Research On Defect Detection Of Aluminum Alloy Die Casting Based On Ultrasonic Phased Array Technology

Pressure casting is a main method in metal processing technology,and the die casting produced by this method is widely used in various fields.Aluminum alloy die casting has become the second largest metal using material in the world due to its good corrosion resistance,light weight and other advantages.During the production or use of aluminum alloy die casting,defects such as holes,cracks and inclusions will occur,which will not only cause property loss but also cause serious personal safety hazards.Therefore,it is urgent to study the defect detection of aluminum alloy die casting.First of all,this article introduces the types and characteristics of die casting defects in detail.Several detection methods for these defects are proposed,and the ultrasonic phased array technology is selected to detect the die casting defects.The ultrasonic phased array probe has a significant advantage that it can realize the deflection and focus of the sound beam without moving the probe,so as to detect defects at different angles and depths of workpiece.Therefore,the ultrasonic phased array probe is used to detect the defects of aluminum alloy die castings.The principles of phased array transmitting and receiving are introduced,and the deflection delay law and focus delay law in aluminum alloy die casting are designed and calculated.The arrangement and basic structure of the transducer probes are studied in order to improve the detection effect,and a one-dimensional linear phased array probe is selected as the detection probe of this project.The directivity of linear phased array probe is studied,and three standards of linear phased array probe design are obtained.The width of the main lobe of the sound beam should be minimized as much as possible,the existence of the grating lobe should be eliminated,and the amplitude of the side lobe should be minimized.The transducer probe with different parameters is simulated by MATLAB software,and the parameters of the transducer probes are determined on the premise that the probe design standards are met.The sinusoidal excitation signal modulated by different window functions and the negative square wave excitation signal for ultrasonic detection are studied.By simulating the propagation of different waveforms and wave numbers in aluminum alloy die castings,the ultrasonic echo signals are analyzed from the energy value and the quality factor,and the negative square wave excitation signal is determined as the detection excitation signal.According to the characteristics of focused acoustic beam and the theoretical near-field length of ultrasonic wave propagating in water and aluminum alloy die casting,the aperture of transducer is determined.By simulating the propagation path of the phased array probe in the water and aluminum alloy die casting,the delay law of the liquid-solid interface is determined.An experiment platform for defect detection of aluminum alloy die casting was built to detect the die casting with different sizes and types of defects.The structural dimensions of aluminum alloy die castings with different kinds of defects are introduced.According to different structural dimensions,the detection parameters such as scanning step distance,water distance and focusing depth are determined.Wavelet analysis is used to analyze the experimental data,and the energy eigenvector values of different kinds of defects are obtained,which laid a foundation for the identification of defect types in the actual ultrasonic testing process of aluminum alloy die castings.