Dynamic Crack Microscope and Its Application

A new generation acoustic emission (AE) source characterization system combined with detected wave analyzing system was developed for materials evaluation. The system consists of six AE transducers. parallel processing units. a host CPU and a desk-top computer subsystem. AE signals from each transducer are digitized by a high-speed ND converter in each processing unit. From digitized waveform data, AE parameters such as arrival time, peak amplitude, rise time and phase of the first motion of longitudinal wave are extracted by a Digitial Signal Processor (DSP) installed in each processing unit. The data of arrival time in each channel is fed into the host CPU to determine AE source location. The location result together with both AE parameters and waveform data are transferred to the desk-top computer, on which AE source functions are calculated by single deconvolution method using both the dynamic Green's function of a medium and the transfer function of the measuring system. Then the size and mean nucleation velocity of microcracks are automatically calculated. This advanced system was applied to the fracture toughness testing in Ti-8AI-1Mo-IV alloy and the microfracture process of the material was quantitatively evaluated.