Experiment Research on an Optical Fiber F-p Ultrasound Sensor for Detecting Internal Defects of Metal Materials

Metal materials have been used in aero industry widely because of its excellent characteristics. So its internal defects are very important. Ultrasound detection technology for detecting metal materials internal defects is related to piezoelectric ultrasonic sensor. This has a few of disadvantages. So the double wavelength optical fiber F-P ultrasound sensing system is designed in this paper. The ultrasound detecting experiment devices for internal defects of metal materials is established based on the optical fiber F-P sensing system. Experimental research of detecting the internal defects is developed. The experimental results show this sensor can detect the ultrasound signals effectively. And it’s proved that this method can be effective used in the internal defect of metal materials.

Design and Experiment of PVDF Transducer for Laser Ultrasound Detecting

The design of PVDF transducer is finished and its designing idea and structure frame are presented. The laser ultrasound in nano A1P/SiO2 is detected by the PVDF transducer and the acoustic signal curve is obtained. The ultrasound waveform thermal elastically generated by a rectangular laser pulse is theoretically presented. The ultrasound pulse waveform obtained in the experiment is in accordance with the one in theory. It is shown that this design method is simple, practical and easy to implement.

Bat attacks and moth defensive behaviour around street lights

The defensive behaviour of moths around street lights was examined at a site where bats feed heavily on moths. The lights had a negative effect on moth defensive behaviour, but a combination of observational techniques (recording the outcome of naturally occurring bat-moth interactions) and experimental techniques (deafening moths by puncturing the tympanal organs) indicated that ultrasound-detecting ears still afforded the moths some protection from bat predation. On average, bats captured 69% of the moths they attacked. Moths that exhibited evasive behaviour were caught significantly less often than those that did not (52 vs. 2%). Moths whose tympanic organs had been punctured were significantly easier to catch (requiring fewer attempts) than moths with intact ears, reflecting the fact that significantly more of the eared than the deafened moths showed evasive behaviour (48 vs. 0%). Overall, the number of captures of deafened moths was higher, though not significantly, than the number of captures of eared moths.