Feature Extraction Technology Of Ultrasonic Echo And Flaw Location Method In The Magnesium Alloy Castings

Magnesium alloy component is very widely used in aerospace, transportation, electronic information and other areas. But defects maybe appear near surface and internal the magnesium alloy castings while processing by some unknown reasons, such as flaw, impurity, bubble, that will affect the performance of magnesium alloy component and cause some serious safety accidents. This paper takes magnesium alloy billet warhead as the detection objects for the research of feature extraction technology of ultrasonic echo and defect location method in the magnesium alloy castings.Based on the analysis of ultrasonic testing principle about the magnesium alloy castings, this paper proposes a research plan of firstly extracting defect feature and then locating defect information.First of all, through analyzing the actual ultrasonic testing echo signal of magnesium alloy castings, several factors affectting accurately extracting the detection echo signal feature are obtained, and detection feature extraction technology is considered in this paper. When there is more than one flaw echo in ultrasonic echo signal, or the defects echo signal is overlapping the echo signal following the under surface echo, using spline interpolation method for signal envelope and taking envelope maximum point as defect feature, we can successfully extract the first detection echo signal feature, and also can effectively solve the problem of ultrasonic detection blind. When there is abnormal echo signal in ultrasonic echo signal, using the method of adaptive noise cancellation, we can effectively prevent the ultrasonic echo signal from the interference of abnormal echo signal.Secondly, according to the characteristics of magnesium alloy castings, the ultrasound propagation paths in the component are analyzed. And according to the arrival time of detection echo signal, this paper studies on defect location method of magnesium alloy castings, proposes determining the defects position in magnesium alloy castings in the mode of detect cross-sectional polar and displaying it in the form of image, in order to realize the purpose of defect location. Combining with the defects image of C scan and defects image of each detect cross-sectional, we can determine defects position, shape and size of the castings. The experiment result shows that, using feature extraction technology and defects locating method of this paper can determine effectively the defects near surface and internal magnesium alloy castings.The research result can provide important reference for the automatic ultrasonic testing of defects in the magnesium alloy castings.