Current Testing Problems Research Articles

Three-Dimensional Simulation of Remote Field ECT using the Ar Method and a New Formula for Signal Calculation

ABSTRACT In this article, a three-dimensional (3D) edge-element finite element method (FEM) code of the Ar method is upgraded to enable the 3D simulation of remote field eddy current testing (RFECT) problem by introducing a new formula for the pickup signal calculation. The validity of the proposed formulation and the corresponding implementation are verified by comparing numerical results of the 3D code with the measured signals and those of an axisymmetric code. The numerical results show that, although both the conventional formulation and the proposed method are for a nonmagnetic tube, the upgraded code has a more satisfactory simulation accuracy for a tube of ferromagnetic material. It is also proven that the upgraded Ar-method code is very efficient in the 3D simulation of the RFECT problem and even a normal PC can accomplish the calculations.

Numerical techniques in finite element analysis of eddy current testing problem

Several types of finite element methods have been developed and shown the validity and the effectiveness for eddy current testing (ECT) problem. However, it is difficult to analyze the finite element model including two or more objects whose positions relatively change, such as conductor plate and ECT probe. Furthermore, it takes a large amount of computer resources to compute an accurate finite element model for a natural crack, because of the complex shapes and the narrow gap. In this paper, a superposition method to avoid the finite element mesh regeneration for the relative position change is presented, and the method is applied to the ECT probe with a ferrite core. Furthermore, the finite element model for the natural crack is shown and the model is applied to the ECT problem with the fatigue crack.

Finite element model of natural crack in eddy current testing problem

Eddy current testing (ECT) is one of the nondestructive inspection techniques to detect cracks and eddy current analysis is important for ECT. However, it is difficult to model a natural crack in finite element method (FEM), because of the narrow gap and the complex shape. In this paper, a finite element model for the natural crack is proposed. The conductivity for the finite element model is expressed by a tensor. In the proposed finite element, the change in crack shape and contact condition are simulated by changing the coefficients of the conductivity tensor. The proposed model is applied to a conductor plate model with a crack and a coil. The computation results are compared with the computation results of an artificial crack model. The validity of the proposed method is shown by the computation results.

Test challenges in nanometric CMOS technologies

The current trends in decreasing the minimum feature sizes in CMOS technologies are producing new failure mechanisms for which the classical test methods become inefficient. This situation causes a growing concern in the design and test communities due to the fact that the advances in integration advance faster than the ability of test specialists in providing the required strategies to test the new circuits. If the current levels of reliability are to be maintained new paradigms to guarantee the quality levels of the future megatransitor chips will be required. In this paper, after reviewing the technology trends in CMOS technologies, the emerging failure mechanisms of these technologies are analyzed. The challenges facing testing in nanometric technologies are explored in terms of voltage test difficulties as well as current test (IDDQ) problems and solutions.

A Computing Method of Functional Derivatives with respect to System Parameters of Steady-state Electromagnetic Field Equations

The paper presents a computing method of functional derivatives with respect to system parameters such as magnetic resistivity, electric conductivity and source current in steady-state electromagetic fields. The method is based on Gataux differential, namely a kind of sensitivity analysis, and the functional derivatives are proved to be calculated by explicit forms of the solutions of the electromagnetic field equation and its adjoint equation. The methodis applied in success to a simple eddy current testing problem

A displacement scheme with drilling degrees of freedom for plane elements

AbstractA scheme of boundary displacements with drilling degrees of freedom for plane elements is presented. The scheme is free from zero displacement modes and allows the development of hybrid finite elements with vertex and mid‐side nodes, each node including a drilling degree of freedom besides the translational ones. Four quadrilateral isoparametric hybrid stress elements are implemented, and numerical results for some current test problems are given.

Application of a perturbation method to the solution of eddy current testing problems

This paper presents an analytical solution for the change of the impedance of a double conductor line due to eddy currents induced in presence of an infinitely long horizontal cylindrical flaw with vertically symmetric cross-section. The solution, found by a perturbation method, is applicable in the case the conductivities of the flaw and of the surrounding material do not differ by much. Numerical results for flaws of circular and elliptic cross-sections are presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

On the application of hinged finite elements to eddy current problems

A Finite Element method that uses a hinged weighting function is applied to 1-D and 2-D eddy current problems. A method of choosing the hinge parameters such that the resulting piecewise linear function approximates an exponential weighting function is developed. A special purpose quadrilateral element that incorporates the hinged weighting function is derived. The hinged elements are used to solve 1-D and 2-D eddy current test problems. Computed results that illustrate the advantages of the hinged F.E.M. are presented.