Calibration Method and System for Horizontal Friction Force of Dynamic Compression-Shear Testing Machine

Abstract

This application discloses a calibration method and system for the horizontal friction force of a dynamic compression-shear testing machine, relating to the field of equipment calibration. This application uses standard simulated specimens independent of the seismic isolation bearings as carriers, preparing at least three standard simulated specimens with consistent mechanical properties, thereby reducing friction force separation deviations caused by the specimens' inherent characteristics at the source. Using test data from three sets of double-shear configurations under various vertical pressures, a system of equations is constructed to calculate the standard horizontal friction force of a single standard simulated specimen under different vertical pressures. A relationship curve between the inherent horizontal friction force of the standard simulated specimen and the vertical pressure is established through fitting analysis. Then, under the same set vertical pressure, a single-shear test is conducted on each standard simulated specimen. Based on the relationship curve, the horizontal friction force and horizontal friction coefficient of the rolling platform of the dynamic compression-shear testing machine under the set vertical pressure are obtained, improving the accuracy, stability, and reliability of the calibration results.

Description

Technical Field

[0001] This application relates to the field of equipment calibration technology, specifically to a calibration method and system for the horizontal friction force of a dynamic compression-shear testing machine. Background Technology

[0002] Seismic isolation bearings, as a type of seismic isolation device, are widely used in important infrastructure such as bridges, especially in critical service buildings such as airports, schools, and hospitals. After the installation of seismic isolation bearings, the horizontal deformation of the bearings can effectively absorb the energy of seismic shear waves, reduce the impact of earthquakes on the superstructure, and effectively improve the seismic resistance of the building structure. Whether the various parameters of the seismic isolation bearings meet the requirements needs to be tested using a compression-shear testing machine. Among them, the dynamic compression-shear testing machine is a specialized device for testing the horizontal dynamic mechanical properties of seismic isolation bearings, and the accuracy and reliability of its force values ​​directly affect the validity of the bearing test results.

[0003] Dynamic compression-shear testing machines are widely used in testing the mechanical properties of engineering materials such as rubber bearings, seismic isolation devices, and dampers. In these tests, the specimens typically undergo reciprocating shear motion in the horizontal direction while being subjected to enormous vertical pressure. To simulate realistic boundary conditions and bear huge vertical loads, the lower loading platform of the testing machine is usually designed as a rolling platform with rollers, sliders, or linear guides. However, the rolling platform inevitably generates horizontal frictional resistance during movement. This frictional resistance is superimposed on the specimen's true restoring force, causing distortion of key parameters such as the measured hysteresis curve, equivalent stiffness, and damping ratio. Therefore, precise calibration is essential.

[0004] Traditional calibration methods include the no-load operation method, the commutation point mutation method, and the empirical estimation method. The no-load operation method measures friction without installing a test specimen. This method ignores the changes in the contact state, force distribution, and motion trajectory of the rolling platform after the specimen is installed (i.e., the "load effect"), leading to a significant deviation between the friction measured under no-load conditions and the friction under actual load. The commutation point mutation method is based on a single-specimen test curve, estimating friction by extracting the force mutation at the instant the velocity is zero. This method is extremely sensitive to sensor noise and control system overshoot, and it is difficult to distinguish between the friction mutation and the nonlinear viscoelastic hysteresis of the high-damped specimen itself, resulting in large fluctuations and poor repeatability in the calculation results. The empirical estimation method estimates based on theoretical formulas or fixed coefficients. It cannot reflect the real-time changes in the equipment's condition due to guide rail wear, lubrication aging, etc., as the equipment ages over time, and its accuracy cannot meet high-standard metrological requirements.

[0005] Therefore, the traditional calibration method for dynamic compression-shear testing machines has the problems of relying on specimen characteristics and inaccurate friction force separation. Summary of the Invention

[0006] The purpose of this application is to provide a calibration method and system for the horizontal friction force of a dynamic compression-shear testing machine, in order to solve the problems of traditional calibration methods for dynamic compression-shear testing machines that rely on specimen characteristics and have inaccurate friction force separation.

[0007] To achieve the above objectives, the first aspect of this application provides a method for calibrating the horizontal friction force of a dynamic compression-shear testing machine, comprising:

[0008] Prepare at least three standard simulated specimens with identical mechanical properties, the standard simulated specimens being independent of the seismic isolation bearing;

[0009] The three standard simulated specimens were paired up and assembled with rigid frame components to form three sets of double shear configurations. Each set of double shear configurations was then placed on a double shear compression shear testing machine and horizontal shear tests were conducted under various vertical pressures to obtain three sets of double shear resultant force data.

[0010] Based on the physical property that the internal friction forces cancel each other out in the double-shear configuration, a set of equations is constructed from the three sets of double-shear resultant force data to calculate the standard horizontal friction force of a single standard simulated specimen under different vertical pressures. The relationship curve between the inherent horizontal friction force and the vertical pressure of the standard simulated specimen is established through fitting analysis. Each standard simulated specimen is individually installed on the rolling platform of the dynamic compression-shear testing machine to be calibrated to form a single-shear configuration. Horizontal shear tests are performed sequentially under a set vertical pressure to obtain the single-shear measured data corresponding to each standard simulated specimen.

[0011] Based on the relationship curve between the inherent horizontal friction force and the vertical pressure, the target inherent horizontal friction force corresponding to each of the standard simulated specimens under the set vertical pressure is calculated. Based on the single shear test data of each of the standard simulated specimens and the target inherent horizontal friction force, the horizontal friction force and horizontal friction coefficient of the rolling platform of the dynamic compression-shear testing machine under the set vertical pressure are calculated.

[0012] A second aspect of this application provides a calibration system for the horizontal friction force of a dynamic compression-shear testing machine, comprising:

[0013] Rigid frame components;

[0014] Three standard simulated specimens with identical mechanical properties are configured to be paired in pairs and assembled with the rigid frame assembly to form three independent double shear configurations, or to be individually mounted on the rolling platform of the dynamic compression-shear testing machine to form a single shear configuration.

[0015] The memory is configured to store instructions; and

[0016] The processor is configured to retrieve the instructions from the memory and, when executing the instructions, to implement the above-described method for calibrating the horizontal friction force of the dynamic compression-shear testing machine.

[0017] The beneficial effects of this application are:

[0018] This application uses standard simulated specimens independent of seismic isolation bearings as carriers to prepare at least three standard simulated specimens with consistent mechanical properties. First, this application eliminates the need for seismic isolation bearings, abandoning the traditional calibration method that uses the tested seismic isolation bearing as the measurement benchmark and relies on the mechanical properties of the bearing's linear elasticity. This reduces frictional force separation deviations caused by the specimen's own characteristics from the source and improves the universality and scalability of the calibration method. Second, using test data from three sets of double-shear configurations under various vertical pressures, a system of equations is constructed to calculate the standard horizontal frictional force of a single standard simulated specimen under different vertical pressures. A relationship curve between the inherent horizontal frictional force and vertical pressure of the standard simulated specimen is established through fitting analysis. This relationship curve provides a dynamic benchmark for subsequent tests across the entire range, reducing systematic errors caused by treating the specimen's frictional force as a constant. Then, under the same set vertical pressure, each standard simulated specimen is independently subjected to horizontal shear tests, obtaining the measured single-shear data for each standard simulated specimen. Based on the relationship curve between inherent horizontal friction and vertical pressure, the measured single-shear data of the standard simulated specimen is compared with the corresponding inherent horizontal friction of the target specimen to obtain the horizontal friction and horizontal friction coefficient of the rolling platform of the dynamic compression-shear testing machine under the set vertical pressure. Based on a multiple independent verification mechanism, misjudgments caused by installation deviations of individual specimens, local surface defects, or fluctuations in a single test are effectively reduced, improving the accuracy, stability, and reliability of the calibration results.

[0019] Other features and advantages of this application will be described in detail in the following detailed description section. Attached Figure Description

[0020] Figure 1 This is a top view of a standard simulation specimen provided in an embodiment of this application;

[0021] Figure 2 This is a side view of a standard simulated specimen provided in an embodiment of this application;

[0022] Figure 3 This is a schematic diagram of a double-shear configuration provided in an embodiment of this application;

[0023] Figure 4 This is a structural schematic diagram of a single-shear configuration provided in an embodiment of this application;

[0024] Figure 5This is a schematic flowchart illustrating a calibration method for the horizontal friction force of a dynamic compression-shear testing machine provided in an embodiment of this application.

[0025] Figure 6 This is a schematic diagram of the relationship curve between inherent horizontal friction force and vertical pressure provided in the embodiments of this application;

[0026] Figure 7 This is a schematic diagram of the relationship curve between the inherent horizontal friction coefficient and vertical pressure provided in the embodiments of this application.

[0027] Explanation of reference numerals in the attached figures

[0028] 100. Standard simulated specimen; 101. Lower base; 102. Upper pressure plate; 103. Mirror stainless steel plate; 104. PTFE sliding plate; 105. Silicone grease storage tank; 106. Side guide mechanism; 200. Rigid frame assembly; 201. Upper connecting plate; 202. Lower connecting plate; 203. Middle connecting plate; 300. Rolling platform. Detailed Implementation

[0029] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0030] In the description of this application, it should be understood that 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 indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified. Details are set forth in the following description for illustrative purposes. It should be understood that those skilled in the art will recognize that this application can be implemented without using these specific details. In other instances, well-known structures and processes will not be described in detail to avoid unnecessarily obscuring the description of this application. Therefore, this application is not intended to be limited to the embodiments shown, but rather to be consistent with the broadest scope of the principles and features disclosed herein.

[0031] To address the difficulty in calibrating the horizontal friction force of the rolling platform in traditional single-shear dynamic compression-shear testing machines, this application provides a dedicated calibration system for the horizontal friction force of such machines. This system offers stable friction force output and high measurement repeatability. The calibration system may include a rigid frame assembly, three standard simulated specimens with identical mechanical properties, a memory, and a processor. The memory is configured to store instructions. The processor is configured to retrieve instructions from the memory and, when executing the instructions, implement any of the horizontal friction force calibration methods for dynamic compression-shear testing machines described in this application.

[0032] The standard simulation specimen is a dedicated calibration standard independent of the seismic isolation bearing, which can reduce the interference of the nonlinear mechanics of the seismic isolation bearing itself on the calibration results. Independent of the seismic isolation bearing means that the standard simulation specimen is a standardized component designed specifically for calibration. Its material properties (such as friction coefficient stability), geometric dimensions, and mechanical response are all strictly screened and controlled, unlike the test object (compression-shear testing machine). This reduces the systematic errors introduced by the bearing nonlinearity, hysteresis characteristics differences, and individual discreteness when using the compression-shear testing machine itself as a reference in traditional methods.

[0033] Figure 1 This is a top view schematic diagram of a standard simulated specimen provided in an embodiment of this application. For example... Figure 1 As shown, the standard simulation specimen 100 is a sliding friction device. The base material is 45# steel. It consists of two main parts: a lower base 101 and an upper pressure plate 102. The lower base 101 is larger than the upper pressure plate in the length direction (x-axis), which can ensure that the upper pressure plate 102 does not come off when sliding along the x-axis. A hoisting hole is reserved at each of the four corners of the lower base 101 for easy hoisting.

[0034] Figure 2 This is a side view of a standard simulation specimen 100 provided in an embodiment of this application. Figure 2 As shown, a mirror-finished stainless steel plate 103 is embedded in the upper surface of the lower base 101, and a high-strength PTFE sliding plate 104 is embedded in the lower surface of the upper pressure plate 102. The sliding plate surface has circular recesses, i.e., silicone grease storage grooves 105. Silicone grease is applied to the PTFE sliding plate surface during assembly, and during use, the grease is stored in the grooves, ensuring constant lubrication during sliding. The sides of the lower base 101 and the upper pressure plate 102 form a cooperating side guide mechanism 106. To reduce side friction, this guide mechanism is made of linear guide rails. In this embodiment, three standard simulation test pieces are required, which can be sequentially labeled as the first test piece, the second test piece, and the third test piece. The first, second, and third test pieces are unique identifiers representing the standard simulation test pieces, for example, they can be numbered A, B, and C.

[0035] In this embodiment, three standard simulated specimens are configured to be paired in pairs and assembled with a rigid frame assembly to form three independent double-shear configurations, or individually mounted on the rolling platform of a dynamic compression-shear testing machine to form a single-shear configuration. The rigid frame assembly may include an upper connecting plate, a lower connecting plate, and an intermediate connecting plate, used to assemble two standard simulated specimens into a double-shear configuration, ensuring that the two standard simulated specimens are subjected to symmetrical forces and consistent deformations during the double-shear test, and that their own rigidity can negligibly mitigate the influence of deformation, thus avoiding the introduction of additional mechanical errors.

[0036] The double-shear configuration is a test configuration formed by symmetrically clamping two standard simulated specimens between the upper connecting plate and the middle connecting plate, and the middle connecting plate and the lower connecting plate, of a rigid frame assembly. The core physical characteristic of this configuration is that the internal frictional forces cancel each other out, outputting only the sum of the standard horizontal frictional forces of the two standard simulated specimens. The standard horizontal frictional force is the inherent horizontal frictional force generated by the standard simulated specimen itself under a set vertical pressure, without any external frictional interference. It is obtained from the double-shear test and is the core reference value for calibration. Figure 3 As shown, Figure 3 This is a structural schematic diagram of a double-shear configuration provided in an embodiment of this application. The double-shear configuration may include an upper connecting plate 201, a lower connecting plate 202, and a middle connecting plate 203 of a rigid frame assembly 200, as well as two standard simulation specimens 100. The standard simulation specimens 100 are paired up and subjected to a double-shear test on a pressure shear machine. In one example, the temperature fluctuation during the test can be controlled within 2°C. For example, the upper and lower standard simulation specimens 100 are labeled A and B, respectively. A and B are not distinguished by their position. During the test, the x-axis direction of the standard simulation specimens 100 needs to be parallel to the movement direction of the middle connecting plate 203, and the horizontal force sensor measuring T1 needs to be calibrated according to the predicted friction range before the test to ensure the accuracy of the force value.

[0037] The single shear configuration is a test configuration in which a single standard simulated specimen is placed flat on the rolling platform of the dynamic compression-shear testing machine to be calibrated, and the upper connecting plate fixed to the dynamic compression-shear testing machine is attached to it. The force value collected under this configuration is the superposition value of the standard horizontal friction force of the standard simulated specimen itself and the horizontal friction force of the rolling platform of the testing machine. Figure 4 This is a structural schematic diagram of a single-shear configuration provided in an embodiment of this application. Figure 4 As shown, each standard simulated specimen 100 can be subjected to a single shear test on a dynamic compression-shear testing machine. The temperature during the test is consistent with that of the double shear test, and the fluctuation is controlled within 2℃. Figure 4In the test, the upper connecting plate 201 is fixed horizontally, while the rolling platform 300 can roll left and right. During the test, the x-axis direction of the standard simulated specimen must be parallel to the movement direction of the rolling platform 300. Furthermore, the horizontal force sensor of the dynamic compression-shear testing machine must be calibrated before the test to ensure the accuracy of the single-shear test data. The single-shear test data is the stable horizontal force value collected during the single-shear test, under the same vertical pressure as the double-shear test, when the rolling platform 300 moves the standard simulated specimen 100. This value includes the frictional interference component of the rolling platform 300.

[0038] Based on the above calibration system, a calibration method is provided that uses three standard simulated specimens to perform multiple measurements in pairs using a static compression-shear testing machine under a specific vertical pressure. This allows for the acquisition of the horizontal friction force of a single standard simulated specimen under a specific vertical pressure. Furthermore, a standard simulated specimen with known friction force is used to obtain the horizontal friction force and friction coefficient of a dynamic compression-shear testing machine. This calibration method provides a repeatable calibration device and method, solving the problem of difficult measurement and calibration of the horizontal friction force of a dynamic compression-shear testing machine, and improving the measurement accuracy of a single-shear dynamic compression-shear testing machine. Moreover, this calibration method uses readily available materials, has a relatively simple operation process, does not require disassembly of the rolling platform of the equipment, and is highly efficient, reliable, and accurate. A detailed description follows.

[0039] Figure 5 This is a schematic flowchart illustrating a calibration method for the horizontal friction force of a dynamic compression-shear testing machine provided in an embodiment of this application. Figure 5 As shown, this calibration method may include steps 501-505, which will be described in detail below.

[0040] Step 501: Prepare at least three standard simulated specimens with consistent mechanical properties, independent of the seismic isolation bearing. Consistent mechanical properties mean that under the same working conditions (same vertical pressure, same sliding speed), the deviation of the horizontal friction force generated by these three specimens is controlled within a very small preset threshold (e.g., <2%), ensuring the effectiveness of subsequent multiple verifications.

[0041] Step 502: Pair the three standard simulated specimens together and assemble them with the rigid frame components to form three sets of double shear configurations. Place each set of double shear configurations on a double shear compression shear testing machine in sequence and conduct horizontal shear tests under various vertical pressures to obtain three sets of double shear resultant force data.

[0042] Each pair of double-shear configurations was sequentially mounted onto a high-precision double-shear compression-shear testing machine, which served as the reference device. Then, a series of gradient vertical pressures were set, covering the commonly used operating range of the testing machine to be calibrated. Horizontal shear tests were performed under each level of vertical pressure, and the readings of the horizontal force sensor were recorded, thus obtaining three sets of double-shear resultant force data for different pairings. The double-shear resultant force data is the stable horizontal force value collected during the double-shear test when the double-shear configurations experience relative sliding under the set vertical pressure. It is the superposition of the standard horizontal friction forces of two standard simulated specimens, without interference from testing machine friction.

[0043] Step 503: Based on the physical property that the internal friction forces cancel each other out in the double shear configuration, construct a set of equations from the three sets of double shear resultant force data, calculate the standard horizontal friction force of a single standard simulated specimen under different vertical pressures, and establish the relationship curve between the inherent horizontal friction force and vertical pressure of the standard simulated specimen through fitting analysis.

[0044] Due to symmetrical superposition and the elimination of external interference, the double-shear configuration possesses the physical characteristic of mutually canceling internal frictional forces. Using three sets of double-shear resultant force data, a system of equations is constructed. By solving this system under a specific vertical pressure, the standard horizontal frictional force of a single standard simulated specimen under that vertical pressure can be accurately separated. Next, by traversing all tested vertical pressure points, multiple data pairs consisting of vertical pressure and inherent horizontal frictional force are obtained. Fitting analysis of these data pairs establishes a relationship curve between inherent horizontal frictional force and vertical pressure. This relationship curve serves as a fingerprint characteristic of the standard simulated specimen, characterizing the variation of the standard horizontal frictional force of the standard simulated specimen with vertical pressure, and is used to quickly query the target standard horizontal frictional force of the device under any vertical pressure.

[0045] By fitting the established relationship curve between inherent horizontal friction and vertical pressure, the crude assumption of treating the specimen friction as a constant or a simple linear proportion is abandoned. This relationship curve can truly reflect the nonlinear variation law of inherent horizontal friction under different pressures, making the target inherent horizontal friction retrieval under any set vertical pressure more accurate, thus improving the accuracy of the final calibration results.

[0046] Step 504: Install each standard simulated specimen individually on the rolling platform of the dynamic compression-shear testing machine to be calibrated to form a single shear configuration. Perform horizontal shear tests sequentially under the set vertical pressure to obtain the single shear test data corresponding to each standard simulated specimen.

[0047] Specifically, under a set vertical pressure, horizontal shear tests can be performed on three standard simulated specimens sequentially, and the readings of the horizontal force sensor of the testing machine to be calibrated can be recorded to obtain the single shear test data. At this time, the single shear test data is a mixed value, which includes both the inherent friction force of the standard simulated specimen itself and the unknown friction force of the rolling platform of the testing machine to be calibrated.

[0048] Step 505: Based on the relationship curve between inherent horizontal friction and vertical pressure, calculate the target inherent horizontal friction corresponding to each standard simulated specimen under the set vertical pressure. Based on the single shear test data of each standard simulated specimen and the target inherent horizontal friction, calculate the horizontal friction and horizontal friction coefficient of the rolling platform of the dynamic compression-shear testing machine under the set vertical pressure.

[0049] Specifically, the difference principle can be used to subtract the measured single-shear force of each standard simulated specimen from the inherent horizontal friction force of the target, thus obtaining the horizontal friction force of the rolling platform. The horizontal friction coefficient is then calculated based on this rolling platform friction force. Since there are three standard simulated specimens, three calculated values ​​of horizontal friction force can be obtained. By comparing the dispersion of these three values, the reliability of the test can be determined. Finally, the average value or weighted average value is taken as the final calibration result for the horizontal friction force and horizontal friction coefficient of the rolling platform of the dynamic compression-shear testing machine to be calibrated.

[0050] Traditional calibration methods struggle to distinguish between specimen friction and equipment friction. By employing a double-shear cross-calibration mechanism, a relationship curve for a standard simulated specimen is now calibrated in an environment free from equipment friction interference. This curve is then used to precisely extract the friction force of the rolling platform from single-shear measured data. This strategy of first calibrating the baseline and then performing differential subtraction solves the challenge of accurately separating and calibrating the friction force of low-friction coefficient equipment under high vertical pressure.

[0051] This application uses standard simulated specimens independent of seismic isolation bearings as carriers to prepare at least three standard simulated specimens with consistent mechanical properties. This application does not require the use of seismic isolation bearings, abandoning the calibration method in traditional technology that uses the seismic isolation bearing under test as the measurement benchmark and relies on the mechanical properties of the bearing such as linear elasticity. This reduces the frictional separation deviation caused by the characteristics of the specimen itself from the source, and improves the universality and scalability of the calibration method.

[0052] Secondly, using test data from three sets of double-shear configurations under various vertical pressures, a system of equations was constructed to calculate the standard horizontal friction force of a single standard simulated specimen under different vertical pressures. Through fitting analysis, a relationship curve between the inherent horizontal friction force and vertical pressure of the standard simulated specimen was established. This relationship curve provides a dynamic benchmark across the entire testing range, reducing systematic errors caused by treating the specimen's friction force as a constant.

[0053] Then, under the same set vertical pressure, each standard simulated specimen was independently subjected to a horizontal shear test, and the single-shear measured data of each standard simulated specimen was obtained. Based on the relationship curve between inherent horizontal friction and vertical pressure, the single-shear measured data of the standard simulated specimen was compared with the corresponding inherent horizontal friction of the target specimen to obtain the horizontal friction force and horizontal friction coefficient of the rolling platform of the dynamic compression-shear testing machine under the set vertical pressure. Based on the multiple independent verification mechanism, misjudgments caused by installation deviations of individual specimens, local surface defects, or fluctuations in a single test were effectively reduced, improving the accuracy, stability, and reliability of the calibration results.

[0054] Before step 502, the process includes screening and labeling standard simulated specimens. Specifically, multiple candidate specimens are first subjected to sliding tests under a low-friction environment, and sliding friction data for each candidate specimen is collected under a set vertical pressure. A low-friction environment refers to a test condition with minimal background interference. Under this environment, the additional friction introduced by the test equipment is negligible, thus ensuring that the collected data accurately reflects the frictional characteristics of the candidate specimens themselves.

[0055] For example, prepare several (e.g., 5-10) preliminary processed candidate specimens. Set up or select a low-friction testing environment (e.g., using an air-bearing platform, a high-precision linear guide table, or a calibrated high-grade double-shear testing machine) to ensure that the background friction of the testing environment is much smaller than the friction of the specimen itself (e.g., background friction ratio <1%), to eliminate environmental interference. Place each candidate specimen sequentially in this environment and perform a reciprocating sliding test under a set vertical pressure (usually a typical pressure value within the calibration range, such as 10MPa or 20MPa). Collect and record the sliding friction data (including peak friction, average friction, and fluctuation curve) of each candidate specimen in real time.

[0056] Then, three candidate specimens with sliding friction deviations less than or equal to the set deviation, no jamming during sliding, and smooth operation of the guiding mechanism were selected as standard simulation specimens with consistent mechanical properties. The set deviation refers to a predefined allowable error range, serving as a quantitative benchmark for measuring the consistency of mechanical properties. Only specimens falling within this range are considered homogeneous, reducing the possibility of subsequent equation set solutions failing or errors being amplified due to excessive individual differences in specimens. Jamming refers to the discontinuous phenomenon of motion—stopping—sudden sliding—and then stopping again during the relative sliding process of the friction pair, caused by microscopic surface irregularities, poor lubrication, or excessively tight guiding mechanism. Jamming causes drastic fluctuations in friction force data, failing to represent stable friction characteristics, and is therefore a veto item in the screening process.

[0057] Specifically, based on the collected data, a rigorous screening logic can be implemented to retain only three candidate specimens that meet the following dual criteria as the final standard simulation specimens. First, quantitative indicators are used to calculate the average sliding friction force of all candidate specimens under the same working conditions. Specimens with sliding friction force values ​​deviating from the mean value less than or equal to a set deviation (e.g., ±2% or ±3%) are selected, ensuring high consistency in material friction coefficient, surface roughness, and lubrication status among the selected specimens. Then, qualitative indicators are used to observe the mechanical curve waveform and physical motion state during the sliding process. Any specimens exhibiting jamming, sudden changes in friction force, or fluctuations are eliminated. Specimens with unsmooth operation, abnormal noise, or resistance in the guiding mechanism (linear guide) are also eliminated. The three final selected specimens must ensure smooth sliding without jerking throughout the entire stroke, ensuring that the measured friction force originates purely from the friction pair and not from mechanical assembly defects.

[0058] Next, the three standard simulation specimens are sequentially labeled as Specimen A, Specimen B, and Specimen C. The three selected standard simulation specimens are then physically labeled and registered. For example, they are named Specimen A (First Specimen), Specimen B (Second Specimen), and Specimen C (Third Specimen). This labeling will be used throughout all subsequent steps (double-scissor pairing, single-scissor testing, and data processing) to ensure accurate tracking of the data contribution of each individual specimen during equation construction, achieving data traceability.

[0059] The solution to the equations is highly dependent on the uniformity of the data from the three specimens. If the frictional forces between the specimens differ too much (high dispersion), even minor measurement noise can be amplified during the solution process, leading to distortion of the standard frictional force calculation results for a single specimen. Through rigorous consistency screening, it was ensured that the three unknowns were of the same order of magnitude and uniformly distributed, greatly improving the numerical stability and solution accuracy of the equations. A smooth and unobstructed qualitative screening effectively eliminated abnormal specimens caused by processing defects, improper assembly, or lubrication failure. This ensured that the subsequently measured frictional force data originated entirely from the frictional characteristics of the materials themselves (PTFE sliding plate and mirror-finished stainless steel), rather than mechanical structural fault noise, guaranteeing the purity and reliability of the calibration benchmark. The specimens were uniquely marked with first, second, and third identifiers, establishing a clear data traceability chain. In subsequent analysis, if an anomaly is found in a set of double-shear data, the specific specimen can be quickly located, facilitating cause investigation or data weighting processing, thus improving the controllability and rigor of the experimental process. This step transforms ordinary machined parts into metrological-grade standard simulation specimens. The specimens, verified in a low-friction environment and rigorously screened, exhibit highly predictable and reproducible mechanical behavior.

[0060] In step 502, for each double-shear configuration, two standard simulated specimens are clamped between the upper connecting plate and the middle connecting plate, and between the middle connecting plate and the lower connecting plate, respectively. Specifically, in the first clamping layer, one of the standard simulated specimens (e.g., "first specimen") is placed between the lower surface of the upper connecting plate and the upper surface of the middle connecting plate, with the lower base of the specimen fixed to the middle connecting plate and the upper pressure plate fixed to the upper connecting plate (or vice versa, depending on the specific guide mechanism design), ensuring that the specimen is firmly clamped and there is no relative slippage (except for the designed sliding surface). In the second clamping layer, another standard simulated specimen (e.g., "second specimen") is placed between the lower surface of the middle connecting plate and the upper surface of the lower connecting plate. At this time, the middle connecting plate acts as a common force-bearing component, simultaneously driving the movement of both upper and lower specimens, forming a typical "sandwich" double-shear structure.

[0061] Then, the installation position of each double shear configuration is adjusted so that the shear center lines of the two standard simulation specimens in each double shear configuration are coaxial in the vertical direction and symmetrically arranged about the intermediate connecting plate in the horizontal shear direction, so as to ensure that the geometric boundary conditions of the three double shear configurations are consistent.

[0062] The shear centerline is an imaginary straight line passing through the geometric center of the friction pair (the contact surface between the PTFE sliding plate and the mirror-finished stainless steel plate), and it is also the axis along which the horizontal shear force mainly acts. In a double-shear configuration, it is ideal for the shear centerlines of the upper and lower standard simulated specimens to coincide. Coaxiality means that the shear centerlines of the upper and lower standard simulated specimens lie on the same vertical straight line. This is crucial for eliminating the second-order bending moment effect. If they are not coaxial, the vertical load will generate an additional bending moment, causing the pressure distribution on the friction surface to be trapezoidal rather than uniform, severely affecting the accuracy of friction force measurement.

[0063] In one example, a high-precision laser plumb line or a plumb line can be used to project a beam through the central region of the upper, middle, and lower connecting plates. The relative horizontal positions of the three connecting plates are finely adjusted so that the friction pair center of the upper specimen and the lower specimen are on the same vertical line. This eliminates the eccentric bending moment caused by misalignment of the upper and lower specimen centers. If the centers are not coaxial, the middle connecting plate will tilt when vertical pressure is applied, resulting in uneven distribution of normal pressure on the upper and lower specimens (larger on one side, smaller on the other), thus introducing additional frictional force errors and disrupting the symmetry of the double shear model. Simultaneously, the installation distance between the upper and lower specimens in this direction is measured using the geometric center line of the middle connecting plate as a reference. By translating the upper or lower connecting plate, it is ensured that the offset of the upper specimen relative to the middle plate is equal in magnitude and opposite in direction to the offset of the lower specimen relative to the middle plate (i.e., mirror symmetry). This ensures that the shear deformation of the upper and lower specimens is completely consistent during the horizontal shearing process, and that the horizontal torques acting on the intermediate connecting plate cancel each other out, so that the intermediate connecting plate only performs pure translation and does not rotate.

[0064] Consistent geometric boundary conditions mean that different groups of double-shear test devices maintain identical spatial geometric relationships (such as alignment, symmetry, and parallelism). This is a prerequisite for conducting comparative experiments and establishing a system of simultaneous equations. If the geometric boundary conditions of each group of devices are different (e.g., one group is perfectly aligned, while another has a slight eccentricity), different systematic errors will be introduced, leading to unsolvable equations or distorted results. In one example, the above adjustment process is repeated for the three constructed double-shear configurations (e.g., group A+B, group B+C, and group A+C). Use a feeler gauge to check the parallelism between each connecting plate and use a level to check the overall levelness. Ensure that the three configurations maintain a high degree of consistency in geometric boundary conditions (including alignment accuracy, parallelism, and symmetry). Only when the geometric boundary conditions of the three configurations are consistent will the system of equations constructed in step 103 have the same physical model basis, and the calculated frictional forces of individual specimens will be comparable and accurate.

[0065] In step 503, for each same vertical pressure, based on the original data set, the total horizontal shear force values ​​measured in three sets of double-shear configurations are read. For example, by iterating through all tested points of the same vertical pressure, for each specific vertical pressure, the total horizontal shear force values ​​measured in three sets of double-shear configurations are read from the original data set. Let the three standard simulation specimens be specimen 1 (A), specimen 2 (B), and specimen 3 (C). The three sets of known quantities read are as follows: , and Before reading the data, the background noise of the double shear tester itself (if calibrated) can be subtracted to ensure that the three sets of known quantities purely reflect the sum of the friction forces of the two standard simulated specimens.

[0066] Based on the mechanical superposition principle of the double-shear configuration, that is, under ideal symmetrical double-shear conditions, the total horizontal shear force is equal to the sum of the frictional forces of the upper and lower contact surfaces. Since each specimen contains a friction pair (or is equivalent to a friction unit), the total force of the double-shear configuration is the sum of the individual frictional forces of the two specimens participating in the group. Therefore, a system of three linear equations can be constructed, with the total horizontal shear force of each double-shear configuration as the known quantity of the equation, and the horizontal frictional forces of the two standard simulated specimens participating in the current group test as unknown quantities, such that each equation indicates that the sum of the horizontal frictional forces of the two standard simulated specimens is equal to the corresponding total horizontal shear force. Then, the system of three linear equations is solved to obtain the independent horizontal frictional force components of each standard simulated specimen under the same vertical pressure. Finally, multiple horizontal frictional force components corresponding to a single standard simulated specimen under multiple different vertical pressures are selected as sample data, and the least squares method is used for linear regression analysis to fit and establish the relationship curve between the inherent horizontal frictional force and the vertical pressure characterizing the physical properties of the standard simulated specimen.

[0067] The following uses standard simulated specimens, including A, B, and C, as an example to illustrate the steps of the double shear test.

[0068] 1) Install standard simulated specimens A and B in a double shear combination on the upper and lower connecting plates of the static compression shear testing machine, with the center deviation from the short side length of the specimen being less than 1%. Place anti-slip friction plates on the upper and lower parts of the static compression shear testing machine to prevent slippage.

[0069] 2) Adjust the height of the horizontal shear cylinder of the compression shear testing machine so that the central axis of the cylinder is aligned with the central axis of the rigid plate to avoid lateral forces and bending moments caused by misalignment.

[0070] 3) Apply vertical compressive stress at a rate of 0.05 MPa / s to 10 MPa (i.e., 10000 kN) and keep the vertical pressure constant.

[0071] 4) Apply horizontal shear stress at a rate of 0.002 MPa / s until relative sliding occurs between the intermediate rigid plate and the upper and lower devices, and then stop. Record the force value at the time of sliding.

[0072] 5) Repeat the above steps 3 times, recording the force value during each sliding motion, and average the force value using... express.

[0073] 6) Repeat steps 1) to 5) of the above test for AC and BC to obtain the mean horizontal shear force. and .

[0074] Since this is a double shear test, the average horizontal shear force obtained each time is the sum of the frictional forces of the two standard simulated specimens. Let the horizontal shear forces of the standard simulated specimens A, B, and C in the test be... , and Then we can obtain the following system of equations:

[0075] .

[0076] We can obtain the answer by solving the system of equations. , and That is, the horizontal sliding friction force of the three devices under the same vertical pressure.

[0077] Figure 6 This is a schematic diagram of the relationship curve between inherent horizontal friction and vertical pressure provided in an embodiment of this application. Figure 7 This is a schematic diagram illustrating the relationship between the inherent horizontal friction coefficient and vertical pressure provided in an embodiment of this application. Figure 6 and Figure 7 As shown, by applying different vertical forces and repeating the above experimental steps, the following results can be obtained. Figure 6The inherent horizontal friction of the calibration device under different vertical pressures is shown by... Figure 6 It can be seen that the inherent horizontal friction force (i.e., frictional force, in kN) of this calibration device does not exhibit a perfect linear relationship with the vertical pressure (in kN). The corresponding horizontal friction coefficient can be calculated to obtain... Figure 7 As shown in the figure, the horizontal friction coefficient (i.e., friction coefficient) of the calibration device exhibits a trend of first decreasing and then increasing with the vertical pressure (in kN).

[0078] In step 504, each of the three standard simulated specimens is selected sequentially as the current single-shear test object. For example, a specimen test queue is established, and the first, second, and third specimens are selected sequentially as the current single-shear test objects. The currently selected standard simulated specimen is individually installed on the rolling platform of the testing machine to be calibrated. After installation, the set vertical pressure is applied, and the specimen is checked to ensure vertical alignment and that there is no initial off-center load.

[0079] The rolling platform is driven to perform three reciprocating horizontal shearing motions under a set vertical pressure, and horizontal shearing data is collected synchronously during the reciprocating horizontal shearing motions. While maintaining a constant set vertical pressure, the rolling platform of the testing machine is driven for horizontal displacement control. Sine wave or triangular wave displacement control is typically used, with specific amplitudes (e.g., ±50mm) and frequencies (e.g., 0.1Hz - 1.0Hz, depending on calibration specifications) set. Three complete reciprocating horizontal shearing motions (i.e., three complete load-unload cycles) are strictly executed. During the motion, horizontal force sensor data and displacement sensor data of the testing machine are synchronously collected at a high sampling frequency (e.g., ≥100Hz) to form a time-series raw dataset.

[0080] Then, the frictional force values ​​from the three reciprocating horizontal shearing motions are arithmetically averaged to obtain the single-shear test data of the current standard simulated specimen under a set vertical pressure. Specifically, from the raw data of the three reciprocating horizontal shearing motions, the stable segment is extracted (usually, the unsteady-state data caused by acceleration / deceleration or mechanical clearance at the beginning and end are removed, and the middle stable cycle segment is taken). The average frictional force value (or peak frictional force value, depending on the definition, but here it uniformly refers to the characteristic value representing the frictional properties) during the sliding phase is calculated for each reciprocating motion. By averaging through multiple cycles, random noise, instantaneous jamming, or accidental errors caused by sensor jitter that may occur in a single test are effectively eliminated. After completing the horizontal shear test of the current standard simulated specimen, the current standard simulated specimen is disassembled, and the next set of standard simulated specimens is installed and tested until all three sets of standard simulated specimens have completed the horizontal shear test.

[0081] The single shear test procedure will be explained below using standard simulated specimens A, B, and C.

[0082] 1) Install the standard simulated specimen A in the middle of the rolling platform of the compression-shear testing machine, with the center offset from the short side length of the specimen by less than 1%. Place anti-slip friction plates on the top and bottom of the device to prevent slippage.

[0083] 2) Adjust the height of the horizontal shear cylinder of the compression shear tester to align the central axis of the cylinder with the central axis of the rolling platform to avoid lateral forces and bending moments caused by misalignment.

[0084] 3) Apply vertical compressive stress at a rate of 0.05 MPa / s to 10 MPa (i.e., 10000 kN) and keep the vertical pressure constant.

[0085] 4) Set the horizontal rolling platform displacement to ±50mm and drive the rolling platform to reciprocate at a rate of 0.01Hz / s for 3 cycles, and record the force value during sliding.

[0086] 5) Calculate the average value of the three measured horizontal shear forces, and use... express.

[0087] 6) Repeat steps 1) to 5) for standard simulated specimens B and C to obtain the single shear horizontal shear force of standard simulated specimens B and C. and .

[0088] Let the horizontal friction force of the rolling platform be... Based on the results of the three experiments, we can conclude that:

[0089] .

[0090] In step 505, the set vertical pressure can be substituted into the relationship curve between the inherent horizontal friction force and the vertical pressure to calculate the target standard horizontal friction force of the three standard simulated specimens under the set vertical pressure. Then, the single shear test data corresponding to the three standard simulated specimens under the set vertical pressure are retrieved. The difference between the single shear test data and the target standard horizontal friction force is calculated, and the difference is used as the horizontal friction force of the current standard simulated specimen under the vertical pressure.

[0091] Next, the arithmetic mean of the three horizontal friction forces is taken to obtain the horizontal friction force of the rolling platform of the dynamic compression-shear testing machine under the set vertical pressure level. For example, the formula for a single shear test can be obtained as follows: , and The average of the three results is taken as the horizontal friction force of the rolling platform. ,Right now:

[0092] .

[0093] Finally, based on the given vertical pressure and horizontal friction force, the horizontal friction coefficient under the given vertical pressure is calculated. For example, the friction coefficient can satisfy the formula:

[0094] .

[0095] To reduce measurement errors in the above tests, three samples were used for each measurement step to calculate the average value, and the test result for each sample was the average of the three tests. By varying the vertical pressure and repeating the above test process, the friction force and coefficient of friction of the rolling platform under different vertical pressures can be obtained.

[0096] Traditional calibration often relies on external standard sensors or assumes zero friction under no-load conditions, which is often invalid under heavy loads. This application utilizes differential decoupling, directly using standard specimens with known characteristics as probes to mathematically separate the equipment's own friction force from measured data. Regardless of how nonlinearly the equipment's friction force changes with pressure, it can be accurately captured and quantified, completely solving the industry problem of determining background friction force under heavy loads. A robust error suppression mechanism is constructed through a strategy of independently calculating and averaging three specimens. This method not only obtains the friction coefficient at a single point but can be repeatedly executed for multiple set vertical pressure levels, thereby constructing a complete equipment friction-pressure mapping spectrum. This allows for dynamic correction of test data based on real-time load in subsequent actual engineering tests, deducting systematic errors from the original data in real time, significantly improving the authenticity and accuracy of dynamic compression-shear test data.

[0097] In this embodiment, the calibration effectiveness verification step is also included. A closed-loop test logic of "double shear - single shear - double shear" is used to verify the accuracy of the specimen's inherent friction curve and the equipment's friction coefficient calculated in the preceding steps. Specifically, any pair of standard simulated specimens can be selected, and a first double shear test is performed under any vertical pressure. The baseline value of the double shear resultant force of the first double shear test is recorded. A single shear test is then performed on each of the standard simulated specimen pairs under the same vertical pressure to obtain measured single shear data. Keeping the vertical pressure constant, a second double shear test is performed on the standard simulated specimen pair, and the verified value of the double shear resultant force of the second double shear test is recorded. The baseline value and the verified value of the double shear resultant force refer to the total shear force measured in the double shear configuration at the beginning and end of the verification cycle, respectively. The consistency between the two reflects the time stability and repeatability of the test system.

[0098] Then, the deviation rate between the verified value and the baseline value of the double shear force is calculated. If the deviation rate is less than or equal to the preset tolerance threshold, the calibration under the current vertical pressure is deemed valid, and the relationship curve between the inherent horizontal friction force and the vertical pressure, as well as the horizontal friction coefficient, are stored for subsequent compensation. If the deviation rate is greater than the preset tolerance threshold, the calibration under the current vertical pressure is deemed invalid, and the calibration validity verification steps are repeated. The preset tolerance threshold is the maximum permissible relative error limit set based on engineering experience or standard specifications. It serves as the passing grade for judging the reliability of the calibration results.

[0099] Traditional calibration often stops at calculating parameters, lacking immediate verification of parameter accuracy. This step forms a logical closed loop through double-shear and single-shear back-calculation. Calibration is considered successful only when the calculated equipment friction force perfectly explains the difference between single-shear and double-shear tests, reducing the risk of erroneous parameters being stored. By comparing the first and second double-shear tests, systematic drift that may occur during the test can be keenly detected (such as viscosity changes due to increased oil temperature, thermal expansion of mechanical parts). If the difference between the two double-shear tests is large, it indicates environmental or equipment instability, resulting in an error and avoiding calibration under unreliable conditions. Only data that passes rigorous deviation rate verification is stored and used, ensuring that the friction coefficient used to compensate for actual engineering test data has extremely high traceability and reliability, significantly reducing the uncertainty of the final test results.

[0100] In this embodiment of the application, the calibration method further includes full-range friction characteristic modeling. Specifically, the set vertical pressure can be changed, and the calculation steps of calculating the horizontal friction force and horizontal friction coefficient of the rolling platform of the dynamic compression-shear testing machine under each set vertical pressure can be repeatedly executed to obtain multiple sets of data pairs consisting of horizontal friction force and vertical pressure and horizontal friction force, and the corresponding friction coefficient sequence can also be obtained.

[0101] Then, regression analysis is performed on the data pairs using quadratic polynomial fitting or exponential fitting methods to obtain a fitting equation characterizing the frictional characteristics of the rolling platform. The frictional characteristic fitting equation is a continuous mathematical function; it is not only a summary of the data but also a digital twin of the equipment's physical behavior, allowing users to perform high-precision interpolation predictions at pressure points not yet tested. The fitting equation characterizes the variation of the friction coefficient of the dynamic compression-shear testing machine within the working vertical pressure range. Quadratic polynomial fitting is suitable for situations where frictional force exhibits slight nonlinearity with pressure (such as nonlinear resistance caused by seal compression). The exponential fitting method is suitable for situations with a significant start-up threshold or rapid changes in frictional characteristics at high speeds. Regression analysis is performed on the above data pairs using the least squares method to calculate the best fitting coefficient, minimizing the sum of squared residuals. The fitting equation characterizing the frictional characteristics of the rolling platform is output and embedded in the testing machine's control system or post-processing software. In actual testing, the system reads the real-time vertical pressure, substitutes it into the equation to instantly calculate the current background frictional force, and automatically subtracts it from the original test force.

[0102] In actual engineering tests, vertical pressure is often dynamically changing (e.g., sinusoidal loading) rather than a constant value. Discrete calibration points cannot cover all instantaneous pressure values. By fitting equations, accurate background friction can be calculated based on real-time pressure within milliseconds, achieving dynamic compensation throughout the entire process without blind spots, greatly improving test accuracy under complex loading paths. The friction characteristics of rolling platforms are often not simple constants (Coulomb friction). The compression of the sealing ring and the thickness of the lubricating oil film change with pressure, leading to nonlinearity. Polynomial or exponential fitting can accurately capture these nonlinear characteristics (e.g., static friction dominates in the low-pressure zone, and the sealing resistance surges in the high-pressure zone), which is more consistent with physical reality than a single linear assumption, reducing systematic errors such as overcompensation at low pressure and undercompensation at high pressure. The fitting equations form the "friction fingerprint" of the testing machine. During long-term use of the equipment, only a few key points need to be periodically sampled for rapid verification to update the fitting parameters, eliminating the need for tedious full-range testing every time. This not only improves calibration efficiency but also facilitates tracking the long-term evolution trend of equipment performance. Encapsulating complex friction laws into simple mathematical equations enables the testing machine control system to have self-sensing and self-correcting capabilities. This is a key step in realizing the intelligence and automation of high-end material testing equipment, reducing the tedious process of manual table lookup and correction, as well as human error.

[0103] Those skilled in the art will understand that all or part of the functions of the various methods in the above embodiments can be implemented by hardware or by computer programs. When all or part of the functions in the above embodiments are implemented by computer programs, the program can be stored in a computer-readable storage medium, which may include: read-only memory, random access memory, disk, optical disk, hard disk, etc., and the program is executed by a computer to achieve the above functions. For example, the program can be stored in the memory of a device, and when the program in the memory is executed by the processor, all or part of the above functions can be achieved. In addition, when all or part of the functions in the above embodiments are implemented by computer programs, the program can also be stored in a server, another computer, disk, optical disk, flash drive, or external hard drive, etc., and can be downloaded or copied to the memory of a local device, or the system of the local device can be updated. When the program in the memory is executed by the processor, all or part of the functions in the above embodiments can be achieved.

[0104] The above examples illustrate this application only to aid understanding and are not intended to limit its scope. Those skilled in the art to which this application pertains can make various simple deductions, modifications, or substitutions based on the ideas presented.

Claims

1. A method for calibrating the horizontal friction force of a dynamic compression-shear testing machine, characterized in that, include: Prepare at least three standard simulated specimens with identical mechanical properties, the standard simulated specimens being independent of the seismic isolation bearing; The three standard simulated specimens were paired up and assembled with rigid frame components to form three sets of double shear configurations. Each set of double shear configurations was then placed on a double shear compression shear testing machine and horizontal shear tests were conducted under various vertical pressures to obtain three sets of double shear resultant force data. For each same vertical pressure, based on the original data set, the total horizontal shear force measured in the three sets of the double shear configurations was read respectively; A system of three linear equations is constructed, with the total horizontal shear force of each double shear configuration as the known quantity of the equation, and the horizontal friction force of the two standard simulated specimens participating in the current group test as the unknown quantity, so that each equation indicates that the sum of the horizontal friction forces of the two standard simulated specimens is equal to the corresponding total horizontal shear force. Solving the three-variable linear equations yields the independent horizontal friction force components for each of the standard simulated specimens under the same vertical pressure. Multiple horizontal friction force components corresponding to a single standard simulated specimen under multiple different vertical pressures were selected as sample data. The least squares method was used to perform linear regression analysis to fit and establish the relationship curve between the inherent horizontal friction force and the vertical pressure that characterizes the physical properties of the standard simulated specimen. Each of the standard simulated specimens was individually mounted on the rolling platform of the dynamic compression-shear testing machine to be calibrated to form a single shear configuration. Horizontal shear tests were performed sequentially under a set vertical pressure to obtain the single shear test data corresponding to each of the standard simulated specimens. Based on the relationship curve between the inherent horizontal friction force and the vertical pressure, the target inherent horizontal friction force corresponding to each of the standard simulated specimens under the set vertical pressure is calculated. Based on the single shear test data of each of the standard simulated specimens and the target inherent horizontal friction force, the horizontal friction force and horizontal friction coefficient of the rolling platform of the dynamic compression-shear testing machine under the set vertical pressure are calculated.

2. The calibration method for the horizontal friction force of the dynamic compression-shear testing machine according to claim 1, characterized in that, The standard simulated specimen consists of a lower base and an upper pressure plate. The lower base is larger than the upper pressure plate in the length direction. The lower base has pre-drilled hoisting holes at its four corners. The upper surface of the lower base is inlaid with a mirror-finished stainless steel plate. The lower surface of the upper pressure plate is inlaid with a high-strength PTFE sliding plate. The surface of the PTFE sliding plate has a circular recess as a silicone grease storage groove. Silicone grease is applied to the surface of the PTFE sliding plate during assembly. The sides of the lower base and the upper pressure plate are provided with mutually cooperating side guide mechanisms. The guide mechanisms are linear guide rails.

3. The calibration method for the horizontal friction force of the dynamic compression-shear testing machine according to claim 1, characterized in that, Before the step of pairing the three standard simulated specimens in pairs and assembling them with rigid frame components to form three sets of double-shear configurations, the method further includes: Multiple candidate specimens were subjected to sliding tests under low friction conditions, and sliding friction force data of each candidate specimen under a set vertical pressure were collected. Three candidate specimens with sliding friction deviation less than or equal to the set deviation, no jamming during sliding, and smooth operation of the guide mechanism were selected as the standard simulation specimens with consistent mechanical properties. The three standard simulation specimens are sequentially labeled as specimen 1, specimen 2, and specimen 3.

4. The calibration method for the horizontal friction force of the dynamic compression-shear testing machine according to claim 1, characterized in that, The rigid frame includes an upper connecting plate, a lower connecting plate, and a middle connecting plate; The process involves pairing the three standard simulated specimens together and assembling them with rigid frame components to form three sets of double-shear configurations, including: For each set of double-shear configurations, two standard simulated specimens are respectively clamped between the upper connecting plate and the middle connecting plate, and between the middle connecting plate and the lower connecting plate; Adjust the installation position of each set of double shear configurations so that the shear center lines of the two standard simulated specimens in each set of double shear configurations are coaxial in the vertical direction and symmetrically arranged about the intermediate connecting plate in the horizontal shear direction, so as to ensure that the geometric boundary conditions of the three sets of double shear configurations are consistent.

5. The calibration method for horizontal friction force of the dynamic compression-shear testing machine according to claim 1, characterized in that, Each of the standard simulated specimens is individually mounted on the rolling platform of the dynamic compression-shear testing machine to be calibrated to form a single shear configuration. Horizontal shear tests are then performed sequentially under a set vertical pressure to obtain the single shear test data for each standard simulated specimen, including: Each of the three standard simulated specimens is selected sequentially as the current single-shear test object; The rolling platform is driven to perform three reciprocating horizontal shearing motions under the set vertical pressure, and horizontal shearing data is collected synchronously during the reciprocating horizontal shearing motion. The frictional force values ​​of the three reciprocating horizontal shearing motions are arithmetically averaged and used as the single shear test data of the current standard simulated specimen under the set vertical pressure. After completing the horizontal shear test of the current standard simulated specimen, disassemble the current standard simulated specimen and install and test the next set of standard simulated specimens until all three sets of standard simulated specimens have completed the horizontal shear test.

6. The calibration method for the horizontal friction force of the dynamic compression-shear testing machine according to claim 1, characterized in that, Based on the relationship curve between the inherent horizontal friction force and the vertical pressure, the target inherent horizontal friction force corresponding to each of the standard simulated specimens under the set vertical pressure is calculated. Based on the single shear test data of each of the standard simulated specimens and the target inherent horizontal friction force, the horizontal friction force and horizontal friction coefficient of the rolling platform of the dynamic compression-shear testing machine under the set vertical pressure are calculated, including: Substituting the set vertical pressure into the relationship curve between the inherent horizontal friction force and the vertical pressure, the target standard horizontal friction force of the three standard simulated specimens under the set vertical pressure is calculated respectively. Retrieve the single shear test data corresponding to the three standard simulated specimens under the set vertical pressure; Calculate the difference between the measured single shear data and the target standard horizontal friction force, and use the difference as the horizontal friction force of the current standard simulated specimen under the vertical pressure; The arithmetic average of the three horizontal friction forces is used to obtain the horizontal friction force of the rolling platform of the dynamic compression-shear testing machine under the set vertical pressure level. Based on the set vertical pressure and the set horizontal friction force, the horizontal friction coefficient under the set vertical pressure is calculated.

7. The calibration method for the horizontal friction force of the dynamic compression-shear testing machine according to claim 1, characterized in that, It also includes a step for verifying the calibration effectiveness, which includes: Select any pair of standard simulated specimens and perform the first double shear test under any vertical pressure. Record the reference value of the resultant double shear force of the first double shear test. Each of the standard simulated specimens in the standard simulated specimen pair was subjected to a single shear test under the same vertical pressure to obtain single shear test data. Keeping the vertical pressure constant, perform a second double shear test on the paired standard simulation specimens and record the verification value of the resultant double shear force of the second double shear test; Calculate the deviation rate between the verified value of the dual shear force and the reference value of the dual shear force; If the deviation rate is less than or equal to the preset tolerance threshold, the calibration under the current vertical pressure is determined to be effective, and the relationship curve between the inherent horizontal friction force and the vertical pressure and the horizontal friction coefficient corresponding to the vertical pressure are stored for subsequent compensation. If the deviation rate is greater than the preset tolerance threshold, the calibration under the current vertical pressure is determined to be invalid, and the calibration validity verification step is re-executed.

8. The calibration method for the horizontal friction force of the dynamic compression-shear testing machine according to claim 1, characterized in that, The calibration method further includes: By changing the set vertical pressure, the calculation steps of the horizontal friction force and the horizontal friction coefficient of the rolling platform of the dynamic compression-shear testing machine under each set vertical pressure are repeatedly executed to obtain multiple sets of data pairs consisting of the horizontal friction force and the vertical pressure and the horizontal friction force. The data pairs are subjected to regression analysis using a quadratic polynomial fitting or exponential fitting method to obtain a fitting equation characterizing the frictional properties of the rolling platform. The fitting equation characterizes the variation law of the friction coefficient of the dynamic compression-shear testing machine within the working vertical pressure range.

9. A calibration system for the horizontal friction force of a dynamic compression-shear testing machine, characterized in that, include: Rigid frame components; Three standard simulated specimens with identical mechanical properties are configured to be paired in pairs and assembled with the rigid frame assembly to form three independent double shear configurations, or to be individually mounted on the rolling platform of the dynamic compression-shear testing machine to form a single shear configuration. The memory is configured to store instructions; and The processor is configured to retrieve the instructions from the memory and, when executing the instructions, to implement the calibration method for the horizontal friction force of the dynamic compression-shear testing machine according to any one of claims 1 to 8.

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