Fatigue strength of spring steel with small scratches

Nishimura, Yoshihiko; Yanase, K.; Ikeda, Yuichi; Tanaka, Yuzo; Miyamoto, Noboru; Miyakawa, Susumu; Endo, Mitsuru

doi:10.1111/ffe.12793

Cited by 30 publications

(21 citation statements)

References 37 publications

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“…It has been reported that for various metallic materials, the fatigue limit as a crack‐growth threshold can accurately be predicted by the

\sqrt{area}

parameter model . This model states that Δ Κ th at a stress ratio of −1 depends on the size of the initial crack or defect and the hardness of the material, expressed by the following equation:

normalΔ Κ_{th} = 3.3 \times 10^{- 3} ((), italicHV + 120) {(\sqrt{area})}^{1 / 3} .

The unit is MPa

\sqrt{m}

for Δ Κ th .…”

Section: Resultsmentioning

confidence: 99%

Effect of defects on the fatigue limit of Ni‐based superalloy 718 with different grain sizes

Kevinsanny

Okazaki

Takakuwa

et al. 2019

Fatigue Fract Eng Mat Struct

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Tension‐compression fatigue tests were performed on two types of Ni‐based superalloy 718 with different microstructures in which small artificial defects of various sizes and shapes were introduced. The susceptibility of the fatigue strength to the defects varied significantly with the microstructure morphology, ie, a smaller grain size made the alloy more susceptible to defects. The fatigue limit as a small‐crack threshold was successfully predicted using the area parameter model. The evaluation of the fatigue limit was classified into the following three stages depending on the defect size: (a) harmless defect regime, (b) small‐crack regime, and (c) large‐crack regime. Such a classification enabled comprehensive evaluation of the fatigue limit in a wide range of defect size, considering (a) defect size over a range of small crack to large crack and (b) characteristics of matrix represented by grain size and hardness.

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“…It has been reported that for various metallic materials, the fatigue limit as a crack‐growth threshold can accurately be predicted by the

\sqrt{area}

parameter model . This model states that Δ Κ th at a stress ratio of −1 depends on the size of the initial crack or defect and the hardness of the material, expressed by the following equation:

normalΔ Κ_{th} = 3.3 \times 10^{- 3} ((), italicHV + 120) {(\sqrt{area})}^{1 / 3} .

The unit is MPa

\sqrt{m}

for Δ Κ th .…”

Section: Resultsmentioning

confidence: 99%

Effect of defects on the fatigue limit of Ni‐based superalloy 718 with different grain sizes

Kevinsanny

Okazaki

Takakuwa

et al. 2019

Fatigue Fract Eng Mat Struct

View full text Add to dashboard Cite

show abstract

“…This equation is widely used for the prediction of the fatigue limit of numerous metallic materials with small defects and cracks. [30][31][32][33][34][35][36][37] It is worth noting that the model has been proven to give an accurate forecast of the fatigue limit of the Ti-6Al-4V alloy with small defects and cracks of diverse sizes and dimensions. [38,39] In the prior study by the author et al, the local R value was calculated according to the residual stress distribution in Equation 2, thereby enabling the successful prediction of the fatigue limit of an FOD specimen.…”

Section: Discussionmentioning

confidence: 99%

Effect of impact velocity and impact angle on residual stress fields caused by foreign object damage

Matsunaga

2020

Strain

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In order to study the residual stress induced by foreign object damage (FOD), the distribution of residual stress caused by the impact of a hard spherical body was measured via the sin2ψ technique, using synchrotron X‐ray. A steel sphere was impacted onto a flat surface of a Ti‐6Al‐4V alloy from an angle of either 90° or 45°, at a velocity of 180 m/s. The same sphere was also quasi‐statically pressed into the surface. In the cases of right‐angled impact and quasi‐static indentation, a compressive residual stress was extensively distributed inside the generated crater. No remarkable difference in residual stress distribution was noted between the dynamic case and the quasi‐static case. However, at an impact angle of 45°, a tensile residual stress that is more detrimental to fatigue strength was widely distributed inside the crater. Outside of the craters, tensile stress was generally observed in all cases.

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“…This observation can be attributed to the formation of the homogeneously distributed sub-micron size grains and ultra-fine nano carbides with high volume ratio after the deep cryogenic treatment as also discussed in the previous section. Fatigue tests were conducted under five different loads by using three samples for each load, Table 4. The high cycle (> 10 4 ) fatigue tests were selected to determine the fatigue strength of the specimens since the cryogenic treatment has no considerable contribution to the fatigue strength in low cycle (< 10 4 ) fatigue regime due to the possible failure in locking of the dislocations by fine martensite grains in this regime [33].…”

Section: Mechanical Properties Of Heat Treated Specimensmentioning

confidence: 99%

“…They are primarily utilized in the automotive industry as leaf springs and anti-roll bars, which are suspension elements used in various highway and railroad vehicles [2,3]. These suspension components generally have the tempered-martensitic microstructure to fulfill the necessary mechanical competence since they are constantly exposed to a dynamic mechanical stress [4].…”

Section: Introductionmentioning

confidence: 99%

Enhancement of the mechanical properties of EN52CrMoV4 spring steel by deep cryogenic treatment

Özden

Anık

2020

Materialwissenschaft Werkst

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The effect of the deep cryogenic treatment on the micro-structure and mechanical properties (tensile strength, toughness, residual stress and fatigue strength) of the medium carbon spring steel, which is subjected to different heat treatment steps, is investigated. Deep cryogenic treatment causes spring steel to keep compressive residual stress more efficiently due to an increase in the density of the crystalline defects, retardation in the stress relief after the phase transformations and nano-cluster carbide formations. If deep cryogenic treatment is applied before the tempering then the homogeneously distributed fine carbides form after the tempering and the grains remain relatively fine. The microstructure with homogeneously distributed fine carbides and fine grains cause spring steels to have simultaneously enhanced tensile strength, ductility and fatigue strength. If deep cryogenic treatment is applied after the conventional heat treatment (quenching + tempering), however, the coarse carbides form in the micro-structure and the improvement in the mechanical properties of the spring steel is limited.

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Fatigue strength of spring steel with small scratches

Cited by 30 publications

References 37 publications

Effect of defects on the fatigue limit of Ni‐based superalloy 718 with different grain sizes

Effect of defects on the fatigue limit of Ni‐based superalloy 718 with different grain sizes

Effect of impact velocity and impact angle on residual stress fields caused by foreign object damage

Enhancement of the mechanical properties of EN52CrMoV4 spring steel by deep cryogenic treatment

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