Device and method for testing free recovery behavior of thermally-driven shape memory material

Abstract

The invention provides a thermal driving shape memory material free recovery behavior testing device and method, and the device comprises a box body, a lead screw sliding table is arranged in the box body, one end of the lead screw sliding table is provided with a force sensor, and the other end of the force sensor is provided with a clamp group. The other end of the clamp set is connected with a fixing table arranged on the lead screw sliding table. The device and the method for testing the free recovery behavior of the thermally-driven shape memory material are used for testing the free recovery behavior of the thermally-driven shape memory material.

Description

Technical Field

[0001] The invention relates to the field of physical property testing of memory materials, and in particular to a device and method for testing the free recovery behavior of heat-driven shape memory materials. Background Art

[0002] Shape memory materials are a class of smart materials with unique properties. They can remember their initial shape under certain conditions and return to their initial shape when subjected to external stimuli (such as temperature, humidity, light, electric field, etc.). Among them, thermally driven materials are the most widely used. Shape memory materials include shape memory alloys, shape memory ceramics, shape memory polymers, etc. Taking thermally driven shape memory polymers as an example, due to their special molecular structure, they can achieve shape memory function by changing temperature and applying external force. Generally speaking, a complete shape memory cycle is divided into three steps: first, after being heated, the temperature of the polymer must be higher than the glass transition temperature. The modulus of this polymer decreases rapidly and the shape can be changed arbitrarily; then, through cooling, the temporary shape of the polymer is frozen. At this time, when the external force is removed, the polymer will not return to its original shape; finally, after heating again, the polymer can automatically return from the temporary shape to the original permanent shape.

[0003] Different chemical compositions and molecular chain structures lead to different recovery properties. However, it is very challenging to accurately and quantitatively evaluate the free recovery behavior of thermally driven shape memory materials. The existing methods mainly include thermomechanical analysis and shape recovery rate test. Among them, thermomechanical analysis evaluates the shape memory performance by monitoring the dimensional changes of the sample during heating or cooling, but it is only applicable to the strain range of a few tens of percent at most, and cannot control the automatic loosening of the clamp. In a complete shape memory cycle, the third step requires loosening the clamp, and human intervention will affect the experimental data collection. The shape recovery rate test method deforms the polymer sample to a specific shape and fixes it, then allows it to recover freely under specific conditions, measures the changes in geometric parameters such as length, angle, and area, and calculates the shape recovery rate for quantitative evaluation. Although this method is simple, it requires human intervention to ensure that the experimental conditions are the same each time, and the shape recovery rate cannot reflect all the information of the polymer in a complete shape memory cycle. Summary of the invention

[0004] The purpose of the present invention is to provide a device and method for testing the free recovery behavior of heat-driven shape memory materials, which can obtain the stress-deformation temperature data of the shape memory material in a complete shape memory cycle without human intervention, and is applicable to a strain range of several hundred percent. By designing a fixture, the free recovery behavior of the shape memory material under various stress forms such as tension, shear, and cyclic loading can be tested.

[0005] To achieve the above-mentioned purpose, the present invention provides a heat-driven shape memory material free recovery behavior testing device, including a box body, a screw slide is arranged in the box body, a force sensor is arranged at one end of the screw slide, a clamp group is arranged at the other end of the force sensor, and the other end of the clamp group is connected to a fixed platform arranged on the screw slide.

[0006] Preferably, the slide table is provided with a limiter, one or two limiters are provided, and the limiters are located on both sides of the fixed table.

[0007] Preferably, the clamp group comprises an upper clamp and a lower clamp, the upper clamp is a non-pneumatic clamp, the lower clamp is a pneumatic clamp, and the lower clamp is connected to a cylinder arranged on one side thereof.

[0008] Preferably, a connection block is provided on one side of the fixing platform, and the connection block is connected to one side of the lower fixture.

[0009] Preferably, a connecting plate is provided at one end of the lead screw slide, and the connecting plate is connected to one end of the force sensor.

[0010] Preferably, the force sensor, the fixture assembly and the fixing platform are all located above the lead screw slide.

[0011] Preferably, the screw slide is provided with a bracket on the back side thereof, a fan is provided on the bracket, at least one fan is provided, and the bracket is connected to the box.

[0012] Preferably, a copper tube is provided inside the box body, and the copper tube is located between the side wall of the box body and the bracket.

[0013] Preferably, it also includes a solenoid valve, an air pump, a high and low temperature constant temperature circulation pump, a data acquisition card, and a PC terminal;

[0014] The lower fixture is connected to the solenoid valve and the air pump;

[0015] The force sensor is connected to a data acquisition card, and the data acquisition card is connected to a PC terminal;

[0016] The copper tube is connected to a high and low temperature constant temperature circulation pump.

[0017] The method for testing the free recovery behavior of heat-driven shape memory materials comprises the following steps:

[0018] Step 1: Start the computer, open the labview software, open the code, control the motor to slowly drive the lead screw to the appropriate position, turn on the air pump, control the solenoid valve to loosen the lower clamp, clamp the two ends of the sample on the clamp group, and then control the solenoid valve to close the lower clamp. Turn on the high and low temperature constant temperature circulation pump, heat to the test temperature, keep warm, and control the motor to stretch the sample to the position where the stress is 0 according to the signal fed back by the force sensor. At this point, the preparation link is completed, and a complete shape memory cycle test is carried out without manual intervention;

[0019] Step 2: A complete shape memory cycle test: The first step is to control the motor to drive the screw to stretch the sample to the specified position. The second step is to control the high and low temperature constant temperature circulation pump to cool the temperature of the environmental box and keep it warm. At this time, the temporary shape of the sample is "frozen". According to the signal feedback from the force sensor, the motor is controlled to unload the sample. Then, the solenoid valve is controlled to release the lower clamp. The sample will maintain the temporary shape and will not shrink back to the initial shape. The third step is to control the high and low temperature constant temperature circulation pump to increase the temperature of the environmental box. As the temperature changes, the sample will gradually return to its initial shape. The camera records the experimental process in real time. At this point, a complete shape memory cycle test is completed.

[0020] Therefore, the present invention adopts the above-mentioned heat-driven shape memory material free recovery behavior testing device and method, which can obtain the stress deformation temperature data of the shape memory material in a complete shape memory cycle without human intervention, and is applicable to a strain range of several hundred percent. By designing a fixture, the free recovery behavior of the shape memory material under various stress forms such as tension, shear, and cyclic loading can be tested. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A schematic diagram of an environmental chamber of a device for testing the free recovery behavior of a heat-driven shape memory material according to the present invention;

[0022] Figure 2 Schematic diagram of the test device for the free recovery behavior of the heat-driven shape memory material of the present invention.

[0023] Reference numerals

[0024] 1. Box; 2. Screw slide; 3. Force sensor; 4. Fixture group; 41. Upper fixture; 42. Lower fixture; 43. Cylinder; 5. Fixed table; 6. Stopper; 7. Connecting block; 8. Connecting plate; 9. Bracket; 10. Fan; 11. Copper tube; 12. Optical platform; 13. Solenoid valve; 14. Air pump; 15. High and low temperature constant temperature circulation pump; 16. Data acquisition card; 17. PC terminal. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0026] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0027] Embodiment 1

[0028] The thermally driven shape memory material free recovery behavior testing device comprises a solenoid valve 13, an air pump 14, a high and low temperature constant temperature circulation pump 15, a data acquisition card 16, a PC terminal 17, and an environmental chamber.

[0029] The environmental chamber includes a box body 1, which is made of an aluminum plate and double-layer transparent glass. A lead screw slide 2 is arranged in the box body 1. A force sensor 3 is arranged at one end of the lead screw slide 2. A clamp group 4 is arranged at the other end of the force sensor 3. The other end of the clamp group 4 is connected to a fixed platform 5 arranged on the lead screw slide 2. The force sensor 3, the clamp group 4, and the fixed platform 5 are all located above the lead screw slide 2.

[0030] The clamp group 4 includes an upper clamp 41 and a lower clamp 42. The upper clamp 41 is a non-pneumatic clamp, and the lower clamp 42 is a pneumatic clamp. A cylinder 43 is provided on one side of the lower clamp 42. The lower clamp 42 is connected to the solenoid valve 13 and the air pump 14 through an air guide pipe, and the air flow of the control pipeline is opened and closed by the solenoid valve 13, thereby controlling the clamping and release of the lower clamp 42.

[0031] The upper fixture 41 is connected to the force sensor 3, and a connecting plate 8 is provided at one end of the lead screw slide 2, and the connecting plate 8 is connected to one end of the force sensor 3. The force sensor 3 is connected to the data acquisition card 16, and the data acquisition card 16 is connected to the PC terminal 17. The force sensor 3 is connected to the input end of the data acquisition card 16, and the motor and the solenoid valve 13 of the lead screw slide 2 are connected to the output end of the data acquisition card 16, and the data acquisition card 16 is connected to the PC terminal 17. When the force sensor 3 is subjected to force, an electrical signal will be generated, and the electrical signal will be collected by the data acquisition card 16 through the signal amplifier, and will be output in real time on the computer interface through the code written by the labview software. At the same time, the code can be written to control the motor and the solenoid valve 13 through the data acquisition card.

[0032] A connecting block 7 is provided on one side of the fixed platform 5, and the connecting block 7 is connected to one side of the lower clamp 42. The fixed platform 5 can slide up and down under the action of the lead screw, thereby driving the movement of the lower clamp 42 to better clamp the sample. At the same time, it can cooperate with the upper clamp 41 to realize the pulling test of the sample.

[0033] One or two limiters 6 are provided, and the limiters 6 are located on both sides of the fixing platform 5, so as to prevent collision caused by incorrect operation of the motor.

[0034] A copper tube 11 is arranged inside the box 1, and the outside is covered with heat insulation cotton. The copper tube 11 is located between the side wall of the box 1 and the bracket 9. The box 1 is provided with a water outlet and a water inlet, which are connected to the high and low temperature constant temperature circulation pump 15. The screw slide 2 is provided with a bracket 9 on its back side. The bracket 9 is provided with a fan 10. At least one fan 10 is provided, and the bracket 9 is connected to the box 1. The temperature inside the environmental box is controlled by heating and cooling the liquid (water or oil) of the high and low temperature constant temperature circulation pump 15.

[0035] During the experiment, one end of the thermocouple is glued to the sample and connected to the data acquisition card 16. By writing code, the collected temperature signal can be output in real time on the computer interface. One side of the environmental chamber has double-layer transparent glass, and the experimental process can be observed through the glass while ensuring thermal insulation. The experimental process is recorded in real time by a camera.

[0036] A perforated plate is provided below the box body 1 as an optical platform 12 to facilitate the movement of the entire environmental box.

[0037] The following is a specific example to illustrate how to use this device:

[0038] Step 1: Start the computer, open the labview software, open the code, control the motor to slowly drive the lead screw to the appropriate position, turn on the air pump, control the solenoid valve 13 to loosen the lower clamp 42, clamp the two ends of the sample on the clamp group 4, and then control the solenoid valve 13 to close the lower clamp 42. Turn on the high and low temperature constant temperature circulation pump 15, heat to the test temperature, keep warm for 10 to 20 minutes, and control the motor to stretch the sample to the position where the stress is 0 according to the signal fed back by the force sensor 3. At this point, the preparation link is completed, and a complete shape memory cycle test can be carried out without manual intervention;

[0039] Step 2: A complete shape memory cycle test: The first step is to control the motor to drive the screw to stretch the sample to the specified position. The second step is to control the high and low temperature constant temperature circulation pump to cool the temperature of the environmental box and keep it warm for 10 to 20 minutes. At this time, the temporary shape of the sample is "frozen". According to the signal feedback from the force sensor 3, the motor is controlled to unload the sample. Then, the solenoid valve 13 is controlled to loosen the lower clamp 42. The sample will maintain the temporary shape and will not shrink back to the initial shape. The third step is to control the high and low temperature constant temperature circulation pump 15 to increase the temperature of the environmental box. As the temperature changes, the sample will gradually return to its initial shape. The camera records the experimental process in real time. At this point, a complete shape memory cycle test is completed.

[0040] Therefore, the present invention adopts the above-mentioned thermally driven shape memory material free recovery behavior testing device and method to test the free recovery behavior of the thermally driven shape memory material.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. Thermally driven shape memory material free recovery behavior test device, It is characterized in that It comprises a box body, in which a lead screw slide is arranged, a force sensor is arranged at one end of the lead screw slide, a clamp group is arranged at the other end of the force sensor, and the other end of the clamp group is connected to a fixed platform arranged on the lead screw slide.

2. The thermally driven shape memory material free recovery behavior testing device according to claim 1, It is characterized in that The slide table is provided with a limiter, one or two limiters are provided, and the limiters are located on both sides of the fixed table.

3. The thermally driven shape memory material free recovery behavior testing device according to claim 1, It is characterized in that The clamp group comprises an upper clamp and a lower clamp, wherein the upper clamp is a non-pneumatic clamp, and the lower clamp is a pneumatic clamp, and the lower clamp is connected to a cylinder arranged on one side thereof.

4. The thermally driven shape memory material free recovery behavior testing device according to claim 1, It is characterized in that A connection block is provided on one side of the fixing platform, and the connection block is connected to one side of the lower clamp.

5. The thermally driven shape memory material free recovery behavior testing device according to claim 1, It is characterized in that A connecting plate is provided at one end of the lead screw slide, and the connecting plate is connected to one end of the force sensor.

6. The thermally driven shape memory material free recovery behavior testing device according to claim 1, It is characterized in that The force sensor, the fixture group and the fixing platform are all located above the lead screw slide.

7. The thermally driven shape memory material free recovery behavior testing device according to claim 1, It is characterized in that The lead screw slide is provided with a bracket on the back side thereof, a fan is provided on the bracket, at least one fan is provided, and the bracket is connected to the box body.

8. The thermally driven shape memory material free recovery behavior testing device according to claim 1, It is characterized in that A copper tube is arranged inside the box body, and the copper tube is located between the side wall of the box body and the bracket.

9. The thermally driven shape memory material free recovery behavior testing device according to claim 3 or 8, It is characterized in that It also includes solenoid valves, air pumps, high and low temperature constant temperature circulation pumps, data acquisition cards, and PC terminals; The lower fixture is connected to the solenoid valve and the air pump; The force sensor is connected to a data acquisition card, and the data acquisition card is connected to a PC terminal; The copper tube is connected to a high and low temperature constant temperature circulation pump.

10. Test method for free recovery behavior of thermally driven shape memory materials, It is characterized in that The following steps are involved: Step 1: Start the computer, open the labview software, open the code, control the motor to slowly drive the lead screw to the appropriate position, turn on the air pump, control the solenoid valve to loosen the lower clamp, clamp the two ends of the sample on the clamp group, and then control the solenoid valve to close the lower clamp. Turn on the high and low temperature constant temperature circulation pump, heat to the test temperature, keep warm, and control the motor to stretch the sample to the position where the stress is 0 according to the signal fed back by the force sensor. At this point, the preparation link is completed, and a complete shape memory cycle test is carried out without manual intervention; Step 2: A complete shape memory cycle test: The first step is to control the motor to drive the screw to stretch the sample to the specified position. The second step is to control the high and low temperature constant temperature circulation pump to cool the temperature of the environmental box and keep it warm. At this time, the temporary shape of the sample is "frozen". According to the signal feedback from the force sensor, the motor is controlled to unload the sample. Then, the solenoid valve is controlled to release the lower clamp. The sample will maintain the temporary shape and will not shrink back to the initial shape. The third step is to control the high and low temperature constant temperature circulation pump to increase the temperature of the environmental box. As the temperature changes, the sample will gradually return to its initial shape. The camera records the experimental process in real time. At this point, a complete shape memory cycle test is completed.

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