Research On Voiceprint Feature Of Metal Micro Crack Detected By Nonlinear Ultrasonic

In today's manufacturing industry,steel plates are widely used in a variety of manufacturing equipment.Because the steel plate in the production and use process,bear the more complex load condition,the steel plate is easy to produce micro-crack,and the micro-crack of the steel plate will increase,and eventually lead to fracture,causing great harm and loss to life and property.According to the latest research,the traditional linear acoustic detection is insensitive to microcracks,it is difficult to detect microcracks,and the nonlinear effect is strongly related to the microcracks inside the material.In this paper,the nondestructive testing method of micro-crack steel plate based on the nonlinear generation of medium and differential frequency wave is studied by means of theory and numerical simulation.This paper studies the nonlinear Ultrasonic theory,introduces the application of nonlinear ultrasonic detection in cracked steel plate,and the classical nonlinear acoustic theory of nonlinear ultrasonic detection materials,and deduces the nonlinear acoustic effect of high order harmonic and the corresponding nonlinear acoustic parameters,and puts forward the concept of contact nonlinear acoustic theory and contact nonlinear parameters,It is also analyzed and explained that contact nonlinearity is an important mechanism of nonlinear acoustic effect.The characteristics of microcracks polarity(two tip)inside the material are analyzed and described,and the finite element simulation of the micro-crack of steel plate is simplified by using the Bipolar Arc transition scheme.The finite element simulation was used to verify that the ultrasonic wave produced high harmonics after the micro-crack through the steel plate,and compared with the results of steel plate analysis without microcracks.The influence of mesh density and unit type execution mode on the finite element analysis results of steel plate microcracks is discussed.In this paper,the frequency composition of the mixed-frequency ultrasonic wave after the micro-crack of the steel plate is analyzed theoretically,and a positive correlation trend between the microcracks length and the nonlinear characteristic coefficient of the frequency is deduced,and the finite element analysis is used to verify it.