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

对于声发射，发展了先进的导波(管状和杆状)声源定位和模拟方法。通过对SO和L(0，1)波的波形模拟和波形匹配，得到了氢泡、延迟断裂和空穴形成(Ti-Pd)的源动力学。这里的波形是由假设的裂纹张开与由压缩型PZT单元的展开确定的实验总传递函数的卷积计算的。发现高压钢延迟断裂的微裂纹接近瑞利波速度，在快速扩展过程中由于波能的泄漏而产生亚裂纹。首次利用声发射传感器对淬火高碳钢延迟性断裂的极快微裂纹进行了研究，该传感器监测到了频散的低频导波，但比机械断裂慢。这也是第一个强者…在Ti-Pd合金棒材吸氢过程中监测到了更多的快导波俄歇能谱，可能是由于氢气形成空洞。这种俄歇电子能谱是由于氢化钛释放出的氢气迅速形成空穴而产生的。作者首次提出了利用极少的声发射传感器进行声发射源定位的方法。导波在纵向和横截面上的声源位置仅由单个声发射传感器确定。这种信号分析所需的速度色散和模式分析的计算机软件是由国内开发的，目前已在互联网上开放。穿粒APC-SCC不发射AES，而粒间APC-SCC发射足够幅度的AES。利用PVD-TiN膜人工断裂所确定的综合传递函数，对APC-SCC过程中腐蚀电位的波动动力学进行了研究。然而，由于它的响应速度太慢，不能用电势波动的逆处理来研究它。小波分析(时频域分析)表明，在潜伏期内，高于0.2 Hz的波动频率占主导地位，而在鳞状细胞癌传播过程中，波动频率较低。较少

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