Laser coaxial powder feeding multilayer deposition contour rapid prediction method

Abstract

The invention relates to the technical field of metal additive manufacturing, in particular to a laser coaxial powder feeding multilayer deposition contour rapid prediction method. The method comprises the following steps: acquiring spatial distribution of powder concentration; obtaining laser intensity distribution after powder shielding by utilizing the spatial distribution; obtaining a substrate temperature field according to the laser intensity distribution; obtaining a contact angle and a sectional area of a deposition layer through the substrate temperature field; based on the contact angle and the cross-sectional area, constructing a prediction model of the single-channel single-layer deposition contour; according to the prediction model, a single-channel multi-layer deposition contour is obtained; and according to the single-channel multi-layer deposition contour, rapid prediction of the laser coaxial powder feeding multi-layer deposition layer contour is realized. According to the method, the component surface topography prediction efficiency under different process parameter combinations is greatly improved, the problems of complex experimental process and high cost are effectively solved, and the problems of high spatial resolution, large calculation scale and high time cost of numerical simulation are also solved.

Description

Technical Field

[0001] The invention relates to the technical field of metal additive manufacturing, and in particular to a method for quickly predicting a multi-layer deposition profile using laser coaxial powder feeding. Background Art

[0002] Laser coaxial powder feeding is an important technology in metal additive manufacturing. This technology uses a gas-carrying powder feeder to transport metal powder and delivers the powder flow into the light spot to achieve line-by-line and layer-by-layer deposition forming. It has broad application prospects in the additive manufacturing of large components and the composite and gradient component manufacturing of multiple materials on the same material. However, laser coaxial powder feeding technology still faces many challenges in engineering applications, especially in surface forming quality control. There are still common surface defects such as uneven top surface of components, dimensional deviation, rough side wall, unmelted powder adhesion, and side wall stacking corrugations, which lead to large cutting allowances in subsequent finishing and make it difficult to achieve true "near-net" forming.

[0003] In the prior art, experimental methods or numerical simulation methods are usually used to study the surface forming quality. On the one hand, obtaining forming quality characterization data through experiments is the most direct way, but it is limited by the detection means and experimental costs, and it is difficult to meet the research needs under a large number of process parameter combinations. On the other hand, to study the surface forming quality through numerical simulation, it is necessary to establish a high-fidelity model to describe subtle defects, but due to its high spatial resolution and large calculation scale, the calculation time of a single case is usually more than tens of hours, which is difficult to meet the needs of efficient prediction; in addition, theoretical or analytical models can directly reflect the physical meaning, but due to the complexity of physical problems, it is difficult to accurately describe complex physical phenomena. Therefore, it is urgent to establish an efficient, accurate and physically meaningful prediction method to achieve rapid mapping of process parameters and component surface contours.

[0004] At present, there is not much research on the profile of multi-layer deposition using laser coaxial powder feeding, and there is no specific method for predicting the profile of multi-layer deposition using laser coaxial powder feeding with low cost, high accuracy and high efficiency. Summary of the invention

[0005] In view of the defects in the prior art, the present invention provides a method for quickly predicting the profile of multi-layer deposition by laser coaxial powder feeding.

[0006] The method for rapid prediction of laser coaxial powder feeding multi-layer deposition profile provided by the present invention comprises the following steps: Obtain the spatial distribution of powder concentration; obtain the laser intensity distribution after powder shielding by using the spatial distribution; obtain the substrate temperature field according to the laser intensity distribution; obtain the contact angle and cross-sectional area of ​​the deposited layer through the substrate temperature field; construct a prediction model of a single-channel single-layer deposition profile based on the contact angle and the cross-sectional area; obtain a single-channel multi-layer deposition profile according to the prediction model; and realize the rapid prediction of the profile of the multi-layer deposition layer of laser coaxial powder feeding according to the single-channel multi-layer deposition profile. The present invention greatly improves the efficiency of component surface morphology prediction under different process parameter combinations, reduces the trial and error costs of a large number of experiments, generates excellent economic benefits, and shortens the calculation time of high-fidelity numerical simulation from "days" to "seconds", making it possible to predict the surface forming quality in real time, effectively solving the problem of complex process and high cost of obtaining the deposited layer profile through experiments, and also solving the problem of high spatial resolution, large calculation scale and low efficiency of solving the deposited layer profile through numerical simulation.

[0007] Optionally, obtaining the spatial distribution of the powder concentration includes: obtaining the spatial distribution of the powder concentration in the front waist area, the waist area and the back waist area, the spatial distribution includes an annular Gaussian distribution in the front waist area, a circular Gaussian distribution in the waist area and a divergent distribution in the back waist area, and the spatial distribution satisfies the following expression: in, is the powder concentration in the space, is the powder concentration in the plane, , is the distribution radius of the powder on the horizontal plane in different areas, is the horizontal distance from the center of the powder flow to the center line, is the area boundary distance of the powder flow, is the distance to the focal plane, is the spatial radial coordinate, is the spatial azimuth, is the space height, The present invention clearly depicts the distribution characteristics of powder concentration in the front, back and center parts of the waist area through the spatial distribution expression of powder concentration, which not only effectively reflects the distribution characteristics of powder concentration in different areas, but also provides important clues for understanding the spatial distribution law of powder.

[0008] Optionally, the using the spatial distribution to obtain the laser intensity distribution after powder shielding includes: using the spatial distribution and the surface heat source Gaussian intensity distribution to obtain the laser intensity distribution after powder shielding, and the laser intensity distribution satisfies the following expression: in, is the intensity distribution after laser attenuation, is the Gaussian intensity distribution of the surface heat source, is the powder concentration in the space, is the powder radius, is the ordinate coordinate of the initial contact point between the laser and the powder flow, is the spatial radial coordinate, is the spatial azimuth, The present invention constructs an expression for the laser intensity distribution after powder shielding through the spatial distribution of powder concentration and the Gaussian intensity distribution of the surface heat source. It not only takes into account the inhomogeneity of powder concentration in space, but also takes into account the intensity distribution characteristics of the laser source itself, so that the laser intensity distribution after powder shielding can be obtained more accurately, which is of great significance in scientific research and industrial applications.

[0009] Optionally, the method of obtaining the substrate temperature field according to the laser intensity distribution includes: establishing an analytical model of the substrate temperature field under a moving Gaussian heat source according to the laser intensity distribution; obtaining the substrate upper surface temperature through the analytical model; obtaining the substrate upper surface heat loss power according to the substrate upper surface temperature; and obtaining the substrate temperature field based on the substrate upper surface heat loss power and the analytical solution of the analytical model. The present invention describes the complete process of deriving the substrate temperature field from the laser intensity distribution. The specific effects are as follows: First, an analytical model of the substrate temperature field under a moving Gaussian heat source is established using the laser intensity distribution, which provides a basis for subsequent calculations; second, the temperature of the substrate upper surface is calculated through the analytical model, and an important indicator for evaluating the laser thermal effect is obtained; third, the heat loss power of the substrate upper surface is derived based on the temperature of the substrate upper surface, which reflects the heat loss on the substrate upper surface; fourth, the substrate temperature field is obtained through the upper surface heat loss power and the analytical solution of the analytical model, realizing the accurate mapping from laser intensity to substrate temperature field.

[0010] Optionally, the temperature increment of the substrate temperature field satisfies the following expression: in, is the temperature increment, is the laser power, is the heat loss power on the substrate surface, is the standard deviation of laser intensity, is the absorption rate, is the material density, is the gravity state value, is the specific heat of the material, is the thermal conductivity of the material, is the laser moving speed, is the moving time step, is the reference time step, , , is a spatial coordinate point. The present invention constructs a temperature increment expression for the substrate temperature field by considering the heat loss power on the upper surface of the substrate, which is used to describe the dynamic changes of the substrate temperature field. This expression has the following effects: First, it not only takes the heat loss power on the upper surface of the substrate into consideration as a key parameter, but also reflects how the substrate temperature is adjusted with the change of heat loss during the laser processing process, and can more accurately analyze the thermal effect of the interaction between the laser and the substrate, including key links such as heat absorption, conduction and dissipation; second, it provides a theoretical basis for accurately controlling the temperature distribution during laser processing, helps to optimize process parameters, reduce thermal deformation and thermal stress, thereby improving processing quality and efficiency, and is of great significance in high-precision processing fields such as laser cutting, welding, and cladding.

[0011] Optionally, obtaining the contact angle and cross-sectional area of ​​the deposited layer through the substrate temperature field includes: obtaining the molten pool size through the substrate temperature field; obtaining the powder utilization rate and the contact angle of the deposited layer based on the molten pool size; and obtaining the cross-sectional area of ​​the deposited layer based on the powder utilization rate. The present invention accurately derives the key characteristics of the deposited layer through the substrate temperature field. The specific effects are as follows: First, the molten pool size is accurately measured by using the distribution information of the substrate temperature field. The molten pool size not only reflects the efficiency of the melting process, but also directly affects the formation of the subsequent deposited layer; second, based on the molten pool size, the powder utilization rate that measures the material utilization efficiency and the contact angle of the deposited layer that reveals the bonding state between the deposited layer and the substrate are calculated, which is crucial to ensuring the stability and strength of the deposited layer; third, the powder utilization rate is used to deduce the cross-sectional area of ​​the deposited layer. The cross-sectional area reflects the morphology and size of the deposited layer, which has important reference value for evaluating the deposition effect and subsequent processing.

[0012] Optionally, constructing a prediction model for a single-channel single-layer deposition profile based on the contact angle and the cross-sectional area includes: constructing a prediction model for a single-channel single-layer deposition profile based on the contact angle, the cross-sectional area and the Young-Laplace equation, wherein the Young-Laplace equation satisfies the following expression: in, is the surface tension coefficient, is the contour curvature, is the pressure difference between the gas and liquid surfaces. The single-channel single-layer deposition profile prediction model constructed by the present invention makes full use of the three key elements of contact angle, cross-sectional area and Young-Laplace equation. The specific effects are as follows: First, the contact angle, as an important indicator of the interface characteristics between the deposited layer and the substrate, provides the model with key information about the expansion trend of the deposited layer; second, the cross-sectional area directly reflects the morphology and size of the deposited layer, and becomes an indispensable data for predicting the deposition profile; third, the introduced Young-Laplace equation describes the relationship between the liquid interface curvature and the interfacial tension. Combined with the contact angle and cross-sectional area, it can more accurately describe the expansion and morphological changes of the deposited layer on the substrate.

[0013] Optionally, the prediction model of the single-pass single-layer deposition profile satisfies the following expression: in, is the surface tension coefficient, is the first-order derivative of the distance between the profile curve and the central axis, is the second-order derivative of the distance between the contour curve and the central axis, is the coefficient, is the gravity state value, is the material density, is the single-channel single-layer deposition profile, is the volume fraction of liquid metal. The prediction model constructed by the present invention is an advanced expression that integrates scientificity, practicality and accuracy. It cleverly integrates the physical principle of the Young-Laplace equation, thereby ensuring the accuracy and reliability of the prediction results. It not only provides strong support for the optimization of the deposition process, but also injects new vitality into the research and development of related fields.

[0014] Optionally, obtaining a single-channel multi-layer deposition profile according to the prediction model includes: obtaining a single-channel single-layer deposition profile according to the prediction model; and performing profile processing on the single-channel single-layer deposition profile using a profile construction method to obtain a single-channel multi-layer deposition profile. The present invention obtains a single-channel multi-layer deposition profile through a prediction model of a single-channel single-layer deposition profile; the entire process embodies the advancement and practicality of the technology; the profile processing method not only improves the accuracy and reliability of the deposition profile, but also provides richer and more accurate technical support for subsequent analysis and research.

[0015] Optionally, the contour construction method includes a direct stacking construction method and an indirect stacking construction method of the contour; the direct stacking construction method includes a construction method in which multiple single-layer deposited layer cross-sections are directly stacked after considering the melting area; the indirect stacking construction method includes a construction method in which multiple single-layer deposited layer cross-sections are first superimposed on the cross-sectional area and then stacked. The present invention describes the direct stacking construction method and the indirect stacking construction method in the contour construction method; the direct stacking construction method emphasizes the direct superposition of the cross-sectional area of ​​each single-layer deposited layer after considering the melting area, which can be closer to the fusion bonding between layers in the actual deposition process, thereby improving the construction accuracy; the indirect stacking construction method first superimposes the cross-sectional areas of multiple single-layer deposited layers and then stacks them, which takes more consideration of the interaction between the deposited layers and the overall structural stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a flow chart of a method for rapid prediction of a multi-layer deposition profile of laser coaxial powder feeding according to an embodiment of the present invention; Figure 2 A flowchart of performing calculations according to an embodiment of the present invention; Figure 3 This is a process schematic diagram of laser coaxial powder feeding according to an embodiment of the present invention; Figure 4 A schematic diagram of the geometrical profile of a nozzle and a powder flow thereunder according to an embodiment of the present invention; Figure 5 This is a schematic diagram of laser shielding by powder in a microelement according to an embodiment of the present invention; Figure 6 This is a flow chart of heat loss power calculation according to an embodiment of the present invention; Figure 7 A top view of the laser coaxial powder feeding process according to an embodiment of the present invention; Figure 8 This is a schematic diagram of a laser coaxial powder feeding model according to an embodiment of the present invention; Fig. 9 A schematic cross-sectional view of a cladding layer according to an embodiment of the present invention; Fig.10 A single-pass single-layer deposition profile calculation flow chart of an embodiment of the present invention; Fig.11 A schematic cross-sectional view of a single-pass multi-layer deposition according to an embodiment of the present invention; Fig.12 Schematic diagram of single-pass multi-layer deposition according to an embodiment of the present invention. DETAILED DESCRIPTION

[0017] The specific embodiments of the present invention will be described in detail below. It should be noted that the embodiments described herein are only for illustration and are not intended to limit the present invention. In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present invention. However, it is obvious to those of ordinary skill in the art that these specific details do not need to be adopted to implement the present invention. In other examples, in order to avoid confusing the present invention, known circuits, software or methods are not specifically described.

[0018] Throughout the specification, references to "one embodiment," "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in conjunction with the embodiment or example is included in at least one embodiment of the present invention. Therefore, the phrases "in one embodiment," "in an embodiment," "an example," or "an example" appearing in various places throughout the specification do not necessarily all refer to the same embodiment or example. In addition, particular features, structures, or characteristics may be combined in one or more embodiments or examples in any suitable combination and / or subcombination. In addition, it should be understood by those of ordinary skill in the art that the figures provided herein are for illustrative purposes and that the figures are not necessarily drawn to scale.

[0019] See also Figure 1 , an embodiment of the present invention provides a method for quickly predicting the profile of a multi-layer deposition by laser coaxial powder feeding, the method comprising the following steps: S1. Obtain the spatial distribution of powder concentration.

[0020] In one embodiment, based on the laser coaxial powder feeding process, the nozzle parameters and the powder spatial distribution parameters are measured. The laser coaxial powder feeding process is as follows: Figure 2 As shown, the laser beam is at a processing speed Yanzheng The coordinate origin is fixed at the center of the laser beam spot on the substrate. The distance between the coaxial powder feeding nozzle and the substrate plane is The laser beam passes through the central cavity of the nozzle, and the powder particles are transported in a conical annular channel coaxial with the laser beam. On any vertical symmetry plane, the geometric profile of the nozzle and the powder flow below it is as follows: Figure 3 shown.

[0021] Furthermore, on the nozzle outlet plane, with the origin A coordinate system is established for the nozzle center The angle of the annular channel relative to the center line (Z axis) is The powder flow usually diverges to a certain extent at the nozzle outlet, with the upper and lower divergence angles being and The powder particles ejected from the annular outlet flow downward, and the laser beam and powder flow After the points interact with each other, the powder flow undergoes a process of first convergence and then divergence.

[0022] Furthermore, according to the distribution characteristics of the powder on the horizontal cross-section at different positions, the powder flow is roughly divided into three regions: the front waist area of ​​the annular Gaussian distribution, the waist area of ​​the circular Gaussian distribution, and the back waist area of ​​the divergent distribution. The analytical expression of the spatial distribution of powder concentration is: in, is the powder concentration in the space, is the powder concentration in the plane, , is the distribution radius of the powder on the horizontal plane in different areas, is the horizontal distance from the center of the powder flow to the center line, is the area boundary distance of the powder flow, is the distance to the focal plane, is the spatial radial coordinate, is the spatial azimuth, is the space height, is the distribution of powder concentration in the transverse plane. Satisfies the following expression: It should be noted that the distribution of powder concentration in the transverse plane is represented by the brightness distribution of the powder flow. According to Mie theory, the brightness of the powder flow is proportional to the powder concentration. Therefore, the brightness distribution in the front view image of the powder flow captured reflects the distribution of the powder flow concentration, that is, the greater the brightness, the greater the concentration; the smaller the brightness, the smaller the concentration.

[0023] Furthermore, the image is converted into a grayscale image by image processing software, and the brightness of the powder flow is converted into grayscale intensity.

[0024] Further, according to the grayscale images at different positions and The concentration distribution was fitted and the analytical solution was obtained.

[0025] S2. Using the spatial distribution, obtain the laser intensity distribution after powder shielding.

[0026] In one embodiment, the laser intensity distribution after powder shielding is studied based on the spatial distribution of the powder flow and the attenuation effect of the powder on the laser intensity.

[0027] Specifically, in this embodiment, a Gaussian distributed surface heat source is used, and its intensity distribution Satisfies the following expression: in, is the laser power, is the laser spot radius, is the distance from the laser center to the desired point. The attenuation of the laser power intensity by the powder flow can be calculated according to the intensity distribution expression of the Gaussian distribution surface heat source above, as Figure 4 As shown, the selected area is , height is The attenuation coefficient The laser intensity in the microelement The following relations are satisfied: in, is the shaded area of ​​the powder, which can be expressed as: in, is the powder radius.

[0028] Furthermore, the attenuation coefficient Satisfies the following expression: Further, the above formula is in the interval Therefore, the total attenuation of laser intensity is It can be expressed as: in, Initial contact between laser and powder flow The vertical coordinate of the point, such as Figure 4 As shown. Intensity distribution after laser attenuation It can be solved by the following formula: in, is the intensity distribution after laser attenuation, is the Gaussian intensity distribution of the surface heat source, is the powder concentration in the space, is the powder radius, is the spatial radial coordinate, is the spatial azimuth, The height of the space.

[0029] S3. Obtaining the substrate temperature field according to the laser intensity distribution.

[0030] Wherein, step S3 further comprises the following steps: S31. According to the laser intensity distribution, an analytical model of the substrate temperature field under the moving Gaussian heat source is established.

[0031] In one embodiment, the process of establishing an analytical model of the substrate temperature field under a moving Gaussian heat source is as follows: First, in the solid domain, without considering the convection in the molten pool, the heat transfer equation can be written as: in, is the temperature, is the material density, is the material specific heat, is the thermal conductivity of the material, Laser heat source. is the source term introduced by the material phase change and can be expressed as: in, is the density of the metal material, is the latent heat of melting of metal materials, is the volume fraction of liquid metal, which can be expressed as: in, is the solidus and liquidus temperature of the material, and the inverse tangent function can be introduced to approximate , which is expressed as follows: in, It is obtained by fitting and then The derivative is expressed as: Further, Defined as: Furthermore, the heat transfer equation is rearranged as: It should be noted that the laser intensity distribution represents The laser beam interacts with the powder, the powder temperature is increased, and the laser intensity is attenuated by the powder flow. The total attenuation can be divided into the sum of powder absorption and scattering. In the laser coaxial powder feeding process, since the size of the powder is much larger than the laser wavelength, the scattering phenomenon can be ignored, and most of the attenuated laser energy is absorbed by the powder.

[0032] Furthermore, the Green's function method is used to integrate the entire interval and obtain the analytical solution of the instantaneous point heat source.

[0033] Specifically, by superimposing instantaneous Gaussian surface heat sources in a continuous order and at a certain distance, the temperature response expression of the moving Gaussian surface heat source moving on the surface of a semi-infinite medium is obtained. , the speed is ,along Axis movement, absorption rate , and its temperature increment analytical solution is: in, is the standard deviation of laser intensity. When the time is very short, it is assumed is a constant, so we can get: in, is the temperature increment, is the laser power, is the absorption rate, is the material density, is the gravity state value, is the specific heat of the material, is the thermal conductivity of the material, is the moving time step, is the reference time step, , , is the spatial coordinate point.

[0034] S32. Obtain the upper surface temperature of the substrate through the analytical model.

[0035] In one embodiment, the material properties are considered to vary with temperature and The impact of time Divide into multiple time steps, the time interval is , calculate the temperature field after each time step to update the material properties and , therefore, the relationship satisfied by the surface temperature of the substrate is as follows: in, It represents the surface temperature of the substrate and can be solved by the temperature increment analytical expression , material parameters are taken Material properties at temperature and Temperature increment at a point .

[0036] S33. Obtain the heat loss power on the upper surface of the substrate based on the upper surface temperature of the substrate.

[0037] In one embodiment, the heat loss is equivalent to the power loss on the upper surface of the substrate, that is, the heat loss power , which satisfies the following relationship: in, is the ambient temperature, is the convective heat transfer coefficient, is the Stefan-Boltzmann constant, is the emissivity, is the latent heat of vaporization of the material, is the molar mass of the molecule, is the atmospheric pressure, is the universal gas constant, is the upper surface area of ​​the substrate.

[0038] S34. Obtain the substrate temperature field based on the heat loss power on the substrate surface and the analytical solution of the analytical model.

[0039] In one embodiment, considering the heat loss power and combining the expression of the temperature increment analytical solution, the final temperature increment can be obtained, and its expression is as follows: Furthermore, to determine the , taking an iterative approach to find the appropriate , the process is as follows Figure 5 The power considering heat loss is updated at each time step, and the temperature field is solved through the temperature field analytical model.

[0040] S4. Obtain the contact angle and cross-sectional area of ​​the deposited layer through the substrate temperature field.

[0041] Wherein, step S4 further comprises the following steps: S41. Obtain the molten pool size through the substrate temperature field.

[0042] In one embodiment, the projection of the molten pool on the substrate surface is approximated by the solid-liquid line, such as Figure 6 As shown. Among them, points A, B, C, and D are located on the boundary of the molten pool. According to the expression of the temperature increment analytical solution, we can get: Furthermore, the molten pool boundary can be approximated as two semi-ellipses, and the solidus can be expressed as: S42. Based on the molten pool size, obtain the powder utilization rate and the contact angle of the deposited layer.

[0043] In one embodiment, according to the expression of the powder shadow area, it is determined that only the powder entering the molten pool is utilized, the molten pool is divided into two semi-ellipses with the center of the heat source as the boundary point, the powder concentration at each position is calculated according to the spatial distribution expression of the powder concentration, and the spatial distribution expression of the powder concentration is integrated on the two semi-ellipsoidal surfaces to obtain the utilization rate of the powder, and the utilization rate of the powder satisfies the following expression: in, The molten pool area.

[0044] Furthermore, the contact angle of the deposited layer is calculated according to the expression of the molten pool boundary line. The expression of the contact angle is as follows: S43. Obtain the cross-sectional area of ​​the deposited layer according to the powder utilization rate.

[0045] In one embodiment, the area of ​​the cross section of the deposited layer is calculated according to the scanning speed, the powder feeding rate and the powder utilization rate, and the area of ​​the cross section of the deposited layer satisfies the following expression: in, is the powder feeding rate.

[0046] S5. Based on the contact angle and the cross-sectional area, a prediction model for a single-channel single-layer deposition profile is constructed.

[0047] In one embodiment, the Young-Laplace equation is first used to describe the surface tension of the deposited layer. The Young-Laplace equation is as follows: in, is the surface tension coefficient, is the contour curvature, is the pressure difference between the gas and liquid surfaces. Based on the assumption that the radius of curvature of the sedimentary layer surface along the Y axis is infinite, its curvature is: Among them, 𝑅 is the radius of the contour curve from the central axis, where They are The first and second order derivatives of It is the single-channel single-layer deposition profile.

[0048] Furthermore, in order to simplify the modeling process, the fluid momentum equation is written as follows under the consideration of the steady flow of the sediment layer: Where 𝜌 is the density and 𝑔 is the gravity state value. Assume that the pressure at the top of the radius is , the fluid momentum equation can be written as: in, is a coefficient related to the top curvature of the profile and the height of the sediment layer. According to the profile curvature and the fluid momentum equation, the sediment layer profile equation is substituted into the Young-Laplace equation. The sediment layer profile equation is as follows: Furthermore, to avoid the singularity of the equation, it is assumed that the sedimentary layer profile at a short distance from the top is a parabola, and its expression is: in, is the coefficient.

[0049] Further, according to the above parabolic expression and sedimentary layer profile equation, and taking When , we get: Furthermore, the sedimentary layer profile equation is sorted out to obtain a prediction model for a single-channel single-layer sedimentary profile, and the prediction model satisfies the following expression: in, is the surface tension coefficient, is the first-order derivative of the distance between the profile curve and the central axis, is the second-order derivative of the distance between the contour curve and the central axis, is the coefficient, is the gravity state value, is the material density, is the single-channel single-layer deposition profile, is the volume fraction of liquid metal.

[0050] It should be noted that the laser coaxial powder feeding process is as follows Figure 7 As shown in Figure 1, the shape of liquid metal is mainly affected by surface tension, gravity and pressure. In order to describe the shape of the deposited layer during processing, the following assumptions are made: the metal is liquid before the force reaches equilibrium; the deposited layer is symmetrically distributed, and the surface of the deposited layer is The radius of curvature of the axis is infinite; the Marangoni effect mainly acts in the tangential direction, so its effect on the surface of the sediment layer is indirectly exerted by affecting the flow velocity, which is ignored here.

[0051] S6. Based on the prediction model, a single-channel single-layer deposition profile is obtained.

[0052] Wherein, step S6 further comprises the following steps: S61. Based on the prediction model, a single-channel multi-layer deposition profile is obtained.

[0053] In one embodiment, based on the prediction model of single-pass single-layer deposition profile, a particle swarm optimization algorithm is used to obtain and First, a high-fidelity numerical model is used to calculate the contact angle The surface tension coefficient is considered as a constant.

[0054] Furthermore, for the calibrated theoretical model, the unknown sedimentary layer height is obtained by the fourth-order Runge-Kutta algorithm. and coefficient , the calculated contour area and contact angle Compared with the known values, the optimal solution is obtained through the particle swarm optimization algorithm. It usually takes only 0.1s to quickly calculate the single-pass single-layer deposition profile curve under specific working conditions. The process is as follows: Fig. 9 shown.

[0055] S62. Performing profile processing on the single-channel single-layer deposition profile using a profile construction method to obtain a single-channel multi-layer deposition profile.

[0056] For multi-layer deposition, that is, along the same path and in the same direction, the laser print head is raised to a certain height before each deposition, so as to obtain a thin-walled workpiece. The processing process is simplified, such as Fig.10 As shown, points M and N are the two end points of the deposition layer respectively. Assuming that the width and cross-sectional area of ​​each deposition layer remain unchanged, the following two situations will occur during the processing: first, the maximum width of the surface profile of the first deposition layer exceeds the bottom width of the deposition layer; second, the maximum width of the surface profile of the first deposition layer is the bottom width.

[0057] When the first situation is encountered, in one embodiment, a single-channel multi-layer profile is constructed by a direct stacking construction method; the direct stacking construction method includes a construction method in which multiple single-layer deposition layer sections are directly stacked after considering the melting area.

[0058] Specifically, the first layer of the deposition profile and the and Point coordinates.

[0059] Further, determine the endpoint coordinates of the next layer, the endpoint and Point coordinates The coordinates remain unchanged. The coordinates take the maximum value of the contour of this layer, and the cross-sectional area of ​​the next layer . It is based on the contour of the previous deposition layer and the powder utilization efficiency on the new plane after the laser head is lifted to a certain height, such as Fig.11 As shown, that is: in, For the The secondary deposition raises the molten area to different heights. The molten shape is assumed to be the same as the initial molten pool shape. The geometric contour of the next layer is determined according to the endpoint coordinates, cross-sectional area and the same single-pass single-layer deposition contour geometric prediction method to solve the multi-layer contour.

[0060] When encountering the second situation, in another embodiment, an indirect stacking construction method of first superimposing and then stacking is adopted to construct a single-channel multi-layer profile; the indirect stacking construction method includes a construction method of first superimposing the cross-sectional area of ​​multiple single-layer deposition layer sections and then stacking them.

[0061] Specifically, according to the prediction model of single-channel single-layer deposition profile, the first deposition layer profile and point, Point coordinates; Furthermore, keep the second layer endpoints and The coordinates remain unchanged, and the cross-sectional area of ​​the second layer is solved based on the powder utilization efficiency considering the melting area. , , the second layer profile is determined by the single-pass single-layer deposition profile geometry prediction method, and so on. When constructing the layer-by-layer sedimentation profile, , if at this time The maximum width of the contour of the layer is no longer the width of the contour endpoint. Then the solution method of the first case is used to obtain the contours of the multiple layers.

[0062] S7. Based on the single-pass single-layer deposition profile, a rapid prediction of the laser coaxial powder feeding multi-layer deposition profile is achieved.

[0063] In one embodiment, according to the single-pass single-layer deposition profile, an optimization process of the profile curve is performed. The steps of the optimization process are as follows: Firstly, the prediction model of the single-pass single-layer deposition profile in the single-pass multi-layer deposition is trained by using the historical data of the equipment parameters and the process parameters to obtain the optimized prediction model of the single-pass single-layer deposition profile; Further, according to the optimization prediction model, an optimized single-pass single-layer deposition profile is obtained; Further, according to the optimized single-pass single-layer deposition profile, a direct stacking construction method or an indirect stacking construction method is used to obtain an optimized single-pass multilayer deposition profile, such as Fig.12 As shown; Furthermore, the optimized single-pass multi-layer deposition profile is used to quickly predict the laser coaxial powder feeding multi-layer deposition profile.

[0064] In summary, the surface profile efficient prediction model established by the present invention greatly improves the prediction efficiency of component surface morphology under different process parameter combinations, reduces the trial and error cost of a large number of experiments, produces excellent economic benefits, and shortens the calculation time of high-fidelity numerical simulation from "days" to "seconds", making it possible to predict the surface forming quality in real time. The present invention first derives physical quantities such as the spatial distribution position of powder during coaxial powder feeding based on geometric relationships. At the same time, based on parameters such as powder volume fraction, a theoretical model considering the laser shielding effect is established to correct the heat source power model. Subsequently, based on the above-mentioned heat source model, the influence of heat loss and phase change is considered on the basis of the Eagar-Tsai model to achieve the prediction of the spatial distribution of the temperature field. Furthermore, based on the spatial distribution of the temperature field, the melting size and morphology are obtained. According to the relationship between the conservation of mass and the conservation of momentum of the fluid, the area of ​​the cross section of the cladding layer is preliminarily determined. Since the morphology is affected by the surface tension of the liquid metal, the Young-Laplace equation is used to describe it to obtain the equilibrium relationship between the surface tension and the pressure difference. On this basis, according to the relationship between conservation of mass and momentum, a semi-analytical solution of the geometric configuration stacked in the multi-layer scanning process is further established, and finally an efficient prediction model for surface forming quality is established to achieve rapid and accurate prediction of the contours of components using laser coaxial powder feeding technology, forming a relatively rich mapping relationship map between process parameters and deposited layer contours, which strongly supports the research on optimization of the "shape control" process parameters of laser coaxial powder feeding.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and specification of the present invention.

Claims

1. A method for rapid prediction of laser coaxial powder feeding multi-layer deposition profile, characterized in that: The method comprises the following steps: Obtain the spatial distribution of powder concentration; Using the spatial distribution, obtaining the laser intensity distribution after powder shielding; According to the laser intensity distribution, a substrate temperature field is obtained; Obtaining the contact angle and cross-sectional area of ​​the deposited layer through the substrate temperature field; constructing a prediction model of a single-pass single-layer deposition profile based on the contact angle and the cross-sectional area; According to the prediction model, a single-pass multi-layer deposition profile is obtained; According to the single-pass multi-layer deposition profile, a rapid prediction of the laser coaxial powder feeding multi-layer deposition profile is achieved.

2. The method for rapid prediction of laser coaxial powder feeding multi-layer deposition profile according to claim 1 is characterized in that: The obtaining of the spatial distribution of powder concentration comprises: The spatial distribution of powder concentration in the front waist region, waist region and back waist region is obtained, wherein the spatial distribution includes an annular Gaussian distribution in the front waist region, a circular Gaussian distribution in the waist region and a divergent distribution in the back waist region, and the spatial distribution satisfies the following expression: in, is the powder concentration in the space, is the powder concentration in the plane, , is the distribution radius of the powder on the horizontal plane in different areas, is the horizontal distance from the center of the powder flow to the center line, is the area boundary distance of the powder flow, is the distance to the focal plane, is the spatial radial coordinate, is the spatial azimuth, is the space height, is the distribution of powder concentration in the transverse plane.

3. The method for rapid prediction of laser coaxial powder feeding multi-layer deposition profile according to claim 1 is characterized in that: The method of obtaining the laser intensity distribution after powder shielding by utilizing the spatial distribution comprises: The laser intensity distribution after powder shielding is obtained by using the spatial distribution and the Gaussian intensity distribution of the surface heat source. The laser intensity distribution satisfies the following expression: in, is the intensity distribution after laser attenuation, is the Gaussian intensity distribution of the surface heat source, is the powder concentration in the space, is the powder radius, is the ordinate coordinate of the initial contact point between the laser and the powder flow, is the spatial radial coordinate, is the spatial azimuth, The height of the space.

4. The method for rapid prediction of laser coaxial powder feeding multi-layer deposition profile according to claim 1 is characterized in that: The obtaining of the substrate temperature field according to the laser intensity distribution comprises: According to the laser intensity distribution, an analytical model of the substrate temperature field under a moving Gaussian heat source is established; Obtaining the upper surface temperature of the substrate through the analytical model; Obtaining heat loss power on the upper surface of the substrate according to the upper surface temperature of the substrate; Based on the heat loss power on the upper surface of the substrate and the analytical solution of the analytical model, a substrate temperature field is obtained.

5. The method for rapid prediction of laser coaxial powder feeding multi-layer deposition profile according to claim 4 is characterized in that: The temperature increment of the substrate temperature field satisfies the following expression: in, is the temperature increment, is the laser power, is the heat loss power on the substrate surface, is the standard deviation of laser intensity, is the absorption rate, is the material density, is the gravity state value, is the material specific heat, is the thermal conductivity of the material, is the laser moving speed, is the moving time step, is the reference time step, , , is the spatial coordinate point.

6. The method for rapid prediction of laser coaxial powder feeding multi-layer deposition profile according to claim 1 is characterized in that: The step of obtaining the contact angle and cross-sectional area of ​​the deposited layer through the substrate temperature field comprises: Obtaining the size of the molten pool through the substrate temperature field; Based on the molten pool size, powder utilization and contact angle of the deposited layer are obtained; According to the powder utilization rate, the cross-sectional area of ​​the deposited layer is obtained.

7. The method for rapid prediction of laser coaxial powder feeding multi-layer deposition profile according to claim 1 is characterized in that: The step of constructing a prediction model for a single-pass single-layer deposition profile based on the contact angle and the cross-sectional area includes: Based on the contact angle, the cross-sectional area and the Young-Laplace equation, a prediction model for a single-pass single-layer deposition profile is constructed, and the Young-Laplace equation satisfies the following expression: in, is the surface tension coefficient, is the contour curvature, is the pressure difference between the gas and liquid surfaces.

8. The method for rapid prediction of laser coaxial powder feeding multi-layer deposition profile according to claim 7, characterized in that: The prediction model of the single-pass single-layer deposition profile satisfies the following expression: in, is the surface tension coefficient, is the first-order derivative of the distance between the profile curve and the central axis, is the second-order derivative of the distance between the contour curve and the central axis, is the coefficient, is the gravity state value, is the material density, is the single-channel single-layer deposition profile, is the volume fraction of liquid metal.

9. The method for rapid prediction of laser coaxial powder feeding multi-layer deposition profile according to claim 1, characterized in that: The step of obtaining a single-pass multi-layer deposition profile based on the prediction model includes: According to the prediction model, a single-channel single-layer deposition profile is obtained; The single-pass single-layer deposition profile is processed by using a profile construction method to obtain a single-pass multi-layer deposition profile.

10. The method for rapid prediction of laser coaxial powder feeding multi-layer deposition profile according to claim 9, characterized in that: The outline construction method includes a direct stacking construction method and an indirect stacking construction method of the outline; The direct stacking construction method includes a construction method in which multiple single-layer deposited layer sections are directly stacked after considering the melting area; The indirect stacking construction method includes a construction method in which the cross-sectional areas of multiple single-layer deposition layers are first superimposed and then stacked.

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