A Shape Memory Alloy Spring Testing Device and Testing Method

Abstract

The present invention discloses a shape memory alloy spring testing device and a testing method, belonging to the technical field of spring testing. The device includes a frame, a force sensor, a fixture for clamping a shape memory alloy spring, a first force loading mechanism, and a high and low temperature chamber. The fixture includes a first guide rod and a second guide rod, and a second force loading mechanism is detachably connected to the second guide rod. The present invention can perform various loadings on the shape memory alloy spring using a motor, weights, or a spring, realizing various mode tests of its characteristics, and realizing the tests of the force and deformation characteristics and temperature characteristics of the shape memory alloy compression spring and the shape memory alloy tension spring; it has a simple structure, is convenient to install, and has low manufacturing cost and use cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of spring testing, and particularly relates to a shape memory alloy spring testing device and a testing method. Background Art

[0002] Springs have many applications in modern technology, industry, and life production, such as buffering, shock absorption, energy storage, and motion control in mechanical equipment, etc. With the development of new materials and processes, the application of springs is more extensive. For example, shape memory alloy springs, due to their intrinsic shape memory characteristics, have outstanding performance advantages such as large-range recoverable deformation and returning to the initial shape, and have good application potential in many emerging high-tech industrial fields. Fully mastering various characteristics of shape memory alloy springs, such as temperature, force, and deformation ability, etc., is not only a prerequisite for the design and development of new shape memory alloy springs, but also the basis for realizing their effective control and application.

[0003] However, most of the existing spring testing equipment are independent characteristic testing equipment. For example, the tensile testing machine for testing the mechanical properties of materials is relatively expensive and generally does not have the function of simultaneously measuring temperature. Therefore, it is necessary to design a testing device to realize the measurement of the temperature-sensitive mechanical characteristics of shape memory alloy springs.

[0004] However, when measuring shape memory alloy springs, in addition to obtaining the force, deformation, and temperature characteristics of the springs, the following requirements are also needed:

[0005] (1) Shape memory alloy springs must be trained (with different loads, different temperatures, different frequencies) before they are officially put into service to make their internal structures and performances stable;

[0006] (2) For testing and evaluating the service life of shape memory alloy springs, cyclic loading tests with multiple environmental parameters (different loads, different temperatures, different frequencies) need to be carried out until their shape memory characteristics are lower than the minimum index required for service, that is, functional fatigue. The testing process takes a very long time. Directly using a tensile testing machine for testing will cause great waste of resources and generate high testing costs;

[0007] (3) It is possible to realize the testing of the force, deformation characteristics, and temperature characteristics of shape memory alloy compression springs and shape memory alloy extension springs. Summary of the Invention

[0008] Technical Problem: Aiming at the above problems existing in the prior art, the technical problem to be solved by the present invention is a shape memory alloy spring testing device and a testing method, which can realize the measurement of the temperature-sensitive mechanical characteristics of shape memory alloy springs and perform various modes of testing on the springs.

[0009] Technical solution: To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0010] A shape memory alloy spring testing device, comprising a frame, a force sensor arranged on the frame, a fixture connected to the force sensor and used for clamping a shape memory alloy spring, a first force loading mechanism detachably connected to the fixture, and a high and low temperature box for accommodating the shape memory alloy spring. The fixture includes a first guide rod connected to one end of the shape memory alloy spring and a second guide rod connected to the other end of the shape memory alloy spring. A second force loading mechanism for applying tensile or compressive force to the second guide rod is detachably connected to the second guide rod.

[0011] Further, the second force loading mechanism is a spring variable load mechanism or a weight variable load mechanism;

[0012] The spring variable load mechanism includes a second spring, a first spring seat connected to one end of the second spring, and a second spring seat connected to the other end of the second spring. The first spring seat is detachably connected to the second guide rod, and the second spring seat is detachably connected to the frame;

[0013] The weight variable load mechanism includes a weight seat and weights detachably connected to the weight seat. The weight seat is detachably connected to the second guide rod, and the number of weights is more than one.

[0014] Further, the first force loading mechanism includes a guide rail seat, a motor arranged on the guide rail seat, a lead screw connected to the motor, and a slider movably connected to the lead screw. The slider is detachably connected to the second guide rod through a connecting rod.

[0015] Further, a heating pipe, a liquid nitrogen pipe, and a first temperature sensor are arranged in the high and low temperature box. A second temperature sensor for measuring the temperature of the shape memory alloy spring is arranged on the first guide rod or the second guide rod. A distance measuring sensor is arranged on the frame, and a displacement piece corresponding to the distance measuring sensor is arranged on the second guide rod.

[0016] Further, the frame includes a first support plate, a support column connected to the first support plate, and a second support plate connected to the support column. The force sensor is arranged on the first support plate, and the guide rail seat, the motor, and the lead screw are arranged in the support column.

[0017] The present invention also provides a method for testing a shape memory alloy spring, using the above-mentioned shape memory alloy spring testing device, comprising the following steps:

[0018] S1. Connect the shape memory alloy spring to the fixture. One end of the shape memory alloy spring is connected to the first guide rod, and the other end is connected to the second guide rod.

[0019] S2. Use the first force loading mechanism or the second force loading mechanism to test the shape memory alloy spring in the motor loading mode, training mode, fatigue mode or constant strain mode.

[0020] S3. Collect the temperature T in the high and low temperature chamber, the temperature T of the shape memory alloy spring, the force F exerted by the shape memory alloy spring on the force sensor, and the displacement L of the shape memory alloy spring in each mode. c ; d ;

[0021] S4. Calculate the real-time spring constant K of the shape memory alloy spring according to the formula F = KL. d

[0022] S5. Calculate the helix angle β of the shape memory alloy spring after stretching or compressing according to the formula , where β0 is the initial helix angle of the shape memory alloy spring, L0 is the initial length of the shape memory alloy spring, the length L is the length of the shape memory alloy spring after stretching or compressing, and L = L0 + L. d ;

[0023] S6. Calculate the transverse force F', torque T' and bending moment M on a certain normal section of the shape memory alloy spring after stretching or compressing according to the formulas F' = Fcosβ and and , where D is the mean diameter of the shape memory alloy spring and F is the force exerted by the shape memory alloy spring on the force sensor.

[0024] S7. Calculate the torsional shear stress τ and on a certain normal section of the spring after stretching or compressing according to the formulas T and shear stress τ F , where d is the diameter of the spring wire of the shape memory alloy spring.

[0025] Further, in the motor loading mode in step S2, the first force loading mechanism is used to test the shape memory alloy spring, including the following steps:

[0026] S2.01. Fasten the first force loading mechanism to the second guide rod.

[0027] S2.02. Remove the second force loading mechanism from the second guide rod.

[0028] S2.03. Keep the high and low temperature chamber at a constant temperature according to the setting.

[0029] S2.04. The first force loading mechanism drives the second guiding rod to generate regular displacements according to the settings.

[0030] Furthermore, in step S2, the training mode is to use the second force loading mechanism to test the shape memory alloy spring, including the following steps:

[0031] S2.11. Separate the first force loading mechanism from the second guiding rod;

[0032] S2.12. Select the spring variable load mechanism for the second force loading mechanism and connect the spring variable load mechanism to the second guiding rod;

[0033] S2.13. The high and low temperature chamber generates regular temperature changes according to the settings, causing the shape memory alloy spring to produce a shape memory effect;

[0034] Furthermore, in step S2, the fatigue mode is to use the second force loading mechanism to test the shape memory alloy spring, including the compression spring fatigue mode and the tension spring fatigue mode.

[0035] The compression spring fatigue mode includes the following steps:

[0036] S2.21. Separate the first force loading mechanism from the second guiding rod;

[0037] S2.22. Select the weight variable load mechanism for the second force loading mechanism and connect the weight variable load mechanism to the second guiding rod. The weight variable load mechanism continuously applies pressure to the shape memory alloy spring through the second guiding rod;

[0038] S2.23. The high and low temperature chamber generates regular temperature changes according to the settings, causing the shape memory alloy spring to produce a shape memory effect;

[0039] The tension spring fatigue mode includes the following steps:

[0040] S2.31. Invert the frame;

[0041] S2.32. After inversion, separate the first force loading mechanism from the second guiding rod;

[0042] S2.33. Select the weight variable load mechanism for the second force loading mechanism and connect the weight variable load mechanism to the second guiding rod. Under the action of gravity, the weight variable load mechanism continuously applies a tensile force to the shape memory alloy spring through the second guiding rod;

[0043] S2.34. The high and low temperature chamber generates regular temperature changes according to the settings, causing the shape memory alloy spring to produce a shape memory effect.

[0044] Further, in the step S2, the constant strain mode is to test the shape memory alloy spring by using the first force loading mechanism, including the following steps:

[0045] S2.41. Fasten the first force loading mechanism to the second guide rod;

[0046] S2.42. Remove the second force loading mechanism from the second guide rod;

[0047] S2.43. After the first force loading mechanism drives the second guide rod to displace, keep the position unchanged;

[0048] S2.44. The high and low temperature chamber generates regular temperature changes according to the setting, so that the shape memory alloy spring generates a shape memory effect.

[0049] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0050] 1. By setting two groups of force loading mechanisms detachably connected to the fixture, and the second force loading mechanism can choose to use a spring variable load mechanism or a weight variable load mechanism, so that a motor, weights or springs can be used to perform multiple loadings on the shape memory alloy spring, and multiple mode tests on its characteristics are realized through the test method of the present invention, including the motor loading mode, the training mode, the fatigue mode and the constant strain mode;

[0051] The motor loading mode can test the relationship characteristics between the displacement and force of the shape memory alloy spring at a constant temperature;

[0052] The test method of the training mode can make the shape memory alloy spring undergo training under different loads, different temperatures and different frequencies before it is officially put into service, so as to improve the stability of its internal structure and performance;

[0053] The fatigue mode can perform cyclic loading on the shape memory alloy spring in a pulling or pressing manner under multiple environmental parameters (different loads, different temperatures, different frequencies) to test the service life;

[0054] The constant strain mode can detect the relationship characteristics between the temperature and force of the shape memory alloy spring when maintaining a constant strain;

[0055] Through the test of the shape memory alloy spring by this device, the temperature T in the high and low temperature chamber c , the temperature T of the shape memory alloy spring, the force F exerted by the shape memory alloy spring on the force sensor, and the displacement L of the shape memory alloy spring can be obtained d . Then, through formula calculation, the real-time spring constant K, torsional shear stress τ T and shear stress τ F, the stress-strain and temperature characteristic relationship of the shape memory alloy spring can be finally obtained;

[0056] 2. By selecting two sets of force loading mechanisms and cooperating with a high and low temperature chamber, the fixture is connected to the shape memory alloy spring. The two sets of force loading mechanisms can apply tensile or compressive forces to the tested shape memory alloy spring, which can be either for extension springs (tension springs) or compression springs (compression springs), so as to realize the tests on the force, deformation characteristics and temperature characteristics of the shape memory alloy compression spring and the shape memory alloy extension spring;

[0057] 3. It can not only passively test the force generated by the spring, but also actively affect the spring with an active force. Therefore, it can test shape memory alloy spring drivers, sensors and other similar objects, with a wide range of applications;

[0058] 4. Use heating tubes and liquid nitrogen for heating and cooling, with a large temperature control range;

[0059] 5. The structure is simple, easy to install, with low manufacturing and usage costs. Only by reversing the device, the tests on extension springs and compression springs can be completed without extensive modification, saving space. Description of the Drawings

[0060] Figure 1 is a schematic structural view of the present invention;

[0061] Figure 2 is a schematic structural view of the spring variable load mechanism;

[0062] Figure 3 is a schematic structural view of the fixture;

[0063] Figure 4 is a schematic structural view when the second force loading mechanism adopts a weight variable load mechanism;

[0064] Figure 5 is a schematic structural view of the weight variable load mechanism;

[0065] Figure 6 is a schematic structural view of the inverted present invention in the fatigue mode of the extension spring;

[0066] Figure 7 is a schematic three-dimensional structural view of Embodiment 6 of the present invention.

[0067] In the figure, 1 is the frame; 2 is the force sensor; 3 is the fixture; 4 is the first force loading mechanism; 5 is the high and low temperature chamber; 6 is the second force loading mechanism; 7 is the distance measuring sensor; 9 is the shape memory alloy spring; 11 is the first support plate; 12 is the support column; 13 is the second support plate; 14 is the foot; 31 is the first guide rod; 32 is the second guide rod; 33 is the guide mandrel; 311 is the first locking bolt; 321 is the second locking bolt; 44 is the slider; 45 is the connecting rod; 46 is the fixed sleeve; 47 is the third locking bolt; 51 is the heating pipe; 52 is the first temperature sensor; 53 is the second temperature sensor; 54 is the box body; 55 is the door body; 56 is the liquid nitrogen pipe; 61 is the second spring; 62 is the first spring seat; 621 is the first bolt pin; 63 is the second spring seat; 631 is the second bolt pin; 64 is the weight seat; 641 is the threaded column; 65 is the weight; 71 is the displacement piece. Detailed implementation mode

[0068] The following will further clarify the present invention in combination with specific embodiments. The embodiments are implemented on the premise of the technical solution of the present invention. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0069] Embodiment 1

[0070] As Figure 1 and Figure 3As shown in the figure, a shape memory alloy spring testing device includes a frame 1, a force sensor 2, a fixture 3, a first force loading mechanism 4, a high and low temperature chamber 5, a second force loading mechanism 6, and a ranging sensor 7. The frame 1 includes a first support plate 11, a support column 12, and a second support plate 13. Both the first support plate 11 and the second support plate 13 are horizontally arranged flat plates. The support column 12 is vertically arranged between the first support plate 11 and the second support plate 13. The first support plate 11 is connected to the lower end of the support column 12 as the bottom plate, and the second support plate 13 is connected to the upper end of the support column 12 as the top plate. The force sensor 2 is an S-type force sensor. The lower end of the force sensor 2 is connected to the first support plate 11, and the fixture 3 is connected to the upper end of the force sensor 2. The fixture 3 is used to clamp the shape memory alloy spring 9 to be tested. The shape memory alloy spring 9 is a helical spring, with a first vertical section extending vertically upward at the upper end and a second vertical section extending vertically downward at the lower end. The fixture 3 includes a first guide rod 31, a second guide rod 32, and a guide mandrel 33. The first guide rod 31 is provided with a first jack corresponding to the first vertical section of the shape memory alloy spring 9, and the first guide rod 31 is also provided with a first locking bolt 311 for locking the first vertical section of the shape memory alloy spring 9. The second guide rod 32 is provided with a second jack corresponding to the second vertical section of the shape memory alloy spring 9, and the second guide rod 32 is also provided with a second locking bolt 321 for locking the second vertical section of the shape memory alloy spring 9. When the first locking bolt 311 and the second locking bolt 321 are tightened, the fixture 3 clamps and fixes the shape memory alloy spring 9 (the fixture 3 can also use other existing fixtures or methods to fix the shape memory alloy spring 9). The guide mandrel 33 is cylindrical and passes through the shape memory alloy spring 9 from the middle hole of the shape memory alloy spring 9. The first guide rod 31 is provided with a first receiving groove corresponding to the guide mandrel 33, and the second guide rod 32 is provided with a second receiving groove corresponding to the guide mandrel 33. The guide mandrel 33 has a clearance fit with both the first guide rod 31 and the second guide rod 32. Thus, when the second guide rod 32 moves up and down, it will not drive the guide mandrel 33 to move, and the guide mandrel 33 plays a guiding role.

[0071] As Figure 1As shown, the first force loading mechanism 4 is detachably connected to the second guide rod 32 of the fixture 3. The first force loading mechanism 4 adopts a single-axis slide. The first force loading mechanism 4 includes a guide rail base, a motor, a lead screw, and a slider 44. The guide rail base, the motor, and the lead screw are all arranged inside the support column 12. The motor is arranged at one end of the guide rail base. The lead screw is arranged on the guide rail base and connected to the motor. The slider 44 is movably connected to the lead screw and extends outward to be movably connected to the support column 12. The first force loading mechanism 4 is vertically arranged. Driven by the motor, the slider 44 slides up and down along the support column 12. The slider 44 is detachably connected to the second guide rod 32 through a connecting rod 45. A fixing sleeve 46 is arranged on the connecting rod 45. A third locking bolt 47 is arranged on the fixing sleeve 46. The fixing sleeve 46 is sleeved on the second guide rod 32. By tightening the third locking bolt 47, the connecting rod 45 can be fixed to the second guide rod 32. After fixing, the up and down movement of the slider 44 can drive the second guide rod 32 to move up and down.

[0072] As Figure 1 and Figure 3 shown, the high and low temperature box 5 houses the shape memory alloy spring 9. The high and low temperature box 5 includes a box body 54 and a door body 55. The lower end of the box body 54 is connected to the first support plate 11 of the frame 1 through a plurality of support feet 14. The door body 55 is arranged on one side of the door body 55, which is convenient to open from the side. A first notch corresponding to the first guide rod 31 is arranged on the bottom plate of the box body 54. A first retaining piece is inserted at the first notch. A second notch corresponding to the second guide rod 32 is arranged on the top plate of the box body 54. A second retaining piece is inserted at the second notch. During use, open the door body 55, move the box body 54 from the side towards the shape memory alloy spring 9. The first notch houses the first guide rod 31, and the second notch houses the second guide rod 32. Then insert the first retaining piece into the first notch and the second retaining piece into the second notch, which can block the excess part after the two notches house the two guide rods. Close the door body 55, and the shape memory alloy spring 9 can be housed in the box. Then connect the box body 54 and the plurality of support feet 14 through bolts. Since there is a gap between the first notch and the first guide rod 31, and a gap between the second notch and the second guide rod 32, the high and low temperature box 5 does not affect the movement of the first guide rod 31 and the second guide rod 32. A heating tube 51, a liquid nitrogen tube 56, and a first temperature sensor 52 are arranged inside the high and low temperature box 5. A second temperature sensor 53 is arranged on the first guide rod 31. The heating tube 51 is used to heat the temperature inside the high and low temperature box 5. The liquid nitrogen tube 56 is used to connect to an external liquid nitrogen pipeline to cool the inside of the high and low temperature box 5. The first temperature sensor 52 is used to detect the temperature inside the box. The second temperature sensor 53 is in contact with the shape memory alloy spring 9 to measure the temperature of the shape memory alloy spring 9.

[0073] As Figure 1 、 Figure 2 、 Figure 4 and Figure 5As shown, a second force loading mechanism 6 for applying tensile or compressive force to the second guiding rod 32 is detachably connected to the second guiding rod 32. The second force loading mechanism 6 is a spring variable load mechanism or a weight variable load mechanism. As Figure 1 and Figure 2 shown, the spring variable load mechanism includes a second spring 61, a first spring seat 62, and a second spring seat 63. The second spring 61 is a tension spring with hooks at both ends. The first spring seat 62 is detachably connected to the second guiding rod 32, and the detachable connection method is threaded connection. The second spring seat 63 is also detachably connected to the second support plate 13 of the frame 1 by a threaded connection method. A first pin 621 is provided on the first spring seat 62, and the lower end of the second spring 61 is connected to the first spring seat 62 through the first pin 621. A second pin 631 is provided on the second spring seat 63, and the upper end of the second spring 61 is connected to the second spring seat 63 through the second pin 631. As Figure 4 and Figure 5 shown, the weight variable load mechanism includes a weight seat 64 and weights 65. A threaded post 641 is provided on the weight seat 64. The weight seat 64 is detachably connected to the second guiding rod 32 through the threaded post 641. The weight and quantity of the weights 65 can be selected according to needs. The weights 65 are threadedly connected to the threaded post 641 and thus detachably connected to the weight seat 64.

[0074] A distance measuring sensor 7 is provided on the frame 1. The distance measuring sensor 7 is a laser distance measuring sensor. A displacement piece 71 corresponding to the distance measuring sensor 7 is provided on the second guiding rod 32. The displacement distance is measured by the distance measuring sensor 7 sensing the movement of the displacement piece 71.

[0075] This embodiment also discloses a method for testing a shape memory alloy spring. Using the above-mentioned shape memory alloy spring testing device, the shape memory alloy spring 9 is tested. The shape memory alloy spring 9 can be either a tension spring or a compression spring. The method includes the following steps:

[0076] S1. Connect the shape memory alloy spring 9 to the fixture 3. The lower end of the shape memory alloy spring 9 is connected to the first guiding rod 31 and locked by the first locking bolt 311, and the upper end is connected to the second guiding rod 32 and locked by the second locking bolt 321.

[0077] S2. Use the first force loading mechanism 4 to test the shape memory alloy spring 9 in the motor loading mode, specifically including:

[0078] S2.01. Connect the first force loading mechanism 4 tightly to the second guiding rod 32, that is, tighten the third locking bolt 47 to connect the fixed sleeve 46 to the second guiding rod 32;

[0079] S2.02. Remove the second force loading mechanism 6 from the second guiding rod 32;

[0080] S2.03. The high and low temperature chamber 5 is maintained at a constant temperature according to the setting, such as room temperature of 25 °C.

[0081] S2.04. The first force loading mechanism 4 drives the second guide rod 32 to generate regular displacements according to the setting. The slider 44 drives the fixed sleeve 46, the fixed sleeve 46 drives the second guide rod 32, and the second guide rod 32 drives the shape memory alloy spring 9. The up and down movement of the slider 44 can apply tensile or compressive forces to the shape memory alloy spring 9.

[0082] S3. Collect the temperature T inside the high and low temperature chamber 5 c , the temperature T of the shape memory alloy spring 9, the force F exerted by the shape memory alloy spring 9 on the force sensor 2, and the displacement L of the shape memory alloy spring 9 d ; The first temperature sensor 52 collects the temperature T inside the high and low temperature chamber 5 c , the second temperature sensor 53 collects the temperature T of the shape memory alloy spring 9, and the distance measuring sensor 7 collects the displacement L through the displacement piece 71 d .

[0083] S4. According to the formula F = KL d , calculate the real-time spring constant K of the shape memory alloy spring 9.

[0084] S5. According to the formula calculate the helix angle β of the shape memory alloy spring 9 after stretching or compression, where β0 is the initial helix angle of the shape memory alloy spring 9, where L0 is the initial length of the shape memory alloy spring 9, the length L is the length of the shape memory alloy spring 9 after stretching or compression, and L = L0 + L d .

[0085] S6. According to the formulas F' = Fcosβ and and calculate the transverse force F', torque T', and bending moment M on a certain normal section of the shape memory alloy spring 9 after stretching or compression, where D is the mean diameter of the shape memory alloy spring 9, and F is the force exerted by the shape memory alloy spring 9 on the force sensor 2.

[0086] S7. According to the formulas and the torsional shear stress τ on a certain normal section of the spring after stretching or compression can be calculated T and the shear stress τ F , where d is the wire diameter of the shape memory alloy spring 9.

[0087] Example 2

[0088] The shape memory alloy spring testing device of this embodiment is the same as that of Embodiment 1. Meanwhile, a method for testing a shape memory alloy spring is disclosed. Using the above-mentioned shape memory alloy spring testing device, the shape memory alloy spring 9 is tested. The shape memory alloy spring 9 can be either a tension spring or a compression spring, and the method includes the following steps:

[0089] S1. Connect the shape memory alloy spring 9 to the fixture 3. The lower end of the shape memory alloy spring 9 is connected to the first guide rod 31 and locked by the first locking bolt 311, and the upper end is connected to the second guide rod 32 and locked by the second locking bolt 321.

[0090] S2. Use the second force loading mechanism 6 to test the shape memory alloy spring 9 in the training mode, which specifically includes the following steps:

[0091] S2.11. Separate the first force loading mechanism 4 from the second guide rod 32, that is, loosen the third locking bolt 47;

[0092] S2.12. Select the spring variable load mechanism for the second force loading mechanism 6, and connect the spring variable load mechanism to the second guide rod 32. As Figure 1 shown, the first spring seat 62 is threadedly connected to the upper end of the second guide rod 32, the second spring seat 63 is threadedly connected to the second support plate 13, and the second spring 61 is connected between the first spring seat 62 and the second spring seat 63. The second spring 61 uses a common tension spring or compression spring to apply a tensile force or a compressive force to the shape memory alloy spring 9;

[0093] S2.13. The high and low temperature chamber 5 generates a regular temperature change according to the setting. The heating tube 51 is used for heating, and the liquid nitrogen tube 56 is used for introducing liquid nitrogen to cool down, so that the shape memory alloy spring 9 generates a shape memory effect. The temperature can be set according to the phase change temperature and various characteristics of the shape memory alloy spring 9, and the number of operating times of the temperature change is set according to needs.

[0094] S3. Collect the temperature T c inside the high and low temperature chamber 5, the temperature T of the shape memory alloy spring 9, the force F exerted by the shape memory alloy spring 9 on the force sensor 2, and the displacement L of the shape memory alloy spring 9 d ; The first temperature sensor 52 collects the temperature T c inside the high and low temperature chamber 5, the second temperature sensor 53 collects the temperature T of the shape memory alloy spring 9, and the distance measuring sensor 7 collects the displacement L through the displacement piece 71 d .

[0095] S4. According to the formula F = KL d , calculate the real-time spring constant K of the shape memory alloy spring 9.

[0096] S5. According to the formula Calculate the helix angle β after stretching or compressing the shape memory alloy spring 9, where β0 is the initial helix angle of the shape memory alloy spring 9. Here, L0 is the initial length of the shape memory alloy spring 9, and the length L is the length of the shape memory alloy spring 9 after stretching or compressing, and L = L0 + L d 。

[0097] S6. According to the formula F' = Fcosβ and and calculate the transverse force F', torque T', and bending moment M on a certain normal section of the shape memory alloy spring 9 after stretching or compressing, where D is the mean diameter of the shape memory alloy spring 9, and F is the force exerted by the shape memory alloy spring 9 on the force sensor 2.

[0098] S7. According to the formula and the torsional shear stress τ on a certain normal section of the spring after stretching or compressing can be calculated T and the shear stress τ F , where d is the wire diameter of the shape memory alloy spring 9.

[0099] Example 3

[0100] The shape memory alloy spring testing device in this example is the same as that in Example 1. At the same time, a shape memory alloy spring testing method is disclosed. Using the above-mentioned shape memory alloy spring testing device to test the shape memory alloy spring 9, the shape memory alloy spring 9 is a compression spring, and the method includes the following steps:

[0101] S1. Connect the shape memory alloy spring 9 to the fixture 3. The lower end of the shape memory alloy spring 9 is connected to the first guide rod 31 and locked by the first locking bolt 311, and the upper end is connected to the second guide rod 32 and locked by the second locking bolt 321.

[0102] S2. Use the second force loading mechanism 6 to test the shape memory alloy spring 9 in the fatigue mode. The fatigue mode is the compression spring fatigue mode, and the compression spring fatigue mode specifically includes the following steps:

[0103] S2.21. Separate the first force loading mechanism 4 from the second guide rod 32, that is, loosen the third locking bolt 47;

[0104] S2.22. The second force loading mechanism 6 selects the weight variable load mechanism and connects the weight variable load mechanism to the second guide rod 32, as Figure 4As shown, the weight seat 64 is threadedly connected to the second guide rod 32, and the weight 65 is threadedly connected to the weight seat 64. The weight and quantity of the weight 65 are selected according to requirements. The weight variable load mechanism continuously applies pressure to the shape memory alloy spring 9 through the second guide rod 32;

[0105] S2.23. The high and low temperature chamber 5 generates regular temperature changes according to the setting. The heating tube 51 is used for heating, and the liquid nitrogen tube 56 is used for introducing liquid nitrogen to cool down, so that the shape memory alloy spring 9 generates a shape memory effect. The temperature can be set according to the phase change temperature and various characteristics of the shape memory alloy spring 9, and the number of operating times of the temperature change is set according to requirements.

[0106] S3. Collect the temperature T inside the high and low temperature chamber 5 c , the temperature T of the shape memory alloy spring 9, the force F exerted by the shape memory alloy spring 9 on the force sensor 2, and the displacement L of the shape memory alloy spring 9 d ; The first temperature sensor 52 collects the temperature T inside the high and low temperature chamber 5 c , the second temperature sensor 53 collects the temperature T of the shape memory alloy spring 9, and the distance measuring sensor 7 collects the displacement L through the displacement piece 71 d .

[0107] S4. According to the formula F = KL d , calculate the real-time spring constant K of the shape memory alloy spring 9.

[0108] S5. According to the formula calculate the helix angle β of the shape memory alloy spring 9 after compression, where β0 is the initial helix angle of the shape memory alloy spring 9, where L0 is the initial length of the shape memory alloy spring 9, and the length L is the length of the shape memory alloy spring 9 after compression, L = L0 + L d .

[0109] S6. According to the formulas F' = Fcosβ and and calculate the transverse force F', torque T', and bending moment M on a certain normal section of the shape memory alloy spring 9 after compression, where D is the mean diameter of the shape memory alloy spring 9, and F is the force exerted by the shape memory alloy spring 9 on the force sensor 2.

[0110] S7. According to the formulas and the torsional shear stress τ T and shear stress τ F on a certain normal section of the compressed spring can be calculated, where d is the wire diameter of the shape memory alloy spring 9.

[0111] Example 4

[0112] The shape memory alloy spring testing device of this embodiment is the same as that of Embodiment 1. At the same time, a method for testing a shape memory alloy spring is disclosed. Using the above-mentioned shape memory alloy spring testing device to test the shape memory alloy spring 9, the shape memory alloy spring 9 is a tension spring, and the method includes the following steps:

[0113] S1. Connect the shape memory alloy spring 9 to the fixture 3. The lower end of the shape memory alloy spring 9 is connected to the first guide rod 31 and locked by the first locking bolt 311, and the upper end is connected to the second guide rod 32 and locked by the second locking bolt 321.

[0114] S2. Use the second force loading mechanism 6 to test the shape memory alloy spring 9 in the fatigue mode. The fatigue mode is the tension spring fatigue mode, and the tension spring fatigue mode specifically includes the following steps:

[0115] S2.31. Invert the frame 1 as shown in Figure 6 so that the second support plate 13 is located below and used as the bottom plate.

[0116] S2.32. After inversion, separate the first force loading mechanism 4 from the second guide rod 32, that is, loosen the third locking bolt 47.

[0117] S2.33. Select the weight variable load mechanism for the second force loading mechanism 6. Connect the weight variable load mechanism to the second guide rod 32. The weight seat 64 is threadedly connected to the second guide rod 32, and the weight 65 is threadedly connected to the weight seat 64. The weight and quantity of the weight 65 are selected according to needs. Under the action of gravity, the weight 65 continuously applies a tensile force to the shape memory alloy spring 9 through the second guide rod 32.

[0118] S2.34. The high and low temperature chamber 5 generates a regular temperature change according to the setting. The heating tube 51 is used for heating, and the liquid nitrogen tube 56 is used for introducing liquid nitrogen to cool down, so that the shape memory alloy spring 9 generates a shape memory effect. The temperature can be set according to the phase change temperature and various characteristics of the shape memory alloy spring 9, and the number of operating times of the temperature change is set according to needs.

[0119] S3. Collect the temperature T in the high and low temperature chamber 5 c , the temperature T of the shape memory alloy spring 9, the force F exerted by the shape memory alloy spring 9 on the force sensor 2, and the displacement L of the shape memory alloy spring 9 d ; The first temperature sensor 52 collects the temperature T in the high and low temperature chamber 5 c , the second temperature sensor 53 collects the temperature T of the shape memory alloy spring 9, and the distance measuring sensor 7 collects the displacement L through the displacement piece 71 d .

[0120] S4. According to the formula F = KL d, calculate the real-time spring constant K of the shape memory alloy spring 9.

[0121] S5. According to the formula calculate the helix angle β after the shape memory alloy spring 9 is stretched, where β0 is the initial helix angle of the shape memory alloy spring 9, L0 is the initial length of the shape memory alloy spring 9, the length L is the length of the shape memory alloy spring 9 after stretching, and L = L0 + L d .

[0122] S6. According to the formulas F' = Fcosβ and and calculate the transverse force F', torque T' and bending moment M on a certain normal section of the shape memory alloy spring 9 after stretching, where D is the mean diameter of the shape memory alloy spring 9, and F is the force exerted by the shape memory alloy spring 9 on the force sensor 2.

[0123] S7. According to the formulas and the torsional shear stress τ and shear stress τ on a certain normal section of the spring after stretching can be calculated T and shear stress τ F , where d is the wire diameter of the shape memory alloy spring 9.

[0124] Example 5

[0125] The shape memory alloy spring testing device in this example is the same as that in Example 1. At the same time, a shape memory alloy spring testing method is disclosed. Using the above-mentioned shape memory alloy spring testing device to test the shape memory alloy spring 9, the shape memory alloy spring 9 can be either a tension spring or a compression spring, including the following steps:

[0126] S1. Connect the shape memory alloy spring 9 to the fixture 3. The lower end of the shape memory alloy spring 9 is connected to the first guide rod 31 and locked by the first locking bolt 311, and the upper end is connected to the second guide rod 32 and locked by the second locking bolt 321.

[0127] S2. Use the first force loading mechanism 4 to test the shape memory alloy spring 9 in a constant strain mode. The constant strain mode specifically includes the following steps:

[0128] S2.41. Connect the first force loading mechanism 4 to the second guide rod 32 tightly, that is, tighten the third locking bolt 47 to connect the fixed sleeve 46 to the second guide rod 32;

[0129] S2.42. Remove the second force loading mechanism 6 from the second guide rod 32;

[0130] S2.43. After the first force loading mechanism 4 drives the second guide rod 32 to generate displacement, its position remains unchanged. The slider 44 drives the fixed sleeve 46, the fixed sleeve 46 drives the second guide rod 32, the second guide rod 32 drives the shape memory alloy spring 9, and the slider 44 moves to a position and then remains unchanged.

[0131] S2.44. The high and low temperature chamber 5 generates regular temperature changes according to the setting. The heating tube 51 is used for heating, and the liquid nitrogen tube 56 is used for introducing liquid nitrogen to cool down, so that the shape memory alloy spring 9 generates a shape memory effect. The temperature can be set according to the phase change temperature and various characteristics of the shape memory alloy spring 9, and the number of operating times of the temperature change is set according to needs.

[0132] S3. Collect the temperature T inside the high and low temperature chamber 5 c , the temperature T of the shape memory alloy spring 9, the force F exerted by the shape memory alloy spring 9 on the force sensor 2, and the displacement L of the shape memory alloy spring 9 d ; The first temperature sensor 52 collects the temperature T inside the high and low temperature chamber 5 c , the second temperature sensor 53 collects the temperature T of the shape memory alloy spring 9, and the ranging sensor 7 collects the displacement L through the displacement piece 71 d .

[0133] S4. According to the formula F = KL d , calculate the real-time spring constant K of the shape memory alloy spring 9.

[0134] S5. According to the formula calculate the helix angle β of the shape memory alloy spring 9 after stretching or compressing, where β0 is the initial helix angle of the shape memory alloy spring 9, where L0 is the initial length of the shape memory alloy spring 9, the length L is the length of the shape memory alloy spring 9 after stretching or compressing, and L = L0 + L d .

[0135] S6. According to the formulas F' = F cosβ and and calculate the transverse force F', torque T' and bending moment M on a certain normal section of the shape memory alloy spring 9 after stretching or compressing, where D is the mean diameter of the shape memory alloy spring 9, and F is the force exerted by the shape memory alloy spring 9 on the force sensor 2.

[0136] S7. According to the formulas and the torsional shear stress τ T and shear stress τ F on a certain normal section of the spring after stretching or compressing can be calculated, where d is the wire diameter of the shape memory alloy spring 9.

[0137] Example 6

[0138] As Figure 7 shown, the difference from Embodiment 1 is that the high and low temperature chamber 5 is not connected to the frame 1. The high and low temperature chamber 5 is supported by the connecting column 57 of an external bracket. The external bracket (not shown in the figure) can drive the high and low temperature chamber 5 to move up and down and back and forth. When the high and low temperature chamber 5 is needed, it is moved to a designated position through the external bracket, so as to accommodate the shape memory alloy spring 9. Two retaining pieces are inserted at the two notches, and then the door body 55 is closed. The high and low temperature chamber 5 is set to be movable for easy removal when not in use.

[0139] The devices in the six embodiments can not only passively test the force generated by the spring, but also exert an active force on the spring. Therefore, this device can test shape memory alloy spring actuators and sensors and other similar objects. A shape memory alloy spring actuator refers to a spring that can act as an actuator to exert an active force on other objects when its temperature or length changes; A shape memory alloy spring sensor refers to a sensor that can know the magnitude of the active force or the change in temperature by measuring the change in the length of the spring when an active force is exerted on the shape memory alloy spring by other objects or when the temperature changes.

[0140] The above is only the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for testing a shape memory alloy spring, which uses a testing device for a shape memory alloy spring, is characterized in that The test device includes a frame (1), a force sensor (2) arranged on the frame (1), a fixture (3) connected to the force sensor (2) and used for clamping a shape memory alloy spring (9), a first force loading mechanism (4) detachably connected to the fixture (3), and a high and low temperature chamber (5) for accommodating the shape memory alloy spring (9). The fixture (3) includes a first guide rod (31) connected to one end of the shape memory alloy spring (9) and a second guide rod (32) connected to the other end of the shape memory alloy spring (9). A second force loading mechanism (6) for applying a tensile force or a compressive force to the second guide rod (32) is detachably connected to the second guide rod (32). The second force loading mechanism (6) is a spring variable load mechanism or a weight variable load mechanism; The spring variable load mechanism includes a second spring (61), a first spring seat (62) connected to one end of the second spring (61), and a second spring seat (63) connected to the other end of the second spring (61). The first spring seat (62) is detachably connected to the second guide rod (32), and the second spring seat (63) is detachably connected to the frame (1); The weight variable load mechanism includes a weight seat (64) and weights (65) detachably connected to the weight seat (64). The weight seat (64) is detachably connected to the second guide rod (32), and the number of the weights (65) is more than one; The test method includes the following steps: S1. Connect the shape memory alloy spring (9) to the fixture (3). One end of the shape memory alloy spring (9) is connected to the first guide rod (31), and the other end is connected to the second guide rod (32); S2. Use the first force loading mechanism (4) or the second force loading mechanism (6) to test the shape memory alloy spring (9) in a motor loading mode, a training mode, a fatigue mode or a constant strain mode; S3. Collect the temperature T inside the high and low temperature chamber (5) in each mode c , the temperature T of the shape memory alloy spring (9), the force F exerted by the shape memory alloy spring (9) on the force sensor (2), and the displacement L of the shape memory alloy spring (9) d ; S4. Calculate the real-time spring constant K of the shape memory alloy spring (9) according to the formula F = KL d , where S5. According to the formula calculate the helix angle β after the shape memory alloy spring (9) is stretched or compressed, where β0 is the initial helix angle of the shape memory alloy spring (9), L0 is the initial length of the shape memory alloy spring (9), the length L is the length of the shape memory alloy spring (9) after being stretched or compressed, and L = L0 + L d ; S6. According to the formula F' = Fcosβ and and calculate the transverse force F', torque T' and bending moment M on a certain normal section of the shape memory alloy spring (9) after stretching or compression, where D is the mean diameter of the shape memory alloy spring (9), and F is the force exerted by the shape memory alloy spring (9) on the force sensor (2); S7. According to the formula and the torsional shear stress τ T and shear stress τ F acting on a certain normal section of the spring after stretching or compression can be calculated, where d is the wire diameter of the shape memory alloy spring (9).

2. The shape memory alloy spring testing method according to claim 1, characterized in that The first force loading mechanism (4) includes a guide rail seat, a motor arranged on the guide rail seat, a lead screw connected to the motor, and a slider (44) movably connected to the lead screw. The slider (44) is detachably connected to the second guide rod (32) through a connecting rod (45).

3. The shape memory alloy spring testing method according to claim 2, characterized in that The high and low temperature chamber (5) is provided with a heating pipe (51), a liquid nitrogen pipe (56) and a first temperature sensor (52). A second temperature sensor (53) for measuring the temperature of the shape memory alloy spring (9) is arranged on the first guide rod (31) or the second guide rod (32). A distance measuring sensor (7) is arranged on the frame (1), and a displacement piece (71) corresponding to the distance measuring sensor (7) is arranged on the second guide rod (32).

4. The shape memory alloy spring testing method according to claim 2, wherein The frame (1) includes a first support plate (11), a support column (12) connected to the first support plate (11), and a second support plate (13) connected to the support column (12). The force sensor (2) is arranged on the first support plate (11), and the guide rail seat, the motor and the lead screw are arranged in the support column (12).

5. The shape memory alloy spring testing method according to claim 1, wherein In the step S2, the motor loading mode is to test the shape memory alloy spring (9) by using the first force loading mechanism (4), including the following steps: S2.

01. Fasten the first force loading mechanism (4) to the second guide rod (32). S2.

02. Remove the second force loading mechanism (6) from the second guide rod (32). S2.

03. Keep the high and low temperature chamber (5) at a constant temperature according to the setting. S2.

04. The first force loading mechanism (4) drives the second guide rod (32) to generate regular displacements according to the setting.

6. The shape memory alloy spring testing method according to claim 1, wherein In the step S2, the training mode is to test the shape memory alloy spring (9) by using the second force loading mechanism (6), including the following steps: S2.

11. Separate the first force loading mechanism (4) from the second guide rod (32). S2.

12. Select the spring variable load mechanism for the second force loading mechanism (6), and connect the spring variable load mechanism to the second guide rod (32). S2.

13. The high and low temperature chamber (5) generates regular temperature changes according to the setting, so that the shape memory alloy spring (9) produces the shape memory effect.

7. The shape memory alloy spring testing method according to claim 1, characterized in that In the step S2, the fatigue mode is to test the shape memory alloy spring (9) by using the second force loading mechanism (6), including the compression spring fatigue mode and the tension spring fatigue mode. The compression spring fatigue mode includes the following steps: S2.

21. Separate the first force loading mechanism (4) from the second guide rod (32). S2.

22. Select the weight variable load mechanism for the second force loading mechanism (6), connect the weight variable load mechanism to the second guide rod (32), and the weight variable load mechanism continuously applies pressure to the shape memory alloy spring (9) through the second guide rod (32). S2.

23. The high and low temperature chamber (5) generates regular temperature changes according to the setting, so that the shape memory alloy spring (9) produces the shape memory effect. The tension spring fatigue mode includes the following steps: S2.

31. Invert the frame (1). S2.

32. After inversion, separate the first force loading mechanism (4) from the second guide rod (32). S2.

33. Select the weight variable load mechanism for the second force loading mechanism (6), connect the weight variable load mechanism to the second guide rod (32), and under the action of gravity, the weight variable load mechanism continuously applies tension to the shape memory alloy spring (9) through the second guide rod (32). S2.

34. The high and low temperature chamber (5) generates regular temperature changes according to the setting, so that the shape memory alloy spring (9) produces the shape memory effect.

8. The shape memory alloy spring testing method according to claim 1, characterized in that In the step S2, the constant strain mode is to test the shape memory alloy spring (9) by using the first force loading mechanism (4), including the following steps: S2.

41. Fasten the first force loading mechanism (4) to the second guide rod (32). S2.

42. Remove the second force loading mechanism (6) from the second guide rod (32). S2.

43. After the first force loading mechanism (4) drives the second guide rod (32) to generate a displacement, keep the position unchanged. S2.

44. The high and low temperature chamber (5) generates regular temperature changes according to the setting, so that the shape memory alloy spring (9) produces the shape memory effect.

Images