Device and method for testing bending stress relaxation performance of high-strength low-relaxation metal material

Abstract

The invention provides a device and a method for testing the bending stress relaxation performance of a high-strength low-relaxation metal material. The testing device mainly comprises a rigid base (1) which is provided with a vertical column (6) and a horizontal counter-force base (10); the torque measuring assembly comprises a torque sensor (2) and a clamping piece (3), the torque sensor (2) is fixed to the vertical stand column (6), and the clamping piece (3) and the torque sensor (2) are associated and form a vertical clamping mechanism; the pressure measuring assembly comprises a pressure sensor (4) and a supporting rod (5), the pressure sensor (4) is fixed to the horizontal counter-force base (10), and the supporting rod (5) and the pressure sensor (4) are associated and form a horizontal loading mechanism; the stress relaxation rate is calculated by the torque data and the pressure data. The technical problem of performance detection of the high-strength low-relaxation metal material with the tensile strength larger than or equal to 1000 MPa and the 1000-hour stress relaxation rate smaller than or equal to 3% is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of material mechanical property testing, and specifically relates to a testing device and a testing method for the bending stress relaxation performance of high-strength, low-relaxation metal materials. The present invention is particularly suitable for testing the bending stress relaxation performance of high-strength, low-relaxation metal materials with a tensile strength of ≥1000MPa and a 1000h stress relaxation rate of ≤3%. Background Art

[0002] The stress relaxation performance of metal materials is an important indicator for evaluating their stress attenuation characteristics under long-term loads and is crucial to the safety design of engineering structures. Traditional stress relaxation tests mostly use tension loading methods, which have the following drawbacks:

[0003] Insufficient stability: the tensioning device is easily affected by environmental vibrations, resulting in load fluctuations, making it difficult to meet the long-term testing requirements of high-strength, low-relaxation materials;

[0004] Limited accuracy: Traditional mechanical sensors have low resolution and cannot accurately capture tiny stress relaxation changes. They are not suitable for high-strength, low-stress relaxation alloy materials.

[0005] Applicability limitations: Existing devices are difficult to achieve bending loading modes for high-strength metal materials, and the tensile loading force is large, making testing difficult.

[0006] In view of the above problems, it is urgent to develop a bending stress relaxation test device and method with high precision, high stability and simple test process. For example, the national standard GB / T 39152-2020 mentions a bending stress relaxation test method for copper and copper alloys, which calculates the stress relaxation rate by manually measuring the bending height of the metal material. Chinese invention patent application CN118329667A discloses a device and method for measuring the low-temperature bending stress relaxation performance of metal materials. The device for measuring the low-temperature bending stress relaxation performance of metal materials includes a loading system, a fixture, a measuring system and a low-temperature environment chamber. The loading system includes a bracket and a servo electric cylinder, and the servo electric cylinder is fixedly arranged on the bracket. The top end of the fixture is fixed on the bracket, and the bottom end is used to fix one end of the sample to be tested. The measuring system includes a pressure sensor, a push rod and a downward pressure head. The pressure sensor is fixedly arranged at the front end of the telescopic rod of the servo electric cylinder, and the push rod is fixedly arranged at the center of the end of the pressure sensor away from the servo electric cylinder.

[0007] However, the above test method is unable to accurately measure the properties of high-strength, low-relaxation metal materials with a tensile strength ≥1000 MPa and a 1000h stress relaxation rate ≤3%, and the measurement accuracy does not reach above ±0.05% FS.

[0008] Therefore, there is an urgent need for a testing device and method for measuring the bending stress relaxation performance of high-strength, low-relaxation metal materials to solve the above problems. Summary of the Invention

[0009] The present invention aims to solve the technical problem that traditional stress relaxation testing devices cannot adapt to the bending loading requirements of high-strength, low-relaxation materials, and to achieve accurate measurement of the performance of high-strength, low-relaxation metal materials with a tensile strength ≥1000MPa and a 1000h stress relaxation rate ≤3%. It has the characteristics of high measurement accuracy (up to ±0.02%FS) and easy operation.

[0010] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0011] The present invention first provides a testing device for the bending stress relaxation performance of a high-strength, low-relaxation metal material, wherein the high-strength, low-relaxation metal material has a tensile strength of ≥1000 MPa and a 1000h stress relaxation rate of ≤3%. The testing device mainly comprises:

[0012] A rigid base, wherein the rigid base is provided with vertical columns and a horizontal reaction base;

[0013] a torque measurement assembly comprising a torque sensor and a clamping member, wherein the torque sensor is fixed to the vertical column, and the clamping member is associated with the torque sensor and forms a vertical clamping mechanism;

[0014] a pressure measurement assembly comprising a pressure sensor and a support rod, wherein the pressure sensor is fixed to the horizontal reaction force base, and the support rod is associated with the pressure sensor and forms a horizontal loading mechanism; and

[0015] The steel material to be tested is clamped and fixed on the torque sensor by the clamping member and presents a vertical cantilever structure. The support rod is suitable for horizontally loading the cantilever end of the steel material to be tested to a predetermined deformation amount. The torque sensor collects torque data in real time, and the pressure sensor collects pressure data in real time. The stress relaxation rate is calculated by the two data together.

[0016] Preferably, the stress relaxation rate is calculated from two data including:

[0017] The relaxation rate after 1000 hours is calculated using torque data as shown in formula (1), and the relaxation rate after 1000 hours is calculated using pressure data as shown in formula (2). The final material bending relaxation performance after 1000 hours is calculated using these two data as shown in formula (3):

[0018]

[0019] Preferably, the rigid base, vertical columns and horizontal reaction base are made of high-rigidity alloy materials, so as to be suitable for testing the bending stress relaxation properties of high-strength low-relaxation metal materials with tensile strength ≥1000MPa and 1000h stress relaxation rate ≤3%.

[0020] Preferably, the torque sensor is a cylindrical structure, including a cylindrical body and a vertical clamping piece, the inner side of the cylindrical body is fixed on the vertical column, and two groups of the clamping pieces are vertically fixed to the outer side of the cylindrical body; and the two groups of the clamping pieces are provided with bolt holes, and the clamping piece is a fixing bolt, which passes through the bolt holes on the two groups of the clamping pieces and the bolt holes on the steel to be tested to clamp and fix the steel to be tested.

[0021] Preferably, the pressure sensor is a columnar structure, one end of which is connected and fixed to the horizontal reaction force base by embedding, and the support rod abuts against the other end of the columnar structure.

[0022] Preferably, the support rod is an adjustable support rod to achieve stepless adjustment of the support length.

[0023] Preferably, the torque sensor and pressure sensor have a built-in temperature compensation module with a temperature drift coefficient of ≤0.002% FS / °C, and can perform variable temperature stress relaxation testing within a temperature range of -70°C to +300°C.

[0024] Preferably, the testing device further comprises:

[0025] a signal transmitter connected to the torque sensor and the pressure sensor, and used for converting and amplifying load data;

[0026] A digital display unit is connected to the signal transmitter and is used to display real-time torque and pressure measurement values.

[0027] Preferably, the signal transmitter has a built-in RS485 conversion module and a programmable amplifier circuit, which can convert the analog signals output by the pressure sensor and the torque sensor into digital signals and perform dynamic gain adjustment.

[0028] Preferably, the digital display unit supports real-time drawing of pressure-time curve and torque-time curve, and has a built-in data storage module, with a measurement accuracy of up to ±0.02% FS, which can achieve stable detection of 1000h bending stress relaxation performance.

[0029] The present invention further provides a method for testing the bending stress relaxation performance of a high-strength, low-relaxation metal material based on the testing device, comprising the following steps:

[0030] The steel material to be tested is clamped on the vertical column by fixing bolts and torque sensors to form a vertical cantilever structure;

[0031] Determine the initial load application gradient through finite element simulation; apply a constant bending load to the steel material to a predetermined deformation through the support rod in a displacement control mode; preferably, during loading, the constant bending load is applied by combining mechanical preload with electronic feedback closed-loop control, the initial loading stress is set to ≥0.8 times the material yield strength, and the loading error is less than ±0.5N;

[0032] The pressure data is collected in real time using a pressure sensor, the torque data is collected in real time using a torque sensor, and the signal is processed through a signal transmitter; preferably, during data collection, the pressure data and the torque data are collected continuously for 1000 hours at a sampling frequency of 0.1 Hz;

[0033] The pressure decay curve and torque decay curve are displayed in two digital display units respectively. The two data are used together to calculate the stress relaxation rate. When the error between the two data is greater than 0.01%, the pressure sensor and torque sensor need to be calibrated.

[0034] The beneficial effects of the present invention over the prior art are as follows: the present invention provides a testing device and method for the bending stress relaxation performance of high-strength, low-relaxation metal materials, which are particularly suitable for testing the bending stress relaxation performance of high-strength, low-relaxation metal materials with a tensile strength ≥1000MPa and a 1000h stress relaxation rate ≤3%. By innovatively adopting multi-source data acquisition of pressure sensors and torque sensors, the two data are used to collaboratively detect the stress relaxation performance of the material, solving the technical problems of poor stability and low measurement accuracy in traditional tensile stress relaxation performance testing. The measurement accuracy can reach as high as ±0.02%FS and the operation is simple, making it suitable for testing the bending stress relaxation performance of high-strength, low-stress relaxation steels with high measurement accuracy requirements. Specifically, it can be better understood from at least the following aspects:

[0035] (1) Traditional methods are not suitable for testing high-strength, low-relaxation materials. This device is suitable for testing the bending stress relaxation properties of high-strength, low-relaxation metal materials with a tensile strength of ≥1000 MPa and a 1000h stress relaxation rate of ≤3%.

[0036] (2) The device has the advantages of high accuracy in testing bending stress relaxation performance and easy operation through reasonable design and multi-source data acquisition;

[0037] (3) The device is equipped with a temperature compensation module inside the sensor, which can perform variable temperature stress relaxation tests in the temperature range of -70℃ to +300℃.

[0038] It should be understood that the implementation of any embodiment of the present invention does not mean that multiple or all of the above-mentioned beneficial effects must be possessed or achieved at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments or the description of the prior art. Obviously, the drawings described below are merely exemplary, and those skilled in the art can, without inventive effort, derive other implementation drawings based on the provided drawings.

[0040] The structures, proportions, sizes, etc. illustrated in this specification are intended solely to complement the contents disclosed herein and to facilitate understanding and reading by persons skilled in the art. They are not intended to limit the conditions under which the present invention may be implemented and therefore have no substantive technical significance. Any structural modifications, changes in proportions, or adjustments in sizes, provided they do not affect the efficacy and objectives of the present invention, shall remain within the scope of the technical contents disclosed herein.

[0041] Figure 1 1 is a schematic diagram of the overall structure of a testing device for measuring bending stress relaxation properties of high-strength, low-relaxation metal materials according to an embodiment of the present application;

[0042] Figure 2 2. This is a schematic diagram of the overall structure of a testing device for measuring bending stress relaxation properties of high-strength, low-relaxation metal materials according to an embodiment of the present application from another perspective;

[0043] Figure 3 The results of bending stress relaxation measurement of 40CrMoNi alloy at room temperature for 120h.

[0044] The above drawings include the following reference numerals:

[0045] 1- Rigid base; 2- Torque sensor, cylindrical body 21, clamping piece 22; 3- Clamping piece; 4- Pressure sensor; 5- Support rod; 6- Vertical column; 7- Signal transmitter; 8- Digital display unit; 9- Steel material to be tested; 10- Horizontal reaction force base.

[0046] In the various drawings, the same or corresponding reference numerals denote the same or corresponding parts. DETAILED DESCRIPTION

[0047] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention more clearly understood, the embodiments of the present invention are further described in detail below in conjunction with the embodiments and drawings. Here, the illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0048] In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "connect," "fixed," etc. should be understood broadly. For example, they may refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0049] It should be understood that the terms "comprises / comprising," "consisting of," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a product, apparatus, process, or method that includes a list of elements includes not only those elements but also, if necessary, other elements not explicitly listed, or elements inherent to such product, apparatus, process, or method. In the absence of further limitations, elements defined by the phrases "comprises / comprising," "consisting of," do not preclude the presence of additional identical elements in the product, apparatus, process, or method that includes the elements.

[0050] It should also be understood that terms such as "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device, component or structure referred to must have a specific direction, be constructed or operate in a specific direction, and should not be understood as limiting the present invention.

[0051] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature identified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0052] As mentioned in the background technology, the existing testing methods for the bending stress relaxation performance of metal materials have the problem of being unable to accurately detect high-strength, low-relaxation metal materials, especially high-strength, low-relaxation metal materials with a tensile strength ≥1000MPa and a 1000h stress relaxation rate ≤3%. The measurement accuracy does not reach above ±0.05%FS, which cannot meet the requirements.

[0053] Based on this, the present invention proposes a testing device and method for the bending stress relaxation performance of high-strength metal materials, which can well adapt to the bending loading requirements of high-strength, low-relaxation materials, and accurately measure the bending stress relaxation performance of high-strength, low-relaxation metal materials with a tensile strength ≥1000MPa and a 1000h stress relaxation rate ≤3%. It has the characteristics of high measurement accuracy (up to ±0.02%FS) and easy operation.

[0054] The following is a detailed description of the specific implementation and preferred embodiments of the testing device and method for the bending stress relaxation performance of high-strength metal materials proposed in the present invention.

[0055] Overall Figure 1-2 As shown, a testing device for the bending stress relaxation performance of high-strength, low-relaxation metal materials is exemplified, which is suitable for high-strength, low-relaxation metal materials with a tensile strength ≥1000MPa and a 1000h stress relaxation rate ≤3%. The testing device mainly includes: a rigid base 1, a torque measuring component, and a pressure measuring component, wherein the rigid base 1 serves as the base of the entire testing device, carrying relevant loading components and monitoring components, the torque measuring component is used to measure the torque load of the material during the loading process, and the pressure measuring component is used to measure the pressure load of the material during the loading process, and the stress relaxation rate is calculated jointly through the two load data to ensure that the measurement accuracy reaches above ±0.05% FS.

[0056] Specifically, the rigid base 1 is a rigid platform structure, on which vertical columns 6 and horizontal reaction bases 10 are provided. Figure 1 As shown, the vertical column 6 is fixed on one side of the rigid base 1, and the horizontal reaction base 10 is fixed on the side of the rigid base 1 adjacent to the vertical column 6, so that the vertically clamped steel material 9 to be tested can be horizontally loaded from the side.

[0057] The rigid base 1, the vertical column 6, and the horizontal reaction base 10 are fixed together. The overall device size is approximately 200mm long × 150mm wide × 3000mm high, which meets the requirements of clamping, loading and measuring the steel material 9 to be tested.

[0058] Preferably, the rigid base 1, vertical columns 6, and horizontal reaction base 10 are all made of a high-rigidity alloy material with a polished surface and anti-slip treatment. For example, they are made of medium-carbon low-alloy steel 42CrMo, which has been quenched and hardened to a Rockwell hardness of 40 HRC or higher (the measured Rockwell hardness of the material is 40-42 HRC) to ensure that the platform deformation under long-term load is less than 0.01 mm / m.

[0059] As for the torque measuring assembly and the pressure measuring assembly, the torque measuring assembly includes a torque sensor 2 and a clamping member 3, and the pressure measuring assembly includes a pressure sensor 4 and a support rod 5, wherein the torque sensor 2 is fixed on the vertical column 6, specifically on the inner side of the vertical column 6, the clamping member 3 is associated with the torque sensor 2 and forms a vertical clamping mechanism, the pressure sensor 4 is fixed on the horizontal reaction force base 10, specifically on the inner side of the horizontal reaction force base 10, and the support rod 5 is associated with the pressure sensor 4 and forms a horizontal loading mechanism.

[0060] The steel material 9 to be tested is a strip steel plate, the upper end of which is clamped and fixed on the torque sensor 2 by the clamping member 3 and presents a vertical cantilever structure, and the lower end is cantilevered. The support rod 5 is suitable for horizontally loading the cantilever end of the steel material 9 to be tested to a predetermined deformation amount from the horizontal direction. During the loading process, the torque sensor 2 collects torque data in real time, and the pressure sensor 4 collects pressure data in real time. The stress relaxation rate is calculated by the two data together.

[0061] In one embodiment, see Figure 1 、 Figure 2 The torque sensor 2 utilizes a cylindrical structure, comprising a cylindrical body 21, specifically a cylinder in this embodiment. The inner side of the cylinder is fixed to the vertical column 6, and a torque detection element is built into the cylinder. The torque sensor 2 has a range of 0-30,000 N·mm and a nonlinear error of ≤±0.02% FS.

[0062] In order to clamp the steel material 9 to be tested, the torque sensor 2 is also provided with a vertical clamping piece 22. Two groups of clamping pieces 22 are provided. The two groups of clamping pieces 22 are vertically opposite and fixed on the outside of the cylindrical body 21. Specifically, two strip steel plates can be welded and fixed on the cylindrical body 21. The upper end of the steel material 9 to be tested is clamped and fixed by the two groups of clamping pieces 22.

[0063] Preferably, to facilitate installation and disassembly, the clamping member 3 uses fixing bolts, and bolt holes are provided on the two sets of clamping plates 22. In this embodiment, two fixing bolts are specifically used, and bolt holes are provided on the upper end of the steel material 9 to be tested. The two fixing bolts pass through the bolt holes on the two sets of clamping plates 22 and the bolt holes on the steel material 9 to be tested, thereby clamping and fixing the upper end of the steel material 9 to be tested, forming a vertical cantilever structure. The fixing bolts are 12.9 grade high-strength bolts with a thread specification of M12×1.5 and a pre-tightening torque set to 50N·m±0.5%. It is easy to understand that the so-called vertical here means perpendicular to the rigid base 1 below, and can also be understood as vertical, so as to facilitate horizontal loading on the support rod 5 and the horizontal reaction base 10.

[0064] In a specific embodiment, see Figure 1 、 Figure 2The pressure sensor 4 is a cylindrical structure, specifically a circular cylinder in this embodiment. One end of the cylinder is fixed to the horizontal reaction force base 10 by embedding, ensuring accurate force transmission. The other end of the cylinder abuts one end of the support rod 5, which in turn aligns with the cantilever end of the steel material 9 to be tested, providing horizontal loading to the cantilever end. The pressure sensor 4 has a range of 0-300N and a nonlinear error of ≤±0.02%FS.

[0065] Preferably, the support rod 5 is an adjustable support rod to achieve stepless adjustment of the support length. The support rod 5 is made of 7075 aluminum alloy hollow tube (outer diameter 8mm, wall thickness 2mm).

[0066] In addition, since changes in ambient temperature will cause changes in bending stress, which in turn will cause changes in support force and torque, setting temperature compensation on the sensor can eliminate the impact of temperature changes. Therefore, the pressure sensor 4 and torque sensor 2 have built-in temperature compensation chips, and the temperature drift coefficient is ≤0.002% FS / ℃.

[0067] In a specific embodiment, see Figure 1 、 Figure 2 The test device also includes a signal transmitter 7 and a digital display unit 8. The signal transmitter 7 is connected to the torque sensor 2 and the pressure sensor 4 for converting and amplifying load data. The digital display unit 8 is connected to the signal transmitter 7 for displaying real-time torque and pressure measurement values. In practice, the signal transmitter 7 and the digital display unit 8 can be shared by the torque sensor 2 and the pressure sensor 4, or they can be provided separately. In this embodiment, one signal transmitter 7 and one digital display unit 8 are provided for each torque sensor 2 and the pressure sensor 4, respectively.

[0068] Preferably, the signal transmitter 7 has a built-in RS485 conversion module and a programmable amplifier circuit, with a maximum sampling frequency of 500Hz, and the RS485 interface transmission rate can be configured to 9600bps-115200bps. The programmable amplifier circuit has an adjustable gain, a maximum gain multiple of 1000 times, and a signal-to-noise ratio ≥80dB. It can convert the analog signal output by the pressure sensor 4 into a digital signal and perform dynamic gain adjustment.

[0069] The digital display unit 8 features a 3-inch capacitive touchscreen with a resolution of 1280×800, a minimum sampling interval of 0.1s, and real-time plotting and display of pressure-time and torque-time curves. Its measurement accuracy reaches ±0.02% FS, enabling stable testing of bending stress relaxation performance over 1000 hours. It also includes a built-in data storage module with a capacity of ≥1GB, capable of storing 100 sets of test data and supporting CSV format export. Furthermore, the data storage module utilizes a dual backup mechanism and is equipped with an uninterruptible power supply to ensure 72-hour data protection during power outages.

[0070] The method for testing bending stress relaxation performance using the testing device provided by the present invention comprises the following steps:

[0071] The first step is to clamp the steel sample (9) to the vertical column (6) using the fixing bolts and torque sensor (2) to form a vertical cantilever structure. Specifically, loosen the fixing bolts and place the steel sample (9) (200mm long, 20mm wide, and 3mm thick) on the torque sensor (2), maintaining a cantilever length of approximately 180mm. Tighten the bolts to the set torque, ensuring that the axis of the sample is parallel to the column.

[0072] In the present invention, the equivalent lever ratio of the cantilever loading structure is 1:15-1:20, which can amplify the micro-deformation of the sample into a measurable displacement, and the applicable range of the thickness of the measured material is 1mm to 5mm.

[0073] In the second step, the initial load application gradient is determined through finite element simulation; a constant bending load is applied through the support rod 5 and the steel material 9 to be tested is loaded to a predetermined deformation amount in a displacement control mode; specifically, by adjusting the length of the support rod 5, the load is loaded to a target displacement of 30 mm, and a three-dimensional contact model is established using ABAQUS with a grid size of 0.1 mm. It is calculated that when the support point of the specimen moves horizontally by 30 mm, the maximum bending stress on the surface of the specimen reaches 850 MPa, and the support force calculation result is 142 N. The error between the support force calculated by the finite element model and the measured support force is less than 0.1%.

[0074] In the third step, the pressure data (in N) is collected in real time using the pressure sensor 4, and the torque data (in N·mm) is collected in real time using the torque sensor 2, and the signal is processed through the signal transmitter 7. During the loading process, the pressure value fluctuation is monitored to be less than ±0.3N, and the torque sensor fluctuation is less than ±54N·mm. At this time, the pressure value displayed on the instrument deviates from the simulation result by less than 1.5%, and the force value obtained by dividing the cantilever length 180mm by the instrument deviates from the pressure sensor by less than 1.5%.

[0075] The sampling rate is 1 Hz in the initial stage (0-1 h), reduced to 0.1 Hz in the stable stage (1-100 h), and 0.01 Hz interval sampling is used in the long-term stage (100-1000 h) to balance the data volume and storage space.

[0076] The torque sensor 2 and the pressure sensor 4 have built-in temperature probes. When the ambient temperature changes by more than ±1°C, the compensation algorithm is automatically activated. The temperature coefficient compensation accuracy reaches 0.001% FS / °C.

[0077] The signal transmitter has four-level electromagnetic shielding, and the anti-interference ability reaches 100dB@50Hz.

[0078] The fourth step is to display the pressure decay curve and the torque decay curve in the two digital display units 8 respectively. The two data are used together to calculate the stress relaxation rate. When the error between the two data is greater than 0.01%, the pressure sensor 4 and the torque sensor 2 need to be calibrated.

[0079] In this step, the stress relaxation rate is calculated by two data:

[0080] The relaxation rate after 1000 hours is calculated using torque data as shown in formula (1), and the relaxation rate after 1000 hours is calculated using pressure data as shown in formula (2). The final material bending relaxation performance after 1000 hours is calculated using these two data as shown in formula (3):

[0081]

[0082] During the test, the digital display unit 8 will automatically record the test force values ​​of the pressure sensor 4 and the torque sensor 2; wait for the test to end and obtain test data such as time and force values. Figure 3 The results show that the device can detect data changes of 0.1N after the last digit of a small data point, as can be seen from the left vertical axis, and can detect data changes within 50N·mm from the right vertical axis, with high detection accuracy. The pressure and torque data change trends are consistent within the initial 20 hours of measurement, and the change process is stable. In addition, the sampling frequency is set high for the first 50 hours, resulting in high data density, while the sampling frequency is set low for the subsequent 70 hours, resulting in low data point density. This shows that the measurement device is stable and the sampling frequency is variable, which can realize the bending stress relaxation performance detection of high-strength, low stress relaxation rate steel with high precision requirements.

[0083] This device can perform variable temperature stress relaxation testing within a temperature range of -70°C to +300°C. The test plan involves placing the entire device, excluding the signal transmitter 7 and the digital display unit, in a -40°C low-temperature chamber or a 200°C high-temperature chamber. Experimental measurements show that the bending stress relaxation rate of 40CrNiMo alloy at -40°C over 1000 hours is 18% lower than that at room temperature, while the bending stress relaxation rate at 200°C over 10 hours is 33% higher than that at room temperature.

[0084] On-site calibration was performed using a third-class standard dynamometer, with linear correction performed at 50 N, 200 N, and 500 N. After calibration, the system accuracy reached 0.02, with an annual stability of <0.03% FS.

[0085] For 40CrNiMo alloy (tensile strength 1250 MPa), the initial load was set at 0.8 times the material's yield strength (1100 MPa). After 1000 hours, the bending stress relaxation rate was measured to be 2.3%, with a data fluctuation of <±0.02%.

[0086] 40CrNiMo alloy was tested continuously for 3000h, and the system drift was less than 0.05%FS / 1000h, proving that the test device meets the requirements of ultra-long-term stress relaxation testing.

[0087] In the present invention, high-strength, low-relaxation metal materials include but are not limited to: maraging steel, β-titanium alloy, nickel-based high-temperature alloy, etc.

[0088] The test method shows that within a 1000-hour test period, system drift is less than 0.02% FS. Since low-stress relaxation materials typically have a stress relaxation rate of less than 3% over 1000 hours, assuming a measured result of 1% but a system drift of 0.5%, the true stress relaxation rate is 1.5%. Therefore, smaller system drift means smaller errors.

[0089] Compared with traditional tension testing devices, energy consumption is reduced by 80%, test efficiency is increased by more than 3 times, and measurement accuracy can reach ±0.02% FS.

[0090] In summary, the testing device and testing method provided by the present invention are suitable for the bending stress relaxation performance testing of high-strength, low-relaxation metal materials with a tensile strength ≥1000MPa, an initial loading stress set to ≥0.8 times the material yield strength, and a stress relaxation rate ≤3%. By simultaneously detecting the pressure and torque in the system, multi-source data coordination detection of the material stress relaxation performance is achieved, and the measurement accuracy can reach as high as ±0.02%FS.

[0091] Although several specific implementation details are included in the above discussion, these should not be construed as limiting the scope of the present invention. Certain features described in the context of separate embodiments may also be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation may also be implemented in multiple implementations individually or in any suitable sub-combination.

Claims

1. A device for testing the bending stress relaxation performance of high-strength and low-relaxation metal materials, characterized in that: The high-strength, low-relaxation metal material has a tensile strength of ≥1000 MPa and a stress relaxation rate of ≤3% after 1000 h. The testing device mainly includes: A rigid base (1), wherein the rigid base (1) is provided with a vertical column (6) and a horizontal reaction base (10); A torque measurement assembly comprising a torque sensor (2) and a clamping member (3), wherein the torque sensor (2) is fixed on the vertical column (6), and the clamping member (3) is associated with the torque sensor (2) and forms a vertical clamping mechanism; A pressure measurement assembly comprising a pressure sensor (4) and a support rod (5), wherein the pressure sensor (4) is fixed on the horizontal reaction force base (10), and the support rod (5) is associated with the pressure sensor (4) and forms a horizontal loading mechanism; and The steel material (9) to be tested is clamped and fixed on the torque sensor (2) by the clamping member (3) and presents a vertical cantilever structure. The support rod (5) is suitable for horizontally loading the cantilever end of the steel material (9) to be tested to a predetermined deformation amount. The torque sensor (2) collects torque data in real time, and the pressure sensor (4) collects pressure data in real time. The stress relaxation rate is calculated by combining the two data.

2. The testing device according to claim 1, wherein: The stress relaxation rate is calculated by two data including: The relaxation rate after 1000 hours is calculated using torque data as shown in formula (1), and the relaxation rate after 1000 hours is calculated using pressure data as shown in formula (2). The final material bending relaxation performance after 1000 hours is calculated using these two data as shown in formula (3):

3. The testing device according to claim 1, wherein: The rigid base (1), vertical column (6) and horizontal reaction force base (10) are made of high-rigidity alloy material, and are suitable for testing the bending stress relaxation performance of high-strength low-relaxation metal materials with a tensile strength of ≥1000MPa and a 1000h stress relaxation rate of ≤3%.

4. The testing device according to claim 1, wherein: The torque sensor (2) is a columnar structure, comprising a columnar body (21) and a vertical clamping piece (22), wherein the inner side of the columnar body (21) is fixed on the vertical column (6), and two groups of the clamping pieces (22) are fixed on the outer side of the columnar body (21) in a vertically opposed manner; and bolt holes are provided on the two groups of the clamping pieces (22), and the clamping member (3) is a fixing bolt, which passes through the bolt holes on the two groups of the clamping pieces (22) and the bolt holes on the steel material (9) to be tested to clamp and fix the steel material (9) to be tested.

5. The testing device according to claim 1, wherein: The pressure sensor (4) is a columnar structure, one end of which is connected and fixed to the horizontal reaction force base (10) by embedding, and the support rod (5) abuts against the other end of the columnar structure.

6. The testing device according to claim 1, wherein: The support rod (5) is an adjustable support rod to achieve stepless adjustment of the support length.

7. The testing device according to claim 1, characterized in that The torque sensor (2) and the pressure sensor (4) have built-in temperature compensation modules, with a temperature drift coefficient of ≤0.002% FS / °C, and are capable of performing variable temperature stress relaxation tests within a temperature range of -70°C to +300°C.

8. The testing device according to claim 1, wherein: The test setup also includes: a signal transmitter (7), connected to the torque sensor (2) and the pressure sensor (4), for converting and amplifying load data; A digital display unit (8) is connected to the signal transmitter (7) and is used to display real-time torque and pressure measurement values.

9. The testing device according to claim 8, characterized in that: The signal transmitter (7) has a built-in RS485 conversion module and a programmable amplifier circuit, which can convert the analog signals output by the pressure sensor (4) and the torque sensor (2) into digital signals and perform dynamic gain adjustment; The digital display unit (8) supports real-time drawing of pressure-time curve and torque-time curve, and has a built-in data storage module. The measurement accuracy can reach ±0.02% FS, and can achieve stable detection of bending stress relaxation performance for 1000 hours.

10. A method for testing the bending stress relaxation performance of high-strength, low-relaxation metal materials based on the testing device according to any one of claims 1 to 9, characterized in that: The following steps are involved: The steel material (9) to be tested is clamped on the vertical column (6) by fixing bolts and a torque sensor (2) to form a vertical cantilever structure; The initial load application gradient is determined by finite element simulation; a constant bending load is applied through the support rod (5) and the steel material (9) to be tested is loaded to a predetermined deformation amount in a displacement control mode; preferably, during loading, the constant bending load is applied by combining mechanical preload and electronic feedback closed-loop control, the initial loading stress is set to ≥0.8 times the yield strength of the material, and the loading error is less than ±0.5N; The pressure data is collected in real time using the pressure sensor (4), the torque data is collected in real time using the torque sensor (2), and the signal is processed by the signal transmitter (7); preferably, when collecting data, the pressure data and the torque data are collected together at a sampling frequency of 0.1 Hz for 1000 hours of load attenuation data; The pressure decay curve and the torque decay curve are displayed respectively on two digital display units (8), and the two data are used together to calculate the stress relaxation rate. When the error between the two data is greater than 0.01%, the pressure sensor (4) and the torque sensor (2) need to be calibrated.

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