Assessment of fatigue strength of steel butt-welded joints in as-welded condition – Alternative approaches for curve fitting and mean stress effect analysis

2015 ◽  
Vol 44 ◽  
pp. 288-310 ◽  
Author(s):  
Timo Nykänen ◽  
Timo Björk
Keyword(s):  
Fatigue Strength ◽  
Curve Fitting ◽  
Welded Joints ◽  
Stress Effect ◽  
Mean Stress ◽  
Effect Analysis ◽  
Mean Stress Effect ◽  
Alternative Approaches

S–N curves for fatigue life estimation of friction stir welded 19501 aluminum alloy T-joint

2018 ◽  
Vol 233 (2) ◽  
pp. 664-674
Author(s):  
Prakash Chandra Gope ◽  
Harshit Kumar ◽  
Himanshu Purohit ◽  
Manish Dayal
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Life ◽  
Fatigue Strength ◽  
Weld Zone ◽  
Stress Effect ◽  
Mean Stress ◽  
Friction Stir ◽  
Fracture Surfaces ◽  
Mean Stress Effect ◽  
Metallic Bonding

In this study, the mechanical properties and fatigue life of 19501 aluminum alloy friction stir welded T-joint is investigated. Tensile properties of friction stir welded joint show that there is a marginal reduction of about 5% in strength and ductility as compared to unwelded 19501 aluminum alloy. Fatigue test results of T-joint specimen at two stress ratios of 0 and -1 show that there is a reduction of 15% in fatigue strength due to change of stress ratio from -1 to 0. Also, higher variation is seen in fatigue strength in low cycle zone than the high cycle zone. Effect of mean stress on fatigue life is discussed on the basis of different mean stress effect models. Morrow’s mean stress effect model is found to be better than other models. Micrographs from the fracture surfaces of retreating side, mid weld zone, and advancing side of the T-joint indicates that fracture surfaces are cleavage fracture. Different sizes of inter-metallic bonding are seen in the micrographs, which indicate that fracture is initiated due to breaking of the brittle inter-metallic bonding.

scholarly journals Mean Stress Effect on the Axial Fatigue Strength of DIN 34CrNiMo6 Quenched and Tempered Steel

Metals ◽  
2018 ◽  
Vol 8 (4) ◽  
pp. 213 ◽  
Author(s):  
Luis Pallarés-Santasmartas ◽  
Joseba Albizuri ◽  
Alexander Avilés ◽  
Rafael Avilés
Keyword(s):  
Fatigue Strength ◽  
Stress Effect ◽  
Mean Stress ◽  
Mean Stress Effect ◽  
Quenched And Tempered Steel ◽  
Tempered Steel ◽  
Axial Fatigue

scholarly journals Application of the S-N Curve Mean Stress Correction Model in Terms of Fatigue Life Estimation for Random Torsional Loading for Selected Aluminum Alloys

Materials ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 2985
Author(s):  
Michał Böhm ◽  
Krzysztof Kluger ◽  
Sławomir Pochwała ◽  
Mariusz Kupina
Keyword(s):  
Fatigue Life ◽  
Fatigue Strength ◽  
Stress Effect ◽  
Mean Stress ◽  
Torsional Loading ◽  
Correction Model ◽  
Life Estimation ◽  
Mean Stress Effect ◽  
Fatigue Life Estimation ◽  
The Mean

The paper presents the experimental fatigue test results for cyclic constant amplitude loading conditions for the case of the torsion of the PA4 (AW-6082-T6), PA6 (AW-2017A-T4) and PA7 (AW-2024-T3) aluminum alloy for a drilled diabolo type test specimen. The tests have been performed for the stress asymmetry ratios R = −1, R = −0.7, R = −0.5 and R = −0.3. The experimental results have been used in the process of a fatigue life estimation performed for a random generated narrowband stress signal with a zero and a non-zero global mean stress value. The calculations have been performed within the time domain with the use of the rainflow cycle counting method and the Palmgren−Miner damage hypothesis. The mean stress compensation has been performed with the S-N curve mean stress model proposed by Niesłony and Böhm. The model has been modified in terms of torsional loading conditions. In order to obtain an appropriate R = 0 ratio S-N curve fatigue strength amplitude, the Smith−Watson−Topper model was used and compared with literature fatigue strength amplitudes. The presented solution extends the use of the correction model in terms of the torsional loading condition in order to obtain new S-N curves for other R values on the basis of the R = −1 results. The work includes the computational results for new fatigue curves with and without the mean stress effect correction. The results of the computations show that the mean stress effect plays a major role in the fatigue life assessment of the tested aluminum alloys and that the method can be used to assess the fatigue life under random conditions.

scholarly journals Mean Stress Effect on Fatigue Strength in Gray Cast Iron and Its Mechanism

2012 ◽  
Vol 98 (8) ◽  
pp. 442-449 ◽  
Author(s):  
Shinobu Kawaguchi ◽  
Ryo Hamanaka ◽  
Tetsuya Tagawa
Keyword(s):  
Cast Iron ◽  
Fatigue Strength ◽  
Gray Cast Iron ◽  
Gray Cast ◽  
Stress Effect ◽  
Mean Stress ◽  
Mean Stress Effect

Mean Stress Effect on Fatigue of Welded Joint in FPSOs

2006 ◽  
Author(s):  
Bin Zhang ◽  
Torgeir Moan
Keyword(s):  
Fatigue Life ◽  
Fatigue Strength ◽  
Residual Stresses ◽  
Stress Effect ◽  
Mean Stress ◽  
Initial Condition ◽  
Mean Stress Effect ◽  
Structural Details ◽  
The Mean ◽  
Mean Stresses

This paper deals with the mean stress effect on the fatigue life of welded joints in FPSOs. Mean stresses in structural details of FPSOs are composed of residual stresses and mean stresses induced by external service loading conditions. Mean stresses, both the residual stresses and those induced by external load, affect on the fatigue life of structural details. Fatigue strength decreases as tensile mean stress increases. Under compressive mean stresses, fatigue lives are increased. Different fatigue analysis procedures to account for mean stress effect, i.e. JBP, JTP, DNV CN30.7 and IIW procedure, are used to compare the fatigue test data of different specimens representing different typical welded connections in ship-shaped structures from HHI in Korea. In this paper these procedures are compared and an improved procedure explicitly considering of the mean stress effect is also proposed. The fatigue strength of welded joints of FPSO is affected by the initial condition as well as possible redistribution (shake-down) of the residual stresses. The initial condition of welding residual stress and its re-distribution by static preload and cyclic load in the small scale specimens are evaluated with FE analyses and analytical equations, also compared with the test results obtained from measurement based on ordinary sectioning method.

Dislocation mechanisms of mean stress effect on cyclic plasticity

2004 ◽  
Vol 46 (7-8) ◽  
pp. 363-373
Author(s):  
Hai Ni ◽  
Zhirui Wang
Keyword(s):  
Cyclic Plasticity ◽  
Stress Effect ◽  
Mean Stress ◽  
Mean Stress Effect
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