CN103454012B - Device for measuring internal temperature of sample in process of low-temperature triaxial mechanical testing - Google Patents

Abstract

The invention discloses a device for measuring the internal temperature of a sample during a low-temperature triaxial mechanical test. The device consists of a high-precision thermistor temperature sensor, an epoxy resin indenter with quick connectors and contacts, an ordinary epoxy resin indenter, an oil-proof latex sleeve, a lock-type three-axis pressure chamber top cover and a data acquisition system. The data acquisition system includes a data acquisition instrument and a computer. When in use, a small pressure-resistant high-precision thermistor temperature sensor is placed inside the sample, and its lead wires are respectively welded to the contacts distributed at the lower end of the epoxy resin pressure head with quick connectors and contacts placed on the top of the sample, with quick connectors The quick interface on the upper end of the epoxy resin pressure head of the contact point is docked with the quick interface on the top cover of the lock-type triaxial pressure chamber, and the lead wire is connected to the data acquisition system from the quick interface on the top cover of the triaxial pressure chamber; through the data The acquisition system can directly store data and observe the change process of the internal temperature of the sample in real time. The invention can directly monitor the dynamic evolution of the internal temperature of the sample during the triaxial mechanical test, thereby providing temperature guarantee for the study of the mechanical properties of frozen soil.

Description

A device for measuring the internal temperature of a sample during a low-temperature triaxial mechanical test

technical field

The invention relates to a device for measuring the internal temperature of a sample during a low-temperature triaxial mechanical test, which is mainly used for direct measurement and monitoring of the internal temperature of a frozen soil sample under the action of triaxial static and dynamic loads.

Background technique

Frozen soil is a four-phase system composed of solid mineral particles, plastic ice, liquid water and gas. It is a kind of soil that is very sensitive to temperature and has unstable properties. Its instability is mainly manifested in the fluctuation of mechanical properties. The research on the mechanical properties of frozen soil is basically carried out around the temperature in the test. On the one hand, other conditions are fixed, and the initial (test) temperature of the sample is changed to explore the law of the change of frozen soil properties with the temperature; on the other hand, the fixed The initial (test) temperature of the sample is used to discuss the influence of the soil quality, dry density, water content, strain rate, load magnitude, and load action time of the sample on the mechanical properties of frozen soil. All these show that the temperature has very important significance to the study of the mechanical properties of frozen soil.

In a large number of studies on the mechanical properties of frozen soil, the temperature involved refers to the initial temperature of the sample or the temperature of the environment where the sample is located. There are also some reports on the test internal temperature test during the uniaxial mechanical test. The temperature measurement The method is that the lead wire of the temperature sensor inserted into the sample directly penetrates the latex sleeve on the surface of the sample to connect with the data acquisition instrument. In the triaxial mechanical test, the sample is placed in hydraulic oil, and a small damage to the latex sleeve will cause the test If the sample is polluted or soaked by oil, obviously the above method is not suitable for the measurement of the internal temperature of the sample in the triaxial mechanical test. Up to now, there is no measuring device or method in this regard. Therefore, it is necessary to develop a measuring device for measuring the internal temperature of the sample during the low-temperature triaxial mechanical test, which can not only regulate the temperature of the hydraulic oil in the triaxial pressure chamber during the mechanical test to ensure the initial temperature or test temperature of the sample, but also directly measure The internal temperature of the sample and its change process with the load can improve the temperature control accuracy in the process of mechanical testing of frozen soil, and provide a theoretical basis for the interpretation of some mechanical phenomena and mechanisms.

Contents of the invention

In view of the above, the object of the present invention is to provide a device for measuring the internal temperature of a sample during a low-temperature triaxial mechanical test. The device can directly measure the internal temperature of the sample and its change process with the load, and can regulate the temperature of the hydraulic oil in the triaxial pressure chamber to ensure the initial temperature or test temperature of the sample.

The purpose of the present invention is achieved like this:

A device for measuring the internal temperature of a sample during a low-temperature triaxial mechanical test, mainly composed of a high-precision thermistor temperature sensor, an epoxy resin indenter with quick connectors and contacts, an ordinary epoxy resin indenter, and a lock The top cover of the lock-type triaxial pressure chamber, the quick interface, the sample and the threaded rod are composed. The sample is put into the pressure tank matching the top cover of the lock-type triaxial pressure chamber. On the tank, the sample is covered with an oil-proof latex sleeve. The epoxy resin indenter with quick connectors and contacts is placed on the top of the sample, and the ordinary epoxy resin indenter is placed at the bottom of the sample. There is a rubber ring embedded in the groove of the epoxy resin indenter and the ordinary epoxy resin indenter, and the leads of the high-precision thermistor temperature sensor inserted into the sample are distributed along the lower end of the sample and the epoxy resin indenter with leads The lead wires are welded, and the welded joints are correspondingly connected with the contacts distributed on the upper end of the epoxy resin indenter with quick connectors and contacts, and the epoxy resin indenter with quick connectors and contacts is connected to the top cover of the locking type triaxial pressure chamber. Quick interface, threaded holes and cold liquid circulation pipes are provided on the top cover of the lock-type triaxial pressure chamber, and the threaded rod is fixedly connected with the corresponding pressure tank through the threaded holes; The lead wire is connected with the data acquisition instrument in the data acquisition system, and the data acquisition instrument is connected with the computer through the data line.

Advantages of the present invention:

1. The present invention connects the high-precision thermistor temperature sensor lead wires placed inside the sample through the contacts on the epoxy resin indenter with quick connectors and contacts, and connects the epoxy resin indenter with quick connectors and contacts and the lock Two quick joints on the top cover of the three-axis pressure chamber, and the sample, high-precision thermistor temperature sensor and the lower part of the epoxy resin indenter with quick joints and contacts are sealed in the oil-proof latex sleeve, and then passed through The fast interface on the top cover of the lock-type triaxial pressure chamber is connected to the data acquisition instrument in the data acquisition system. The data acquisition instrument is connected to the computer through the data line, so that the sample during the triaxial mechanical test can be directly monitored. The dynamic change process of the internal temperature avoids the occurrence of the sample being polluted or soaked by oil, improves the temperature control accuracy in the process of mechanical testing of frozen soil, and provides a basis for the interpretation of some mechanical phenomena and mechanisms.

2. The structure of the locking type triaxial pressure chamber top cover of the present invention is an improvement on the top cover of the test tank in the Chinese patent application of 200410026390.6. The top cover changes the screw structure into a lock structure. The top cover is provided with threaded holes, quick connectors and cooling liquid circulation pipes. The quick interface is convenient for docking with the quick connector on the epoxy resin indenter with quick connector and contacts, and the lead wire can be connected to the data acquisition instrument. The temperature inside the sample can be directly monitored in real time through the computer connected to the data acquisition instrument. Changes. Secondly, the threaded rod is fixed and closely connected with the locking type triaxial pressure chamber top cover 5 and the pressure tank through the threaded hole, which ensures the sealing of the pressure tank.

Description of drawings

Figure 1 is a cross-sectional view of the arrangement of a high-precision thermistor temperature sensor in a sample according to an embodiment of the present invention

Fig. 2 is a three-dimensional schematic diagram of a special epoxy resin indenter according to an embodiment of the present invention.

Fig. 3 is a cross-sectional view of the top cover of the locking type triaxial pressure chamber according to the embodiment of the present invention.

Fig. 4 is a top view of the top cover of the locking type triaxial pressure chamber according to the embodiment of the present invention.

Fig. 5 is a graph showing the variation of oil temperature and the internal temperature of the sample with time during the confining pressure process. In the figure: oil represents the confining pressure oil, and Sample represents the sample.

Figure 6 is a diagram of the change process of the internal temperature of the sample under the action of axial cyclic load when the confining pressure is 8.0MPa. In the figure: -0.2℃, -0.5℃, -1.0℃, -2.0℃ and -4.0℃ are respectively sample initial temperature.

Detailed ways

The high-precision thermistor temperature sensor 1 of the present invention is composed of a thermistor and a needle-shaped pressure-resistant steel sleeve, and its lead wire is a two-wire system; wherein the thermistor performance and the manufacturing technology of the high-precision thermistor temperature sensor 1 It was disclosed in the research article "Technical Improvement and Application Characteristics of High-precision Thermistor Temperature Sensor" in Volume 33, Issue 4 of "Glacier and Frozen Soil" in 2011. The needle-shaped pressure-resistant steel sleeve has a length of 20.0mm and a diameter of 3.0mm. The thermistor is placed 2.0mm from the tip of the needle-shaped pressure-resistant steel sleeve. Its model is: small high-precision thermistor temperature sensor, produced by the State Key Laboratory of Frozen Soil Engineering, Institute of Cold and Arid Region Environment and Engineering, Lanzhou Chinese Academy of Sciences.

Sample 9 of the present invention is silty sandy soil.

Below in conjunction with accompanying drawing, structure and working principle of the present invention will be further described:

See Figures 1, 2, 3 and 4, a device for measuring the internal temperature of a sample during a low-temperature triaxial mechanical test, mainly composed of a high-precision thermistor temperature sensor 1, an epoxy resin press with quick connectors and contacts Head 2, ordinary epoxy resin indenter 3, lock-type three-axis pressure chamber top cover 5, quick interface 7, sample 9 and threaded rod 12. Sample 9 was put into a pressure tank matched with the top cover 5 of the locking type triaxial pressure chamber, and the top cover 5 of the locking type triaxial pressure chamber was covered on the pressure tank. The sample 9 is covered with an oil-proof latex sleeve 4 . The epoxy resin indenter 2 with quick joint and contact is placed on the top of sample 9, and is located under the top cover 5 of the locking type triaxial pressure chamber; the diameter of epoxy resin indenter 2 with quick joint and contact is the same as that of the sample 9 has the same diameter, a height of 30.0mm, and a bearing capacity of 20MPa. Ordinary epoxy resin indenter 3 is placed at the bottom of sample 9, and the groove of epoxy resin indenter 2 with quick connector and contact point and ordinary epoxy resin indenter 3 is embedded with rubber ring 8, which is inserted into sample 9 The lead wires of the two internal high-precision thermistor temperature sensors 1 are welded to the three contacts at the lower end of the epoxy resin pressure head 2 with quick connectors and contacts, and the soldered contacts are connected to the epoxy resin with quick connectors and contacts. The contacts distributed on the upper end of the indenter 2 communicate correspondingly, and connect the epoxy resin indenter 2 with quick joints and contacts with the quick interface 7 on the top cover 5 of the lock-type triaxial pressure chamber. There are 8 threaded holes 13 and 1 set of cold liquid circulation pipes 10 on the top cover 5 of the locking type triaxial pressure chamber, and 8 threaded rods 12 connect the top cover 5 of the locking type triaxial pressure chamber with the pressure tank Fixedly connected; connect the lead wires from the fast interface 7 of the terminal 11 on the top cover of the triaxial pressure chamber 5 to the data acquisition instrument in the data acquisition system 6, and the data acquisition instrument is connected to the computer through a data line.

Before the test, first insert two high-precision thermistor temperature sensors 1 into the sample 9, then wrap the lead wire on the high-precision thermistor temperature sensor 1 along the radial direction of the sample 9, and connect it with the quick connector and the contact The joints distributed at the lower end of the epoxy resin indenter 2 are welded, and the epoxy resin indenter 2 with quick joints and contacts is placed on the top of the sample, and then the oil-proof latex sleeve 4 is placed on the sample 9 from bottom to top Put the ordinary epoxy resin indenter 3 on the bottom of the sample 9, and put the rubber ring 8 tightly on the groove of the epoxy resin indenter 2 and the ordinary epoxy resin indenter 3 with quick joints and contacts Then put the sample 9 into the pressure tank that matches the top cover 5 of the lock-type triaxial pressure chamber, and connect the epoxy resin pressure head 2 with quick joints and contacts with the top cover 5 of the lock-type triaxial pressure chamber Two quick connectors 7 on the top, cover the lock-type triaxial pressure chamber top cover 5 on the pressure tank, and fix the lock-type triaxial pressure chamber top cover 5 and the pressure tank through 8 threaded rods 12, and finally Connect the lead wires from the fast interface 7 of the terminal post 11 on the top cover of the triaxial pressure chamber 5 to the data acquisition instrument in the data acquisition system 6, and the data acquisition instrument is connected to the computer.

Turn on the data acquisition system 6, and after the temperature in the sample 9 has stabilized for 2 hours, perform a three-axis loading test, monitor and download and store data in real time through the computer in the data acquisition system 6 until the end of the test.

Figure 5 and Figure 6 show the changes of oil temperature and internal temperature of silty sand sample during confining pressure and cyclic loading, respectively. The water content of the sample is 15.0%, the dry density is 1.80 g/cm ³ , the confining pressure is 8.0 MPa, the loading frequency is 3.0 Hz, the peak value of the cyclic load is 45% of the static compressive strength of the corresponding sample, and the valley value is 8.03 MPa.

Figure 5 shows that the oil temperature and the internal temperature of the sample increase with the increase of the confining pressure, but the temperature obviously lags behind the peak value of the force, and the time when the internal temperature of the sample reaches the maximum value also lags behind the oil temperature, and when the confining pressure is stable, the oil The internal temperature of the mild sample gradually recovers, and finally fails to reach the initial value, indicating that the confining pressure has changed the initial state of the oil and the sample. The change of oil temperature is mainly caused by the volume compression caused by the effect of confining pressure. On the one hand, the change of sample temperature is caused by the effect of oil temperature, and on the other hand, it is also caused by the effect of confining pressure.

Figure 6 shows that when the confining pressure is kept constant, the internal temperature of the sample increases with the increase of the axial cyclic loading time, and the lower the initial temperature of the sample, the more obvious the internal temperature rises. When the confining pressure is constant, the compressibility of the oil is constant, so the oil temperature remains constant, then the change of the internal temperature of the sample at this time is mainly caused by the work done by the cyclic load on the sample.

According to Figure 5 and Figure 6, when performing low temperature triaxial testing, the measurement of the internal temperature of the sample can not only improve the temperature control accuracy, but also explain some mechanical phenomena and mechanisms.

Claims (1)

1. A device for measuring the internal temperature of a sample during a low-temperature triaxial mechanical test, mainly composed of a high-precision thermistor temperature sensor (1), an epoxy resin indenter with quick joints and contacts (2), an ordinary epoxy Resin indenter (3), lock type triaxial pressure chamber top cover (5), quick connector (7), sample (9) and threaded rod (12), is characterized in that: sample (9) is put into In the pressure tank matched with the lock-type triaxial pressure chamber top cover (5), the lock-type triaxial pressure chamber top cover (5) is covered on the pressure tank, and the sample (9) is covered with an oil-proof latex sleeve ( 4), the epoxy resin indenter (2) with quick connector and contacts is placed on the top of the sample (9), and the ordinary epoxy resin indenter (3) is placed at the bottom of the sample (9), with quick connectors and The rubber ring (8) is embedded in the groove of the epoxy resin indenter (2) of the contact point and the ordinary epoxy resin indenter (3), which is inserted into the high-precision thermistor temperature sensor (1) inside the sample (9) The leads are welded along the joints distributed between the sample (9) and the lower end of the epoxy resin indenter (2) with quick connectors and contacts, and the upper and lower ends of the epoxy resin indenter (2) with quick connectors and contacts are distributed The contacts of the corresponding connection are connected, and the epoxy resin indenter (2) with quick joints and contacts is connected with the quick joint (7) on the top cover (5) of the lock-type triaxial pressure chamber, and the top cover of the lock-type triaxial pressure chamber (5) is provided with a threaded hole (13) and a cold liquid circulation pipe (10), and the threaded rod (12) is fixedly connected with the corresponding pressure tank through the threaded hole (13); from the top cover of the lock type triaxial pressure chamber ( 5) The fast interface (7) of the upper terminal (11) is connected with the data acquisition instrument in the data acquisition system (6), and the data acquisition instrument is connected with the computer through the data line.