Analysis of Tilt Effect on Notch Depth Profiling Using Thin-Skin Regime of Driver-Pickup Eddy-Current Sensor

Electromagnetic eddy current sensors are commonly used to identify and quantify the surface notches of metals. However, the unintentional tilt of eddy current sensors affects results of size profiling, particularly for the depth profiling. In this paper, based on the eddy current thin-skin regime, a revised algorithm has been proposed for the analytical voltage or impedance of a tilted driver–pickup eddy current sensor scanning across a long ideal notch. Considering the resolution of the measurement, the bespoke driver–pickup, also termed as transmitter–receiver (T-R) sensor is designed with a small mean radius of 1 mm. In addition, the T-R sensor is connected to the electromagnetic instrument and controlled by a scanning stage with high spatial travel resolution, with a limit of 0.2 μm and selected as 0.25 mm. Experiments were conducted for imaging of an aluminium sheet with seven machined long notches of different depths using T-R sensor under different tilt angles. By fitting the measured voltage (both real and imaginary part) with proposed analytical algorithms, the depth profiling of notches is less affected by the tilt angle of sensors. From the results, the depth of notches can be retrieved within a deviation of 10% for tilt angles up to 60 degrees.

Analysis of Tilt Effect on Notch Depth Profiling Using Thin-Skin Regime of Driver-Pickup Eddy-Current Sensor

Electromagnetic eddy current sensors are commonly used to identify and quantify the surface notches of metals. However, the unintentional tilt of eddy current sensors affects results of size profiling, particularly for the depth profiling. In this paper, based on the eddy current thin-skin regime, a revised algorithm has been proposed for the analytical voltage or impedance of a tilted driver–pickup eddy current sensor scanning across a long ideal notch. Considering the resolution of the measurement, the bespoke driver–pickup, also termed as transmitter-receiver (T-R) sensor is designed with a small mean radius of 1 mm. Besides, the T-R sensor is connected to the electromagnetic instrument and controlled by a scanning stage with high spatial travel resolution , with a limit of 0.2 μm and selected as 0.25 mm. Experiments have been out on the voltage imaging of an aluminium sheet with 7 machined long notches of different depths using T-R sensor under different tilt angles. By fitting the measured voltage (both real and imaginary part) with proposed analytical algorithms, the depth profiling of notches is less affected by the tilt angle of sensors. From the results, the depth of notches can be retrieved within a deviation of 10 % for tilt angles up to 60 degrees.

High-Q-Factor Tunable Silica-Based Microring Resonators

A high-Q-factor tunable silica-based microring resonator (MRR) is demonstrated. To meet the critical-coupling condition, a Mach–Zehnder interferometer (MZI) as the tunable coupler was integrated with a racetrack resonator. Then, 40 mW electronic power was applied on the microheater on the arm of MZI, and a maximal notch depth of about 13.84 dB and a loaded Q factor of 4.47 × 106 were obtained. The proposed MRR shows great potential in practical application for optical communications and integrated optics.

High-Q Slot Resonator Used in Chipless Tag Design

A retransmission chipless tag with multiple U-shaped slot resonators is proposed to cut down the cost of traditional tags with chips. Multiple side-by-side U-shaped slot structures of different lengths are printed on the microstrip line, and the two terminals of the microstrip line are connected correspondingly with two orthogonal ultra-wideband (UWB) transceiver antennas to form the retransmission chipless tag. The U-shaped slot resonator has high Q values and narrow impedance bandwidth. The bandwidth that each resonator adds to the protection bandwidth is 300 MHz. Several 6-bit coding U-shaped slot resonator chipless tags are designed and fabricated for comparison and measurement. Results show that the simulation and the measurement are in agreement. The slot width of the U-shaped slot resonator and the distance between the resonators are reduced, resulting in deepened spectrum notch depth of the resonator. Decreasing the dielectric constant of the substrate or increasing the thickness of the substrate increases the spectrum notch depth of the resonator.

Effect of Notch on Strain Rate Concentration Factor of 304 Stainless Steel Bar

In this study, the notch effect of different types of 304 stainless steel rod notch is studied because of the problem of difficulty in measuring the notch root strain of 304 rod stainless steel, and the parameters of the annular notch root are analyzed. The notch angle, notch depth, and notch root radius are the main parameters of the stress field affecting the annular notch, and the mathematical expression of the strain rate concentration factor is derived. In order to verify the accuracy of the theory, the mechanical model of 304 stainless steel bar is established by finite element and numerical simulation calculation. The results show that the theoretical and finite elements have a high degree of agreement. When the notch angle increases, both theoretical and finite elements show a downward trend. When the notch depth of 304 stainless steel bar increases, both theoretical and numerical simulations show an increasing trend. The notch root radius of 304 stainless steel bar increases with decreasing numerical simulation.

Experimental Investigation on the Tensile and Fracture Properties of Burst-Prone Coal under Quasistatic Condition

To study the tensile and fracture properties of the specimen under the quasistatic loading, the Brazilian disc splitting method and the notched semicircular bend (NSCB) method were used to test the tensile properties of coal specimens, and the fracture properties of NSCB specimens with different notch depths were tested and analyzed. The applicability of plane strain fracture toughness KIC and J-integral fracture toughness in evaluating the fracture properties of coal specimens was discussed. The influence of notch depth on the fracture toughness measurement of the NSCB specimen was studied. Combined with the surface strain monitoring of specimens during loading and the industrial CT scanning image of damaged specimens, the deformation characteristics of coal specimen under loads and the distribution law of crack after failure were analyzed. The results show that the NSCB test is suitable for measuring the tensile strength of a coal specimen; when the dimensionless notch depth is β = 0.28, the dispersion of plane strain fracture toughness KIC of the NSCB specimen is the smallest. Besides, the plane strain fracture toughness of coal is obviously affected by the notch depth and dimensionless stress intensity factor. The J-integral fracture toughness can be used to effectively evaluate the fracture performance of specimens.

High-Q-Factor Silica-Based Racetrack Microring Resonators

In this paper, ultrahigh-Q factor racetrack microring resonators (MRRs) are demonstrated based on silica planar lightwave circuits (PLCs) platform. A loaded ultrahigh-Q factor Qload of 1.83 × 106 is obtained. The MRRs are packaged with fiber-to-fiber loss of ~5 dB. A notch depth of 3 dB and ~137 pm FSR are observed. These MRRs show great potential in optical communications as filters. Moreover, the devices are suitable used in monolithic integration and hybrid integration with other devices, especially in external cavity lasers (ECLs) to realize ultranarrow linewidths.