Location

Seattle, WA

Start Date

1-1-1996 12:00 AM

Description

Detecting hidden damage at the second layer of lap joint structures in aircraft by using eddy current techniques is difficult because the cracks are usually located beneath the head of the rivets, which cause large signals that mask the relatively smaller signals from the second layer cracks. In addition, using lower frequency excitation for deeper penetration of the eddy currents reduces the signal-to-noise ratio. Several new techniques have been tried, such as using a sheet inducer to increase the penetration depth or using sensors that have a frequency independent response, to improve the signal to noise ratio [1, 2]. To better extract the information due to the cracks beneath the rivet at the second layer, we have developed a phase analysis of the magnetic field produced from the eddy currents induced by the sheet inducer.

Volume

15A

Chapter

Chapter 1: Standard Techniques

Section

Eddy Currents

Pages

401-408

DOI

10.1007/978-1-4613-0383-1_51

Language

en

File Format

application/pdf

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Jan 1st, 12:00 AM

Depth-Selective Squid Eddy Current Techniques for Second Layer Flaw Detection

Seattle, WA

Detecting hidden damage at the second layer of lap joint structures in aircraft by using eddy current techniques is difficult because the cracks are usually located beneath the head of the rivets, which cause large signals that mask the relatively smaller signals from the second layer cracks. In addition, using lower frequency excitation for deeper penetration of the eddy currents reduces the signal-to-noise ratio. Several new techniques have been tried, such as using a sheet inducer to increase the penetration depth or using sensors that have a frequency independent response, to improve the signal to noise ratio [1, 2]. To better extract the information due to the cracks beneath the rivet at the second layer, we have developed a phase analysis of the magnetic field produced from the eddy currents induced by the sheet inducer.