Wear prediction method of shield machine disc cutter based on abrasive contact mechanics

Abstract

The present invention proposes a method for predicting the wear of a disc cutter of a shield machine based on abrasive contact mechanics. According to the structural feature that the disc cutter of a shield machine is formed by the accumulation and cementation of a series of metal abrasives with specific mechanical properties, a structural physical model of the disc cutter of a shield machine is proposed. Taking into account the process of the cutter excavating and breaking rocks in the rock mass and its interaction with the rock mass, a "cutter-rock mass collaborative analysis wear prediction model" is constructed. The cutter wear and crack propagation are predicted through the model to realize the prediction of the wear state, internal crack propagation and blade collapse of the disc cutter of the shield machine, so as to realize the optimization of disc cutter manufacturing materials, cutter selection, cutter replacement guidance and other links. The method has high practical application and promotion value.

Description

Technical Field

[0001] The invention belongs to the technical field of disc cutter wear prediction, and in particular relates to a method for predicting disc cutter wear of a shield machine based on abrasive contact mechanics. Background Art

[0002] Full-section tunnel boring machines (TBMs) are characterized by high excavation speed, safety and high efficiency, and are widely used in the construction of urban underground spaces. Disc cutters are an important component of the cutterhead for cutting rock mass on full-section tunnel boring machines, and they directly cut and crush the rock mass during the excavation process. However, the service environment of disc cutters is extremely complex and changeable, resulting in a variety of external manifestations of disc cutter wear. In actual engineering, it is difficult to accurately judge the actual contact between the cutter and the rock. Not only that, the wear and tear of the disc cutters and the cutter replacement process will further affect the construction benefits and economic costs of the entire project, thereby restricting the overall construction progress and quality. Therefore, the wear problem of the shield machine disc cutter has always been the most common and unavoidable difficult problem in the construction of full-section tunnel boring machines.

[0003] For example, the invention patent with the authorization announcement number [CN 104182620 B] discloses a method for predicting the wear of disc cutters using life coefficients, by calculating the spiral wear coefficient and arc wear coefficient of the disc cutters on the cutterhead of a full-section tunnel boring machine; respectively correcting the spiral wear coefficient and arc wear coefficient of the disc cutters and defining the life coefficient of the disc cutters on the cutterhead of a full-section tunnel boring machine; predicting the wear of the disc cutters on the cutterhead of a full-section tunnel boring machine, and obtaining a disc cutter life coefficient prediction method with high prediction accuracy to predict the wear of the disc cutters. In addition, the invention patent with the application announcement number [CN 106570275 A] discloses a TBM cutter wear prediction method based on CAI values. Based on the cutter wear test, a disc cutter wear prediction model based on the rock CAI system value is established by using regression analysis; on this basis, the cutter wear rate (i.e., wear coefficient) and CAI value are used as core parameters to obtain a cutter life prediction model suitable for actual engineering.

[0004] However, in order to predict the wear of disc cutters, most of the existing methods for predicting the wear of disc cutters are based on wear resistance tests of shield machine disc cutter materials and rocks with different mechanical properties. They cannot accurately reveal the wear behavior of disc cutters under service conditions, and it is even more difficult to accurately analyze and study the microscopic damage mechanism of disc cutters. When studying the microscopic fracture of rocks, Academician Xie Heping found that the microscopic damage morphology of rock fractures exists in the form of intergranular fracture and transgranular fracture. He regarded the internal microstructure of rocks as a combination of grains and constructed a microscopic model of rock damage and studied its mechanism. Based on this idea, the present invention proposes a method for predicting the wear of disc cutters of shield machines based on abrasive contact mechanics, which realizes the model construction and analysis of the microscopic damage mechanism of disc cutters, and solves the problem of difficult judgment of the contact between disc cutters and rocks from the perspective of microscopic stress conditions. Summary of the invention

[0005] In view of the defects of the existing disc cutter wear prediction methods, the present invention proposes a shield machine disc cutter wear prediction method based on abrasive contact mechanics, which can realize the prediction of the wear state, internal crack propagation and blade fracture of the shield machine disc cutter, so as to better guide the optimization of disc cutter manufacturing materials, cutter selection, and cutter replacement.

[0006] The present invention is implemented by adopting the following technical scheme: a method for predicting the wear of a shield machine disc cutter based on abrasive contact mechanics, comprising the following steps:

[0007] Step A: Analyze the physical model of the disc cutter structure and calculate the contact force between the disc cutter grains, specifically including:

[0008] Step A1, the shield machine disc cutter is regarded as a series of metal abrasive particles with specific mechanical properties that are stacked and bonded, and the abrasive particles are assumed to be standard spherical, each standard spherical abrasive particle unit is regarded as an infinite rigid body, the contact between the abrasive particles is regarded as flexible contact, and the contact between the abrasive particles is point contact;

[0009] Step A2: Calculate the contact force between the disc cutter grains:

[0010] Step A21, calculate the normal displacement U between two adjacent abrasive particles a and b n and tangential displacement U s ;

[0011] U n =R (a) +R (b) -d;

[0012] U s =Δ sa +Δ sb ;

[0013] Among them, R(a) , R (b) represents the radius of two adjacent abrasive grains of the shield machine disc cutter, d represents the distance between the centers of the two adjacent abrasive grains, Δ sa , Δ sb are the displacements of abrasive particles a and b in the vertical direction along the line connecting the centers of the two abrasive particles;

[0014] Step A22, calculating the normal contact force and tangential contact force of the abrasive particles;

[0015] The contact force between abrasive particles F and the tangential contact force between abrasive particles F s and the abrasive normal contact force F n The relationship between them is:

[0016] F=F s +F n ;

[0017] F n =k n U n ;

[0018] F s =k s U s ;

[0019] Among them, k n is the normal contact stiffness, k s is the tangential contact stiffness;

[0020] Step B: Combined with the test analysis, the abrasive bond fracture tensile strength is obtained and shear strength

[0021] Step C: Construct a wear prediction model for disc cutter-rock collaborative analysis to predict the wear of disc cutter:

[0022] (1) Combine the data obtained in step A and step B to determine the normal contact force and tangential contact force of each abrasive particle and the tensile strength of the abrasive particle bond fracture and shear strength and judge whether the following formula is true:

[0023] Abrasive normal contact force F n >Abrasive bond fracture tensile strength

[0024] Abrasive tangential contact force F s >Abrasive bond fracture shear strength

[0025] If at least one of the above two comparisons is true, the abrasive particle is defined as a failed abrasive particle;

[0026] (2) The failed abrasive particles are counted. If the number of failed abrasive particles is greater than 10% of the total number of abrasive particles, it is considered that the internal wear of the shield machine disc cutter is serious and the cracks are expanding. Otherwise, it is considered that the wear of the shield machine disc cutter is not serious and the crack expansion is slight.

[0027] Furthermore, in step A22, when calculating the normal contact force and the tangential contact force between the abrasive particles, the force state of the disc cutter gradually changes from zero to one, and the deformation process of the cutter is differentiated to form a number of normal displacement variables ΔU n , tangential displacement variable ΔU s , then:

[0028] ΔF n =k n ΔU n ;

[0029] ΔF s =k s ΔU s ;

[0030] Then, the normal contact force and tangential contact force between all abrasive particles are calculated according to the following iterative cycle relationship:

[0031] F n ←F n +ΔF n

[0032] F s ←F s +ΔF s

[0033] Where, ΔF n is the normal contact force F n Shear force variation, ΔF s is the abrasive tangential contact force F s The shear force variable.

[0034] Furthermore, in step A22, when the normal contact force and the tangential contact force of the abrasive reach or exceed 30% of the bond fracture tensile strength and shear strength, the abrasive is considered to enter a plastic state and generate a new displacement:

[0035]

[0036] Among them, x i (t+Δt / 2) , is the velocity and acceleration at t+Δt / 2, x i (t) is the speed at time t, and Δt is the time interval for monitoring the deformation of the hob.

[0037] Furthermore, in step B, when conducting the test analysis:

[0038] (1) Conduct on-site sampling tests on disc cutters under construction, conduct multiple tensile tests on the sampled disc cutters, and obtain the tensile force required to break the disc cutter ring. The tensile force is divided by the cross-sectional area of ​​the disc cutter ring, and the resulting stress is defined as the abrasive bond fracture tensile strength At the same time, the normal contact stiffness k is determined during the test. n ;

[0039] (2) Similarly, a shear test is performed on the strength specimen to obtain the shear force required to break the disc cutter ring. The shear force is divided by the cross-sectional area of ​​the disc cutter ring, and the resulting stress is defined as the abrasive bond fracture shear strength At the same time, the tangential contact stiffness k is determined during the test. s .

[0040] Compared with the prior art, the advantages and positive effects of the present invention are:

[0041] Based on the structural characteristics that the disc cutter of a shield machine is formed by the accumulation and bonding of a series of metal abrasive particles with specific mechanical properties, this scheme proposes a structural physical model of the disc cutter of a shield machine, which can be used to explore and analyze the microscopic damage mechanism of the disc cutter of a shield machine. In addition, by simplifying the model of the disc cutter of a shield machine and starting from the force of the microscopic abrasive particles of the disc cutter, the dependence on determining the contact between the disc cutter of a shield machine and the rock is reduced, thereby simplifying the analysis model and achieving more accurate predictions, so as to better guide the optimization of disc cutter manufacturing materials, cutter selection, and cutter replacement. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a flow chart of the prediction method according to an embodiment of the present invention;

[0043] Figure 2 Schematic diagram of macro-micro abrasive damage and internal crack propagation of a shield machine cutter according to an embodiment of the present invention;

[0044] Figure 3 is the linear relationship between the hob abrasive particles in the embodiment of the present invention n —F n Schematic diagram of normal contact sliding model;

[0045] Figure 4 is the linear relationship between the hob abrasive particles in the embodiment of the present invention s —F s Schematic diagram of the tangential contact sliding model;

[0046] Figure 5 Schematic diagram of the contact relationship between the abrasive grains of the shield machine cutter according to an embodiment of the present invention;

[0047] Figure 6 Schematic diagram of the tangential displacement between abrasive particles in an embodiment of the present invention. DETAILED DESCRIPTION

[0048] In order to more clearly understand the above-mentioned purpose, features and advantages of the present invention, the present invention is further described below in conjunction with the accompanying drawings and embodiments. In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention can also be implemented in other ways different from those described herein, and therefore, the present invention is not limited to the specific embodiments disclosed below.

[0049] The present invention proposes a method for predicting the wear of a shield machine disc cutter based on abrasive contact mechanics. According to the structural characteristics that the shield machine disc cutter is formed by the accumulation and cementation of a series of metal abrasives with specific mechanical properties, a structural physical model of the shield machine cutter is proposed, and the process of the cutter excavating and breaking rocks in the rock mass and its interaction with the rock mass are considered to predict the cutter wear and crack propagation, so as to realize the prediction of the wear state of the shield machine disc cutter and the internal crack propagation (the blade will collapse when the crack propagates to a certain extent). The process is as follows: Figure 1 As shown, the following steps are included:

[0050] Step A, structural physical model analysis, calculating the contact force between the disc-shaped hob abrasive particles, including the normal contact force of the abrasive particles and the tangential contact force of the abrasive particles;

[0051] Step B, combining test analysis to obtain the abrasive bond fracture tensile strength and shear strength;

[0052] Step C: Compare and analyze the normal contact force and tangential contact force of the abrasive calculated in step A and the bond fracture tensile strength and shear strength of the abrasive calculated in step B to determine the wear state of the disc cutter.

[0053] Specifically, the following specific implementation manner will be described in detail the scheme of the present invention:

[0054] In step A, when performing mechanical analysis of the disc cutter, the shield machine disc cutter is first regarded as a series of metal abrasive particles with specific mechanical properties that are stacked and bonded. When performing calculations, it is divided into i abrasive particles (generally i is 20-60), and the contact force of each abrasive particle is calculated in combination with the finite element analysis principle until all i abrasive particles in the disc cutter reach a static equilibrium state, and the total stress state of i abrasive particles in the disc cutter is obtained. At the same time, considering that if the number of divided disc cutters is too large, the amount of calculation will inevitably increase, so this patent recommends that the size of the calculation sample should be appropriately considered in the actual application of this patent, and the number of disc cutter abrasive particles should be controlled, preferably 40 abrasive particles;

[0055] Assuming that the abrasive particles in the shield machine disc cutter contact each other through springs and generate forces, the force between the abrasive particles is calculated cyclically under the linear elastic rule. When the force in the spring exceeds a certain limit, the connection between the abrasive particles will break. The process of the spring connection breaking between the abrasive particles reflects the wear and tear of the tool and the expansion of cracks at the macro level. The mapping relationship between the microscopic damage between the abrasive particles and the macroscopic tool wear is as follows: Figure 2 As shown, F before destruction r and F f They represent the vertical force and rolling force on the disc cutter during rock breaking, which have been mentioned in the research of Colorado School of Mines. F is the force on the abrasive grains when the disc cutter is transmitted to the abrasive grains. The linear elastic relationship between the spring force on the abrasive grains is as follows: Figure 3 , 4 Specifically, the step A comprises the following steps:

[0056] Step A1: Set up assumptions;

[0057] The shield machine disc cutter abrasive particles are regarded as standard spheres; each standard spherical abrasive particle unit constituting the shield machine disc cutter is regarded as an infinite rigid body; the shield machine cutter will be subjected to the reaction force of rock mass squeezing when cutting rock mass, and the reaction force will cause the relative position movement between the shield machine disc cutter abrasive particles, and this movement may be the separation between the two abrasive particles, or it may be the contact between the two abrasive particles. The contact between the shield machine disc cutter abrasive particles is regarded as flexible contact, that is, there is a certain amount of overlap in the contact, and the size of the overlap is related to the contact force; the contact between the shield machine disc cutter abrasive particles is regarded as point contact, so that even if there is an overlap, it only occurs in a very small range; the purpose of setting the above assumptions is to facilitate analysis and calculation in the process of solving the force cycle between the shield machine disc cutter abrasive particles, and it is consistent with the actual theoretical analysis.

[0058] In addition, when performing mechanical analysis, this embodiment uses the disc cutter axis as the x-axis, the two perpendicular directions as the y-axis and the z-axis respectively, and the coordinate origin is selected at the center of the disc cutter entity.

[0059] Step A2, calculating the contact force between the disc-shaped hob abrasive grains;

[0060] Step A21, calculate the normal displacement U between adjacent abrasive grains of the disc hob n and tangential displacement U s ;

[0061] (1) Figure 5 As shown in FIG. 1 , it is a contact relationship diagram between abrasive particles. Abrasive particles a and b are used as examples for explanation (a and b are any two adjacent abrasive particles in the disc cutter of the shield machine, without special requirements). The contact plane direction n between the abrasive particles is determined by calculating the unit normal vector.

[0062]

[0063] where x (a) 、x (b) is the movement displacement of two adjacent shield cutter grains under the action of force; d is the distance between the sphere centers of two adjacent grains, and a and b are the codes of two adjacent grains;

[0064] (2) Calculation of the normal displacement U between the shield machine cutter particles n , still taking abrasive particles a and b as an example, Figure 5 As shown, the normal displacement U n It is caused by the reaction force from the rock mass on the disc cutter of the shield machine when it squeezes the rock mass during the rock breaking process:

[0065] U n =R (a) +R (b) -d

[0066] Among them, R (a) , R (b) It represents the radius of two adjacent standard spherical abrasive grains of the shield machine disc cutter;

[0067] (3) Calculation of the tangential displacement U of the shield machine cutter s ,like Figure 6 As shown, still taking abrasive particles a and b as an example, the tangential displacement U s It is caused by the reaction force from the rock mass on the disc cutter of the shield machine when it squeezes the rock mass during the rock breaking process:

[0068] U s =Δ sa +Δ sb

[0069] Among them, Δ sa , Δ sb They are the displacements of abrasive particles a and b in the direction perpendicular to the line connecting the centers of the two abrasive particles.

[0070] It can be seen that the above normal displacement U n and tangential displacement U s All of these can be obtained by monitoring the abrasive particles of the shield machine disc cutter.

[0071] Step A22, calculating the normal contact force and the tangential contact force of the disc hob;

[0072] The force corresponding to the contact position of the shield machine disc cutter abrasive is divided into the abrasive normal contact force F n and abrasive tangential contact force F s , where the normal contact force F n and the corresponding normal contact displacement U nand normal contact stiffness k n The abrasive tangential contact force F s and the corresponding tangential contact displacement U s and the tangential contact stiffness k s The change of contact force is related to the displacement relationship between contacts;

[0073] (1) Inter-abrasive contact force F and abrasive tangential contact force F s and the abrasive normal contact force F n The relationship between them is:

[0074] F=F s +F n；

[0075] Wherein, the subscript i represents the i-th abrasive particle;

[0076] (2) Abrasive normal contact force F n and normal displacement U n is proportional, that is:

[0077] F n =k n U n

[0078] (3) Abrasive tangential contact force F s and tangential displacement U s is proportional, that is:

[0079] F s =k s U s

[0080] It should be noted that the applicable scope of the above formula is that the contact between the abrasive particles is within the elastic range.

[0081] During the rock-breaking process of the shield machine, the stress state of the disc cutter changes gradually from zero to one, and the deformation of the cutter also increases from zero until it reaches the destruction state. When studying the stress and wear of the disc cutter, the deformation process of the cutter is differentiated to form several ΔU n , ΔU s (its ΔU n , ΔU s The acquisition is carried out by monitoring the disc cutter of the shield machine. Specifically, it can be a strain gauge or fiber Bragg grating (both of which are existing technologies). On the one hand, it is more in line with the physical process of rock breaking and wear and damage by the cutter, and on the other hand, it divides the small deformation to make the calculation result more accurate.

[0082] Abrasive normal contact force F n Shear force variation ΔF n and normal displacement U nThe variable ΔU n The relationship between them is expressed as:

[0083] ΔF n =k n ΔU n

[0084] Abrasive tangential contact force F s Shear force variation ΔF s and tangential displacement U s The variable ΔU s The relationship between them is expressed as:

[0085] ΔF s =k s ΔU s

[0086] The normal contact force and tangential contact force between all abrasive particles can then be calculated using the following assignment relationship:

[0087] F n ←F n +ΔF n

[0088] F s ←F s +ΔF s

[0089] In this embodiment, through the above monitoring and calculation, when the force between the two abrasive particles, whether it is the normal contact force or the tangential contact force, reaches or exceeds 25% of the corresponding bond fracture tensile strength and shear strength value, it is considered that the abrasive particle enters a plastic state, and the law of motion is in accordance with Newton's second law, and there is linear motion and rotational motion under the action of external force;

[0090] When linear motion occurs:

[0091]

[0092] When rotational motion occurs:

[0093]

[0094] Where: I is the moment of inertia; M is the resultant torque;

[0095] Calculate the acceleration and angular acceleration at t

[0096]

[0097]

[0098] in, ω iTo calculate at time t±nΔt / 2, x i , F i and M are calculated at time t±nΔt.

[0099] Calculate the velocity and angular velocity at t±Δt / 2

[0100]

[0101]

[0102] The new displacement calculation formula of the wear particle can be obtained from the previous speed:

[0103]

[0104] By calculating the stress state of the abrasive particles before destruction and the movement trajectory of the abrasive particles after contact destruction between the abrasive particles, a cycle of repeated iterative calculation of the relevant stress state and mechanical properties of the abrasive particles is formed.

[0105] Through the indicator ΔU n , ΔU s As well as Δt's continuous approach to the mechanical state of hob wear damage at the monitoring level, the analysis and calculation of the force between the internal hob grains is realized, and finally the normal contact force between the disc hob grains and the tangential contact force between the disc hob grains are obtained. This method of abstracting actual granular materials into particle units in the mathematical domain and mapping the macroscopic mechanical problems of materials from the physical domain to the mathematical domain for solution and calculation has many applications in the field of numerical simulation. On this basis, the present invention makes creative improvements and designs to realize the mechanical analysis of the contact force of the disc hob grains.

[0106] In step B, the abrasive bonding contact model of the hob material is analyzed experimentally to determine the mechanical properties of the shield machine hob metal material. During the analysis: 1. Mill off about 30 mm at both ends of the cutter ring to remove the heat affected zone; 2. Cut the cutter ring to 10 mm thick as a strength test specimen to ensure that the upper and lower planes of the specimen are parallel;

[0107] (1) Conduct on-site sampling tests on disc cutters under construction, and conduct tensile tests on the selected disc cutters as many times as possible to obtain the tensile force required to break the cutter ring of the disc cutter. The tensile force is divided by the cross-sectional area of ​​the cutter ring, and the obtained stress is defined as the abrasive bond fracture tensile strength. At the same time, the normal contact stiffness k is determined during the test. n ;

[0108] (2) Similarly, a shear test is performed on the strength specimen to obtain the shear force required to break the disc cutter ring. The shear force is divided by the cross-sectional area of ​​the cutter ring, and the resulting stress is defined as the abrasive bond fracture shear strength. At the same time, the tangential contact stiffness is measured during the test.

[0109] Step C, constructing a cutter-rock collaborative analysis wear prediction model to predict the wear of the disc cutter;

[0110] First, determine whether the normal contact force and tangential contact force of each abrasive particle is greater than the abrasive particle bond fracture tensile strength or the abrasive particle bond fracture shear strength, and the abrasive particles that are greater than (any greater than, or) are called failed abrasive particles. Secondly, count the failed abrasive particles. If the number of failed abrasive particles is greater than 10% of the total number, it is considered that the internal wear of the shield machine disc cutter is serious and the cracks are expanding. If the number of failed abrasive particles is less than 10% of the total number, it is considered that the shield machine disc cutter is not seriously worn, and the crack expansion is light and can be ignored.

[0111] In summary, the basic idea of ​​the abrasive contact mechanics prediction method is to regard each abrasive as a unit, and to solve the wear and damage behavior of the entire hob system cyclically based on the interaction between units in each calculation step and the iteration of Newton's second law. When two abrasives come into contact, displacement superposition will occur at the contact point; the force on the unit can be obtained based on the force-displacement law and the constitutive relationship of the material; then the acceleration of the unit is obtained by using Newton's second law, and then the velocity and the new displacement are obtained; subsequently, due to the new displacement of the abrasive, a new superposition is generated at the superposition point, and this cycle is repeated, and mechanical calculations and iterative analysis are continuously performed. The contact force between the abrasives is repeatedly calculated by using Newton's laws of motion, and the velocity, acceleration, and displacement of the abrasives are assigned to the corresponding abrasives in a timely manner. When the abrasives obtain new parameters, they are re-iterated according to the iterative rules until a static equilibrium state is reached, and then the state changes between the abrasives at the micro level reflect the wear state of the disc hob at the macro level.

[0112] The above description is only a preferred embodiment of the present invention and does not limit the present invention in other forms. Any technician familiar with the profession may use the technical content disclosed above to change or modify it into an equivalent embodiment with equivalent changes and apply it to other fields. However, any simple modification, equivalent change and modification made to the above embodiment based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A wear prediction method for shield machine disc cutter based on abrasive contact mechanics, characterized in that: The following steps are involved: Step A: Analyze the physical model of the disc cutter structure and calculate the contact force between the disc cutter grains, specifically including: Step A1, the shield machine disc cutter is regarded as a series of metal abrasive particles with specific mechanical properties that are stacked and bonded, and the abrasive particles are assumed to be standard spherical, each standard spherical abrasive particle unit is regarded as an infinite rigid body, the contact between the abrasive particles is regarded as flexible contact, and the contact between the abrasive particles is point contact; Step A2: Calculate the contact force between the disc cutter grains: Step A21, calculate the normal displacement U between two adjacent abrasive particles a and b n and tangential displacement U s ; U n =R (a) +R (b) -d; U s =D sa +D sb ; Among them, R (a) , R (b) represents the radius of two adjacent abrasive grains of the shield machine disc cutter, d represents the distance between the centers of the two adjacent abrasive grains, Δ sa , Δ sb are the displacements of abrasive particles a and b in the vertical direction along the line connecting the centers of the two abrasive particles; Step A22, calculating the normal contact force and tangential contact force of the abrasive particles; The contact force between abrasive particles F and the tangential contact force between abrasive particles F s and the abrasive normal contact force F n The relationship between them is: F=F s +F n ; F n =k n U n ; F s =k s U s ; Among them, k n is the normal contact stiffness, k s is the tangential contact stiffness; When calculating the normal contact force and tangential contact force between the abrasive particles, the force state of the disc cutter changes gradually from zero to one, and the deformation process of the cutter is differentiated to form several normal displacement variables ΔU n , tangential displacement variable ΔU s , then: ΔF n =k n ΔU n ; ΔF s =k s ΔU s ; Then, the normal contact force and tangential contact force between all abrasive particles are calculated according to the following iterative cycle relationship: F n ←F n +ΔF n F s ←F s +ΔF s Where, ΔF n is the normal contact force F n Shear force variation, ΔF s is the abrasive tangential contact force F s The shear force variable; When the normal contact force and tangential contact force of the abrasive reach or exceed 30% of the bond fracture tensile strength and shear strength, the abrasive is considered to enter a plastic state and generate new displacement: Among them, x i (t+Δt / 2) , is the velocity and acceleration at t+Δt / 2, x i (t) is the speed at time t, Δt is the time interval for monitoring the deformation of the hob; Step B: Combined with the test analysis, the abrasive bond fracture tensile strength is obtained and shear strength Step C, compare and analyze the normal contact force and tangential contact force of the abrasive calculated in step A and the bond fracture tensile strength and shear strength of the abrasive calculated in step B to determine the number of failed abrasives. If the number of failed abrasives is greater than 10% of the total number of abrasives, it is considered that the internal wear of the shield machine disc cutter is serious and the cracks are expanding. Otherwise, it is considered that the wear of the shield machine disc cutter is not serious and the crack expansion is slight.

2. The method for predicting the wear of shield machine disc cutter based on abrasive contact mechanics according to claim 1 is characterized in that: In step B, when conducting the test analysis: (1) Conduct on-site sampling tests on disc cutters under construction, conduct multiple tensile tests on the sampled disc cutters, and obtain the tensile force required to break the disc cutter ring. The tensile force is divided by the cross-sectional area of ​​the disc cutter ring, and the resulting stress is defined as the abrasive bond fracture tensile strength At the same time, the normal contact stiffness k is determined during the test. n ; (2) Similarly, a shear test is performed on the strength specimen to obtain the shear force required to break the disc cutter ring. The shear force is divided by the cross-sectional area of ​​the disc cutter ring, and the resulting stress is defined as the abrasive bond fracture shear strength At the same time, the tangential contact stiffness k is determined during the test. s .

3. The method for predicting the wear of shield machine disc cutter based on abrasive contact mechanics according to claim 1 is characterized in that: In step C, when determining the failed abrasive particles: Abrasive normal contact force F n >Abrasive bond fracture tensile strength Abrasive tangential contact force F s >Abrasive bond fracture shear strength If at least one of the above two comparisons is true, the abrasive particle is defined as a failed abrasive particle.

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