Nonlinear Behavior of the Ultrasonic Signal and Its Application

Ultrasonic testing technology has been extensively used in non-destructive testing of materials and equipments.The ultrasonic echoes, which indicate the performances of the materials and the information of the flaws,are greatly complicated,because of their noises and the interaction between the ultrasonic wave and the transmitted medium,the flaw among them.To understand the nonlinearity possessed in the ultrasonic echo is greatly important and significant for the testing and evaluation of materials and flaws.This paper,with the background of offshore pipeline ultrasonic inspection,investigates the nonlinear behavior of the ultrasonic signal from the angle of time domain using the methods of surrogate data test and statistical vectors.The results show that there exist distinct nonlinearity in the ultrasonic signals,and also indicate that the nonlinearity is generated not by the testing function,but by the dynamic system,that is to say,the nonlinearity is generated by the interaction between the ultrasonic wave and the reflector.The paper also analyzes the applications and prospects of the nonlinear features.