Development Of Multi-channel Dynamic Photoelastic Imaging System

Ultrasonic wave is a kind of stress wave which can't be seen by people directly .The traditional method studying ultrasonic propagation is mainly to analyze ultrasonic signal which is received with transducers on the surface of solid, and conclude the propagation of ultrasonic wave in the material. With the rapid development of modern non-destructive testing technology and the continuous improvement of detecting accuracy, multi-channel ultrasonic testing, phased array and other new multi-elements ultrasonic testing technologies are applied to engineering practice, and the dissemination of ultrasonic wave in the material becomes more complex, which brings great difficulties to the research of sound field. In order to make ultrasonic wave become visible and make people understand the complex sound field intuitively, the author developed a multi-channel dynamic photoelastic imaging system.By using dynamic photoelastic technique, the system can observe the propagation regularity of multi-elements ultrasonic wave in transparent solids .This system can provide visual images that displays the propagation of ultrasonic wave in solids for non-destructive testing workers, particularly science and technology workers who use multi-element focused ultrasound to detect defects in materials, Which can provide experimental basis for the ultrasonic flaw detection and has important guiding significance in ultrasonic nondestructive testing. The development process of multi-channel dynamic photoelastic system is described in this paper in detail.Main tasks are as follows:Develop a Multi-channel delay controller which can control the phase delay of each element of the ultrasonic array transducer and control the acousto-optic delay. By using microcontroller as a controlling core and Cooperating with delay circuit and Multi-channel address decoding circuit, the system can excite each element of the ultrasonic array transducer with independent phase delay, produce flexible and controllable sound beam whose focus is controllable in solid and simulate sound beam scan of ultrasonic phased array technology.By using dynamic photoelastic technique, the system realizes the visualization of multi-elements focused ultrasonic sound field .we can observe the propagation of focused ultrasonic wave in transparent solids, and the focused ultrasonic wave theory of materials testing is verified by the visual experimental means.Develop a multi-channel ultrasonic transmitting system. A new circuit structure with 2-MOSFET was applied via optimizing the circuit in existence. With the new circuit, the width of the pulse can be adjusted, and the matching ability was improved.Develop multi-channel dynamic photoelastic imaging software which includes many functions such as phase control, dynamic preview,image acquisition, image post-processing and so on. Good human-machine interface make operators feel more convenient.When the system was completed, we carried out performance testing, and take many pictures which display the propagation of multi-elements focused ultrasonic wave in the glass.