Fatigue strength of welded and high frequency mechanical impact (HFMI) post-treated steel joints under constant and variable amplitude loading

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Fatigue strength of welded and high frequency mechanical impact (HFMI) post-treated steel joints under constant and variable amplitude loading. / Leitner, Martin; Ottersböck, M.; Pußwald, S.; Remes, H.

In: Engineering Structures, Vol. 163, 15.05.2018, p. 215-223.

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@article{73f9c4dc1b244307b7388e060bdad35f,
title = "Fatigue strength of welded and high frequency mechanical impact (HFMI) post-treated steel joints under constant and variable amplitude loading",
abstract = "This study presents fatigue test results of longitudinal stiffener specimens in as-welded and high frequency mechanical impact (HFMI) post-treated condition under both constant amplitude loading (CAL) and variable amplitude loading (VAL). The experiments incorporate mild steel S355 and high-strength steel S700 samples at load stress ratios of R = 0.1 and R = −1 respectively. VAL tests are performed utilizing a straight-line distribution with a sequence length of 2 ⋅ 105 load-cycles and an omission level of 19{\%} of the maximum stress range. The test results reveal a significant benefit of the HFMI-treatment under CAL. On the contrary, the increase in fatigue strength is majorly reduced in case of VAL. X-ray residual stress measurements for the investigated mild steel S355 specimens demonstrate that even at comparably minor load stress ranges, a certain relaxation of the HFMI-treatment induced local compressive residual stress state at the weld toe occurs. This phenomenon contributes to the decrease of the benefit by the HFMI-treatment under VAL compared to CAL. An evaluation of specified damage sums on the basis of the determination of an equivalent stress range for VAL reveals that damage sums between D = 1.0 and D = 0.5 are well applicable for a conservative fatigue assessment on the basis of the IIW-recommended fatigue design curves. However, facilitating a lightweight component design by considering experimental test results of HFMI-treated joints under CAL, a reduced specified damage sum of D = 0.3, or even of D = 0.2 in case of fluctuating mean stress states, is suggested for the fatigue assessment to avoid non-conservative results.",
keywords = "Equivalent stress range, Fatigue strength, HFMI-treatment, Specified damage sum, Variable amplitude loading, Welded joints",
author = "Martin Leitner and M. Ottersb{\"o}ck and S. Pu{\ss}wald and H. Remes",
year = "2018",
month = "5",
day = "15",
doi = "10.1016/j.engstruct.2018.02.041",
language = "English",
volume = "163",
pages = "215--223",
journal = "Engineering Structures",
issn = "0141-0296",
publisher = "Elsevier BV",

}

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TY - JOUR

T1 - Fatigue strength of welded and high frequency mechanical impact (HFMI) post-treated steel joints under constant and variable amplitude loading

AU - Leitner, Martin

AU - Ottersböck, M.

AU - Pußwald, S.

AU - Remes, H.

PY - 2018/5/15

Y1 - 2018/5/15

N2 - This study presents fatigue test results of longitudinal stiffener specimens in as-welded and high frequency mechanical impact (HFMI) post-treated condition under both constant amplitude loading (CAL) and variable amplitude loading (VAL). The experiments incorporate mild steel S355 and high-strength steel S700 samples at load stress ratios of R = 0.1 and R = −1 respectively. VAL tests are performed utilizing a straight-line distribution with a sequence length of 2 ⋅ 105 load-cycles and an omission level of 19% of the maximum stress range. The test results reveal a significant benefit of the HFMI-treatment under CAL. On the contrary, the increase in fatigue strength is majorly reduced in case of VAL. X-ray residual stress measurements for the investigated mild steel S355 specimens demonstrate that even at comparably minor load stress ranges, a certain relaxation of the HFMI-treatment induced local compressive residual stress state at the weld toe occurs. This phenomenon contributes to the decrease of the benefit by the HFMI-treatment under VAL compared to CAL. An evaluation of specified damage sums on the basis of the determination of an equivalent stress range for VAL reveals that damage sums between D = 1.0 and D = 0.5 are well applicable for a conservative fatigue assessment on the basis of the IIW-recommended fatigue design curves. However, facilitating a lightweight component design by considering experimental test results of HFMI-treated joints under CAL, a reduced specified damage sum of D = 0.3, or even of D = 0.2 in case of fluctuating mean stress states, is suggested for the fatigue assessment to avoid non-conservative results.

AB - This study presents fatigue test results of longitudinal stiffener specimens in as-welded and high frequency mechanical impact (HFMI) post-treated condition under both constant amplitude loading (CAL) and variable amplitude loading (VAL). The experiments incorporate mild steel S355 and high-strength steel S700 samples at load stress ratios of R = 0.1 and R = −1 respectively. VAL tests are performed utilizing a straight-line distribution with a sequence length of 2 ⋅ 105 load-cycles and an omission level of 19% of the maximum stress range. The test results reveal a significant benefit of the HFMI-treatment under CAL. On the contrary, the increase in fatigue strength is majorly reduced in case of VAL. X-ray residual stress measurements for the investigated mild steel S355 specimens demonstrate that even at comparably minor load stress ranges, a certain relaxation of the HFMI-treatment induced local compressive residual stress state at the weld toe occurs. This phenomenon contributes to the decrease of the benefit by the HFMI-treatment under VAL compared to CAL. An evaluation of specified damage sums on the basis of the determination of an equivalent stress range for VAL reveals that damage sums between D = 1.0 and D = 0.5 are well applicable for a conservative fatigue assessment on the basis of the IIW-recommended fatigue design curves. However, facilitating a lightweight component design by considering experimental test results of HFMI-treated joints under CAL, a reduced specified damage sum of D = 0.3, or even of D = 0.2 in case of fluctuating mean stress states, is suggested for the fatigue assessment to avoid non-conservative results.

KW - Equivalent stress range

KW - Fatigue strength

KW - HFMI-treatment

KW - Specified damage sum

KW - Variable amplitude loading

KW - Welded joints

UR - http://www.scopus.com/inward/record.url?scp=85042628985&partnerID=8YFLogxK

U2 - 10.1016/j.engstruct.2018.02.041

DO - 10.1016/j.engstruct.2018.02.041

M3 - Article

VL - 163

SP - 215

EP - 223

JO - Engineering Structures

JF - Engineering Structures

SN - 0141-0296

ER -

ID: 26044822