Issue 28

B. Ye et alii, Frattura ed Integrità Strutturale, 28 (2014) 32-41; DOI: 10.3221/IGF-ESIS.28.04

Configuration

Operation

50 20 0.1

N m

ρ α β

1 2

0.1

q 0

(8×40038.5) −1

C

500

t max

e 0.01 Table 1 : IACA configuration.

Thickness t mm

Permeability μ

Structures Conductivity σ MS/m

Layer 1 Layer 2 Defect

18.5 18.5

1 2

μ 0 μ 0

0

μ 0 Table 2 : Structure parameters.

Item

Quantity

Number of turns N Inside radius r 1 mm Outside radius r 2

330 3.0 5.11

mm

Length l mm Inductance L 0 Resistance R 0 Frequency f 0

20.70 1.02 19.84

mH

Ω

Hz

400 0.0

mm

Liftoff l 1

Table 3 : Coil parameters. In the actual computing process, we find themethod needs a long computing time to find the global optimum, when the estimation of the objective function requires a field analysis bymeans of the FEM. So, we propose a novel methodwith a signal database consisting of impedance signals of different size computed by FEM in advance, applied to the optimization of defect inspection, to reduce the computing time for the whole optimization. The identification results using IACA are shown in Tab. 4. At the same time, the identification results using the least square method are shown in Tab. 5.

Group 1

Group2

Group 3

Group 4

True length (mm) TrueHeight (mm) TrueDepth (mm)

16 0.8 1.2

17

18 0.8 1.2

19

1

1

1.7

1.7

Estimated length (mm) EstimatedHeight (mm) EstimatedDepth (mm)

16.26 0.84 1.22 1.63

17.16 1.04 1.73 0.94

17.83 0.77 1.15 -0.94 -3.75 -4.17

18.74 1.04 1.66 -1.37

Length error (%) Height error (%) Depth error (%)

5

4

4

1.67

1.76

-2.35

Table 4 : Identificationof defect using IACA.

39