Evaluation of fatigue limit and harmless crack size of needle peened offshore structure steel F690

Kim, Min-Heon; Lee, Won-Gu; Kim, Cheol-Su; Takahashi, Koji; Handa, Mitsuru; Nam, Ki-Woo

doi:10.1007/s12206-021-2109-4

Cited by 6 publications

(5 citation statements)

References 16 publications

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“…With the surface residual stress using IH, 𝑎𝑎 ℎ𝑚𝑚𝑚𝑚 was able to obtain the same effect as the peening (shot, laser, ultrasonic, etc.) of the previous study [19][20][21][22][23][24][25]34]. Key Engineering Materials Vol.…”

Section: Fatigue Limitmentioning

confidence: 99%

“…The values of 𝑎𝑎 ℎ𝑚𝑚𝑚𝑚 were compared using the relationship between the maximum allowable crack depth (𝑎𝑎 𝑐𝑐𝑟𝑟𝑐𝑐 ), which is assumed to be the value of the safety factor, and the maximum detectable crack depth by non-destructive inspection (𝑎𝑎 𝑐𝑐𝑁𝑁𝐼𝐼 ). Kim et al reported that a semicircular surface defect with a depth of less than 0.8 mm could be rendered harmless by applying needle peening to offshore structural steel [21]. Nam et al [22] and Park et al [23] clarified that a semicircular surface defect with a depth of less than 0.3 mm could be rendered harmless by applying ultrasonic peening to Ni 12 % STS316L.…”

Section: Introductionmentioning

confidence: 99%

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Improvement of Safety and Reliability of SCM440 Steel with Induction Hardening

Lee,

Park,

Nam

2023

KEM

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In this study, structural SCM440 steel was used to investigate harmless crack size using compressive residual stresses by induction hardening (IH). The fatigue limits of base metal (BM), quenching–tempering (QT), and IH specimens were obtained. The harmless crack size (ahml) was evaluated using the fatigue limits, threshold stress intensity factor using the Ando equation, and the sum of the stress intensity factor using the Newman-Raju and API-RP579 equations. Because as the crack depth increases, the compressive residual stress rapidly decreases, the harmless crack was determined from the intersection of depth for all aspect ratios (As). However, the outermost surface crack did not intersect because the compressive residual stress (σr,s) on the surface is always present. The ahml values based on BM and QT are 1.04−1.45 and 1.02−1.39 mm, respectively. These values can be evaluated as the ∆Kth(l) of a long crack. ahml did not significantly depend on As. If the crack detected after nondestructive inspection (NDI) is not surface modified after repair, then NDI1 with a very high resolution must be performed.

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Section: Fatigue Limitmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Improvement of Safety and Reliability of SCM440 Steel with Induction Hardening

Lee,

Park,

Nam

2023

KEM

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“…Eq. 2 evaluated the fatigue limit of microcracks regardless of the steel type [22,23]. Therefore, the fatigue limit of the structure in service can be evaluated with the crack size detected by nondestructive inspection, and the safety of the structure can be secured.…”

Section: Static Fatigue Limit Of Cracked Specimenmentioning

confidence: 99%

Evaluation of Fatigue Life of Ultra-High-Strength Steel under Stress Corrosion Environment

Lee

et al. 2022

AMM

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Ultra-high-strength steel (UHSS) structures are exposed to corrosive environments during service, and hydrogen-assisted cracking (HAC) may occur owing to stress corrosion cracking and hydrogen embrittlement. In this study, the HAC threshold stress intensity factor and fatigue life of UHSS steel were evaluated by applying stress in a corrosive environment to prevent structural fracture. For specimen with semicircular slits by electric discharge machining, fatigue limit was obtained by static fatigue test under corrosive environment. The fatigue limit of the crack specimen was evaluated by the fatigue limit of the experiment and HAC threshold stress intensity factor, and comparative evaluation was performed. On the surface of cracks, grain boundaries were embrittled by corrosion, and grains were clearly observed. Meanwhile, cracks in the surface direction propagated slightly, unlike cracks in the depth direction. The static fatigue limit of UHSS (SKD11:HV670) was determined to be 400 MPa, and the fatigue limit of the crack specimen could be evaluated. The experimental results agreed well with the evaluation results.

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“…Therefore, if surface cracks can be made harmless in terms of the fatigue limit through peening, the reliability of the metal can be improved and the industrial usability of the part can be increased. Surface cracks of metal can be made harmless by various types of peening [13][14][15][16][17]. Tsuji et al were able to render harmless semicircular surface cracks with a depth of less than 0.2 mm using shot peening (SP) on carburized steel [13].…”

Section: Introductionmentioning

confidence: 99%

“…Tsuji et al were able to render harmless semicircular surface cracks with a depth of less than 0.2 mm using shot peening (SP) on carburized steel [13]. Semicircular surface cracks with depths of less than 0.3 mm and 0.8 mm could be rendered harmless by ultrasonic needle peening on STS316L [14] and DNV F690 [15], respectively. Park et al [16] and Takahashi et al [17] could rendered harmless the semicircular surface cracks smaller than 0.2 mm using SP and laser peening for A6061-T6 and Additive-Manufactured maraging steel (unaged), respectively.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Fatigue Limit Improvement and Harmless Crack Size of Maraging Steel Using Shot Peening

Yun,

Nam,

Nam

2024

KEM

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The fatigue strength of maraging steel, which is an ultra-high-strength steel, is relatively low, compared to that of conventional high-strength steel. The fatigue life of a structure is highly dependent on the surface conditions, because fatigue cracks generally start at the surface of the material. In particular, surface cracks considerably degrade the fatigue limit. To expand the application range of maraging steel, it is necessary to improve the fatigue limit, and render the surface cracks harmless. This study aims to investigate the effect of shot peening (SP) on the fatigue strength of maraging steel with surface cracks. The SP application introduced a compressive residual stress from the specimen surface to a depth of 170 μm, and increased the fatigue limit by 77 %. The estimated crack size that can be rendered harmless, based on fracture mechanics, is (0.170 − 0.202) μm in the range As = (1.0 − 0.1). The intersections of the harmless crack sizes were determined at depth. A semicircular surface crack below this value is harmless in terms of fatigue limit. The usefulness of non-destructive inspection (NDI) and non-damaging technology was evaluated in relation to ahml, aNDI, a25,50, and As. Thus, the SP process can improve the reliability of the maraging steel. Compressive residual stress is the dominant factor to improve fatigue strength and render the surface crack harmless.

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Evaluation of fatigue limit and harmless crack size of needle peened offshore structure steel F690

Cited by 6 publications

References 16 publications

Improvement of Safety and Reliability of SCM440 Steel with Induction Hardening

Improvement of Safety and Reliability of SCM440 Steel with Induction Hardening

Evaluation of Fatigue Life of Ultra-High-Strength Steel under Stress Corrosion Environment

Evaluation of Fatigue Limit Improvement and Harmless Crack Size of Maraging Steel Using Shot Peening

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