Development Of A New ACFM System For Weld Surface Crack Defect Detection

This thesis aims at exploring the weld surface defect ACFM detection and developing a new ACFM detection system.The thesis bases the AC electromagnetic detection technology,and combines the common weld characteristics and nature,and compares the different weld detection technology,and builds the weld ACFM detection model with ANSYS.Design the new coil and GMR probe,and optimizes the signal generator to get batter sinusoidal signal,and enhances the system accuracy and reliability.Design the new GMR probe ACFM detection system including the hardware platform and software platform,and then finish the ACFM detection system with function of signal acquisition,signal processing and defect judgment.This thesis study includes below contents.(1)Theory study and simulation analysis of weld surface defect ACFM detectionCollect classified the common weld surface crack defects and combine their character and compare different construction weld surface defect.Build the ACFM weld detection model with ANSYS based the ACFM theory,and apply the ideal boundary conditions and sine encourage single.Then get the defect surface magnetic field intensity to analyze the change rule.(2)Design and optimize weld surface crack detection probe and build ACFM system.Based on the old ACFM detection system,design the coil ACFM probe.And design GMR porbe ACFM detection system.Develop the GMR senor circuit and AD620 amplification circuit.And put the GMR senor and AD620 into the probe together.Design the ACFM system lithium battery power and voltage regulator circuit and improve the defect recognition software(3)coil and GMR probe ACFM detection system experiment testUse two kinds of ACFM detection system to test the test-piece including flat weld,pipeline weld and T weld.And then experiment the probe lift-off.Compare the BX?BZ curves of two different ACFM system,find the GMR ACFM system have good advantage.