CN219455025U - Measuring device for crack width change of underground masonry cultural relics - Google Patents

Abstract

The utility model discloses a measuring device for crack width variation of underground masonry cultural relic structures, which comprises a helical compression spring, a plastic gasket and a film flexible piezoresistive pressure sensor, and the first surfaces of the two plastic gaskets are respectively fixed on The two ends of the helical compression spring and the second surfaces of the two plastic gaskets are respectively fixed on the pressure-sensing surfaces of the two thin-film flexible piezoresistive pressure sensors. The measuring device of the utility model uses a thin-film flexible piezoresistive pressure sensor to convert the pressure signal into an electrical signal output, and then obtains the pressure of the spring through a detection instrument, and directly calculates the length change of the spring through Hooke's law, and then obtains the underground masonry The change of crack width of similar cultural relic structure greatly improves the measurement accuracy of crack width change, which can be used for long-term monitoring of cultural relics.

Description

A measuring device for crack width variation of underground masonry cultural relics structure

technical field

The utility model relates to a crack measurement technology for cultural relics, in particular to a measuring device for crack width variation of underground masonry cultural relics structures.

Background technique

Most of the underground cultural relic structures are masonry structures. Due to hundreds of thousands of years of weathering, the structure and material properties of the cultural relics have been greatly deteriorated, and the environment where the underground cultural relics are located is high in humidity, constant temperature and rich in water, making the cultural relics body Numerous cracks develop which develop slowly and continuously over time. The width of cracks in underground cultural relic structures is generally about 10 mm, and changes slowly. Such small-scale cracks bring many difficulties to the design and selection of measuring devices. How to reasonably monitor the crack changes of underground masonry structures and provide data support for the subsequent protection of cultural relics is the most important thing in the protection of underground masonry cultural relics.

Due to the characteristics of cultural relics protection, conventional crack observation techniques need to fix scales or paste markers on cultural relics, but this method will be greatly limited due to the characteristics of cultural relics themselves, resulting in low accuracy and poor sustainability. The current detection methods for structural cracks in underground cultural relics mainly include manual inspection and non-destructive testing. Among them, the manual inspection method is highly dependent on labor and tools, and requires experienced surveyors to detect and record the location and width of cultural relic cracks. Different levels lead to lower detection accuracy and lower efficiency. Non-destructive testing is to use a camera to take pictures of cultural relics for image recognition, but this method is greatly affected by the accuracy of the camera and the testing environment. Therefore, in view of the low visibility in the underground space, conventional measurement methods are difficult to measure accurately, and it is difficult to achieve long-term monitoring. It is necessary to design a portable, high-precision, light disturbance, and long-term measurement of underground masonry cultural relics structures Measuring device for crack width variation.

Utility model content

Purpose of the utility model: In view of the above problems, the purpose of the utility model is to provide a measuring device for crack width variation of underground masonry cultural relics structures.

Technical solution: The utility model is a measuring device for crack width change of underground masonry cultural relics structure, which includes a helical compression spring, a plastic gasket and a film flexible piezoresistive pressure sensor. The first surfaces of the two plastic gaskets are respectively It is fixed on both ends of the helical compression spring, and the second surfaces of the two plastic gaskets are respectively fixed on the pressure-sensing surfaces of the two thin-film flexible piezoresistive pressure sensors.

Further, the diameter of the thin-film flexible piezoresistive pressure sensor is larger than the diameter of the plastic gasket, and the diameter of the plastic gasket is larger than the outer diameter of the helical compression spring.

Further, the helical compression spring is a cylindrical compression spring with a metal circular cross-section, and the two end surfaces of the helical compression spring are tightened and ground flat.

Further, the surface of the plastic spacer is circular.

Further, the surface of the thin-film flexible piezoresistive pressure sensor is circular.

Beneficial effect: compared with the prior art, the utility model has the remarkable advantages of:

1. The measuring device of the present utility model uses a thin-film flexible piezoresistive pressure sensor to convert the pressure signal into an electrical signal output. The pressure of the spring is measured by the detection instrument, and the length change of the spring is calculated by Hooke's law, and then the underground brick is obtained. The change of the crack width of the stone cultural relic structure greatly improves the measurement accuracy of the crack width change, and can be used for long-term monitoring of cultural relics;

2. The measuring device of the present invention is equipped with pressure sensors at both ends of the device, which can check the data results mutually; the average value of the pressure measured by the two pressure sensors is taken as the spring pressure value, which further improves the accuracy of the measurement results; at the same time It also improves the redundancy to prevent the failure of one side of the measuring device;

3. The measuring device of the present invention contacts the plastic gasket through the flattened spring end face, which expands the force-bearing area and reduces the pressure; the film flexible piezoresistive pressure sensor on the circular surface contacts the crack surface of the cultural relics, Enlarging the contact surface and providing flexible contact, greatly reducing the disturbance and damage to the crack structure during the use of the measuring device;

4. The measuring device of the present utility model is small in size and light in weight, and its length can be freely compressed according to cracks of different sizes, and it is easy to place and can be self-fixed in the cracks of cultural relics. good measurement results;

5. The components of the measurement device of the present invention are all finished in the inner chamber, and are not affected by human error during measurement, which can improve work efficiency, reduce labor costs, and improve measurement accuracy.

Description of drawings

Fig. 1 is the structural representation of the utility model;

Fig. 2 is a schematic diagram of a section at the end of a helical compression spring;

Fig. 3 is the implementation schematic diagram of the utility model when measuring the cultural relic crack;

Detailed ways

In order to make the purpose, technical solution and advantages of the present application clearer, the present application will be further described in detail below in conjunction with the accompanying drawings and embodiments.

Figure 1-2 is a schematic structural diagram of a measuring device for the crack width change of underground masonry cultural relics described in this embodiment. The measuring device includes a helical compression spring 1, a plastic gasket 2 and a film flexible piezoresistive Pressure sensor 3, wherein the number of plastic gaskets 2 is 2, the number of film flexible piezoresistive pressure sensors 3 is 2, the helical compression spring 1 includes two end faces, and the first surfaces of the two plastic gaskets 2 are respectively fixed On both ends of the helical compression spring 1 , the second surface of the plastic gasket 2 is fixed on the pressure-sensitive surface of the thin-film flexible piezoresistive pressure sensor 3 .

Optionally, in the above measuring device, the first surface of the plastic gasket 2 can be fixed on the end surface of the helical compression spring 1 by pasting, and the pasting material can be epoxy resin 5 . The second surface of the plastic gasket 2 can also be pasted and fixed on the pressure-sensitive surface of the thin-film flexible piezoresistive pressure sensor 3 by epoxy resin.

Further, the diameter of the thin-film flexible piezoresistive pressure sensor 3 is larger than the diameter of the plastic gasket 2, and the diameter of the plastic gasket 2 is larger than the outer diameter of the helical compression spring 1. While ensuring the aesthetics, the connection between the plastic gasket 2 and the helical spring is increased. The contact area between the springs 1 is compressed, the pressure is reduced, and the disturbance to the crack contact surface is reduced.

As shown in Figure 2, the helical compression spring 1 is a cylindrical compression spring with a metal circular cross-section. The two end faces of the helical compression spring 1 are tightened and ground flat to ensure the verticality of the helical compression spring 1 when it works, and Keep the support ring of the helical compression spring 1 in contact with the plastic gasket 2, change the line contact to surface contact, increase stability and stress area, and avoid scratches on the contact surface.

In an example, the free length of the above-mentioned helical compression spring can be selected as 10-14mm, which satisfies the characteristic that the crack width of underground masonry cultural relics is about 10mm; the stiffness of the helical compression spring is 0.2-0.25N/mm, and the ultimate load is 1.4 -1.5N, the pressure generated by the helical compression spring within the range of variation during operation will hardly disturb the crack contact surface. During the use of the measuring device, the helical compression spring is always in a compressed state to ensure the normal operation and stability of the measuring device. During the use of the measuring device in this embodiment, the variation amplitude of the helical compression spring is 20-40%, which is in line with the estimated degree of crack development in masonry cultural relics.

The surface of the thin-film flexible piezoresistive pressure sensor 3 is circular, and the pressure-sensing surfaces of the two thin-film flexible piezoresistive pressure sensors 3 are respectively in contact with the plastic gasket 2 to receive the spiral compression transmitted from the plastic gasket 2. The pressure of the spring 1, and convert the pressure signal into an electrical signal output, receive and display the pressure through the monitoring instrument; the non-pressure-sensitive surfaces of the two thin-film flexible piezoresistive pressure sensors 3 are respectively in contact with the two surfaces of the cultural relics crack, through Flexible contact avoids damage to the surface of cultural relics.

In an example, the thickness of the above-mentioned thin-film flexible piezoresistive pressure sensor can be selected from 1.5-2.5mm, which reduces the length of the entire measuring device and meets the characteristics of the small crack width of underground masonry cultural relics. The range of 0-4kPa _is selected , sensitivity In line with the cultural relics, cracks bring pressure changes during the expansion process, while ensuring the highest sensitivity and improving the accuracy of measurement.

The surface of the plastic gasket 2 is round and made of insulating material, which further reduces the possibility of conduction between the helical compression spring 1 and the thin-film flexible piezoresistive pressure sensor 3 . Usually, the thickness of the plastic gasket 2 is selected to be 1-1.5mm, which reduces the length of the entire measuring device and satisfies the characteristics of the small crack width of the underground masonry cultural relics structure.

Using the measuring device in this embodiment to measure the crack width variation of the underground masonry cultural relic structure, specifically includes the following process:

First determine the location of the cracks in the masonry cultural relics that need to be monitored, including dangerous cracks and cracks in important parts of the structure. As shown in Figure 3, at least three installation points are determined at the cracks in the cultural relics for placing the measuring device of this embodiment (this implementation three installation points in the example), and the distance between the measuring devices is preferably 10cm; The measuring device is inserted into the crack, and the helical compression spring 1 is always in a compressed state, and the measuring device is self-fixed in the crack of the cultural relic by the compression force of the helical compression spring 1; The length will elongate along with the crack, so that the elastic force changes, acts on the plastic gasket 2 and transmits to the thin-film flexible piezoresistive pressure sensor 3, so that the pressure it receives changes, and the thin-film flexible piezoresistive pressure sensor 3 The output electrical signal changes and is received by the detection instrument, showing the change of pressure.

Under normal working conditions, take the average value of the pressure changes measured by the two thin-film flexible piezoresistive pressure sensors on both sides of the measuring device as the final pressure change value, and then according to Hooke's law, the spring length change formula is Δl =ΔF/k, where ΔF is the pressure change value, k is the spring stiffness, and the elongation value of the spring can be directly calculated according to the pressure change value, that is, the change value of the crack width of the cultural relic structure.

In this embodiment, the measurement device consisting of a helical compression spring, a plastic gasket and a flexible piezoresistive pressure sensor is used to measure the change in the crack width of the underground masonry cultural relic structure, and the measurement device is installed in the crack of the cultural relic, and then The development of cracks in cultural relics is converted into the length change of the helical compression spring, and the change in the elastic force of the helical compression spring caused by the length change is converted into an electrical signal output through a thin-film flexible piezoresistive pressure sensor, which is reversed after analysis Obtain the elastic force change of the helical compression spring, and use Hooke's law to calculate the change value of the crack width of the cultural relic. During the use of the measuring device, since the helical compression spring is tightened and the end surface is ground flat, the verticality of the helical compression spring is guaranteed, the stability of the device is improved, the force-bearing area is increased, and the force-bearing area is reduced. The pressure received by the crack contact surface and the thin-film flexible piezoresistive pressure sensor is reduced, and the disturbance to the crack surface of cultural relics is reduced; the selection of the thin-film flexible piezoresistive pressure sensor reduces the overall length of the device, making it have the characteristics of small crack width The feasibility of monitoring cracks in underground masonry cultural relic structures is greatly improved, and the high sensitivity of the thin-film flexible piezoresistive pressure sensor improves the accuracy of measurement.

Claims (5)

1. The measuring device for the width change of the crack of the underground masonry type cultural relics is characterized by comprising a spiral compression spring, plastic gaskets and a thin film flexible piezoresistive pressure sensor, wherein first surfaces of the two plastic gaskets are respectively fixed on two end surfaces of the spiral compression spring, and second surfaces of the two plastic gaskets are respectively fixed on pressure sensing surfaces of the two thin film flexible piezoresistive pressure sensors.

2. The measurement device of claim 1, wherein the diameter of the thin film flexible piezoresistive pressure sensor is greater than the diameter of the plastic spacer, which is greater than the outer diameter of the helical compression spring.

3. A measuring device according to claim 1 or 2, characterized in that the helical compression spring is a cylindrical compression spring, the cross section of which is a metal circular cross section, the two end faces of the helical compression spring being juxtaposed and ground flat.

4. A measuring device according to claim 1 or 2, characterized in that the surface of the plastic spacer is circular.

5. A measuring device according to claim 1 or 2, characterized in that the surface of the thin film flexible piezoresistive pressure sensor is circular.