Luminescent photoelastic coating (LPC) methods are used to measure the full-field shear strain and its principal direction. These methods apply a liquid LPC onto the surfaces of the structures to be measured. To correct the effects of coating thickness non-uniformity on the quantitative shear strain measurements, a non-contact method is proposed for coating thickness measurements. The proposed method establishes a linear calibration curve between the thickness and the luminescent signal intensity of the test coating. The results show that the linear calibration curve of the intensity and the thickness of the LPC can be obtained by incorporating an appropriate concentration of the luminescent dye into the photoelastic coating. The correlation coefficient of this linear calibration curve is more than 0.999.
To perform measurements in special environments like narrow gaps, a coil-shaped carbon nanotube composite is structured as a sensing element. Its high conductive phase ratio offers superior response to magnetic field changes, outperforming traditional metals in non-contact magnetic sensing. The composite's feasibility for magnetic flux thickness measurement is validated through experiments, leading to the design of a thickness measurement and material discrimination system for real-time monitoring by an upper computer. The carbon nanotube composite can reach the sensitivity (65.32 mV/mm in planar, 63.54 mV/mm in curved) as traditional metal (69.8842 mV/mm). The flexible sensor system can maintain a high accurate measurement under curved conditions with the highest accuracy of 0.879% planar and 0.157% curved. This paper replaces traditional metal materials with the composite for non-contact thickness measurement and material discrimination in curved narrow gaps, offering a practical measurement system and a reference for using flexible composite materials with sensing and measurement capabilities in special environments.
To realize the thickness measurement by using the intrinsic flexible sensor, the conductive polymer composite is fabricated into a coil-shaped structure. The experimental results show that the effective value for the induced electromotive force (induced emf) of the composite coil decreases with the increase in thickness. The experimental results show that the sensitivity of the composite coil is 40.177 mV/mm, which is higher than that using a traditional metal coil with the same structure. With the distance of the composite coil or the metal sample position changing, the induced emf value of the composite coil also changes in response. When the sensitive element bends and deforms, the sensitivity of the thickness measurement will be lower than that of the measurement in the planar state under the same experimental conditions. However, all those changes in distance or curvature do not affect the relationship between the induced emf and the thickness. The aforementioned results have preliminarily verified the feasibility of using the coil-shaped composite to measure the thickness.
The monitoring of thickness using intrinsically flexible sensors remains an underexplored area in advanced manufacturing. Numerous challenges persist, including the lack of systematic studies on the correlation between materials and thickness response. In this article, integrated experimental analysis and finite element simulation are combined to investigate thickness measurement using coil-shaped carbon nanotube composite. This article focuses on six nonferromagnetic metallic materials and demonstrates effective thickness measurement, and the results reveal distinct response characteristics of the sensing element across different materials. However, these variations do not alter the fundamental relationship between induced electromotive force (emf) and thickness, namely, an increase in thickness corresponds to a decrease in induced emf. Through experiments and simulations, the increasing conductivity will lead to the induced emf of the sensing element decreasing and the measuring sensitivity increasing. Leveraging the feasibility of material recognition and thickness measurement across diverse materials, this article proposes a solution for multimetal thickness measurement. This approach facilitates tailored suggestions and recommendations for various engineering applications.
危险品化学品经营许可证（带存储）