Research On Acoustic Field Simulation And Control Method Of Ultrasonic Phased Array

Ultrasonic phased array detection technology controls the excitation delay of the probe array wafers by electronic method.The focused sound field at the set depth was formed with the each element's sound beam by constructive interference.Phased array detection technology which has the advantages of high detection efficiency,high resolution and sensitivity,high defect detection rate and good flexibility is suitable for the detection of complex shaped workpieces.In addition,the phased array detection technology is provided with depth focused and angular deflection.Misdetection and false detection due to fixed focus and limited angle by conventional single-crystal focusing probes can be effectively avoided.Moreover,the inspection efficiency and defect detection rate are also improved.However,the sound field distribution of ultrasonic phased array detection in practical applications is affected by the arrangement of array elements and the focusing algorithm which make superposed sound field formed more complex and diverse than the conventional single crystal focusing probe.The experiment cost and time required can be reduced by establishing a finite element model of sound field which can be used to observe the focusing sound field intuitively.It has important application value for the prediction of detect-ability,optimization of detection parameters and analysis of test results during actual detection.In this study,high-temperature alloy castings for aeroengine turbine disks are used as testing objects.The finite element model of ultrasound phased array detection sound field was established and optimized.Base on this,the distribution characteristics and influencing factors of the ultrasonic phased arrays focused sound field were analyzed.And the design and optimization methods of detection parameters are proposed.Based on the sound field simulation result,ultrasonic phased array focused sound field control method is implemented,and the ability of the phased array to detect high-temperature alloy components is improved.The main research contents includes: Firstly,the finite element method was used to simulate the sound field in ultrasonic phased array detection of GH901 superalloy specimens.Combined with the material properties and transducer parameter of the finite element model,the finite element simulation models for direct contact method and wedge coupling method was established.By measuring the focus error and focus sound pressure amplitude changes,the influence of mesh size,load sub-step time,and simulated sampling rate of load on the precision and accuracy of finite element calculation were analyzed.And the finite element models were optimized.Secondly,based on the optimized finite element model,the focused sound field characteristics of ultrasonic phased array were studied.Using finite element simulation techniques as a means,the effects of transducer frequency,array center-to-center distance,width,number,depth of focus,and the wedges on acoustic field distribution,focal area size,near-surface and far-surface detection capabilities were analyzed by measuring the focusing conditions,the size of the focal spot,the sound pressure distribution in the focal area and plotting the sound field amplitude distribution map.Actual detection is guided by finite element simulation results,and the effective detection parameter design rules applicable to engineering applications were given.Finally,based on the analysis results of phased array sound field characteristics,a custom sound field control method is proposed.Two consecutive focused sound fields within the workpieces were formed by controlling the focus law.Three kinds of sound field control modes,mode 1,mode 2,and mode 3,were designed.The size and amplitude of the focal area under different modes were analyzed by establishing three finite element models of sound field control modes.And the optimal sound field control method was obtained.The method was applied to the phased array ultrasonic testing of GH901 samples.Compared with the conventional focusing detect,the detection resolution and imaging quality of the phased-array focused scanning was improved by using the custom sound field control method in actual detection.The finite element model proposed in this study has practical application value for intuitive understanding the sound field distribution of phased array technique,guiding the optimization and designation of detection parameters,and assisting analysis of test results.Besides,the custom sound field control method based on finite element simulation can effectively improve the detection process and detection capability of the ultrasonic phased array.The custom sound field control method is expected to be widely promoted in production practice.