Abstract
The paper proposes a capacitance-sensor-array-based imaging system to detect water leakage inside insulating slabs with porous cells, such as anechoic acoustic rubber tiles. The modeling is conducted by using the finite element method to obtain the electrical potential distribution and sensitivity map with the proposed capacitance sensor array. An experimental test setup, which is composed of an eight-electrode capacitance sensor array and a commercialized capacitance bridge instrument for measurement, is developed. Experiments regarding different leakage scenarios are carried out by using the test setup. Preliminary results standing for different water leakage cases, which are based on the experimental data obtained from the test setup, are presented and depicted as images reconstructed by using different algorithms including the linear back projection (LBP), the projected Landweber iteration, and the total variation regularization. These results demonstrate that the proposed capacitance sensor array is feasible and has a great potential for imaging of water leakage inside insulating slabs with porous cells. A cost-effective capacitance measurement circuit for practical applications is also proposed and simulated.
Highlights
IntroductionMost modern submarine hulls are covered with anechoic acoustic rubber tiles
To enhance submarine stealth, most modern submarine hulls are covered with anechoic acoustic rubber tiles
The anechoic acoustic rubber tiles usually have a structure with porous cells inside, which are capable of absorbing active sonar signals from enemy vessels for detecting purposes, preventing acoustic noise from the submarine interior, which can be detected by passive sonar, from being transmitted outside [1]
Summary
Most modern submarine hulls are covered with anechoic acoustic rubber tiles. The debonding or detachment of rubber tiles from the steel hull may lead to water leakage into the porous cells, which will absorb less acoustic signals passing through and degenerate the rubber tiles’ acoustic performance. For this reason, one daily routine submarine maintenance task is to inspect whether water has already leaked into the porous cells inside the anechoic acoustic rubber tiles, in the early stage of water permeating due to adhesive debonding. Nondestructive test methods based on different sensing techniques including X-ray [5], microwave [6,7,8,9], Sensors 2019, 19, 2514; doi:10.3390/s19112514 www.mdpi.com/journal/sensors
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