Second-order stiffness suspension spring static and dynamic and fatigue performance research method

Abstract

The invention provides a second-order stiffness suspension spring static and dynamic and fatigue performance research method, and relates to the technical field of automobile suspension spring research, the second-order stiffness suspension spring static and dynamic and fatigue performance research method comprises a fixed support plate and a positioning support plate, the middle position of the fixed support plate is provided with a driving cylinder, and the top edge position of the fixed support plate is provided with a support vertical plate; a positioning pipe is mounted at the bottom of the positioning supporting plate; the output end of the driving cylinder in the middle of the fixed carrier plate is inserted into the positioning pipe; a connecting plate is mounted on the outer side of the fixed carrier plate; a fixed protective cover is installed at the outer end of the connecting plate, a protective net is arranged on the side face of the fixed protective cover, a pressing plate and a positioning supporting plate are used for clamping the suspension spring, static or dynamic fatigue performance tests are conducted on the suspension spring, and then the fatigue life of the suspension spring is designed. The problems that research on the mechanical property of the second-order rigidity suspension spring is not comprehensive, and the number of research literatures capable of being referred to in the aspect of fatigue life mechanical property is small are solved.

Description

Technical Field

[0001] The invention relates to the technical field of automobile suspension spring research, and in particular to a method for researching static, dynamic and fatigue performances of a second-order stiffness suspension spring. Background Art

[0002] Suspension springs are important components of the automobile chassis system. Together with shock absorbers, they bear the vehicle system and load mass, absorb vehicle driving vibrations, and improve ride comfort. The suspension spring product design must meet mechanical properties such as strength, stiffness, natural frequency, permanent deformation, stability, and fatigue durability.

[0003] If a car has different loads or is driving on different roads, if a small stiffness spring design is used, it can only meet the riding comfort when the car is lightly loaded or driving on good roads. When the car is heavily loaded or driving on bad roads, the deformation will increase, causing the spring to be compressed and lose its shock absorbing effect. At this time, it is hoped that the spring stiffness will be larger, so a spring with variable diameter and pitch is produced, which can meet the requirements of light and heavy load spring stiffness at the same time.

[0004] The suspension spring involved in the present invention is a two-pitch cylindrical helical compression spring. As the load increases, the spring tightens from a small pitch to a large pitch, the stiffness increases, an inflection point appears on the stiffness characteristic line, and the characteristic line changes from a constant stiffness to a second-order stiffness.

[0005] At present, the research on the mechanical properties of second-order stiffness suspension springs is not comprehensive, and mostly stays in the aspects of static strength, static stiffness, and modal analysis. There are few reference research literatures on the stability, permanent deformation, and fatigue life mechanical properties of the springs. In particular, the stress of the second-order stiffness suspension spring changes nonlinearly within the entire load range. For this reason, the present invention needs to study the static, dynamic and fatigue properties of the second-order stiffness suspension spring, and perform a reasonable fatigue life design for the second-order stiffness suspension spring. Summary of the invention

[0006] The disclosed embodiment relates to a method for studying the static, dynamic and fatigue properties of a second-order stiffness suspension spring, wherein the output end of a driving cylinder on a fixed carrier plate is inserted into a positioning tube to position the positioning pallet, and the positioning pallet can be positioned so that the positioning pallet is in a static or dynamic state, and a driving cylinder in the middle of a central plate applies a thrust to a pressure plate, and under the traction of a driving cylinder at a side end of a traction bracket, a static or dynamic fatigue property test of the suspension spring can be performed, and then the fatigue life of the suspension spring can be designed, and the experimental research device provides rich theoretical support for the fatigue performance of the suspension spring.

[0007] In a first aspect, the present disclosure provides a method for studying the static, dynamic and fatigue properties of a second-order stiffness suspension spring, specifically comprising: a set of integrated test equipment, the test equipment comprising: a fixed carrier plate and a positioning support plate, the fixed carrier plate being an octagonal structure, and having legs installed at the bottom edge of the fixed carrier plate, and having a driving cylinder installed at the middle position of the fixed carrier plate, and having a supporting vertical plate installed at the top edge of the fixed carrier plate; the positioning support plate being an octagonal structure, and having a positioning tube installed at the bottom of the positioning support plate, wherein the positioning tube is a cylindrical structure; the output end of the driving cylinder at the middle position of the fixed carrier plate is inserted into the interior of the positioning tube; a connecting plate is installed at the outer side of the fixed carrier plate; a fixed protective cover is installed at the outer end of the connecting plate, wherein a protective net is provided on the side of the fixed protective cover.

[0008] Furthermore, a centralizing plate is installed on the top of the supporting vertical plate; a driving cylinder is installed in the middle of the centralizing plate, and a supporting plate is installed at the top edge of the centralizing plate, and a positioning panel is installed on the top of the supporting plate.

[0009] Furthermore, a traction bracket is installed at the bottom of the positioning panel; the traction bracket is a cross-shaped structure, and a driving cylinder is installed at the bottom of the side end of the traction bracket; a positioning plate is installed on the outer side of the concentrating plate; and the output end of the driving cylinder at the bottom of the side end of the traction bracket is slidably installed on the inner side of the positioning plate.

[0010] Furthermore, a traction side plate is installed on the outer side of the positioning support plate; a traction vertical rod is installed on the top of the traction side plate; the traction vertical rod is a cylindrical structure, and a universal joint is rotatably installed on the top of the traction vertical rod; the top of the universal joint is rotatably connected to the output end of the driving cylinder at the bottom of the side end of the traction bracket.

[0011] Furthermore, a pressure plate is slidably installed between the four supporting vertical plates; the pressure plate is an octagonal structure, and a movable groove is opened on the top of the pressure plate; a movable plate is slidably installed inside the movable groove.

[0012] Furthermore, the movable plate is a circular structure, and the top of the movable plate is connected to the output end of the bottom of the driving cylinder in the middle position of the central plate; a detection plate is installed at the edge position of the bottom of the pressure plate, and a suspension spring is installed between the bottom of the pressure plate and the top of the positioning support plate.

[0013] Furthermore, a detection sensor is provided on the inner side of the detection plate; guide grooves are provided at the bottom of the pressure plate and the top of the positioning support plate; a driving rod is rotatably installed inside the guide groove; and the side ends of the driving rod respectively penetrate the side surfaces of the pressure plate and the positioning support plate.

[0014] Furthermore, a guide plate is slidably installed on the inner side of the guide groove; the guide plate is installed on the outer side of the driving rod, and strong fixing belts are installed on the outer ends of the two guide plates; a rubber pad is provided on the inner side of the strong fixing belt, and the strong fixing belt is installed on the top and bottom of the spring between the pressure plate and the positioning support plate.

[0015] Furthermore, a driving cylinder is installed on the outer side of the support plate at the top edge of the concentrating plate, and a traction plate is installed on the output end of the driving cylinder; the traction plate is installed on the top of the movable protective cover; the movable protective cover is movably installed on the outer side of the supporting vertical plate.

[0016] Further, the following steps are included:

[0017] First, place the suspension spring between the positioning support plate and the pressure plate, with the top and bottom ends of the spring on the inner side of the strong fixing belt;

[0018] Second, the driving rod is rotated to drive the guide plate to pull the strong fixing belt to fix the spring;

[0019] 3. The output end of the driving cylinder at the middle position of the fixed carrier is inserted into the positioning tube to position the positioning support plate;

[0020] Fourth, the driving cylinder in the middle of the central plate presses the pressure plate downward to apply load pressure to the suspension spring;

[0021] Fifth, the spring is tested by the detection sensor on the inner side of the detection plate to complete the fatigue performance test of the suspension spring under static conditions;

[0022] Sixth, make the output end of the driving cylinder at the middle position of the fixed carrier plate leave the positioning tube;

[0023] Seventh, the driving cylinder at the bottom of the side end of the traction bracket drives the positioning support plate to move to different positions, and the pressure plate applies load pressure to the spring;

[0024] 8. At the same time, the detection sensor on the inner side of the detection plate is used to detect the spring to realize the fatigue performance detection of the suspension spring under dynamic conditions;

[0025] Ninth, the driving cylinder drives the movable protective cover to move to the outside of the suspension spring between the pressure plate and the positioning support plate through the traction plate to protect the suspension spring from possible breakage.

[0026] The present invention provides a method for studying the static, dynamic and fatigue properties of a second-order stiffness suspension spring, which has the following beneficial effects:

[0027] When the present invention is in use, the suspension spring is clamped by using a pressure plate and a positioning support plate to test the fatigue performance under static and dynamic conditions. When the static and dynamic fatigue performance of the second-order stiffness suspension spring is studied, the suspension spring to be tested is installed between the pressure plate and the positioning support plate, and the output end of the driving cylinder on the fixed carrier plate is inserted into the positioning tube to position the positioning support plate. The position of the positioning support plate can be positioned so that the positioning support plate is in a static or dynamic state. The driving cylinder in the middle position of the central plate applies a thrust to the pressure plate, and under the traction of the driving cylinder at the side end of the traction bracket, the suspension spring can be tested for static or dynamic fatigue performance, and then the fatigue life of the suspension spring is designed. The experimental research device provides rich theoretical support for the fatigue performance of more suspension springs.

[0028] In addition, fixed and movable protective covers are used to protect springs that may break and splash during the test research. When conducting static and dynamic fatigue performance studies on the second-order stiffness suspension spring, the movable protective cover is located on the outside of the tested suspension spring under the traction of the drive cylinder to block the spring that may break and splash during the test, and the fixed protective cover protects the spring that falls downward again to prevent it from bouncing again after falling.

[0029] In addition, the suspension springs are tested using the detection sensors on the inside of the test plate, and the second-order stiffness suspension springs are calibrated in six aspects: strength, stiffness, natural frequency, stability, permanent deformation, and fatigue durability. The mechanical properties of the springs are studied by combining theoretical analysis, experimental technology, and simulation technology, and an integrated second-order stiffness suspension spring mechanical performance solution is established. This solution can be extended to other component systems, saving development cycle and cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solution of the embodiment of the present invention, the drawings of the embodiment are briefly introduced below.

[0031] The drawings described below are only related to some embodiments of the present invention, but are not intended to limit the present invention.

[0032] In the attached picture:

[0033] Figure 1 A schematic diagram showing the overall structure of the present application;

[0034] Figure 2 A schematic diagram of the three-dimensional structure of the positioning panel of the present application is shown;

[0035] Figure 3 A schematic diagram of the three-dimensional structure of the positioning plate of the present application is shown;

[0036] Figure 4 A schematic diagram of the three-dimensional structure of the positioning support plate of the present application is shown;

[0037] Figure 5 A schematic diagram of the three-dimensional structure of the traction vertical rod of the present application is shown;

[0038] Figure 6 A schematic diagram of the cross-sectional structure of the pressing plate of the present application is shown;

[0039] Figure 7 A schematic diagram of the three-dimensional structure of the movable protective cover of the present application is shown;

[0040] Figure 8 The flowchart of the research method of this application is shown;

[0041] Reference numerals list

[0042] 1. Fixed carrier plate; 101. Support vertical plate; 102. Centralizing plate; 103. Positioning panel; 104. Traction bracket; 105. Positioning plate;

[0043] 2. Positioning support plate; 201. Positioning tube; 202. Traction side plate; 203. Traction vertical rod; 204. Universal joint; 205. Pressing plate; 206. Movable groove; 207. Movable plate; 208. Detection plate; 209. Guide groove; 2010. Driving rod; 2011. Guide plate; 2012. Strong fixing belt;

[0044] 3. Connecting plate; 301. Fixed protective cover; 302. Traction plate; 303. Movable protective cover. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0046] Please refer to Figures 1 to 8 :

[0047] Embodiment 1:

[0048] The present invention proposes a method for studying the static, dynamic and fatigue properties of a second-order stiffness suspension spring, comprising: a set of integrated test devices, the test device comprising: a fixed carrier plate 1 and a positioning support plate 2, the fixed carrier plate 1 is an octagonal structure, and a support leg is installed at the bottom edge of the fixed carrier plate 1, and a driving cylinder is installed at the middle position of the fixed carrier plate 1, and a supporting vertical plate 101 is installed at the top edge of the fixed carrier plate 1; a concentrating plate 102 is installed at the top of the supporting vertical plate 101; a driving cylinder is installed at the middle position of the concentrating plate 102, and a support plate is installed at the top edge of the concentrating plate 102, and a positioning panel 103 is installed at the top of the support plate; a traction bracket 104 is installed at the bottom of the positioning panel 103; the traction bracket 104 is a cross-shaped structure, and a driving cylinder is installed at the bottom of the side end of the traction bracket 104; a positioning plate 105 is installed on the outer side of the concentrating plate 102; the output end of the driving cylinder at the bottom of the side end of the traction bracket 104 is slidably installed on the inner side of the positioning plate 105.

[0049] In the disclosed embodiment, when conducting static and dynamic fatigue performance research on the second-order stiffness suspension spring, the fixed carrier plate 1, the concentrating plate 102 and the positioning panel 103 form a structurally stable research and testing device to ensure the stability during the suspension spring research and testing process. The output end of the driving cylinder at the bottom of the side end of the traction bracket 104 moves through the positioning plate 105, and the output end of the driving cylinder can pull the positioning support plate 2 to move up and down to conduct dynamic fatigue performance research, so that the fatigue performance of the suspension spring can be studied in all aspects.

[0050] Embodiment 2, on the basis of embodiment 1, the positioning support plate 2 is an octagonal structure, and a positioning tube 201 is installed at the bottom of the positioning support plate 2, wherein the positioning tube 201 is a cylindrical structure; the output end of the driving cylinder at the middle position of the fixed carrier plate 1 is inserted into the inside of the positioning tube 201; a traction side plate 202 is installed on the outside of the positioning support plate 2; a traction vertical rod 203 is installed on the top of the traction side plate 202; the traction vertical rod 203 is a cylindrical structure, and a universal joint 204 is rotatably installed on the top of the traction vertical rod 203; the top of the universal joint 204 is rotatably connected to the output end of the driving cylinder at the bottom of the side end of the traction bracket 104; a pressing plate 205 is slidably installed between the four supporting vertical plates 101; the pressing plate 205 is an octagonal structure, and a movable groove 206 is opened on the top of the pressing plate 205; the movable groove 206 is slidably installed inside There is a movable plate 207; the movable plate 207 is a circular structure, and the top of the movable plate 207 is connected to the output end of the bottom of the driving cylinder in the middle position of the central plate 102; a detection plate 208 is installed at the edge position of the bottom of the pressing plate 205, and a suspension spring is installed between the bottom of the pressing plate 205 and the top of the positioning support plate 2; a detection sensor is provided on the inner side of the detection plate 208; a guide groove 209 is provided at the bottom of the pressing plate 205 and the top of the positioning support plate 2; a driving rod 2010 is rotatably installed inside the guide groove 209; the side ends of the driving rod 2010 respectively penetrate the side surfaces of the pressing plate 205 and the positioning support plate 2; a guide plate 2011 is slidably installed on the inner side of the guide groove 209; the guide plate 2011 is installed on the outer side of the driving rod 2010, and the outer ends of the two guide plates 2011 are installed with strong fixing belts 2012;A rubber pad is provided on the inner side of the strong fixing belt 2012, and the strong fixing belt 2012 is installed at the top and bottom of the spring between the pressure plate 205 and the positioning support plate 2. When the static and dynamic fatigue performance of the second-order stiffness suspension spring is studied, the suspension spring is installed between the positioning support plate 2 and the pressure plate 205, and the top and bottom ends of the suspension spring are placed on the inner side of the strong fixing belt 2012. The side end of the driving rod 2010 is rotated on the outer side of the positioning support plate 2 and the pressure plate 205 to drive the guide plate 211 along the guide groove 2. 09 moves, the guide plate 2011 pulls the strong fixing belt 2012 to move to both sides, so that the strong fixing belt 2012 fixes the top and bottom ends of the spring. The strong fixing belt 2012 has a large coverage area and can position suspension springs of different specifications. It has a simple structure and convenient operation. The output end of the driving cylinder in the middle position of the fixed carrier plate 1 is inserted into the inside of the positioning tube 201 to position the position of the positioning support plate 2, ensuring the stability of the positioning support plate 2 without shaking. Then the middle position of the central plate 102 The output end of the driving cylinder drives the movable plate 207 installed inside the movable groove 206. The driving cylinder presses the pressure plate 205 downward to apply load pressure to the suspension spring. The detection sensor inside the detection plate 208 can be used to detect strength, stiffness, natural frequency, deformation and other aspects, and the fatigue performance of the suspension spring is tested in static state. After the output end of the driving cylinder at the middle position of the fixed carrier plate 1 leaves the positioning tube 201, the output end of the driving cylinder at the bottom of the side end of the traction bracket 104 drives the universal joint 204 to deform. The bottom of the universal joint 204 drives the positioning support plate 2 to move through the traction vertical rod 203 and the traction side plate 202, so that the positioning support plate 2 moves to different positions. The pressure plate 205 applies load pressure to the spring. The detection sensor inside the detection plate 208 can be used to detect strength, stiffness, natural frequency, deformation and other aspects, and the fatigue performance of the suspension spring is tested in dynamic state. The fatigue performance of the suspension spring can be comprehensively studied, which is convenient for designing the fatigue life of the suspension spring. ;

[0051] Embodiment 3, on the basis of embodiment 1, a connecting plate 3 is installed on the outer side of the fixed carrier plate 1; a fixed protective cover 301 is installed on the outer end of the connecting plate 3, wherein a protective net is provided on the side of the fixed protective cover 301; a driving cylinder is installed on the outer side of the support plate at the top edge position of the concentrating plate 102, and a traction plate 302 is installed on the output end of the driving cylinder; the traction plate 302 is installed on the top of the movable protective cover 303; the movable protective cover 303 is movably installed on the outer side of the supporting vertical plate 101, when the static and dynamic fatigue performance of the second-order stiffness suspension spring is studied, the output end of the driving cylinder on the outer side of the support plate at the top edge position of the concentrating plate 102 drives the traction plate 302 to move, and the traction plate 302 drives the movable protective cover 303 to the outer side of the suspension spring between the pressing plate 205 and the positioning support plate 2, and the suspension spring that may break during the experimental research process is blocked to reduce the problem of spring splashing and injuring others, and the blocked spring falls on the inner side of the fixed protective cover 301, and the connecting plate 3 positions the position of the fixed protective cover 301 to prevent the spring from bouncing again.

[0052] The steps include:

[0053] First, place the suspension spring between the positioning support plate 2 and the pressure plate 205, with the top and bottom ends of the spring on the inner side of the strong fixing belt 2012;

[0054] Second, the driving rod 2010 is rotated to drive the guide plate 2011 to pull the strong fixing belt 2012 to fix the spring;

[0055] Third, the output end of the driving cylinder at the middle position of the fixed carrier plate 1 is inserted into the positioning tube 201 to position the positioning support plate 2;

[0056] Fourth, the driving cylinder in the middle of the central plate 102 presses the pressure plate 205 downward to apply load pressure to the suspension spring;

[0057] Fifth, the spring is tested by the detection sensor on the inner side of the detection plate 208 to complete the fatigue performance test of the suspension spring under static conditions;

[0058] Sixth, make the output end of the driving cylinder at the middle position of the fixed carrier plate 1 leave the positioning tube 201;

[0059] Seventh, the driving cylinder at the bottom of the side end of the traction bracket 104 drives the positioning support plate 2 to move to different positions, and the pressure plate 205 applies load pressure to the spring;

[0060] Eighth, the detection sensor on the inner side of the detection plate 208 is used to detect the spring at the same time to realize the fatigue performance detection of the suspension spring under dynamic conditions;

[0061] Ninth, the driving cylinder drives the movable protective cover 303 to move to the outside of the suspension spring between the pressing plate 205 and the positioning support plate 2 through the traction plate 302 to protect the suspension spring from possible breakage.

[0062] The working principle of this embodiment is as follows: when in use, the suspension spring is installed between the positioning support plate 2 and the pressure plate 205, and the top and bottom ends of the suspension spring are placed on the inner side of the strong fixing belt 2012. The side end of the rotating driving rod 2010 drives the guide plate 2011 to move along the guide groove 209, and the guide plate 2011 pulls the strong fixing belt 2012 to move to both sides to fix the top and bottom ends of the spring. The output end of the driving cylinder in the middle position of the fixed carrier plate 1 is inserted into the positioning tube 201 to position the positioning support plate 2, and the output end of the driving cylinder in the middle position of the central plate 102 drives the movable plate 207 to be installed in the movable groove 206. The driving cylinder presses the pressure plate 205 to move downward to apply load pressure to the suspension spring. The detection sensor on the inner side of the detection plate 208 can be used to detect the strength, stiffness, natural frequency, deformation and other aspects of the suspension. The spring is tested for fatigue performance under static conditions. After the output end of the driving cylinder in the middle position of the fixed carrier plate 1 leaves the positioning tube 201, the output end of the driving cylinder at the bottom of the side end of the traction bracket 104 drives the universal joint 204 to deform. The bottom of the universal joint 204 drives the positioning tray 2 to move through the traction vertical rod 203 and the traction side plate 202. The positioning tray 2 moves to different positions. The pressure plate 205 applies load pressure to the spring. The strength, stiffness, natural frequency, deformation and other aspects are tested through the detection sensor on the inner side of the detection plate 208. The fatigue performance of the suspension spring is tested under dynamic conditions. The output end of the driving cylinder on the outer side of the support plate at the top edge position of the concentration plate 102 drives the movable protective cover 303 to the outside of the suspension spring between the pressure plate 205 and the positioning tray 2 through the traction plate 302 to block the suspension spring that may break.

[0063] In this article, there are a few points to note:

[0064] 1. The drawings of the embodiments of the present disclosure only involve structures related to the embodiments of the present disclosure, and other structures may refer to general designs.

[0065] 2. In the absence of conflict, the embodiments of the present disclosure and the features therein may be combined with each other to obtain new embodiments.

[0066] The above are only specific embodiments of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present disclosure, which should be included in the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be based on the protection scope of the claims.

Claims

1. A method for studying the static, dynamic and fatigue properties of a second-order stiffness suspension spring, comprising: A set of integrated test device, characterized in that the test device comprises: a fixed carrier plate (1) and a positioning support plate (2), wherein the bottom edge of the fixed carrier plate (1) is provided with a support leg, the middle position of the fixed carrier plate (1) is provided with a driving cylinder, and the top edge of the fixed carrier plate (1) is provided with a supporting vertical plate (101); the bottom of the positioning support plate (2) is provided with a positioning tube (201), wherein the positioning tube (201) is a cylindrical structure; the output end of the driving cylinder at the middle position of the fixed carrier plate (1) is inserted into the interior of the positioning tube (201); the outer side of the fixed carrier plate (1) is provided with a connecting plate (3); the outer end of the connecting plate (3) is provided with a fixed protective cover (301), wherein a protective net is provided on the side of the fixed protective cover (301).

2. A method for studying static, dynamic and fatigue properties of a second-order stiffness suspension spring according to claim 1, characterized in that: A centralizing plate (102) is installed on the top of the supporting vertical plate (101); a driving cylinder is installed in the middle of the centralizing plate (102), and a supporting plate is installed at the top edge of the centralizing plate (102); a positioning panel (103) is installed on the top of the supporting plate.

3. A method for studying static, dynamic and fatigue properties of a second-order stiffness suspension spring according to claim 2, characterized in that: A traction bracket (104) is installed at the bottom of the positioning panel (103); a driving cylinder is installed at the bottom of the side end of the traction bracket (104); a positioning plate (105) is installed on the outer side of the concentrating plate (102); and an output end of the driving cylinder at the bottom of the side end of the traction bracket (104) is slidably installed on the inner side of the positioning plate (105).

4. The method for studying static, dynamic and fatigue performance of a second-order stiffness suspension spring according to claim 1, characterized in that: A traction side plate (202) is installed on the outer side of the positioning support plate (2); a traction vertical rod (203) is installed on the top of the traction side plate (202); a universal joint (204) is rotatably installed on the top of the traction vertical rod (203); the top of the universal joint (204) is rotatably connected to the output end of the driving cylinder at the bottom of the side end of the traction bracket (104).

5. The method for studying static, dynamic and fatigue performance of a second-order stiffness suspension spring according to claim 1, characterized in that: A pressing plate (205) is slidably installed between the four supporting vertical plates (101); the pressing plate (205) is an octagonal structure, and a movable groove (206) is opened on the top of the pressing plate (205); a movable plate (207) is slidably installed inside the movable groove (206).

6. A method for studying static, dynamic and fatigue properties of a second-order stiffness suspension spring according to claim 5, characterized in that: The top of the movable plate (207) is connected to the output end of the bottom of the driving cylinder at the middle position of the central plate (102); a detection plate (208) is installed at the edge of the bottom of the pressing plate (205), and a suspension spring is installed between the bottom of the pressing plate (205) and the top of the positioning support plate (2).

7. A method for studying static, dynamic and fatigue properties of a second-order stiffness suspension spring according to claim 6, characterized in that: A detection sensor is provided on the inner side of the detection plate (208); a guide groove (209) is provided at the bottom of the pressure plate (205) and the top of the positioning support plate (2); a driving rod (2010) is rotatably installed inside the guide groove (209); and the side ends of the driving rod (2010) respectively penetrate the side surfaces of the pressure plate (205) and the positioning support plate (2).

8. The method for studying static, dynamic and fatigue performance of a second-order stiffness suspension spring according to claim 7, characterized in that: A guide plate (2011) is slidably mounted on the inner side of the guide groove (209); the guide plate (2011) is mounted on the outer side of the driving rod (2010), and strong fixing belts (2012) are mounted on the outer ends of the two guide plates (2011); a rubber pad is provided on the inner side of the strong fixing belt (2012), and the strong fixing belt (2012) is mounted on the top and bottom of the spring between the pressure plate (205) and the positioning support plate (2).

9. The method for studying static, dynamic and fatigue performance of a second-order stiffness suspension spring according to claim 2, characterized in that: A driving cylinder is installed on the outer side of the support plate at the top edge of the concentrating plate (102), and a traction plate (302) is installed on the output end of the driving cylinder; the traction plate (302) is installed on the top of the movable protective cover (303); the movable protective cover (303) is movably installed on the outer side of the supporting vertical plate (101).

10. A method for studying the static, dynamic and fatigue properties of a second-order stiffness suspension spring, characterized in that: The following steps are involved: First, place the suspension spring between the positioning support plate (2) and the pressure plate (205), with the top and bottom ends of the spring being located inside the strong fixing belt (2012); Second, the driving rod (2010) is rotated to drive the guide plate (2011) to pull the strong fixing belt (2012) to fix the spring; Third, the output end of the driving cylinder at the middle position of the fixed carrier plate (1) is inserted into the positioning tube (201) to position the positioning support plate (2); Fourth, the driving cylinder in the middle of the central plate (102) presses the pressure plate (205) downward to apply load pressure to the suspension spring; Fifth, the spring is tested by the detection sensor on the inner side of the detection plate (208), so as to complete the fatigue performance test of the suspension spring under static state; Sixth, the output end of the driving cylinder at the middle position of the fixed carrier plate (1) is separated from the positioning tube (201); Seventh, the driving cylinder at the bottom of the side end of the traction bracket (104) drives the positioning support plate (2) to move to different positions, and the pressure plate (205) applies load pressure to the spring; Eighth, the spring is tested by using the test sensor on the inner side of the test plate (208) to test the fatigue performance of the suspension spring under dynamic conditions; Ninth, the driving cylinder drives the movable protective cover (303) to move to the outside of the suspension spring between the pressing plate (205) and the positioning support plate (2) through the traction plate (302) to protect the suspension spring from possible breakage.

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