Composite Defect Detection Research Based On The Ultrasonic Testing

Ultrasonic nondestructive testing technology is a simple and effective method for composite material in the detection of inner defects,it is mainly used for detection of compact structure,porous materials,the structure of the layer board and honeycomb sandwich structure,etc.This article selects the typical compact artifacts and porous materials for ultrasonic measurement.Firstly,according to traditional(contact)ultrasonic nondestructive testing technology confrontation dense concrete member in the process of uniaxial compression consolidation stage,elastic stage,plastic stage and adjacent destruction,during ultrasonic detection test,analysis of similarities and differences of different phase inside the concrete damage ultrasonic testing signals.Based on the sound,sound velocity,frequency and amplitude of acoustic parameters to analyze and get some concrete specimen,the change trend of each development stage in damage,internal defects of concrete for qualitative analysis.Using fast Fourier series transform the waveform graph to spectrum,interpret each phase of the frequency spectrum characteristic curve,identify signal characteristics of each stage.By analyzing ultrasonic detection test results of acoustic parameters and spectrum characteristic curve we can real-time tracking of actual concrete structure of the development of internal damage,reinforce the remedial measures in a timely manner.Traditional ultrasonic testing methods confront a dense structure itself exists damage detection results are ideal.But for porous material acquisition signal disturbance,unable to carry on the qualitative and quantitative analysis,and the traditional ultrasonic testing method(contact)can make the coupling agent to immerse in the material internal and make the specimen to be affected with damp,dirty and the mechanical properties of stability.In this paper,on the basis of the traditional ultrasonic testing for porous ceramic fiber insulation material,air coupling ultrasonic testing experiment is carried out.Mainly discusses the basic idea and characteristics of air coupling ultrasonic testing,use the air coupling ultrasonic automated testing instruments and transmission method to detect the bonding defects between the porous ceramic fiber material and substrate.Combining with the median filtering,use Otsu best global threshold method for image segmentation,get the binary image containing target defect information,calculate the number of pixels to get defect area.According to the defects in the images of the experiment,we get the deboning detection precision of the structure of the adhesive for Φ4mm.By pixel value to calculate the defect area we know the error between the known defect area of the specimen and the bonding defect area of calculating is less than ±9%.Results show that the air coupling ultrasonic testing is a very effective measure for sample defect and has a good imaging precision.Otsu can detect and analyze defects quantitatively and the quantitative accuracy is very high.