To overcome the shortcomings of the existing rectangular electrode coplanar capacitive sensor used in the non-destructive detection, such as poor adaptability to the uneven distribution of medium, small dynamic range and low sensitivity, a two channel coplanar capacitive sensor with triangular electrode is proposed, and a method of applying it to non-destructive detection is discussed. Firstly, the sensor structure and mathematical model of the novel coplanar capacitive sensor is established, and the sensor related performance indexes are analyzed and defined. By establishing a three-dimensional simulation model of the sensor, the influence of sensor structure parameters such as working electrode, shielding electrode, protective electrode and substrate thickness on its performance indexes is systematically analyzed. Through studying the correspondence between different performance indexes and structural parameters, the linear relationship between the penetration depth of sensor and the electrode structure parameters is established. Finally, experiments are conducted to evaluate its performance on non-destructive detection.
Particle charging is a universal phenomenon due to the collision and contact between particle and particle, particle and wall in the powder pneumatic conveying process. The linear electrostatic sensor matrix (LESM) is able to capture the dynamic information of the moving charged particles in pipeline, whose spatial filtering characteristics has been employed to obtain the flow velocity of particles in gas-solid flow. The spatial filtering characteristics of LESM are closely related to its dynamic sensitivity (DS) distribution. In this paper, the 3D simulated model of the LESM was built by finite element method and the effects of its structural parameters on its dynamic sensitivity and spatial filtering characteristics were studied. The geometric dimensionless model of dynamic sensitivity of LESM was further established. Finally the experiment was carried out on a gravity-fed solids flow rig, and the experimental results was verified the simulation results.
For the mechanical industry, bolts are an important guarantee for the safety of connection between parts. The traditional method for monitoring bolt loosening is mainly through human judgment, but this method has a large error and cannot be monitored online. At present, the dynamic change process of the bolt loosening can be learned in more detail through the Lamb wave monitoring technology. In this paper, the piezoelectric transducer(PZT) is used to generate the Lamb wave in aluminum structure to monitor the looseness of the bolt on it. The signal with bolt looseness information received by another PZT is analyzed and processed. The S0 modal of the signal is chosen to extract the amplitude of it. After analysis it can be seen that the amplitude of the S0 modal reduces as the bolt gone loose. The relationship between the amplitude and bolt looseness have been drowned. And the functional relationship is presented.
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