Junjun Xin

Nondestructive Inspection Using Rotating Magnetic Field Eddy-Current Probe

Rotating magnetic field eddy-current (RoFEC) probe for nondestructive evaluation of steam generator tubes in a nuclear power plant offers an alternate method that has compact configuration and higher speed compared to traditional bobbin coil, rotating probe coils, and array probes. This paper investigates the feasibility of the proposed RoFEC eddy-current probe which is composed of three windings excited by three-phase ac current and does not require mechanical rotation of probe. Results of finite-element modeling using reduced magnetic vector potential (RMVP) formulation are presented for modeling the inspection of ferromagnetic and nonferromagnetic tubes. Design parameters of the excitation coils and GMR pick-up sensor are optimized by means of a parametric study.

Novel Transceiver Rotating Field Nondestructive Inspection Probe

Metallic tube inspection techniques using eddy current probes have evolved over the years from those employing a single bobbin coil to rotating coils and arrays, in an attempt to improve the speed and reliability of inspection. This paper presents a novel eddy current transceiver probe design that uses a rotating electromagnetic field. The transceiver coils consist of three identical windings located 120° apart on the same physical axis. A three-phase sinusoidal current source is used for exciting the coils. The phase voltages are identical in amplitude, but 120° apart in phase. The rotating magnetic field generated by the three-phase current is sinusoidal in space and time and so are the induced eddy currents in the tube wall. The sensor achieves mechanical rotating probe functionality by electronic means and eliminates the need for mechanical rotation. The terminal voltages of the three-phase windings can be measured during the scan. The defects axial and angular position can be estimated by analyzing the amplitude and phase of the sum of the three terminal voltage signals. The probe is sensitive to defects of all orientations and is as effective as conventional rotating pancake coil probes while offering the advantages of high inspection speed and greater reliability, since the probe does not rotate mechanically. A 3-D finite-element model based on reduced magnetic vector potential Ar, V-Ar formulation was developed to simulate and predict the response of the probe to a variety of defects. A prototype unit consisting of a probe connected to a three-phase constant current source and data acquisition system was developed and tested. Experimental results validating the simulation model and demonstrating the feasibility concept are presented.

Nonlinear, non-stationary image processing technique for eddy current NDE

Automatic analysis of eddy current (EC) data has facilitated the analysis of large volumes of data generated in the inspection of steam generator tubes in nuclear power plants. The traditional procedure for analysis of EC data includes data calibration, pre-processing, region of interest (ROI) detection, feature extraction and classification. Accurate ROI detection has been enhanced by pre-processing, which involves reducing noise and other undesirable components as well as enhancing defect indications in the raw measurement. This paper presents the Hilbert-Huang Transform (HHT) for feature extraction and support vector machine (SVM) for classification. The performance is shown to significantly better than the existing rule based classification approach used in industry.

Novel rotating field probe for inspection of tubes

Inspection of steam generator tubes in nuclear power plants is extremely critical for safe operation of the power plant. In the nuclear industry, steam generator tube inspection using eddy current techniques has evolved over the years from a single bobbin coil, to rotating probe coil (RPC) and array probe, in an attempt to improve the speed and reliability of inspection. The RPC probe offers the accurate spatial resolution but involves complex mechanical rotation. This paper presents a novel design of eddy current probes based on rotating fields produced by three identical coils excited by a balanced three-phase supply. The sensor thereby achieves rotating probe functionality by electronic means and eliminates the need for mechanical rotation. The field generated by the probe is largely radial that result in induced currents that flow circularly around the radial axis and rotating around the tube at a synchronous speed effectively producing induced eddy currents that are multidirectional. The probe will consequently be sensitive to cracks of all orientations in the tube wall. The finite element model (FEM) results of the rotating fields and induced currents are presented. A prototype probe is being built to validate simulation results.

Nondestructive inspection using Rotating Field Eddy Current (RoFEC) Probes

The use of Rotating Field Eddy Current (RoFEC) Probe for inspection of metallic steam generator tubes in nuclear power plant offers higher operation speed and sensitivity relative to traditional rotating probe coil and array probes. This paper investigates the feasibility of the RoFEC probe which does not require rotating the coils mechanically. Results of finite element modeling and simulation results with Reduced Magnetic Vector Potential Formulation (RMVP) are presented for non-magnetic and ferromagnetic tube inspection.

GPU implementation of simultaneous iterative reconstruction techniques for computed tomograpy

This paper presents implementation of simultaneous iteration reconstruction techniques on GPU with parallel computing languages using CUDA and its intrinsic libraries on four different Graphic Processing (GPU) cards. GPUs are highly parallel computing structures that enable acceleration of scientific and engineering computations. The GPU implementations offer significant performance improvement in reconstruction times. Initial results on the Shepp-Logan phantom of size ranging from 16×16 to 256×256 pixels are presented.

High performance wireless sensors system for structural health monitoring

Continuous structural health monitoring (SHM) uses permanently mounted sensor networks on critical locations of a structural component. In-situ wired sensors require a large amount of cabling for power and data transfer, which can drive up costs of installation and maintenance. Hence the need for developing wireless sensors for SHM. The major obstacles preventing the widespread use of wireless sensor networks (WSN) for SHM is the availability of portable, low cost, low powered, low footprint, and high SNR based instrumentation. This paper presents a wireless sensor system that could be interfaced with piezoelectric transducers for the identification of anomalous events using ultrasonic techniques. Power aware algorithms are used to coordinate the actuator-sensor network interaction with a central processing server, where appropriate signal processing techniques are used to quantify the damage in terms of severity.

Modeling of new/commercial eddy current probe for steam generator inspection

Computational models serve an important role in Non-Destructive Evaluation applications for enabling effective use of the technology. The solution of simulation models provide valuable insight into the underlying physics, help visualize the field/flaw interaction and help optimize sensor design and develop algorithms for interpreting the measured signals. This paper presents a simulation model for predicting defect signals in Steam Generator tube inspections using commercial eddy current probe used in industry. The model, based on finite element analysis, uses reduced vector potential formulation and novel strategies for modeling ferrite core probes. Experimental validations of model predictions for a number of defect geometries are presented.