Mitsuharu Shiwa

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 Greens function of a medium and the transfer function of the measuring system. Then the size and mean nuclea...

ACOUSTIC EMISSION EVALUATION OF ARAMID REINFORCED ALUMINUM LAMINATE

ARALL shows a good fatigue crack resistance and a high tensile yield strength. Acoustic emission was monitored during tensile tests and loading-holding-unloading cycle tests for two types (notched and unnotched) of ARALL specimens. AE activities showed that the fiber breakage during the tensile tests depended upon the specimen geometry. Results of observations by a scanning electron microscope showed that the delamination also depended upon the specimen geometry. In loading-holding-unloading tests specimens were subjected to ASME standard (Section, V,11). AE activities showed different tendencies from that of the tensile tests. The ratio (Waveform Ratio = Rise time/Duration) of events during the tensile and loading-holding-unloading tests was shown to be a good indicator to distinguish the generated fracture mechanisms, such as delamination, fiber breakage and pull-out obtained from SEM observations.

ACOUSTIC EMISSION EVALUATION OF FIBER REINFORCED PLASTICS (FRP) COMPOSITE The In-plane Statistical Radiation Pattern Analysis

Abstract The in-plain statistical acoustic emission radiation pattern analysis on fiber reinfected composite material is successfully developed. The method is based on both the analysis of the displacement field of Lamb wave and evaluation for the sensitivity of piezo-electric device properties. The sample of the test used is angle ply CFRP. The acoustic emission signal detected using special six piezo-electric resonant sensors developed in our laboratory. Signals from the sensors are acquired using two different systems, PAC 3000/3104 AE analyzer and Dynamic Crack Microscope, which is a six channel acoustic emission source characterization system developed in our laboratory. The fracture mechanisms of this sample consists of Mode I, which corresponds to the delamination, Mode II which corresponds to debonding, and Mode I and Mode II combined mode which corresponds to a continuous delamination.