2020 Fiscal Year Research-status Report
Development of two-dimensional strain mapping technique around a fatigue crack using the pulsed neutron Bragg-edge transmission imaging and neutron diffraction
| Project/Area Number |
20K20106
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| Research Institution | Japan Atomic Energy Agency |
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Principal Investigator |
蘇 玉華 国立研究開発法人日本原子力研究開発機構, 原子力科学研究部門 J－PARCセンター, 主査 (20644264)
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| Project Period (FY) |
2020-04-01 – 2022-03-31
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| Keywords | fatigue damage / Bragg-edge imaging / neutron diffraction |
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| Outline of Annual Research Achievements |
This research is devoted to develop the fatigue evaluation technique by a combination of two neutron methods: Bragg-edge transmission imaging and diffraction. Here, we prepared the compact-tension (CT) specimens under different fatigue conditions. Two kinds of steels: an austenitic stainless steel (SUS304) and a duplex stainless steel (SUS329J4L; Japanese Industrial Standards) consisting of austenite and ferrite, were used in the present investigation. The two-dimensional (2D) maps of the residual strain/stress and microstructure around a fatigue crack can be non-destructively obtained by Bragg-edge spectral analysis and diffraction pattern analysis.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
The fatigue crack growth tests were conducted using constant-amplitude cyclic loading model at room temperature until the crack length reached 10 mm or 25 mm. In addition, the digital image correlation (DIC) was also applied for crack tip strain field characterisation at the surface of the samples during the fatigue testing. We have performed the time-of-flight (TOF) neutron Bragg-edge transmission imaging experiment at the energy-resolved neutron imaging system, RADEN, BL22 and the neutron diffraction experiment at the engineering diffractometer, TAKUMI, BL19 at MLF/J-PARC, respectively.
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| Strategy for Future Research Activity |
The RITS code will be used for Bragg-edge spectral analysis. 2D maps of the strain, texture variations and phase volume fraction can be obtained. The diffraction data will be analysed by the Z-Rietveld software, to obtain residual lattice strain, texture and phase volume fractions. The obtained original information of the strain and crystalline structure state inside the bulk could give a greater understanding on crack tip elastic and plastic strain evolution mechanisms in engineering materials. The 2D mapping technique will be further applied to investigate the effect of temperature on the fatigue-crack growth behaviours, to evaluate how the martensite distribution due to phase transformation under cryogenic conditions of very low temperature to affect the fatigue-crack growth.
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| Causes of Carryover |
The incurring amount will be used for sample and jig preparations, academic conference participations and paper publications in the next fiscal year.
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