Interior-Induced Fracture Mechanism of High Cleanliness Spring Steel (JIS SWOSC-V) in Very High Cycle Regime

Miura, Taku; Sakakibara, Takayuki; Kuno, Takanori; Ueno, Akira; Kikuchi, Shoichi; Sakai, Tatsuo

doi:10.4028/www.scientific.net/kem.664.209

Cited by 5 publications

(3 citation statements)

References 16 publications

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“…In Step B in the crack initiation model, local micro‐debondings take place along the boundaries between fine granular layer and the martensitic matrix. Those micro‐debondings in high‐strength steels tend to occur isolatedly as sometimes confirmed by several researchers by means of the fracture surface topography analysis technology.…”

Section: Resultssupporting

confidence: 55%

Microscopic and nanoscopic observations of metallurgical structures around inclusions at interior crack initiation site for a bearing steel in very high‐cycle fatigue

Sakai

Oguma

Morikawa

2015

Fatigue Fract Eng Mat Struct

106

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A B S T R A C T In some high-strength steels, a fatigue crack tends to occur at the interior inclusion after a long-term sequence of the cyclic loadings at low stress levels, although the crack takes place at the surface in the usual life region at high stress levels. Thus, we have the duplex S-N curves consisting of the respective S-N curves for usual life region and very highcycle regime. It is well known that a significant fracture surface having the fine granular morphology is formed around the interior inclusion at the crack initiation site. This surface area is sometimes called as 'fine granular area'. In this work, metallurgical structures around the interior inclusion at the fatigue crack initiation site were carefully observed by combining several special techniques such as focused ion beam technique and highresolution scanning electronic microscopes. Based on the current observation results, it was found that the microstructure around the interior inclusion was changed into the penny-shape fine granular layer from the usual martensitic structure during long-term cyclic loadings. Then, debondings along with the boundaries of the matrix and the fine granular layer have produced the small cracks inside the metallic material, and these interior cracks caused the final fatigue fracture after definite loading cycles of the crack propagation.Keywords bearing steel; fine acicular area (FAA); fine granular area (FGA); interior crack initiation; rotating bending; very high-cycle fatigue. N O M E N C L A T U R Eα = stress concentration factor D = distance from definite section ΔK th = threshold value of stress intensity factor range in crack propagation N = number of cycles N f = number of cycles to failure R = stress ratio (minimum stress/maximum stress) σ = stress σ a = stress amplitude σ B = tensile strength σ w = fatigue limit I N T R O D U C T I O NAs a common understanding in the Metal Fatigue, it is well known that ferrous metals such as structural steels reveal the clear fatigue limit at the number of stress cycles less than 10 7 cycles. 1 However, non-ferrous metals such as aluminium alloys have no fatigue limit such that the S-N curve tends to decrease continuously in the very long life region, longer than 10 7 cycles. Usually, the fatigue limit for the structural steels is proportional to the tensile strength, and we have σ w = σ B /2, approximately, in the wide variety of the strength levels. 2,3 In recent years, practical structures such as railway wheels and axles, offshore structures, energy conversion and transportation systems have been used in a long term, sometimes, beyond their original design life

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Section: Resultssupporting

confidence: 55%

Microscopic and nanoscopic observations of metallurgical structures around inclusions at interior crack initiation site for a bearing steel in very high‐cycle fatigue

Sakai

Oguma

Morikawa

2015

Fatigue Fract Eng Mat Struct

106

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“…The results of these fatigue experiments disprove the assumption of a pronounced fatigue strength around 10

or 10

cycles for compression springs. This finding has been repeated in a multitude of tests on material specimens [ 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 ] and compression springs [ 3 , 15 , 16 ].…”

Section: Utilized Statistical Model For Fatigue Eventsmentioning

confidence: 82%

On the Influence of Ultimate Number of Cycles on Lifetime Prediction for Compression Springs Manufactured from VDSiCr Class Spring Wire

2020

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For the generation of fatigue curves by means of fatigue tests, an ultimate number of cycles must be chosen. This ultimate number of cycles also limits the permissible range of the fatigue curve for the design of components. This introduces extremely high costs for testing components that are to be used in the Very High Cycle Fatigue regime. In this paper, we examine the influence of the ultimate number of cycles of fatigue tests on lifetime prediction for compression springs manufactured from VDSiCr class spring wire. For this purpose, we propose a new kind of experiment, the Artificial Censoring Experiment (ACE). We show that ACEs may be used to permissibly extrapolate the results of fatigue tests on compression springs by ensuring that a batch-specific minimum ultimate number of cycles has been exceeded in testing. If the minimum ultimate number of cycles has not been exceeded, extrapolation is inadmissible. Extrapolated results may be highly non-conservative, especially for models assuming a pronounced fatigue limit.

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“…n order to assess the performances of this system, fatigue tests were carried out on valve spring Si-Cr oil tempered wire SWOSC-V [2]. Configuration of the fatigue specimen is presented in Fig.…”

Section: Evaluation Of the Performance Of The Introduced Systemmentioning

confidence: 99%

Development of in-situ fatigue crack observing system for rotating bending fatigue testing machine

Lian¹,

Ueno

Iwashita³

2015

Frattura Ed Integrità Strutturale

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Interior-Induced Fracture Mechanism of High Cleanliness Spring Steel (JIS SWOSC-V) in Very High Cycle Regime

Cited by 5 publications

References 16 publications

Microscopic and nanoscopic observations of metallurgical structures around inclusions at interior crack initiation site for a bearing steel in very high‐cycle fatigue

Microscopic and nanoscopic observations of metallurgical structures around inclusions at interior crack initiation site for a bearing steel in very high‐cycle fatigue

On the Influence of Ultimate Number of Cycles on Lifetime Prediction for Compression Springs Manufactured from VDSiCr Class Spring Wire

Development of in-situ fatigue crack observing system for rotating bending fatigue testing machine

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