An electrochemical hydrogen-charged slow strain rate in-situ tensile device

Abstract

This invention provides an electrochemical hydrogen-charged slow strain rate in-situ tensile testing device, comprising an electrochemical hydrogen-charged unit, a sealing unit, and an in-situ tensile unit. The hydrogen-charged unit includes platinum electrodes, a DC power supply, and an electrolytic cell. The sealing unit consists of a compression spring, a sealing rubber ring, and a PVC sealing ring. The in-situ tensile unit comprises a set of lead screw guides, a sample clamping device, and an upper mechanism. The in-situ tensile sample is fixed by the clamping device and penetrates the upper and lower ends of the electrolytic cell, with the gauge length completely immersed in the electrolyte. The pressure generated by the deformation of the compression spring and the sealing rubber ring ensure the sealing of the in-situ tensile sample in the electrolytic cell. This invention solves the problem of experimentally testing the slow strain rate mechanical properties of samples under the influence of internal and external hydrogen in a hydrogen-containing environment. Furthermore, the device has a simple structure, small overall size, and is easy to operate, making it suitable for experimental research and verification of hydrogen damage in materials.

Description

Technical Field

[0001] This invention relates to the field of measuring the mechanical properties of metals in a hydrogen-containing environment, specifically to an electrochemical hydrogen-charged slow strain rate in-situ tensile device. Background Technology

[0002] Energy structure transformation is a major national need, and hydrogen energy, as a renewable energy source, has broad prospects for industrial development. Currently, the hydrogen energy industry is being deployed on a large scale across the country. Consequently, the development of safety assurance technologies for equipment and structural components throughout the entire hydrogen energy industry chain is also progressing rapidly.

[0003] Typical hydrogen energy industry equipment and structural components, such as hydrogen refueling station equipment and hydrogen pipelines, face problems such as hydrogen embrittlement and hydrogen-induced cracking when operating in hydrogen-environment environments. The sources of hydrogen in materials can be divided into two categories: one is internal hydrogen that enters the material through physical adsorption, decomposition, and diffusion under hydrogen pressure, such as from hydrogen-blended natural gas pipelines and pure hydrogen pipelines; the other is external hydrogen in the service environment.

[0004] Equipment and structural components operating in hydrogen-environment environments are typically subjected to the combined effects of stress and chemical potential, leading to hydrogen damage phenomena such as hydrogen embrittlement, hydrogen-induced cracking, and hydrogen blistering. Hydrogen embrittlement, specifically the degradation of strength, stiffness, and toughness caused by hydrogen diffusion and accumulation within the metal, falls under the category of early-stage hydrogen damage. Irreversible damage occurs when hydrogen, penetrating the metal interior and accumulating at dislocations and grain boundaries in atomic and molecular form, induces microcrack propagation, and can even cause structural component fracture. Therefore, studying the early-stage hydrogen damage state of metals under the influence of internal and external hydrogen is of significant practical importance for preventing the failure of structural components operating in hydrogen-environment environments.

[0005] Currently, the generally accepted mechanisms of hydrogen embrittlement in metallic materials include the hydrogen pressure theory, the hydrogen-induced reduction of interfacial bonding forces theory, the hydrogen-induced promotion of local plastic deformation theory, and the hydrogen-induced strain-induced vacancy aggregation theory. To explore the fundamental mechanisms of hydrogen embrittlement and ensure the safety of metallic materials during use, it is essential to investigate the effects of hydrogen content on the mechanical properties of materials and the mechanisms of performance degradation under laboratory conditions.

[0006] Hydrogen charging can be categorized into static and dynamic charging based on whether stress is applied during the process. Static charging under unloaded conditions is a well-established method, commonly including room temperature gas-phase charging, high-temperature and high-pressure charging, and electrochemical charging. Room temperature gas-phase charging involves direct immersion in an acidic solution or crude oil, with increasing hydrogen concentration entering the metal over time. This method is simple to operate but has poor charging efficiency. High-temperature and high-pressure charging, while effective, requires prolonged exposure to high temperatures and pressures, conditions difficult to maintain in most laboratories, compromising experimental safety. Electrochemical charging allows for rapid attainment of high hydrogen concentrations in samples. The required hydrogen concentration can be easily controlled by adjusting charging time, current, and electrolyte concentration, making it a common experimental hydrogen charging method.

[0007] Comparing the three hydrogen filling methods, although each has its own advantages, they all have unavoidable drawbacks. Therefore, in summary, it is necessary to design a dynamic laboratory hydrogen filling device that is simple to operate, has minimal safety hazards, and is easy to use. Summary of the Invention

[0008] To address the problems existing in the prior art, this invention provides an electrochemical hydrogen-charging slow strain rate in-situ stretching device, the main purpose of which is to solve the problems of high hydrogen-charging cost, long experimental cycle and complex structure.

[0009] The technical solution of the present invention is as follows:

[0010] An electrochemical hydrogen-charged slow strain rate in-situ tensile device is disclosed, comprising an electrochemical hydrogen-charged unit, a sealing unit, and an in-situ tensile unit, wherein:

[0011] The electrochemical hydrogen charging unit includes a DC power supply, a platinum electrode, an in-situ tensile specimen, and an electrolytic cell. In use, the platinum electrode and the in-situ tensile specimen are placed in the electrolytic cell containing hydrogen-charging electrolyte. The platinum electrode is connected to the anode of the DC power supply through wires, and the in-situ tensile specimen is connected to the cathode of the DC power supply.

[0012] The sealing unit includes a compression spring and a sealing rubber ring. In use, the compression spring is placed at the fixed end of the in-situ tensile specimen and contacts the PVC sealing ring and sealing cap. The axial elastic force formed by the compression of the spring itself compacts the sealing rubber ring, thereby achieving self-sealing of the fixed end of the in-situ tensile specimen during the slow hydrogen-filled tensile process.

[0013] The in-situ tensile unit includes a lead screw guide and a clamping device. The lead screw guide tensile device is a crucial component for maintaining the stability of the tensile specimen. Two lead screw guides of the same specifications are symmetrically assembled on both sides of the electrochemical hydrogen charging device. The two lead screw nuts are connected by metal connecting plates and fixing plates, and the metal connecting rods are fixed to the lead screw nuts by welding to maintain the parallel position of the two lead screw nuts.

[0014] The electrochemical hydrogen-charged slow strain rate in-situ tensile device has a through hole with the same diameter as the clamping end of the in-situ tensile specimen on the bottom surface of the electrolytic cell. After being connected to the clamping device at the lower end, it passes through a compression spring, a sealing rubber ring, and a PVC sealing ring, and is kept sealed by the electrolytic cell through the sealing unit.

[0015] In the electrochemical hydrogen-charged slow strain rate in-situ tensile device, both the metal sample and the platinum sheet are placed in the electrolytic cell. The platinum sheet is placed parallel to the left side of the metal sample and connected to the anode of the power supply through an insulated copper wire. The metal sample is connected to the cathode of the power supply through an insulated copper wire.

[0016] The electrochemical hydrogen-charged slow strain rate in-situ tensile device has symmetrical clamping devices made of metal, and the upper and lower clamping devices are directly connected to the metal sample by fastening bolts.

[0017] The electrochemical hydrogen-charged slow strain rate in-situ tensile device uses a ball screw as its guide rail. The ball screw is an ideal product for converting rotary motion into linear motion, with high precision, good stability, high sensitivity, and long service life.

[0018] The design concept of this invention is:

[0019] Existing hydrogen charging methods all have their own shortcomings. High-temperature and high-pressure hydrogen charging requires a high-temperature and high-pressure environment, which is usually difficult to meet in laboratories, and it also poses significant safety hazards. Secondly, current experiments on hydrogen embrittlement sensitivity typically employ pre-charging followed by a slow tensile test, with the tensile test performed after hydrogen charging. The pre-charging process, whether at room temperature or electrochemically, requires a significant amount of time and has limited hydrogen content. Furthermore, the transition from the hydrogen environment to the tensile test takes time, and the low strain rate and long duration of the tensile test make it difficult to prevent hydrogen escape.

[0020] This invention, while closely approximating real-world operating conditions, enables the simultaneous hydrogen charging and stretching of metallic materials. Different hydrogen concentrations can be obtained by varying the current. It reduces safety hazards, facilitates laboratory operation, allows for the design of specimens of varying sizes to suit different situations, requires minimal raw materials, is easy to process, and the small size of the metallic specimens promotes hydrogen diffusion within the sample. It is suitable for dynamic hydrogen charging and slow stretching systems where hydrogen charging and loading processes occur simultaneously, effectively addressing the issue of hydrogen escape during slow stretching experiments following hydrogen charging in studies of hydrogen embrittlement sensitivity.

[0021] The present invention has the following advantages and beneficial effects:

[0022] 1. The present invention has a simple structure, compact equipment, and uses common and readily available materials with low cost.

[0023] 2. This invention is simple to operate, has few safety hazards, and requires minimal laboratory expertise.

[0024] 3. This invention uses sealing gaskets, rubber, etc. for sealing. The device has a simple sealing structure and good sealing performance, which can effectively prevent the leakage of electrolyte and the escape of hydrogen.

[0025] 4. This invention uses fastening bolts to connect the clamp to the sample, and the tensioning device on both sides of the lead screw guide can load the sample under electrochemical hydrogen charging, effectively avoiding the problem of hydrogen escape during the experimental stage of pre-charging.

[0026] 5. This invention can control the current density during hydrogen charging by adjusting the input current of the DC power supply, thereby obtaining the required experimental conditions for different internal and external hydrogen states by controlling the hydrogen charging current density. Attached Figure Description

[0027] Figure 1 It is a structural schematic diagram of the present invention.

[0028] In the diagram, 1. DC power supply; 2. Metal connecting plate; 3. Guide rail slider; 4. Clamping device; 5. Electrolytic cell; 6. Platinum electrode; 7. Lead screw linear guide; 8. In-situ tensile specimen; 9. Sealing rubber ring; 10. PVC sealing ring; 11. Compression spring; 12. Clamping device fastening bolt; 13. Fixing plate; 14. Host computer. Detailed Implementation

[0029] The structure of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0030] In the specific implementation process, such as Figure 1 As shown, the dynamic electrochemical hydrogen charging test device in this embodiment has a symmetrical structure on the left and right sides and an asymmetrical structure on the top and bottom. It includes an electrochemical hydrogen charging unit, a sealing unit, and an in-situ tensile unit. It mainly consists of a platinum electrode 6, a DC power supply 1, an electrolytic cell 5, an in-situ tensile specimen 8, a compression spring 11, a sealing rubber ring 9, a PVC sealing ring 10, a set of lead screw guides 7, a metal connecting plate 2, a fixing plate 13, and a pair of specimen clamping devices 12. This device is lightweight and easy to operate, and can simultaneously charge the hydrogen and load the specimen, which helps reduce hydrogen escape and improves the reliability of experimental results.

[0031] The upper end face of the electrolytic cell 5 is open, and the lower end face has a through hole with the same diameter as the end of the in-situ tensile specimen 8. The end of the in-situ tensile specimen 8 passes through the through hole and is connected to the clamping device 12 by fastening bolts. A sealing rubber ring 9, a PVC sealing ring 10, and a compression spring 11 are placed at the lower end of the in-situ tensile specimen 8, passing through the through hole of the electrolytic cell 5 into the interior of the electrolytic cell 5. The compressive stress generated by the self-extension deformation of the compression spring 11 achieves self-sealing of the tensile device, preventing electrolyte leakage.

[0032] Electrolytic cell 5 is filled with NaOH electrolyte. The gauge length of the in-situ tensile specimen 8 and the platinum electrode 6 are placed inside electrolytic cell 5, with the electrolyte completely submerging the gauge length of the metal specimen to ensure that the gauge length and platinum electrode are fully in experimental condition. The platinum electrode 6 is also placed in electrolytic cell 5, parallel to the gauge length of the in-situ tensile specimen 8. The gauge length of the in-situ specimen 8 can be shaped according to different experimental requirements, with the upper and lower ends matching the clamping device. The platinum electrode 6 is connected to the anode of the DC power supply 1 with insulated copper wire, and the in-situ tensile specimen 8 is connected to the cathode of the DC power supply in the same way. The DC power supply 1 can adjust the current and voltage values ​​according to different experimental requirements.

[0033] The upper end of the in-situ tensile specimen 8 is connected to the clamping device 12 by fastening bolts. The end face of the clamping device 12 is connected and fixed to the metal connecting plate 2 and the fixing plate 13 by fastening bolts, and then connected and fixed to the nuts on the left and right symmetrical lead screw guides 7, so that the left and right lead screw nuts always remain parallel, thereby achieving the loading of tensile force through the lead screw guides 7. The host computer 14 simultaneously collects the number and time of stepper motor pulses.

[0034] The device of this invention has a simple structure, low equipment cost, simple operation, and no safety hazards. It can perform electrochemical hydrogen charging while slowly stretching the sample, effectively avoiding hydrogen leakage, and can control the hydrogen charging current density and charging time to reduce experimental errors. The device has a small overall size, making it suitable for widespread use in laboratories. It is simple and easy to operate and suitable for metal samples of different sizes and shapes.

[0035] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. An electrochemical hydrogen-charged slow strain rate in-situ tensile device, characterized in that, The device includes an electrochemical hydrogen charging unit, a sealing unit, and an in-situ stretching unit, wherein: The electrochemical hydrogen charging unit includes a DC power supply (1), a platinum electrode (6), an in-situ tensile specimen (8), and an electrolytic cell (5); the sealing unit includes a compression spring (11) and a sealing rubber ring (9); the in-situ tensile unit includes a lead screw linear guide (7), a clamping device (4), and a host computer (14). The upper structure of the electrolytic cell (5) is an electrochemical hydrogen charging unit. The platinum electrode (6) and the gauge length of the in-situ tensile specimen (8) are placed parallel to each other in the electrolytic cell and immersed in the electrolyte. The platinum electrode is connected to the anode of the DC power supply (1) by a wire, and the in-situ tensile specimen (8) is connected to the cathode of the DC power supply (1). The compression spring (11) is located in the bottom sealing structure of the electrolytic cell (5), fixed at the lower end of the in-situ tensile specimen (8), and in contact with the PVC sealing ring (10). The axial elastic force formed by the compression of the spring acts on the PVC sealing ring (10) and is transmitted to the sealing rubber ring (9), so that the lower end of the in-situ tensile specimen (8) remains sealed during the tensile process. The left and right symmetrical lead screw linear guide (7) device is connected to the metal connecting plate (2) and the fixing plate (13) respectively by fastening bolts, so that the left and right lead screw linear guides are kept parallel. The high-precision stepper motor drives the lead screw transmission to control the clamping device to stretch the in-situ tensile specimen (8).

2. The electrochemical hydrogen-charged slow strain rate in-situ tensile device according to claim 1, characterized in that, The upper and lower symmetrical clamping devices (4) are connected and fixed on the upper and lower metal connecting plates (2). The in-situ tensile specimen (8) is connected to the clamping devices (4) by fastening bolts (12).

3. The electrochemical hydrogen-charged slow strain rate in-situ tensile device according to claim 1, characterized in that, The in-situ tensile unit controls the stepper motor speed through the host computer (14) to set the sample tensile rate.

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