Simulation and experimental study of magnetic anomalies of defects in
high-energy beam electron welds
Abstract
In view of the current situation in which the existing
nondestructive testing (NDT) technology can hardly meet the demand of
aluminum alloy electron beam weld defect detection, a weak magnetic NDT
technology for aluminum alloy electron beam weld defects based on the
geomagnetic field is proposed. Using the finite element analysis method,
a simulation model of cracked aluminum alloy electron beam weld defects
is established, the distribution characteristics of the magnetic field
of cracked weld defects are determined, and the relationship between the
defect size and the number of magnetic anomaly characteristics is
analyzed. On this basis, a weak magnetic detection test was conducted on
cracked aluminum alloy electron beam welds. First, the magnetic anomaly
signal at the cracked weld was accurately extracted from the complex
original magnetic induction intensity signal by using wavelet transform,
and second, the least squares method was used to fit the curve to the
crack depth h and the magnetic anomaly amplitude ∆B at the crack. The
test results show that the magnetic induction intensity signal at the
crack has obvious characteristics, and the wavelet transform can
effectively extract and judge the weld crack signal from the weak
magnetic detection signal and improve the defect identification rate.
The crack amplitude ∆B is approximately positively correlated with the
depth h in a certain range, consistent with the simulation analysis
results. The feasibility of weak magnetic detection of cracks in
aluminum alloy electron beam welds is verified by simulation and
experimental analysis.
