Electromagnetic methods for measuring material properties of cylindrical rods and array probes for rapid flaw inspection

Thumbnail Image
Sun, Haiyan
Major Professor
John Bowler
Committee Member
Journal Title
Journal ISSN
Volume Title
Research Projects
Organizational Units
Organizational Unit
Electrical and Computer Engineering

The Department of Electrical and Computer Engineering (ECpE) contains two focuses. The focus on Electrical Engineering teaches students in the fields of control systems, electromagnetics and non-destructive evaluation, microelectronics, electric power & energy systems, and the like. The Computer Engineering focus teaches in the fields of software systems, embedded systems, networking, information security, computer architecture, etc.

The Department of Electrical Engineering was formed in 1909 from the division of the Department of Physics and Electrical Engineering. In 1985 its name changed to Department of Electrical Engineering and Computer Engineering. In 1995 it became the Department of Electrical and Computer Engineering.

Dates of Existence

Historical Names

  • Department of Electrical Engineering (1909-1985)
  • Department of Electrical Engineering and Computer Engineering (1985-1995)

Related Units

Journal Issue
Is Version Of

The case-hardening process modifies the near-surface permeability and conductivity of steel, as can be observed through changes in alternating current potential drop (ACPD) along a rod. In order to evaluate case depth of case hardened steel rods, analytical expressions are derived for the alternating current potential drop on the surface of a homogeneous rod, a two-layered and a three-layered rod. By fitting model results to multi-frequency ACPD experimental data, estimates of conductivity, permeability and case depth are found. Although the estimated case depth by the two-layer model is in reasonable agreement with the effective case depth from the hardness profile, it is consistently higher than the effective case depth. This led to the development of the three-layer model. It is anticipated that the new three-layered model will improve the results and thus makes the ACPD method a novel technique in nondestructive measurement of case depth.;Calculations of eddy currents are performed for a two-layer conducting rod of finite length excited by a coaxial circular coil carrying an alternating current. By truncating the solution region to a finite length in the axial direction, the magnetic vector potential can be expressed as a series expansion of orthogonal eigenfunctions instead of as a Fourier integral. Closed-form expressions are derived for the electromagnetic field in the presence of a finite a two-layer rod and conductive tube. The results are in very good agreement with those obtained by using a 2D finite element code.;A new probe technology is designed which has an enhanced flaw detection capability and can reduce inspection time through the use of multiple magnetic field sensing elements. A preliminary Hall array probe has been built and test with eight individual Hall sensor ICs and a racetrack coil. Electronic hardware is developed to interface the probes to an oscilloscope or an eddy current instrument. To achieve high spatial resolution and to limit the overall probe size, high-sensitivity Hall sensor arrays were fabricated directly on a wafer using photolithography techniques and then mounted in their unencapsulated form. The electronic hardware is updated to interface the new probes to a computer.

Subject Categories
Sat Jan 01 00:00:00 UTC 2005