The Research On Defect Detection System Of Electromagnetic Ultrasonic In Additive Manufacturing Based On FPGA

The additive manufacturing process is a process that is based on a digital model and forms a solid three-dimensional model by stacking materials layer by layer.It can break the shackles of design,break through the limitations of molds,and manufacture complex integrated parts.In the process of additive manufacturing,materials tend to form internal defects such as cracks and pores due to thermal shrinkage and layer-by-layer accumulation.Online detection and real-time repair are necessary auxiliary methods for additive manufacturing.Therefore,this article takes aluminum alloy as the research object and designs an electromagnetic ultrasonic defect detection system based on "STM32-FPGA" as the main control system for the detection of internal defects in the additive manufacturing process.The main research work is as follows:Aiming at the high temperature conditions of the additive manufacturing process,the detection methods and mechanisms of piezoelectric ultrasonic and electromagnetic ultrasonic are compared,electromagnetic ultrasonic is selected as the detection method of additive manufacturing process,and longitudinal wave is used as the detection waveform.According to the physical model of the sound field,magnetic field and electric field of the energy conversion process,the parameters of defect detection based on aluminum alloy are configured,and the transducer probe is designed.The overall design of the hardware circuit of the electromagnetic ultrasonic testing system is mainly designed for the electromagnetic ultrasonic excitation signal generation module,the signal receiving module for echo signal extraction and processing,and the main control module for system working sequence and echo signal data storage and forwarding.The overall software design of the main control module based on the "STM32-FPGA" dual control system is carried out to realize the functions of system working sequence generation,signal conversion,data storage and forwarding.The finite state machine is used to realize the initial parameter configuration of the system,the conversion of various working states,and the shutdown and start of the system.The whole inspection system is debugged at the board level,and the aluminum alloy is used for inspection experiments.The experimental results show that the inspection system designed in this paper can detect internal defects with a depth of 5mm and a size of 0.5mm.