The Research Of Weld Axis Defect Of Ultrasonic TOFD Based On Transformed Wave

The time-of-flight diffraction measurement technology is a new type of non-destructive testing technology.It adopts a transmitting probe and a receiving probe symmetrically arranged on both sides of weld.The detection method to get size and location of defect by measuring the diffraction time lag defect edge.TOFD technique has advantages as follows: high detection precision and speed,low error rate at location and identification of defect size.In recent years,the TOFD detection technology is widely used in the detection of weld.The conventional TOFD detection gets the length of the defect and the depth information based on the defects in the weld center line.But the calculated depth of defect is not accurate when the defect is not in the middle of two probes,which due to the existence of the error of axis deviation in the process of TOFD inspection.In order to reduce the measurement error,improve the accuracy of the defect location quantitative,the defect is not in the weld center line are studied in this paper base on transformed wave.The main contents are as follows:(1)Introduce the mathematical model,establish the TOFD detection system and analyze the transformed wave,calculate deviating from the weld defects in weld center distance using the deformation wave transmission time and the defects of endpoint diffraction wave transmission time.Solve the length of the defect by established the mathematical model,transformed wave was made use of,then the time difference among the diffracted longitudinal wave signals of cracks and transformed waves signals was surveyed,and the calculated depth was modified by iterative procedure.Then the distance of the defect deviating from the middle of two probes was drawn out.(2)Artificial block is designed and manufactured to simulate artificial based on the TOFD principles,perform on the artificial block and the actual work piece,The TOFD detection maps offline analysis software are used to get the software defects analysis information,and to extract the defect in the map of the direct wave,defect and deformation of endpoint diffraction wave transmission time and probe delay time by means of a computer program calculate the eccentric distance and the defect depth value optimization.The optimized analysis of defect information and software defect information get defects associated with the measured values.(3)measure the actual information contained in the defects of work piece by the destructive experiment,compare the defects of software analysis values with the optimized measurement values,and found that the optimize defect that base on transformed wave is closer to the actual information and the measuring error is lower than before.In this paper,we can found that taking the advantage of the transformed wave to measure the weld defects and optimize the value of the depth of the defect further.The measurement values conform to the requirements of the TOFD testing standards.And the optimized values are more closer to the actual values than the software analysis values.It improves the sizing accuracy by using the transformed waves of TOFD.