Integrated Design Of High Frequency Eddy Current System Based On ARM And LabVIEW

With the increasing demand of carbon fiber reinforced plastic(CFRP) in the field of aerospace, it is very necessary to detect damage in CFRP in time, to avoid major safety risks caused by structural damage. There are a lot of damage detection methods for CFRP. Eddy current testing is used widely as a common NDT(Non Destructive Testing) technology because of its simple structure, non-contact and no coupling agent. CFRP is composed of conductive carbon fiber and insulating matrix, so CFRP presents weak electrical conductivity and thus we can use eddy current testing technology to detect damage in CFRP.In this thesis, we use the eddy current testing technology to detect damage in CFRP. In order to meet the different needs of exciting signal frequency in different occasions, a high frequency eddy current testing system with a maximum frequency as high as 10 MHz is designed and the testing frequency can be adjusted. The system has the advantages of high integration, small size and it is very convenient to use the system to detect damage. The main contents in this thesis are listed as follows:Firstly, the hardware circuit of the system is designed according to the proposed scheme, including a power module, a signal processing module, an automatic balancing module, a lock-in amplifier module, a core module based on STM32, a sinusoidal signal generator module, a data acquisition module, an automatic balancing control module and a USB communication module.Secondly, the software of the system is realized, including upper computer software and lower computer software. The main funntion of the upper computer is to control the work of the lower computer and the process of testing, and the main function of the lower computer is to perform different operations according to the commands from the upper computer.Thirdly, experimental verification are conducted and the high frequency eddy current testing system has the ability of detecting common damage of CFRP, including crack, impact damage and delamination damage. The results prove the feasibility and practicability of the system.