Non-contact laser displacement measurement system used for cement-based materials

Abstract

The present invention relates to a non-contact laser displacement measurement system used for cement-based materials, which belongs to the strain measurement technique of cement-based gelling materials in processes of hydration as well as dehydration. The system is characterized in that: in the aspect of hardware constitution, the system comprises a laser displacement sensor and fixing supports thereof, a temperature signal sensor, rotary knobs which are used for adjusting positions in horizontal and vertical directions and installed on the fixing supports, a cement-based material mold, tested samples of the cement-based materials, laser signal reflection targets embedded in the tested samples of the cement-based materials, a computer, and a controller which is provided with a displacement signal processing module of the samples, a temperature signal processing module of the samples, and a data collection card; in the aspect of software: the computer is installed with measurement and analysis softwares for calculating strain quantity of the related samples based on temperature variation. The invention has the advantages of being high in testing precision, quick in sampling frequency, free from surrounding electromagnetic interference during the testing process, and impervious to material quality and color of the samples.

Description

technical field [0001] It is used to measure the displacement change history of the monitored point during the process of hydration and drying of cement-based cementitious materials. Background technique [0002] The crack resistance and durability of cement-based materials are the current research hotspots in the field of inorganic non-metallic materials. By testing the volume change history of cement-based materials in the process of hydration and drying, it can be used to compare and calculate the volume change and displacement field of cement-based materials during the maturation process, providing a basis for the selection of raw materials, the optimization of the mix ratio, and the internal stress of the structure. The calculation and cracking risk assessment provide scientific basis. [0003] There are two types of test methods for cement-based materials during the hydration and drying process, one is a contact measurement method, and the other is a non-contact measu...

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Problems solved by technology

However, the disadvantage of this method is that the test accuracy is poor, especially the elastic recovery force of the test hardware dial indicator and LVDT during the measurement period, so this method cannot accurately measure the displacement history of cement-based materials in the plastic state before initial setting. The start time of the test can only be after the initial setting of the cement-based material, which affects the scope of use of this method and the authenticity of the measured value

The second non-contact measurement method has the characteristics of unlimited test start time, Wang Peiming (Wang Peiming, Liu Yan, Guo Yanhui, etc. Research on the eddy current method of shrinkage test of concrete in early age, Journal of Building Materials. 2006, 9 (6): 711-715) reported a non-contact test method for testing the early age shrinkage of concrete. The method uses an eddy current displacement sensor with a measurement accuracy of 1um. Although this method achieves non-contact measurement, the used Eddy-current sensors have some disadvantages. First, when using eddy-current sensors, the measured sample can only be metal, and the feedback signals of different metals such as copper, iron, aluminum and lead are not the same. Therefore, When the material of the target to be tested is different, it is necessary to repeatedly calibrate and calibrate the equipment; again, the test accuracy of the eddy current sensor is poor, and its test accuracy is generally at the um level; finally, the eddy current sensor is vulnerable to External electric field, magnetic field interference, so the stability of the test signal is poor

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