CN103091176B - Testing device for testing mechanical property of steel bar under ultralow temperature environment - Google Patents

Abstract

The invention relates to a device for testing the mechanical properties of steel bars in an ultra-low temperature environment. The test device includes a universal tensile testing machine, a suspended rail trolley, an ultra-low temperature test chamber, a liquid nitrogen tank, an electric control box and external measuring equipment; the suspended rail trolley is suspended on the upper end of the universal tensile testing machine, and the ultra-low temperature test chamber is placed on the suspended rail trolley Above, the liquid nitrogen tank is connected to the controller on the ultra-low temperature test box through the liquid nitrogen tube, the electric control box is connected to the controller on the ultra-low temperature test box through the electric control line, and the external measuring equipment is connected to the external terminal on the ultra-low temperature test box through the connecting line Connect to read the data measured by the internal measuring equipment. In the present invention, the test box and the suspended track trolley are independent of each other so that the follow-up test can be quickly positioned and the operation cycle is reduced; the sealing plugs at both ends of the test box are fixed by combining front resistance and rear pulling to avoid excessive damage to the steel bars due to excessive displacement of the sealing plugs The extrusion force affects the experimental results; the upper cover of the test box and the lower part of the box are further sealed by a tongue and groove connection.

Description

Experimental device for testing the mechanical properties of steel bars in ultra-low temperature environments

technical field

The invention belongs to the field of material testing, and in particular relates to a test device for the mechanical properties of steel bars in an ultra-low temperature environment, in particular to a device for static tensile tests of steel bars at ultra-low temperatures, tensile performance tests of steel bar joints at ultra-low temperatures, and The test device for the stress loss test caused by the stress relaxation of prestressed steel bars. the

Background technique

Ultra-low temperature storage tanks (such as liquefied natural gas storage tanks) are special structures that my country has begun to build in recent years. The outer tank wall of the storage tank generally adopts prestressed concrete structure, and the storage temperature of liquefied natural gas is about -165°C. Properties also change, which in turn affects the overall performance of reinforced concrete. the

At present, the design of large ultra-low temperature storage tanks is only in the hands of a few countries such as the United Kingdom, the United States, and Japan. my country is still in the initial and exploratory stage. The relevant standards and specifications have not kept up with the pace of construction. It needs to digest and absorb foreign advanced technical specifications and domestic development and construction. On the basis of practice and research, gradually establish and improve a set of relevant norms and standards of our country. the

In China, there are few studies on the performance of ultra-low temperature (below -100°C) steel bars. Wang Yuanqing of Tsinghua University et al. studied BCT3c∏ (equivalent to my country's Q235) and O9Γ2C (equivalent to my country’s Q345) and heat-quenched and tempered steel BCT3c∏-T2 have done a series of tests. Tongji University and Tianjin University have done static tensile tests on steel bars at ultra-low temperatures, but limited to test conditions, there are errors in the tests and the conclusions are not complete. Therefore, a large number of tests are still needed to perfect the relevant norms and standards in this field in our country, and the tests are required to be more accurate. the

For the performance of steel bars at ultra-low temperature, foreign experimental research has a certain foundation, which is of reference significance for us, but the foreign experimental results cannot be directly applied in our country. Therefore, the performance of steel bars in ultra-low temperature environments needs to be further studied in order to establish a relatively complete set of independent standard systems in my country. the

Domestically, no relevant research has been done on the stress loss test of prestressed steel bars at ultra-low temperatures, and the stress loss of prestressed steel bars at ultra-low temperatures is crucial to the design of ultra-low temperature storage tanks. the

Contents of the invention

In order to overcome the shortage of existing equipment, the present invention provides a machine that is easy to operate and can accurately and quickly complete the static tensile test of steel bars at ultra-low temperatures, the tensile performance test of steel bar joints at ultra-low temperatures, and the stress relaxation of prestressed steel bars at ultra-low temperatures. Test setup for stress loss tests. the

To achieve the above object, the present invention adopts the following scheme:

The test device for testing the mechanical properties of steel bars in an ultra-low temperature environment includes a universal tensile testing machine, a suspended rail trolley, an ultra-low temperature test chamber, a liquid nitrogen tank, an electric control box, and external measuring equipment; The test chamber is placed on the suspended track trolley, the liquid nitrogen tank is connected to the controller on the ultra-low temperature test chamber through the liquid nitrogen tube, the electric control box is connected to the controller on the ultra-low temperature test chamber through the electric control line, and the external measuring equipment is connected through the connection line It is connected to the external terminal on the ultra-low temperature test chamber to read the data measured by the internal measuring equipment. the

Preferably, the above-mentioned suspension track type trolley includes a trolley and two suspension tracks, and the two suspension tracks are parallel; each suspension track includes a crossbeam, an anchorage, a telescopic suspension rod, a longitudinal diagonal stay, a transverse stay and a track; the crossbeam The anchors at both ends are fixed on the upper end of the universal tensile testing machine, and the anchoring device and the beam are anchored to form a whole through the connecting bolts, and the fixing bolts on the anchoring gear further fix the formed whole with the upper end of the universal tensile testing machine. the

Preferably, telescopic suspension rods are suspended at both ends of the crossbeam, and the crossbeam and the telescopic suspension rods can be fixed with bolts; and longitudinal diagonal stay rods to enhance the structural integrity, and the horizontal diagonal stay rods, longitudinal diagonal stay rods and telescopic suspension rods are fixed with bolts. the

Preferably, the telescopic suspension rod is formed by nesting two steel pipes with different diameters. The small-diameter steel pipe extends into the large-diameter steel pipe, and the wall of the large-diameter steel pipe is embedded with fastening bolts. When the small-diameter steel pipe is inserted into the large-diameter steel pipe When the expansion and contraction reaches the required height, the fastening bolts are tightened to extrude the small-diameter steel pipe. the

Preferably, the trolley comprises a trolley floor, four wheels and four rigid bars, two wheels are arranged in each track, and each wheel is connected with four corners of the trolley floor by a rigid bar, and the wheels can freely enter and exit the track and Sliding in the track, the rigid rod and the bottom plate of the trolley are fixed by bolts. The bottom plate of the trolley has certain rigidity and strength and holes are left in the middle. the

Preferably, the bottom plate of the trolley is made of steel plate or plywood. the

Preferably, the ultra-low temperature test chamber has a cylindrical structure, and four 360-degree rotating wheels are symmetrically arranged at the bottom of the chamber. The wall of the ultra-low temperature test chamber is divided into an inner protective layer, an insulating layer, and an outer protective layer from inside to outside. The inner protection layer can be made of aluminum alloy or ultra-low temperature 06Ni9 steel, the insulation layer can be made of polyurethane board, and the outer protection layer can be made of ordinary steel plate; It adopts tongue-and-groove connection, and is equipped with an upper sealing gasket and a lower sealing gasket. The upper sealing gasket and the lower sealing gasket are made of trifluoro pad material; the sealing switch of the upper cover can be connected by ordinary bolts or powerful electromagnet switches. The upper and lower parts are respectively equipped with handles to facilitate the taking and placing of the box; the ultra-low temperature test box has a fixed wiring across the wall, and the fixed wiring has an internal terminal and an external terminal. The measuring equipment is connected to the external measuring equipment, the internal measuring equipment is ultra-low temperature strain gauge, ultra-low temperature sensor, etc., and the external measuring equipment is the display device of each parameter; the lower part of the ultra-low temperature test chamber is equipped with a controller, which is used to adjust the liquid nitrogen per unit time The evaporation amount is used to control the temperature inside the box. The controller is connected to the electric control box and the liquid nitrogen tank respectively through the electric control line and the liquid nitrogen tube, thereby forming an automatic temperature adjustment mechanism. the

Preferably, the upper and lower ends of the box body are symmetrically provided with openings, the openings at both ends are tapered with a large inside and small outside, and sealing plugs are provided at the openings at both ends. On the outer end face of the tapered hole, there is a hoop formed by shrinking the outer protective layer into the hole, and the hoop is used to limit the displacement of the sealing plug; a box protrusion is formed outside the inner end face of the tapered hole, and the box protrusion is also As for the structure of the box, the outer surface of the raised box is threaded, and the raised bottom of the box is provided with a ring-shaped protrusion; the sealing plug is tapered and the end of the big head forms a nail cap, and the sealing plug is made of trifluoro pad material. The sealing plug is fixed on the protrusion of the box body through a bowl-shaped nut. the

Preferably, the bowl-shaped nut is made of ultra-low temperature 06Ni9 steel, wherein the inner surface of the bowl-shaped nut is threaded so as to be threadedly connected with the casing protrusion; the inner bottom surface of the bowl-shaped nut is provided with an annular protrusion ; The end face of the bowl-shaped nut is provided with a hole for the bowl-shaped nut. the

Compared with the prior art, the present invention has the following advantages:

(1), the ultra-low temperature test chamber and the suspended track type trolley of the present invention are mutually independent devices, and the top of the rigid suspension rod supporting the trolley track is provided with a temporary anchoring device, which can temporarily fix the track on the tensile testing machine, and the ultra-low temperature test chamber Place it on the bottom of the trolley. Temporarily fix the track and perform lateral positioning for quick positioning in subsequent tests, reducing the experimental operation cycle. the

(2) The material of the sealing plug of this experimental device is a high-quality ultra-low temperature resistant trifluoro mat material, which can be used as a sealing material in an ultra-low temperature state, and the applicable temperature is -200°C to 150°C. the

(3) The sealing plugs at both ends of the ultra-low temperature test chamber are fixed by a combination of front resistance and rear pulling, that is, the blocking of the hoop and the extrusion of the bowl-shaped nut, so as to avoid excessive damage to the steel bars due to excessive displacement of the sealing plugs Extrusion force will affect the accuracy of the experimental results. the

(4) The connection between the upper cover of the ultra-low temperature test box and the lower part of the box body adopts tongue-and-groove connection, and there is an ultra-low temperature gasket made of high-quality ultra-low temperature resistant trifluoro mat to further seal. the

(5) The wall of the ultra-low temperature test box is embedded with fixed wiring, and there are wiring joints at both ends to connect the measuring devices and instruments inside and outside the box. the

Description of drawings

Fig. 1 is the schematic diagram of front view of ultra-low temperature test device of the present invention;

Fig. 2 is the side view schematic diagram of ultra-low temperature test device of the present invention;

Figure 3 is a schematic diagram of the main view of the suspension track type trolley;

Figure 4 is a side view schematic diagram of the suspension track type trolley;

Fig. 5 is the schematic diagram of the front view of the anchor for fixing the suspended track type trolley;

Fig. 6 is a schematic side view of the anchorage for fixing the suspended track-type trolley;

Fig. 7 is the schematic sectional view of the track when the suspension track type dolly has wheels;

Figure 8 is a three-dimensional schematic diagram of the track when the suspension track type dolly has no wheels;

Figure 9 is a schematic diagram of the structure of the ultra-low temperature test chamber;

Figure 10 is a schematic diagram of the structure of the sealing plug of the ultra-low temperature test chamber;

Fig. 11 is a schematic diagram of the structure of the bowl-shaped nut for fixing the sealing plug at the end. the

In the figure: 1. Universal tensile testing machine; 2. Suspension track trolley; 3. Ultra-low temperature test chamber; 4. Liquid nitrogen tank; 5. Electric control box; 6. External measuring equipment; 7. Cart; 8. Suspension track; 9. Liquid nitrogen pipe; 10. Electric control line; 11. Supporting suspension track beam; 12. Anchor; 13. Large-diameter steel pipe; 14. Telescopic suspension rod; 15. Fastening bolts; 16. Small-diameter steel pipe ; 17, longitudinal slanting rod; 18, track; 19, trolley wheel; 20, rigid bar for selecting the bottom plate of trolley; 21, trolley bottom plate; , 22 transverse slanting rod; 23, connecting bolt; , sealing plug; 26, bowl nut; 27, upper sealing gasket; 28, lower sealing gasket; 29, upper cover sealing switch; 30, inner protective layer; 31, insulation board; 32, outer protective layer; 33 , Across wiring; 34, External terminal; 35, Internal terminal; 36, Test piece; 37, Upper cover handle; 38, Box lower handle; 39, Controller; 40, 360-degree rotating wheel; 41, Internal measurement Equipment; 42. Ultra-low temperature studio; 43. The thread connection between the box body protrusion and the bowl-shaped nut; 44. The box body protrusion; 45. Hoop; 46. The thread treatment of the inner wall of the bowl-shaped nut; An annular protrusion at the bottom of the cap; 48, a hole for the bowl-shaped nut; 49, an annular protrusion. the

Detailed ways

As shown in Figure 1-2, the test device for testing the mechanical properties of steel bars in an ultra-low temperature environment includes a universal tensile testing machine 1, a suspended track trolley 2, an ultra-low temperature test chamber 3, a liquid nitrogen tank 4, an electric control box 5 and external measuring equipment 6 ; Suspension rail trolley 2 is suspended on the upper end of universal tensile testing machine 1, ultra-low temperature test chamber 3 is placed on suspension rail type trolley 2 to facilitate entry and exit of universal tensile testing machine 1, liquid nitrogen tank 4 passes liquid nitrogen tube 9 and ultra-low temperature test chamber 3 The controller 39 on the ultra-low temperature test box 3 is connected to each other, the electric control box 5 is connected to the controller 39 on the ultra-low temperature test box 3 through the electric control line 10, and the external measuring device 6 is connected to the external terminal 34 on the ultra-low temperature test box 3 through a connecting line to read the internal The data measured by the measuring equipment 41; the universal tensile testing machine 1 is used to load the test piece, the suspended track trolley 2 is used to support the ultra-low temperature test chamber 3, and the ultra-low temperature test chamber 3 is used to provide the ultra-low temperature environment required for the experiment, liquid nitrogen The tank 4 is used to hold the refrigerant liquid nitrogen, the electric control box 5 is used to intelligently control the temperature in the ultra-low temperature test chamber 3, and the external measuring device 6 is used to read the experimental data. the

As shown in Figures 1-8, the suspension track type trolley 2 includes a trolley 7 and two suspension rails 8; the two suspension rails are parallel. Every suspension track 8 comprises crossbeam 11, anchorage 12, telescopic suspension rod 14, longitudinal diagonal stay rod 17, transverse stay rod 22 and track 18; Crossbeam 11 is fixed on universal tensile testing machine 1 by anchorage 12 at two ends At the upper end, the anchorage 12 and the crossbeam 11 are anchored tightly by the connecting bolts 23 to form a whole, and the fixing bolts 24 on the anchorage 12 further fix the formed whole with the upper end of the universal tensile testing machine, so as to achieve the purpose of fixing the crossbeam. the

The two ends of the crossbeam 11 are respectively suspended with telescopic suspension rods 14, and the crossbeam 11 and the telescopic suspension rods 14 can be fixed by bolt connection. The four telescopic suspension rods 14 are respectively provided with intersecting transverse stay rods 22 and longitudinal stay rods 17 in two directions to enhance structural integrity. Fastened with bolts. the

The retractable suspension rod 14 is formed by the nesting of two steel pipes with different diameters. The small-diameter steel pipe 16 stretches into the large-diameter steel pipe 13, and the wall of the large-diameter steel pipe 13 is embedded with fastening bolts 15. When expansion and contraction in the diameter steel pipe 13 reaches the required height, fastening bolt 15 is tightened to extrude the small diameter steel pipe to fix the length of telescopic suspension rod 14. the

Dolly 7 comprises four wheels 19, four rigid bars 20 and dolly floor 21, two wheels 19 are arranged in every track 18, and each wheel 19 is connected with four corners of dolly floor by a rigid bar 20, and wheel 19 can freely enter and exit the track 18 and slide in the track 18, and the rigid rod 20 and the trolley floor 21 are fixed by bolts. The dolly base plate 21 has certain rigidity and strength and leaves a hole in the middle, and the dolly base plate 21 can select steel plate or plywood for use. the

As shown in Figures 1-3 and 9, the ultra-low temperature test chamber 3 has a cylindrical structure, and four 360-degree rotating wheels 40 are symmetrically arranged at the bottom of the chamber to facilitate the parallel movement of the chamber. The wall of the ultra-low temperature test chamber 3 is divided into an inner protective layer 30, an insulating layer 31, and an outer protective layer 32 from the inside to the outside. The inner protective layer 30 can be made of aluminum alloy or ultra-low temperature 06Ni9 steel, and the insulating layer 31 can be made of polyurethane board. , The outer protective layer 32 can be made of ordinary steel plate. The box is divided into two parts, the upper cover and the lower part of the box. The upper cover and the lower part of the box are connected by tongue and groove, and an upper sealing gasket 27 and a lower sealing gasket 28 are provided to achieve effective sealing. The upper sealing gasket 27 and the lower sealing gasket The sealing gasket 28 is made of trifluoro pad material. The loam cake seal switch 29 can select common bolt connection, powerful electromagnet switch connection, and the upper and lower two parts are respectively provided with handle 37 and handle 38 to facilitate the casing to pick and place. The box wall of the ultra-low temperature test chamber 3 is straddled by a fixed connection 33, and the fixed connection 33 has an internal terminal 35 and an external terminal 34, and the internal terminal 35 and the external terminal 34 are respectively connected to the internal measuring equipment 41 and the external measuring equipment through connecting wires. 6 are connected, the internal measuring device 41 is an ultra-low temperature strain gauge, an ultra-low temperature sensor, etc., and the external measuring device 6 is a display device for each parameter. The internal measuring device 41 and the external measuring device 6 all belong to existing equipment in the field. The lower part of the ultra-low temperature test chamber 3 is provided with a controller 39. The controller 39 is used to adjust the evaporation rate of liquid nitrogen per unit time to control the temperature inside the chamber. Box 5 is connected with liquid nitrogen tank 4, and then forms the automatic regulation mechanism of temperature, and controller 39 and electric control box 5 all belong to existing equipment. the

As shown in Fig. 9-11, the upper and lower ends of the box body are symmetrically provided with openings, the openings at both ends are tapered with a large inside and small outside, and sealing plugs 25 are provided at the openings at both ends. On the outer end surface of the tapered hole, there is a hoop 45 formed by shrinking the outer protective layer 32 into the hole. The hoop 45 is used to limit the displacement of the sealing plug 25; The body protrusion 44 is also the structural part of the box body, the outer surface 43 of the box body protrusion 44 is threaded, and the bottom surface of the box body protrusion 44 is provided with an annular protrusion 49 . The sealing plug 25 is tapered and has a large head end forming a nail cap. The sealing plug 25 is made of trifluoro pad material. The sealing plug 25 is fixed on the casing protrusion 44 through a bowl-shaped nut 26 . The bowl-shaped nut 26 is made of ultra-low temperature 06Ni9 steel, which can meet the performance requirements at ultra-low temperature, and the inner surface 46 of the bowl-shaped nut 26 is made into a threaded thread so as to be connected with the casing protrusion 44 through the thread 43; The inner bottom surface of the nut 26 is provided with an annular protrusion 47, the purpose of which is to strengthen the extrusion force on the sealing plug 25 corresponding to the annular protrusion 49, and to pull the sealing plug 25 when the sealing plug 25 moves outwards too much. riveting function; the bowl-shaped nut 26 end face is provided with a bowl-shaped nut retaining hole 48 . the

The experimental operation process is as follows:

During the test, the track 18 is suspended and temporarily fixed on the upper end of the universal tensile testing machine, and the lateral positioning is done, and then the dolly is suspended on the track 18. By adjusting the telescopic rod 14, the track and the bottom plate of the trolley are as horizontal as possible, and the upper clear height is reserved by referring to the height of the known ultra-low temperature test chamber, so as to meet the requirement that the upper clamp just clamps the steel bar. Place the ultra-low temperature test chamber on the bottom plate 21 of the trolley, and connect the liquid nitrogen input device, the external measuring device 6, the electric control box 5, and the like. Open the ultra-low temperature test chamber 3 and place the sealing plug 25, then fix and compress the sealing plug 25 with a bowl-shaped nut 26, bond the test piece 36 to internal measuring equipment 41 such as strain gauges, and put the test piece 36 into the ultra-low temperature test chamber 3 And connect the terminal of the internal measurement equipment 41 with the fixed internal terminal 35, cover the ultra-low temperature test box, and use the switch 29 to anchor and seal the upper cover and the lower part of the box body. the

Push the trolley along the track 18 into the universal tensile testing machine. At this time, the space reserved after the horizontal positioning of the previous track and the height calculation makes the upper clamp just enough to clamp the steel bar, and then move the lower clamp upward to reach the height that can clamp the steel bar. . Set the temperature required for the experiment through the electric control box 5, check each instrument, start liquid nitrogen transportation to cool down, and after reaching the required test temperature, clamp the steel bars at both ends to stretch, and pay attention to the readings of the external instruments during the stretching process. Record the experimental data. the

After the stretching of a test piece is finished, stop the liquid nitrogen circulation and release the clamping end, pull the trolley out along the track 18, open the ultra-low temperature test chamber 3 to replace the test piece 36, and repeat the appeal process to complete the tensile test of each test piece. the

Claims (10)

1. steel bar mechanics performance tester for testing under ultra-low temperature surroundings, comprises universal tensile testing machine, suspended rail formula dolly, cryogenic testing case, liquid nitrogen container, electric cabinet and external measurement devices; It is characterized in that: suspended rail formula dolly hangs on universal tensile testing machine upper end, cryogenic testing case is positioned on suspended rail formula dolly, liquid nitrogen container is connected with the controller on cryogenic testing case by liquid nitrogen pipe, electric cabinet is connected with the controller on cryogenic testing case by electrical control lines, and external measurement devices to be connected with the external the end of a thread on cryogenic testing case by connecting line and then to read the data that internal measurement equipment records.

2. steel bar mechanics performance tester for testing under ultra-low temperature surroundings according to claim 1, is characterized in that: above-mentioned suspended rail formula dolly comprises dolly and two suspended rails, and two suspended rails are parallel; Every bar suspended rail comprises crossbeam, ground tackle, extension type suspending rod, longitudinal brace, horizontal brace and track; Crossbeam is fixed on universal tensile testing machine upper end by the ground tackle at two ends, by coupling bolt, ground tackle and crossbeam anchoring is tightly formed an entirety, the set bolt on ground tackle and then the entirety of formation and universal tensile testing machine upper end are fixed.

3. steel bar mechanics performance tester for testing under ultra-low temperature surroundings according to claim 2, is characterized in that: crossbeam two ends are hung with extension type suspending rod respectively, crossbeam and extension type suspending rod are fixed with bolts; Four extension type suspending rod are respectively equipped with in the two directions intersects horizontal brace and longitudinal brace to strengthen structural integrity, and horizontal brace and longitudinal brace and extension type suspending rod are fixed with bolts.

4. steel bar mechanics performance tester for testing under ultra-low temperature surroundings according to claim 3, it is characterized in that: extension type suspending rod is formed by the steel pipe that two diameters are different is nested, minor-diameter steel-tube stretches in large diameter steel pipe, Large-diameter Steel tube wall is embedded with fastening bolt, when fastening bolt is tightened extruding minor-diameter steel-tube by minor-diameter steel-tube when Large-diameter Steel inner telescoping tube reaches desired height.

5. steel bar mechanics performance tester for testing under ultra-low temperature surroundings according to claim 4, it is characterized in that: dolly comprises cart base plate, four wheels and four rigid bars, two wheels are had in every bar track, each wheel is connected with four angles of cart base plate by a rigid rod, wheel can free in and out track and slide in track, rigid bar and cart base plate are fixed with bolts, and cart base plate has certain rigidity and intensity and box out in centre.

6. steel bar mechanics performance tester for testing under ultra-low temperature surroundings according to claim 5, is characterized in that: cart base plate selects steel plate or scale board.

7. steel bar mechanics performance tester for testing under ultra-low temperature surroundings according to claim 6, it is characterized in that: cryogenic testing case is columnar structured, four 360 degree of swiveling wheels are provided with in bottom half symmetry, the tank wall of cryogenic testing case is divided into internal protection layer, heat-insulation layer, exterior cover sheets from inside to outside, internal protection layer is made up of aluminium alloy or ultralow temperature 06Ni9 steel, heat-insulation layer adopts polyurethane sheet to make, and exterior cover sheets adopts general steel plate to make; Casing divides upper cover and lower box two parts, and upper cover and lower box adopt tongue and groove to be connected, and is provided with gasket seal and lower seal pad, and upper gasket seal and lower seal pad adopt trifluoro mat material material; Upper cover enclosed switch selects plain bolt to connect or strong electromagnet switch connects, and upper and lower two parts are respectively equipped with handle and pick and place to facilitate casing; The tank wall of cryogenic testing case is crossed with fixed wiring, fixed wiring has internal wiring head and external the end of a thread, internal wiring head is connected with internal measurement equipment, external measurement devices respectively by connecting line with external the end of a thread, internal measurement equipment is ultralow temperature foil gauge, ultralow temperature temperature inductor, and external measurement devices is the display device of parameters; Cryogenic testing lower box part is provided with controller, controller is for regulating the evaporation capacity of liquid nitrogen in the unit interval thus controlling the temperature of box house, controller is connected with liquid nitrogen container with electric cabinet with liquid nitrogen pipe respectively by electrical control lines, and then the self-correcting mechanism of formation temperature.

8. steel bar mechanics performance tester for testing under ultra-low temperature surroundings according to claim 7, is characterized in that: cryogenic testing box body upper and lower two ends symmetry be provided with opening, both ends open all in large outer little tapered, both ends open place is provided with sealing-plug.

9. steel bar mechanics performance tester for testing under ultra-low temperature surroundings according to claim 8, is characterized in that: have in the outer face of opening and in hole, shrink by exterior cover sheets the hoop formed, and hoop is used for limiting the displacement of sealing-plug; Form casing projection outside the inner face of opening, casing projection is similarly body structure part, and the protruding lateral surface of casing is rod thread, and the protruding bottom surface of casing is provided with annular protrusion; Sealing-plug is taper and major part end forms the head of a nail, and sealing-plug adopts trifluoro mat material to make, and sealing-plug is fixed in casing projection by bowl-type nut.

10. steel bar mechanics performance tester for testing under ultra-low temperature surroundings according to claim 9, it is characterized in that: bowl-type nut is that ultralow temperature 06Ni9 steel is made, wherein the medial surface of bowl-type nut makes rod thread, is threaded to project through with casing; The inner bottom surface of bowl-type nut is provided with annular protrusion; Bowl-type nut end face is provided with bowl-type nut and boxes out.