Improvement of fatigue limit by shot peening for high‐tensile strength steel containing a crack in the stress concentration zone

Houjou, Keiji; Takahashi, Koji; Ando, Kotoji

doi:10.1108/17579861311321726

Cited by 17 publications

(18 citation statements)

References 8 publications

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“…Shot peening is a surface treatment process used to produce a beneficial compressive residual stress layer and modify the fatigue strength of metals by impacting a surface with high-velocity spherical media [1] [2]. However, specimens without welded joints were used in these studies.…”

Section: Introductionmentioning

confidence: 99%

Fatigue Limit Prediction and Estimation for the Crack Size Rendered Harmless by Peening for Welded Joint Containing a Surface Crack

Fueki¹,

Takahashi²,

Houjou³

2015

MSA

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In this study, the effects of portable pneumatic needle-peening (PPP) on the bending fatigue limit of a low-carbon steel SM490A welded joint containing a semi-circular slit on the weld toe were investigated. PPP was applied to the specimens with a semi-circular slit with depths of a = 0.4, 0.8, 1.2, and 1.6 mm. Then, three-point bending fatigue tests were carried out under R = 0.05. The fatigue limits of low-carbon steel welded specimens containing a semi-circular slit were increased for peened specimens compared with non-peened specimens. Peened specimens having a semicircular slit with a depth of a = 1.2 mm had high fatigue limits, almost equal to those of the non-slit peened specimens. It was concluded that a semi-circular slit with a depth of less than a = 1.2 mm can be rendered harmless by peening. Then, the fatigue improvement by peening was predicted. The fatigue limits before and after peening could be estimated accurately by using a modified Goodman diagram considering the effects of residual stress, stress concentration, and Vickers hardness. Moreover, the maximum depth of a semi-circular slit that can be rendered harmless by PPP was estimated based on fracture mechanics assuming that the semi-circular slit was equivalent to a semi-circular crack. The prediction results were almost consistent with the experimental results.

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Section: Introductionmentioning

confidence: 99%

Fatigue Limit Prediction and Estimation for the Crack Size Rendered Harmless by Peening for Welded Joint Containing a Surface Crack

Fueki¹,

Takahashi²,

Houjou³

2015

MSA

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“…Recently, several studies have been published on the fatigue fracture behaviour of peened cracked materials. [21][22][23][24][25][26] Typical examples of the experimental results are shown in Figures 2-4. 21 The material is HV470 spring steel with a width (2w) and thickness (t) of 10 mm and 3 mm.…”

Section: Experimental Results Used For Analysismentioning

confidence: 99%

“…The precrack that was rendered harmless was defined as the fatigue limit of the SP precrack specimen that was not less than 95% of the fatigue limit of the SP smooth specimen. [21][22][23][24][25][26] The threshold stress intensity factor range (ΔK th(l) ) of R = 0 for a large crack was 6.09 MPa ffiffiffiffi m p…”

Section: Experimental Results Used For Analysismentioning

confidence: 99%

Analysis on peculiar fatigue fracture behaviour of shot peened metal using new threshold stress intensity factor range equation

Ando

Kim

Nam

2020

Fatigue Fract Eng Mat Struct

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A shot‐peened specimen with a precrack exhibits the following peculiar fatigue fracture behaviour. (1) Precracks can be rendered harmless by peening, even though the precrack reduced the fatigue limit by approximately 20%–60% of the nonpeened specimen. (2) When shot‐peened specimens were fractured at a higher stress than the fatigue limit, most specimens were fractured from outside the precracked part. (3) In most run‐out specimens, stage II (tensile type) nonpropagating cracks were observed. Why were nonpropagating cracks initiated and arrested? To explain the above fatigue behaviours, a new threshold stress intensity factor range ( ) equation is necessary. In this paper, a equation as a function of crack size was proposed using a nonlinear zone size criterion. By using the equation, the above peculiar fatigue fracture behaviours (1) and (2) and the stage II nonpropagating crack arrest condition could be evaluated quantitatively. Stage II nonpropagating crack initiation could be explained by considering the microdistribution of residual stress due to peening.

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“…In previous studies, the method of rendering a crack harmless by improving the fatigue limit using shot peening of high strength steel was proposed; the effectiveness of the method has been proven by the authors [1] [2]. Shot peening is a surface treatment process used to produce a beneficial compressive residual stress layer and modify the fatigue strength of metals by impacting a surface, using high-velocity spherical media.…”

Section: Introductionmentioning

confidence: 99%

Fatigue Limit Improvement by Needle-Peening for Stainless Steel Welded Joint Containing a Crack-Like Defect

Fueki

Takahashi

2016

Volume 5: High-Pressure Technology; Rudy Scavuzzo Student Paper Symposium and 24th Annual Student Paper Competition; ASME Nonde

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The effects of needle-peening on the bending fatigue limit of an austenitic stainless steel JIS-SUS316 welded joint containing an artificial semi-circular slit on the weld toe were investigated. Peening was applied to specimens with a semi-circular slit at depths of a = 1.0 mm and 1.5 mm. Then, plane bending fatigue tests were carried out at a stress ratio of R = 0. The fatigue limits of welded specimens containing a semi-circular slit were increased for the peened specimens. Peened specimens with slit sizes of a = 1.0 mm had high fatigue limits that were nearly equal to those of non-slit, peened specimens. We observed that a semicircular slit with a depth of less than a = 1.0 mm could be rendered harmless by peening. Additionally, the values of fatigue limit and the maximum depth of a semi-circular slit that can be rendered harmless by peening were predicted based on fracture mechanics, where we assume that a semi-circular slit is equivalent to a semi-circular crack. The prediction results were consistent with experimental results. NOMENCLATURE a: depth of crack alim: upper limit of depth of non-propagating crack amax: maximum depth of crack that does not decrease fatigue limit FEM: finite element method Kmax: maximum stress intensity factor Kmin: minimum stress intensity factor Kr: stress intensity factor due to residual stress ΔK: stress intensity factor range ΔKT: effective stress intensity factor range for fatigue crack growth ΔKT,A: stress intensity factor at the deepest point of the crack ΔKT,C: stress intensity factor at the surface of the crack ΔKth: threshold stress intensity factor range ΔK(L)th: threshold stress intensity factor range ΔKth for a large crack PPP: portable pneumatic needle-peening TIG: tungsten inert gas UNP: ultrasonic needle-peening x: longitudinal direction R: stress ratio α: shape parameter σnom: nominal stress σx: normal stress for longitudinal direction σr: residual stress σa: stress amplitude σmax: maximum stress Δσw0: stress range at the fatigue limit for non-slit, non-peened specimens

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Improvement of fatigue limit by shot peening for high‐tensile strength steel containing a crack in the stress concentration zone

Cited by 17 publications

References 8 publications

Fatigue Limit Prediction and Estimation for the Crack Size Rendered Harmless by Peening for Welded Joint Containing a Surface Crack

Fatigue Limit Prediction and Estimation for the Crack Size Rendered Harmless by Peening for Welded Joint Containing a Surface Crack

Analysis on peculiar fatigue fracture behaviour of shot peened metal using new threshold stress intensity factor range equation

Fatigue Limit Improvement by Needle-Peening for Stainless Steel Welded Joint Containing a Crack-Like Defect

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