Fatigue strength assessment of laser welded thin-walled joints made of mild and high strength steel

Marulo, Giuseppe; Baumgartner, J. Craig; Frendo, Francesco

doi:10.1016/j.ijfatigue.2016.11.016

Cited by 22 publications

(24 citation statements)

References 18 publications

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“…In the FE analysis, the whole joint was supposed to be constituted of a single and homogeneous material, having the same properties of the base material; it is well known that the material constituting a welded joint does not show homogeneous properties (see, e.g., Marulo et al 49 ) and this was a mere simplification.…”

Section: Analysis Of Results: Fatigue Life Assessmentmentioning

confidence: 99%

Fatigue life assessment of welded joints under sequences of bending and torsion loading blocks of different lengths

Frendo

Marulo

Chiocca

et al. 2020

Fatigue Fract Eng Mat Struct

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In this work, the nominal stress concept, the notch stress approach and two critical plane approaches are used to analyse the fatigue endurance of a pipeto-plate welded joint subjected to complex loading histories. Both the pipe and the plate were made of S355JR steel. Starting from already known fatigue endurance curves obtained for the same specimens under pure bending and pure torsion, a first series of tests was conducted, in which specimens were loaded in bending for a given fraction of the estimated life and then in torsion until failure. A similar series of tests was then carried out by changing the loading order: specimens were firstly loaded in torsion for a given fraction of the estimated endurance and then in bending until failure. The whole test campaign was repeated for two different fractions of the estimated life, that is, 0.3 and 0.45, respectively. After that, additional three series of tests were carried out, in which the specimens were subjected to consecutive sequences of bending and torsion blocks of different lengths (short, medium and long, respectively); the relative length of the bending and torsion block in each series was determined in order to produce the same damage. The experimental results, in terms of total damage at failure, were analysed using the Palmgren-Miner hypothesis. For all the assessment methods, the characteristic endurance curves were firstly calibrated on the basis of finite element (FE) analyses and of the experimental results obtained under pure bending and pure torsion loadings. The observed damage at failure resulted always greater than 0.5 for all the employed methods and greater than 1 for most of the tests. The different methods gave similar results, with the critical plane methods giving a slightly more stable damage at failure and a correct determination of the failure location. For all the methods, the damage at failure slightly reduces as the block length shortens. K E Y W O R D Scritical plane, loading blocks, multiaxial fatigue, nominal stress, notch stress, welded joints

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Section: Analysis Of Results: Fatigue Life Assessmentmentioning

confidence: 99%

Fatigue life assessment of welded joints under sequences of bending and torsion loading blocks of different lengths

Frendo

Marulo

Chiocca

et al. 2020

Fatigue Fract Eng Mat Struct

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“…It is stated in the literature that the laser-welded butt-joints have a better fatigue strength compared to the convectional welded butt-joints [3,37,38]. The dierences are due different geometry and microstructure, as seen in Figure 2.…”

Section: Laser Welding Fatigue In Generalmentioning

confidence: 99%

Overview of laser-welded thin-walled joints fatigue performance and a statistical method for defect analysis

Kokko

Vaara

Kuivaniemi

et al. 2020

RakMek

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Welding always has a deteriorating effect on fatigue strength in structures under dynamic loading. Weld joints induce discontinuity in structure geometry and the microstructure. Welding induced discontinuity, and defects allow for potential fatigue cracks that lead to the failure of welded parts or structures. The laser welding process differs from conventional arc welding in process and joint type. The most significant advantage in laser welding comes from the deep penetrating mode of welding, which also brings challenges to the soundness of the weld. The benefits of laser welding are most evident in the manufacture of sheet metal products such as sandwich panels. In literature, laser welding is generally dealt with by using different parts of the overall process without taking the fatigue point of view into account. In this article, the process of laser welding is discussed, while keeping fatigue strength in perspective. The fatigue data of laser welded joints is studied in order to find defect distribution that explains fatigue strength distribution in tests. The suitability of traditional fatigue assessment for laser welding is also discussed.

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“…Because of increased computational power, such methods are more easily applicable nowadays. The point (PM) and line (LM) methods—based on the gradient of the stress acting perpendicular to the expected crack path—have gained especial interest, judging by the variety of investigated applications 8–29 …”

Section: Introductionmentioning

confidence: 99%

Requirements for stress gradient‐based fatigue assessment of notched structures according to theory of critical distance

Braun

Müller

Milaković

et al. 2020

Fatigue Fract Eng Mat Struct

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Notches, local stress raisers within structural components, are one of the most important locations for fatigue crack initiation. It is well known that fatigue is governed by the effective stresses in the vicinity of notches. Within this study, differences in prediction accuracy between different types of theory of critical distance methods, that is, point and line methods, are systematically investigated in conjunction with a sensitivity study regarding mesh refinement, assumed strength hypothesis and material behaviour. For this purpose, a finite element analysis parameter study on notched structures is performed and recommendations for the application of stress gradient methods are presented.Difference in effective stress of up to 30%, and hence a significant difference in fatigue life (e.g., 185% for a slope of S-N curve of k = 4), is found for typical notch shapes, for example, in welded joints. K E Y W O R D Scritical distance, fatigue at notches, finite element analysis, notch fatigue analysis, notch sensitivity, stress gradient

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Fatigue strength assessment of laser welded thin-walled joints made of mild and high strength steel

Cited by 22 publications

References 18 publications

Fatigue life assessment of welded joints under sequences of bending and torsion loading blocks of different lengths

Fatigue life assessment of welded joints under sequences of bending and torsion loading blocks of different lengths

Overview of laser-welded thin-walled joints fatigue performance and a statistical method for defect analysis

Requirements for stress gradient‐based fatigue assessment of notched structures according to theory of critical distance

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