Magnetic permeability perturbation testing (MPPT) owns the advantage of high sensitivity for deep buried defects steel pipes. The local wall thickness of pipes will change under complex working conditions, making it difficult to evaluate defects. The effects of uneven variation of wall thickness on magnetic permeability perturbation (MPP) is analyzed in the theoretical model. The magnetic field distribution in the case of thickening, thinning and normal thickness of the steel plate is studied in the simulation. The simulation and experiment results both show that the detection signal increases in case of thickness thinning while it decreases in case of thickness thickening. This study will contribute to the quantitative evaluation of defects in MPPT method.

The total focusing method (TFM) based on full matrix capture (FMC) is one of the hot spots in the research and application of ultrasonic testing. Compared with the traditional phased array method, the TFM can reduce the structural noise in ultrasonic testing for materials with inhomogeneity and anisotropy. In order to solve the problems of weak detection ability and low signal-to-noise ratio (SNR) in such materials, a new ultrasonic testing method that combines pulse compression technology with TFM is established in this work. First, the feasibility of this method is verified by numerical simulations based on the finite element method (FEM). Then, a TFM Ultrasonic testing system based on pulse compression technology is built and applied to the detection of defects in inhomogeneous and anisotropic materials. By comparing with traditional detection methods, it was verified that the Enhanced TFM with pulse compression technology of Encoding Modulation can effectively improve the detection ability and SNR of detection.

In this paper, the mode conversion of a single-mode ultrasonic beam is studied when passing across cracks of different depths in an aluminum plate. The single S0 mode is obtained using a wedge-angle beam probe. According to the aluminum properties and the plate thickness, the chosen operation frequency is sufficiently low to only permit the propagation of the A0 and S0 modes. Time signals along the propagation line path were acquired using a digital oscilloscope and a 2D Fast Fourier Transform was applied to the space-time map, and the wavenumber frequency map is obtained.

Eddy current testing can detect defects of carbon fibers in CFRP thanks to their conductive properties. In this study, the electric conductivity model of unidirectional laminated CFRP is investigated. The directional coil is sensitive to the fiber orientation, and the angular dependency of coil impedance over unidirectional laminated CFRP is studied. The conductivity model is developed based on the electromagnetic response of the directive coil.