Development Of High Precision Multi-channel Dynamic Photoelastic Imaging System

Ultrasonic waves as a kind of stress wave can not be observed with the naked eye.People's initial understanding of acoustic detection is through ultrasound electronics.Recognizing ultrasonic waves from the electrical signals received by the ultrasonic transducer and then derive the propagation characteristics of the ultrasonic waves in the object.However,with the continuous development of modern industrial technology,industrial production departments have put forward new and higher requirements for ultrasonic testing technology.At this point,ultrasound multi-channel detection technology came into being.Compared with single-channel ultrasonic detection,the detection efficiency and accuracy can be greatly improved.But with the introduction of multiple elements,the sound field it inspires will also become extremely complex.This has brought great difficulties to the research of multi-element sound field.In order to make people more intuitive to observe and study the multi-element phased phase sound field,the author developed a set of high-precision multi-channel dynamic photoelastic imaging system by introducing FPGA technology..This system is based on dynamic photoelastic technology.Through embedding soft core technology,phase-locked loop technology,differential counting technology,serial communication technology,and adjustable pulse width technology,the entire phase-controlled emission acousto-optic synchronization delay control system is implemented in a single FPGA.Compared with the existing multi-channel dynamic photoelastic observer device,the phase-delay precision is improved by 10 times,from the original 25 ns to 2.5 ns.This has positive significance for improving the practicability,stability and portability of multi-channel dynamic photoelastic imaging systems.In this dissertation,the implementation scheme of high-precision multi-channel dynamic photoelastic imaging system is described in detail.The main tasks are:A high-accuracy multi-channel phased emission acousto-optic synchronization delay control system was developed.It is mainly used to control the sound field excited by the multi-element transducer.With the method of the system to collect sound field images,complete the sound field acquisition of different time images.Developed a set of high voltage narrow pulse signal generation circuit for transducer excitation.The pulse width of the excitation signal can be adjusted within 100ns-2us.The effective operating range of the excitation voltage is 0V-400 V.The voltage and pulse width of the excitation signal can be adjusted independently of each other.Within a certain range,the best matching with the transducer used can be achieved.Developed a LED light source high-power instantaneous lighting circuit.The nanosecond high-voltage,high-current,narrow-pulse electrical signals generated by the avalanche effect of the tertiary tube are used to light up the LEDs to realize the high-brightness,narrow-light pulsed-strobe light source required to observe the sound field.A 2Mhz,8-chip system-specific transducer was fabricated using a high-performance piezoelectric wafer.Through the Visual Basic programming language,a set of system-specific computer software was developed.Finally through the joint debugging of hardware and software,a good sound field observation effect has been achieved.