Fatigue assessment of welded joints under variable amplitude loading using a novel notch stress approach

Nykänen, T.; Mettänen, Heli; Björk, Timo; Ahola, Antti

doi:10.1016/j.ijfatigue.2016.12.031

Cited by 21 publications

(19 citation statements)

References 20 publications

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“…All received results of the study on crack initiation are similar, namely, the fractures initiated in the notch root, and in considered welded joints, they have been at the surface in the vicinity of fusion line. Detailed studies, presented in magnified pictures, have revealed that Grey area is the range of predicted fatigue life defined by equation (14) and obtained for different values of safety factors. Advances in Materials Science and Engineering there were no dominating origins of fatigue cracks, and the initiation in both cases occurred over almost the entire length of the fusion line.…”

Section: Fractographic Investigation On Fatigue Crack Initiationmentioning

confidence: 99%

“…erefore, the welded joints of these structures are designed against fatigue using the effective notch stress approach [13][14][15][16][17][18][19], which is the most advanced fatigue design method being recommended by IIW [1]. is approach is based on the statement that stresses in the notch bottom are determined in the weld toe/root rounded with a fictive radius of 1 mm or 0.5 mm when the thickness of welded component is larger than 5 mm or less, respectively.…”

Section: Introductionmentioning

confidence: 99%

“…Material constant a � 0.5 was taken. e strain range Δε N was calculated according to equation (14). Obtained results are presented in Table 5 and shown on the plot (Figure 4).…”

mentioning

confidence: 99%

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Prediction of Fatigue Life of Welded Joints Made of Fine-Grained Martensite-Bainitic S960QL Steel and Determination of Crack Origins

Ślęzak

2019

Advances in Materials Science and Engineering

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Due to growing requirements connected with the utilization of advanced structures, nowadays the modern design processes are developed. One of the crucial issues considered in these processes is proper design of the joints against fatigue in order to fulfill a stated life of operation. In this study, the method of fatigue life prediction based on the criterion of permissible strain range in the notch root is presented. An engaged simplified model of fatigue life prediction was previously developed for mild and carbon steels. The evaluation made during the research has proven that this method can also be used for S960QL high-strength steel characterized by entirely different properties and structure. A considered theoretical model demonstrates satisfactory correlation with experimental data and safely describes the fatigue life of weldments. Furthermore, the predicted fatigue life of studied steel without welds shows great comparability with experimental data. The limit value of the strain range in the notch root was estimated. Below this value of strain, the fatigue life of welded joints is infinite, theoretically. Finally, the impact of the surface imperfections on the fatigue crack initiation was revealed. For paternal material, the origins of cracking were discovered at the places of nonmetallic scale particles. In welded joints, the fatigue cracks initiated at the whole length of the fusion line.

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Section: Fractographic Investigation On Fatigue Crack Initiationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Prediction of Fatigue Life of Welded Joints Made of Fine-Grained Martensite-Bainitic S960QL Steel and Determination of Crack Origins

Ślęzak

2019

Advances in Materials Science and Engineering

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“…Based on the S − N curves obtained from fatigue tests on actual welded joints, the extrapolated maximum structural stress in consideration of local geometries was utilized to predict life expectancy in the hot-spot stress method [6][7][8]. In order to concern detailed geometrical features and stress concentration effects, the maximum notch stress at the weld toe and weld root is treated as lifetime assessment parameter, proposed by the notch stress approach [9,10]. Similarly, the so-called E − N curves are expressed in terms of plastic and elastic strain energy density (SED) at the weld seam, and relevant number of cycles in the SED method to estimate fatigue life of welded joints [11,12].…”

Section: Introductionmentioning

confidence: 99%

An Energy-Based Approach for Fatigue Life Estimation of Welded Joints without Residual Stress through Thermal-Graphic Measurement

Xiao

et al. 2019

Applied Sciences

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The traditional methodologies for fatigue life assessment of welded joints strongly depend on geometries and surface characteristics, as well as time. In this paper, an energy-based approach, independent of structures though thermal-graphic measurement, was presented to predict life expectancy of welded joints, via limited number of tests. In order to eliminate the thermal elastic effect caused by the welding residual stress, annealing was first conducted on welded specimens. Both monotonic and cyclic tests for welded joints were implemented. Then, based on the thermal evolution of welded joints measured by the quantitative thermo-graphic method, an energy-based approach, taking the linear temperature evolution and the intrinsic dissipation into account, was employed on the fatigue life prediction of flat butt-welded joints. The estimated results showed good agreement with the experimental ones, and the energy tolerance to failure E c for different stress amplitudes was found to be constant.

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“…Based on the fatigue failure characteristics of welded structures, Radaj et al 16 and Hobbacher 17 adopted the hot spot stress analysis method and notch stress analysis method, which effectively eliminated the dispersion of the nominal stress of joints. Nyka¨nen et al 18 calculated the notch stress range under the constant amplitude load by using the master S-N curve and Miner's linear cumulative damage rule. Then, the fatigue strength of welded structures under variable amplitude loads was predicted by the notch stress method considering local stress ratio.…”

Section: Introductionmentioning

confidence: 99%

Analysis methods of the dynamic structural stress in a full-scale welded carbody for high-speed trains

Lü

Zheng

et al. 2018

Advances in Mechanical Engineering

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The calculation of the dynamic stress of a large and complex welded carbody is the key to the fatigue design and the durability evaluation of the carbody. Adopting the advanced structural stress based on the finite element method, a new finite element transformation method between random loads and dynamic stresses is proposed to be applied in carbody for high-speed trains. The multi-axial random dynamic load spectrums of full-scale carbody are obtained by the vehicle system dynamics method, and the shell finite element model of a full-scale carbody is established. Adopting the concept of a surrogate model, the finite element transformation relationship between the random load and the dynamic structural stress at concerned points is constructed by using multidisciplinary methods to compute the dynamic stress spectrums of concerned points at the welding seam, and dynamic structural stresses are compared and validated through carbody rig-test. The analysis methods of dynamic structural stress are performed systematically for a full-scale welded structure, which provides reference methods for the fatigue durability evaluation of large-scale welded structures.

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Fatigue assessment of welded joints under variable amplitude loading using a novel notch stress approach

Cited by 21 publications

References 20 publications

Prediction of Fatigue Life of Welded Joints Made of Fine-Grained Martensite-Bainitic S960QL Steel and Determination of Crack Origins

Prediction of Fatigue Life of Welded Joints Made of Fine-Grained Martensite-Bainitic S960QL Steel and Determination of Crack Origins

An Energy-Based Approach for Fatigue Life Estimation of Welded Joints without Residual Stress through Thermal-Graphic Measurement

Analysis methods of the dynamic structural stress in a full-scale welded carbody for high-speed trains

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