Simplistic, Efficient, and Low-Cost Crack Detection of Dielectric Materials Based on Millimeter-Wave Interference

Abstract

This paper proposes a simplistic, efficient, and low-cost method of millimeter-wave nondestructive testing (NDT) of dielectric material cracks based on millimeter-wave interference. A relationship between combining efficiency, phase difference, and amplitude difference was analyzed. We found that phase difference was the main factor that affects combining efficiency. A change in combining efficiency of more than 1% was caused by a phase-difference altering of greater than 1.2° in a specific range. A relevant model was simulated with CST, and the operating frequency and antenna spacing were optimized to enhance sensitivity of the measuring system. Then, a Ka-band NDT system was built to test the combining efficiencies of different cracks. The experimental results showed that for polytetrafluoroethylene (PTFE) plates with a thickness of 5 mm, cracks with a width of about 0.4 mm, which is about 0.07 λg, could be detected at 35 GHz. Experimental results, simulation results, and theoretical derivation are basically consistent. Large-scale online applications of this NDT method in various industries appear feasible due to the above characteristics.

Detection of Defects in a Dielectric Material by Thermo-Elastic Optical Indicator Microscopy

“…Conventional NDT technologies mainly include thermal imaging, ultrasound, computed tomography, eddy currents, and so on [7], [8], [9], [10], [11], [12]. Although these technologies have been successfully applied to various applications, requirements of them such as isolation from surrounding thermal radiation, coupling medium, expensive equipment and long measurement time limit their use in practical applications [13]. In this light, microwave imaging methods have advantages that it is relatively insensitive to the surrounding environment and consists of a simple and inexpensive measurement system [14].…”