A Development of AE Source Inversion System and an Application to the Monitoring of Hydrogen Assisted Cracking of Low Alloy Steel

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  • AE原波形解析システムの開発と低合金鋼の水素脆化割れモニタリングへの適用
  • AE ゲンハケイ カイセキ システム ノ カイハツ ト テイゴウキン コウ ノ

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Abstract

In order to elucidate the microkinetics of hydrogen assisted cracking of low alloy steel, a newly developed Acoustic Emission (AE) source inversion system was used. The paper discusses the feasibility and some problems in applying this system to monitor the kinetics of microcrack. The AE monitoring system is composed of displacement type transducer, preamplifier, high speed A/D converter and 32 bit personal computer. The transfer function of AE measuring system was carefully examined and found to measure the surface displacement without giving wave distorsion up to 1.5MHz. A computer software for AE source inversion procedure made it possible to calculate the second kind Green's function (transfer function of material) and also to simulate the surface displacement at sensor position and calculate the source waves from detected waves by convolution integral in time domain and deconvolution integral in frequency domain respectively. The energy released by step wise crack propagation was obtained by the deconvolution of detected waves with the overall transfer function of the system which was experimentally determined by pencil lead breaking at notch tip. The crack size was calculated from relieased energy with the assistance of fracture mechanics, and found to fairly well agree with the hydrogen induced intergranular fracture area at early time. Though the propriety and accuracy of the informations from source wave have to be carefully examined by more experiments of large specimens, it could be said that the AE source inversion procedure could give more direct informations on the microkinetics of environmental assisted cracking.

Journal

  • CORROSION ENGINEERING

    CORROSION ENGINEERING 39 (7), 347-354, 1990

    Japan Society of Corrosion Engineering

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