Liquid helium ultralow-temperature impact system based on vacuum and using method of liquid helium ultralow-temperature impact system

Abstract

The invention discloses a liquid helium ultralow-temperature impact system based on vacuum and a use method thereof, and belongs to the technical field of liquid helium ultralow-temperature impact mechanical property testing equipment, and the liquid helium ultralow-temperature impact system based on vacuum comprises an ultralow-temperature vacuum experiment cavity, a vacuum unit, a liquid helium supply device, an impact device and a strain acquisition device. The device is clear in structure and simple in principle; liquid helium is adopted for refrigeration, so that the temperature in the experiment cavity can reach an ultralow temperature environment, and the device can be used for impact loading mechanical property testing of different samples in a complex stress state in the ultralow temperature environment.

Description

Technical Field

[0001] The invention belongs to the technical field of liquid helium ultra-low temperature impact mechanical property testing equipment, and in particular relates to a liquid helium ultra-low temperature impact system based on vacuum and a use method thereof. Background Art

[0002] The safety of materials operating at low ambient temperatures is a current problem and challenge. In particular, the dynamic characteristics of materials in the 4.2K-77K temperature range are a fundamental issue in the safety protection of deep space exploration structures, and are also one of the key and difficult points in the research of detector impact protection engineering. While increasing the strength of the material, the low temperature environment will reduce its fracture toughness, leading to rapid crack expansion. This brittle fracture often occurs without warning, which will be catastrophic to the safety protection of materials at low temperatures.

[0003] Generally speaking, the toughening of metal materials requires them to have high elastic modulus, low stacking fault energy and phase stability. However, the research on the toughening characteristics of metals at ultra-low temperatures mainly focuses on static loading, and the research on impact loading under complex stress states is lacking, and the microscopic mechanism of its dynamic toughening is still unclear. Based on this, the present invention creates a dynamic mechanics experimental device for materials under ultra-low temperatures (4.2K~77K) and complex stress states, combines multi-scale experimental methods to study the dynamic mechanical properties of fiber metal composites at ultra-low temperatures, explores the deformation and failure evolution laws of fiber metal composites under low-temperature dynamic loading, clarifies the microscopic mechanical mechanism of its ultra-low temperature dynamic toughening, and further explains the association and competition mechanism between ultra-low temperatures and high strain rates and stress states. Summary of the invention

[0004] The purpose of the present invention is to perform ultra-low temperature cooling on the material while the material is subjected to impact loading under a complex stress state, and to provide a liquid helium ultra-low temperature impact system based on vacuum and a method of using the same. The present invention is based on the separated Hopkinson pressure bar technology, combined with an ultra-low temperature vacuum experimental chamber to provide an ultra-low temperature environment for the sample, and can measure the mechanical properties of the sample from 4k to 77k. The ultra-low temperature vacuum experimental chamber can be cooled by liquid helium or liquid nitrogen; the size of the sample holder can be selected, and the mechanical properties of materials of different diameters and thicknesses can be tested; the bottom of the sample holder uses an indium sheet, which has good thermal conductivity, so that the sample temperature measured by the temperature sensor is more accurate; there is a transparent observation window in front of the cavity, and the structural evolution and destruction process of the material can be clearly observed; the device structure is clear and the principle is simple.

[0005] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical scheme:

[0006] A liquid helium ultra-low temperature shock system based on vacuum, the liquid helium ultra-low temperature shock system based on vacuum comprising an ultra-low temperature vacuum experimental chamber, a vacuum unit, a liquid helium supply device, an impact device and a strain acquisition device;

[0007] The ultra-low temperature vacuum experiment chamber comprises an observation window, an impact device access port, a liquid helium transmission port, a liquid helium reflux port, a vacuum interface, a fixture, a sample holder, a liquid helium temperature sensor, a liquid nitrogen temperature sensor, an indium sheet and a stage; impact device access ports are arranged on opposite sides of the chamber for the incident rod and the transmission rod of the impact device to extend into, and an observation window, a liquid helium transmission port, a liquid helium reflux port and a vacuum interface are arranged on the side of the ultra-low temperature vacuum experiment chamber; a stage is arranged inside the chamber, an indium sheet is arranged on the stage, a sample holder is arranged on the indium sheet, a fixture is arranged vertically above the sample holder, and a sample is placed between the fixture and the sample holder so that the sample is located between the incident rod and the transmission rod of the impact device;

[0008] The vacuum unit comprises an air pump and a controller, the air pump is connected to the vacuum interface via a bellows, and the controller is used to control the air pump;

[0009] The liquid helium supply device comprises a liquid helium tank, a helium pump, a liquid helium transmission pipe, a helium transmission pipe and a temperature controller; the liquid helium tank is connected to the helium pump through the helium transmission pipe, the liquid helium tank is connected to the liquid helium transmission inlet through the liquid helium transmission pipe, and the temperature controller is used to measure the temperature of the internal environment of the ultra-low temperature vacuum experiment cavity;

[0010] The impact device comprises a gas gun, an impact rod, an incident rod, a transmission rod, an absorption rod and a momentum well; the gas gun, the impact rod, the incident rod, the transmission rod, the absorption rod and the momentum well are arranged in sequence along a straight line direction, the gas gun, the impact rod and the incident rod are arranged on one side of the ultra-low temperature vacuum experiment cavity, and the transmission rod, the absorption rod and the momentum well are arranged on the other side of the ultra-low temperature vacuum experiment cavity;

[0011] The strain acquisition device comprises a strain gauge, a strain meter and an oscilloscope. The strain gauge is arranged on the incident rod and the transmission rod, the strain gauge is connected to the strain meter, and the strain meter is connected to the oscilloscope.

[0012] In the above technical solution, the ultra-low temperature vacuum experiment chamber further includes a base, and the base is arranged at the bottom of the chamber.

[0013] In the above technical solution, the impact device further includes a support platform, and the support platform is arranged below the incident rod and the transmission rod for fixing.

[0014] In the above technical solution, the sample rack has different sizes and specifications and is replaceable.

[0015] In the above technical solution, the observation window is transparent and made of glass.

[0016] A method for using a liquid helium ultra-low temperature shock system under vacuum comprises the following steps:

[0017] Step 1: Select a suitable sample holder according to the size of the sample, place the sample on the sample holder through the observation window, clamp it with the incident rod and the transmission rod, and tighten the fixture.

[0018] Step 2: The molecular pump controller is connected to the vacuum interface through a metal bellows to evacuate the ultra-low temperature vacuum experimental chamber.

[0019] Step 3: Turn on the helium pump and siphon the liquid helium in the liquid helium tank through the helium transmission tube to press the liquid helium into the liquid helium transmission inlet in the ultra-low temperature vacuum experiment chamber. The liquid helium refluxes in the ultra-low temperature vacuum experiment chamber and flows out through the liquid helium reflux outlet, providing a continuous ultra-low temperature environment for the chamber. The temperature is then monitored in real time by the temperature controller.

[0020] Step 4: Conduct a split Hopkinson bar experiment. The incident bar and the transmission bar are supported by a support platform so that they are aligned horizontally and vertically. The impact bar is hit by the high-pressure gas in the gas gun to generate a compressive stress pulse that propagates along the incident bar toward the sample. When the stress wave reaches the interface between the incident bar and the sample, a part of it is reflected back to the incident bar, and the other part loads the sample and is transmitted to the transmission bar. Finally, the energy is absorbed by the absorption bar and the momentum well. The incident pulse, reflected pulse, and transmitted pulse are recorded by strain gauges attached to the incident bar and the transmission bar.

[0021] In the above technical solution, in step 4, the stress, strain rate and strain on the sample are determined according to the one-dimensional stress wave theory, thereby making a stress-strain curve and a strain-strain rate curve:

[0022] ;

[0023] ;

[0024] ;

[0025] Where E, c, A are the elastic modulus, wave velocity and cross-sectional area of ​​the compression rod. , are the initial cross-sectional area and initial length of the specimen.

[0026] Beneficial effects:

[0027] (1) The device has a clear structure and simple principle;

[0028] (2) The ultra-low temperature vacuum experiment chamber can be cooled by either liquid helium or liquid nitrogen;

[0029] (3) The size of the sample holder can be selected, and the mechanical properties of materials with different diameters and thicknesses can be tested;

[0030] (4) The bottom of the sample holder is made of indium sheet, which has good thermal conductivity, making the sample temperature measured by the temperature sensor more accurate;

[0031] (5) There is a transparent observation window in front of the cavity, which can clearly observe the structural evolution and destruction process of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a front view of the ultra-low temperature vacuum experiment chamber device of the present invention;

[0033] Figure 2 This is a rear view of the ultra-low temperature vacuum experiment chamber device of the present invention;

[0034] Figure 3 A top view of the ultra-low temperature vacuum experiment chamber device of the present invention;

[0035] Figure 4 This is a cross-sectional view of the ultra-low temperature vacuum experiment chamber device of the present invention;

[0036] Figure 5 This is a schematic diagram of the fixture structure in the ultra-low temperature vacuum experiment chamber device of the present invention;

[0037] Figure 6 It is the schematic diagram of the vacuum unit (I);

[0038] Figure 7 It is the schematic diagram of the vacuum unit (II);

[0039] Figure 8 This is a schematic diagram of a liquid helium ultra-low temperature shock system based on vacuum;

[0040] Fig. 9 It is a temperature-time curve based on the data monitored by the temperature controller;

[0041] Fig.10 This is the stress-strain curve when the sample is destroyed under ultra-low temperature conditions;

[0042] Fig.11 This is the strain-strain rate curve when the sample fails under ultra-low temperature conditions.

[0043] In the figure: 1- observation window; 2- base; 3- impact device access port; 4- liquid helium transmission port; 5- liquid helium reflux outlet; 6- vacuum interface; 7- holder; 8- sample rack; 9- liquid helium temperature sensor; 10- liquid nitrogen temperature sensor; 11- indium sheet; 12- stage; 13- power switch; 14- mechanical pump switch; 15- molecular pump switch; 16- molecular pump controller; 17- vacuum gauge panel; 18- power socket; 19- exhaust port; 20- fan; 21- mechanical pump observation port. DETAILED DESCRIPTION

[0044] The following is combined with Figure 1-8 The present invention is described in detail with specific embodiments. However, the following embodiments are limited to explaining the present invention, and the protection scope of the present invention should include the entire contents of the claims, and through the description of the following embodiments, those skilled in the art can fully implement the entire contents of the claims of the present invention.

[0045] Example

[0046] Figure 1 This is a front view of the ultra-low temperature vacuum experiment chamber device of the present invention. Figure 2 This is a rear view of the ultra-low temperature vacuum experiment chamber device of the present invention. Figure 3 It is a top view of the ultra-low temperature vacuum experiment chamber device of the present invention. Figure 4 This is a cross-sectional view of the ultra-low temperature vacuum experimental chamber device of the present invention. Figure 5 It is a schematic diagram of the fixture structure in the ultra-low temperature vacuum experiment chamber device of the present invention. Figure 6 Schematic diagram of the vacuum unit (I). Figure 7 This is a schematic diagram of the vacuum unit (II). Figure 8 Schematic diagram of the liquid helium ultra-low temperature shock system under vacuum. Fig. 9 It is a temperature-time curve based on the data monitored by the temperature controller. Fig.10 This is the stress-strain curve when the sample is destroyed under ultra-low temperature conditions. Fig.11 This is the strain-strain rate curve when the sample fails under ultra-low temperature conditions.

[0047] like Figure 1-8 As shown, a liquid helium ultra-low temperature impact system based on vacuum proposed by the present invention includes an observation window 1, a base 2, an impact device access port 3, a liquid helium transmission port 4, a liquid helium reflux port 5, a vacuum interface 6, a holder 7, a sample rack 8, a liquid helium temperature sensor 9, a liquid nitrogen temperature sensor 10, an indium sheet 11, a stage 12, a switch 13, a mechanical pump switch 14, a molecular pump switch 15, a molecular pump controller 16, a vacuum gauge panel 17, a power socket 18, an exhaust port 19, a fan 20, a mechanical pump observation port 21, a liquid helium tank, a helium pump, a liquid helium transmission pipe, a helium transmission pipe, and a temperature controller.

[0048] The liquid helium ultra-low temperature impact system based on vacuum comprises an ultra-low temperature vacuum experimental chamber, a vacuum unit, a liquid helium supply device, an impact device and a strain collection device.

[0049] The ultra-low temperature vacuum experiment chamber comprises an observation window 1, a base 2, an impact device access port 3, a liquid helium transmission port 4, a liquid helium reflux port 5, a vacuum interface 6, a fixture 7, a sample rack 8, a liquid helium temperature sensor 9, a liquid nitrogen temperature sensor 10, an indium sheet 11, and a stage 12. When the device is used for an experiment: the base 2 is fixed on the impact device support arm, and the incident rod extends into the ultra-low temperature vacuum experiment chamber through the impact device access port 3; the indium sheet 11 is located above the stage 12; the liquid helium temperature sensor 9 and the liquid nitrogen temperature sensor 10 are located on both sides of the indium sheet 11; and the sample rack 8 is located above the indium sheet 11.

[0050] The vacuum unit includes a switch 13, a mechanical pump switch 14, a molecular pump switch 15, a molecular pump controller 16, a vacuum gauge panel 17, a power socket 18, an exhaust port 19, a fan 20, and a mechanical pump observation port 21; the molecular pump controller 16 controls the ultra-low temperature vacuum experiment chamber to be evacuated to achieve the vacuum condition of the ultra-low temperature vacuum experiment chamber.

[0051] The liquid helium supply device comprises a liquid helium tank, a helium pump, a liquid helium transmission pipe, a helium transmission pipe, and a temperature controller; the helium pump siphons the liquid helium in the liquid helium tank through the liquid helium transmission pipe and presses it into the ultra-low temperature vacuum experiment cavity through the liquid helium transmission pipe, so as to achieve the ultra-low temperature condition of the ultra-low temperature vacuum experiment cavity, and then the temperature is measured and monitored in real time by the temperature controller.

[0052] The impact device comprises a gas gun, an impact rod, an incident rod, a transmission rod, an absorption rod and a momentum well; the gas gun, the impact rod, the incident rod, the transmission rod, the absorption rod and the momentum well are arranged in sequence along a straight line direction, the gas gun, the impact rod and the incident rod are arranged on one side of the ultra-low temperature vacuum experiment cavity, and the transmission rod, the absorption rod and the momentum well are arranged on the other side of the ultra-low temperature vacuum experiment cavity;

[0053] The strain acquisition device comprises a strain gauge, a strain meter and an oscilloscope. The strain gauge is arranged on the incident rod and the transmission rod, the strain gauge is connected to the strain meter, and the strain meter is connected to the oscilloscope.

[0054] As a preferred solution of this embodiment, the observation window 1 is used to observe the internal situation of the cavity in real time and is made of transparent glass.

[0055] As a preferred solution of this embodiment, the base 2 is used to fix the ultra-low temperature vacuum experiment chamber and is fixed to the support arm of the impact device by two pairs of screws.

[0056] As a preferred solution of this embodiment, the diameter of the impact device access port 3 is slightly larger than that of the incident rod, which is convenient for the incident rod to enter and exit and easy to operate to make it airtight.

[0057] As a preferred solution of this embodiment, the helium pump siphons the liquid helium in the liquid helium tank through the liquid helium transmission tube and presses it into the liquid helium transmission inlet 4 in the ultra-low temperature vacuum experiment cavity, refluxes in the ultra-low temperature vacuum experiment cavity, and flows out through the liquid helium reflux outlet 5, providing a continuous ultra-low temperature environment for the cavity, and then real-time temperature measurement and monitoring is performed by a temperature controller.

[0058] As a preferred solution of this embodiment, the molecular pump controller 16 is connected to the vacuum interface 6 through a metal bellows to evacuate the ultra-low temperature vacuum experiment chamber.

[0059] As a preferred solution of this embodiment, the fixer 7 and the sample rack 8 are both used to fix the sample, and the size of the sample rack is consistent with the sample.

[0060] As a preferred solution of this embodiment, the indium sheet 11 has good thermal conductivity and is used to connect the sample and the temperature sensor to achieve accurate temperature measurement.

[0061] The use process of the liquid helium ultra-low temperature shock system under vacuum of the present invention is as follows:

[0062] When conducting a complex stress state impact loading experiment under an ultra-low temperature environment, before the experiment begins, select a suitable sample holder 8 according to the size of the sample, place the sample on the sample holder from the observation window 1, and clamp it with the incident rod and the transmission rod, and tighten the fixture 7. The molecular pump controller 16 is connected to the vacuum interface 6 through a metal bellows to evacuate the ultra-low temperature vacuum experiment cavity. Turn on the helium pump and siphon the liquid helium in the liquid helium tank through the liquid helium transmission tube into the liquid helium transmission inlet 4 in the ultra-low temperature vacuum experiment cavity through the helium transmission tube, reflux in the ultra-low temperature vacuum experiment cavity, and flow out through the liquid helium reflux outlet 5 to provide a continuous ultra-low temperature environment for the cavity, and then monitor the temperature in real time through the temperature controller. Subsequently, a separate Hopkinson bar experiment is carried out, and the incident rod and the transmission rod are supported by a support platform so that they are aligned horizontally and vertically. The impact rod is hit by the high-pressure gas in the gas gun to generate a compressive stress pulse and propagate along the incident rod toward the sample. When the stress wave reaches the interface between the incident rod and the sample, part of it is reflected back to the incident rod, and the other part loads the sample and is transmitted to the transmission rod, and finally the energy is absorbed by the absorption rod and the momentum well. The incident pulse, reflected pulse and transmitted pulse can be recorded by the strain gauges attached to the incident rod and the transmission rod. The stress, strain rate and strain on the sample can be determined according to the one-dimensional stress wave theory, and the stress-strain curve and strain-strain rate curve can be drawn.

[0063] ;

[0064] ;

[0065] ;

[0066] Where E, c, A are the elastic modulus, wave velocity and cross-sectional area of ​​the compression rod. , are the initial cross-sectional area and initial length of the specimen.

[0067] It should be noted that, according to the above-mentioned embodiments of the present invention, those skilled in the art can fully implement the full scope of the independent claims and dependent rights of the present invention, and the implementation process and method are the same as the above-mentioned embodiments; and the parts not elaborated in detail in the present invention belong to the well-known technology in the field.

[0068] The above descriptions are only some specific implementation methods of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any person familiar with the art within the technical scope disclosed in the present invention should be covered within the protection scope of the present invention.

Claims

1. A liquid helium ultra-low temperature shock system based on vacuum, characterized in that: The liquid helium ultra-low temperature impact system based on vacuum comprises an ultra-low temperature vacuum experimental chamber, a vacuum unit, a liquid helium supply device, an impact device and a strain collection device; The ultra-low temperature vacuum experiment chamber comprises an observation window, an impact device access port, a liquid helium transmission port, a liquid helium reflux port, a vacuum interface, a fixture, a sample holder, a liquid helium temperature sensor, a liquid nitrogen temperature sensor, an indium sheet and a stage; impact device access ports are arranged on opposite sides of the chamber for the incident rod and the transmission rod of the impact device to extend into, and an observation window, a liquid helium transmission port, a liquid helium reflux port and a vacuum interface are arranged on the side of the ultra-low temperature vacuum experiment chamber; a stage is arranged inside the chamber, an indium sheet is arranged on the stage, a sample holder is arranged on the indium sheet, a fixture is arranged vertically above the sample holder, and a sample is placed between the fixture and the sample holder so that the sample is located between the incident rod and the transmission rod of the impact device; The vacuum unit comprises an air pump and a controller, the air pump is connected to the vacuum interface via a bellows, and the controller is used to control the air pump; The liquid helium supply device comprises a liquid helium tank, a helium pump, a liquid helium transmission pipe, a helium transmission pipe and a temperature controller; the liquid helium tank is connected to the helium pump through the helium transmission pipe, the liquid helium tank is connected to the liquid helium transmission inlet through the liquid helium transmission pipe, and the temperature controller is used to measure the temperature of the internal environment of the ultra-low temperature vacuum experiment cavity; The impact device comprises a gas gun, an impact rod, an incident rod, a transmission rod, an absorption rod and a momentum well; the gas gun, the impact rod, the incident rod, the transmission rod, the absorption rod and the momentum well are arranged in sequence along a straight line direction, the gas gun, the impact rod and the incident rod are arranged on one side of the ultra-low temperature vacuum experiment cavity, and the transmission rod, the absorption rod and the momentum well are arranged on the other side of the ultra-low temperature vacuum experiment cavity; The strain acquisition device comprises a strain gauge, a strain meter and an oscilloscope. The strain gauge is arranged on the incident rod and the transmission rod, the strain gauge is connected to the strain meter, and the strain meter is connected to the oscilloscope.

2. The liquid helium ultra-low temperature shock system based on vacuum according to claim 1, characterized in that: The ultra-low temperature vacuum experiment chamber also includes a base, which is arranged at the bottom of the chamber.

3. The liquid helium ultra-low temperature shock system based on vacuum according to claim 1, characterized in that: The impact device also includes a support platform, which is arranged below the incident rod and the transmission rod for fixing.

4. The liquid helium ultra-low temperature shock system based on vacuum according to claim 1, characterized in that: The sample holder has different sizes and specifications and is replaceable.

5. The liquid helium ultra-low temperature shock system based on vacuum according to claim 1, characterized in that: The observation window is transparent and made of glass.

6. A method for using a liquid helium ultra-low temperature shock system under vacuum, characterized in that: The steps include: Step 1: Select a suitable sample holder according to the size of the sample, place the sample on the sample holder through the observation window, and clamp it with the incident rod and the transmission rod, and tighten the fixture; Step 2: The molecular pump controller is connected to the vacuum interface through a metal bellows to evacuate the ultra-low temperature vacuum experiment chamber; Step 3: Turn on the helium pump to siphon the liquid helium in the liquid helium tank through the helium transmission tube and press it into the liquid helium transmission inlet in the ultra-low temperature vacuum experiment chamber. The liquid helium refluxes in the ultra-low temperature vacuum experiment chamber and flows out through the liquid helium reflux outlet, providing a continuous ultra-low temperature environment for the chamber. The temperature is then monitored in real time by the temperature controller. Step 4: Conduct a split Hopkinson bar experiment. The incident rod and the transmission rod are supported by a support platform so that they are aligned horizontally and vertically. The impact rod is hit by the high-pressure gas in the gas gun to generate a compressive stress pulse that propagates along the incident rod toward the sample. When the stress wave reaches the interface between the incident rod and the sample, a part of it is reflected back to the incident rod, and the other part loads the sample and is transmitted to the transmission rod. Finally, the energy is absorbed by the absorbing rod and the momentum well, and the incident pulse, reflected pulse, and transmitted pulse are recorded by strain gauges attached to the incident rod and the transmission rod.

7. The method for using a liquid helium ultra-low temperature shock system under vacuum according to claim 6, characterized in that: In step 4, the stress, strain rate, and strain on the sample are determined according to the one-dimensional stress wave theory, and the stress-strain curve and strain-strain rate curve are drawn.

Images