CN-122016663-A - Preparation method of coarse and fine particle-clamped hybrid photoelastic sample and contact force chain network analysis method

CN122016663ACN 122016663 ACN122016663 ACN 122016663ACN-122016663-A

Abstract

The invention discloses a method for preparing a coarse and fine particle-clamped photoelastic sample and analyzing a contact force chain network, which relates to the field of particle material mechanics tests and comprises the steps of calculating target void ratios under different coarse particle contents by a discrete element method; generating a corresponding numerical calculation sample according to the target pore ratio and the preset coarse grain content, deriving related parameters to prepare coarse and fine grain-sandwiched photoelastic samples with the same initial compactness, combining unpolarized and polarized photoelastic images of the photoelastic samples, extracting inter-grain contact force and constructing a contact force network, extracting a strong contact force network based on the contact force network, and performing mesoscopic analysis to obtain force transmission characteristic comparison results under different coarse grain content conditions. The method realizes the preparation efficiency and the controllability of the initial state of samples with different coarse grain contents, reveals the influence rule of the coarse grain contents on the force chain structure and the force transmission characteristics thereof based on the analysis of a contact force chain network, and has important significance for researching the force transmission mechanism of a coarse grain and fine grain inclusion system and the fine structural characteristics thereof.

Inventors

SHI XIUSONG
XU JIN
ZHAO JIDONG
LI AIGUO
LIU KAI
XIONG HAO

Assignees

深圳大学

Dates

Publication Date: 20260512
Application Date: 20260413

Claims (9)

1. The preparation method of the coarse and fine particle-clamped hybrid photoelastic sample and the contact force chain network analysis method are characterized by comprising the following steps of: s1, calculating target pore ratios under different coarse grain contents by a discrete element method; S2, generating a corresponding numerical calculation sample according to the target pore ratio and the preset coarse grain content, and leading out related parameters to prepare coarse and fine grain-clamped photoelastic samples with the same initial compactness; S3, combining the unpolarized photoelastic image and the polarized photoelastic image of the photoelastic sample, extracting inter-particle contact force and constructing a contact force network; And S4, extracting a strong contact force network based on the contact force network, and performing mesoscopic analysis to obtain a force transmission characteristic comparison result under the condition of different coarse grain contents.
2. The method for preparing a coarse and fine particle-clamped hybrid photoelastic sample and analyzing a contact force chain network according to claim 1, wherein the step S1 comprises: obtaining the maximum pore ratio corresponding to the most loosely piled state of the particle system under different coarse particle contents through discrete element numerical simulation Minimum void ratio corresponding to the most densely packed state ; According to preset relative compactness Calculating a target void ratio 。
3. The method for preparing a coarse and fine particle-clamped hybrid photoelastic sample and analyzing a contact force chain network according to claim 1, wherein the step S2 comprises: Generating a corresponding numerical calculation sample based on the target pore ratio and the preset coarse grain content, and preparing a two-dimensional photoelastic sample according to the number of coarse grains and fine grains in the sample; The method comprises the steps of constructing samples with different coarse grain contents through a sample delivering strategy, namely preparing a photoelastic sample with high coarse grain content, taking the photoelastic sample with high coarse grain content as an initial structure, and obtaining a target coarse grain content sample by gradually removing part of coarse grains from the initial structure, disturbing the rest coarse grains and supplementing corresponding quantity of fine grains when preparing the photoelastic sample with low coarse grain content.
4. The method for preparing a coarse and fine particle-clamped hybrid photoelastic sample and analyzing a contact force chain network according to claim 1, wherein the step S3 comprises: s31, recognizing particle contours in the unpolarized image, and acquiring center coordinates and radiuses of each particle; S32, identifying particle pairs in contact with each other according to a preset contact judgment criterion, and establishing a particle contact relationship; S33, extracting corresponding inter-particle contact force based on the polarized photoelastic image; and S34, regarding particles as network nodes, regarding inter-particle contact as network edges, and constructing a contact force network by taking the extracted contact force as edge weight.
5. The method for preparing a coarse and fine particle-doped photoelastic sample and analyzing a contact force chain network according to claim 4, wherein in S32, a contact judgment criterion is preset for any particle And particles If the center distance between two particles is satisfied Will then Is denoted as contact pair, in which And Respectively particles And Is used for the radius of the (c) for the (c), An error compensation amount is identified for the image.
6. The method for preparing a coarse and fine particle-doped photoelastic sample and analyzing a contact force chain network according to claim 4, wherein the step S33 comprises: Graying the polarized photoelastic image, calculating gradient amplitude of pixels in single particles, and defining photoelastic response of the particles An integrated average value that is the square of its internal gradient; building particle photoelastic response by combining single particle calibration test Empirical relationship with average contact force F Calculating the average contact force to which each particle is subjected Wherein a, b are fitting parameters; based on the relative magnitude of the photoelastic response intensity at each contact interface, the average contact force experienced by each particle is determined Distributing to corresponding particle contact positions to obtain initial estimated values of contact force of each contact point I, j represent particle numbers; constructing a particle contact force inversion model, generating a corresponding photoelastic response image through theoretical contact force distribution, comparing the photoelastic response image with a polarized photoelastic image obtained through experiments, and establishing a residual function between an observation image and a theoretical image; optimizing and solving the contact force parameters by adopting a nonlinear least square algorithm, minimizing a residual function, and obtaining a contact force distribution result which is most matched with the experimental photoelastic image and meets the particle stress balance condition 。
7. The method for preparing a coarse and fine particle-doped photoelastic sample and analyzing a contact force chain network according to claim 1, wherein in S4, the mesoscopic analysis comprises a topological structure analysis, and the method comprises the following steps: identifying the maximum connected cluster in the strong contact force network, and counting the proportion of the number of nodes of the maximum connected cluster to the total number of nodes of the strong contact force network to obtain the relative size of the maximum connected cluster; Based on the direction of the particle contact connecting line in the strong contact force network, the contact quantity in each direction interval is counted, and the distribution characteristics of the contact direction are obtained.
8. The method for preparing a coarse and fine particle-doped photoelastic sample and analyzing a contact force chain network according to claim 1, wherein in S4, the mesoscopic analysis further comprises percolation characteristics analysis, comprising: Stepwise adjustment of contact force threshold Constructing a strong contact sub-network under different threshold conditions, wherein Is a dimensionless parameter and is used for screening that the contact force is larger than Contact relation of multiple average contact force; The relative sizes of the maximum connected clusters under the thresholds are counted, and the critical threshold for converting the strong contact force network from the non-through state to the through state is determined and used as the percolation threshold of the force chain And the penetration state is that the particle collection in the maximum communicating cluster is simultaneously contacted with the boundaries of the two sides of the sample.
9. The method for preparing a coarse and fine particle-doped photoelastic sample and analyzing a contact force chain network according to claim 1, wherein in S4, the mesoscopic analysis further comprises a matrix bridge structure analysis, and the method comprises the following steps: Identifying a fine particle set which is positioned between adjacent coarse particles, is composed of a plurality of fine particles and has a contact relationship belonging to strong contact, and defining a matrix bridge structure; And counting the number, the spatial distribution or the communication scale of the matrix bridge structures.

Description

Preparation method of coarse and fine particle-clamped hybrid photoelastic sample and contact force chain network analysis method Technical Field The invention relates to the field of particle material mechanics tests, in particular to a method for preparing a coarse and fine particle-clamped hybrid photoelastic sample and analyzing a contact force chain network. Background The particle material is widely used in various engineering fields such as geotechnical engineering, geological disaster prevention and control, powder metallurgy and the like, the evolution characteristics of an internal force chain network directly determine the mechanical response behavior of the whole material, and a photoelastic experiment is used as a non-contact measuring method capable of visually displaying the contact force distribution among particles, and is widely applied to the microscopic mechanical research of a two-dimensional particle system, so that the related experimental research is carried out for simulating the common grading characteristics in the actual engineering material by adopting a coarse and fine mixed photoelastic sample formed by mixing coarse particles and fine particles. However, in the preparation process of the existing coarse and fine mixed photoelastic samples, the initial compaction state of the samples with different coarse grain contents is difficult to effectively control, as the change of coarse grain contents can obviously influence the stacking property of a particle system, when the samples with different coarse grain contents are prepared by adopting a conventional sample laying or layering sample loading mode, each sample often has different initial void ratios and relative compactedness, the difference of the initial states can directly interfere the formation of contact relation among particles, further influence the distribution characteristics of a force chain network, so that the influence of the change of coarse grain contents on the force transmission property is difficult to truly reflect by test results, and the comparability and repeatability of the test results among different samples are reduced. On the other hand, the existing photoelastic sample preparation method generally has the problems of complicated operation and lower efficiency, and generally needs to perform multiple independent sample spreading or loading operations respectively according to test requirements of different coarse particle contents, and each sample preparation needs to repeat the steps of particle screening, spreading, leveling and the like, so that a great deal of time is consumed, the consistency of particle arrangement modes of different samples in the preparation process is difficult to ensure, and the low-efficiency sample preparation mode limits the development of multiple groups of comparison tests of different coarse particle contents, and restricts the deep research of the mechanical behaviors of coarse and fine inclusion particle systems. In addition, the existing contact force analysis method aiming at the photoelastic image is concentrated on a single-grain-diameter or approximately-homogeneous grain system, the attention of a special fine structure in a coarse-fine inclusion grain system is insufficient, the conventional method is mainly based on the photoelastic image to extract inter-grain contact force and construct a contact force network, but the system analysis of a strong contact force network topological structure is lacking, connectivity, directionality and penetration critical conditions of force chains under different coarse grain contents are difficult to quantify, and particularly for a bearing and force transmission structure formed by fine grains between adjacent coarse grains, no effective identification and quantification method is established in the prior art, so that the knowledge of the mechanical contribution of fine grains in the coarse-fine inclusion grain system is insufficient. Therefore, how to design a method for preparing coarse and fine particle-clamped photoelastic samples and analyzing contact force chain networks, which can effectively control the consistency of initial states of different samples, improve the sample preparation efficiency, and perform systematic quantitative analysis on particle contact force networks so as to realize reliable comparison and research on force transmission characteristics under the condition of different coarse particle contents is a problem to be solved by those skilled in the art. Disclosure of Invention In view of the above, the invention provides a method for preparing coarse and fine particle-clamped photoelastic samples and analyzing a contact force chain network, which aims to solve the problems that in the prior art, the initial compaction state of samples with different coarse particle contents is difficult to be kept consistent, the sample preparation efficiency is low, and the system quantitative analysis on th