Measurement of Stress Distribution Near Fatigue Crack in Ultra-Fine Grained Steel by Synchrotron Radiation

Akiniwa, Yoshiaki; Tanaka, Keisuke; Kimura, Hidehiko

doi:10.4028/www.scientific.net/msf.490-491.118

Cited by 2 publications

(2 citation statements)

References 5 publications

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“…With the help of a compact loading frame mounted on a diffractometer, diffraction measurements can be performed to analyse stress distributions in the cross section under in-situ mechanical loading. Such setups were successfully applied to study microscopic loading sharing in composites and polycrystalline materials [4,5] and stress distributions around crack tips [6]. In the current work, we have used in-situ synchrotron diffraction to study load partitioning between the surface and bulk for a duplex steel of type SAF 2507 having a strengthened surface with compressive residual stresses and the influence of low cycle fatigue loading.…”

Section: Introductionmentioning

confidence: 99%

S164 Load Partitioning in a Duplex Stainless Steel with Surface Strength Gradient and Residual Stresses

et al. 2008

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The load partitioning between surface and bulk was studied by means of in-situ synchrotron energy dispersive diffraction in an SAF 2507 superduplex stainless steel having a strain hardened surface layer with compressive residual stresses. Two loading cycles with a peak tensile strain of 0.5% and 0.87%, respectively, were successively applied and the evolution of stresses in the respective constituent phases (austenite and ferrite) were measured in a 0.026 mm thick surface layer and at 0.75 mm depth, from which the macrostress development was derived, respectively, for the two locations. It was found that the surface and the bulk followed different loading paths and that such inhomogeneous load sharing was related to variation in strength and residual stresses over the load-carrying cross-section. During macroscopic elastic loading, the load partitioning, characterized by increasing tensile stress in the bulk and decreasing compressive stress in the surface, depended mainly on the initial residual stress distribution. Upon yielding of the bulk, a rapid load transfer from the bulk to the hard surface layer started and continued until the surface also reached its elastic limit. At the 0.87% peak strain, the plastic incompatibility over the cross-section resulted in a much higher stress in the surface (1070 MPa) than in the bulk (680 MPa), which also led to a large tensile residual stress in the surface after unloading. In the paper, the observed inhomogeneous microscopic load partitioning was also presented.

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Section: Introductionmentioning

confidence: 99%

S164 Load Partitioning in a Duplex Stainless Steel with Surface Strength Gradient and Residual Stresses

et al. 2008

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“…Synchrotron radiation sources provide the X‐rays with extremely high intensity as well as narrow divergence. The stress distribution around a fatigue crack and a crack closure can be evaluated using this method to a sufficient accuracy 16 . The synchrotron method has previously been applied to a fibre reinforced composite using tomographic imaging and strain mapping 17–20 .…”

Section: Introductionmentioning

confidence: 99%

Evaluation of fibre bridging stress of short fatigue cracks in SCS‐6/Ti‐15‐3 composite

Akiniwa

Fujii

Kimura

et al. 2006

Fatigue Fract Eng Mat Struct

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A B S T R A C T Single-edge notched specimens of a unidirectional SiC long fibre reinforced titanium alloy, were fatigued under four point bending. The propagation behaviour of short fatigue cracks from a notch was observed on the basis of the effects of fibre bridging. The branched fatigue cracks were initiated from the notch root. The fatigue cracks propagated only in the matrix and without fibre breakage. The crack propagation rate decreased with crack extension due to the crack bridging by reinforced fibres. After fatigue testing the loading and residual stresses in the reinforced fibres were measured for the arrested cracks by the X-ray diffraction method. The longitudinal stresses in the reinforced fibres were measured using high spatial resolution synchrotron radiation. A stress map around the fatigue cracks was then successfully constructed. The longitudinal stress decreased linearly with increasing distance from a location adjacent to the wake of the matrix crack. This region of decreasing stress corresponded to the debonding area between the fibre and the matrix. The interfacial frictional stress between the matrix and the fibre could be determined from the fibre stresses. The bridging stress on the crack wake was also measured as a function of a distance from a notch root. The threshold stress intensity factor range, corrected on the basis of the shielding stress, was similar to the propagation behaviour of the monolithic matrix. Hence the main factor influencing the shielding effect in composites is fibre bridging.

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Measurement of Stress Distribution Near Fatigue Crack in Ultra-Fine Grained Steel by Synchrotron Radiation

Cited by 2 publications

References 5 publications

S164 Load Partitioning in a Duplex Stainless Steel with Surface Strength Gradient and Residual Stresses

S164 Load Partitioning in a Duplex Stainless Steel with Surface Strength Gradient and Residual Stresses

Evaluation of fibre bridging stress of short fatigue cracks in SCS‐6/Ti‐15‐3 composite

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