Research On Part Stress Detection System In Additive Manufacturing Process

Additive manufacturing specimens are under the interaction of physical fields such as temperature field and stress field,which causes complex internal stress in the specimens.The deformation caused by the release of internal stress will affect the forming rate and mechanical properties of the specimen,so the detection of internal stress is particularly important in the process of additive manufacturing.Compared with other stress detection methods,ultrasonic detection method has the advantages of fast detection speed and high accuracy,and can be applied in additive manufacturing process.In this paper,the thin-walled titanium alloy specimen of aircraft casing is taken as the research object.According to the acoustic-elastic theory,the theoretical research of ultrasonic stress detection system is carried out,and the ultrasonic stress detection system is designed.The main research contents are as follows:The critical refracted compressional wave(LCR),which is the most sensitive to stress,was selected to solve the difficulty of detection due to the small change of wave velocity caused by internal stress,and the first critical angle of LCR wave was determined according to Snell’s law.The acoustoelastic theoretical model of compressional wave is emphatically studied.The acoustoelastic model of compressional wave is studied emphatically,and the conversion relationship between stress and detection time is obtained through derivation and simplification of the formula of stress-sound velocity.The overall structure of the ultrasonic stress detection system is designed,and the hardware circuit detection system with FPGA as the core chip is established,which includes two modules of ultrasonic transmission and reception.The ultrasonic transmitting module is composed of FPGA,peripheral interface circuit,ultrasonic transduce driving circuit and transmitting probe.The signal receiving module is mainly composed of receiving probe,signal conditioning circuit and voltage comparator,etc.The design and simulation of configuration circuit,power circuit,interface circuit,probe drive circuit,filter amplifier circuit and the selection of core chip are given.Verilog HDL is used to complete the internal timing logic control of FPGA,including real-time communication,timing module,data transmission and storage and other functions.Finally,according to the basic idea of "part-module-system",the whole inspection system is debugged,and the stress test is carried out on the titanium alloy specimens under different stress states.The results can effectively reflect the distribution of internal stress in the specimen,and based on ultrasonic the stress detection system provides a deformation control method in the additive manufacturing process.