CN118886262A - A method, device and medium for simulating electron beam selective melting additive process - Google Patents

Abstract

The present application discloses a method, device and medium for simulating an electron beam selective melting additive process, and relates to the field of additive manufacturing. The method includes: establishing a finite element model of electron beam selective melting; determining the electron beam energy based on the actual additive process of electron beam selective melting; determining the region where the electron beam energy application surface is located based on the finite element model at any moment of the simulation calculation; determining the free interface set according to the liquid volume fraction of each grid unit in the region where the electron beam energy application surface is located; excluding the pore interface and the blocked interface in the free interface set to obtain a subset of free interfaces to which electron beam energy is applied; applying electron beam energy to each unit in the free interface subset to establish a heat source model at the current moment; and simulating the additive process based on the heat source model at the current moment. The present application can automatically track the transient energy application free interface, and apply all the heat source energy to the free interface, thereby improving the simulation accuracy.

Description

A method, device and medium for simulating electron beam selective melting additive process

Technical Field

The present application relates to the field of additive manufacturing, and in particular to a method, device and medium for simulating an electron beam selective melting additive process.

Background Art

Electron Beam Selective Melting (EBSM) is a high-energy-density additive manufacturing method with the advantages of high energy absorption rate, concentrated power density, fast scanning speed, and low residual thermal stress. It can improve the quality and efficiency of additive manufacturing of metal parts and is a metal additive manufacturing technology with great prospects. The heat source characteristics of EBSM additive are highly concentrated local energy, instantaneous and keyhole effects. Especially for the keyhole-type selective melting process, the instantaneous change of the keyhole directly affects the quality of additive manufacturing.

Numerical simulation based on computational fluid dynamics (CFD) is an effective method to deeply explore the evolution of keyholes and the mechanism of defect formation in the EBSM additive process. Compared with experiments, it can more comprehensively and deeply study the real-time evolution of the molten pool, the surface quality of the additive, the mechanism of defect formation, etc. in the EBSM additive process. The reasonable construction and application of the heat source model is an extremely important link in the electron beam selective melting simulation, which essentially determines the rationality and effectiveness of the temperature field and flow field simulation.

At present, the research on the heat source model and modeling method of electron beam selective melting mainly adopts the Gaussian body heat source model with regular shape. The body heat source model applies the heat source in a regular geometric area. However, the actual molten pool geometry is irregular and there are gaps (space close to vacuum) between the powder particles in the powder bed. The use of the body heat source model will inevitably apply part of the heat source energy to the gap instead of the deposition layer or substrate below the gap, which is inconsistent with the actual situation and leads to inaccurate simulation results.

Summary of the invention

The purpose of this application is to provide a method, device and medium for simulating an electron beam selective melting additive process, which can automatically track the transient energy application free interface and apply all the heat source energy to the free interface to improve the simulation accuracy.

To achieve the above objectives, this application provides the following solutions:

In a first aspect, the present application provides a method for simulating an electron beam selective melting additive process, comprising:

Establish a finite element model for electron beam selective melting;

Determine the electron beam energy based on the actual additive process of electron beam selective melting;

At any moment of the simulation calculation, based on the finite element model, determining the region where the electron beam energy application surface is located at the current moment; the region where the electron beam energy application surface is located includes a plurality of grid units;

Extracting the liquid phase volume fraction of each grid unit in the region where the electron beam energy application surface is located at the current moment, and determining all free interface units in the region where the electron beam energy application surface is located at the current moment according to the liquid phase volume fraction of each grid unit in the region where the electron beam energy application surface is located at the current moment, and obtaining a free interface set;

According to the three-dimensional coordinates of each free interface unit in the free interface set, the pore interface unit and the blocked interface unit in the free interface set are excluded to obtain a free interface subset to which electron beam energy is applied; wherein the x-axis coordinate and the y-axis coordinate are directions of the additive plane, and the z-axis is the thickness direction;

Applying the electron beam energy to each unit in the free interface subset to establish a heat source model at the current moment;

The additive process is simulated based on the heat source model at the current moment.

In a second aspect, the present application provides a computer device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the above-mentioned electron beam selective melting additive process simulation method.

In a third aspect, the present application provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the above-mentioned electron beam selective melting additive process simulation method.

According to the specific embodiments provided in this application, this application discloses the following technical effects:

The present application provides a simulation method, device and medium for electron beam selective melting additive process. In the simulation calculation process, according to the liquid phase volume fraction of each grid unit in the area where the electron beam energy application surface is located at the current moment, the free interface set in the area where the electron beam energy application surface is located at the current moment is determined, and then according to the three-dimensional coordinates of each free interface unit in the free interface set, the pore interface unit and the blocked interface unit in the free interface set are excluded, thereby obtaining a subset of free interfaces to which electron beam energy is applied, and then the electron beam energy is applied to each unit in the free interface subset, thereby realizing the heat source modeling of the EBSM additive process at each moment. The heat source modeling method can automatically determine the shielding of the deposited layer or substrate by pores and particles, and then accurately and automatically track the transient energy application free interface, which is more in line with the actual thermal effect of the additive process. The heat source modeling method does not involve heat source shape restrictions, and can be directly applied to the simulation of single-pass, multi-pass and multi-layer selective melting processes. It can be applied to additive processes with conductive and keyhole-type molten pool formation mechanisms, thereby improving the simulation accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

FIG1 is a diagram showing an application environment of a method for simulating an electron beam selective melting additive process in an embodiment of the present application;

FIG2 is a schematic diagram of the overall process of a method for simulating an electron beam selective melting additive process provided by an embodiment of the present application;

FIG3 is a detailed schematic diagram of a method for simulating an electron beam selective melting additive process according to an embodiment of the present application;

FIG4 is a schematic diagram of a geometric structure model of electron beam selective melting;

FIG5 is a schematic diagram of eliminating the blocked interface;

FIG6 is a schematic diagram of eliminating the pore interface;

FIG. 7 is a schematic diagram of the structure of a computer device provided in an embodiment of the present application.

DETAILED DESCRIPTION

The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

The electron beam selective melting additive process simulation method provided in the embodiment of the present application can be applied to the application environment as shown in Figure 1. Among them, the terminal 102 communicates with the server 104 through the network. The data storage system can store the data that the server 104 needs to process. The data storage system can be set up separately, or it can be integrated on the server 104, or it can be placed on the cloud or other servers. The terminal 102 can send the relevant parameters of the electron beam selective melting additive process to the server 104. After receiving the relevant parameters of the electron beam selective melting additive process, the server 104 simulates the additive process. The server 104 can feedback the simulation calculation results to the terminal 102. In addition, in some embodiments, the electron beam selective melting additive process simulation method can also be implemented by the server 104 or the terminal 102 alone.

The terminal 102 may be, but is not limited to, various desktop computers, laptop computers, smart phones, tablet computers, IoT devices, and portable wearable devices. The IoT devices may be smart speakers, smart TVs, smart air conditioners, smart vehicle-mounted devices, etc. The portable wearable devices may be smart watches, smart bracelets, head-mounted devices, etc. The server 104 may be implemented as an independent server or a server cluster consisting of multiple servers, or may be a cloud server.

In an exemplary embodiment, as shown in FIG. 2 and FIG. 3 , a method for simulating an electron beam selective melting additive process is provided. The method is executed by a computer device, and specifically can be executed by a computer device such as a terminal or a server alone, or can be executed by a terminal and a server together. In the embodiment of the present application, the method is applied to the server 104 in FIG. 1 as an example for description, and includes the following steps 201 to 207. Among them:

Step 201, establishing a finite element model of electron beam selective melting.

In an exemplary embodiment, step 201 includes:

(11) Establishing a geometric structure model for electron beam selective melting. As shown in FIG4 , the geometric structure model includes a substrate 401, a deposition layer 402, a powder bed 403, and an approximate vacuum region 404. If a single-layer deposition simulation analysis is performed, the deposition layer 402 is not required. The powder bed 403 is composed of a plurality of powder particles. The size of the substrate 401, the size of the deposition layer 402, the distribution and size of the powder particles are consistent with the actual ones, and the height of the approximate vacuum region 404 is greater than twice the maximum powder particle diameter.

Specifically, a geometric structure model of electron beam selective melting is established according to the actual powder spreading situation or the powder bed distribution obtained by simulation calculation.

(12) Meshing the geometric structure model, giving material properties, setting the initial temperature, initial liquid phase volume fraction and initial fluid velocity of each mesh unit, and setting boundary conditions to obtain a finite element model of electron beam selective melting.

Specifically, the material properties of each region (substrate 401, deposition layer 402, powder bed 403, approximate vacuum region 404) are set to establish a finite element model. The grid unit size of the powder bed 403 region is less than 1/10 of the average powder particle size, and the grid units of other regions can be gradually sparse, and the size of the largest grid unit does not exceed the diameter of the largest powder particle. According to actual conditions, the substrate 401, deposition layer 402 and powder bed 403 regions are liquid materials, and the approximate vacuum region 404 is gas material.

Furthermore, based on the finite element model of electron beam selective melting, the simulation analysis method is determined to be a multiphase flow (Volume of Fluid, VOF) model method of computational fluid dynamics. According to the actual situation, the surface tension coefficient of the material and the Lee model parameters of the gas-liquid phase change are given, and the initial settings (t=0) and material phase information related to the calculation of the method are determined. The material phase information includes the initial temperature of each grid unit, the initial liquid phase volume fraction of each grid unit, and the initial velocity of the fluid in each grid unit. According to the actual additive process, the starting position (x _o , _yo , z _o ) of the electron beam additive and the moving speed v _x and _vy of the electron beam are determined. According to the actual situation, the velocity inlet and the pressure outlet are set for any two boundary surfaces of the approximate vacuum domain 404, and the radiation heat transfer conditions are set for all other boundary surfaces.

Step 202: Determine the electron beam energy based on the actual additive process of electron beam selective melting. The electron beam energy includes the energy density acting at each point on the free interface of the molten pool during the additive process.

In an exemplary embodiment, step 202 includes:

(21) Obtain the energy effective radius of the electron beam, the acceleration voltage U of the electron beam, the current intensity I of the electron beam, and the energy absorption coefficient (heat absorption rate) η of the material to the electron beam.

(22) According to the electron beam acceleration voltage U, the electron beam current intensity I and the material's energy absorption coefficient η of the electron beam, the energy power acting on the free interface of the molten pool is calculated. That is, the energy power P acting on the free surface of the molten pool during welding is calculated: P = ηUI.

(23) The energy density at each point on the free interface of the molten pool during the additive process is determined based on the energy power acting on the free interface of the molten pool, the energy effective radius of the electron beam, and the position of the current heat source center.

This application defines the x-axis coordinate and the y-axis coordinate as the additive plane direction, and the z-axis as the thickness direction.

Specifically, the electron beam energy is Gaussian distributed. Assuming that its energy effective radius is r ₀ , the energy density acting on the free interface of the molten pool at point (x ₁ ,y ₁ ) during the additive process is:

Among them, q _S (x ₁ ,y ₁ ) is the energy density acting on the point (x ₁ ,y ₁ ) on the free interface of the molten pool during the additive process, x ₁ is the x-axis coordinate of any point on the free interface of the molten pool, y ₁ is the y-axis coordinate of any point on the free interface of the molten pool, P is the energy power acting on the free interface of the molten pool, r ₀ is the energy effective radius of the electron beam, and r is the position from the point (x ₁ ,y ₁ ) to the current center of the heat source.

Step 203, for any moment of the simulation calculation, based on the finite element model, determine the region where the electron beam energy application surface is located at the current moment. The region where the electron beam energy application surface is located includes a plurality of grid units.

In an exemplary embodiment, step 203 includes:

(31) Obtain the starting position of the electron beam additive, the moving speed of the electron beam, and the energy effective radius of the electron beam.

(32) Calculate the center coordinates of the current position of the electron beam energy according to the current time, the starting position of the electron beam additive and the moving speed of the electron beam.

Specifically, the following formula is used to determine the center coordinates of the current position of the electron beam energy:

x _c = x _o + v _x · t;

y _c = _yo + _vy · t;

Among them, ( _xc , _yc , _zo ) are the center coordinates of the current position of the electron beam energy, _xc is the x-axis coordinate of the current position of the electron beam energy, _yc is the y-axis coordinate of the current position of the electron beam energy, t is the current moment, ( _xo , yo, _zo ) is the starting position of the electron beam additive, _xo is the x-axis coordinate of the starting position of the electron beam additive, _yo is the y-axis coordinate of the starting position of the electron beam additive, _zo is the z-axis coordinate of the starting position of the electron beam additive, _vx is the moving speed of the electron beam in the x-axis direction, and _vy is the moving speed of the electron beam in the y-axis direction.

(33) According to the center coordinates ( _xc , _yc , _z0 ) of the current position of the electron beam energy and the energy effective radius _r0 of the electron beam, the region where the electron beam energy application surface is located is determined. The region where the electron beam energy application surface is located is a cylindrical region including the substrate 401, the deposited layer 402 and the powder bed 403, that is, the electron beam energy application region is a cylindrical region with ( _xc , _yc , _z0 ) as the center and _r0 as the radius including the substrate 401, the deposited layer 402 and the powder bed 403.

Step 204, extract the liquid phase volume fraction of each grid cell in the area where the electron beam energy application surface is located at the current moment, and determine all free interface cells in the area where the electron beam energy application surface is located at the current moment based on the liquid phase volume fraction of each grid cell in the area where the electron beam energy application surface is located at the current moment, and obtain a free interface set.

Specifically, for the region where the electron beam energy application surface is located, the liquid volume fraction V _f of each grid unit of the powder particles and the deposition layer 402 is extracted. If the relationship 0.5≤V _f <1.0 is satisfied, the grid unit is a free interface unit, and all free interface units in the electron beam energy application region are obtained in turn to form a free interface set.

Step 205: according to the three-dimensional coordinates of each free interface unit in the free interface set, the pore interface units and the blocked interface units in the free interface set are excluded to obtain the free interface subset to which electron beam energy is applied. The units in the free interface subset to which electron beam energy is applied are energy applied free interfaces.

Specifically, for the free interface set, a vertical (z-axis direction) unit coordinate analysis method is used to determine whether there are pore interfaces and particle-blocked interfaces of the deposition layer 402 (or substrate 401), and exclude them.

In an exemplary embodiment, step 205 includes:

(51) According to the three-dimensional coordinates of each free interface unit in the free interface set, the spatial range of the free interface is determined, that is, the space formed by the minimum x-axis coordinate, the maximum x-axis coordinate, the minimum y-axis coordinate and the maximum y-axis coordinate in the free interface set.

(52) The free interface units in the spatial range where the free interface is located, which have the same x-axis coordinates and y-axis coordinates but different z-axis coordinates, are regarded as a group of mesh units to be excluded.

(53) In the free interface set, each group of to-be-excluded grid cells only retains the to-be-excluded grid cells with the largest z-axis coordinate to obtain a subset of free interfaces to which electron beam energy is applied.

Specifically, as shown in FIG5 and FIG6, when the electron beam 501 is applied to the free interface, if there is a free interface unit with the same x-axis coordinate and y-axis coordinate but different z-axis coordinate within the spatial range where the free interface is located, it is determined that there is a pore interface 601 or a shielded interface 503. In this case, only the grid unit with the largest z-coordinate is retained as the energy application free interface 502. When all the pore interfaces 601 and shielded interfaces 503 in the free interface set are excluded, the energy application free interface 502 can be obtained.

Step 206: Apply the electron beam energy to each unit in the free interface subset to establish a heat source model at the current moment.

Step 207 , performing simulation calculation on the additive process based on the heat source model at the current moment.

In an exemplary embodiment, step 207 includes:

(71) For all free interfaces of the molten pool, the gas evaporation recoil pressure is applied and the calculation formula is:

Among them, _Pr is the gas evaporation recoil pressure, _P0 is the ambient pressure, _Le is the latent heat of material evaporation, T is the free surface temperature of the molten pool, _Te is the boiling point of the material, and R is the ideal gas constant.

(72) The finite volume method is used to simulate the EBSM additive process and obtain the melt pool evolution results, additive surface morphology and real-time evolution results of pore defects in the additive process. Based on the melt pool evolution results, additive surface morphology and real-time evolution results of pore defects in the additive process, the melt pool evolution process, additive surface quality and defect formation mechanism are deeply analyzed to provide theoretical guidance for the optimization and control of additive manufacturing process parameters.

This application is aimed at EBSM additive manufacturing. On the basis of analyzing the characteristics of the heat source and the actual thermal interaction process between the powder bed 403 and the substrate 401, the electron beam energy is calculated based on the actual EBSM additive process, and its energy density is determined to be a Gaussian distribution related to the radius. For any time step in the additive process, the free interface of the powder particles and the molten pool on the deposition layer 402 (or substrate 401) is identified by the volume fraction of the gas-liquid two phases in the CFD model, and all free interfaces in the molten pool area are obtained. Through the interface unit coordinate analysis, it is determined whether there are pore interfaces and the interface of the deposition layer 402 (or substrate 401) blocked by particles, and the pores and blocked free interfaces are excluded to obtain the energy application free interface, and the electron beam energy is applied to the interface, thereby realizing the heat source modeling within the time step of the EBSM additive process. The heat source model does not involve heat source shape restrictions, can be directly applied to the simulation of single-pass, multi-pass and multi-layer selective melting processes, and can be applied to additive processes with conductive and keyhole molten pool formation mechanisms.

Aiming at the actual thermal effects of EBSM additive manufacturing, this application proposes a simulation method for EBSM additive manufacturing that can automatically track the transient energy application free interface. Compared with the existing body heat source model, the heat source model constructed in this application has the following advantages:

1) The existing body heat source model applies heat source in a regular geometric area, while the geometry of the actual molten pool is irregular and changes instantaneously, so the application area of the body heat source model deviates greatly from the actual molten pool area. The present application simplifies the heat source energy into a moving Gaussian surface heat source that is only related to the radius (see step 203), and the heat source application surface can be any curved surface without geometric shape restrictions, so that energy can be effectively applied to the free interface of the molten pool. It can be directly applied to additive processes with both conductive and keyhole molten pool formation mechanisms.

2) The present application can automatically determine the obstruction of the deposited layer 402 (or substrate 401) by pores and particles (see step 205), and can accurately and automatically track the transient energy application free interface, including the free interface between particles and the deposited layer 402 (or substrate 401), which is more in line with the actual thermal effect of the additive process.

3) The present application can automatically track the free interface of the molten pool and apply the heat source to the free interface of geometrically complex particles and the deposition layer 402 (or substrate 401) (see steps 205 to 206), so it can be directly applicable to single-pass, multi-pass and multi-layer multi-pass selective melting without the need for parameter adjustment.

4) Based on the heat source model constructed in steps 202 to 206, EBSM additive manufacturing simulation can obtain more accurate prediction results.

In summary, the electron beam selective melting additive process simulation method provided in this application is more in line with the actual process and has higher prediction accuracy. It provides an important basis for in-depth research on the molten pool evolution process, additive surface quality, defect formation mechanism, etc. in the EBSM additive process, and is helpful for optimizing and controlling the additive manufacturing process parameters.

The present application also provides an application scenario, which applies the above-mentioned electron beam selective melting additive process simulation method. Specifically: The electron beam selective melting additive process simulation method provided in this embodiment can be applied to the optimization and regulation of additive manufacturing process parameters. In the process of optimizing and regulating the additive manufacturing process parameters, the electron beam selective melting additive process simulation method provided in this embodiment is first used to simulate and calculate the additive process, and the molten pool evolution process, the additive surface quality and the defect formation mechanism are deeply analyzed according to the simulation calculation results, and then the additive manufacturing process parameters are optimized.

In an exemplary embodiment, a computer device is provided, which may be a server or a terminal, and its internal structure diagram may be shown in FIG7. The computer device includes a processor, a memory, an input/output interface (Input/Output, referred to as I/O) and a communication interface. Among them, the processor, the memory and the input/output interface are connected through a system bus, and the communication interface is connected to the system bus through the input/output interface. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The database of the computer device is used to store relevant data of electron beam selective melting additive. The input/output interface of the computer device is used to exchange information between the processor and an external device. The communication interface of the computer device is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor, a method for simulating an electron beam selective melting additive process is implemented.

Those skilled in the art will appreciate that the structure shown in FIG. 7 is merely a block diagram of a portion of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. A specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components. In an exemplary embodiment, a computer device is provided, including a memory and a processor, wherein a computer program is stored in the memory, and the processor implements the steps in the above-mentioned method embodiments when executing the computer program.

In an exemplary embodiment, a computer-readable storage medium is provided, storing a computer program, and when the computer program is executed by a processor, the steps in the above method embodiments are implemented.

In an exemplary embodiment, a computer program product is provided, including a computer program, and when the computer program is executed by a processor, the steps in the above method embodiments are implemented.

It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of relevant data must comply with relevant regulations.

Those of ordinary skill in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to the memory, database or other medium used in the embodiments provided in the present application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM may be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM).

The database involved in each embodiment provided in this application may include at least one of a relational database and a non-relational database. The non-relational database may include a distributed database based on blockchain, etc., but is not limited thereto. The processor involved in each embodiment provided in this application may be a general-purpose processor, a central processing unit, a graphics processor, a digital signal processor, a programmable logic device, a data processing logic device based on quantum computing, etc., but is not limited thereto.

The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims (10)

1. A method for simulating an electron beam selective melting additive process, characterized in that the method comprises: Establish a finite element model for electron beam selective melting; Determine the electron beam energy based on the actual additive process of electron beam selective melting; At any moment of the simulation calculation, based on the finite element model, determining the region where the electron beam energy application surface is located at the current moment; the region where the electron beam energy application surface is located includes a plurality of grid units; Extracting the liquid phase volume fraction of each grid unit in the region where the electron beam energy application surface is located at the current moment, and determining all free interface units in the region where the electron beam energy application surface is located at the current moment according to the liquid phase volume fraction of each grid unit in the region where the electron beam energy application surface is located at the current moment, and obtaining a free interface set; According to the three-dimensional coordinates of each free interface unit in the free interface set, the pore interface unit and the blocked interface unit in the free interface set are excluded to obtain a free interface subset to which electron beam energy is applied; wherein the x-axis coordinate and the y-axis coordinate are directions of the additive plane, and the z-axis is the thickness direction; Applying the electron beam energy to each unit in the free interface subset to establish a heat source model at the current moment; The additive process is simulated based on the heat source model at the current moment. 2. The electron beam selective melting additive process simulation method according to claim 1 is characterized in that establishing a finite element model of electron beam selective melting specifically comprises: Establishing a geometric structure model for electron beam selective melting; the geometric structure model includes a substrate, a deposition layer, a powder bed and an approximate vacuum domain; The geometric structure model is meshed, material properties are given, initial temperature, initial liquid phase volume fraction and initial fluid velocity of each mesh unit are set, and boundary conditions are set to obtain a finite element model of electron beam selective melting. 3. The electron beam selective melting additive process simulation method according to claim 1, characterized in that the electron beam energy includes the energy density acting at each point on the free interface of the molten pool during the additive process; The electron beam energy is determined based on the actual additive process of electron beam selective melting, including: Obtain the energy effective radius of the electron beam, the acceleration voltage of the electron beam, the current intensity of the electron beam, and the energy absorption coefficient of the material to the electron beam; The energy power acting on the free interface of the molten pool is calculated based on the acceleration voltage of the electron beam, the current intensity of the electron beam and the energy absorption coefficient of the material to the electron beam; According to the energy power acting on the free interface of the molten pool, the energy effective radius of the electron beam and the position of the current heat source center, the energy density acting at each point on the free interface of the molten pool during the additive process is determined. 4. The electron beam selective melting additive process simulation method according to claim 3, characterized in that the energy density acting on the free interface of the molten pool at the point (x ₁ , y ₁ ) during the additive process is calculated using the following formula: Among them, q _S (x ₁ ,y ₁ ) is the energy density acting on the point (x ₁ ,y ₁ ) on the free interface of the molten pool during the additive process, x ₁ is the x-axis coordinate of any point on the free interface of the molten pool, y ₁ is the y-axis coordinate of any point on the free interface of the molten pool, P is the energy power acting on the free interface of the molten pool, r ₀ is the energy effective radius of the electron beam, and r is the position from the point (x ₁ ,y ₁ ) to the current center of the heat source. 5. The electron beam selective melting additive process simulation method according to claim 1, characterized in that, based on the finite element model, determining the area where the electron beam energy application surface is located at the current moment specifically includes: Obtain the starting position of electron beam additive, the moving speed of the electron beam and the energy effective radius of the electron beam; Calculate the center coordinates of the current position of the electron beam energy according to the current time, the starting position of the electron beam material addition and the moving speed of the electron beam; The area where the electron beam energy application surface is located is determined according to the central coordinates of the current position of the electron beam energy and the energy effective radius of the electron beam; the area where the electron beam energy application surface is located is a cylindrical area including the substrate, the deposition layer and the powder bed. 6. The electron beam selective melting additive process simulation method according to claim 5, characterized in that the center coordinates of the current position of the electron beam energy are determined by using the following formula: x _c = x _o + v _x · t; y _c = _yo + _vy · t; Among them, ( _xc , _yc , _zo ) are the center coordinates of the current position of the electron beam energy, _xc is the x-axis coordinate of the current position of the electron beam energy, _yc is the y-axis coordinate of the current position of the electron beam energy, t is the current moment, ( _xo , _yo , _zo ) is the starting position of electron beam additive, _xo is the x-axis coordinate of the starting position of electron beam additive, _yo is the y-axis coordinate of the starting position of electron beam additive, _zo is the z-axis coordinate of the starting position of electron beam additive, _vx is the moving speed of the electron beam in the x-axis direction, and _vy is the moving speed of the electron beam in the y-axis direction. 7. The electron beam selective melting additive process simulation method according to claim 1 is characterized in that, according to the liquid volume fraction of each grid unit in the area where the electron beam energy application surface is located at the current moment, all free interface units in the area where the electron beam energy application surface is located at the current moment are determined to obtain a free interface set, which specifically includes: For any grid cell in the region where the electron beam energy application surface is located at the current moment, if the liquid phase volume fraction of the grid cell satisfies the relationship 0.5≤V _f ＜1.0, then the grid cell is a free interface cell; the free interface concentration includes all free interface cells in the region where the electron beam energy application surface is located; wherein V _f is the liquid phase volume fraction of the grid cell. 8. The electron beam selective melting additive process simulation method according to claim 1, characterized in that, according to the three-dimensional coordinates of each free interface unit in the free interface set, the pore interface unit and the blocked interface unit in the free interface set are excluded to obtain the free interface subset to which the electron beam energy is applied, specifically comprising: Determining the spatial range of the free interface according to the three-dimensional coordinates of each free interface unit in the free interface set; The free interface units within the spatial range where the free interface is located, which have the same x-axis coordinates and y-axis coordinates but different z-axis coordinates, are regarded as a group of mesh units to be excluded; In the free interface set, each group of to-be-excluded grid cells only retains the to-be-excluded grid cells with the largest z-axis coordinate, so as to obtain a free interface subset to which electron beam energy is applied. 9. A computer device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the electron beam selective melting additive process simulation method according to any one of claims 1 to 8. 10. A computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the method for simulating an electron beam selective melting additive process according to any one of claims 1 to 8 is implemented.