Eddy Current Testing Of Internal Defect In Additive And Subtractive Hybrid Manufacturing

Integrating on-line non-destructive testing(NDT)technology into the process of additive and subtractive hybrid manufacturing(ASHM)to test internal defects produced from additive manufacturing process and removing the defects by subtractive manufacturing is an effective method to improve the quality of the final part fabricated by ASHM.Aiming at the testing requirements of internal defects in ASHM,this paper utilizes eddy current testing(ECT)technology to test internal artificial defects in ASHM sample and establishes a model for internal defect ETC based on volume integral equation method(VIEM).By combining numerical calculation,finite element simulation and experimental research,this paper investigates internal defect ECT in ASHM and provides theoretical guidance for the integration of ASHM and ECT.The main research contents are expressed as follows:(1)The model for internal defect ECT is established based on VIEM.The equivalent source model for internal defect ECT is derived from Maxwell's equations.The model of semiinfinite conductor without defect and FE model for internal defect ECT are established.(2)The electric field distribution of semi-infinite conductor without defect and the reactance increment of coil caused by different internal defects with different testing parameters are calculated and with the help of FE analysis,the effect of excitation frequency,the coil liftoff distance and defect features on the ECT signals of internal defects are studied.(3)The ASHM sample with internal artificial defects is fabricated using the methods of low laser energy,reverse stack and calibration groove positioning.The experimental research on ECT of different internal artificial defects is conducted out under different testing parameters and the law obtained by theoretical analysis is verified.(4)The effects of metal powder and chips on ECT signals of internal defects in ASHM are studied through the experimental method.The influence of temperature on ECT signals of internal defects is also studied through the combination of experimental research and theoretical analysis.