Naiguang Lei

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.

Rotating field eddy current (RoFEC)-probe for steam generator inspection

A novel design of eddy current probe based on rotating magnetic fields is presented for the inspection of steam generator tubes in nuclear power plants. A major advantage of the rotating field probe is that it offers the same functiona lity as that of a rotating probe coil without the need for mechanical rotation, which in turn translates into higher operating sp eed. The probe design is also sensitive to cracks of all orientations in the tube wall.

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 based numerical modeling for eddy current non-destructive evaluation

Numerical models serve an important role in eddy current non-destructive evaluation applications. The results of computational models provide meaningful insight into the underlying physics, help theoretically visualize the field/sample interaction and help optimize sensor design and assist algorithms developing for interpreting the measured signals. However, three dimensional computational models can be time consuming. This paper presents a fast and efficient GPU based numerical model for simulating eddy current testing techniques. The model, based on boundary integral method, uses novel matrix compression techniques to optimize the solver performance on GPU architectures. Validation results of model predictions for a number of sample geometries are presented.

Storage strategies of eddy-current FE-BI model for GPU implementation

In the past few years graphical processing units (GPUs) have shown tremendous improvements in computational throughput over standard CPU architecture. However, this comes at the cost of restructuring the algorithms to meet the strengths and drawbacks of this GPU architecture. A major drawback is the state of limited memory, and hence storage of FE stiffness matrices on the GPU is important. In contrast to storage on CPU the GPU storage format has significant influence on the overall performance. This paper presents an investigation of a storage strategy in the implementation of a two-dimensional finite element-boundary integral (FE-BI) model for Eddy current NDE applications, on GPU architecture. Specifically, the high dimensional matrices are manipulated by examining the matrix structure and optimally splitting into structurally independent component matrices for efficient storage and retrieval of each component. Results obtained using the proposed approach are compared to those of conventional CPU imple...

Implementation of 2D computational models for NDE on GPU

This paper presents an attempt to implement a simulation model for electromagnetic NDE on a GPU. A sample electromagnetic NDE problem is examined and the solution is computed on both CPU and GPU. Diffierent matrix storage formats and matrix-vector computational strategies will be investigated. Analysis of the storage requirements for the matrix on the GPU is tabulated and a full-timing breakdown of the process is presented and discussed.

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.

SOLUTION OF INVERSE PROBLEM USING TIME REVERSAL TECHNIQUES

Inverse problem solutions in NDE can be broadly classified as model‐based approach and system‐based approach. In model‐based approach an accurate forward model is used in an iterative framework to provide a defect shape that minimizes the error between the measured signal and a simulated signal. However this approach results in repeated executions of a three dimensional forward model in each iteration, making it computationally demanding. This paper presents a direct approach to inversion using principles of time reversal. The feasibility of the approach is demonstrated via application to microwave NDE data. A two‐dimensional finite difference time domain model for simulating the propagation of forward and time reversed wave fields is first developed. The key advantage of the approach is that it provides a model‐based inversion method that is not iterative. Simulation and experimental results validating the approach are presented.

MODEL BASED STUDY OF TIME REVERSAL IMAGING IN MICROWAVE NDE

This paper presents a feasibility study of imaging defects in dielectric materials using principles of time reversal with microwaves. The principle is demonstrated using a two‐dimensional finite difference time domain model for simulating the propagation of forward and time reversed wave fields. The scattered electric field is recorded on a linear array of receivers; time reversed and propagated backwards using the model to highlight the scatterer/defect. Simulations results validating the approach are presented. Initial results demonstrate the ability of the technique to image defects.