Nondestructive evaluation of plastic damage in a RAFM steel considering the influence of loading history

Autor: Hiroyuki Miki, Manru He, Sho Takeda, Hong-En Chen, Toshiyuki Takagi, Takanori Matsumoto, Shejuan Xie, Zhenmao Chen, Tetsuya Uchimoto
Rok vydání: 2019
Předmět:
Zdroj: Journal of Nuclear Materials. 523:248-259
ISSN: 0022-3115
DOI: 10.1016/j.jnucmat.2019.05.048
Popis: Reduced Activation Ferritic/Martensite (RAFM) steel is a new material considered to be one of the important candidate structural materials for Tokamak fusion reactors. Plastic deformation inevitably occurs during the operation of fusion reactors due to giant unexpected loads. To ensure the structural integrity, reliable non-destructive evaluation (NDE) for RAFM steel is of great importance. Magnetic Barkhousen Noise (MBN), Magnetic Incremental Permeability (MIP) and Magnetic Flux Leakage (MFL) methods are found being effective especially for NDE of large plastic deformation in RAFM steel by authors. Its feasibility for small plastic deformation under 1%, however, is not clarified. At the same time, as mechanical damage may be caused by several times of large load, i.e., the current deformation state is possibly of complicated loading history. To clarify the influence of these factors is also very important for application of these magnetic NDE methods in practice. In view of this background, the influences of plastic deformation history on NDE signals and the feasibility of the magnetic NDE methods for relative small deformation are experimentally studied in this paper. From experimental results, it was found that the MIP and MFL signals decrease with an enlarged plastic deformation and are not significantly influenced by the plastic deformation history, while the MBN signals show significantly different tendency for specimen of different loading history. To understand the mechanism, micro-structure analyses and magnetic domain observations are conducted by using the EBSD and the magnetic powder-pattern method. Observation results reveal that the pinning effect of the micro defects prevents the movement of magnetic domain walls and perturbs the signals of magnetic NDE methods, especially on the MBN signals. These results show that the MIP and MFL method are more suitable for evaluation of plastic deformation in RAFM steel from practical application point of view.
Databáze: OpenAIRE
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