Microscopic Mechanism of Environmentally Assisted Cracking by the Inverse Analysis of Measured Data

针对声发射问题，提出了导波（管道波和杆波）的先进声源定位和仿真方法。通过对So（0,1）波和L（0,1）波的波形模拟，将计算得到的波形与实测值进行匹配，得到氢泡、延迟破裂和孔隙形成（Ti-Pd）的源动力学。这里的波形是由假设的裂纹张开与实验总体传递函数的卷积计算得到的，该传递函数是由压缩型PZT单元的扩展确定的。发现高温钢迟发断裂微裂纹接近瑞利波速，在快速传播过程中由于波能泄漏而产生亚裂纹。利用声发射传感器首次研究了延迟断裂的极快微裂纹，并在标记和棒样处监测了频散低频导波，但比淬火高碳钢的机械断裂要慢。在Ti-Pd合金棒的吸氢过程中，可能通过氢气形成空隙，首次监测到强而快速的导波Aes。这种Aes被认为是由氢化钛释放的氢气快速形成空洞而产生的。作者首次提出了利用少量声发射传感器定位声发射源的方法。仅用单个声发射传感器即可确定导波纵剖面和横剖面的震源位置。用于这种信号分析所需的速度色散和模态分析的计算机软件是在国内开发的，现在在互联网上开放。跨晶APC-SCC不发射Aes，而跨晶APC-SCC发射Aes，且有足够的振幅。利用PVD-TiN膜人工断裂确定的整体传递函数，尝试了APC-SCC过程中腐蚀电位的波动动力学。但由于其响应太慢，无法通过势波动逆处理进行研究。小波分析（时频域分析）表明，SCC在潜伏期以高于0.2Hz的波动频率为主，在传播过程中以较低的波动频率为主。少

For the Acoustic Emission (AE), advanced source location and simulation methods for guided waves (pipe and rod) are developed. Source dynamics of hydrogen blister, delayed fracture and void formation (Ti-Pd) were obtained by the wave form simulation of So and L (0,1) waves by the wave form matching of computed to the measured. Here the wave form was computed by the convolution of assumed crack opening with experimental over-all transfer function determined using the expansion of the compression type PZT element. Micro-cracks of delayed fracture of high tension steel was found to be close to the Rayleigh wave velocity and caused sub-cracks by leaking the wave-energy during fast propagation. Extremely fast micro-crack of delayed fracture was first studied by using the AE sensors at marker and the rod specimen where the dispersive low frequency guided waves were monitored, but was slower than those of mechanical fractures of quenched high carbon steel. It was also first that the strong an … More d fast guided wave Aes were monitored during hydrogen absorbing of Ti-Pd alloy rod, possibly by void formation by hydrogen gas. Such Aes are supposed to be produced by rapid void formation by hydrogen gas emitted from titanium hydride.The author first proposed the AE source location method using very few AE sensors. Source locations of guided wave, both in the longitudinal direction and transverse section, were determined only a single AE sensor. Computer soft ware for velocity dispersion and modal analysis, required for such signal analysis were developed at home and now opened on the internet.Trans-granular APC-SCC does not emit Aes while inter-granular one does emit Aes with sufficient amplitudes. Fluctuation dynamics of corrosion potential during APC-SCC were attempted using the over-all transfer function determined by artificial fracture of PVD-TiN film. However, it could not be studied by the inverse processing of potential fluctuation due to it's too slow response. Wavelet analysis (time-frequency domain analysis) revealed that fluctuation frequency higher than 0.2Hz was dominant during the incubation period, but lower frequency during SCC propagation. Less