Analysis of Dual Semicircle Shape CSRR Sensor for Dent Detection on Teflon Coated Metal Surfaces

A planar microstrip transmission line with dual semicircle complementary split-ring resonator (CSRR) is proposed as a high sensitivity RF sensor for detecting non-uniformity of the surface of the thin metal plate. In automotive industries, a surface deformity on lightweight aluminum sheet components is a serious problem. Due to the uneven surfaces of the parts, typical flaws such as dents, dings, and waviness are not visible in the early stages of production. The defects, if ignored at an early stage, may lead to more production cost. So in this paper, we investigated the detection of flaws on the thin aluminum sheet under variable load conditions. The dual ring semicircle CSRR loaded microstrip transmission line implemented on Teflon (thickness = 0.08 mm) coated aluminum sheet (thickness = 3 mm) which behave as an RF sensor. By varying the depth of the dent from 1 to 2.05 mm on the aluminum sheet, the sensor was able to find the maximum frequency shift (nearly 800 MHz frequency) as compared to faultless (without a dent) aluminum sheet, in both simulations as well as in measurement conditions. As compared to circular shape CSRR, the dual ring semicircle CSRR has a high bonding effect between the electric field and metal sheet, which gives a more accurate prediction of dent portion on a thin metal sheet. This proposed compact RF sensor can be effectively utilized for crack avoidance in fiber optic glasses, crack avoidance in the gas pipeline, aircraft plate etc. By comparing frequency shift of the proposed CSRR sensor is more accurate, even invisible non-uniformities can be easily detected and thus can be prevented at an early stage to avoid any damage.