◽  
Effective Notch Stress ◽  
Geometric Effects

The existing S-N curves by effective notch stress to assess the fatigue life of gusset welded joints can result in reduced accuracy due to the oversimplification of bead geometries. The present work proposes the parametric formulae of stress concentration factor (SCF) for as-welded gusset joints based on the spline model, by which the effective notch stress can be accurately calculated for fatigue resistance assessment. The spline model is also modified to make it applicable to the additional weld. The fatigue resistance of as-welded and additional-welded specimens is assessed considering the geometric effects and weld profiles. The results show that the error of SCFs by the proposed formulae is proven to be smaller than 5%. The additional weld can increase the fatigue life by as great as 9.4 times, mainly because the increasing weld toe radius and weld leg length lead to the smaller SCF. The proposed series of S-N curves, considering different SCFs, can be used to assess the welded joints with various geometric parameters and weld profiles.

Equivalent crack approach for fatigue life assessment of welded joints

2015 ◽  
Vol 149 ◽  
pp. 144-155 ◽  
Author(s):  
Eeva Mikkola ◽  
Yukitaka Murakami ◽  
Gary Marquis
Keyword(s):  
Fatigue Life ◽  
Welded Joints ◽  
Life Assessment ◽  
Fatigue Life Assessment

Fatigue Design of Welded Joints by Local Approaches: Comparison between Fictitious Notch Rounding and Strain Energy Averaging

2007 ◽  
Vol 348-349 ◽  
pp. 449-452 ◽  
Author(s):  
Paolo Lazzarin ◽  
Filippo Berto ◽  
D. Radaj
Keyword(s):  
Welded Joints ◽  
Strain Energy ◽  
Control Volume ◽  
Local Strain ◽  
Stress Distributions ◽  
Good Correspondence ◽  
Load Carrying ◽  
Weld Toe ◽  
Weld Root ◽  
Coarse Meshes

The paper demonstrates the close correspondence between two local approaches to assess the fatigue strength of welded joints: Radaj’s approach based on fictitious notch rounding and a recently proposed approach based on the local strain energy density (SED) averaged over a given control volume. This volume surrounds the weld root or weld toe, both modelled as sharp (zero radius) V-notches with different opening angles. The two approaches are applied to load carrying and non-load carrying cruciform joints and the theoretical fatigue notch factors Kf are compared. The SED averaged over the control volume is determined from finite element models with very fine meshes, as typically designed to evaluate the intensity of the asymptotic stress distributions, and also from coarse meshes, showing a surprisingly good correspondence.

Creep-Fatigue Fracture of Dissimilar Metal Electron Beam Welded Joints at Elevated Temperature

1988 ◽  
Vol 110 (3) ◽  
pp. 212-218 ◽  
Author(s):  
M. Okazaki ◽  
Y. Mutoh ◽  
M. Yamaguchi
Keyword(s):  
Electron Beam ◽  
Fatigue Life ◽  
Welded Joints ◽  
Prediction Method ◽  
Strain Range ◽  
Local Strain ◽  
Base Metals ◽  
Dissimilar Metal ◽  
Creep Fatigue ◽  
Metal Electron

Creep-fatigue tests of dissimilar-metal electron beam welded joints between A387 Gr.22 ferritic low-alloy steel and AISI 405 ferritic stainless steel were carried out under strain-controlled cycling at a temperature of 873 K. It was found that the creep-fatigue life of a dissimilar metal welded joint was significantly shorter than those of its base metals. This resulted from the strain concentration on the AISI 405 side (with the lower deformation resistance.) It was also found that the hardness distribution was one of the important measures by which the local strain distribution was reflected. Furthermore, a simple prediction method for the creep-fatigue life of dissimilar metal welded joints was proposed based on the creep-fatigue life properties of its base metals by applying the strain range partitioning approach. The predicted lives were in good agreement with the experimental results.

scholarly journals Fatigue Life Estimation with Mean Stress Effect Compensation for Lightweight Structures—The Case of GLARE 2 Composite

Polymers ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 251 ◽  
Author(s):  
Michał Böhm ◽  
Karolina Głowacka
Keyword(s):  
Fatigue Life ◽  
Composite Structures ◽  
Life Assessment ◽  
Stress Effect ◽  
Mean Stress ◽  
Lightweight Structures ◽  
Fatigue Life Assessment ◽  
Current State ◽  
Fatigue Life Estimation ◽  
Material Information

This paper describes the current state-of-the-art in fatigue life assessment for lightweight composite structures with the use of the frequency domain fatigue life calculation method. Random stationary gaussian loading signals have been generated and served in the process of fatigue calculation. The material information that is being used in the calculation process has been obtained from literature for the Glare 2 composite. The effect of nonzero mean stress and different fiber orientations have been taken into account. The calculations have been performed for two mean stress compensation models by Goodman and Gerber. The proposed procedure gives satisfying results for the high-cycle fatigue region for Goodman and an overall good comparison in both regimes for the Gerber model.

scholarly journals Numerical investigation of the cope hole shape impact on fatigue life of welded joints in steel bridges

2019 ◽  
Vol 252 ◽  
pp. 07008
Author(s):  
Krzysztof Śledziewski
Keyword(s):  
Fatigue Life ◽  
Welded Joints ◽  
Hot Spot ◽  
Experimental Studies ◽  
Free Access ◽  
Steel Bridge ◽  
High Concentration ◽  
Hole Shape ◽  
Weld Toe ◽  
The Impact

Holes in the bridge girders are usually made at the joint of strips. In most cases, they are made when there is a need to make double-sided butt welds and in order to avoid welds crossing. Size of the hole is selected in order to allow full penetration of the strips across their whole width and also to ensure free access to the welds during NDT. Welded joints with holes, due to low fatigue life, are critical elements affecting durability of large-span steel bridge structures. Low fatigue life of joints with holes results mostly from high concentration of stresses near the weld toe caused by local reduction of cross-section. The paper covers parametric studies based on finite elements method in order to determine the impact of geometrical changes of the hole shape on distribution of stresses within probable areas of cracks initiation and durability of such joint. With reference to experimental studies results, four different holes geometries were analysed: semi-circle (conventional), triangle, parabola of second degree and oval. Assessment of the fatigue was performed using the so-called hot spot method, i.e. geometrical stresses. Results of the studies show that geometrical change of the hole shape affects the stresses concentration change, but it does not translate to the increase of fatigue life of such joint.

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