A periodic immersion stress corrosion test device and method

Abstract

A cyclic immersion stress corrosion test device and method, the device includes an adjustable bracket, a lever-type loading system and a corrosion liquid tank that can be automatically raised and lowered periodically; the adjustable bracket includes a support tube, a horizontal crossbar, an adjustable support rod and a fixed pulley; the lever-type loading system includes a lever-type loading rod, a connecting line and a counterweight block; the corrosion liquid tank that can automatically be raised and lowered periodically includes a corrosion liquid tank, a corrosion liquid and an eccentric wheel system. The present invention also includes a cyclic immersion stress corrosion method implemented using the device. The device applies a bending moment through a lever-type loading rod to introduce stress into the sample, and realizes cyclic immersion of the sample through an eccentric wheel system, which can simulate a cyclic alternating stress corrosion process, and the sample size, stress size and cyclic immersion rate can all be adjusted, and has the advantages of being simple, easy to operate, economical and efficient.

Description

Technical Field

[0001] The invention relates to a metal material performance testing device and method, and in particular to a periodic immersion stress corrosion testing device and method. Background Art

[0002] More and more highway and railway bridges are made of steel structures due to their advantages such as light weight, high strength, easy assembly and construction, good vibration and earthquake resistance, etc. However, steel has poor corrosion resistance and will corrode and degrade with the aging of anti-corrosion measures during long-term service. Therefore, research on the corrosion resistance of steel, as well as the static and dynamic strength and fatigue performance of corroded steel or metal materials has received continuous attention.

[0003] Most of the existing research on the corrosion performance of metal materials is to corrode the stress-free samples by placing them in the atmosphere, immersing them in corrosive liquids, or placing them in salt spray corrosion test chambers, and then testing the mechanical properties of the samples after a certain period of corrosion. However, this test mode cannot effectively simulate the real stress corrosion state of bridge structures or engineering structures. Some stress corrosion tests use a mode in which stress is applied through an auxiliary loading frame, and the loading frame and the sample are simultaneously placed in a corrosive environment for treatment. Under this test method, a periodic corrosive environment is difficult to achieve. The method of immersing in corrosive liquid requires manual removal and immersion of the sample regularly, and the accelerated salt spray corrosion chamber that can achieve a periodic corrosive environment is expensive. Therefore, the existing testing technology lacks an economical and efficient stress corrosion test device and method that can achieve a periodic corrosive environment. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a periodic immersion stress corrosion test device and method which is simple, easy to operate, economical and efficient and can adjust the stress size and immersion cycle.

[0005] The technical solution adopted by the present invention to solve the technical problem is: a periodic immersion stress corrosion test device, including an adjustable bracket, a lever-type loading system and a corrosion liquid tank that can automatically rise and fall periodically;

[0006] The adjustable bracket includes a support tube, a horizontal cross bar, an adjustable support rod and a fixed pulley. The adjustable support rod is sleeved in the support tube and can move up and down in the support tube. When the adjustable support rod reaches a predetermined position, the adjustable support rod is fixed. The fixed pulley is installed on the top of the adjustable support rod through a pin shaft. Both ends of the horizontal cross bar are fixedly connected to the support tube respectively to form a support frame of the lever-type loading rod system.

[0007] The lever-type loading system comprises a lever-type loading rod, a connecting line and a counterweight block. The lever-type loading rods are two and are respectively sleeved on the horizontal crossbar through round holes. The upper part of the lever-type loading rod is connected to the counterweight block through a connecting line, and the connecting line bypasses the fixed pulley. The lower part of the lever-type loading rod is provided with a structure for installing the corrosion sample and is arranged opposite to each other.

[0008] The automatic periodic lifting and lowering corrosion liquid tank is located below the lever-type loading rod.

[0009] Furthermore, the adjustable bracket and the lever-type loading rod are made of metal rods with anti-corrosion protection measures. Of course, they can also be made of corrosion-resistant and high-strength materials such as hard high-strength plastics or carbon fiber.

[0010] Furthermore, the lever-type loading rod is of L-shaped structure, with a circular hole in the middle of its vertical long limb, the diameter of the circular hole is larger than the diameter of the horizontal cross bar, the lower part of the lever-type loading rod is an L-shaped right-angle bent end, and a square hole is opened at the end, and the corrosion sample can be inserted into the square hole and embedded.

[0011] Furthermore, both ends of the connecting line are provided with lifting rings, one end of the lifting ring is sleeved on the lever-type loading rod, and the other end of the lifting ring is used to hang a counterweight.

[0012] Furthermore, the automatic periodic lifting and lowering corrosion liquid tank comprises a corrosion liquid tank, the corrosion liquid tank is filled with corrosion liquid, an eccentric wheel system is installed at the lower part of the corrosion liquid tank, and the eccentric wheel system is driven by a motor to rotate at a constant speed to realize the automatic periodic lifting and lowering of the corrosion liquid tank. The liquid level of the corrosion liquid is determined based on the support height of the lever-type loading rod. When the corrosion liquid tank drops to the lowest point, the lower end of the lever-type loading rod and the corrosion sample can be located above the liquid level. When the corrosion liquid tank rises to the highest point, the lower end of the lever-type loading rod and the corrosion sample can be immersed in the corrosion liquid.

[0013] Furthermore, the eccentric wheel system includes an elliptical rotating wheel, a rotating shaft, a circular bearing ring and bearing steel balls. The elliptical rotating wheel is of an elliptical structure. The rotating shaft is located at the long axis of the ellipse and deviates from the center of the long axis. The bearing steel balls are filled in the circular bearing ring. When the elliptical rotating wheel rotates, it can roll in contact with the bearing steel balls to achieve smooth rotation of the elliptical rotating wheel. The rotating shaft is connected to the motor to rotate at a constant speed, driving the elliptical rotating wheel to rotate at a constant speed, and then driving the circular bearing ring and the corrosion liquid tank supported on the eccentric wheel system to automatically rise and fall periodically.

[0014] The periodic immersion stress corrosion test method implemented by the device comprises the following steps:

[0015] (1) Insert both ends of the corrosion specimen into the lower end of the lever-type loading rod;

[0016] (2) Adjust the height of the adjustable support rod and the mass of the counterweight block so that the bending moment at the bottom axis of the lever-type loading rod reaches a predetermined level;

[0017] (3) Inject the corrosive liquid into the corrosive liquid tank, and adjust the liquid level of the corrosive liquid so that the corrosion sample can be completely immersed in the corrosive liquid when the corrosive liquid tank rises to the highest point, and the corrosion sample is completely above the corrosive liquid level when the corrosive liquid tank drops to the lowest point;

[0018] (4) Set the rotation rate of the rotating shaft in the eccentric wheel system so that the lifting and lowering cycle rate of the corrosion liquid tank meets the predetermined requirements.

[0019] The beneficial effects of the present invention are as follows: a lever-type loading system is formed by a lever-type loading rod, a connecting line, and a counterweight block, and a fixed pulley on an adjustable support rod is used to introduce a bending moment at the bottom of the lever-type loading rod by the principle of a lever, so that the metal sample area produces a pure bending stress state, and thus the upper and lower cross-sectional areas of the sample will form a tensile and compressive stress state. The loading arm can be changed by the upward and downward extension of the adjustable support rod in the support tube, and combined with the mass adjustment of the counterweight block, a stepless change of the bending moment in a wide range can be achieved. On the other hand, the periodic lifting and lowering of the corrosion liquid tank can be achieved by the periodic rotation of the eccentric wheel in conjunction with the circular bearing ring fixed to the corrosion liquid tank, and the lifting and lowering rate can be adjusted by the rotation rate of the eccentric wheel. The test device has a simple structure, a clear principle, and does not require a complex control system, and can be easily made by yourself. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the structure of the test device when the corrosion liquid tank rises to the highest point and the corrosion sample is immersed in the corrosion liquid;

[0021] Figure 2 It is a schematic diagram of the structure of the test device when the corrosion liquid tank is lowered to the lowest point and the corrosion sample is located above the corrosion liquid surface;

[0022] Figure 3 yes Figure 1 A three-dimensional schematic diagram of the lever-type loading rod in the test device shown;

[0023] Figure 4 yes Figure 1 An enlarged schematic diagram of the eccentric wheel system in the test device shown;

[0024] Figure 5 is a three-dimensional schematic diagram of the corrosion specimen;

[0025] Figure 6 It is a three-dimensional schematic diagram of the corrosion specimen placed in the lever-type loading rod;

[0026] In the figure: 1. adjustable bracket, 11. support tube, 12. horizontal cross bar, 13. adjustable support rod, 14. tightening bolt, 15. fixed pulley, 16. pin; 2. lever-type loading system, 21. lever-type loading rod, 22. connecting line, 23. counterweight, 211. round hole, 212. L-shaped right-angle bent end, 213. square hole; 3. automatic periodic lifting and lowering corrosion liquid tank, 31. corrosion liquid tank, 32. corrosion liquid, 33. eccentric wheel system, 331. elliptical wheel, 332. rotating shaft, 333. circular bearing ring, 334. bearing steel ball; 4. corrosion specimen. DETAILED DESCRIPTION

[0027] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0028] Reference Figure 1-Figure 6 , a periodic immersion stress corrosion test device, comprising an adjustable bracket 1, a lever-type loading system 2 and a corrosion liquid tank 3 that can automatically rise and fall periodically;

[0029] The adjustable bracket 1 includes a support tube 11, a horizontal cross bar 12, an adjustable support rod 13 and a fixed pulley 15. The adjustable support rod 13 is sleeved in the support tube 11 and can move up and down in the support tube 11. When the adjustable support rod 13 reaches a predetermined position, the adjustable support rod 13 is fixed by applying an extrusion force to the adjustable support rod 13 by tightening a tightening bolt 14 passing through the tube wall of the support tube 11. The fixed pulley 15 is installed on the top of the adjustable support rod 13 through a pin 16. The two ends of the horizontal cross bar 12 are respectively fixedly connected to the support tube 11 to form a support frame of the lever-type loading rod system 2;

[0030] The lever-type loading system 2 includes a lever-type loading rod 21, a connecting line 22 and a counterweight 23. The lever-type loading rod 21 is two in number and is respectively sleeved on the horizontal crossbar 12 through a circular hole 211. The upper portion of the lever-type loading rod 21 is connected to the counterweight 23 through a connecting line 22, and the connecting line 22 bypasses the fixed pulley 15. The lower portion of the lever-type loading rod 21 is provided with a structure for mounting the corrosion specimen 4 and is arranged opposite to each other.

[0031] The automatically periodically lifting and lowering corrosive liquid tank 3 is located below the lever-type loading system 2 .

[0032] In this embodiment, the adjustable bracket 1 and the lever-type loading rod 21 are made of metal rods with anti-corrosion protection measures. Of course, they can also be made of corrosion-resistant and high-strength materials such as hard high-strength plastics or carbon fiber.

[0033] In this embodiment, a triangular support structure is provided at the bottom of the support tube 11. The surface of the horizontal cross bar 12 is smooth, and the friction between the horizontal cross bar 12 and the lever-type loading rod 21 can be ignored.

[0034] In this embodiment, the lever-type loading rod 21 is an L-shaped structure, and a circular hole 211 is opened in the middle of the vertical long limb. The diameter of the circular hole 211 is larger than the diameter of the horizontal cross bar 12. The lower part of the lever-type loading rod 21 is an L-shaped right-angle bent end 212, and a square hole 213 is opened at the end. Figure 3 As shown, the corrosion sample 4 can be inserted into the square hole 213 and embedded.

[0035] In this embodiment, both ends of the connecting line 22 are provided with lifting rings, one end of the lifting ring is sleeved on the lever-type loading rod 21, and the other end of the lifting ring is used to hang the counterweight 23.

[0036] In this embodiment, the automatically periodically lifting and lowering corrosion liquid tank 3 comprises a corrosion liquid tank 31 , wherein the corrosion liquid tank 31 is filled with corrosion liquid 32 , and two sets of eccentric wheel systems 33 are installed at the lower part of the corrosion liquid tank 31 .

[0037] The eccentric wheel system 33 includes an elliptical wheel 331, a rotating shaft 332, a circular bearing ring 333 and a bearing steel ball 334. The elliptical wheel 331 is an elliptical structure. The rotating shaft 332 is located at the long axis of the ellipse and deviates from the center of the long axis. The distances from the center of the rotating shaft 332 to the long end and the short end of the ellipse are Δ1 and Δ2 respectively. Figure 4 As shown, the bearing steel ball 334 is filled in the circular bearing ring 333, and the elliptical wheel 331 can roll with the bearing steel ball 334 when rotating, so as to realize the smooth rotation of the elliptical wheel 331. The rotating shaft is connected to the motor to rotate at a constant speed, driving the elliptical wheel to rotate at a constant speed, and then driving the circular bearing ring and the corrosion liquid tank supported on the eccentric wheel system to automatically rise and fall periodically. When the elliptical wheel 331 rotates at a speed n (unit: rpm), the time required for the corrosion liquid tank 31 to complete a lifting is 1 / n minutes. The net lifting height of the corrosion liquid tank 31 is Δ1-Δ2. When the corrosion liquid 32 is injected, the distance between the liquid level and the horizontal axis of the specimen thickness direction is controlled to be (Δ1-Δ2) / 2, so that the corrosion sample 4 can be periodically immersed and separated from the liquid surface when the corrosion liquid tank 31 is periodically lifted and lowered.

[0038] The periodic immersion stress corrosion test method implemented by the device comprises the following steps:

[0039] (1) Insert both ends of the corrosion specimen 4 into the lower part of the lever-type loading rod 21;

[0040] (2) Adjust the height of the adjustable support rod 13 and the mass of the counterweight block 23 so that the bending moment at the bottom axis of the lever-type loading rod 21 reaches a predetermined level, and tighten the top bolt 14;

[0041] (3) injecting the etching liquid 32 into the etching liquid tank 31, and adjusting the liquid level of the etching liquid 32 so that the etching sample 4 can be completely immersed in the etching liquid 32 when the etching liquid tank 31 rises to the highest point, and the etching sample 4 is completely located above the liquid level of the etching liquid 32 when the etching liquid tank 31 drops to the lowest point;

[0042] (4) The rotation rate of the rotating shaft 332 in the eccentric wheel system 33 is set so that the lifting and lowering cycle rate of the corrosion liquid tank 31 meets the predetermined requirements.

[0043] In this embodiment, the corrosion sample 4 is a dog-bone plate or rod, and its two ends are clamping ends. The cross-sectional size of the clamping end is slightly smaller than the cross-sectional size of the square hole 213 of the lever-type loading rod 21. The two ends of the corrosion sample 4 are respectively inserted into the end square holes 213 of the lever-type loading rod 21 placed opposite to each other. Figure 5 and Figure 6 shown.

[0044] In this embodiment, the vertical distance between the axis of the horizontal crossbar 12 and the horizontal axis of the L-shaped right-angle bent end 212 is L1, the vertical distance between the horizontal section of the connecting line 22 and the axis of the horizontal crossbar 12 is L2, the mass of the counterweight 23 is M, and the gravitational acceleration is g. After the corrosion sample 4 and the device are assembled, the bending moment applied to the corrosion sample 4 is equal to Mg(L1+L2). Figure 5 As shown in the figure, the corrosion specimen 4 will produce tensile and compressive stress on its upper and lower surfaces under the pure bending force at both ends. When a rectangular cross-section plate is selected, and the width of the small cross-section test section in the middle is b, and the thickness of the plate is t, the tensile and compressive stress is 6Mg(L1+L2) / bt 2 .

[0045] Although the preferred embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the above-mentioned specific embodiments, which are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which fall within the scope of protection of the present invention.

Claims

1. A periodic immersion stress corrosion test device, characterized in that: It includes an adjustable bracket, a lever-type loading system and a corrosion liquid tank that can be automatically raised and lowered periodically; the adjustable bracket includes a support tube, a horizontal cross bar, an adjustable support rod and a fixed pulley, the support tubes are two, which are vertically arranged on both sides of the corrosion liquid tank that can be automatically raised and lowered periodically, the adjustable support rods are two, which are respectively sleeved in the support tubes on both sides and can move up and down in the support tubes, and when the adjustable support rods reach the predetermined position, the adjustable support rods are fixed, the fixed pulleys are two, which are respectively installed on the top of the two adjustable support rods through pins, and the two ends of the horizontal cross bar are respectively fixedly connected to the support tube to form a supporting frame of the lever-type loading rod system; the lever-type loading system includes a lever-type loading rod, a connecting line and a counterweight block, the lever-type loading rods are two, which are respectively sleeved on the horizontal cross bar through round holes, and the counterweight blocks are two, which are respectively located at two On the outside of the support tube, the upper part of the lever-type loading rod is connected to the counterweight block on the same side through a connecting line, and the connecting line bypasses the fixed pulley. The lower part of the lever-type loading rod is provided with a structure for installing the corrosion sample, and the structures are arranged opposite to each other. The corrosion liquid tank that can be automatically raised and lowered periodically is located below the lever-type loading rod. The lever-type loading rod is an L-shaped structure, and a circular hole is opened in the middle of its vertical long limb section, and the diameter of the circular hole is larger than the diameter of the horizontal cross bar. The lower end of the lever-type loading rod is an L-shaped right-angle bent end, and a square hole is opened at the end, and the corrosion sample can be inserted into the square hole and embedded. A lever-type loading system is formed by the lever-type loading rod, the connecting line, and the counterweight block, and the fixed pulley on the adjustable support rod is used to introduce a bending moment at the bottom of the lever-type loading rod according to the principle of leverage, so that the corrosion sample area produces a pure bending stress state, so that the upper and lower cross-sectional areas of the corrosion sample will form a tensile and compressive stress state.

2. The periodic immersion stress corrosion testing device according to claim 1, characterized in that: The adjustable bracket and the lever-type loading rod are made of metal rods with anti-corrosion protection measures.

3. The periodic immersion stress corrosion testing device according to claim 1 or 2, characterized in that: Both ends of the connecting line are provided with lifting rings, one end of the lifting ring is sleeved on the lever-type loading rod, and the other end of the lifting ring is used to hang a counterweight.

4. The periodic immersion stress corrosion testing device according to claim 1 or 2, characterized in that: The automatically periodically lifting and lowering corrosion liquid tank comprises a corrosion liquid tank, wherein the corrosion liquid tank is filled with corrosion liquid, and an eccentric wheel system is installed at the lower part of the corrosion liquid tank. The eccentric wheel system is driven by a motor to rotate at a constant speed to realize the automatic periodic lifting and lowering of the corrosion liquid tank.

5. The periodic immersion stress corrosion testing device according to claim 4, characterized in that: The liquid level of the corrosive liquid is determined based on the support height of the lever-type loading rod. When the corrosive liquid tank drops to the lowest point, the lower end of the lever-type loading rod and the corrosion sample can be located above the liquid level. When the corrosive liquid tank rises to the highest point, the lower end of the lever-type loading rod and the corrosion sample can be immersed in the corrosive liquid.

6. The periodic immersion stress corrosion testing device according to claim 4, characterized in that: The eccentric wheel system includes an elliptical rotating wheel, a rotating shaft, a circular bearing ring and bearing steel balls. The elliptical rotating wheel is of an elliptical structure. The rotating shaft is located at the long axis of the ellipse and deviates from the center of the long axis. The bearing steel balls are filled in the circular bearing ring. When the elliptical rotating wheel rotates, it can roll with the bearing steel balls to achieve smooth rotation of the elliptical rotating wheel. The rotating shaft is connected to the motor to rotate at a constant speed, driving the elliptical rotating wheel to rotate at a constant speed, and then driving the circular bearing ring and the corrosion liquid tank supported on the eccentric wheel system to automatically rise and fall periodically.

7. A periodic immersion stress corrosion test method implemented by the device of claim 1, characterized in that: The following steps are involved: (1) Insert both ends of the corrosion specimen into the lower end of the lever-type loading rod; (2) Adjust the height of the adjustable support rod and the mass of the counterweight block so that the bending moment at the bottom axis of the lever-type loading rod reaches a predetermined level; (3) Inject the corrosive liquid into the corrosive liquid tank, and adjust the liquid level of the corrosive liquid so that the corrosion sample can be completely immersed in the corrosive liquid when the corrosive liquid tank rises to the highest point, and the corrosion sample is completely above the corrosive liquid level when the corrosive liquid tank drops to the lowest point; (4) The rotation rate of the rotating shaft in the eccentric wheel system is set so that the lifting and lowering cycle rate of the corrosion liquid tank meets the predetermined requirements.

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