Structure Design And Optimization Of Lamb Wave Emats For Aluminum Plate

Aluminum plate with its own characteristics,being more and more widely used in many fields,such as aerospace,ships,trains,which resulted in increasingly demand for the quality of aluminum plates.Aluminum sheet in the production process will inevitably be a variety of defects,such as delamination,cracks,oxide film,which requires non-destructive testing method to detect these problems,in order to prevent the occurrence of major accidents.NDT electromagnetic ultrasonic testing technology for its without coupling agent,the advantages of simple operation,fast,is widely used in quality testing of aluminum sheet.The core part of the electromagnetic ultrasonic testing technology is electromagnetic acoustic transducer(EMAT),which may stimulate a variety of flexible ultrasonic aluminum sheet,this paper studies the electromagnetic ultrasonic Lamb wave,electromagnetic ultrasonic Lamb wave echo signal is weak and multi-mode ultrasound phenomenon to the solenoid adversely affected,this article focused on these two aspects of electromagnetic ultrasonic Lamb wave transducers structural design and optimization.(1)In this paper,electromagnetic ultrasonic Lamb wave echo signal is weak,proposes a method of using nanocrysta lline strip to optimize EMAT magnetic circuit,finite element simulation software EMAT model added ultrafine crystalline material before and after the simulation,the simulation results show that the addition of nanocrystalline strip EMAT to optimize the magnetic circuit,thereby enhancing the strength of the electromagnetic ultrasonic Lamb wave echo signals.(2)An increase of nanocrystalline laminations EMAT simulation calculations,change the twists and turns of the coil winding pitch,got the Lamb wave echo signals in different modes under different coil spacing;changing the magnetic field strength permanent magnet excitation current frequency,amplitude and pulse number,respectively of electromagnetic ultrasonic Lamb wave echo signal with the change o f the various parameters and trends,based on simulation results obtained for each parameter to select three values within a certain range,and orthogonal table lists,for the nine combinations of parameters finite element simulation,and finally get the optimum parameters added nanocrystalline EMAT after lamination of a group.(3)The simulation results were verified experimentally.By contrast,the experimental results are consistent with the simulation results,adding nanocrystalline strip Lamb wave EMAT improve the echo signal is weak and multi-mode Lamb wave phenomenon.