A method for evaluating ignition safety of defective charge

Abstract

The invention discloses a method for evaluating the ignition safety of a defective grain, which belongs to the technical field of solid rocket engines. The method comprises: based on a pre-constructed grid model of a defective grain, carrying out finite element numerical calculation of the ignition working condition of the defective grain, obtaining the strain energy release rate of the crack tip of the defective grain; based on the function of the pre-acquired propellant fracture energy release rate corresponding to the defective grain and the temperature and strain rate, obtaining the propellant fracture energy release rate corresponding to the defective grain at the current temperature and strain rate; comparing the strain energy release rate of the crack tip of the defective grain with the propellant fracture energy release rate corresponding to the defective grain at the current temperature and strain rate, obtaining the ignition safety evaluation result of the defective grain. The method can evaluate the ignition safety of engine grains with crack defects.

Description

Technical Field

[0001] The invention relates to an ignition safety assessment method for a defective charge, and belongs to the technical field of solid rocket engines. Background Art

[0002] During the transportation and combat readiness of missiles, various crack defects will appear inside the rocket engine grain.

[0003] Currently, there is no specific solution to the problem of ignition safety of engine propellants containing crack defects.

[0004] On the one hand, there is no experimental method worthy of reference for judging crack extension.

[0005] On the other hand, there is no reliable calculation software for the numerical calculation of the strain energy release rate at the crack tip of the defective grain structure. Summary of the invention

[0006] The object of the present invention is to provide a method for evaluating the ignition safety of defective grains, which can evaluate the ignition safety of engine grains containing crack defects.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A method for evaluating the ignition safety of a defective charge, comprising:

[0009] Based on the pre-built grid model of defective grain, the finite element numerical calculation of the ignition condition of the defective grain is carried out to obtain the strain energy release rate at the crack tip of the defective grain;

[0010] Based on the pre-acquired function of the propellant fracture energy release rate corresponding to the defective grain column and the temperature and strain rate, the propellant fracture energy release rate corresponding to the defective grain column at the current temperature and strain rate is obtained;

[0011] The strain energy release rate of the crack tip of the defective grain is compared with the propellant fracture energy release rate corresponding to the defective grain at the current temperature and strain rate to obtain an ignition safety assessment result of the defective grain;

[0012] Wherein, the grid model of the defective grain column is constructed based on the actual geometric configuration of the defective grain column;

[0013] The function of the propellant fracture energy release rate corresponding to the defective grain column and the temperature and strain rate is obtained by conducting fracture energy test experiments at different temperatures and tensile rates on the propellant corresponding to the defective grain column using a preset fracture energy test device.

[0014] In combination with the first aspect, further, the defective grains include grains containing type I defects and grains containing type II defects. Accordingly, the propellant corresponding to the grains containing type I defects is type I propellant, and the propellant corresponding to the grains containing type II defects is type II propellant.

[0015] In combination with the first aspect, further, the fracture energy test device includes a clamp for clamping the propellant, and a testing machine connected to the clamp and used to stretch the propellant.

[0016] In combination with the first aspect, further, the clamp includes a first clamp for clamping Type I propellant, the first clamp is bonded to both ends of the Type I propellant parallel to its crack propagation direction, and the testing machine is connected to the first clamp to stretch the Type I propellant perpendicular to its crack propagation direction.

[0017] In combination with the first aspect, further, the clamp includes a second clamp for clamping the Type II propellant, the second clamp is an integrally formed L-shaped structure, the first side of the L-shaped structure is bonded to both ends of the Type II propellant parallel to its crack propagation direction, and the testing machine is connected to the second side of the L-shaped structure to stretch the Type II propellant parallel to its crack propagation direction.

[0018] In combination with the first aspect, further, a fracture energy test test is performed on the propellant corresponding to the defective grain column at different temperatures and tensile rates using a preset fracture energy test device, and the function of the fracture energy release rate of the propellant corresponding to the defective grain column and the temperature and strain rate is obtained, including:

[0019] The fracture energy test device is used to carry out fracture energy test at different temperatures and stretching rates on the propellant corresponding to the defective grain column, and the force-displacement curve of the propellant corresponding to the defective grain column at various temperatures and stretching rates is obtained;

[0020] Based on the force-displacement curves of the propellant corresponding to the defective grain at various temperatures and stretching rates, the fracture energy release rate of the propellant corresponding to the defective grain at various temperatures and stretching rates is calculated;

[0021] The parameters of the fracture energy release rate of the propellant corresponding to the defective grain column at various temperatures and stretching rates are fitted to obtain the function of the fracture energy release rate of the propellant corresponding to the defective grain column with temperature and strain rate.

[0022] In combination with the first aspect, further, the calculation formula for the fracture energy release rate of the propellant corresponding to the defective grain at various temperatures and stretching rates is:

[0023] ;

[0024] in, , It represents the fracture energy release rate of the type I propellant corresponding to the grain containing type I defects and the type II propellant corresponding to the grain containing type II defects at various temperatures and stretching rates. , It represents the area enclosed by the force-displacement curves of the type I propellant corresponding to the grain containing type I defects and the type II propellant corresponding to the grain containing type II defects at various temperatures and stretching rates and the coordinate axis, , It represents the crack extension length of Type I propellant corresponding to the grain containing Type I defects and Type II propellant corresponding to the grain containing Type II defects. It indicates the thickness of Type I propellant corresponding to a grain containing Type I defects or the thickness of Type II propellant corresponding to a grain containing Type II defects.

[0025] Combined with the first aspect, further, based on the pre-constructed grid model of defective grain, finite element numerical calculation of ignition condition is carried out on the defective grain to obtain the strain energy release rate at the crack tip of the defective grain, including:

[0026] Based on the pre-built defective grain grid model, the crack tip of the defective grain is meshed to obtain the crack tip grid;

[0027] The displacement of the crack tip mesh under each load step is extracted and projected to the preset - Reference coordinate system;

[0028] exist - Calculate the strain and stress of each integration point of each element of the crack tip mesh in the reference coordinate system;

[0029] Based on the strain and stress of the integration point of each unit of the crack tip mesh, the internal force of the node of each unit of the crack tip mesh is calculated;

[0030] Based on the internal forces of the nodes of each unit of the crack tip mesh and the displacement of the crack tip mesh, the strain energy release rate of the crack tip of the defective charge is calculated;

[0031] The calculation formula of the strain energy release rate at the crack tip of the defective charge is:

[0032] ;

[0033] in, , It represents the strain energy release rate at the crack tip of the grain containing type I defects and type II defects. , Represents the node corresponding to the crack tip in the crack tip mesh exist direction, The internal force of direction, , Represents the node corresponding to the crack propagation direction in the crack tip mesh exist direction, Direction displacement, Represents the average size of each element in the crack tip mesh.

[0034] In combination with the first aspect, further, the crack tip grid is a 2×2 quadrilateral grid, the central axis of the crack tip grid is parallel to the crack propagation direction of the defective grain, and the average size of each unit of the crack tip grid is consistent with the average size of each unit of the defective grain grid model.

[0035] In combination with the first aspect, further, the strain energy release rate of the crack tip of the defective grain is compared with the propellant fracture energy release rate corresponding to the defective grain at the current temperature and strain rate, and the ignition safety assessment result of the defective grain is obtained, including:

[0036] Compare the strain energy release rate of the crack tip of the defective grain with the propellant fracture energy release rate corresponding to the defective grain at the current temperature and strain rate, and if the preset judgment formula is satisfied at any time during the ignition period, it is determined that the ignition of the defective grain is safe;

[0037] Wherein, the determination formula is:

[0038] ;

[0039] in, , It represents the strain energy release rate at the crack tip of the grain containing type I defects and type II defects. , It represents the function of the propellant fracture energy release rate corresponding to the grain containing type I defects and the grain containing type II defects as a function of temperature and strain rate. Indicates the current temperature. represents the current strain rate, , It represents the propellant fracture energy release rate corresponding to the grain containing type I defects and type II defects at the current temperature and strain rate.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] The ignition safety assessment method of defective grain provided by the present invention performs finite element numerical calculation of ignition conditions on the defective grain based on a grid model of the defective grain to obtain the strain energy release rate of the crack tip of the defective grain; based on the function of the propellant fracture energy release rate corresponding to the defective grain and the temperature and strain rate, obtains the propellant fracture energy release rate corresponding to the defective grain at the current temperature and strain rate; and by comparing the strain energy release rate at the crack tip of the defective grain with the propellant fracture energy release rate corresponding to the defective grain at the current temperature and strain rate, the ignition safety assessment result of the defective grain can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a flow chart of the ignition safety assessment method of defective charge provided by an embodiment of the present invention;

[0043] Figure 2 1 is a schematic diagram of the structure of a fracture energy test device provided by an embodiment of the present invention, wherein (a) is a schematic diagram of the application state of the fracture energy test device on a type I propellant, and (b) is a schematic diagram of the application state of the fracture energy test device on a type II propellant;

[0044] Figure 3 Schematic diagram of force-displacement curves of the propellant corresponding to the defective grain provided in the embodiment of the present invention at various temperatures and stretching rates;

[0045] Figure 4 1 is a schematic diagram of the actual geometric configuration of a defective star-shaped grain and its crack tip grid division provided by an embodiment of the present invention, wherein (a) is a schematic diagram of the actual geometric configuration of a defective star-shaped grain, and (b) is a schematic diagram of the crack tip grid of a defective star-shaped grain;

[0046] Figure 5 The crack tip grid of the defective star-shaped charge provided by the embodiment of the present invention is - Schematic diagram of projection in the reference coordinate system. DETAILED DESCRIPTION

[0047] The technical solution of the present application is further described in detail below in conjunction with specific implementation methods.

[0048] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and should not be construed as limitations on the present application. In the absence of conflict, the embodiments of the present application and the technical features in the embodiments may be combined with each other.

[0049] Embodiment 1:

[0050] Figure 1 This is a flow chart of a method for evaluating the ignition safety of a defective charge provided in this embodiment. This flow chart only shows the logical sequence of the method in this embodiment. Different methods can be used without conflict. Figure 1 The steps shown or described are accomplished in the order shown.

[0051] See also Figure 1 The ignition safety assessment method for defective charge provided in this embodiment specifically includes the following steps:

[0052] Step 1: Based on the pre-built grid model of defective grain, finite element numerical calculation of ignition condition is performed on the defective grain to obtain the strain energy release rate at the crack tip of the defective grain;

[0053] In this embodiment, the grid model of the defective grain is constructed based on the actual geometric configuration of the defective grain.

[0054] Based on the pre-built grid model of defective grain, the finite element numerical calculation of the ignition condition of the defective grain is carried out to obtain the strain energy release rate at the crack tip of the defective grain, which specifically includes the following steps:

[0055] Step 1: Based on the pre-built defective grain grid model, mesh the crack tip of the defective grain to obtain the crack tip grid;

[0056] In this embodiment, the crack tip grid is a 2×2 quadrilateral grid, the central axis of the crack tip grid is parallel to the crack extension direction of the defective grain, and the average size of each unit of the crack tip grid is consistent with the average size of each unit of the defective grain grid model. In addition to setting a 2×2 quadrilateral grid at the crack tip, triangle or quadrilateral grids can be set at other positions.

[0057] Step 2: Extract the displacement of the crack tip mesh under each load step and project it to the preset - Reference coordinate system;

[0058] Step 3: - Calculate the strain and stress of each integration point of each element of the crack tip mesh in the reference coordinate system;

[0059] Step 4: Based on the strain and stress of the integration point of each unit of the crack tip mesh, calculate the internal force of the node of each unit of the crack tip mesh;

[0060] Step 5: Based on the internal forces of the nodes of each unit of the crack tip mesh and the displacement of the crack tip mesh, calculate the strain energy release rate of the crack tip of the defective charge.

[0061] In this embodiment, based on the internal force of the nodes of each unit of the crack tip grid and the displacement of the crack tip grid, the strain energy release rate of the crack tip of the defective charge is obtained by using the interpolation method.

[0062] The calculation formula for the strain energy release rate at the crack tip of a defective charge is:

[0063] ;

[0064] in, , It represents the strain energy release rate at the crack tip of the grain containing type I defects and type II defects. , Represents the node corresponding to the crack tip in the crack tip mesh exist direction, The internal force of direction, , Represents the node corresponding to the crack propagation direction in the crack tip mesh exist direction, Direction displacement, Represents the average size of each element in the crack tip mesh.

[0065] In the actual calculation process, the engine structure must be calculated according to the full model, and the axisymmetric model cannot be used. Figure 4 As shown, a defective star-shaped charge is used as an example for explanation.

[0066] like Figure 4 As shown in (a), a grid model of a defective star-shaped grain is constructed based on the actual geometric configuration of the defective star-shaped grain.

[0067] like Figure 4 As shown in (b), based on the mesh model of defective star-shaped grain, the crack tip of the defective star-shaped grain is meshed. As the center point, the crack propagation direction of the defective star-shaped grain is parallel to As the central axis, a 2×2 quadrilateral grid is constructed to obtain the crack tip grid of the defective star-shaped charge. Figure 4 As shown in (b), the quadrilateral ,quadrilateral ,quadrilateral ,quadrilateral are the four elements of the crack tip grid of the defective star-shaped charge, , , , For unit 4 nodes, , , , For unit 4 nodes, , , , For unit 4 nodes, , , , For unit The average size of each unit in the crack tip mesh of the defective star-shaped grain is consistent with the average size of each unit in the defective star-shaped grain mesh model. The integration points of each unit in the crack tip mesh of the defective star-shaped grain are Figure 4 Not shown.

[0068] like Figure 5 As shown in the figure, the displacement of the crack tip grid of the defective star-shaped charge under each load step condition is extracted and projected to the preset - Reference coordinate system, - In the reference coordinate system, the crack tip of the defective star-shaped charge is the coordinate origin, Direction Axis positive direction, Direction Axis positive direction; - The strain and stress of the integral point of each unit of the crack tip grid of the defective star-shaped charge are calculated in the reference coordinate system; the internal force of the node of each unit of the crack tip grid of the defective star-shaped charge is calculated based on the strain and stress of the integral point of each unit of the crack tip grid of the defective star-shaped charge; based on the internal force of the node of each unit of the crack tip grid and the displacement of the crack tip grid, the strain energy release rate of the crack tip of the defective charge is obtained by the interpolation method.

[0069] Step 2: Based on the pre-acquired function of the propellant fracture energy release rate corresponding to the defective grain column and the temperature and strain rate, the propellant fracture energy release rate corresponding to the defective grain column at the current temperature and strain rate is obtained;

[0070] In this embodiment, the function of the fracture energy release rate of the propellant corresponding to the defective grain column and the temperature and strain rate is obtained by conducting fracture energy test experiments on the propellant corresponding to the defective grain column at different temperatures and tensile rates using a preset fracture energy test device.

[0071] The fracture energy test device is used to carry out fracture energy test on the propellant corresponding to the defective grain column at different temperatures and tensile rates, and the function of the fracture energy release rate of the propellant corresponding to the defective grain column and the temperature and strain rate is obtained, which specifically includes the following steps:

[0072] Step 1: Use a preset fracture energy test device to carry out fracture energy test tests on the propellant corresponding to the defective grain column at different temperatures and stretching rates to obtain the force-displacement curves of the propellant corresponding to the defective grain column at various temperatures and stretching rates;

[0073] In this embodiment, the defective grains include grains containing type I defects and grains containing type II defects. Accordingly, the propellant corresponding to the grains containing type I defects is type I propellant, and the propellant corresponding to the grains containing type II defects is type II propellant. Figure 2 As shown in (a), Type II propellant is Figure 2 In this embodiment, the thickness of the type I propellant is the same as that of the type II propellant.

[0074] The fracture energy test device includes a fixture for clamping the propellant, and a test machine connected to the fixture and used to stretch the propellant. In this embodiment, the thickness of the fixture is the same as the thickness of the propellant.

[0075] like Figure 2 As shown in (a), for Type I propellant, the fixture includes a first fixture for clamping Type I propellant, the first fixture is bonded to two ends of Type I propellant parallel to its crack propagation direction, the testing machine is connected to the first fixture, and the Type I propellant is stretched perpendicular to its crack propagation direction. In this embodiment, the first fixture is bonded to two ends of Type I propellant parallel to its crack propagation direction by high-strength glue, and the testing machine is connected to the first fixture by a pin.

[0076] like Figure 2 As shown in (b), for Type II propellant, the fixture includes a second fixture for clamping Type II propellant, the second fixture is an integrally formed L-shaped structure, the first side of the L-shaped structure is bonded to the two ends of Type II propellant parallel to the crack propagation direction, the testing machine is connected to the second side of the L-shaped structure, and the Type II propellant is stretched parallel to the crack propagation direction. In this embodiment, the first side of the L-shaped structure is bonded to the two ends of Type II propellant parallel to the crack propagation direction by high-strength glue, and the testing machine is connected to the second side of the L-shaped structure by a pin.

[0077] When using a fracture energy test device to conduct fracture energy tests at different temperatures and stretching rates on the propellant corresponding to the defective grain, it is necessary to ensure that the temperature and stretching rate cover the actual conditions of engine ignition.

[0078] In this embodiment, a fracture energy test device is used to carry out fracture energy test tests on the propellant corresponding to the defective grain column at different temperatures and stretching rates, and the force-displacement curves of the propellant corresponding to the defective grain column at various temperatures and stretching rates are obtained. Figure 3 shown. Figure 3 middle, Indicates the origin of coordinates, the horizontal coordinate It represents the displacement of the propellant corresponding to the defective grain at the current temperature and stretching rate. It represents the force of the propellant corresponding to the defective grain at the current temperature and stretching rate.

[0079] Step 2: Based on the force-displacement curves of the propellant corresponding to the defective grain column at various temperatures and stretching rates, calculate the fracture energy release rate of the propellant corresponding to the defective grain column at various temperatures and stretching rates;

[0080] In this embodiment, the calculation formula for the fracture energy release rate of the propellant corresponding to the defective grain at various temperatures and stretching rates is:

[0081] ;

[0082] in, , It represents the fracture energy release rate of the type I propellant corresponding to the grain containing type I defects and the type II propellant corresponding to the grain containing type II defects at various temperatures and stretching rates. , It represents the area enclosed by the force-displacement curves of the type I propellant corresponding to the grain containing type I defects and the type II propellant corresponding to the grain containing type II defects at various temperatures and stretching rates and the coordinate axis, , It represents the crack extension length of Type I propellant corresponding to the grain containing Type I defects and Type II propellant corresponding to the grain containing Type II defects. It indicates the thickness of Type I propellant corresponding to a grain containing Type I defects or the thickness of Type II propellant corresponding to a grain containing Type II defects.

[0083] Step 3: Perform parameter fitting on the fracture energy release rate of the propellant corresponding to the defective grain column at various temperatures and stretching rates to obtain the function of the fracture energy release rate of the propellant corresponding to the defective grain column with temperature and strain rate.

[0084] In this embodiment, the discrete points of the fracture energy release rates of the type I propellant corresponding to the type I defective grain column and the type II propellant corresponding to the type II defective grain column at various temperatures and stretching rates calculated in step 2 are fitted with parameters to obtain the function of the fracture energy release rate of the type I propellant corresponding to the type I defective grain column and the type II propellant corresponding to the type II defective grain column with temperature and strain rate. , ,in, Indicates temperature, represents the strain rate.

[0085] Step 3: Compare the strain energy release rate at the crack tip of the defective grain with the propellant fracture energy release rate corresponding to the defective grain at the current temperature and strain rate to obtain the ignition safety assessment result of the defective grain.

[0086] In this embodiment, the strain energy release rate of the crack tip of the defective grain is compared with the propellant fracture energy release rate corresponding to the defective grain at the current temperature and strain rate, and obtaining the ignition safety assessment result of the defective grain specifically includes: comparing the strain energy release rate of the crack tip of the defective grain with the propellant fracture energy release rate corresponding to the defective grain at the current temperature and strain rate, and if the preset judgment formula is satisfied at any time during the ignition period, it is judged that the ignition of the defective grain is safe; otherwise, it is judged that the ignition of the defective grain is unsafe.

[0087] In this embodiment, the determination formula is:

[0088] ;

[0089] in, , It represents the strain energy release rate at the crack tip of the grain containing type I defects and type II defects. , It represents the function of the propellant fracture energy release rate corresponding to the grain containing type I defects and the grain containing type II defects as a function of temperature and strain rate. Indicates the current temperature. represents the current strain rate, , It represents the propellant fracture energy release rate corresponding to the grain containing type I defects and type II defects at the current temperature and strain rate.

[0090] The ignition safety assessment method for defective grains provided in this embodiment performs finite element numerical calculation of ignition conditions on defective grains based on a grid model of defective grains to obtain the strain energy release rate at the crack tip of the defective grains; obtains the propellant fracture energy release rate corresponding to the defective grains at the current temperature and strain rate based on the function of the propellant fracture energy release rate corresponding to the defective grains and the temperature and strain rate; and obtains the ignition safety assessment result of the defective grains by comparing the strain energy release rate at the crack tip of the defective grains with the propellant fracture energy release rate corresponding to the defective grains at the current temperature and strain rate.

[0091] The fracture energy test device provided in this embodiment can carry out fracture energy test tests at different temperatures and stretching rates on Type I propellant and Type II propellant respectively, to ensure that cracks in the propellant expand according to a preset fracture mode.

[0092] The above are only preferred implementations of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A method for evaluating the ignition safety of a defective charge, characterized in that: include: Based on the pre-built grid model of defective grain, the finite element numerical calculation of the ignition condition of the defective grain is carried out to obtain the strain energy release rate at the crack tip of the defective grain; Based on the pre-acquired function of the propellant fracture energy release rate corresponding to the defective grain column and the temperature and strain rate, the propellant fracture energy release rate corresponding to the defective grain column at the current temperature and strain rate is obtained; The strain energy release rate of the crack tip of the defective grain is compared with the propellant fracture energy release rate corresponding to the defective grain at the current temperature and strain rate to obtain an ignition safety assessment result of the defective grain; Wherein, the grid model of the defective grain column is constructed based on the actual geometric configuration of the defective grain column; The function of the propellant fracture energy release rate corresponding to the defective grain column and the temperature and strain rate is obtained by carrying out fracture energy test tests at different temperatures and tensile rates on the propellant corresponding to the defective grain column using a preset fracture energy test device; The fracture energy test device is used to carry out fracture energy test on the propellant corresponding to the defective grain column at different temperatures and tensile rates, and the functions of the fracture energy release rate of the propellant corresponding to the defective grain column and the temperature and strain rate are obtained, including: The fracture energy test device is used to carry out fracture energy test at different temperatures and stretching rates on the propellant corresponding to the defective grain column, and the force-displacement curve of the propellant corresponding to the defective grain column at various temperatures and stretching rates is obtained; Based on the force-displacement curves of the propellant corresponding to the defective grain at various temperatures and stretching rates, the fracture energy release rate of the propellant corresponding to the defective grain at various temperatures and stretching rates is calculated; The parameters of the fracture energy release rate of the propellant corresponding to the defective grain column at various temperatures and stretching rates are fitted to obtain the function of the fracture energy release rate of the propellant corresponding to the defective grain column with the temperature and strain rate; The calculation formula for the fracture energy release rate of the propellant corresponding to the defective grain column at various temperatures and stretching rates is: ； in, , It represents the fracture energy release rate of the type I propellant corresponding to the grain containing type I defects and the type II propellant corresponding to the grain containing type II defects at various temperatures and stretching rates. , It represents the area enclosed by the force-displacement curves of the type I propellant corresponding to the grain containing type I defects and the type II propellant corresponding to the grain containing type II defects at various temperatures and stretching rates and the coordinate axis, , It represents the crack extension length of Type I propellant corresponding to the grain containing Type I defects and Type II propellant corresponding to the grain containing Type II defects. It indicates the thickness of Type I propellant corresponding to grains containing Type I defects or Type II propellant corresponding to grains containing Type II defects; Based on the pre-built grid model of defective grain, the finite element numerical calculation of the ignition condition of the defective grain is carried out to obtain the strain energy release rate at the crack tip of the defective grain, including: Based on the pre-built defective grain grid model, the crack tip of the defective grain is meshed to obtain the crack tip grid; The displacement of the crack tip mesh under each load step is extracted and projected to the preset - Reference coordinate system; exist - Calculate the strain and stress of each integration point of each element of the crack tip mesh in the reference coordinate system; Based on the strain and stress of the integration point of each unit of the crack tip mesh, the internal force of the node of each unit of the crack tip mesh is calculated; Based on the internal forces of the nodes of each unit of the crack tip mesh and the displacement of the crack tip mesh, the strain energy release rate of the crack tip of the defective charge is calculated; The calculation formula of the strain energy release rate at the crack tip of the defective charge is: ； in, , It represents the strain energy release rate at the crack tip of the grain containing type I defects and type II defects. , Represents the node corresponding to the crack tip in the crack tip mesh exist direction, The internal force of direction, , Represents the node corresponding to the crack propagation direction in the crack tip mesh exist direction, Direction displacement, Represents the average size of each element in the crack tip mesh.

2. The method for evaluating ignition safety of defective charge according to claim 1, characterized in that: The defective grains include grains containing type I defects and grains containing type II defects. The propellant corresponding to the grains containing type I defects is type I propellant, and the propellant corresponding to the grains containing type II defects is type II propellant.

3. The method for evaluating ignition safety of defective charge according to claim 1, characterized in that: The fracture energy test device comprises a clamp for clamping the propellant, and a testing machine connected to the clamp for stretching the propellant.

4. The method for evaluating ignition safety of defective charge according to claim 3, characterized in that: The clamp includes a first clamp for clamping Type I propellant, the first clamp is bonded to two ends of the Type I propellant parallel to its crack extension direction, and the testing machine is connected to the first clamp to stretch the Type I propellant perpendicular to its crack extension direction.

5. The method for evaluating ignition safety of defective charge according to claim 3, characterized in that: The clamp includes a second clamp for clamping the Type II propellant, the second clamp is an integrally formed L-shaped structure, a first side of the L-shaped structure is bonded to two ends of the Type II propellant parallel to its crack propagation direction, and the testing machine is connected to the second side of the L-shaped structure to stretch the Type II propellant parallel to its crack propagation direction.

6. The method for evaluating ignition safety of defective charge according to claim 1, characterized in that: The crack tip grid is a 2×2 quadrilateral grid, the central axis of the crack tip grid is parallel to the crack propagation direction of the defective grain, and the average size of each unit of the crack tip grid is consistent with the average size of each unit of the defective grain grid model.

7. The method for evaluating ignition safety of defective charge according to claim 1, characterized in that: Comparing the strain energy release rate at the crack tip of the defective grain with the propellant fracture energy release rate corresponding to the defective grain at the current temperature and strain rate, obtaining the ignition safety assessment result of the defective grain includes: Compare the strain energy release rate of the crack tip of the defective grain with the propellant fracture energy release rate corresponding to the defective grain at the current temperature and strain rate, and if the preset judgment formula is satisfied at any time during the ignition period, it is determined that the ignition of the defective grain is safe; Wherein, the determination formula is: ； in, , It represents the strain energy release rate at the crack tip of the grain containing type I defects and type II defects. , It represents the function of the propellant fracture energy release rate corresponding to the grain containing type I defects and the grain containing type II defects as a function of temperature and strain rate. Indicates the current temperature. represents the current strain rate, , It represents the propellant fracture energy release rate corresponding to the grain containing type I defects and type II defects at the current temperature and strain rate.

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