A test system and control method for ultra-low temperature impact test

Abstract

The present invention discloses a test system and control method for ultra-low temperature impact testing. The test system comprises a liquid nitrogen storage device, a delivery system, and a closed test chamber. The liquid nitrogen storage device includes a liquid nitrogen storage tank with an evaporation device at its bottom and a stirring device at its center. The delivery system includes a delivery pipeline, the upper end of the liquid nitrogen storage tank being connected to the test chamber via the delivery pipeline, and a temperature control device being provided at its center. The control method includes steps S1-S10. The device of the present invention utilizes a cryogenic gaseous working fluid to control the ambient temperature of a local area of ​​the equipment. Adjustment to different ambient temperature requirements is achieved by varying the power of the thermal evaporation device and the stirring rate of the stirring device. The device has the advantages of wide temperature coverage, automated parameter adjustment, and reliable operation.

Description

Technical Field

[0001] The present invention relates to the technical field of ultra-low temperature impact testing, and in particular to a testing system and a control method for an ultra-low temperature impact test. Background Art

[0002] The Split Hopkinson bar testing system, consisting of a Split Hopkinson Pressure Bar (SHPB) and a Split Hopkinson Tension Bar (SHTB), is a classic device for studying the mechanical response of materials at high strain rates. It is of great significance for the design and research of materials structures. Its core concept is to decouple stress wave effects from strain rate effects during experiments, thereby establishing the stress-strain relationship of materials at high strain rates.

[0003] While some temperature maintenance devices have been reported both domestically and internationally, their temperature ranges are limited and difficult to meet the demands of engineering applications. With the advancement of engineering construction, the problem of testing the impact dynamic mechanical properties of low-temperature solid materials urgently needs to be addressed. Existing temperature maintenance devices have poor temperature control accuracy, and the temperature control range cannot meet the requirements of high-precision testing, nor can they meet the requirements of ultra-low temperature control. Summary of the Invention

[0004] In view of the above-mentioned deficiencies in the prior art, the present invention provides a test system and control method for ultra-low temperature shock testing that can realize timely and automatic temperature control and adjustment.

[0005] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is:

[0006] Provided is a test system for an ultra-low temperature shock test, comprising a liquid nitrogen storage device, a conveying system, and a closed test chamber. The liquid nitrogen storage device comprises a liquid nitrogen storage tank, an evaporation device is provided at the bottom of the liquid nitrogen storage tank, and a stirring device is provided in the middle of the liquid nitrogen storage tank; the conveying system comprises a conveying pipeline, the upper end of the liquid nitrogen storage tank is connected to the test chamber through the conveying pipeline, and a temperature regulating device is provided in the middle of the conveying pipeline; the evaporation device converts low-temperature liquid nitrogen into a low-temperature gaseous working medium by heating, and the stirring device is used to break large-diameter steam bubbles into small-diameter steam bubbles, which are further cooled during the floating process, thereby reducing the temperature of the outlet low-temperature gaseous working medium.

[0007] Furthermore, temperature sensors are provided at the outlet of the liquid nitrogen storage tank, in the temperature regulating device and in the test box, and a control valve is provided in the temperature regulating device.

[0008] A control method for the above-mentioned ultra-low temperature impact test system is provided, which includes the following steps:

[0009] S1: Assemble the liquid nitrogen storage device, delivery system and closed test chamber. After assembly, open the evaporator and stirring device to evaporate the low-temperature liquid nitrogen into a low-temperature gaseous working medium, which is then delivered to the test chamber through the delivery pipeline;

[0010] S2: The temperature sensor collects the temperature t1 in the test chamber and compares the temperature t1 with the test set temperature T. If t1≠T, the delivery efficiency of the low-temperature gaseous working medium needs to be controlled. The temperature value Δt1 that needs to be adjusted in the test chamber is calculated: Δt1=|T-t1|; then the process proceeds to step S3.

[0011] S3: Compare the temperature value Δt1 with the temperature adjustment threshold value t of the stirring device 1阈值 , the temperature adjustment threshold value t of the evaporation device 2阈值 Compare, and t 1阈值 <t 2阈值 :

[0012] If Δt1≤t 1阈值 , it is determined that the temperature can be controlled by adjusting the stirring rate of the stirring device;

[0013] When T-t1>0, the current temperature in the test chamber is too low, and the stirring device is controlled to reduce the stirring rate;

[0014] When T-t1 is less than 0, the current temperature in the test chamber is too high, and the stirring device is controlled to increase the stirring rate;

[0015] The power of the evaporation device remains unchanged until the temperature in the test chamber reaches T, and then the process goes to step S4;

[0016] If t 1阈值 <Δt1≤t 2阈值 , it is determined that the temperature can be controlled by controlling the power of the evaporation device;

[0017] When T-t1>0, the current temperature in the test chamber is too low, and the evaporation device is controlled to reduce power;

[0018] When T-t1 < 0, the current temperature in the test chamber is too high, and the evaporation device is controlled to increase the power;

[0019] The stirring speed of the stirring device remains unchanged until the temperature in the test chamber reaches T, and then the process proceeds to step S4;

[0020] If t 2阈值 <Δt1, it is determined that the power of the evaporation device and the stirring speed of the stirring device need to be adjusted simultaneously to control the temperature;

[0021] When T-t1>0, the current temperature in the test chamber is too low, and the evaporation device is controlled to reduce the power and the stirring device to reduce the stirring rate;

[0022] When T-t1 is less than 0, the current temperature in the test chamber is too high, and the evaporation device is controlled to increase the power and the stirring device to increase the stirring speed;

[0023] Until the temperature in the test chamber reaches T, enter step S4;

[0024] S4: Maintain the power of the evaporator and the stirring rate of the stirring device when the temperature in the test chamber reaches T in step S3, and collect the temperature t2 in the test chamber again after a set time interval a;

[0025] S5: Compare the temperature t2 with the test set temperature T:

[0026] If t2=T, proceed to step S6;

[0027] If t2≠T, calculate the temperature difference Δt2=|T-t2|;

[0028] When T-t2<0, and Δt2>t 2阈值 +t 1阈值 When the leakage occurs between the liquid nitrogen storage device, the delivery system and the closed test chamber, the staff rechecks the sealing between the liquid nitrogen storage device, the delivery system and the closed test chamber, repairs the leakage location, and returns to step S2;

[0029] Otherwise, replace Δt1 with Δt2 and return to step S3;

[0030] S6: After collecting the temperature in the test chamber n times, the temperature data set (t1, t2, ···, t n ), each time the temperature in the test chamber is collected, the temperature b in the temperature regulating device, the stirring rate v of the stirring device, and the power p of the evaporation device are collected;

[0031] S7: Calculate the temperature loss coefficient k in the test chamber and the temperature control device:

[0032]

[0033] Among them, e is any temperature acquisition process;

[0034] S8: Calculate the average values ​​v and p of the stirring rate v and power p when the temperature reaches T after each temperature adjustment:

[0035]

[0036] S9: Establish a temperature control model based on the temperature loss coefficients k, v and p:

[0037]

[0038] Wherein, f is the promotion coefficient of the power of the evaporation device on the cooling effect, and q is the promotion coefficient of the stirring rate of the stirring device on the cooling effect;

[0039] S10: Input the temperature control model into the test system, and control the power of the evaporation device and the stirring rate of the stirring device through the temperature b collected by the temperature regulating device, so that the temperature in the test chamber reaches the T value.

[0040] The beneficial effects of the present invention are as follows: the device of the present invention intends to use low-temperature gaseous working fluid to control the ambient temperature of a local area of ​​the equipment, and to achieve adjustment of different ambient temperature requirements by changing the power of the thermal evaporation device and the stirring rate of the stirring device. It has the advantages of wide temperature coverage, automatic parameter adjustment, and reliable device.

[0041] This invention provides a low-temperature environment compatible with Hopkinson experimental equipment, facilitating low-temperature impact testing of solid materials with high strain rate impact loading. A temperature control device in the middle section of the delivery pipeline allows the cryogenic gaseous fluid to reach the set test temperature. Real-time feedback is used to adjust the power of the evaporator and agitator in the liquid nitrogen storage tank, enabling the discharge rate of the cryogenic gaseous fluid to meet the requirements of tests with the same temperature but different cooling powers. The temperature is measured by a temperature measurement system and fed back to a microcomputer module for intelligent control of the evaporator, agitator, and temperature control device. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is the principle block diagram of the test system for ultra-low temperature impact test. DETAILED DESCRIPTION

[0043] The specific embodiments of the present invention are described below to facilitate understanding of the present invention by those skilled in the art. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the appended claims, these changes are obvious, and all inventions and creations utilizing the concepts of the present invention are protected.

[0044] like Figure 1 As shown, the test system of the ultra-low temperature shock test of this scheme includes a liquid nitrogen storage device, a conveying system and a closed test chamber. The liquid nitrogen storage device includes a liquid nitrogen storage tank, an evaporation device is provided at the bottom of the liquid nitrogen storage tank, and a stirring device is provided in the middle of the liquid nitrogen storage tank; the conveying system includes a conveying pipe, the upper end of the liquid nitrogen storage tank is connected to the test chamber through the conveying pipe, and a temperature regulating device is provided in the middle of the conveying pipe; the evaporation device converts the low-temperature liquid nitrogen into a low-temperature gaseous working medium by heating, and the stirring device is used to break large-diameter steam bubbles into small-diameter steam bubbles. The small-diameter steam bubbles are further cooled during the floating process, thereby reducing the temperature of the outlet low-temperature gaseous working medium.

[0045] In this embodiment, temperature sensors are provided at the outlet of the liquid nitrogen storage tank, in the temperature regulating device, and in the test chamber. A control valve is provided in the temperature regulating device to control the shutoff of the delivery pipeline.

[0046] The control method of the test system for the ultra-low temperature impact test comprises the following steps:

[0047] S1: Assemble the liquid nitrogen storage device, delivery system and closed test chamber. After assembly, open the evaporator and stirring device to evaporate the low-temperature liquid nitrogen into a low-temperature gaseous working medium, which is then delivered to the test chamber through the delivery pipeline;

[0048] S2: The temperature sensor collects the temperature t1 in the test chamber and compares the temperature t1 with the test set temperature T. If t1≠T, the delivery efficiency of the low-temperature gaseous working medium needs to be controlled. The temperature value Δt1 that needs to be adjusted in the test chamber is calculated: Δt1=|T-t1|; then the process proceeds to step S3.

[0049] S3: Compare the temperature value Δt1 with the temperature adjustment threshold value t of the stirring device 1阈值 , the temperature adjustment threshold value t of the evaporation device 2阈值 Compare, and t 1阈值 <t 2阈值 :

[0050] If Δt1≤t 1阈值 , it is determined that the temperature can be controlled by adjusting the stirring rate of the stirring device;

[0051] When T-t1>0, the current temperature in the test chamber is too low, and the stirring device is controlled to reduce the stirring rate;

[0052] When T-t1 is less than 0, the current temperature in the test chamber is too high, and the stirring device is controlled to increase the stirring rate;

[0053] The power of the evaporation device remains unchanged until the temperature in the test chamber reaches T, and then the process goes to step S4;

[0054] If t 1阈值 <Δt1≤t 2阈值 , it is determined that the temperature can be controlled by controlling the power of the evaporation device;

[0055] When T-t1>0, the current temperature in the test chamber is too low, and the evaporation device is controlled to reduce power;

[0056] When T-t1 < 0, the current temperature in the test chamber is too high, and the evaporation device is controlled to increase the power;

[0057] The stirring speed of the stirring device remains unchanged until the temperature in the test chamber reaches T, and then the process proceeds to step S4;

[0058] If t 2阈值 <Δt1, it is determined that the power of the evaporation device and the stirring speed of the stirring device need to be adjusted simultaneously to control the temperature;

[0059] When T-t1>0, the current temperature in the test chamber is too low, and the evaporation device is controlled to reduce the power and the stirring device to reduce the stirring rate;

[0060] When T-t1 is less than 0, the current temperature in the test chamber is too high, and the evaporation device is controlled to increase the power and the stirring device to increase the stirring speed;

[0061] Until the temperature in the test chamber reaches T, enter step S4;

[0062] S4: Maintain the power of the evaporator and the stirring rate of the stirring device when the temperature in the test chamber reaches T in step S3, and collect the temperature t2 in the test chamber again after a set time interval a;

[0063] S5: Compare the temperature t2 with the test set temperature T:

[0064] If t2=T, proceed to step S6;

[0065] If t2≠T, calculate the temperature difference Δt2=|T-t2|;

[0066] When T-t2<0, and Δt2>t 2阈值 +t 1阈值 When the leakage occurs between the liquid nitrogen storage device, the delivery system and the closed test chamber, the staff rechecks the sealing between the liquid nitrogen storage device, the delivery system and the closed test chamber, repairs the leakage location, and returns to step S2;

[0067] Otherwise, replace Δt1 with Δt2 and return to step S3;

[0068] S6: After collecting the temperature in the test chamber n times, the temperature data set (t1, t2, ···, t n ), each time the temperature in the test chamber is collected, the temperature b in the temperature regulating device, the stirring rate v of the stirring device, and the power p of the evaporation device are collected;

[0069] S7: Calculate the temperature loss coefficient k in the test chamber and the temperature control device:

[0070]

[0071] Among them, e is any temperature acquisition process;

[0072] S8: Calculate the average value of stirring rate v and power p when the temperature reaches T after each temperature adjustment and

[0073]

[0074] S9: According to the temperature loss coefficient k, and Establish a temperature control model:

[0075]

[0076] Wherein, f is the promotion coefficient of the power of the evaporation device on the cooling effect, and q is the promotion coefficient of the stirring rate of the stirring device on the cooling effect;

[0077] S10: Input the temperature control model into the test system, and control the power of the evaporation device and the stirring rate of the stirring device through the temperature b collected by the temperature regulating device, so that the temperature in the test chamber reaches the T value.

[0078] The device of the present invention intends to use low-temperature gaseous working fluid to control the ambient temperature of local areas of the equipment, and to achieve adjustment of different ambient temperature requirements by changing the power of the thermal evaporation device and the stirring rate of the stirring device. It has the advantages of wide temperature coverage, automatic parameter adjustment, and reliable device.

[0079] This invention provides a low-temperature environment compatible with Hopkinson experimental equipment, facilitating low-temperature impact testing of solid materials with high strain rate impact loading. A temperature control device in the middle section of the delivery pipeline allows the cryogenic gaseous fluid to reach the set test temperature. Real-time feedback is used to adjust the power of the evaporator and agitator in the liquid nitrogen storage tank, enabling the discharge rate of the cryogenic gaseous fluid to meet the requirements of tests with the same temperature but different cooling powers. The temperature is measured by a temperature measurement system and fed back to a microcomputer module for intelligent control of the evaporator, agitator, and temperature control device.

Claims

1. A test system for ultra-low temperature impact test, characterized in that: The invention comprises a liquid nitrogen storage device, a delivery system and a closed test chamber. The liquid nitrogen storage device comprises a liquid nitrogen storage tank, an evaporation device is provided at the bottom of the liquid nitrogen storage tank, and a stirring device is provided in the middle of the liquid nitrogen storage tank. The delivery system comprises a delivery pipe, the upper end of the liquid nitrogen storage tank is connected to the test chamber through the delivery pipe, and a temperature regulating device is provided in the middle of the delivery pipe. The evaporation device converts low-temperature liquid nitrogen into low-temperature gaseous working medium by heating. The stirring device is used to break large-diameter steam bubbles into small-diameter steam bubbles. The small-diameter steam bubbles are further cooled during the floating process, thereby reducing the temperature of the outlet low-temperature gaseous working medium. The power of the evaporation device and the stirring rate of the stirring device are controlled by the temperature b collected by the temperature regulating device, so that the temperature in the test box reaches the T value.

2. The ultra-low temperature impact test system according to claim 1, characterized in that: Temperature sensors are provided at the outlet of the liquid nitrogen storage tank, in the temperature regulating device and in the test box, and a control valve is provided in the temperature regulating device.

3. A control method for a test system for ultra-low temperature impact test according to claim 1 or 2, characterized in that: The following steps are involved: S1: Assemble the liquid nitrogen storage device, delivery system and closed test chamber. After assembly, open the evaporator and stirring device to evaporate the low-temperature liquid nitrogen into a low-temperature gaseous working medium, which is then delivered to the test chamber through the delivery pipeline; S2: The temperature sensor collects the temperature t1 in the test chamber and compares the temperature t1 with the test set temperature T. If t1≠T, the delivery efficiency of the low-temperature gaseous working medium needs to be controlled. The temperature value Δt1 that needs to be adjusted in the test chamber is calculated: Δt1=|T-t1|; then the process proceeds to step S3. S3: Compare the temperature value Δt1 with the temperature adjustment threshold value t of the stirring device 1阈值 , the temperature adjustment threshold value t of the evaporation device 2阈值 Compare, and t 1阈值 <t 2阈值 : If Δt1≤t 1阈值 , it is determined that the temperature can be controlled by adjusting the stirring rate of the stirring device; When T-t1>0, the current temperature in the test chamber is too low, and the stirring device is controlled to reduce the stirring rate; When T-t1 is less than 0, the current temperature in the test chamber is too high, and the stirring device is controlled to increase the stirring rate; The power of the evaporation device remains unchanged until the temperature in the test chamber reaches T, and then the process goes to step S4; If t 1阈值 <Δt1≤t 2阈值 , it is determined that the temperature can be controlled by controlling the power of the evaporation device; When T-t1>0, the current temperature in the test chamber is too low, and the evaporation device is controlled to reduce power; When T-t1 < 0, the current temperature in the test chamber is too high, and the evaporation device is controlled to increase the power; The stirring speed of the stirring device remains unchanged until the temperature in the test chamber reaches T, and then the process proceeds to step S4; If t 2阈值 <Δt1, it is determined that the power of the evaporation device and the stirring speed of the stirring device need to be adjusted simultaneously to control the temperature; When T-t1>0, the current temperature in the test chamber is too low, and the evaporation device is controlled to reduce the power and the stirring device to reduce the stirring rate; When T-t1 is less than 0, the current temperature in the test chamber is too high, and the evaporation device is controlled to increase the power and the stirring device to increase the stirring speed; Until the temperature in the test chamber reaches T, enter step S4; S4: Maintain the power of the evaporator and the stirring rate of the stirring device when the temperature in the test chamber reaches T in step S3, and collect the temperature t2 in the test chamber again after a set time interval a; S5: Compare the temperature t2 with the test set temperature T: If t2=T, proceed to step S6; If t2≠T, calculate the temperature difference Δt2=|T-t2|; When T-t2<0, and Δt2>t 2阈值 +t 1阈值 When the leakage occurs between the liquid nitrogen storage device, the delivery system and the closed test chamber, the staff rechecks the sealing between the liquid nitrogen storage device, the delivery system and the closed test chamber, repairs the leakage location, and returns to step S2; Otherwise, replace Δt1 with Δt2 and return to step S3; S6: After collecting the temperature in the test chamber n times, the temperature data set of the test chamber control (t1, t2, ···, t n ), every time the temperature in the test chamber is collected, the temperature b in the temperature regulating device, the stirring rate v of the stirring device and the power p of the evaporation device are collected; S7: Calculate the temperature loss coefficient k in the test chamber and the temperature control device: Among them, e is any temperature acquisition process; S8: Calculate the average value of stirring rate v and power p when the temperature reaches T after each temperature adjustment and : ， S9: According to the temperature loss coefficient k, and Establish a temperature control model: Wherein, f is the promotion coefficient of the power of the evaporation device on the cooling effect, and q is the promotion coefficient of the stirring rate of the stirring device on the cooling effect; S10: Input the temperature control model into the test system, and control the power of the evaporation device and the stirring rate of the stirring device through the temperature b collected by the temperature regulating device, so that the temperature in the test chamber reaches the T value.

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