Split Hopkinson bar confining pressure collaborative control method and device

Abstract

The application discloses a Hopkinson bar confining pressure cooperative control method and device with pressure division, relates to the field of automatic control technology, and aims at solving the problems of low efficiency and poor safety of the existing Hopkinson bar confining pressure control method. The method generates a coupling target group of cavity pressure, buffer pressure and intermediate pressure according to a target confining pressure, an allowable confining pressure fluctuation amount, a rod body invasion feature and a sealing pressure bearing characteristic; three pressure fields are cooperatively established after the cavity is locked, and the pressure difference between adjacent pressure fields is restricted; when loading, the volume change caused by the rod body invasion is absorbed by a pressure buffer assembly in direct hydraulic communication with the confining pressure cavity; a control unit distinguishes between an impact transient and a pressure trend, suppresses valve control regulation during the impact transient, and executes pressure compensation, liquid return and intermediate pressure following after the transient decays; after the test, pressure relief is associated along a controlled pressure difference path, and the cavity is allowed to be opened after each pressure field is safe. The application realizes the time scale division of fast passive compensation and low-frequency active regulation, and enables the graded sealing to maintain controlled pressure bearing during the pressure building, loading and pressure relief processes.

Description

Technical Field

[0001] This invention relates to the field of automatic control technology, and in particular to a multi-pressure domain collaborative control method and device for Hopkinson bar confining pressure tests. Background Technology

[0002] The Hopkinson bar test is used to study the dynamic mechanical properties of materials under high strain rate conditions. To simulate the stress environment of deep rock masses, high-pressure protective structures, and other constrained materials, a confining pressure cavity can be set outside the specimen, and hydraulic confining pressure can be established in the confining pressure cavity before impact loading. Whether the confining pressure is accurate before loading, stable during loading, and can be safely released after the test all affect the repeatability of the test results and the safety of equipment operation.

[0003] Existing confining pressure testing apparatuses typically use a rubber sleeve to cover a portion of the specimen and the rod, applying confining pressure by compressing the rubber sleeve. After axial impact, the specimen undergoes lateral deformation, which further compresses the rubber sleeve and hydraulic medium, causing the actual confining pressure on the specimen to deviate from the set value. Frictional constraints also occur between the rubber sleeve and the specimen and rod, creating additional effects not attributable to the constitutive response of the specimen material. With increasing test pressure and number of repetitions, the rubber sleeve may also age, break, or fail to seal.

[0004] Another approach uses a rigid confining cavity and injects hydraulic fluid into it. While this reduces the direct constraint of the rubber sleeve on the specimen, the hydraulic fluid has limited volumetric elasticity, and the rod occupies existing liquid space upon entering the confining cavity. If this volume increase is not released promptly, the cavity pressure will create a peak pressure. Although placing a conventional accumulator on the external pipeline of the confining cavity can absorb slow pressure fluctuations, the hydraulic fluid must first pass through connecting pipelines and local throttling points to reach the accumulator. Pipeline inertia, friction resistance, and local resistance weaken its response to rapid volume changes. Therefore, the compensation effect of an external accumulator for impact transients is easily affected by pipeline conditions.

[0005] At the point where the rod penetrates the confining cavity, a single seal must bear the entire pressure difference between the cavity pressure and the external ambient pressure. Increasing the seal preload can improve the static seal, but it will also increase the resistance to rod movement and may introduce additional friction into the test results. Using two seals without controlling the pressure between them, simply increasing the number of seals, does not guarantee that the total pressure difference will be distributed as expected; especially during pressure build-up and depressurization, when the intermediate pressure is not synchronized with the cavity pressure, a single seal may momentarily bear the majority of the pressure difference.

[0006] Existing control methods typically treat confining pressure establishment, buffer chamber inflation, sealing pressure division, impact pressure stabilization, and post-test pressure relief as independent actions, controlling each separately based on a single pressure target or a single valve state. This control method has at least the following shortcomings: First, multiple pressure branches establish pressure independently in a fixed sequence, failing to constrain the pressure difference between adjacent pressure domains at the moment of pressure establishment; second, the control valve directly follows the peak impact pressure, and when the valve response lags behind the impact process, it not only fails to reduce the peak pressure in time but may also cause reverse overshoot after the impact ends; third, if only the chamber pressure is used as the unlocking criterion after the test, it cannot rule out the possibility of residual pressure in the intermediate pressure chamber or buffer chamber; fourth, when the buffer assembly leaks, jams, or has insufficient compensation stroke, there is a lack of a control mechanism to identify faults based on pressure response.

[0007] Therefore, the confining pressure cavity, pressure buffer assembly, and graded sealing assembly need to be regarded as a mutually coupled pressure system, and the cavity pressure domain, buffer pressure domain, and intermediate pressure domain need to be handled simultaneously at the control level. It is also necessary to distinguish between the rapid passive compensation undertaken by the mechanical hydraulic structure and the slower active adjustment undertaken by the control valve, so that pressure changes at different time scales are handled by different execution mechanisms, thereby taking into account impact pressure stabilization, sealing load reduction, and safe opening and closing without relying on the rubber sleeve confining pressure. Summary of the Invention

[0008] The purpose of this invention is to provide a method and device for coordinated control of confining pressure with a Hopkinson bar and pressure division, so as to solve the problems of lag in compensation for rapid volume change, independent multiple pressure branches, unstable distribution of graded sealing differential pressure, and high risk of accidental opening of the cavity under pressure in existing confining pressure control.

[0009] In a first aspect, this embodiment provides a method for coordinated control of confining pressure with a Hopkinson bar and voltage divider, comprising the following steps:

[0010] Based on the target confining pressure, allowable confining pressure fluctuation, rod intrusion characteristic parameters, and pressure bearing characteristic parameters of the graded sealing assembly, a coupled pressure target group of cavity pressure, buffer pressure, and intermediate pressure is formed;

[0011] When the confining pressure cavity is in a closed and locked state, a cavity pressure domain, a buffer pressure domain, and an intermediate pressure domain corresponding to the coupled pressure target group are established respectively, so that the pressure difference between adjacent pressure domains is kept within the corresponding allowable pressure difference range; when all three pressure domains reach the target and the pressure change trend reaches a steady state, a loading allow signal is output.

[0012] In response to the Hopkinson rod loading, a pressure buffer assembly directly hydraulically connected to the confining pressure cavity is used to convert the increase in hydraulic medium volume caused by the rod intrusion into the compressibility of the compressible medium, thereby passively compensating for the impact transient of the cavity pressure.

[0013] The cavity pressure response during loading is divided into an impact transient component and a pressure trend component. Active adjustment of the confining pressure cavity is suppressed during the duration of the impact transient component. After the impact transient component decays, the cavity pressure is adjusted according to the pressure trend component, and the intermediate pressure target is updated with the cavity pressure to keep the pressure difference on both sides of the staged sealing assembly within the corresponding allowable pressure difference range.

[0014] After the test is completed, the three pressure domains are depressurized in a manner that keeps the pressure difference between adjacent pressure domains within the corresponding allowable pressure difference range, and the closed locking state is released after all three pressure domains meet the safe opening conditions.

[0015] Preferably, the determination of the buffer pressure in the coupled pressure target group includes:

[0016] The predicted volume change corresponding to the rod's intrusion into the confining pressure cavity is determined based on the rod's cross-sectional area and the predicted intrusion stroke.

[0017] Establish the pressure-volume relationship of a compressible medium from the initial buffer state to the compensated state. Under the constraint that the predicted volume change is jointly absorbed by the pressure buffer components on both sides of the confining cavity, calculate the predicted peak pressure corresponding to different buffer pressures and different effective buffer volumes.

[0018] The target buffer pressure and effective buffer volume are determined from a combination of conditions that ensure the predicted peak pressure is no higher than the sum of the target confining pressure and the allowable confining pressure fluctuation, and that the predicted displacement of the movable separator in the pressure buffer assembly does not exceed the available compensation stroke.

[0019] Preferably, the determination of the intermediate pressure in the coupled pressure target group includes:

[0020] Determine the allowable pressure difference between the inner seal near the confining cavity and the outer seal near the external environment in the graded sealing assembly, respectively;

[0021] Under the constraint that the first pressure difference between the cavity pressure domain and the intermediate pressure domain does not exceed the allowable pressure difference of the inner seal and the second pressure difference between the intermediate pressure domain and the external environment does not exceed the allowable pressure difference of the outer seal, the total pressure difference is distributed according to the pressure margin of the inner seal and the outer seal to obtain the intermediate pressure target.

[0022] When the cavity pressure changes, the intermediate pressure target is updated accordingly to keep the pressure margin ratio of the first pressure difference to the second pressure difference within a preset range.

[0023] Preferably, the step of establishing a cavity pressure domain, a buffer pressure domain, and an intermediate pressure domain corresponding to the coupled pressure target group, respectively, so that the pressure difference between adjacent pressure domains is maintained within the corresponding allowable pressure difference range, includes:

[0024] First, establish a buffer pressure domain so that the movable separator in the pressure buffer assembly forms a gas-liquid separation interface within the available compensation stroke.

[0025] According to the segmented pressure rise curve, the cavity pressure domain and intermediate pressure domain are established synchronously. During the cavity pressure rise process, the synchronous pressure command of the intermediate pressure domain is generated based on the current value of the cavity pressure.

[0026] When the first pressure difference between the cavity pressure domain and the intermediate pressure domain reaches the upper boundary of the corresponding allowable pressure difference range, the pressure increase of the confining cavity is paused and the intermediate pressure is increased; when the second pressure difference between the intermediate pressure domain and the external environment reaches the upper boundary of the corresponding allowable pressure difference range, the rate of increase of the intermediate pressure is reduced or the establishment of the intermediate pressure is paused until both the first pressure difference and the second pressure difference return to their respective allowable pressure difference ranges.

[0027] Preferably, the pressure change trend reaches a steady state, including:

[0028] Within the sliding time window, calculate the fluctuation amplitude, change slope, and pressure holding attenuation of the cavity pressure, buffer pressure, and intermediate pressure respectively.

[0029] When the pressure deviation of each pressure domain is within the allowable range of the corresponding target value, the fluctuation amplitude and the change slope do not exceed the corresponding steady-state threshold, the pressure holding attenuation does not exceed the corresponding leakage judgment threshold, and the locking position feedback of the cavity opening and closing component remains within the locking range, it is determined that the loading ready state has been reached.

[0030] If any condition is not met, the load enable signal shall be prohibited from being output, and a fault indicator shall be output according to the pressure range or lock position corresponding to the unmet condition.

[0031] Preferably, the cavity pressure response during loading is divided into an impact transient component and a pressure trend component, including:

[0032] An impact protection time window is established based on the Hopkinson rod loading trigger signal, and the rate of change of the cavity pressure sampling sequence within the impact protection time window is determined.

[0033] Pressure responses with a rate of change exceeding the transient determination threshold are identified as the impact transient component, and pressure responses with a low rate of change retained after time window smoothing are identified as the pressure trend component.

[0034] During the impact protection time window, the trigger channels for pressure replenishment regulation and fluid return regulation are closed, and passive volume compensation is performed by the pressure buffer component. After the impact protection time window ends and the rate of change of cavity pressure falls back to the trend regulation threshold, pressure replenishment regulation or fluid return regulation is resumed according to the pressure trend component.

[0035] Preferably, it also includes buffer status diagnosis:

[0036] A predicted response envelope for the cavity pressure is generated based on the pressure-volume relationship of the compressible medium in the pressure buffer assembly and the rod intrusion characteristic parameters.

[0037] The peak pressure of the cavity, the time of peak occurrence, and the transient decay characteristics collected during loading are compared with the predicted response envelope;

[0038] When the cavity pressure response exceeds the predicted response envelope, based on the combination of buffer pressure decay, cavity pressure holding decay, and intermediate pressure change, the system identifies compressible medium leakage, obstruction of movable separator movement, or leakage of graded sealing assembly, and executes at least one of the following: prohibiting reloading, depressurizing associated pressure domains, and fault alarm.

[0039] Preferably, the associated pressure relief of the three pressure domains includes:

[0040] Stop supplying hydraulic medium to the confining pressure cavity, open the return fluid branch of the confining pressure cavity, and synchronously reduce the intermediate pressure target according to the cavity pressure drop process, so that the pressure difference between the cavity pressure domain and the intermediate pressure domain, as well as the pressure difference between the intermediate pressure domain and the external environment, are kept within the corresponding allowable pressure difference range.

[0041] After the pressure in the cavity drops to the return fluid auxiliary pressure range, low-pressure gas is introduced into the confining pressure cavity to push the hydraulic medium out through the return fluid branch.

[0042] After the pressure in the cavity and the intermediate pressure domains drops to their respective safe pressures, the remaining pressure in the buffer pressure domain is released.

[0043] When the cavity pressure, intermediate pressure, and buffer pressure are all below their respective safety thresholds, and the rate of change of each pressure remains stable, an unlocking signal is generated.

[0044] Preferably, it also includes state interlocking throughout the entire process:

[0045] Before closing the cavity, confirm that the pressure regulating branch is in an unloaded state and that the cavity opening and closing components are in the allowable closing position.

[0046] When any pressure domain is in an unsafe pressure state, the cavity opening and closing component is prohibited from performing the unlocking action, and the cavity pressure domain is prohibited from being established when the cavity opening and closing component has not reached the locking position.

[0047] When the chamber pressure exceeds the overpressure threshold, the pressure difference between any adjacent pressure domains exceeds the emergency pressure difference threshold, the buffer pressure is lower than the buffer failure threshold, or the lock-up position feedback is abnormal, pressurization is stopped, the corresponding pressure regulation branch is controlled in the direction that prevents the pressure difference between adjacent pressure domains from continuing to expand, and an alarm is output.

[0048] Record the target value, actual value, action status, closure and lock-up status, and loading trigger time of each pressure domain.

[0049] According to a second aspect of this disclosure, a Hopkinson bar confining pressure coordination control device with pressure divider is provided, comprising:

[0050] The pressure-bearing cavity assembly includes a fixed cavity portion and a movable cavity portion that are axially joined together, wherein the fixed cavity portion and the movable cavity portion together form a confining pressure cavity through which the Hopkinson rod body passes when closed;

[0051] Pressure buffer assemblies are integrated on both axial sides of the confining pressure cavity. Each pressure buffer assembly includes a buffer cavity and a movable partition disposed within the buffer cavity. The movable partition divides the buffer cavity into a gas-side space for containing a compressible medium and a liquid-side space for containing a hydraulic medium. The liquid-side space is directly hydraulically connected to the confining pressure cavity so that the movable partition moves in response to changes in the volume of the confining pressure cavity.

[0052] A graded sealing assembly is provided at the position where the rod penetrates the pressure-bearing cavity assembly, including at least two seals spaced apart along the direction from the confining pressure cavity to the external environment and an intermediate pressure cavity located between adjacent seals, wherein the intermediate pressure cavity is connected to an intermediate pressure regulating branch.

[0053] The cavity opening and closing assembly includes a circumferential locking member for limiting the axial separation of the fixed cavity portion and the movable cavity portion, a locking drive member for driving the circumferential locking member to move between a locked position and an unlocked position, and a translation drive member for driving the movable cavity portion to move axially.

[0054] The pressure regulating assembly includes an injection branch and a return branch connected to the confining pressure cavity, a buffer pressure regulating branch connected to the gas-side space, and the intermediate pressure regulating branch.

[0055] Pressure detection components are used to collect chamber pressure, buffer pressure, and intermediate pressure;

[0056] The control unit is communicatively connected to the pressure detection component, the pressure regulation component, and the cavity opening and closing component, respectively, for establishing and coordinating the cavity pressure domain, the buffer pressure domain, and the intermediate pressure domain, controlling the passive compensation during the impact transient and the pressure trend adjustment after the impact transient decay, and performing state interlocking for pressure building, loading permission, associated pressure relief, and cavity opening and closing.

[0057] The beneficial effects of the technical solutions provided in the embodiments of the present invention include at least the following:

[0058] (1) Before the test, the present invention determines the buffer pressure and buffer volume based on the predicted volume change caused by the rod intrusion, so that the pressure buffer component has a compensation capability that matches the test conditions. This method does not passively open the remote pipeline only after the pressure peak appears, but pre-establishes the compressible medium and gas-liquid separation interface to allow for the volume absorption during loading.

[0059] (2) The pressure buffer assembly is integrated on both sides of the confining pressure cavity, and its liquid side space is directly hydraulically connected to the confining pressure cavity. The increase in liquid volume caused by the intrusion of the rod can directly push the movable partition to compress the gas side space, shorten the pressure transmission path, and form a rapid compensation channel undertaken by the mechanical hydraulic structure.

[0060] (3) This invention separates the processing of shock transients and pressure trends. The shock transients are passively absorbed by the pressure buffer assembly, and the control valve does not follow the peak action within the shock protection time window; the low-frequency deviation after the shock attenuates is then corrected by the pressure replenishment or return fluid branch. This reduces the reverse overshoot caused by the lag action of the control valve, allowing the rapid physical compensation and the slower closed-loop regulation to each handle their appropriate time scales.

[0061] (4) This invention establishes a coupled pressure target group of cavity pressure domain, buffer pressure domain and intermediate pressure domain, and continuously constrains the pressure difference between adjacent pressure domains during pressure building, pressure stabilization and pressure relief. The load distribution of the two-stage seal no longer depends solely on the static structure, but is maintained within the predetermined pressure margin ratio through the following control of the intermediate pressure, which is beneficial to reduce the concentrated load of the single seal and the resistance of the rod movement.

[0062] (5) The present invention uses the pressure values ​​of multiple pressure domains, the pressure change trend, and the cavity locking position to jointly determine whether loading and opening of the cavity are allowed. When there is residual pressure or abnormal locking feedback in any pressure domain, the control unit is prohibited from performing unsafe actions, thereby forming a state interlock covering the entire process of pressure building, loading, and depressurization.

[0063] (6) This invention can identify leakage of buffer medium, obstruction of movement of movable separators, or leakage of graded seals based on the deviation between predicted pressure response and measured pressure response. This diagnosis is established using existing pressure data, without relying solely on manual disassembly and inspection, and facilitates the detection of performance degradation between repeated tests. Attached Figure Description

[0064] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0065] Figure 1This is a schematic diagram of the process for a collaborative control method of confining pressure with a Hopkinson bar with voltage divider according to the present invention;

[0066] Figure 2 This is a schematic cross-sectional view of a device according to an embodiment of the present invention;

[0067] Figure 3 This is a schematic diagram of the isometric structure of a device according to an embodiment of the present invention;

[0068] Figure 4 This is a schematic cross-sectional view of the fixed cavity portion according to an embodiment of the present invention;

[0069] Figure 5 This is an isometric structural diagram of the movable cavity portion according to an embodiment of the present invention.

[0070] The annotations in the attached figures are explained as follows:

[0071] 101. Fixed end of cavity; 102. Movable end of cavity; 103. Cavity sealing ring; 104. Hydraulic pressure dividing oil circuit sealing ring; 101a. First gas buffer cavity; 101b. First buffer cavity passage; 101c. First hydraulic pressure dividing oil circuit; 101d. Flange; 102a. Second gas buffer cavity; 102b. Second buffer cavity passage; 102c. Second hydraulic pressure dividing oil circuit; 102d. High-pressure cavity oil circuit; 102e. Pressure sensor passage; 102f. Cavity return gas pressure passage; 102g. Notched flange; 201. Buffer piston; 202. Self-locking nut; 203. Piston seal 301. U-shaped chuck; 302. Rotary gear; 303. Power gear; 304. Support bearing; 305. Reducer and servo motor; 401. Pressure sensor; 402a. Main control solenoid valve; 402b. Return fluid solenoid valve; 402c. Buffer chamber passage solenoid valve; 402d. Hydraulic pressure distribution circuit solenoid valve; 501. Cavity fixed end support; 502. U-shaped chuck support roller; 503. Cavity movable end support; 504. Support cover plate; 505. Linear slider module; 601. Separate Hopkinson bar; 602. Test specimen; 603. Heat shrink sleeve. Detailed Implementation

[0072] The technical solution of the present invention will now be described with reference to the accompanying drawings.

[0073] In embodiments of the present invention, words such as "exemplarily," "for example," etc., are used to indicate that something is an example, illustration, or description. Any embodiment or design described as "exemplary" in the present invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the word "exemplary" is intended to present the concept in a concrete manner. Furthermore, in embodiments of the present invention, the meaning expressed by "and / or" can be both, or either one.

[0074] In the embodiments of this invention, the terms "image" and "picture" may sometimes be used interchangeably. It should be noted that, without emphasizing the distinction between them, they convey the same meaning. Similarly, the terms "of," "corresponding (relevant)," and "corresponding" may sometimes be used interchangeably. It should be noted that, without emphasizing the distinction between them, they convey the same meaning.

[0075] In this embodiment of the invention, sometimes a subscript such as W1 may be written in a non-subscript form such as W1. When the difference is not emphasized, the meaning they express is the same.

[0076] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0077] This invention provides a hydraulic control method for an intelligent Hopkinson bar with pressure divider, comprising the following steps:

[0078] S101. Based on the target confining pressure, allowable confining pressure fluctuation, rod intrusion characteristic parameters, and pressure bearing characteristic parameters of the graded sealing assembly, a coupled pressure target group of cavity pressure, buffer pressure, and intermediate pressure is formed.

[0079] The function of the cavity pressure domain is to provide the target confining pressure to the specimen; the function of the buffer pressure domain is to provide compressible space for rapid volume changes; and the function of the intermediate pressure domain is to distribute the total pressure difference between the confining cavity and the external environment to multiple seals. These three pressure domains are not three parallel conventional pressure branches, but rather form a mutually constraining control relationship through target generation, pressure difference corridors, and time scale division of labor.

[0080] The terms "preset value," "threshold," "allowable range," and "time window" used in this manual refer to control parameters determined and written into the control unit before the start of this test, not arbitrary values ​​that cannot be determined. The parameters are categorized into four types based on their source: The first type is equipment parameters, including buffer chamber geometry, effective area and available stroke of movable separators, rated allowable differential pressure of seals, pressure sensor range and accuracy, valve response time, and position feedback accuracy of circumferential locking components; the second type is test input parameters, including target confining pressure, rod diameter, predicted intrusion stroke, rod length, and rod material wave velocity; the third type is calibration parameters, including pressure change caused by a unit pulse from the electronically controlled valve, steady-state pressure change rate distribution, impact pressure change rate distribution, and pressure holding attenuation baseline; the fourth type is safety parameters, which are obtained by multiplying the equipment's pressure resistance limit, the rated allowable differential pressure of seals, and sensor measurement error by a safety factor. The control unit reads the aforementioned parameters before the test begins and associates and stores the parameter version, determination basis, and applicable test number.

[0081] Before conducting the confining pressure test, the operator inputs the target confining pressure P. c*、 Allowable confining pressure fluctuation Δ Pallow The parameters to be considered include the rod diameter (d), predicted intrusion stroke (L), and specimen information. The rod diameter and predicted intrusion stroke together constitute the rod intrusion characteristic parameters. The predicted intrusion stroke can be given by the loading scheme of this test, or a conservative value can be selected from similar test records.

[0082] The control unit determines the effective cross-sectional area A of the rod based on its diameter and obtains the predicted volume change using ΔV=A×L. If the effective areas and initial volumes of the two pressure buffer components are similar, each side can bear half of the predicted volume change; if the structures on both sides are different, the allocation ratios η1 and η2 are determined based on the available compensation stroke and effective area on each side, and η1+η2=1.

[0083] For implementations using nitrogen or air as the compressible medium, the control unit predicts the buffered pressure using the pressure-volume relationship. The compressibility index n can be selected between isothermal and adiabatic indices based on the impact process and external heat exchange conditions, and is determined during the equipment calibration phase. The control unit iterates through the allowable buffer pressure and initial effective volume combinations, calculating the compensated gas pressure, movable partition displacement, and remaining compensation stroke, respectively.

[0084] Combinations that meet the following condition are included in the candidate set: the compensated predicted pressure does not exceed P. c* +ΔP allow The movable partition's displacement does not exceed the available stroke; a preset stroke margin is retained after compensation; the initial buffer pressure will not push the movable partition into the limit position before the cavity pressure is established. The control unit can select from the candidate set a combination of smaller initial inflation volume, larger remaining stroke, or smaller predicted pressure fluctuation value as the buffer pressure target P. g* and buffer volume target V g* .

[0085] The intermediate pressure target is determined based on the allowable pressure difference between the two seals. The control unit reads the allowable pressure difference ΔP between the inner and outer seals. in,max The allowable pressure difference ΔP between the outer seal and the outer seal out,max And determine the pressure distribution coefficient α. The value of α is such that (P c* -P m* ) / ΔP in,max With (P) m* -P e ) / ΔP out,max This brings the pressure margins of the two seals closer together, thus making their pressure margin ratios similar.

[0086] When the allowable pressure difference between the two seals is the same and the external ambient pressure can be approximated as zero gauge pressure, the intermediate pressure target can be set as the intermediate value of the target confining pressure. When the pressure bearing capacity of the outer seal is low, the intermediate pressure can be reduced to decrease the second pressure difference borne by the outer seal. When the pressure bearing capacity of the inner seal is low, the intermediate pressure can be increased to decrease the first pressure difference.

[0087] The control unit will P c* P g* and P m* The corresponding allowable deviation, allowable rate of change, and safety threshold are combined to form a coupled pressure target group. This coupled pressure target group is stored in association with the test number and serves as a unified control benchmark in subsequent pressure build-up, loading, and depressurization phases.

[0088] During the target generation phase, the target confining pressure determines the overall level of the intermediate pressure; the allowable confining pressure fluctuation and the predicted volume change jointly determine the buffer pressure and buffer volume; and the remaining compensation capacity of the buffer components determines whether loading is allowed under the corresponding target confining pressure. Therefore, no pressure target is set independently of other pressure domains.

[0089] To ensure that the same control method is adaptable to confining cavities of different sizes, rods of different diameters, and seals with different performance characteristics, parameter calibration can be performed before the equipment is put into use. Parameter calibration includes calibration of pressure regulating branches, calibration of pressure buffer components, calibration of graded sealing components, and calibration of pressure trend extraction parameters.

[0090] The pressure buffer assembly calibration is used to determine the relationship between buffer pressure, movable partition displacement, and equivalent volumetric compliance. When the confining pressure cavity is in a low-pressure safe state, the control unit injects a known volume of hydraulic medium into the cavity and records the changes in buffer pressure and cavity pressure. The known injected volume is equivalent to a controllable volumetric disturbance; based on this, the control unit calculates the cavity pressure change caused by the unit volumetric disturbance, thus obtaining the equivalent volumetric compliance of the pressure buffer assembly.

[0091] If the device is equipped with a movable partition position detection element, the control unit also records the displacement change corresponding to the known injection volume to verify the available compensation stroke. If the device is not equipped with a position detection element, the position of the movable partition can be indirectly estimated based on the buffer chamber geometry, injection volume, and buffer pressure changes. This indirect estimate is not used to replace the mechanical limit, but is used to determine whether the remaining compensation capacity meets the requirements of the next test.

[0092] The graded sealing assembly calibration is used to determine the actual pressure difference between the two seals. As the confining chamber is pressurized in stages, the control unit changes the intermediate pressure target and records the driving force or resistance to rod movement required for low-speed trial operation. When the first and second pressure differentials are distributed in different ratios, the resistance to rod movement and the sealing leakage state may change. The control unit selects a pressure distribution coefficient α that minimizes the resistance to rod movement and meets the required pressure attenuation, without exceeding the allowable pressure difference between the two seals.

[0093] When the conditions for testing the rod driving force are not available, the initial pressure distribution coefficient can be determined based on the allowable pressure difference, material hardness, contact length, and preload conditions of the seal design. This coefficient can then be corrected after multiple tests based on the intermediate pressure holding decay and seal maintenance records. The corrected pressure distribution coefficient is associated with the corresponding seal batch to avoid continuing to use an incompatible intermediate pressure target after replacing the seal.

[0094] Through the above calibration, the coupled pressure target, differential pressure corridor, and trend adjustment parameters of this invention all have traceable engineering origins. The control unit does not need to apply a fixed set of parameters to all tests, but can select corresponding parameters based on rod specifications, target confining pressure, buffer assembly status, and seal status, thereby adapting the control method to different test conditions.

[0095] The permissible confining pressure fluctuation is determined jointly based on the allowable confining pressure error of the test and the measurement error of the pressure sensor. Specifically, the permissible confining pressure fluctuation should be no less than twice the maximum measurement error of the pressure sensor to avoid misinterpreting measurement noise as actual pressure deviation, and should not exceed the confining pressure error allowed by the test plan. If the pressure sensor has a range of 25 MPa and an accuracy of 0.2% of full scale, the maximum error for a single measurement is 0.05 MPa. When the test plan allows a confining pressure deviation of 0.5 MPa, the allowable deviation of the pressure target can be set to 0.2 MPa, and the pressure fluctuation amplitude threshold can be set to 0.1 MPa. The former is four times the maximum error of the sensor, and the latter is twice the maximum error of the sensor; both are less than the 0.5 MPa confining pressure fluctuation allowed by the test plan.

[0096] The permissible differential pressure range is determined by multiplying the rated permissible differential pressure of the corresponding seal by a sealing safety factor. The sealing safety factor is less than 1, and its specific value is determined based on the dynamic pressure derating requirements provided by the seal supplier or the machine's durability calibration results. The initial value for new seals should also be verified in a step-by-step pressure increase test. For example, if the rated permissible differential pressure of both the inner and outer seals is 15 MPa, and the normal operating differential pressure is limited to 80% of the rated value according to equipment safety design requirements, the sealing safety factor is 0.8. The upper limit for both permissible differential pressure levels is 12 MPa, and the lower limit is 0 MPa, thus the corresponding permissible differential pressure range is 0 to 12 MPa. The emergency differential pressure threshold can be taken as 90% of the rated permissible differential pressure, i.e., 13.5 MPa, making it higher than the normal control upper limit of 12 MPa but lower than the rated permissible differential pressure of 15 MPa.

[0097] The pressure distribution coefficient α is determined based on the relative pressure-bearing utilization rate of the two seals. Let the allowable pressure difference of the inner seal be ΔP. in,max The allowable pressure difference for the outer seal is ΔP. out,max Then we can take α = ΔP out,max / (ΔP in,max +ΔP out,max ), making (P c* -P m* ) / ΔP in,max With (P) m* -P e ) / ΔP out,max Equal. For the target confining pressure P c* =20MPa, external environmental pressure P e Given that the pressure is 0 MPa and the rated allowable pressure difference between the two seals is 15 MPa, we take α = 0.5 to obtain the intermediate pressure target P. m* =10MPa, the first pressure difference and the second pressure difference are both 10MPa, each retaining a rated pressure margin of 5MPa, and falling within the allowable pressure difference range of 0 to 12MPa. If the allowable pressure difference between the inner and outer seals are 18MPa and 12MPa respectively, then α=0.4, the intermediate pressure target is 8MPa, the first pressure difference is 12MPa, and the second pressure difference is 8MPa. The ratio of each to its respective allowable pressure difference is approximately 0.667. Therefore, the pressure distribution coefficient is not fixed at 0.5, but is calculated from the pressure-bearing parameters of the two seals.

[0098] The pressure margin ratio range is used to tolerate pressure detection and pressure regulation errors. The control unit calculates the relative pressure utilization rate r1 of the inner seal, which is calculated as follows: r1 = (P c -P m ) / ΔP in,max The relative pressure utilization rate of the outer seal is r2 = (P m -Pe) / ΔP out,maxThe pressure margin distribution state is represented by ρ = r1 / r2. Ideally, ρ is 1. If the proportional error after considering the combined pressure measurement error and valve control adjustment error does not exceed 10%, the preset proportional range can be set to 0.9 to 1.1. When ρ is lower than 0.9, the intermediate pressure target is reduced; when ρ is higher than 1.1, the intermediate pressure target is increased until ρ returns to the aforementioned proportional range.

[0099] The following provides calculated implementation data for the pressure buffer parameters. This data is calculated from the device's geometric parameters and pressure-volume relationship, and is used to illustrate how the control unit obtains the control target from the input parameters. It does not represent experimental results and does not constitute a limitation on the applicable pressure range of this invention. Assume the rod diameter d is 20 mm, the effective cross-sectional area A of the rod is 314.159 mm², and the target confining pressure P... c* The allowable confining pressure fluctuation is ΔP, which is 20 MPa. allow The pressure is 0.5 MPa; the two pressure buffer components are symmetrically arranged, with a distribution ratio η of 0.5 on each side; the initial effective volume Vg0 of the gas side space on each side is 80 mL, the initial buffer pressure Pg0 is 20 MPa, and the compression index n is 1.4; the effective pressure-bearing area of ​​the buffer piston is 314.159 mm², and the available compensation stroke is 12 mm.

[0100] When the predicted intrusion path L is 3mm, 5mm, and 7mm, the total predicted volume changes calculated according to ΔV=A×L are 0.942mL, 1.571mL, and 2.199mL, respectively, and the volume changes borne by each pressure buffer assembly are 0.471mL, 0.785mL, and 1.100mL, respectively. According to Pg1=Pg0×[Vg0 / (Vg0-ηΔV)] n The calculated predicted gas pressures Pg1 for the three intrusion paths are 20.166 MPa, 20.278 MPa and 20.391 MPa, respectively, with pressure increments of 0.166 MPa, 0.278 MPa and 0.391 MPa, respectively, all of which are less than the allowable confining pressure fluctuation of 0.5 MPa.

[0101] Based on the calculation of the single-sided volume change divided by the effective pressure-bearing area of ​​the buffer piston, the predicted displacements of the buffer piston under the aforementioned three operating conditions are 1.5mm, 2.5mm, and 3.5mm, respectively, with corresponding remaining compensation strokes of 10.5mm, 9.5mm, and 8.5mm, none exceeding the 12mm usable compensation stroke. The three sets of calculation results also show that, with other parameters remaining constant, increasing the predicted intrusion stroke leads to a larger predicted pressure increment and a smaller remaining compensation stroke. Therefore, the control unit simultaneously verifies both the predicted peak pressure and the remaining compensation stroke, rather than verifying only one of these conditions.

[0102] When the effective pressure-bearing areas on the gas and liquid sides of the buffer piston are the same, and the piston friction is relatively small compared to the hydraulic pressure, the compensated gas pressure Pg1 can be approximated as the predicted peak pressure of the confining cavity. If the effective pressure-bearing area Ag on the gas side is different from the effective pressure-bearing area Al on the liquid side, or if the piston friction Ff cannot be ignored, the control unit calculates the predicted cavity pressure Pc1 according to Pc1=(Ag×Pg1+Ff) / Al; when the piston moves in the opposite direction, the sign of Ff changes accordingly. Ag and Al are calculated from the structural dimensions of the buffer piston, and Ff is obtained by pushing the buffer piston at low speed and recording the starting force. Therefore, the pressure-volume relationship can be applied to pistons with equal area and pistons with differential area, without assuming that the gas pressure and the cavity pressure are necessarily equal.

[0103] The compressibility index *n* is determined through low-pressure volumetric perturbation calibration. The control unit sequentially injects 0.2 mL, 0.5 mL, and 1.0 mL of known volumes of hydraulic medium into the confining pressure chamber, recording the buffer pressure and effective gas-side volume before and after each perturbation. The values ​​are then substituted into the pressure-volume relationship to calculate *n*, and the median of the multiple calculations is taken as the compressibility index for this batch of medium under the current temperature conditions. The three injection volumes cover small, medium, and near-predicted single-side volumetric perturbations, reducing random errors caused by calculations at only a single point. When the duration of the impact process is much shorter than the heat exchange time between the gas-side space and the outside environment, *n* can be selected within a range close to the adiabatic index; when the compression process is slow and heat exchange is sufficient, *n* can be selected within a range close to the isothermal index. In the aforementioned calculated data, *n* = 1.4 is used as an example value to represent rapid compression with nitrogen or air; the actual value is subject to the calibration results.

[0104] The preset stroke margin is determined based on the position detection error of the movable separator, the predicted intrusion stroke error, and the mechanical limit safety distance. Its value must not be less than the sum of these three. For example, if the position detection error is 0.2mm, the predicted intrusion stroke error converted to single-side piston displacement is 0.5mm, and the mechanical limit safety distance is 1mm, the preset stroke margin should be at least 1.7mm, which can be rounded up to 2mm. The remaining compensation stroke for the aforementioned three calculation conditions is greater than 2mm, thus meeting the stroke margin requirement.

[0105] S102. When the confining pressure cavity is in a closed and locked state, establish a cavity pressure domain, a buffer pressure domain, and an intermediate pressure domain corresponding to the coupled pressure target group, so that the pressure difference between adjacent pressure domains is kept within the corresponding allowable pressure difference range; when all three pressure domains reach the target and the pressure change trend reaches a steady state, output a loading allow signal.

[0106] The control unit first performs an initial state pre-check. The pre-check includes: the main control solenoid valve 402a, the return solenoid valve 402b, the buffer chamber passage solenoid valve 402c, and the hydraulic pressure dividing oil circuit solenoid valve 402d are all in a safe initial state; the U-shaped chuck 301 is in the unlocked position; the linear slider module 505 is in the allowed closed position; all pressure detection values ​​are within the initial safe range; and there are no abnormalities that hinder closure at the mating surface between the fixed end 101 and the movable end 102 of the cavity.

[0107] After the pre-inspection is passed, the linear slider module 505 drives the movable end 102 of the cavity to move towards the fixed end 101 of the cavity until the two mating end faces are in contact. The reducer and servo motor 305 drive the U-shaped chuck 301 to rotate to the locking position. The control unit confirms that the locking is complete based on servo position feedback or an independent locking position detection element. If the locking is not confirmed, the main control solenoid valve 402a and the hydraulic pressure dividing oil circuit solenoid valve 402d remain in a prohibited pressurization state.

[0108] After the lock-up is confirmed, the control unit establishes a buffer pressure domain. The buffer chamber passage solenoid valve 402c opens, allowing the compressible medium to enter the gas-side space of the first gas buffer chamber 101a and the second gas buffer chamber 102a, pushing the buffer piston 201 to move. The control unit determines whether the buffer piston 201 has reached the initial working position corresponding to the buffer volume target based on the buffer pressure feedback and optional position feedback.

[0109] Once the buffer pressure reaches the target level, the control unit begins to collaboratively establish the cavity pressure domain and the intermediate pressure domain. The main control valve 402a injects hydraulic medium into the confining pressure cavity, while the hydraulic pressure distribution valve 402d injects hydraulic medium into the intermediate pressure cavity. The control unit does not require the two branches to have the same flow rate, but rather determines the flow rate based on the current cavity pressure P. c and the current intermediate pressure P m Real-time calculation of the first pressure difference P c -P m Second pressure difference P m -P e .

[0110] When the first differential pressure approaches the upper boundary of the allowable differential pressure range, the control unit pauses or reduces the opening of the main control solenoid valve 402a and prioritizes increasing the intermediate pressure. When the second differential pressure approaches the upper boundary of the allowable differential pressure range, the control unit reduces the opening of the hydraulic pressure distribution circuit solenoid valve 402d, waits for the cavity pressure to rise, and then continues to build up the intermediate pressure. Thus, the two pressure domains rise together along the path constrained by the differential pressure.

[0111] To balance pressure build-up efficiency and adjustment accuracy when approaching the target, both the chamber pressure and intermediate pressure can be increased in stages. Continuous pressure increase is used when moving away from the target, valve opening is reduced when approaching the target, and intermittent pulse pressure compensation is used after entering the target's vicinity. The segment boundaries are calibrated based on the equipment volume, hydraulic source flow rate, and valve flow characteristics; a fixed ratio is not required.

[0112] After the three pressure domains enter the target neighborhood, the control unit shuts off the corresponding continuous pressure supply path and enters steady-state determination. For each pressure domain, the control unit calculates the pressure deviation, pressure fluctuation amplitude, and pressure change slope within a sliding time window; then, it performs pressure holding decay monitoring. Only when all three pressure domains pass the steady-state determination and pressure holding decay monitoring, and the locking feedback of the U-shaped chuck 301 remains effective, does the control unit output a loading permission signal.

[0113] If the cavity pressure is stable but the intermediate pressure is still decreasing, it indicates a possible leak in the staged sealing branch, and the control unit should prohibit loading. If the buffer pressure decreases while the cavity pressure remains stable, it indicates a possible leak in the gas-side space of the pressure buffer assembly, and the control unit should also prohibit loading. This avoids misjudging the system's readiness solely based on the normal pressure in the confining cavity.

[0114] The control unit can divide the entire process into initial safety, closure, lockout confirmation, buffer pressure building, coordinated pressure building, steady-state confirmation, loading readiness, impact protection, trend stabilization, associated pressure relief, and chamber opening permission states. Each state has entry conditions, execution actions, and exit conditions.

[0115] The initial safety state requires all pressure regulating branches to be in an unloaded state. In the closed state, only the translational drive is allowed to move; pressure build-up in the chamber is not permitted. The lock-up confirmation state only allows entry into the buffer pressure build-up state after the circumferential locking element reaches its locked position. When any pressure range is at an unsafe pressure, the control logic prohibits entry into the chamber-opening permission state.

[0116] The control unit is equipped with program-level protection and independent protection. Program-level protection executes sequential control based on three pressure domains and lock-up positions. Independent protection can be implemented by an independent pressure switch, safety controller, or pressure relief element with a mechanical setpoint, which directly cuts off the pressurization energy and opens a safe pressure relief path when the chamber pressure reaches the overpressure threshold.

[0117] When either the first or second differential pressure exceeds the emergency differential pressure threshold, the control unit does not employ the fixed action of simultaneously shutting down all branches. Instead, it determines which pressure range needs to be increased or decreased to reduce the excessive differential pressure. For example, if the first differential pressure is too large, chamber pressurization can be paused and the intermediate pressure increased; if the second differential pressure is too large, intermediate pressure establishment can be paused or the intermediate pressure can be decreased. If the differential pressure continues to increase after adjustment, overall safety depressurization is performed.

[0118] "Approaching the upper boundary of the allowable differential pressure range" means that the difference between the current differential pressure and the upper boundary is not greater than the differential pressure control protection band. The differential pressure control protection band is the larger of the sum of the maximum measurement errors of two adjacent pressure sensing elements and the pressure change caused by a single minimum control pulse in the intermediate pressure regulating branch. For example, if the maximum measurement error of both pressure sensing elements is 0.05 MPa, and the pressure change caused by a single minimum control pulse is 0.08 MPa, the differential pressure control protection band is 0.10 MPa. For an allowable differential pressure range with an upper boundary of 12 MPa, if the current differential pressure reaches 11.90 MPa, it is determined to be approaching the upper boundary, and differential pressure correction is performed in advance.

[0119] The steady-state determination time window is determined based on the longest stabilization time of the pressure regulation branch. During calibration, the control unit records the time required for the pressure change rate to fall back to the sensor noise range after the main control solenoid valve 402a, return solenoid valve 402b, and hydraulic pressure divider solenoid valve 402d stop operating, and takes the maximum value among the three branches as the shortest observation time. If the longest stabilization time is 1.2s, the sliding time window can be set to 2s. Considering the aforementioned maximum measurement error of the 0.05MPa sensor, the pressure change slope threshold can be set to 0.05MPa / s, and the leakage determination threshold for the 10s pressure holding phase can be set to 0.1MPa. Only when the pressure deviation does not exceed 0.2MPa, the fluctuation amplitude does not exceed 0.1MPa, the change slope does not exceed 0.05MPa / s, and the 10s pressure holding attenuation does not exceed 0.1MPa, is the corresponding pressure domain considered to have reached steady state. The above values ​​should be recalibrated after the pressure source, hydraulic medium, or sensor is replaced.

[0120] The target neighborhood refers to the region where the difference between the current pressure and the target pressure does not exceed the target allowable deviation. With a target confining pressure of 20 MPa and a target allowable deviation of 0.2 MPa, the target neighborhood for the cavity pressure is 19.8 MPa to 20.2 MPa. The control unit can use continuous pressure increase below 19.8 MPa, and switch to pulse pressure compensation after entering the 19.8 MPa to 20.2 MPa range. The pulse duration and pressure stabilization observation time are obtained through valve calibration; for example, control pulses of 20 ms, 50 ms, and 100 ms can be used sequentially to measure the unit pulse pressure change, with an observation time after each pulse not shorter than the aforementioned longest stabilization time. The closer the pressure deviation is to the allowable range boundary, the shorter the selected pulse duration.

[0121] The locking range of the circumferential locking component is determined based on the repeatability error of the locking position sensor or servo encoder. For example, when the repeatability error of the locking position is ±0.2°, the locking range can be set to ±0.5° of the target locking angle, and it is required that the two consecutive sampling periods are within this range.

[0122] The initial safety range and the safety opening conditions use the same pressure determination basis. With the maximum measurement error of the aforementioned pressure sensor being 0.05 MPa, the initial state pre-check requires that the chamber pressure, intermediate pressure, and buffer pressure all not exceed 0.2 MPa gauge pressure, and that each pressure regulating branch be in the unloaded or cut-off position. Only after this initial safety range is met and the circumferential locking element is confirmed to be in the unlocked position will the translational drive element enter the permissible closing state.

[0123] During the pressure build-up phase, the intermediate pressure rises synchronously with the cavity pressure to prevent the inner seals from bearing the entire pressure differential in the initial stage of cavity pressurization. The buffer pressure forms a usable gas-liquid separation interface before the cavity pressure is established to prevent the hydraulic medium from directly entering the gas side space during loading. If the three pressure domains reach their respective targets but the pressure differential does not meet the conditions, the control unit will still not output a loading permission signal.

[0124] S103. In response to the Hopkinson rod loading, a pressure buffer assembly directly hydraulically connected to the confining pressure cavity is used to convert the increase in hydraulic medium volume caused by the rod intrusion into the compression of the compressible medium, thereby passively compensating for the impact transient of the cavity pressure.

[0125] After the Hopkinson bar load trigger terminal outputs a load trigger signal, the control unit establishes an impact protection time window and increases the sampling rate of the chamber pressure. The impact protection time window can be determined based on the bar length, wave velocity, loading device action sequence, or pressure response duration in historical tests.

[0126] When the rod enters the confining pressure cavity, it occupies the original hydraulic medium space within the cavity. The hydraulic medium transfers the volume increase to the liquid-side space of the first gas buffer chamber 101a and the second gas buffer chamber 102a, pushing the buffer piston 201 to move towards the gas-side space. The compressible medium in the gas-side space is compressed and stores energy, thereby converting the volume increase, which was originally concentrated as a pressure peak in the cavity, into the displacement of the buffer piston 201 and the amount of gas compression.

[0127] Because the first gas buffer chamber 101a and the second gas buffer chamber 102a are located inside the pressure-bearing chamber assembly, the compensation path between the liquid-side space and the confining pressure chamber is short, and the buffer piston 201 can be directly driven by the local pressure difference. This passive compensation does not require waiting for the control unit to complete the pressure calculation, nor does it require waiting for the main control solenoid valve 402a or the return solenoid valve 402b to change its opening.

[0128] The impact protection time window is determined based on the propagation distance of the rod from the loading trigger position to the confining pressure cavity and the rod wave velocity. Assuming this propagation distance is 2m and the longitudinal wave velocity of the rod is 5000m / s, the stress wave one-way propagation time is 0.4ms. To cover triggering errors, wavefront arrival, and the main rapid volume change processes, the impact protection time window can be set to five times the one-way propagation time, i.e., 2ms. The cavity pressure sampling frequency should ensure at least 50 sampling points within the time window; under a 2ms time window, the sampling frequency should be no less than 25kHz, and in this example, 50kHz can be used, corresponding to 100 sampling points.

[0129] S104. The cavity pressure response during loading is divided into an impact transient component and a pressure trend component. Active adjustment of the confining pressure cavity is suppressed during the duration of the impact transient component. After the impact transient component decays, the cavity pressure is adjusted according to the pressure trend component, and the intermediate pressure target is updated with the cavity pressure to keep the pressure difference on both sides of the graded sealing assembly within the corresponding allowable pressure difference range.

[0130] The control unit performs trend extraction on the sampling sequence of pressure sensor 401. Let the original cavity pressure be P. c (t), the trend resistance is P. trend (t), then the impact transient component can be expressed as P impact (t)=P c (t)-P trend (t). P trend (t) can be obtained by sliding the median and then performing low-pass processing, or by connecting the steady-state pressure before and after the impact protection time window for estimation.

[0131] When P impact The absolute value of (t) or P c When the rate of change of (t) exceeds the transient judgment threshold, the control unit keeps the trend adjustment trigger channels of the main control solenoid valve 402a and the return solenoid valve 402b closed. Here, "suppression adjustment state" is not equivalent to canceling the overpressure safety protection; if the cavity pressure reaches the independent overpressure protection threshold, the safety relief branch can still operate directly.

[0132] After the impact protection time window ends, the control unit continues to monitor the chamber pressure change rate. When the pressure change rate falls back below the trend adjustment threshold, it indicates the end of the rapid volume change phase. At this point, if P... trend (t) If the pressure is below the allowable range of the target confining pressure, the control unit opens the main control solenoid valve 402a with a short pulse to replenish the hydraulic medium; if P trend If the pressure (t) exceeds the allowable range, the control unit opens the return fluid control valve 402b with a short pulse to discharge a small amount of hydraulic medium. A pressure stabilization observation time is set after each pulse to avoid oscillation caused by continuous operation.

[0133] During the trend adjustment period, the intermediate pressure target is not maintained at the fixed value before the test, but is adjusted according to the current P. trend (t) Update. The hydraulic pressure differential circuit electronic control valve 402d performs pressure replenishment or pressure relief according to the updated intermediate pressure target, so that the first pressure difference and the second pressure difference continue to be within the allowable pressure difference range.

[0134] When the rod exits the confining cavity or the cavity volume is restored, the pressure in the liquid-side space decreases, and the compressible medium releases the aforementioned compression energy, pushing the buffer piston 201 back into the liquid-side space. The bidirectional movement of the buffer piston 201 allows the pressure buffer assembly to both absorb the pressure rise corresponding to the increase in volume and compensate for the pressure drop corresponding to the recovery of volume.

[0135] Before the test, the control unit generates a predicted pressure response based on the predicted volume change, the target buffer pressure, and the target buffer volume. The predicted pressure response is not a single curve, but rather a response envelope that takes into account sensor errors, rod intrusion stroke errors, and compressible medium state errors.

[0136] This embodiment also includes buffer state diagnosis. A predicted response envelope for the cavity pressure is generated based on the pressure-volume relationship and the rod intrusion characteristic parameters. The peak cavity pressure, peak occurrence time, and transient decay characteristics collected during loading are compared with the predicted response envelope. When the cavity pressure response exceeds the predicted response envelope, based on the combined state of buffer pressure decay, cavity pressure holding decay, and intermediate pressure change, compressible medium leakage, obstruction of movable separator movement, or leakage of the staged sealing assembly is identified, and at least one of the following is executed: prohibiting reloading, depressurizing the associated pressure domain, and triggering a fault alarm.

[0137] During loading, the control unit extracts the peak value, peak occurrence time, impact transient duration, and transient decay characteristics of the measured chamber pressure and compares them with the predicted response envelope. If the measured peak value is higher than the upper boundary of the predicted envelope and the buffer pressure is lower than the target range, it may indicate a leak in the gas-side space or insufficient pre-charge pressure; if the measured peak value is higher than the upper boundary of the predicted envelope, the buffer pressure is normal but the transient duration is prolonged, it may indicate that the movement of the buffer piston 201 is obstructed; if the chamber pressure and the intermediate pressure decay rapidly at the same time, it may indicate a leak in the confining pressure chamber or the staged sealing assembly.

[0138] To avoid false alarms based on a single pressure deviation, the control unit uses a combination of states for diagnosis. The combination of states includes at least a buffer pressure decay state, a chamber pressure holding decay state, and an intermediate pressure change state. Different combination states correspond to different fault indicators, and these fault indicators are associated with corresponding safety actions.

[0139] When insufficient buffer pressure is detected, the control unit prohibits reloading and first reduces the cavity pressure before releasing the buffer pressure; when the movable partition is suspected of being obstructed, the control unit records the impact response and prompts for checking the pressure buffer assembly; when a graded seal leak is detected, the control unit reduces the cavity pressure and intermediate pressure in a direction that does not increase the first and second pressure differentials.

[0140] The control unit stores the predicted response envelope, measured pressure response, diagnostic results, and valve operating status in association with the test number. After maintenance is completed, the predicted response baseline can be re-established through low-pressure trial operation to accommodate seal replacement or changes in hydraulic medium.

[0141] The pressure regulation branch calibration is used to determine the relationship between the control input of each solenoid valve and pressure changes. Without installing test pieces or using calibration pieces, the control unit drives the main solenoid valve 402a, the return solenoid valve 402b, and the hydraulic pressure divider solenoid valve 402d with multiple incremental short-duration control pulses, recording the net pressure change before and after each pulse. Based on the net pressure change, valve action duration, and corresponding pressure range, local response models for the injection branch, return branch, and intermediate pressure regulation branch are established.

[0142] The local response model is used to determine the pulse duration and pulse interval during the trend adjustment phase. When the pressure deviation is large, the control unit selects the pulse with the larger net pressure change; when the pressure deviation is close to the allowable range boundary, the control unit selects the pulse with the smaller net pressure change. If the pressure change direction caused by two consecutive pulses is inconsistent with the expected direction, the control unit stops the adjustment of that branch and outputs a valve or pressure source abnormality indicator.

[0143] Pressure trend extraction parameter calibration is used to separate the impact transient and pressure trend on a time scale. The control unit selects the steady-state segment before loading triggering, the rapid change segment during impact, and the recovery segment after impact from historical tests, and statistically analyzes the pressure change rate and duration for each segment. The transient judgment threshold is set between the steady-state change rate distribution and the impact change rate distribution, and the impact protection time window covers the rapid change segment but does not excessively extend into the recovery segment.

[0144] After each test, the control unit can use the measured data to correct the predicted response envelope. Only when no leakage alarms occur in any of the three pressure domains, no movement obstruction indicators appear on the movable separators, and the pressure detection components are functioning normally, is the data included in the normal sample. Abnormal samples are stored separately and used to update fault response characteristics; they are not used to relax the normal predicted response envelope.

[0145] The transient judgment threshold and trend adjustment threshold are determined by the distribution interval between the valve-controlled pressure change rate and the impact pressure change rate. First, the injection and return branches are driven without impact loading to obtain the maximum pressure change rate R that the valve-controlled action may produce. valve,max Then, the minimum pressure change rate R during the impact phase is obtained based on low-energy calibration loading or historical normal tests. impact,min Transient determination threshold R impact,th R should be satisfied valve,max <R impact,th <R impact,min Trend adjustment threshold R trend,th Not greater than R valve,max Assume that the calibration yields R. valve,max 2MPa / s, R impact,min If it is 20 MPa / s, then R can be impact,th Set to 6MPa / s, R trend,th Set to 2MPa / s. This set of values ​​is only used to illustrate the threshold selection relationship; the actual threshold should be replaced by the calibration results of the corresponding equipment.

[0146] The filtering parameters for the pressure trend component are determined based on the sampling frequency and the impact protection time window. At a sampling frequency of 50kHz, a sliding median filter with a length of 5 sampling points can be used first to remove single-point anomalies, followed by low-pass processing with a cutoff frequency of 1kHz to obtain P. trend (t). The median sliding length corresponds to a 0.1ms impact protection time window, which is less than 2ms; the 1kHz cutoff frequency is used to suppress impact spikes while retaining confining pressure trend changes over a longer period. If the valve response speed or rod wave velocity changes, the filter length and cutoff frequency should be reselected, and the separation of the two on the time scale should be verified by the valve control response under no-load conditions and the low-energy loaded response.

[0147] The predicted response envelope is formed based on the propagation of input parameter errors. Taking the aforementioned 5mm predicted intrusion stroke condition as an example, if the rod intrusion stroke error is ±0.2mm, the calibration error of the compression index n is ±0.05, the initial effective volume error is ±1mL, and the maximum measurement error of the pressure sensor is ±0.05MPa, then by substituting the upper and lower boundaries of each error into the pressure-volume relationship, the predicted peak pressure envelope, including the measurement error, can be obtained as approximately 20.20MPa to 20.36MPa. When the measured peak value exceeds this envelope, the control unit combines buffer pressure attenuation, cavity pressure holding attenuation, and intermediate pressure changes for combined diagnosis, avoiding drawing fault conclusions based solely on a single peak value.

[0148] The predicted response envelope also includes the peak occurrence time and transient decay characteristics. The center value of the peak occurrence time is determined by dividing the propagation distance from the loading trigger position to the confining pressure cavity by the rod wave velocity. The lower boundary of the time envelope is the center value minus the trigger synchronization error, and the upper boundary of the time envelope is the center value plus the impact protection time window. Taking the aforementioned propagation distance of 2m, wave velocity of 5000m / s, trigger synchronization error of 0.05ms, and impact protection time window of 2ms as an example, the peak occurrence time envelope is from 0.35ms to 2.40ms after loading triggering. The transient decay characteristics are obtained through normal calibration loading: for no less than ten low-energy loadings without leakage or jamming, the time required for the impact transient component to decay to 10% of the peak value is recorded. The median value of each decay time plus three times the median absolute deviation is used as the upper boundary of the decay time. For example, if the decay time obtained from ten calibrations is distributed between 2.8ms and 3.6ms, the upper boundary of the decay time can be rounded up to 4ms. This example illustrates the rules for generating the envelope; the actual envelope should be generated from the local calibration data.

[0149] When the target buffer pressure is 20 MPa, the buffer failure threshold can be set to 90% of the target value, i.e., 18 MPa; below this value, the possibility of buffer medium leakage or insufficient pre-charge pressure increases.

[0150] The overpressure threshold, buffer failure threshold, and locking interval are determined by the test target, buffer target, and position detection accuracy, respectively. Under the aforementioned target confining pressure of 20 MPa, the program-level overpressure threshold can be set to 20.5 MPa, which is the sum of the target confining pressure and the allowable confining pressure fluctuation. When the pressure-bearing cavity is determined by pressure resistance verification to have a rated pressure of not less than 25 MPa, the action value of the independent pressure relief element can be set to 22 MPa, making it higher than the program-level overpressure threshold but lower than the rated pressure.

[0151] During the loading phase, the buffer pressure domain, through a movable separator, handles the rapid physical response. The trend component of the cavity pressure domain is regulated by the injection and return branches, and the intermediate pressure domain updates with the cavity pressure trend. This relationship avoids requiring the control valve to perform impossible rapid follow-up during the impact transient, and also avoids the intermediate pressure remaining unchanged after a change in cavity pressure.

[0152] S105. After the test is completed, the three pressure domains are depressurized in a manner that keeps the pressure difference between adjacent pressure domains within the corresponding allowable pressure difference range, and the closed locking state is released after all three pressure domains meet the safe opening conditions.

[0153] After the test is completed, the control unit does not immediately unlock the U-shaped chuck 301, but instead enters the associated depressurization state. First, the pressure replenishment action of the main control solenoid valve 402a is stopped, and the return solenoid valve 402b is opened to allow the hydraulic medium in the confining pressure chamber to be discharged through the return branch.

[0154] During the pressure reduction process in the cavity, the control unit continuously updates the intermediate pressure target based on the current cavity pressure. If the first pressure difference approaches the upper boundary of the allowable pressure difference range, the control unit temporarily halts the intermediate pressure reduction and prioritizes lowering the cavity pressure to reduce the difference between the cavity pressure and the intermediate pressure. If the second pressure difference approaches the upper boundary of the allowable pressure difference range, the control unit accelerates the reduction of the intermediate pressure and, if necessary, temporarily halts the cavity pressure reduction to reduce the difference between the intermediate pressure and the external ambient pressure. This depressurization trajectory is the opposite of the pressure build-up trajectory, but it is also constrained by the pressure difference corridor.

[0155] Once the chamber pressure drops to the low-pressure return fluid range, the control unit activates the low-pressure gas source connected to the chamber return fluid pressure passage 102f. The low-pressure gas acts on the hydraulic medium and propels it to continue being discharged through the return fluid branch. The low-pressure gas is only used to overcome the return fluid resistance, and its pressure is lower than the confining pressure test pressure and the seal safety pressure.

[0156] After both the pressure range of the chamber and the intermediate pressure range have decreased to the corresponding safe pressure, the control unit opens the electronically controlled valve 402c of the buffer chamber passage to release the remaining pressure in the first gas buffer chamber 101a and the second gas buffer chamber 102a. During the release of the buffer pressure, the chamber pressure is continuously monitored. If the movable partition moves back and causes the chamber pressure to rise again, the pressure release is temporarily slowed and the return liquid branch is reopened.

[0157] When the cavity pressure, intermediate pressure, and buffer pressure are all below their respective safety thresholds, and there is no upward trend in any pressure within the confirmation time window, the control unit generates an unlocking signal. The reducer and servo motor 305 drive the U-shaped chuck 301 to rotate to the unlock position, and the linear slider module 505 then drives the movable end 102 of the cavity away from the fixed end 101 of the cavity.

[0158] If any pressure detection value is in an unsafe state, or if the pressure detection component communication malfunctions, the control unit will keep the U-shaped chuck 301 in the locked position. Unlocking will only be allowed after the pressure detection is restored and the safety conditions are reconfirmed.

[0159] The low-pressure return fluid range is determined based on the condition that the low-pressure gas source pressure can simultaneously overcome the current cavity pressure and the pressure loss of the return fluid branch. Specifically, the low-pressure gas source pressure should be greater than the sum of the current cavity pressure and the pressure loss of the return fluid branch. For example, if the pressure loss of the return fluid branch at rated flow is 0.2 MPa, and a low-pressure gas with a gauge pressure of 0.3 MPa is used to assist the return fluid, the low-pressure return fluid range can be set to a cavity pressure not exceeding 0.1 MPa. At this point, the low-pressure gas can drive the hydraulic medium backflow, while remaining significantly below the aforementioned 12 MPa upper limit for the allowable differential pressure of the seal. After the assisted return fluid is completed, the low-pressure gas source is shut off while the return fluid branch remains connected, allowing the cavity pressure to drop back below the safe threshold.

[0160] The safe opening conditions are determined based on sensor error and residual pressure risk. When the maximum measurement error of the pressure sensor is 0.05 MPa, the safety thresholds for the chamber pressure, intermediate pressure, and buffer pressure can all be set to 0.2 MPa gauge pressure, with a confirmation time window of 3 seconds. It is required that the absolute value of each pressure change rate within this time window does not exceed 0.02 MPa / s. The 0.2 MPa safety threshold is four times the maximum measurement error of the sensor, effectively distinguishing between zero-point noise and actual residual pressure. The 3-second confirmation time window is used to eliminate short-term pressure rises caused by the return movement of the buffer piston. Only when the three pressure values, pressure change rate, and circumferential locking element position feedback simultaneously meet the conditions will the control unit output an unlocking signal.

[0161] The control unit records the entry and exit times, pressure target, actual pressure value, valve action, and opening / closing position for each state. This allows for the reconstruction of the control process after the test and determination of whether the anomaly originated from the pressure source, buffer assembly, sealing assembly, or cavity opening / closing assembly.

[0162] During the depressurization phase, the pressure domain of the cavity and the intermediate pressure domain decrease together along the pressure differential corridor, while the buffer pressure domain is released after the cavity and intermediate pressures drop to a safe range. If the intermediate pressure is released completely first, the inner seal may again bear a large pressure differential; if the buffer pressure is released completely first, the movable partition may push hydraulic medium into the confining cavity as it moves back. Therefore, this invention determines the depressurization sequence based on the physical interaction between the pressure domains.

[0163] From the perspective of control effectiveness, predicting volume change, generating buffer targets, direct hydraulic connection, suppressing valve control during impact, and adjusting trends after impact collectively address the problem of confining pressure impact peak value; intermediate pressure targets, pressure differential corridors, and intermediate pressure following collectively address the problem of graded sealing load distribution; and multi-pressure domain steady-state determination and associated pressure relief collectively address the problems of pressurized loading and pressurized cavity opening. Each technical feature has a clear function and forms a synergy through the same pressure state control chain.

[0164] The aforementioned computational data forms a complete data chain: "Test Input—Volume Change Calculation—Buffer Pressure Prediction—Piston Displacement Verification—Pressure Difference Distribution—Steady-State Determination—Transient Identification—Safe Pressure Relief." Before the actual equipment is put into testing, the example values ​​should be replaced with the equipment nameplate parameters, the rated values ​​provided by the seal supplier, the sensor calibration certificate, and the machine calibration record; after replacement, the control parameters should still be generated according to the calculation relationships and judgment order given in this section.

[0165] This embodiment also provides a Hopkinson bar confining pressure coordinated control device with pressure divider, such as... Figures 1 to 4 As shown, the confining pressure coordinated control device in this embodiment includes a pressure-bearing cavity assembly, a pressure buffer assembly, a graded sealing assembly, a cavity opening and closing assembly, a pressure regulating assembly, a pressure detection assembly, a support assembly, and a control unit.

[0166] The pressure-bearing cavity assembly includes a fixed cavity end 101 and a movable cavity end 102. The fixed cavity end 101 and the movable cavity end 102 are arranged coaxially along the axial direction of the split Hopkinson rod 601. After they are joined, a static end face seal is formed by a cavity sealing ring 103 provided at the joining end face, which together defines a confining pressure cavity for accommodating the test specimen 602 and the hydraulic medium. The fixed cavity end 101 corresponds to the fixed cavity part in this embodiment, and the movable cavity end 102 corresponds to the movable cavity part in this embodiment.

[0167] The fixed end 101 of the cavity is provided with a first gas buffer chamber 101a, a first buffer chamber passage 101b, and a first hydraulic pressure dividing oil passage 101c. The movable end 102 of the cavity is provided with a second gas buffer chamber 102a, a second buffer chamber passage 102b, and a second hydraulic pressure dividing oil passage 102c. The two gas buffer chambers are located on opposite axial sides of the confining pressure cavity, allowing the volume change within the confining pressure cavity to be distributed to both sides.

[0168] like Figure 5 As shown, buffer pistons 201 are respectively installed in the first gas buffer chamber 101a and the second gas buffer chamber 102a. The buffer pistons 201 divide the corresponding gas buffer chambers into gas-side spaces and liquid-side spaces. The liquid-side space is directly connected to the confining pressure chamber through a connecting area inside the pressure-bearing chamber assembly, and the gas-side space is connected to an external compressible medium source through the first buffer chamber passages 101b and 102b.

[0169] A piston sealing ring 203 is provided on the outer periphery of the buffer piston 201 to maintain a dynamic seal between the gas-side space and the liquid-side space. A self-locking nut 202 is provided at the tail of the buffer piston 201. The self-locking nut 202 limits the maximum axial displacement of the buffer piston 201 and prevents the buffer piston 201 from leaving the predetermined working range. The self-locking nut 202 can also be replaced by a limiting ring, a limiting step, or other axial limiting components connected to the buffer chamber.

[0170] The buffer piston 201 is one implementation of a movable separator. The movable separator can also be a diaphragm, bellows, or flexible bladder that seals against the inner wall of the buffer chamber. When using a diaphragm, bellows, or flexible bladder, the gas-side space and liquid-side space should be isolated from each other, and the liquid-side space should directly receive the volume changes of the confining chamber. Therefore, the "movable separator" in this embodiment is not limited to a specific piston shape.

[0171] The graded sealing assembly is positioned at the fixed end 101 and the movable end 102 of the cavity through the split Hopkinson rod 601. Taking the one-sided penetration position as an example, a cavity sealing ring 103 and a hydraulic pressure dividing oil circuit sealing ring 104 are sequentially arranged along the direction from the confining cavity towards the external environment. The annular space between the cavity sealing ring 103 and the hydraulic pressure dividing oil circuit sealing ring 104 forms an intermediate pressure chamber, which is connected to either the first hydraulic pressure dividing oil circuit 101c or the second hydraulic pressure dividing oil circuit 102c.

[0172] The cavity sealing ring 103 corresponds to the inner seal, and the hydraulic pressure distribution oil circuit sealing ring 104 corresponds to the outer seal. In actual implementation, two or more intermediate pressure chambers can be set between two or more seals to form three or more levels of pressure distribution. As long as the intermediate pressure chamber can be controlled to establish a pressure between the cavity pressure and the external ambient pressure, graded pressure bearing can be achieved.

[0173] The cavity opening and closing assembly includes a U-shaped chuck 301, a rotary gear 302, a power gear 303, a support bearing 304, a reducer and servo motor 305, and a linear slider module 505. A flange 101d is provided at the end of the cavity fixed end 101, and a notched flange 102g is provided at the end of the cavity movable end 102.

[0174] A U-shaped chuck 301 is arranged around the outer sides of flange 101d and notched flange 102g. A reducer and servo motor 305 drive the U-shaped chuck 301 to rotate circumferentially via a power gear 303 and a rotary gear 302. When the U-shaped chuck 301 rotates until its opening aligns with the notch of the notched flange 102g, the movable end 102 of the cavity can move axially; when the U-shaped chuck 301 rotates until its pressure-bearing part axially overlaps with the notched flange 102g, it forms an axial constraint on the movable end 102 of the cavity.

[0175] In this embodiment, the U-shaped chuck 301 is generally considered as a circumferential locking component. The reducer, servo motor 305, power gear 303, and rotary gear 302 together constitute the locking drive component, and the linear slider module 505 constitutes the translation drive component. The circumferential locking component can also be a rotary locking ring, a split clamp, or other locking structures that can form axial constraints after circumferential movement; the locking drive component can also be a hydraulic motor, a pneumatic actuator, or a linear actuator in conjunction with a conversion mechanism; the translation drive component can also be a hydraulic cylinder, a pneumatic cylinder, or a lead screw module.

[0176] The fixed end 101 of the cavity is mounted on the fixed end support 501 of the cavity via a support cover plate 504. A U-shaped chuck support roller 502 supports the U-shaped chuck 301 and allows it to rotate with low resistance. The movable end 102 of the cavity is mounted on the movable end support 503 of the cavity, which is connected to the linear slider module 505. This support relationship ensures that the fixed end 101 and the movable end 102 of the cavity remain coaxial during opening and closing.

[0177] The pressure regulating assembly includes a main control solenoid valve 402a, a return solenoid valve 402b, a buffer chamber passage solenoid valve 402c, and a hydraulic pressure dividing circuit solenoid valve 402d. The main control solenoid valve 402a is connected to the confining pressure chamber via the high-pressure chamber oil passage 102d and is used to control the injection of hydraulic medium. The return solenoid valve 402b cooperates with the return branch of the confining pressure chamber to control the discharge of hydraulic medium. The chamber return gas pressure passage 102f is used to introduce low-pressure gas into the confining pressure chamber during the low-pressure return phase.

[0178] The buffer chamber passage solenoid valve 402c is connected to the two gas-side spaces via the first buffer chamber passage 101b and the second buffer chamber passage 102b. The two gas-side spaces can be synchronously adjusted by the same buffer chamber passage solenoid valve, or separate regulating valves can be installed to correct for manufacturing differences in the pressure buffer assemblies on both sides. The hydraulic pressure dividing oil circuit solenoid valve 402d is connected to the intermediate pressure chamber via the first hydraulic pressure dividing oil circuit 101c and the second hydraulic pressure dividing oil circuit 102c, and is used to establish and regulate the intermediate pressure.

[0179] The pressure detection assembly includes at least a pressure sensor 401 that acquires the cavity pressure via pressure sensor passage 102e. To perform coordinated control of the three pressure domains, buffer pressure detection elements can also be installed on the first buffer cavity passage 101b and the second buffer cavity passage 102b, and intermediate pressure detection elements can be installed on the first hydraulic pressure dividing oil passage 101c and the second hydraulic pressure dividing oil passage 102c. The buffer pressure detection elements and intermediate pressure detection elements can be installed separately or integrated into a pressure regulating valve or pressure controller with pressure feedback function.

[0180] The control unit can be a programmable logic controller, an industrial controller, or other control equipment with real-time data acquisition and sequential control capabilities. The control unit communicates with the pressure detection assembly, each electrically controlled valve, the reducer and servo motor 305, the position detection components of the linear slider module 505, and the Hopkinson rod loading trigger end.

[0181] The test specimen 602 is positioned between the split Hopkinson bar members 601. Heat-shrinkable sleeves 603 can be installed on the outside of both ends of the specimen to prevent debris from entering the hydraulic passage after the specimen breaks. The heat-shrinkable sleeves 603 do not serve to establish confining pressure, and therefore do not form the main frictional constraint generated by the extrusion of the rubber sleeve in the traditional rubber sleeve confining method.

[0182] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. The scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for coordinated control of confining pressure with a Hopkinson bar and voltage divider, characterized in that, Includes the following steps: Based on the target confining pressure, allowable confining pressure fluctuation, rod intrusion characteristic parameters, and pressure bearing characteristic parameters of the graded sealing assembly, a coupled pressure target group of cavity pressure, buffer pressure, and intermediate pressure is formed; When the confining pressure cavity is in a closed and locked state, a cavity pressure domain, a buffer pressure domain, and an intermediate pressure domain corresponding to the coupled pressure target group are established respectively, so that the pressure difference between adjacent pressure domains is kept within the corresponding allowable pressure difference range; when all three pressure domains reach the target and the pressure change trend reaches a steady state, a loading allow signal is output. In response to the Hopkinson rod loading, a pressure buffer assembly directly hydraulically connected to the confining pressure cavity is used to convert the increase in hydraulic medium volume caused by the rod intrusion into the compressibility of the compressible medium, thereby passively compensating for the impact transient of the cavity pressure. The cavity pressure response during loading is divided into an impact transient component and a pressure trend component. Active adjustment of the confining pressure cavity is suppressed during the duration of the impact transient component. After the impact transient component decays, the cavity pressure is adjusted according to the pressure trend component, and the intermediate pressure target is updated with the cavity pressure to keep the pressure difference on both sides of the staged sealing assembly within the corresponding allowable pressure difference range. After the test is completed, the three pressure domains are depressurized in a manner that keeps the pressure difference between adjacent pressure domains within the corresponding allowable pressure difference range, and the closed locking state is released after all three pressure domains meet the safe opening conditions.

2. The method according to claim 1, characterized in that, The determination of the buffer pressure in the target group of coupling pressure includes: The predicted volume change corresponding to the rod's intrusion into the confining pressure cavity is determined based on the rod's cross-sectional area and the predicted intrusion stroke. Establish the pressure-volume relationship of a compressible medium from the initial buffer state to the compensated state. Under the constraint that the predicted volume change is jointly absorbed by the pressure buffer components on both sides of the confining cavity, calculate the predicted peak pressure corresponding to different buffer pressures and different effective buffer volumes. The target buffer pressure and effective buffer volume are determined from a combination of conditions that ensure the predicted peak pressure is no higher than the sum of the target confining pressure and the allowable confining pressure fluctuation, and that the predicted displacement of the movable separator in the pressure buffer assembly does not exceed the available compensation stroke.

3. The method according to claim 1, characterized in that, The determination of the intermediate pressure in the coupled pressure target group includes: Determine the allowable pressure difference between the inner seal near the confining cavity and the outer seal near the external environment in the graded sealing assembly, respectively; Under the constraint that the first pressure difference between the cavity pressure domain and the intermediate pressure domain does not exceed the allowable pressure difference of the inner seal and the second pressure difference between the intermediate pressure domain and the external environment does not exceed the allowable pressure difference of the outer seal, the total pressure difference is distributed according to the pressure margin of the inner seal and the outer seal to obtain the intermediate pressure target. When the cavity pressure changes, the intermediate pressure target is updated accordingly to keep the pressure margin ratio of the first pressure difference to the second pressure difference within a preset ratio range.

4. The method according to claim 1, characterized in that, The establishment of cavity pressure domains, buffer pressure domains, and intermediate pressure domains corresponding to the coupled pressure target group, respectively, to maintain the pressure difference between adjacent pressure domains within the corresponding allowable pressure difference range, includes: First, establish a buffer pressure domain so that the movable separator in the pressure buffer assembly forms a gas-liquid separation interface within the available compensation stroke. According to the segmented pressure rise curve, the cavity pressure domain and intermediate pressure domain are established synchronously. During the cavity pressure rise process, the synchronous pressure command of the intermediate pressure domain is generated based on the current value of the cavity pressure. When the first pressure difference between the cavity pressure domain and the intermediate pressure domain reaches the upper boundary of the corresponding allowable pressure difference range, the pressure increase of the confining cavity is paused and the intermediate pressure is increased; when the second pressure difference between the intermediate pressure domain and the external environment reaches the upper boundary of the corresponding allowable pressure difference range, the rate of increase of the intermediate pressure is reduced or the establishment of the intermediate pressure is paused until both the first pressure difference and the second pressure difference return to their respective allowable pressure difference ranges.

5. The method according to claim 1, characterized in that, The pressure change trend has reached a steady state, including: Within the sliding time window, calculate the fluctuation amplitude, change slope, and pressure holding attenuation of the cavity pressure, buffer pressure, and intermediate pressure respectively. When the pressure deviation of each pressure domain is within the allowable range of the corresponding target value, the fluctuation amplitude and the change slope do not exceed the corresponding steady-state threshold, the pressure holding attenuation does not exceed the corresponding leakage judgment threshold, and the locking position feedback of the cavity opening and closing component remains within the locking range, it is determined that the loading ready state has been reached. If any condition is not met, the load enable signal shall be prohibited from being output, and a fault indicator shall be output according to the pressure range or lock position corresponding to the unmet condition.

6. The method according to claim 1, characterized in that, The process of dividing the cavity pressure response during loading into an impact transient component and a pressure trend component includes: An impact protection time window is established based on the Hopkinson rod loading trigger signal, and the rate of change of the cavity pressure sampling sequence within the impact protection time window is determined. Pressure responses with a rate of change exceeding the transient determination threshold are identified as the impact transient component, and pressure responses with a low rate of change retained after time window smoothing are identified as the pressure trend component. During the impact protection time window, the trigger channels for pressure replenishment regulation and fluid return regulation are closed, and passive volume compensation is performed by the pressure buffer component. After the impact protection time window ends and the rate of change of cavity pressure falls back to the trend regulation threshold, pressure replenishment regulation or fluid return regulation is resumed according to the pressure trend component.

7. The method according to claim 6, characterized in that, It also includes buffer status diagnostics: A predicted response envelope for the cavity pressure is generated based on the pressure-volume relationship of the compressible medium in the pressure buffer assembly and the rod intrusion characteristic parameters. The peak pressure of the cavity, the time of peak occurrence, and the transient decay characteristics collected during loading are compared with the predicted response envelope; When the cavity pressure response exceeds the predicted response envelope, based on the combination of buffer pressure decay, cavity pressure holding decay, and intermediate pressure change, the system identifies compressible medium leakage, obstruction of movable separator movement, or leakage of graded sealing assembly, and executes at least one of the following: prohibiting reloading, depressurizing associated pressure domains, and fault alarm.

8. The method according to claim 1, characterized in that, The associated depressurization of the three pressure domains includes: Stop supplying hydraulic medium to the confining pressure cavity, open the return fluid branch of the confining pressure cavity, and synchronously reduce the intermediate pressure target according to the cavity pressure drop process, so that the pressure difference between the cavity pressure domain and the intermediate pressure domain, as well as the pressure difference between the intermediate pressure domain and the external environment, are kept within the corresponding allowable pressure difference range. After the pressure in the cavity drops to the return fluid auxiliary pressure range, low-pressure gas is introduced into the confining pressure cavity to push the hydraulic medium out through the return fluid branch. After the pressure in the cavity and the intermediate pressure domains drops to their respective safe pressures, the remaining pressure in the buffer pressure domain is released. When the cavity pressure, intermediate pressure, and buffer pressure are all below their respective safety thresholds, and the rate of change of each pressure remains stable, an unlocking signal is generated.

9. The method according to claim 1, characterized in that, This also includes state interlocking throughout the entire process: Before closing the cavity, confirm that the pressure regulating branch is in an unloaded state and that the cavity opening and closing components are in the allowable closing position. When any pressure domain is in an unsafe pressure state, the cavity opening and closing component is prohibited from performing the unlocking action, and the cavity pressure domain is prohibited from being established when the cavity opening and closing component has not reached the locking position. When the chamber pressure exceeds the overpressure threshold, the pressure difference between any adjacent pressure domains exceeds the emergency pressure difference threshold, the buffer pressure is lower than the buffer failure threshold, or the lock-up position feedback is abnormal, pressurization is stopped, the corresponding pressure regulation branch is controlled in the direction that prevents the pressure difference between adjacent pressure domains from continuing to expand, and an alarm is output. Record the target value, actual value, action status, closure and lock-up status, and loading trigger time of each pressure domain.

10. A Hopkinson bar confining pressure cooperative control device with pressure divider, used to execute the method according to any one of claims 1 to 9, characterized in that, include: The pressure-bearing cavity assembly includes a fixed cavity portion and a movable cavity portion that are axially joined together, wherein the fixed cavity portion and the movable cavity portion together form a confining pressure cavity through which the Hopkinson rod body passes when closed; Pressure buffer assemblies are integrated on both axial sides of the confining pressure cavity. Each pressure buffer assembly includes a buffer cavity and a movable partition disposed within the buffer cavity. The movable partition divides the buffer cavity into a gas-side space for containing a compressible medium and a liquid-side space for containing a hydraulic medium. The liquid-side space is directly hydraulically connected to the confining pressure cavity so that the movable partition moves in response to changes in the volume of the confining pressure cavity. A graded sealing assembly is provided at the position where the rod penetrates the pressure-bearing cavity assembly, including at least two seals spaced apart along the direction from the confining pressure cavity to the external environment and an intermediate pressure cavity located between adjacent seals, wherein the intermediate pressure cavity is connected to an intermediate pressure regulating branch. The cavity opening and closing assembly includes a circumferential locking member for limiting the axial separation of the fixed cavity portion and the movable cavity portion, a locking drive member for driving the circumferential locking member to move between a locked position and an unlocked position, and a translation drive member for driving the movable cavity portion to move axially. The pressure regulating assembly includes an injection branch and a return branch connected to the confining pressure cavity, a buffer pressure regulating branch connected to the gas-side space, and the intermediate pressure regulating branch. Pressure detection components are used to collect chamber pressure, buffer pressure, and intermediate pressure; The control unit is communicatively connected to the pressure detection component, the pressure regulation component, and the cavity opening and closing component, respectively, for establishing and coordinating the cavity pressure domain, the buffer pressure domain, and the intermediate pressure domain, controlling the passive compensation during the impact transient and the pressure trend adjustment after the impact transient decay, and performing state interlocking for pressure building, loading permission, associated pressure relief, and cavity opening and closing.

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