EMAT is a transducer used to inspirit and receive testing signal,in order to get ultrasound signal with certain frequency and amplitude,it's necessary to design rationally coil probe for improving testing efficiency.Hollow cylinder coil probe on the basis of introducing principle of RLC impulse excitation source is proposed.Effect of that kinds of coil parameters on inspiriting signal source and testing effect is analyzed particularly.Aiming at double function between inspiriting and energy conversion of probe,which provides theoretical and practical guidance for design of coil probe by RLC impulse exciting source.Probe coil and experimental testing system are designed according to analysis results,experiment proves the correctness of theoretical analysis.
As a result of superior property of lock-in ampfilier(LIA)technique in weak signal testing and present problem that electromagnetic acoustic testing is high noise and low conversion efficiency,this paper presented an electromagnetic acoustic receiving system combined with analog and digital by the core of the lock-in amplifying technique based on cross-correlation theory.The receiving circuit was designed around PLD consisted of AD630,which contained signal channel,reference passage and correlator.The experimental results prove that the receiving system has high accuracy and it improves signal-to-noise ratio.
Modeling and Simulation from EMAT are a method to comprehend the physical process concerning electromagntic exciting and receiving.Researcher can increase EMAT's energy transduction efficiency by researching principle and optimizing parameter based on this method.In order to obtain the best designing parameter and rule according to electromagnetic surface wave transducer,EMAT's model is established by means of finite element methods and,simulate three kinds of exciting loop,and analysis the relation between paranoia magnetic field,loop,lift-off value,and Eddy current;several major parameters of the EMAT are found,and the law of every parameter impacting on the EMAT is obtained.It is pointed every parameter must be chose as according to the practical testing condition to improve detection efficiency.
