Research On Defect Identification With Ultrasonic Array Based On Vector Total Focusing Method

Throughout their life, industrial structures can be subject to a range of extremeoperating conditions for a long time such as high temperature, heavy load andcorrosion. These effects can lead to various defects, such as cracks and holes. Whilecracks are instability defects and can lead to serious harm for industrial structures.Even a small crack may rapidly expand under the action of alternating stress,temperature, etc when structures in motion, which eventually suddenly causesstructure fractured, leading to catastrophic accidents. These make crack become thebiggest security risk for the safe operation of industrial production. Meanwhile,different orientation of cracks can cause great different harmfulness to structures.Therefore, in view of crack defects detection and orientation identification problemsin structures, in this paper a vector total focusing technique with ultrasonic array isdeveloped to identify defects. The main research work includes:(1) Vector total focusing algorithmThe post-processing method for full matrix of ultrasonic phased array data isstudied and proposed the vector total focusing algorithm based on the correction totalfocus algorithm.Write program of vector total focusing algorithm and extract angle ofthe defect of interest from vector total focusing imaging, which used for identifyingthe orientation of crack.(2) The influencing factors of identifying the orientation of detects based onvector total focusing methodUsing the simulation and experimental full matrix data, the research oninfluences of identifying the orientation of detects based on vector total focusingmethod by three characteristic parameters, which include the number of element ineach sub-array, the incremental step between adjacent sub-arrays and syntheticweighted factor between sub-arrays, are conducted. At the same time, threecharacteristic parameters is optimized under the best result of identifying theorientation of detects. On this basis, the influence of the relative position between theprobe and the defect of interest for detecting defects and identifying the orientation ofdefects is studied to provide guidance for following experiment.(3) The test research and application of identifying the characterizations ofdetects based on vector total focusing method In this section, the defect identification technique based on vector total focusingmethod is applied to the detection of aluminum block with different orientation ofartificial cracks. The experimental result proves that using this technique not onlydetect the location of cracks, but also identify the orientation and length of cracks. Onthis basis, this technique is applied to the detection of forging with typical naturaldefects.