Design Of Ultrasonic Sound Field Distribution Measurement System

Ultrasonic nondestructive testing is one of the important methods in the field of non-destructive testing.In order to ensure high reliability,high sensitivity and high quality of inspection results,it is necessary to quickly and accurately obtain the location,shape and size of defects.The key element in ultrasonic NDT is the ultrasonic transducer,whose sound pressure distribution characteristics greatly affect the localization of defects in ultrasonic inspection and determine the size and measurement of the ultrasonic transducer.Therefore,in order to avoid the hidden danger of missed detection due to weakened or failed ultrasound probe performance,the sound field parameters of the transducer need to be measured for the purpose of judging and calibrating its performance.Common sound field measurement methods include hydrophone method,radiation force balance method,ball target method,etc.Each of these measurement methods requires a system that consists of a three-axis system that can accurately reach the test position and a high-speed data acquisition system.For example,the hydrophone method uses a three-axis movement system that allows the hydrophone to move relative to the transducer in the water tank.At the same time,the hydrophone can collect the sound pressure signal from each measurement point and send it to the computer through the acquisition system.The acquisition system processes the sound pressure information and the measurement point information to display the distribution of the measured transducer’s sound field.This paper designs a measurement system for measuring ultrasonic sound field distribution,which consists of two parts: software and hardware.The software part is written on a PC by QT Creator.The software has a simple interface and is easy to use by the operator.It can also perform data processing,image display and report output on the collected sound field data,which meets the work requirements of ultrasonic probe calibration.In order to facilitate cross-platform development,the software uses visualization to enable users to observe the measured sound field data more intuitively.The hardware part consists of a motion control card,a data acquisition card,a stepper motor driver,and a Cartesian Coordinate Robotic Arm.The Cartesian Coordinate Robotic Arm is based on linear motion units to build a spatial three-degree-of-freedom motion mechanism so that it can reach any point in three-dimensional space.Each linear motion unit adopts precision grinding screw with low friction loss,high transmission efficiency,no crawling at low speed and high accuracy.The trajectory planning algorithm used in the motion part achieves a repeatable positioning accuracy of ±0.04 mm,which meets the requirements of the motion control system in the sound field measurement work.And the system uses a high-speed acquisition card with sampling frequency up to 250 Mhz,sampling accuracy of 16 bit,and onboard memory of 2GB for data acquisition.It can accurately and completely collect the transducer sound field distribution data,visualize the collected data in the software,and completely display the performance index of ultrasonic sound field distribution.And in this paper,the system design is completed after the water immersion flat probe for the sound field distribution measurement experiments.The test results show that this system can achieve the ability to measure the transducer sound field characteristics parameters,visualize the data and output reports.