Multivariate Numerical Analysis Method and System Based on TEHB Test System

Abstract

The present invention provides a multivariate numerical analysis method and system based on a TEHB test system. The multivariate numerical analysis method of the present invention includes the following steps: multi-directional synchronous impact test numerical simulation step: establishing a rock numerical model with a real mineral texture and breakable mineral crystals, and constructing a uniaxial two-way synchronous impact test simulation framework for performing multi-directional synchronous impact test numerical simulation on the rock numerical model; dynamic response index calculation step: separating and recombining the monitored incident wave signal and reflected wave signal to obtain the dynamic response index of the rock numerical model during the impact process; multivariate parameter intelligent analysis step: during the multi-directional synchronous impact test numerical simulation, the spatial distribution characteristics of different types of cracks are displayed in real time, and intelligent mesoscopic analysis of crack evolution, rock damage and energy characteristics is realized. The present invention can simulate the dynamic mechanical behavior of rocks under impact loads and more intuitively display the real-time fracture information inside the rocks.

Description

Technical Field

[0001] The present invention relates to the technical field of rock dynamics research, and particularly relates to a multi - variable numerical analysis method and system based on a TEHB test system. Background Art

[0002] With the advent of the era of deep resource exploitation, the geological environment of engineering rock masses has become increasingly complex, and the problem of dynamic disturbance has become increasingly severe. In the deep environment of high stress, high temperature, high pressure and dynamic disturbance, rocks not only bear high in - situ stress, but also suffer from dynamic disturbance effects caused by factors such as mining activities, engineering blasting and geological tectonic movements. Dynamic disturbances usually have characteristics such as high strain rate and multi - axial loading, and are extremely likely to induce typical dynamic disasters such as rock bursts, rock bumps and coal and gas outbursts. Dynamic disasters are often closely related to the rapid propagation of micro - cracks in rock masses, stress concentration and the suddenness of local damage, and highly depend on the dynamic response of rock masses under high strain rate and complex multi - axial stress conditions. At present, the relevant research devices mainly include various types of Hopkinson bar systems. As the latest developed device, the true triaxial electromagnetic Hopkinson bar (TEHB) test system can realize the simulation of dynamic disturbance with high strain rate, multi - axial multi - direction and synchronous loading, and can truly reproduce the dynamic response of rocks in a complex stress environment in the laboratory. However, there are still deficiencies in the data monitoring and analysis of this test system. The initiation, propagation and penetration of internal cracks in rocks during the dynamic loading process often occur in microseconds or even nanoseconds. Limited by the response speed and signal acquisition frequency of traditional acoustic emission monitoring methods, it is difficult to accurately capture and real - time monitor the micro - fracture information of rocks. More importantly, the types of data that can be collected by traditional monitoring means are relatively single, mainly focusing on macroscopic mechanical indexes such as stress and strain, and it is difficult to explore the evolution process of internal micro - cracks and mesoscopic characteristics such as fracture modes of rocks under dynamic disturbance, which restricts the in - depth analysis of the dynamic fracture process and dynamic fracture mechanism of rocks. Summary of the Invention

[0003] To solve the problems in the prior art, the present invention provides a multi - variable numerical analysis method based on a TEHB test system, and also provides a multi - variable numerical analysis system. Based on the measured data of the electromagnetic Hopkinson bar test system, through multi - directional synchronous impact test numerical simulation, dynamic response index calculation, and multi - variable parameter intelligent meso - analysis module, the present invention can efficiently simulate and analyze the dynamic mechanical behavior of rocks under dynamic disturbance, accurately capture the entire process of dynamic failure from the initiation, propagation to penetration of micro - cracks, achieve comprehensive intelligent analysis of multi - variable characteristics, make up for the shortcomings of the dynamic true - triaxial electromagnetic Hopkinson bar test system in monitoring and analysis, improve the understanding of the meso - scale failure mechanism of rocks under impact loading, and provide strong technical support for rock dynamics research, disaster prediction, and engineering safety protection.

[0004] The multi - variable numerical analysis method based on the TEHB test system of the present invention includes the following steps:

[0005] Step of multi - directional synchronous impact test numerical simulation: Establish a rock numerical model with real mineral composition and breakable mineral crystals, and construct a dynamic true - triaxial electromagnetic Hopkinson bar test system including a simulation framework for uniaxial two - way synchronous impact test to perform multi - directional synchronous impact test numerical simulation on the rock numerical model;

[0006] Step of dynamic response index calculation: Separate and recombine the monitored incident wave signal and reflected wave signal to obtain the dynamic response indexes of the rock numerical model during the impact process, and the dynamic response indexes include dynamic balance coefficient, strain rate, strain, and stress;

[0007] Step of multi - variable parameter intelligent analysis: During the multi - directional synchronous impact test numerical simulation, real - time display the spatial distribution characteristics of different types of cracks, and realize the intelligent analysis of crack evolution, rock damage, and energy characteristics.

[0008] The step of multi - variable parameter intelligent analysis includes the following sub - steps:

[0009] C1: Define the failure criteria for different contacts, group and display the already - damaged contacts. The contacts include the boundary contacts and internal contacts of mineral crystals;

[0010] C2: Track and count the number of various cracks and calculate the damage degree. The calculation formula is as follows:

[0011]

[0012] Among them, D represents the damage degree of the rock numerical model during the impact process, c1 and c2 respectively represent the inter - granular failure and trans - granular failure of mineral crystals, f represents the total number of contacts inside the rock sample, represents the proportion of inter - granular failure of mineral crystals, Indicates the proportion of transgranular failure of mineral crystals.

[0013] Furthermore, the method for establishing the rock numerical model is as follows:

[0014] A1: Use the discrete element UDEC program to generate standard rock specimens of a set size, and perform block division on the interior of the rock specimens using a spatial segmentation algorithm to form a series of numerical model blocks, with each numerical model block corresponding to a mineral crystal;

[0015] A2: Output a.txt type file recording the number, central coordinates of each numerical model block, and each contact number generated for each numerical model block;

[0016] A3: Screen the numerical model blocks based on the proportion of real mineral content, and then use the range command of the discrete element UDEC program to assign mechanical parameters to the screened numerical model blocks according to different mineral characteristics;

[0017] A4: Connect the center of the numerical model block and each vertex of the numerical model block, further divide the numerical model block, construct the mesoscopic fracture mechanism inside the rock numerical model, and simulate the real rock fragmentation behavior;

[0018] A5: Identify the boundary contacts and internal contacts of the mineral crystals, and for different contact types, assign mechanical parameters to each contact respectively based on experimental data and mineral mechanical properties to obtain the final rock numerical model.

[0019] Furthermore, the uniaxial and biaxial synchronous impact test simulation framework includes titanium rods arranged on the left and right sides of the rock numerical model, with cross-sections matching the contact surface of the rock numerical model. The end faces of the titanium rods that do not contact the rock numerical model on the left and right sides are provided with first viscous boundaries, and the upper and lower sides of the titanium rods are provided with second viscous boundaries. A strain monitoring element is provided in the middle of the titanium rod to capture the stress wave propagation characteristics under the action of impact loads.

[0020] Furthermore, the method for numerical simulation of multi-directional synchronous impact tests is as follows: Based on the characteristics of the dynamic true triaxial electromagnetic Hopkinson bar test system, use semi-sine impact loading to synchronously apply shock waves with the same frequency and equal amplitude at both ends of the titanium rods on both sides of the rock numerical model, so that the stress is uniformly loaded on the rock numerical model. Perform a fast Fourier transform on the time-domain signals collected by the strain monitoring element, convert the stress wave data to the frequency domain, identify the frequency component with the largest amplitude in the spectrum, define it as the main frequency, and calculate the distribution of the spectral energy density in different frequency bands to comprehensively reveal the propagation law, local fluctuation characteristics, and nonlinear attenuation effect of stress waves during the impact loading process.

[0021] Furthermore, in the calculation steps of the dynamic response index, the calculation method of the dynamic response index is as follows:

[0022] B1: Identify the captured strain signals and separate the incident wave and reflected wave in the original waveform;

[0023] B2: Calculate the incident stress at both ends of the rock numerical model and , and detect the stress balance at both ends of the specimen through the stress balance coefficient ;

[0024] B3: Calculate the strain rate , dynamic strain and dynamic stress ,

[0025] The calculation formulas are as follows:

[0026]

[0027] where , respectively represent the cross-sectional areas of the titanium rod and the rock numerical model, represents the elastic modulus of the titanium rod and respectively represent the left incident wave and the left reflected wave, and respectively represent the right incident wave and the right reflected wave, and respectively represent the incident wave velocity and the length of the rock numerical model.

[0028] Furthermore, in the calculation steps of the dynamic response index, it also includes step B4: Visualize the calculated dynamic response index and draw key curves. The key curves include strain rate-time curve, stress-time curve, strain-time curve, and stress-strain curve, intuitively showing the dynamic evolution law of the rock numerical model under impact load.

[0029] Furthermore, in sub-step C1, through the self-programmed Fish program, cross-scale geometric recognition and intelligent classification of cracks are realized. For the contacts determined to be damaged, the c_length command is used to record the length of the damaged contacts, and the normal and shear displacements are obtained through the c_ndis and c_sdis commands respectively, and the fracture inclination angle is calculated. At the same time, the contacts damaged inside the crystal are recorded as transgranular cracks, and the rest are intergranular cracks. Combining the spatial coordinate mapping technology, the crack information is projected onto the global coordinate system to generate a visualized crack distribution map.

[0030] Further, in sub-step C2, the cracks generated during the entire impact process are automatically tracked in a full cycle, the generation, propagation, and aggregation of the cracks are recorded in real time, and the total number of cracks is dynamically counted, providing key data support for rock damage assessment. The multi-parameter intelligent analysis step further includes sub-step C3: calculating the damage degree D based on the rock failure mechanism, and by analyzing the damage rate, locating the critical moment when the damage degree increases fastest, so as to reveal the dynamic failure stress field of the rock, saving the calculation model at the moment when the damage degree rising rate is the largest, and calling the built-in command of the discrete element UDEC program to generate the maximum principal stress field cloud diagram, intuitively showing the stress distribution state and the main control area of failure inside the rock numerical model.

[0031] Further, the multi-parameter intelligent analysis step further includes the following sub-steps:

[0032] C4: Real-time calculation of strain energy density and analysis of evolution law,

[0033] Record the stress in all directions of all mineral crystals in real time, and calculate the strain energy density based on the stress data , gradually calculate the storage state of the strain energy in the numerical model block at each moment, and capture the energy accumulation, dissipation, and release laws of the rock at different moments under the impact load by drawing the strain energy cloud diagram, providing an energy perspective for the study of the rock dynamic failure mechanism.

[0034] Strain energy density The calculation formula of is:

[0035]

[0036] In the formula, represents the bulk modulus of the numerical model block, represents the Poisson's ratio of the numerical model block, , , respectively represent the stresses in the XX, YY, and ZZ directions,

[0037] C5: Precise positioning of grain-level contact forces and intelligent stress analysis,

[0038] Traverse all mineral crystals in the calculation process, record the spatial coordinates, the connected crystal type or number, and the maximum contact force of each contact point in real time, map the contact force peak value and contact position information to a two-dimensional coordinate system, construct a contact force spatial distribution map, set a contact force threshold, and automatically identify and screen potential fracture points, providing data support for in-depth exploration of the grain-level failure mechanism and micro-mechanical response.

[0039] The present invention also provides a multi-parameter numerical analysis system for implementing the multi-parameter numerical analysis method based on the TEHB test system. The multi-parameter numerical analysis system includes:

[0040] Multi-directional synchronous impact test numerical simulation module: used to establish a rock numerical model with a real mineral texture and breakable mineral crystals, and construct a dynamic true triaxial electromagnetic Hopkinson bar test system including a simulation framework for uniaxial two-way synchronous impact test, for performing multi-directional synchronous impact test numerical simulation on the rock numerical model;

[0041] Dynamic response index calculation module: used to separate and recombine the monitored incident wave signal and reflected wave signal, and obtain the dynamic response indexes of the rock numerical model during the impact process, where the dynamic response indexes include dynamic balance coefficient, strain rate, strain and stress;

[0042] Multi-parameter intelligent analysis module: used to display the spatial distribution characteristics of different types of cracks in real time during the multi-directional synchronous impact test numerical simulation, and realize the intelligent analysis of crack evolution, rock damage and energy characteristics,

[0043] The execution method of the multi-parameter intelligent analysis module includes the following sub-steps:

[0044] C1: Define the failure criteria for different contacts, group and display the already failed contacts, where the contacts include the boundary contacts of mineral crystals and the internal contacts of mineral crystals;

[0045] C2: Trace and count the number of various cracks and calculate the damage degree. The calculation formula is as follows:

[0046]

[0047] where D represents the damage degree of the rock numerical model during the impact process, c1 and c2 respectively represent the intergranular failure of mineral crystals and the transgranular failure of mineral crystals, f represents the total number of contacts inside the rock sample, represents the proportion of intergranular failure of mineral crystals, represents the proportion of transgranular failure of mineral crystals.

[0048] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention can accurately restore the characteristics of synchronous and symmetrically loaded stress waves in the electromagnetic Hopkinson bar dynamic test system, and assist in the monitoring and analysis of the dynamic true triaxial electromagnetic Hopkinson bar test system. It can truly reflect the fabric characteristics of rocks and the heterogeneity of mineral crystals and grain boundaries, accurately simulate the dynamic mechanical behavior of rocks under impact loads, more intuitively display the real-time fracture information inside rocks, and thus more accurately evaluate the overall damage degree of rocks. By real-time monitoring of multiple information such as crack evolution, maximum principal stress field, strain energy density field, and grain-level contact force, deeply integrating numerical simulation and physical experiments, realizing synchronous monitoring and data analysis of multiple scales and multiple parameters, improving the monitoring and analysis information of the dynamic true triaxial electromagnetic Hopkinson bar test system, and providing strong technical support for rock dynamics research, disaster prediction, and engineering safety protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following-described drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0050] Figure 1 It is a flowchart of the method of the present invention;

[0051] Figure 2 It is a structural block diagram of the multi-parameter numerical analysis system of the present invention;

[0052] Figure 3 It is a schematic diagram of the simulation frame structure of the dynamic true triaxial electromagnetic Hopkinson bar test system - uniaxial bidirectional synchronous impact test;

[0053] Figure 4 It is a schematic diagram of an embodiment structure of a numerical model of a titanium rod and a rock;

[0054] Figure 5(a) is a schematic diagram of strain signal identification in the calculation steps of dynamic response indexes;

[0055] Figure 5(b) is a schematic diagram of strain signal reconstruction in the calculation steps of dynamic response indexes;

[0056] Figure 5(c) is a schematic diagram of the calculation results of dynamic strain and stress in the calculation steps of dynamic response indexes;

[0057] Figure 6 It is a schematic diagram of the processing results of the multi-parameter intelligent analysis steps;

[0058] Figure 7 It is a comparison diagram of the stress-strain curve of the numerical simulation in the embodiment of the present invention and the results of indoor tests;

[0059] Figure 8 It is a schematic diagram of crack tracking statistics and real-time crack display in an embodiment of the present invention;

[0060] Figure 9 It is a comparison diagram of macro-meso damage characteristics of numerical simulation and indoor test results in an embodiment of the present invention.

[0061] Reference numerals:

[0062] 1 - X+ direction auxiliary slide rail, 2 - X+ direction support platform, 3 - X+ direction confining pressure loading actuator, 4 - X+ direction confining pressure loading frame, 5 - X+ direction electromagnetic pulse gun, 6 - X+ direction electromagnetic pulse gun support base, 7 - X+ direction connecting rod support rod, 8 - X+ direction convex platform, 9 - X+ direction square rod support device, 10 - X+ direction square rod, 11 - central frame, 12 - central support platform, 13 - X - direction square rod, 14 - X - direction square rod support device, 15 - X - direction convex platform, 16 - X - direction connecting rod support rod, 17 - X - direction electromagnetic pulse gun support base, 18 - X - direction electromagnetic pulse gun, 19 - X - direction confining pressure loading frame, 20 - X - direction support platform, 21 - X - direction auxiliary slide rail. Detailed implementation manners

[0063] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs; the terms used in the description of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention; the terms "including" and "having" and any variations thereof in the description and claims of the present invention and the above drawings are intended to cover non-exclusive inclusion. The terms "first", "second", etc. in the description and claims of the present invention or the above drawings are used to distinguish different objects and not to describe a specific order.

[0064] Referring to "embodiment" in the present invention means that specific features, structures or characteristics described in combination with the embodiment may be included in at least one embodiment of the present invention. The appearance of this phrase at various positions in the description does not necessarily refer to the same embodiment, nor is it an exclusive, independent or alternative embodiment that is mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described in the present invention may be combined with other embodiments.

[0065] In order to enable those skilled in the art of the present technology to better understand the present invention solution, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings.

[0066] As Figure 1 shown, the present invention is based on a multi - numerical analysis method of the TEHB test system and includes the following steps:

[0067] S1: Numerical simulation steps of multi - directional synchronous impact test.

[0068] Establish a rock numerical model with a real mineral texture and breakable mineral crystals, and construct a dynamic true - triaxial electromagnetic Hopkinson bar test system including a simulation framework for uniaxial two - way synchronous impact test, which is used to perform numerical simulation of multi - directional synchronous impact test on the rock numerical model;

[0069] S2: Calculation steps of dynamic response indicators.

[0070] Separate and recombine the incident wave signal and the reflected wave signal obtained by monitoring, and obtain the dynamic response indicators of the rock numerical model during the impact process. The dynamic response indicators include dynamic balance coefficient, strain rate, strain and stress;

[0071] S3: Intelligent analysis steps of multi - parameter.

[0072] During the numerical simulation of multi - directional synchronous impact test, the spatial distribution characteristics of different types of cracks are displayed in real - time, and the intelligent analysis of crack evolution, rock damage and energy characteristics is realized.

[0073] As Figure 2 shown, the present invention also provides a multi - parameter numerical analysis system for implementing the multi - parameter numerical analysis method based on the TEHB test system. The multi - parameter numerical analysis system includes:

[0074] Multi - directional synchronous impact test numerical simulation module: used to establish a rock numerical model with a real mineral texture and breakable mineral crystals, and construct a dynamic true - triaxial electromagnetic Hopkinson bar test system including a simulation framework for uniaxial two - way synchronous impact test, which is used to perform numerical simulation of multi - directional synchronous impact test on the rock numerical model;

[0075] Dynamic response indicator calculation module: used to separate and recombine the incident wave signal and the reflected wave signal obtained by monitoring, and obtain the dynamic response indicators of the rock numerical model during the impact process. The dynamic response indicators include dynamic balance coefficient, strain rate, strain and stress;

[0076] Multi - parameter intelligent analysis module: used to display the spatial distribution characteristics of different types of cracks in real - time during the numerical simulation of multi - directional synchronous impact test, and realize the intelligent analysis of crack evolution, rock damage and energy characteristics.

[0077] The execution method of the multi - parameter intelligent analysis module includes the following sub - steps:

[0078] C1: Visualize the spatial distribution characteristics of different types of cracks in real - time.

[0079] Define the failure criteria for different contacts, group and display the failed contacts, where the contacts include the boundary contacts of mineral crystals and the internal contacts within mineral crystals.

[0080] C2: Intelligently track the crack propagation process and quantitatively calculate the degree of rock damage.

[0081] Preferably, the execution method of the multi-parameter intelligent analysis module in this example further includes the following sub-steps:

[0082] C3: Precisely visualize the distribution of the maximum principal stress field at the moment of failure, accurately locate the region of the maximum contact force at the grain level, and reveal the microscopic stress concentration mechanism;

[0083] C4: Real-time monitor and analyze the evolution law of the strain energy density.

[0084] The implementation steps of the present invention are described in detail below in conjunction with specific embodiments.

[0085] As Figure 4 shown, in step S1, the method for establishing a rock numerical model with a real mineral texture and breakable mineral crystals in this example is as follows:

[0086] A1: Use the discrete element UDEC program to generate a standard rock specimen with a length * width of 50 mm * 50 mm, and use a spatial segmentation algorithm to divide the interior of the rock specimen into blocks to ensure the real morphological distribution of the grains, forming a series of numerical model blocks (referred to as blocks), and each numerical model block corresponds to a mineral crystal. The spatial segmentation algorithm in this example is the Voronoi algorithm. Of course, the size of the standard rock specimen can also be set to other sizes according to requirements.

[0087] A2: Through Fish program programming, output a.txt type file recording the number, center coordinates of each numerical model block and each contact number, providing accurate data support for subsequent assignment and simulation calculations.

[0088] A3: Screen the numerical model blocks based on the proportion of real mineral content, distinguish the regions of the numerical model blocks corresponding to different minerals, and then combine the self-programmed Fish assignment module script to use the range command of the discrete element UDEC program to achieve precise screening of mineral phases, and assign mechanical parameters to the screened numerical model blocks according to different mineral characteristics to improve the physical authenticity of the rock numerical model.

[0089] A4: Refined modeling to achieve the characterization of the internal microstructure of mineral crystals.

[0090] Use the self-programmed Fish program to establish the topological connection relationships between the centers of each numerical model block divided by the Voronoi algorithm and each vertex. Through cyclic meshing operations, enhance the microstructural accuracy of the rock numerical model, make its grain-level characteristics clearer, so as to more accurately simulate the fragmentation behavior and truly reproduce the mesoscopic fracture mechanism inside the rock.

[0091] A5: Mesoscopic assignment of contact mechanical parameters.

[0092] Use the self-programmed Fish program to automatically identify the mineral crystal boundary contacts and the contacts inside the mineral crystals in the rock numerical model, and accurately distinguish different contact types. For different contact types, based on experimental data and mineral mechanical properties, assign mechanical parameters to each contact respectively to improve the physical authenticity and calculation accuracy of the model and obtain the final rock numerical model.

[0093] Such as Figure 3 and Figure 4 shown, for the verification example based on experimental data in this embodiment, use the dynamic true triaxial electromagnetic Hopkinson bar test system of the uniaxial two-way synchronous impact test simulation framework for verification and monitoring, and use the numerical simulation of the multi-directional synchronous impact test to perform 1:1 scale modeling. The uniaxial two-way synchronous impact test simulation framework in this example includes a central support platform 12 arranged in the middle, an X+-direction support platform 2 arranged on the left side of the central support platform 12, and an X--direction support platform 20 arranged on the right side of the central support platform 12. A central frame 11 for fixing the rock numerical model is arranged on the central support platform 12. An X+-direction confining pressure loading frame 4 and an X+-direction confining pressure loading actuator 3 for driving the X+-direction confining pressure loading frame 4 to slide along the X+-direction auxiliary slide rail 1 are arranged on the X+-direction support platform 2. An X+-direction electromagnetic pulse gun 5 and an X+-direction electromagnetic pulse gun support base 6 for supporting the X+-direction electromagnetic pulse gun 5 are arranged inside the X+-direction confining pressure loading frame 4. A number of X+-direction square rod support devices 9 for supporting the X+-direction square rod 10 are also arranged on the X+-direction support platform 2. An X+-direction boss 8 is also arranged between the X+-direction electromagnetic pulse gun 5 and the X+-direction square rod 10. In this example, 4 X+-direction connecting rod support rods 7 are also arranged between the fixed plate of the X+-direction confining pressure loading actuator 3 and the central frame 11 to reinforce the entire frame structure.

[0094] On the X - direction support platform 20, there is an X - direction confining pressure loading frame 19 and an X - direction confining pressure loading actuator for driving the X - direction confining pressure loading frame 19 to slide along the X - direction auxiliary slide rail 21. Inside the X - direction confining pressure loading frame 19, there is an X - direction electromagnetic pulse gun 18 and an X - direction electromagnetic pulse gun support base 17 for supporting the X - direction electromagnetic pulse gun 18. On the X - direction support platform 20, there are also several X - direction square rod support devices 14 for supporting the X - direction square rod 13. Between the X - direction electromagnetic pulse gun 18 and the X - direction square rod 13, there is an X - direction boss 15. In this example, 4 X - direction connecting rod support rods 16 are also arranged between the fixed plate of the X - direction confining pressure loading actuator and the central frame 11 to reinforce the entire frame structure.

[0095] As Figure 4 shown, the size of the rock numerical model in this example is 50 mm×50 mm and it has a real fabric. Preferably, both the X + - direction square rod and the X - direction square rod in this example are titanium rods, and their material is non - magnetic TC21 titanium alloy. Titanium rods with a length of 2800 mm and a width of 50 mm are arranged on both sides of the rock numerical model. The titanium rods are set as elastic blocks for propagating stress waves. According to the actually measured physical parameters, the elastic modulus is set to 110 GPa in the rock numerical model, and the density and Poisson's ratio of the material are 4500 kg / m 3 ³ and 0.33 respectively. Use Fish language to edit the script and calculate the set parameters of the rock numerical model. The maximum wave speeds of the P - wave and S - wave can reach 5855 m / s and 3198 m / s respectively, and the frequency in the model can reach at least 160e4 Hz, which can meet the requirements of the dynamic impact test.

[0096] In this example, after constructing the high - strength titanium rods on both sides of the completed rock numerical model, an internal stress wave propagation mechanism is constructed to realize the numerical simulation of the rock mass impact test. Specifically, in this example, the vertical displacement of the titanium rods is fixed. First viscous boundaries are provided on the end faces of the titanium rods on the left and right sides that do not contact the rock numerical model, and second viscous boundaries are provided on the upper and lower side faces of the titanium rods to avoid the interference of the stress wave boundary reflection effect on the test and reduce the influence of the boundary effect on the impact test. A half - sine wave is selected as the incident wave to be consistent with the indoor test. The half - period of the incident wave is 500 μs and the frequency is 100 Hz. In this example, strain monitoring points are arranged in the middle of the titanium rods on both sides, 1500 mm away from the rock numerical model, and strain monitoring elements are provided to capture the stress wave propagation characteristics under the action of the impact load.

[0097] After constructing the internal stress wave propagation mechanism, an impact load is input to simulate multi-directional and synchronous impact effects. The method for numerical simulation of multi-directional synchronous impact tests is as follows: Based on the characteristics of the dynamic true triaxial electromagnetic Hopkinson bar test system, semi-sine impact loading is used. Shock waves with the same frequency and equal amplitude are synchronously applied to both ends of the titanium bars on both sides of the rock numerical model, so that the stress is evenly loaded on the rock numerical model. The time-domain signals collected by the strain monitoring elements are subjected to fast Fourier transform to convert the stress wave data into the frequency domain. The frequency component with the largest amplitude in the spectrum is identified and defined as the main frequency (the main vibration component). The distribution of the spectral energy density (square of the amplitude) in different frequency bands is calculated to comprehensively reveal the propagation law, local fluctuation characteristics, and nonlinear attenuation effect of stress waves during the impact loading process.

[0098] In step S2, the specific processing method of the dynamic response index calculation step is as follows:

[0099] B1: Identify the captured strain signals and separate the incident wave and the reflected wave in the original waveform.

[0100] Independently use the programmed Fish program to extract the data of the strain monitoring points in real time and output them as time-domain strain signals. Record the strain signals of the left and right titanium bars respectively and store them in the.txt file format for subsequent signal analysis and waveform processing.

[0101] Independently write a Python program to read multiple strain signal files, segment and adaptively identify the features of the signals. Based on the mutation point detection algorithm and peak analysis method, combined with the signal segmentation strategy optimized by machine learning, accurately capture the starting points and peak points of the incident wave and the reflected wave. At the same time, introduce the adaptive threshold algorithm to enable the program to dynamically adjust the detection parameters according to different impact intensities and signal noise levels, ensure the accuracy, robustness, and intelligence of signal extraction, improve the automation level of data processing, avoid the threshold misjudgment problem that may occur in traditional methods, and thus ensure the high-quality extraction of the incident wave and reflected wave signals, providing accurate data for subsequent stress-strain calculations. The incident wave and reflected wave in the extracted original waveform are shown in Fig. 5(a).

[0102] Further refine the signal classification. Taking two-way loading as an example, use Python programming to extract the incident wave and reflected wave data of the left and right titanium bars respectively. The output left incident wave, left reflected wave, right incident wave, and right reflected wave are shown in Fig. 5(b). Among them, the waveforms of the left incident wave and the right incident wave completely overlap, so only the green curve of the right incident wave can be seen in Fig. 5(b). And output in the.txt file format, and the file names are as follows: Output the incident wave and reflected wave data of the left and right sides respectively, and output files of the types left incident wave.txt, left reflected wave.txt, right incident wave.txt, and right reflected wave.txt.

[0103] B2: Calculate the incident stress at both ends of the rock numerical model and , and detect the stress balance at both ends of the specimen through the stress balance coefficient ;

[0104] B3: Calculate the strain rate , dynamic strain and dynamic stress .

[0105] The calculation formulas for step B2 and step B3 are as follows:

[0106]

[0107] where , respectively represent the cross-sectional areas of the titanium rod and the rock numerical model, represents the elastic modulus of the titanium rod, and respectively represent the left incident wave and the left reflected wave, and respectively represent the right incident wave and the right reflected wave, and respectively represent the incident wave velocity and the length of the rock numerical model.

[0108] In the calculation steps of the dynamic response index, it also includes step B4: Visualize the calculated dynamic response index and draw key curves. The key curves include the strain rate-time curve, stress-time curve, strain-time curve, and stress-strain curve, as shown in Fig. 5(c), so as to intuitively display the dynamic evolution law of the rock numerical model under the impact load, accurately depict the change trend of the strain rate, stress response characteristics, cumulative deformation process, and dynamic mechanical properties of the material.

[0109] As Figure 6 shown, in this example, the multi-parameter intelligent analysis step realizes the intelligent analysis of crack evolution, rock damage, and energy characteristics, and has the functions of real-time visualization, automatic recognition, and accurate calculation. It dynamically displays the spatial distribution of different types of cracks, intelligently tracks and counts the number of cracks, and quantitatively evaluates the degree of rock damage. It accurately reproduces the distribution of the maximum principal stress at the moment of failure, locates the region of the maximum contact force at the grain level, and monitors the evolution law of the strain energy density in real time.

[0110] The multi-parameter intelligent analysis step includes the following sub-steps:

[0111] C1: Define the failure criteria for different contacts, group and display the damaged contacts. The contacts include the boundary contacts of mineral crystals and the internal contacts of mineral crystals.

[0112] (1)Definition and determination of crack failure criterion

[0113] Independently program the Fish program to establish a mesoscopic failure criterion for different types of contact interfaces. Taking quartz minerals as an example, when the shear stress on the contact exceeds the shear strength, it is recorded as shear failure, and when the normal stress on the contact is zero, it is recorded as tensile failure. The generation and evolution of cracks are dynamically determined in each calculation step to ensure the accuracy and real-time of crack identification.

[0114] (2)Cross-scale crack identification and determination of intelligent main control factors

[0115] Independently program the Fish program to achieve cross-scale geometric identification and intelligent classification of cracks. For the contacts determined to be damaged, use the c_length command to record the length of the damaged contacts, use the c_ndis and c_sdis commands to obtain the normal and shear displacements respectively, and calculate the failure dip angle. At the same time, the contacts damaged inside the crystal are recorded as transgranular cracks, and the rest are intergranular cracks. Combining with the spatial coordinate mapping technology, project the crack information onto the global coordinate system to generate a visual crack distribution map. Adopt the K-Means clustering method to conduct clustering analysis on multi-factor characteristics such as crack length, dip angle, and transgranular ratio to achieve intelligent identification of the main control failure mechanism.

[0116] C2: Track and count the number of various cracks and calculate the damage degree.

[0117] (1)Independently program the Fish program to automatically track the cracks generated during the entire impact process in a full cycle, record the generation, propagation, and aggregation of cracks in real time, and dynamically count the total number of cracks to provide key data support for rock damage assessment.

[0118] (2)Calculation of rock damage degree and identification of critical moments of damage. Specifically, independently write the Fish program to calculate the damage degree D based on the rock failure mechanism, and accurately locate the critical moment when the rock damage degree increases fastest by analyzing the damage rate to reveal the dynamic failure stress field of the rock.

[0119] The calculation formula for the damage degree D is as follows:

[0120]

[0121] Among them, D represents the damage degree of the rock numerical model during the impact process, c1 and c2 respectively represent the intergranular failure of mineral crystals and the transgranular failure of mineral crystals, f represents the total number of contacts inside the rock sample, represents the proportion of intergranular failure of mineral crystals, represents the proportion of transgranular failure of mineral crystals.

[0122] Preferably, the multi-parameter intelligent analysis step further includes the following sub-steps:

[0123] C3: Calculate the damage degree D based on the rock failure mechanism, and by analyzing the damage rate, locate the critical moment when the damage degree increases fastest, so as to reveal the dynamic failure stress field of the rock, save the calculation model at the moment when the rising rate of the damage degree is the largest, and call the built-in command of the discrete element UDEC program to generate the maximum principal stress field contour map, visually showing the stress distribution state and the main control area of failure inside the rock numerical model.

[0124] C4: Real-time calculation of strain energy density and analysis of evolution law.

[0125] Through the self-written Fish program, record the stress in all directions of all mineral crystals in real time, and calculate the strain energy density based on the stress data , gradually calculate the storage state of the strain energy in the numerical model block at each moment, capture the energy accumulation, dissipation and release laws of the rock at different moments under the impact load by drawing the strain energy contour map, and provide an energy perspective for the study of the rock dynamic failure mechanism.

[0126] Strain energy density The calculation formula is:

[0127]

[0128] In the formula, represents the bulk modulus of the numerical model block, represents the Poisson's ratio of the numerical model block, , , respectively represent the stresses in the XX, YY, and ZZ directions.

[0129] C5: Precise positioning of grain-level contact forces and intelligent stress analysis,

[0130] Traverse all mineral crystals in the calculation process, record the spatial coordinates of each contact point, the type or number of the connected crystal, and the maximum contact force in real time, map the contact force peak and contact position information to a two-dimensional coordinate system, construct a spatial distribution map of contact forces, set a contact force threshold, and automatically identify and screen potential fracture points, providing data support for in-depth exploration of the grain-level failure mechanism and micro-mechanical response.

[0131] Through the multi-parameter intelligent analysis module of the present invention, the dynamic stress-strain curve of the numerical model simulation result is analyzed. The comparison between the numerical model simulation result and the indoor experimental data is as Figure 7 shown, and the change trend can be divided into 3 stages:

[0132] Elastic stage: The curve is approximately a straight line. The specimen is in the elastic stage and cracks begin to initiate. Plastic stage: As the strain increases, the growth trend of the stress curve slows down and gradually reaches a peak. Failure stage: As the strain increases, the stress shows an obvious decline, and the curve has obvious ductility characteristics. The dynamic response indexes obtained by numerical methods are all within 5% of the indoor test results, as shown in Table 1.

[0133] Table 1 Comparison of calculation results of numerical model and indoor test results

[0134] Characteristic index Laboratory test Numerical model Error / % Peak strain 0.01802 0.017650 2.05 Peak stress / MPa 46.10951 46.77 1.43 Strain rate / % 85.3 78.7 3.16

[0135] Figure 8 It is a schematic diagram for crack tracking statistics and real-time crack display, indicating that the failure in the dynamic impact test is mainly tensile cracks parallel to the loading direction. A large amount of cracks are generated in the quartz mineral with a large mineral content during the test, which is consistent with the test results. Further analysis and comparison of the numerical simulation and indoor test results are as Figure 9 shown. Under the impact load, the overall red damage of sandstone develops uniformly, and the mesoscopic damage is mainly the development of cracks inside the crystal. The numerical simulation and analysis conclusions are consistent with the indoor test results, both demonstrating the effectiveness of this analysis method.

[0136] In summary, the embodiment of the present invention combines with an embodiment and conducts verification, demonstrating the applicability of this method in the monitoring and analysis of the auxiliary dynamic true triaxial electromagnetic Hopkinson bar test system, efficiently processing and analyzing the mesoscopic mechanical behavior of rocks under high-speed dynamic loading, and achieving the effect of accurately reproducing the initiation, propagation, and penetration processes of microcracks. The present invention proposes a multi - numerical analysis method applicable to the dynamic true triaxial electromagnetic Hopkinson bar test system, which can quickly simulate and analyze the fracture behavior of rocks under multi - axial dynamic loading, accurately and visually obtain multi - parameter information during the micro - fracture evolution process of rocks, and then systematically reveal the dynamic fracture mechanism of rocks under dynamic disturbance. The present invention will contribute to guiding the scientific design of deep engineering and providing technical support for its safe construction and healthy operation and maintenance.

[0137] Compared with the prior art, the present invention can accurately restore the characteristics of synchronous and symmetrically loaded stress waves in the electromagnetic Hopkinson bar dynamic test system, and assist in the monitoring and analysis of the dynamic true triaxial electromagnetic Hopkinson bar test system. It can truly reflect the fabric characteristics of rocks and the heterogeneity of mineral crystals and grain boundaries, accurately simulate the dynamic mechanical behavior of rocks under impact loads, more intuitively display the real-time fracture information inside rocks, and thus more accurately evaluate the overall damage degree of rocks. By real-time monitoring of multiple information such as crack evolution, maximum principal stress field, strain energy density field, and grain-level contact force, deeply integrating numerical simulation and physical experiments, realizing synchronous monitoring and data analysis of multi-scale and multi-parameters, improving the monitoring and analysis information of the dynamic true triaxial electromagnetic Hopkinson bar test system, and providing strong technical support for rock dynamics research, disaster prediction, and engineering safety protection.

[0138] The specific embodiments described above are the preferred embodiments of the present invention, which do not limit the specific implementation scope of the present invention. The scope of the present invention includes but is not limited to this specific embodiment. All equivalent changes made in accordance with the present invention are within the protection scope of the present invention.

Claims

1. A multivariate numerical analysis method based on a TEHB test system, characterized in that The steps are as follows: Steps for numerical simulation of multi-directional synchronous impact test: Establish a rock numerical model with real mineral texture and breakable mineral crystals, and construct a dynamic true triaxial electromagnetic Hopkinson bar (TEHB) test system including a simulation framework for uniaxial two-way synchronous impact test to conduct numerical simulation of multi-directional synchronous impact test on the rock numerical model; Steps for calculating dynamic response indicators: Separate and recombine the incident wave signal and reflected wave signal obtained by monitoring, and obtain the dynamic response indicators of the rock numerical model during the impact process. The dynamic response indicators include dynamic equilibrium coefficient, strain rate, strain and stress; Steps for intelligent analysis of multiple parameters: During the numerical simulation of multi-directional synchronous impact test, the spatial distribution characteristics of different types of cracks are displayed in real time to realize the intelligent analysis of crack evolution, rock damage and energy characteristics. The steps for intelligent analysis of multiple parameters include the following sub-steps: C1: Define the failure criteria for different contacts, group and display the damaged contacts. The contacts include the boundary contacts of mineral crystals and the internal contacts of mineral crystals; C2: Track and count the number of various cracks and calculate the damage degree. The calculation formula is as follows: Among them, D represents the damage degree of the numerical model of rock during the impact process, c1 and c2 respectively represent the intergranular failure of mineral crystals and the transgranular failure of mineral crystals, and f represents the total number of contacts inside the rock sample. represents the proportion of intergranular failure of mineral crystals. represents the proportion of transgranular failure of mineral crystals. The method for establishing the rock numerical model is as follows: A1: Use the discrete element UDEC program to generate a standard rock specimen with a set size, and use a spatial segmentation algorithm to divide the inside of the rock specimen into blocks to form a series of numerical model blocks, and each numerical model block corresponds to a mineral crystal; A2: Output and record a.txt type file containing the number, central coordinates of each numerical model block and the number of each contact; A3: Screen the numerical model blocks based on the proportion of real mineral content, and then use the range command of the discrete element UDEC program to assign mechanical parameters to the screened numerical model blocks according to different mineral characteristics; A4: Connect the center of the numerical model block and each vertex of the numerical model block, further divide the numerical model block, and construct the mesoscopic fracture mechanism inside the rock numerical model to simulate the real rock fragmentation behavior; A5: Identify the boundary contacts of mineral crystals and the internal contacts of mineral crystals, and according to different contact types, assign mechanical parameters to each contact respectively based on experimental data and mineral mechanical characteristics to obtain the final rock numerical model.

2. The multivariate numerical analysis method based on the TEHB test system according to claim 1, wherein The simulation framework for uniaxial two-way synchronous impact test includes titanium rods arranged on the left and right sides of the rock numerical model with a cross-section matching the contact surface of the rock numerical model. The end faces of the titanium rods that do not contact the rock numerical model on the left and right sides are provided with first viscous boundaries, and the upper and lower sides of the titanium rods are provided with second viscous boundaries. A strain monitoring element is arranged in the middle of the titanium rod to capture the propagation characteristics of stress waves under the action of impact load.

3. The multivariate numerical analysis method based on the TEHB test system according to claim 2, wherein The method for numerical simulation of multi-directional synchronous impact test is: Based on the characteristics of the dynamic true triaxial electromagnetic Hopkinson bar test system, apply semi-sine impact loading, and synchronously apply shock waves with the same frequency and equal amplitude at both ends of the titanium rods on both sides of the rock numerical model to uniformly load the stress on the rock numerical model. Perform a fast Fourier transform on the time-domain signal collected by the strain monitoring element, convert the stress wave data to the frequency domain, identify the frequency component with the largest amplitude in the spectrum, define it as the main frequency, and calculate the distribution of the spectral energy density in different frequency bands to comprehensively reveal the propagation law, local fluctuation characteristics, and nonlinear attenuation effect of stress waves during the impact loading process.

4. The multivariate numerical analysis method based on the TEHB test system according to claim 3, wherein In the calculation steps of the dynamic response index, the calculation method of the dynamic response index is as follows: B1: Identify the captured strain signal and separate the incident wave and reflected wave in the original waveform; B2: Calculate the incident stress at both ends of the rock numerical model and , and detect the stress balance at both ends of the specimen through the stress balance coefficient ; B3: Calculate the strain rate , dynamic strain and dynamic stress , The calculation formula is as follows: Among them, and represent the cross-sectional areas of the titanium rod and the rock numerical model respectively, represents the elastic modulus of the titanium rod, and represent the left incident wave and the left reflected wave respectively, and represent the right incident wave and the right reflected wave respectively, and represent the incident wave velocity and the length of the rock numerical model respectively.

5. The multivariate numerical analysis method based on the TEHB test system according to claim 4, characterized in that, In the calculation steps of the dynamic response index, it also includes step B4: Perform visualization processing on the calculated dynamic response index and draw key curves. The key curves include the strain rate-time curve, stress-time curve, strain-time curve, and stress-strain curve to intuitively display the dynamic evolution law of the rock numerical model under the action of impact load.

6. The multivariate numerical analysis method based on the TEHB test system according to any one of claims 1-5, characterized in that, In sub-step C1, through an independently programmed Fish program, realize the cross-scale geometric identification and intelligent classification of cracks. For the contacts determined to be damaged, use the c_length command to record the length of the damaged contacts, obtain the normal and shear displacements through the c_ndis and c_sdis commands respectively, and calculate the damage inclination angle. At the same time, record the contacts that are damaged inside the crystal as transgranular cracks, and the rest as intergranular cracks. Combine the space coordinate mapping technology to project the crack information onto the global coordinate system to generate a visualized crack distribution map.

7. The multivariate numerical analysis method based on the TEHB test system according to claim 6, characterized in that In sub-step C2, automatically track the cracks generated during the entire impact process in real time, record the generation, propagation, and aggregation of cracks in real time, and dynamically count the total number of cracks to provide key data support for rock damage assessment. The multi-parameter intelligent analysis step also includes sub-step C3: Calculate the damage degree D based on the rock failure mechanism, and locate the critical moment when the damage degree increases the fastest by analyzing the damage rate to reveal the rock dynamic failure stress field. Save the calculation model at the moment when the damage degree rising rate is the largest, and call the built-in command of the discrete element UDEC program to generate the maximum principal stress field contour map to intuitively display the stress distribution state and the main control area of failure inside the rock numerical model.

8. The multivariate numerical analysis method based on the TEHB test system according to claim 7, characterized in that, The multi-parameter intelligent analysis step also includes the following sub-steps: C4: Real-time calculation and evolution law analysis of strain energy density, Record the stress in all directions of all mineral crystals in real time, and calculate the strain energy density based on the stress data , gradually calculate the storage state of the strain energy in the numerical model block at each moment, capture the laws of energy accumulation, dissipation and release of rocks at different moments under impact loads by drawing strain energy contour maps, and provide an energy perspective for the study of rock dynamic failure mechanisms Strain energy density The calculation formula is as follows: In the formula, represents the bulk modulus of the numerical model block, represents the Poisson's ratio of the numerical model block, , , represent the stresses in the XX, YY, and ZZ directions respectively, C5: Precise positioning and intelligent stress analysis of grain-level contact forces, Traverse all mineral crystals in the calculation process, record the spatial coordinates of each contact point, the type or number of the connected crystals, and the maximum contact force in real time. Map the contact force peak value and contact position information to a two-dimensional coordinate system to construct a contact force spatial distribution map, set a contact force threshold, and automatically identify and screen potential fracture points to provide data support for in-depth exploration of the grain-level failure mechanism and micro-mechanical response.

9. A multivariate numerical analysis system for implementing the multivariate numerical analysis method based on the TEHB test system according to any one of claims 1-8, characterized in that, including: Multi-directional synchronous impact test numerical simulation module: Used to establish a rock numerical model with real mineral fabric and breakable mineral crystals, and construct a dynamic true triaxial electromagnetic Hopkinson bar test system including a single-axis two-way synchronous impact test simulation framework for performing multi-directional synchronous impact test numerical simulation on the rock numerical model; Dynamic response index calculation module: It is used to separate and recombine the incident wave signal and the reflected wave signal obtained by monitoring, and obtain the dynamic response indexes of the rock numerical model during the impact process. The dynamic response indexes include the dynamic balance coefficient, strain rate, strain, and stress; Multi-parameter intelligent analysis module: It is used to display the spatial distribution characteristics of different types of cracks in real time during the numerical simulation of the multi-directional synchronous impact test, and realize the intelligent analysis of crack evolution, rock damage, and energy characteristics. The execution method of the multi-parameter intelligent analysis module includes the following sub-steps: C1: Define the failure criteria for different contacts, group and display the contacts that have failed. The contacts include the boundary contacts of mineral crystals and the internal contacts of mineral crystals; C2: Track and count the number of various cracks and calculate the damage degree. The calculation formula is as follows: Among them, D represents the damage degree of the rock numerical model during the impact process, c1 and c2 respectively represent the intergranular failure of mineral crystals and the transgranular failure of mineral crystals, and f represents the total number of contacts inside the rock sample. represents the proportion of intergranular failure of mineral crystals. represents the proportion of transgranular failure of mineral crystals.

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