Simulation Of Ultrasonic Testing

Traditional ultrasonic flaw detection is based on defect assessments which mainlyrely on the analysis of defect echo signal by the inspection personnel’s experiences.However, for the test pieces with complex material and structure, even testers who haveprofessional inspection trainings and rich experiences will also meet difficulties inrecognition and quantitative. And the simulation of ultrasonic echo signal can assistinspection personnel to analyze the defect echo signals. In addition, simulation ofultrasonic testing can improve the understanding of ultrasonic propagating and imaging.Compared with the experimental study of ultrasonic flaw detection, simulation ofultrasonic testing is more economical and efficient. In designing testing schemes andprobes, effects of various parameters on acoustic field can be studied by changing theparameters of ultrasonic simulation mathematical model, so as to provide guidance fordesigning flaw detection schemes and probes. So it is of great significance to research onthe simulation of ultrasonic detection.The complete modeling process of multi Gaussian beam model is introduced in thispaper. And the acoustic emitting field of different interfaces, oblique incidence,multilayer and focusing transducer are calculated by using the multi Gaussian beammodel. In calculation of acoustic emitting field of focusing probe, a new approach whichbased on modeling the acoustic lens is introduced. While in previous literatures, acousticfield of focusing probe is calculated by modifying the Gaussian superposition coefficient.And the new approach can not only calculate acoustic field of spherical focusingtransducer, but can also calculate acoustic field of line focusing probe and other types offocusing probe.Process of simulation of echo signal of flat bottom hole that based onThompson-Gray ultrasonic measurement model is introduced in this paper. And testingexperiments of flat bottom hole are performed. System function in the formula of echosignal simulation can be obtained by either referent-experiment or simulation. Whetherthe system function is obtained by referent-experiment or simulation, the simulationresults and the experimental results would fit very well as long as simulation results andexperimental results are both normalized. This also verified the feasibility of calculating the defect echo signal using system function that based on simulation.Finally a method based on geometric acoustics for designing acoustic lens of probesof C scan ultrasonic testing of automobile gearbox gear girth weld is introduced in thispaper. Then the acoustic field of focusing ultrasonic probe which calculated by multiGaussian beam model is analyzed. Though distance between defects and probe andactual focal length are not exactly the same, the defects are still in the region ofrelatively high pressure. Furthermore, the method that based on geometric acoustics isvery simple and easy to use. So focusing probe design method based on geometricacoustics is very practical.