Calculation method and system of dynamic stress intensity factor under steady-state interface crack extension

Abstract

The present invention discloses a method for calculating the dynamic stress intensity factor under steady-state expansion of an interface crack, including obtaining the longitudinal wave velocity and the transverse wave velocity of the first material and the second material on both sides of the interface; calculating the expansion velocity under steady-state expansion of the interface crack; constructing the asymptotic field expression of the crack tip of the first material and the second material on both sides of the interface and calculating the type I and II stress intensity factors; calculating the expression of the interface crack with respect to the type I and II stress intensity factors; substituting the expression of the interface crack with respect to the type I and II stress intensity factors into the calculation formula of the displacement extrapolation method to complete the calculation of the dynamic stress intensity factor under steady-state expansion of the interface crack. The present invention also discloses a system for realizing the method for calculating the dynamic stress intensity factor under steady-state expansion of the interface crack. The present invention has high reliability, good accuracy, good universality, and higher calculation efficiency.

Description

Technical Field

[0001] The invention belongs to the field of civil engineering, and in particular relates to a method and system for calculating a dynamic stress intensity factor under steady-state expansion of an interface crack. Background Art

[0002] At present, with the development of economy and technology, engineering bodies composed of concrete and rock have been widely used in the field of civil engineering, such as lining and surrounding rock of underground buildings, dam body and rock foundation of water conservancy dams, pile body and rock mass of rock-embedded piles of bridges, etc. Therefore, it is particularly important to study the safety of this type of engineering body.

[0003] In this type of engineering structure, the concrete-rock interface is a weak link in the engineering structure. Under the action of external loads, especially external dynamic loads (such as earthquakes, blasting, impact, etc.), the concrete-rock interface is prone to interfacial cracks and continues to expand, which has a great impact on the structural stability and service life of the engineering structure. Therefore, a large number of researchers have studied the expansion law of interfacial cracks and dynamic stress intensity factors.

[0004] At present, there are two main types of commonly used calculation schemes for dynamic stress intensity factors under steady-state expansion of interface cracks: experimental-numerical scheme and theoretical analysis scheme. Among them, the experimental-numerical scheme calculates the dynamic stress intensity factor based on the calibration of test results and numerical simulation; while the theoretical analysis scheme calculates according to the complex function theory for known specimen parameters and external load conditions. However, these two types of schemes take a long time in practical applications, and the general applicability of the schemes is poor. Moreover, such schemes often do not consider the influence of crack growth rate on the dynamic stress intensity factor; therefore, such schemes also have the problem of poor reliability and accuracy. Summary of the invention

[0005] One of the purposes of the present invention is to provide a method for calculating the dynamic stress intensity factor of an interface crack under steady-state propagation with high reliability, good accuracy and good versatility.

[0006] A second object of the present invention is to provide a system for realizing the method for calculating the dynamic stress intensity factor under steady-state expansion of the interface crack.

[0007] The method for calculating the dynamic stress intensity factor under steady-state expansion of the interface crack provided by the present invention comprises the following steps:

[0008] S1. Based on the acoustic emission test or the properties of the material itself, the longitudinal wave velocity and the transverse wave velocity of the first material and the second material on both sides of the interface are calculated;

[0009] S2. Based on the digital image of the interface crack, the expansion velocity of the interface crack under steady-state expansion is calculated through the position change information of the crack tip over a period of time;

[0010] S3. Based on the weight function method, the asymptotic field expressions of the crack tips of the first material and the second material on both sides of the interface are constructed, and the stress intensity factors of mode I and II are calculated;

[0011] S4. Substituting the type I and II stress intensity factors obtained in step S3 into the position values ​​corresponding to different positions on the digital image from the crack tip in step S2, and calculating expressions of the interface crack with respect to the type I and II stress intensity factors;

[0012] S5. Substitute the expressions of the interface crack mode I and II stress intensity factors obtained in step S4 into the calculation formula of the displacement extrapolation method to complete the calculation of the dynamic stress intensity factor under steady-state expansion of the interface crack.

[0013] The step S1 specifically includes the following steps:

[0014] Through the acoustic emission test, the longitudinal wave velocity of the first material and the second material on both sides of the interface is directly measured. and shear wave velocity ; The value of j is 1 or 2, j 1 represents the first material, and j 2 represents the second material;

[0015] If the acoustic emission test cannot be performed, the longitudinal wave velocity of the first material and the second material on both sides of the interface is calculated based on the properties of the material itself using the following formula and shear wave velocity : In the formula is the first Lamé constant of the jth material; is the second Lamé constant of the jth material; is the material density of the jth material;

[0016] The calculation formula is ;

[0017] The calculation formula is In the formula is the Poisson’s ratio of the jth material; is the elastic modulus of the jth material.

[0018] The step S2 specifically includes the following steps:

[0019] Based on the digital image of the interface crack, the coordinates of the crack tip at time t are obtained. and Coordinates of time The expansion velocity V of the interface crack under steady-state expansion is calculated to be ,in is the crack extension time, for The x-axis variation of the crack tip over time, for The y-axis change of the crack tip over time.

[0020] The step S3 specifically includes the following steps:

[0021] Based on the weight function method, the following formula is constructed: In the formula is the stress component of the jth material in the x direction; is the longitudinal wave calculation parameter of the jth material, and ; is the shear wave calculation parameter of the jth material, and ; is the magnitude of the shear wave in the polar coordinate system; is the first indefinite weight function of the jth material; is the magnitude angle of the shear wave in the polar coordinate system; is the second indefinite weight function of the jth material; is the magnitude of the longitudinal wave in the polar coordinate system; The third indefinite weight function is for the jth material; is the magnitude angle of the longitudinal wave in the polar coordinate system; is the fourth indefinite weight function of the jth material; is the stress component of the jth material in the y direction; is the shear stress of the jth material; is the displacement component of the jth material in the x direction; is the displacement component of the jth material in the y direction; is the singularity index, and the expression is in is the first calculation coefficient of the singularity index of the jth material, and ; is the second calculation coefficient of the singularity index of the jth material, and ; is the third calculation coefficient of the singularity index of the jth material, and ; is a positive integer set by yourself;

[0022] The stress intensity factor of mode I crack and mode II crack stress intensity factor The definition of , solving for and , expressed as and ;

[0023] by and As the basis function, through the boundary conditions and continuity conditions, we can calculate In the formula is the first and second order coefficient matrix The first row of elements, The expression is , for The element in the mth row and jth column of is the second order coefficient matrix and , is the third second-order coefficient matrix and ; for The second row element in the is the fourth second-order coefficient matrix The element at row m and column n in The expression is , is the fifth second-order coefficient matrix and , is the sixth second-order coefficient matrix and ; is the seventh second-order coefficient matrix The element at row m and column n in , is the eighth second-order coefficient matrix and , is the ninth second-order coefficient matrix and .

[0024] The step S4 specifically comprises the following steps:

[0025] In step S2, The distance from the crack tip to the corresponding position x , y The displacement value in the direction is substituted into the expressions of the stress intensity factors of mode I and II obtained in step S3, and the expressions of the stress intensity factors of mode I and II for the interface crack are obtained as follows: In the formula is the difference in displacement in the x direction between the upper and lower surfaces at the i-th point; is the x-direction displacement recorded on the upper surface of the crack at the i-th point; is the x-direction displacement recorded on the lower surface of the crack at the i-th point; is the difference in displacement in the y direction between the upper and lower surfaces at the i-th point; is the y-direction displacement recorded on the upper surface of the crack at the i-th point; is the y-direction displacement recorded on the lower surface of the crack at the i-th point; is the distance from the i-th point to the crack tip; is the mode I stress intensity factor at the i-th point on the crack surface at the i-th point; is the mode II stress intensity factor at the i-th point on the crack surface.

[0026] The step S5 specifically includes the following steps:

[0027] Substitute the expressions of the interface crack mode I and II stress intensity factors obtained in step S4 into the calculation formula of the displacement extrapolation method to obtain the calculation formula of the dynamic stress intensity factor under steady-state expansion of the interface crack: In the formula is the mode I dynamic stress intensity factor of the crack surface under steady-state propagation of interface crack; is the mode II dynamic stress intensity factor of the crack surface under steady-state propagation of interface crack; N is the number of points taken by the displacement extrapolation method.

[0028] The present invention also provides a system for realizing the method for calculating the dynamic stress intensity factor under steady-state expansion of the interface crack, comprising a wave parameter calculation module, an expansion speed calculation module, a first factor calculation module, a crack strength calculation module and a dynamic factor calculation module; the wave parameter calculation module, the expansion speed calculation module, the first factor calculation module, the crack strength calculation module and the dynamic factor calculation module are connected in series in sequence; the wave parameter calculation module is used to calculate the longitudinal wave velocity and the transverse wave velocity of the first material and the second material on both sides of the interface based on the acoustic emission test or the properties of the material itself, and upload the data information to the expansion speed calculation module; the expansion speed calculation module is used to calculate the expansion velocity under steady-state expansion of the interface crack based on the received data information, the digital image of the interface crack, and the position change information of the crack tip within a period of time, and upload the data information to the expansion speed calculation module. The first factor calculation module; the first factor calculation module is used to construct the asymptotic field expression of the crack tip of the first material and the second material on both sides of the interface based on the weight function method according to the received data information, and calculate the type I and II stress intensity factors, and upload the data information to the crack strength calculation module; the crack strength calculation module is used to substitute the obtained type I and II stress intensity factors into the position values ​​corresponding to different positions on the digital image at different distances from the crack tip according to the received data information, calculate the expression of the interface crack with respect to the type I and II stress intensity factors, and upload the data information to the dynamic factor calculation module; the dynamic factor calculation module is used to substitute the obtained expression of the interface crack with respect to the type I and II stress intensity factors into the calculation formula of the displacement extrapolation method according to the received data information, and complete the calculation of the dynamic stress intensity factor under the steady-state extension of the interface crack.

[0029] The method and system for calculating the dynamic stress intensity factor under steady-state expansion of an interface crack provided by the present invention calculate and analyze the properties of the materials on both sides of the interface and complete the calculation of the dynamic stress intensity factor under steady-state expansion of the interface crack based on the weight function method; and the method and system have high reliability, good accuracy, good universality, and higher calculation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The figure is a schematic diagram of the method flow of the present invention.

[0031] Figure 2 Schematic diagram of the calculation model of the method of the present invention.

[0032] Figure 3 For the expansion of the embodiment of the method of the present invention Cloud diagram; Figure 3 (a) Steady crack extension The x-direction displacement cloud diagram at the time, Figure 3 (b) Steady crack extension The x-direction displacement cloud diagram at the time.

[0033] Figure 4 For the expansion of the embodiment of the method of the present invention Cloud diagram; Figure 4 (a) Steady crack extension The y-direction displacement cloud diagram at the time, Figure 4 (b) Steady crack extension The y-direction displacement cloud diagram at the moment.

[0034] Figure 5 It is a schematic diagram of the curve of the dynamic stress intensity factor of the method of the present invention and the comparative example method changing with time at 40 MPa.

[0035] Figure 6 It is a schematic diagram of the curve of the dynamic stress intensity factor of the method of the present invention and the comparative example method changing with time at 80 MPa.

[0036] Figure 7 Schematic diagram of the functional modules of the system of the present invention. DETAILED DESCRIPTION

[0037] like Figure 1 The method flow diagram of the method of the present invention is shown as follows: The method for calculating the dynamic stress intensity factor under steady-state expansion of the interface crack disclosed in the present invention comprises the following steps:

[0038] The method for calculating the dynamic stress intensity factor under steady-state expansion of the interface crack of the present invention is aimed at Figure 2 Model shown;

[0039] S1. Based on the acoustic emission test or the properties of the material itself, the longitudinal wave velocity and the transverse wave velocity of the first material and the second material on both sides of the interface are calculated; specifically, the steps include:

[0040] Through the acoustic emission test, the longitudinal wave velocity of the first material and the second material on both sides of the interface is directly measured. and shear wave velocity ; The value of j is 1 or 2, j 1 represents the first material, and j 2 represents the second material;

[0041] If the acoustic emission test cannot be performed, the longitudinal wave velocity of the first material and the second material on both sides of the interface is calculated based on the properties of the material itself using the following formula and shear wave velocity : In the formula is the first Lamé constant of the jth material; is the second Lamé constant of the jth material; is the material density of the jth material;

[0042] The calculation formula is ;

[0043] The calculation formula is In the formula is the Poisson’s ratio of the jth material; is the elastic modulus of the jth material;

[0044] S2. Based on the digital image of the interface crack, the expansion velocity of the interface crack under steady-state expansion is calculated through the position change information of the crack tip over a period of time; specifically, the steps include:

[0045] Based on the digital image of the interface crack, the coordinates of the crack tip at time t are obtained. and Coordinates of time The expansion velocity V of the interface crack under steady-state expansion is calculated to be ,in is the crack extension time, for The x-axis variation of the crack tip over time, for The y-axis change of the crack tip over time;

[0046] S3. Based on the weight function method, the asymptotic field expressions of the crack tips of the first material and the second material on both sides of the interface are constructed, and the stress intensity factors of mode I and mode II are calculated; specifically, the steps are as follows:

[0047] Based on the weight function method, the following formula is constructed: In the formula is the stress component of the jth material in the x direction; is the longitudinal wave calculation parameter of the jth material, and ; is the shear wave calculation parameter of the jth material, and ; is the magnitude of the shear wave in the polar coordinate system; is the first indefinite weight function of the jth material; is the magnitude angle of the shear wave in the polar coordinate system; is the second indefinite weight function of the jth material; is the magnitude of the longitudinal wave in the polar coordinate system; The third indefinite weight function is for the jth material; is the magnitude angle of the longitudinal wave in the polar coordinate system; is the fourth indefinite weight function of the jth material; is the stress component of the jth material in the y direction; is the shear stress of the jth material; is the displacement component of the jth material in the x direction; is the displacement component of the jth material in the y direction; is the singularity index, and the expression is in is the first calculation coefficient of the singularity index of the jth material, and ; is the second calculation coefficient of the singularity index of the jth material, and ; is the third calculation coefficient of the singularity index of the jth material, and ; is a positive integer set by yourself;

[0048] The stress intensity factor of crack surface type I and crack surface mode II stress intensity factor , and we can solve and , expressed as and ;

[0049] by and As the basis function, through the boundary conditions and continuity conditions, we can calculate In the formula is the first and second order coefficient matrix The first row of elements, The expression is , for The element in the mth row and jth column of is the second order coefficient matrix and , is the third second-order coefficient matrix and ; for The second row element in the is the fourth second-order coefficient matrix The element at row m and column n in The expression is , is the fifth second-order coefficient matrix and , is the sixth second-order coefficient matrix and ; is the seventh second-order coefficient matrix The element at row m and column n in , is the eighth second-order coefficient matrix and , is the ninth second-order coefficient matrix and .

[0050] S4. Substituting the type I and II stress intensity factors obtained in step S3 into the position values ​​corresponding to different positions on the digital image from the crack tip in step S2, and calculating the expressions of the interface crack with respect to the type I and II stress intensity factors; specifically comprising the following steps:

[0051] In step S2, The distance from the crack tip to the corresponding position x , y The displacement value in the direction is substituted into the expressions of the stress intensity factors of mode I and II obtained in step S3, and the expressions of the stress intensity factors of mode I and II for the interface crack are obtained as follows:

[0052]

[0053]

[0054] In the formula is the difference in displacement in the x direction between the upper and lower surfaces at the i-th point; is the x-direction displacement recorded on the upper surface of the crack at the i-th point; is the x-direction displacement recorded on the lower surface of the crack at the i-th point; is the difference in displacement in the y direction between the upper and lower surfaces at the i-th point; is the y-direction displacement recorded on the upper surface of the crack at the i-th point; is the y-direction displacement recorded on the lower surface of the crack at the i-th point; is the distance from the i-th point to the crack tip; is the mode I stress intensity factor at the i-th point on the crack surface at the i-th point; is the mode II stress intensity factor at the i-th point on the crack surface;

[0055] S5. Substituting the expressions of the interface crack mode I and II stress intensity factors obtained in step S4 into the calculation formula of the displacement extrapolation method to complete the calculation of the dynamic stress intensity factor under the steady-state extension of the interface crack; specifically comprising the following steps:

[0056] Substitute the expressions of the interface crack mode I and II stress intensity factors obtained in step S4 into the calculation formula of the displacement extrapolation method to obtain the calculation formula of the dynamic stress intensity factor under steady-state expansion of the interface crack: In the formula is the dynamic stress intensity factor of the interface crack of the first material under steady-state propagation; is the dynamic stress intensity factor of the interface crack of the second material under steady-state propagation; N is the number of points taken by the displacement extrapolation method.

[0057] The method of the present invention is described below in conjunction with an embodiment:

[0058] Calculation conditions:

[0059] The diameter of the dual-material disk is 50 mm. Material I is sandstone with an elastic modulus of 2810 MPa, a Poisson's ratio of 0.28, and a density of ; Material II is concrete, with an elastic modulus of 1536MPa, a Poisson's ratio of 0.21, and a density of , the crack growth rate is , the displacement cloud diagram is as follows Figure 3 and Figure 4 As shown in the figure, since the crack is expanding at a high speed, in order to ensure the calculation accuracy at that moment, the time step difference between the two images is relatively small, so the difference in displacement before and after the time shown on the image is small; if the image is imported into the DIC processing software for analysis, it can be clearly seen that there is a difference in the data;

[0060] According to the technical solution of step S3, it is calculated that Then, according to step S4 and step S5, the crack tip displacement in the displacement cloud map is extracted, and the dynamic stress intensity factor of the crack tip is solved as follows: and .

[0061] The advantages of the method of the present invention are described below in conjunction with a comparative example:

[0062] At the same time, under the same conditions, for the above model, the stress intensity factor was calculated using the numerical model proposed by Huachao Deng in his 2022 paper "A new enrichment scheme for the interfacial crack modeling using the XFEM" to verify the calculation accuracy of the scheme of the present invention. Finally, the calculation comparison results are as follows Figure 5 and Figure 6 shown.

[0063] pass Figure 5 and Figure 6It can be seen that the calculation accuracy of this method can meet the calculation requirements, and compared with the calculation results obtained by the contour integration method using numerical simulation in the prior art, the semi-analytical solution obtained by the displacement extrapolation method used in this method is simpler and can be directly applied to the calculation of dynamic stress intensity factors in the laboratory, without the need to perform numerical simulation calculations to obtain stress field results and then calculate the dynamic stress intensity factor.

[0064] like Figure 7 The figure shows a schematic diagram of the functional modules of the system of the present invention: the system disclosed in the present invention for realizing the method for calculating the dynamic stress intensity factor under steady-state expansion of the interface crack comprises a wave parameter calculation module, an expansion speed calculation module, a first factor calculation module, a crack strength calculation module and a dynamic factor calculation module; the wave parameter calculation module, the expansion speed calculation module, the first factor calculation module, the crack strength calculation module and the dynamic factor calculation module are connected in series in sequence; the wave parameter calculation module is used to calculate the longitudinal wave velocity and the transverse wave velocity of the first material and the second material on both sides of the interface based on the acoustic emission test or the properties of the material itself, and upload the data information to the expansion speed calculation module; the expansion speed calculation module is used to calculate the expansion velocity under steady-state expansion of the interface crack based on the received data information, the digital image of the interface crack, and the position change information of the crack tip over a period of time, And upload the data information to the first factor calculation module; the first factor calculation module is used to construct the asymptotic field expression of the crack tip of the first material and the second material on both sides of the interface based on the weight function method according to the received data information, and calculate the type I and II stress intensity factors, and upload the data information to the crack strength calculation module; the crack strength calculation module is used to substitute the obtained type I and II stress intensity factors into the position values ​​corresponding to different positions on the digital image at different distances from the crack tip according to the received data information, calculate the expression of the interface crack with respect to the type I and II stress intensity factors, and upload the data information to the dynamic factor calculation module; the dynamic factor calculation module is used to substitute the obtained expression of the interface crack with respect to the type I and II stress intensity factors into the calculation formula of the displacement extrapolation method according to the received data information, and complete the calculation of the dynamic stress intensity factor under the steady-state extension of the interface crack.

Claims

1. A method for calculating the dynamic stress intensity factor under steady-state expansion of an interface crack, characterized in that The steps include: S1. Based on the acoustic emission test or the properties of the material itself, the longitudinal wave velocity and the transverse wave velocity of the first material and the second material on both sides of the interface are calculated; S2. Based on the digital image of the interface crack, the expansion velocity of the interface crack under steady-state expansion is calculated through the position change information of the crack tip over a period of time; specifically, the steps include: Based on the digital image of the interface crack, the coordinates of the crack tip at time t are obtained. and Coordinates of time The expansion velocity V of the interface crack under steady-state expansion is calculated to be ,in is the crack extension time, for The x-axis variation of the crack tip over time, for The y-axis change of the crack tip over time; S3. Based on the weight function method, the asymptotic field expressions of the crack tips of the first material and the second material on both sides of the interface are constructed, and the stress intensity factors of mode I and mode II are calculated; specifically, the steps are as follows: Based on the weight function method, the following formula is constructed: In the formula is the stress component of the jth material in the x direction; is the longitudinal wave calculation parameter of the jth material, and ; is the shear wave calculation parameter of the jth material, and ; is the magnitude of the shear wave in the polar coordinate system; is the first indefinite weight function of the jth material; is the magnitude angle of the shear wave in the polar coordinate system; is the second indefinite weight function of the jth material; is the magnitude of the longitudinal wave in the polar coordinate system; The third indefinite weight function is for the jth material; is the magnitude angle of the longitudinal wave in the polar coordinate system; is the fourth indefinite weight function of the jth material; is the stress component of the jth material in the y direction; is the shear stress of the jth material; is the displacement component of the jth material in the x direction; is the displacement component of the jth material in the y direction; is the singularity index, and the expression is in is the first calculation coefficient of the singularity index of the jth material, and ; is the second calculation coefficient of the singularity index of the jth material, and ; is the third calculation coefficient of the singularity index of the jth material, and ; is a positive integer set by yourself; is the longitudinal wave velocity of the first material and the second material on both sides of the interface, is the shear wave velocity of the first material and the second material on both sides of the interface; j is 1 or 2, j is 1 for the first material, and j is 2 for the second material; is the material density of the jth material; The stress intensity factor of mode I crack and mode II crack stress intensity factor The definition of , solving for and , expressed as and ; by and As the basis function, through the boundary conditions and continuity conditions, we can calculate In the formula is the first and second order coefficient matrix The first row of elements, The expression is , for The element in the mth row and jth column of is the second order coefficient matrix and , is the third second-order coefficient matrix and ; for The second row element in the is the fourth second-order coefficient matrix The element at row m and column n in The expression is , is the fifth second-order coefficient matrix and , is the sixth second-order coefficient matrix and ; is the seventh second-order coefficient matrix The element at row m and column n in , is the eighth second-order coefficient matrix and , is the ninth second-order coefficient matrix and ; S4. Substituting the type I and II stress intensity factors obtained in step S3 into the position values ​​corresponding to different positions on the digital image from the crack tip in step S2, and calculating the expressions of the interface crack with respect to the type I and II stress intensity factors; specifically comprising the following steps: In step S2, obtain The distance from the crack tip to the corresponding position x , y The displacement value in the direction is substituted into the expressions of the stress intensity factors of mode I and II obtained in step S3, and the expressions of the stress intensity factors of mode I and II for the interface crack are obtained as follows: In the formula is the difference in displacement in the x direction between the upper and lower surfaces at the i-th point; is the x-direction displacement recorded on the upper surface of the crack at the i-th point; is the x-direction displacement recorded on the lower surface of the crack at the i-th point; is the difference in displacement in the y direction between the upper and lower surfaces at the i-th point; is the y-direction displacement recorded on the upper surface of the crack at the i-th point; is the y-direction displacement recorded on the lower surface of the crack at the i-th point; is the distance from the i-th point to the crack tip; is the mode I stress intensity factor at the i-th point on the crack surface at the i-th point; is the mode II stress intensity factor at the i-th point on the crack surface; S5. Substitute the expressions of the interface crack mode I and II stress intensity factors obtained in step S4 into the calculation formula of the displacement extrapolation method to complete the calculation of the dynamic stress intensity factor under steady-state expansion of the interface crack.

2. The method for calculating the dynamic stress intensity factor under steady-state expansion of interface cracks according to claim 1 is characterized in that The step S1 specifically includes the following steps: Through the acoustic emission test, the longitudinal wave velocity of the first material and the second material on both sides of the interface is directly measured. and shear wave velocity ; The value of j is 1 or 2, j 1 represents the first material, and j 2 represents the second material; If the acoustic emission test cannot be performed, the longitudinal wave velocity of the first material and the second material on both sides of the interface is calculated based on the properties of the material itself using the following formula and shear wave velocity : In the formula is the first Lamé constant of the jth material; is the second Lamé constant of the jth material; is the material density of the jth material; The calculation formula is The calculation formula is In the formula is the Poisson’s ratio of the jth material; is the elastic modulus of the jth material.

3. The method for calculating the dynamic stress intensity factor under steady-state expansion of interface cracks according to claim 2 is characterized in that The step S5 specifically includes the following steps: Substitute the expressions of the interface crack mode I and II stress intensity factors obtained in step S4 into the calculation formula of the displacement extrapolation method to obtain the calculation formula of the dynamic stress intensity factor under steady-state expansion of the interface crack: In the formula is the mode I dynamic stress intensity factor of the crack surface under steady-state propagation of interface crack; is the mode II dynamic stress intensity factor of the crack surface under steady-state propagation of interface crack; N is the number of points taken by the displacement extrapolation method.

4. A system for realizing the method for calculating the dynamic stress intensity factor under steady-state expansion of an interface crack according to any one of claims 1 to 3, characterized in that It includes a wave parameter calculation module, an expansion speed calculation module, a first factor calculation module, a crack strength calculation module and a dynamic factor calculation module; the wave parameter calculation module, the expansion speed calculation module, the first factor calculation module, the crack strength calculation module and the dynamic factor calculation module are connected in series in sequence; the wave parameter calculation module is used to calculate the longitudinal wave velocity and the transverse wave velocity of the first material and the second material on both sides of the interface based on the acoustic emission test or the properties of the material itself, and upload the data information to the expansion speed calculation module; The expansion speed calculation module is used to calculate the expansion speed of the interface crack under steady-state expansion according to the received data information, based on the digital image of the interface crack and the position change information of the crack tip over a period of time, and upload the data information to the first factor calculation module; The first factor calculation module is used to construct the asymptotic field expression of the crack tip of the first material and the second material on both sides of the interface based on the received data information and the weight function method, and calculate the type I and II stress intensity factors, and upload the data information to the crack strength calculation module; The crack strength calculation module is used to substitute the obtained type I and II stress intensity factors into the position values ​​corresponding to different positions from the crack tip on the digital image according to the received data information, calculate the expressions of the interface cracks with respect to the type I and II stress intensity factors, and upload the data information to the dynamic factor calculation module; The dynamic factor calculation module is used to substitute the expressions of the interface crack mode I and II stress intensity factors into the calculation formula of the displacement extrapolation method according to the received data information, so as to complete the calculation of the dynamic stress intensity factor under the steady-state extension of the interface crack.

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