A method for preparing lightweight high-speed rail brake disc by selective laser melting deposition

Abstract

The present invention relates to a method for preparing a lightweight high-speed rail brake disc by selective laser melting deposition, which mainly constructs an equivalent load method process of a lightweight brake disc based on a topological optimization method. Based on the traditional casting brake disc model, a repeatable unit body model in the brake disc model is extracted for lightweight structural design, and unit body models with a weight reduction of 10%, 15% and 30% and good stress distribution are successfully designed respectively. Then, according to the equivalent integral method, the unit body models after topological optimization are combined to obtain three lightweight high-speed rail brake disc structure models with a weight reduction of 8%, 13% and 28%, among which the heat dissipation performance of the lightweight brake disc model with a weight reduction of 28% is improved by 17%. Under the optimized selective laser melting parameter conditions, a 1:10 scaled-down lightweight high-speed rail brake disc sample was successfully printed using 24CrNiMoY alloy steel powder. Compared with the model sample before lightweighting, the lightweight brake disc sample has the same wear resistance while reducing weight by 28%.

Description

Technical Field

[0001] The present invention relates to the technical field of additive manufacturing, and in particular to a method for preparing a lightweight high-speed rail brake disc by selective laser melting deposition. Background Art

[0002] High-speed rail brake discs are one of the key core parts in the braking system of high-speed trains. They are an important guarantee for the safe operation of trains and can effectively protect the lives and property of passengers. During the train braking process, the friction between the brake pads and the brake discs is relied on. During this process, the brake discs will generate a lot of heat, which is dissipated through heat flow, heat conduction and heat radiation. Reasonable brake disc structural design can improve the heat dissipation capacity of the brake discs. With the rapid development of high-speed rail manufacturing technology, the requirements for its safe and efficient braking are getting higher and higher. Lightweight brake discs not only have excellent heat dissipation performance, but also can reduce the unsprung mass of the train, improve braking efficiency, and meet the requirements of high-speed rail for brake discs. Therefore, how to manufacture lightweight high-speed rail brake discs has great scientific research and practical application value.

[0003] At present, the main manufacturing methods of brake discs in China are casting and forging, but they are difficult to meet the manufacturing needs of lightweight high-speed rail brake discs with complex structures. Selective laser melting technology is one of the additive manufacturing technologies. It has unique advantages in complex structural parts through powder laying and selective forming, and combined with topology optimization technology, it has become one of the most effective means of lightweight parts manufacturing. In the early research, the team has used VIGA technology to independently prepare 24CrNiMoY alloy steel powder with high sphericity and uniform particle size distribution suitable for selective laser melting, and can realize the selective laser melting preparation of high-speed rail brake disc models for traditional casting.

[0004] The research on lightweight design and preparation of high-speed rail brake discs is still in its infancy. At present, topology optimization is one of the most effective and scientific lightweight design methods. However, since the friction behavior of the brake disc is a process in which the action nodes and forces are constantly changing, it is impossible to directly achieve lightweight design through topology optimization calculations. Summary of the invention

[0005] In view of the above problems, the purpose of the present invention is to provide a method for preparing lightweight high-speed rail brake discs by selective laser melting deposition, and an equivalent load method process for the lightweight design of high-speed rail brake discs is proposed based on a topology optimization calculation method, which can design lightweight brake discs with excellent mechanical properties and good heat dissipation performance.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A method for preparing a lightweight high-speed rail brake disc by selective laser melting deposition proposed in the present invention comprises the following steps:

[0008] S1. Select a high-speed rail brake disc model;

[0009] S2, perform equivalent differentiation on the brake disc model and disassemble it into multiple unit structures;

[0010] S3. Perform topology optimization calculation and shape optimization on the unit structure;

[0011] S4, integrating the optimized unit structure equivalently into a lightweight brake disc model;

[0012] S5. According to the lightweight brake disc model, a lightweight high-speed rail brake disc is prepared by selective laser melting.

[0013] Furthermore, the high-speed rail brake disc model consists of a friction surface, an inner surface, heat dissipation ribs, connecting buckles and inner and outer circumferential surfaces.

[0014] Furthermore, the step S2 specifically includes: selecting the friction surface and the heat dissipation rib part of the brake disc model as the design domain for design, distributing the brake disc model according to the heat dissipation ribs, and using the equivalent differential method to equally cut the friction surface to obtain a plurality of "I"-shaped unit body structures, wherein the unit body structure is composed of a cylinder and regular hexagonal prisms coaxially symmetrically connected at both ends of the cylinder.

[0015] Furthermore, the step S3 specifically includes:

[0016] (S3.1) performing topology optimization calculation on the extracted unit cell structure using a solid isotropic material penalty model to remove the non-load-bearing part of the unit cell structure;

[0017] (S3.2) The optimized unit structure is a double "Y" shape, and the main change is that the regular hexagonal prisms at the upper and lower ends of the "I" shape are changed into a combination of regular hexagonal pyramids and regular hexagonal prisms;

[0018] (S3.3) A fillet is applied between the heat dissipation rib and the regular hexagonal pyramid of the double “Y”-shaped unit structure to optimize the shape.

[0019] Furthermore, the step (S3.1) specifically includes:

[0020] (S3.1.1) The mathematical model of the solid isotropic material penalty model used in topology optimization calculations is as follows:

[0021] Min c(ρ,U)=f T U

[0022]

[0023]

[0024]

[0025] ρ∈(0,1)

[0026] Among them, c is the compliance function unit body strain energy of the design target, ρ is the relative density of the calculation unit, U is the relative displacement matrix of the calculation unit, f is the external force load borne by each calculation unit, K is the overall stiffness matrix of the calculation unit, is the equivalent static load pressure, e i is the computing unit. o is the unit volume, V ρ To optimize the unit volume after calculation, x is the target volume fraction, K i represents the stiffness of the computational unit, N is the number of computational units in the design domain, ρ i is the relative density of the calculation unit, ρ min is the minimum relative density of all computational units in the design domain. p is the penalty factor.

[0027] (S3.1.2) The unit target volume x is set to a range of 70% to 90%, that is, a weight reduction range of 10% to 30%.

[0028] (S3.1.3) When performing topology optimization calculations, the stress boundary conditions are set as:

[0029]

[0030] in, is the equivalent static load pressure, is the area of ​​the brake disc S The transient pressure at .

[0031] Furthermore, the step S4 specifically includes:

[0032] (S4.1) The optimized unit cell structure is integrated and combined using the equivalent integration method, and 9 connecting buckles in the non-design domain are evenly added on the inner circumference to form a new lightweight brake disc model;

[0033] (S4.2) The weight reduction range is smaller than the preset range of the unit structure, and the result is 8% to 28%.

[0034] Furthermore, in the step (S4.1), the lightweight brake disc model includes upper and lower friction surfaces, inner and outer circumferential surfaces, heat dissipation ribs and an inner surface, wherein the inner surface is no longer a smooth plane, but becomes a concave and convex surface structure following the distribution of the heat dissipation ribs, and the inner and outer circumferential surfaces also become circumferential surfaces with a serrated structure as the inner surface changes.

[0035] Furthermore, in step S5, the powder used is 24CrNiMoY alloy steel powder, whose particle size distribution is 4-116 μm and the average powder particle size is 37 μm; the process parameters of laser melting are: laser power is 310 W, scanning speed is 1 m / s, scanning spacing is 0.09 mm, layer thickness is 0.05 mm, and substrate preheating temperature is 80°C.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] 1. The design and manufacturing method for lightweight brake discs proposed in the present invention realizes the transformation of complex repetitive structures into simple structures by decomposing and extracting the repetitive unit structures in the brake discs, effectively reduces the amount of calculation, effectively guarantees its mechanical properties, and improves the utilization rate of structural materials.

[0038] 2. The design and manufacturing method for lightweight brake discs proposed in the present invention converts the dynamic boundary pressure during braking into static pressure through the equivalent load method, and converts the dynamic topology optimization problem into a static topology optimization problem, thereby realizing the topology optimization lightweight design under dynamic stress state with complex repetitive structures.

[0039] 3. The process parameters of the selective laser melting method provided by the present invention can manufacture brake disc parts with a weight reduction range of 8-28% for the complex structure of lightweight high-speed rail brake discs. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a flow chart of the equivalent load calculus method for lightweight design of high-speed rail brake discs;

[0041] Figure 2 This is a brake disc model for traditional casting;

[0042] Figure 3 A schematic diagram of the original unit cell model process is proposed for the equivalent differential of the brake disc;

[0043] Figure 4 Schematic diagram of the topology optimization reconstruction process of the unit cell model with the goal of reducing weight by 10%;

[0044] Figure 5 A lightweight brake disc model that reduces weight by 8%;

[0045] Figure 6 Schematic diagram of the input conditions of heat flow at the equivalent friction heat boundary;

[0046] Figure 7 Schematic diagram of the equivalent friction heat boundary heat transfer coefficient condition;

[0047] Figure 8 This is the particle size distribution diagram of 24CrNiMoY alloy steel powder;

[0048] Fig. 9 Schematic diagram of a 1:10 scaled sample of a lightweight brake disc that reduces weight by 8%;

[0049] Fig.10 Schematic diagram of the topology optimization reconstruction process of the unit cell model with the target weight reduction of 15%;

[0050] Fig.11 A lightweight brake disc model that reduces weight by 13%;

[0051] Fig.12 Schematic diagram of a 1:10 scaled sample of a lightweight brake disc that reduces weight by 13%;

[0052] Fig.13 Schematic diagram of the topology optimization reconstruction process of the unit cell model with the goal of reducing weight by 30%;

[0053] Fig.14 A lightweight brake disc model that reduces weight by 28%;

[0054] Fig.15 Schematic diagram of a 1:10 scaled sample of a lightweight brake disc that reduces weight by 28%. DETAILED DESCRIPTION

[0055] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0056] Example 1

[0057] A method for preparing a lightweight high-speed rail brake disc by selective laser melting deposition, the method comprising lightweight design of a brake disc model and selective laser melting of 24CrNiMoY alloy steel. The lightweight design of the brake disc mainly uses SolidWorks2019 and Ansys Workbench 2020R2 software, the equivalent friction heat mainly uses AnsysWorkbench 2020R2 software, and the selective laser melting mainly uses Magics 23.1 software and the rapid prototyping manufacturing system AFS-M260. Figure 1 As shown, the specific implementation steps are as follows:

[0058] Step S1, selecting a high-speed rail brake disc model;

[0059] According to the traditional three-dimensional model of brake disc components for casting, such as Figure 2As shown, the radius of the friction surface 2-1 is 320 mm, the thickness of the circumferential surface 2-2 is 23 mm, the diameter of the heat dissipation rib 2-3 is 20 mm, 2-4 is the inner surface of the brake disc, and 2-5 is the connecting buckle.

[0060] Step S2, performing equivalent differentiation on the brake disc model and disassembling it into multiple unit structures;

[0061] The friction surface of the brake disc and the heat dissipation ribs are selected as the optimization area. The brake disc model is distributed according to the heat dissipation ribs. The friction surface is cut equally by equivalent differential method to obtain multiple "I"-shaped unit structures. The unit structure model consists of a cylinder 3-2 and regular hexagonal prisms 3-1 respectively arranged at both ends of the cylinder 3-2 and symmetrical. The process is as follows Figure 3 As shown, the dimensions of the unit structure are shown in Table 1.

[0062] Table 1 Unit model dimensions

[0063]

[0064] Step S3: topology optimization calculation and shape optimization of the unit structure:

[0065] (S3.1) Perform topology optimization calculation on the extracted unit structure using a solid isotropic material penalty model to remove the non-bearing capacity part; specifically including:

[0066] (S3.1.1) The unit cell model in step S2 is optimized and calculated using the solid isotropic material penalty model using Ansys Workbench 2020R2 software. The mesh adopts a tetrahedral mesh with a mesh size of 1 mm. The mathematical model is as follows:

[0067] Min c(ρ,U)=f T U

[0068]

[0069]

[0070]

[0071] ρ∈(0,1)

[0072] Among them, c is the compliance function unit body strain energy of the design target, ρ is the relative density of the calculation unit, U is the relative displacement matrix of the calculation unit, f is the external force load borne by each calculation unit, K is the overall stiffness matrix of the calculation unit, is the equivalent static load pressure, e i is the computing unit; V o is the unit volume, Vρ To optimize the unit volume after calculation, x is the target volume fraction, K i represents the stiffness of the computational unit, N is the number of computational units in the design domain, ρ i is the relative density of the calculation unit, ρ min is the minimum relative density of all computational units in the design domain; p is the penalty factor;

[0073] (S3.1.2) The unit body target volume x is set to a range of 70% to 90%, that is, a weight reduction range of 10% to 30%; in this embodiment, the material stiffness is 31 GPa, the p value is 3, and the target volume fraction x is set to 90%, that is, a 10% weight reduction within the design domain.

[0074] (S3.1.3) When performing topology optimization calculations, the stress boundary conditions are set as:

[0075]

[0076] in, is the equivalent static load pressure, is the area of ​​the brake disc S The transient pressure at .

[0077] According to TB / T 2980-2104 industry standard for brake discs for rolling stock, the brake pad area is 400cm 2 , the maximum thrust is 30kN, and the braking pressure on the friction surface of the brake disc can be obtained by calculation The direction is perpendicular to the friction surface.

[0078] (S3.2) Figure 4 The topology optimization reconstruction process of the unit body is carried out. The optimization goal is to minimize the maximum strain energy. The optimized unit body model is established with volume and displacement as constraints. The optimized unit body model is reconstructed using SolidWorks 2019 software. The optimized unit body is double "Y" shaped. The main change is that the regular hexagonal prisms at the upper and lower ends of the "I" shape are changed to a combination of a regular hexagonal pyramid and a regular hexagonal prism. The regular hexagonal pyramid is located between the regular hexagonal prism and the cylinder; the cylinder in the middle remains unchanged, the height of the regular hexagonal prism becomes 14mm, and the height of the regular hexagonal pyramid is 9mm. The results are as follows: Figure 4 As shown;

[0079] (S3.3) A fillet with a radius of 6 mm is applied between the heat dissipation rib and the regular hexagonal pyramid of the double “Y”-shaped unit body, i.e., at position 4-1, to perform shape optimization;

[0080] Static analysis was performed using Ansys Workbench 2020R2 software. It was found that the stress distribution of the unit model was improved after topology optimization, and the weight reduction target within the design domain was obtained. The strength results are shown in Table 2.

[0081] Table 2 Comparison of equivalent stress and volume before and after optimization of unit model

[0082]

[0083] Step S4, integrating the optimized unit structure into a lightweight brake disc model;

[0084] (S4.1) According to the equivalent integral principle, the optimized unit body model is reorganized, and 9 connectors in the non-design domain are evenly added on the inner circumference. The results are as follows: Figure 5 The figure below shows a lightweight high-speed rail brake disc model. Figure 2 The main change from the traditional cast brake disc is the inner surface, which is no longer a smooth plane, but a concave and convex surface following the distribution of the heat dissipation ribs. The inner and outer circumferential surfaces also become serrated circumferential surfaces as the inner surface changes;

[0085] The lightweight brake disc was subjected to equivalent friction heat analysis using Ansys Workbench 2020R2 software. The initial braking speed was 350 km / h, the braking time was 60 s, and the acceleration was 1.6 m / s. 2 , the mass is 60t, the heat flux input to the friction surface of the brake disc and the convection radiation coefficient of the lightweight brake disc are as follows Figure 6 and 7 As shown, after thermal analysis, the heat dissipation performance of the lightweight brake disc model is shown in Table 3, which is similar to the heat dissipation performance of the traditional casting brake disc model.

[0086] (S4.2) The volume comparison between the lightweight brake disc model and the traditional casting brake disc model is shown in Table 3. After calculation, the lightweight brake disc model has a volume of 92% of the volume of the traditional casting brake disc model due to the addition of a connecting buckle in the non-design domain, achieving an 8% weight reduction.

[0087] Table 3 Brake disc model heat dissipation performance and volume comparison

[0088]

[0089] Step S5, preparing a lightweight high-speed rail brake disc by selective laser melting according to the lightweight brake disc model;

[0090] (S5.1) The particle size distribution of the 24CrNiMoY alloy steel powder used is 4-116μm, and the average powder particle size is 37μm. Figure 8 Figure 2 shows the particle size distribution of 24CrNiMoY alloy steel powder.

[0091] (S5.2) The lightweight brake disc model is imported into Magics 23.1, supports are added to the lightweight model and processing allowances are reserved, and then the processed lightweight brake disc model is sliced, and the slice layer thickness is 0.05 mm.

[0092] (S5.3) The brake disc model after slicing is imported into the rapid prototyping manufacturing system AFS-M260, and the selective laser melting 24CrNiMoY alloy steel forming is started. During the selective laser melting preparation, a 260mm×260mm×20mm 316L substrate is used, and the pressure in the forming chamber is ensured to be 10MPa and the oxygen content is less than 2000ppm.

[0093] (S5.4) When laser melting preparation is selected, the process parameters used are: laser power of 310 W, scanning speed of 1 m / s, scanning spacing of 0.09 mm, layer thickness of 0.05 mm, and substrate preheating temperature of 80 °C.

[0094] (S5.5) After the printing is completed, the lightweight brake disc sample is cut off by wire cutting parallel to the substrate, and then the upper and lower working surfaces of the brake disc sample are ground by a grinder until the surface roughness Ra is less than 2.0. Fig. 9 shown.

[0095] (S5.6) The friction performance test was carried out using an MM-1000Ⅱ friction machine. The initial braking speed was 5000r / min and the braking pressure was 1.5Mpa. After 50 friction and wear tests, it was found that the wear of the lightweight front brake disc sample was 0.45g, while the wear of the lightweight rear brake disc sample was 0.44g. Therefore, the lightweight brake disc sample has good wear resistance.

[0096] Example 2

[0097] The present embodiment proposes a method for preparing a lightweight high-speed rail brake disc by selective laser melting deposition, which includes lightweight design of a brake disc model and preparation of 24CrNiMoY alloy steel by selective laser melting. The main difference is that the unit body target mass fraction is 85%, that is, a 15% weight reduction within the design domain. The specific implementation steps are as follows:

[0098] Step S1, selecting a high-speed rail brake disc model;

[0099] According to the traditional three-dimensional model of brake disc components for casting, such as Figure 2 As shown, the radius of the friction surface 2-1 is 320 mm, the thickness of the circumferential surface 2-2 is 23 mm, the diameter of the heat dissipation rib 2-3 is 20 mm, 2-4 is the inner surface of the brake disc, and 2-5 is the connecting buckle.

[0100] Step S2, performing equivalent differentiation on the brake disc model and disassembling it into multiple unit structures;

[0101] The friction surface of the brake disc and the heat dissipation ribs are selected as the optimization area. The brake disc model is distributed according to the heat dissipation ribs. The friction surface is cut equally by equivalent differential method to obtain multiple "I"-shaped unit structures. The unit structure model consists of a cylinder 3-2 and regular hexagonal prisms 3-1 respectively arranged at both ends of the cylinder 3-2 and symmetrical. The process is as follows Figure 3 As shown, the dimensions of the unit structure are shown in Table 4.

[0102] Table 4 Unit model dimensions

[0103]

[0104] Step S3: topology optimization calculation and shape optimization of the unit structure:

[0105] (S3.1) Perform topology optimization calculation on the extracted unit structure using a solid isotropic material penalty model to remove the non-bearing capacity part; specifically including:

[0106] (S3.1.1) The unit cell model in step S2 is optimized and calculated using the solid isotropic material penalty model using Ansys Workbench 2020R2 software. The mesh adopts a tetrahedral mesh with a mesh size of 1 mm. The mathematical model is as follows:

[0107] Min c(ρ,U)=f T U

[0108]

[0109]

[0110]

[0111] ρ∈(0,1)

[0112] Among them, c is the compliance function unit body strain energy of the design target, ρ is the relative density of the calculation unit, U is the relative displacement matrix of the calculation unit, f is the external force load borne by each calculation unit, K is the overall stiffness matrix of the calculation unit, is the equivalent static load pressure, e i is the computing unit; V o is the unit volume, V ρ To optimize the unit volume after calculation, x is the target volume fraction, K i represents the stiffness of the computational unit, N is the number of computational units in the design domain, ρ iis the relative density of the calculation unit, ρ min is the minimum relative density of all computational units in the design domain; p is the penalty factor;

[0113] (S3.1.2) The unit body target volume x is set to a range of 70% to 90%, that is, a weight reduction range of 10% to 30%; in this embodiment, the material stiffness is 31 GPa, the p value is 3, and the target volume fraction x is set to 85%.

[0114] (S3.1.3) When performing topology optimization calculations, the stress boundary conditions are set as:

[0115]

[0116] in, is the equivalent static load pressure, is the area of ​​the brake disc S The transient pressure at .

[0117] According to TB / T 2980-2104 industry standard for brake discs for rolling stock, the brake pad area is 400cm 2 , the maximum thrust is 30kN, and the braking pressure on the friction surface of the brake disc can be obtained by calculation The direction is perpendicular to the friction surface.

[0118] (S3.2) Fig.10 The topology optimization reconstruction process of the unit body is carried out. The optimization goal is to minimize the maximum strain energy. The optimized unit body model is established with volume and displacement as constraints. The optimized unit body model is reconstructed using SolidWorks 2019 software. The optimized unit body is double "Y" shaped. The main change is that the regular hexagonal prisms at the upper and lower ends of the "I" shape are changed to a combination of a regular hexagonal pyramid and a regular hexagonal prism. The regular hexagonal pyramid is located between the regular hexagonal prism and the cylinder; the cylinder in the middle remains unchanged, the height of the regular hexagonal prism becomes 12mm, and the height of the regular hexagonal pyramid is 11mm. The results are as follows: Fig.10 As shown;

[0119] (S3.3) A fillet with a radius of 6 mm was applied between the heat dissipation rib and the regular hexagonal pyramid of the double "Y"-shaped unit, i.e., at position 8-1, and shape optimization was performed. The results are as follows: Fig.10 As shown;

[0120] Static analysis was performed using Ansys Workbench 2020R2 software. It was found that the stress distribution of the unit model was improved after topology optimization, and the weight reduction target within the design domain was obtained. The strength results are shown in Table 5.

[0121] Table 5 Comparison of equivalent stress and volume before and after optimization of unit model

[0122]

[0123] Step S4, integrating the optimized unit structure into a lightweight brake disc model;

[0124] (S4.1) According to the equivalent integral principle, the optimized unit body model is reorganized, and 9 connectors in the non-design domain are evenly added on the inner circumference. The results are as follows: Fig.11 The figure below shows a lightweight high-speed rail brake disc model. Figure 2 The main change from the traditional cast brake disc is the inner surface, which is no longer a smooth plane, but a concave and convex surface following the distribution of the heat dissipation ribs. The inner and outer circumferential surfaces also become serrated circumferential surfaces as the inner surface changes;

[0125] The lightweight brake disc was subjected to equivalent friction heat analysis using Ansys Workbench 2020R2 software. The initial braking speed was 350 km / h, the braking time was 60 s, and the acceleration was 1.6 m / s. 2 , the mass is 60t, the heat flux input to the friction surface of the brake disc and the convection radiation coefficient of the lightweight brake disc are as follows Figure 6 and 7 As shown, after thermal analysis, the heat dissipation performance of the lightweight brake disc model is shown in Table 3, which is similar to the heat dissipation performance of the traditional casting brake disc model.

[0126] (S4.2) The volume comparison between the lightweight brake disc model and the traditional casting brake disc model is shown in Table 6. After calculation, the lightweight brake disc model has a volume of 87% of the volume of the traditional casting brake disc model due to the addition of a connecting buckle in the non-design domain, achieving a 13% weight reduction.

[0127] Table 6 Comparison of heat dissipation performance and volume of brake disc model

[0128]

[0129] Step S5, preparing a lightweight high-speed rail brake disc by selective laser melting according to the lightweight brake disc model;

[0130] (S5.1) The particle size distribution of the 24CrNiMoY alloy steel powder used is 4-116μm, and the average powder particle size is 37μm. Figure 8 As shown, the particle size distribution of 24CrNiMoY alloy steel powder;

[0131] (S5.2) Import the lightweight brake disc model into Magics 23.1, add support to the lightweight model and leave a processing allowance, and then slice the processed lightweight brake disc model with a slice layer thickness of 0.05 mm;

[0132] (S5.3) The brake disc model after slicing is imported into the rapid prototyping manufacturing system AFS-M260, and the selective laser melting of 24CrNiMoY alloy steel is started. During the selective laser melting preparation, a 260mm×260mm×20mm 316L substrate is used, and the pressure in the molding chamber is ensured to be 10MPa and the oxygen content is less than 2000ppm;

[0133] (S5.4) When laser melting is selected for preparation, the process parameters used are: laser power of 310 W, scanning speed of 1 m / s, scanning spacing of 0.09 mm, layer thickness of 0.05 mm, and substrate preheating temperature of 80 °C;

[0134] (S5.5) After the printing is completed, the lightweight brake disc sample is cut off by wire cutting parallel to the substrate, and then the upper and lower working surfaces of the brake disc sample are ground by a grinder until the surface roughness Ra is less than 2.0. Fig.12 As shown;

[0135] (S5.6) The friction performance test was carried out using an MM-1000Ⅱ friction machine. The initial braking speed was 5000r / min and the braking pressure was 1.5Mpa. After 50 friction and wear tests, it was found that the wear of the lightweight front brake disc sample was 0.45g, while the wear of the lightweight rear brake disc sample was 0.44g. Therefore, the lightweight brake disc sample has good wear resistance.

[0136] Example 3

[0137] The present embodiment proposes a method for preparing a lightweight high-speed rail brake disc by selective laser melting deposition, which includes lightweight design of a brake disc model and preparation of 24CrNiMoY alloy steel by selective laser melting. The main difference is that the unit body target mass fraction is 70%, that is, a 30% weight reduction within the design domain. The specific implementation steps are as follows:

[0138] Step S1, selecting a high-speed rail brake disc model;

[0139] According to the traditional three-dimensional model of brake disc components for casting, such as Figure 2 As shown, the radius of the friction surface 2-1 is 320 mm, the thickness of the circumferential surface 2-2 is 23 mm, the diameter of the heat dissipation rib 2-3 is 20 mm, 2-4 is the inner surface of the brake disc, and 2-5 is the connecting buckle.

[0140] Step S2, performing equivalent differentiation on the brake disc model and disassembling it into multiple unit structures;

[0141] The friction surface of the brake disc and the heat dissipation ribs are selected as the optimization area. The brake disc model is distributed according to the heat dissipation ribs. The friction surface is cut equally by equivalent differential method to obtain multiple "I"-shaped unit structures. The unit structure model consists of a cylinder 3-2 and regular hexagonal prisms 3-1 respectively arranged at both ends of the cylinder 3-2 and symmetrical. The process is as follows Figure 3 As shown, the dimensions of the unit structure are shown in Table 7.

[0142] Table 7 Unit model dimensions

[0143]

[0144] Step S3: topology optimization calculation and shape optimization of the unit structure

[0145] (S3.1) Perform topology optimization calculation on the extracted unit structure using a solid isotropic material penalty model to remove the non-bearing capacity part; specifically including:

[0146] (S3.1.1) The unit cell model in step S2 is optimized and calculated using the solid isotropic material penalty model using Ansys Workbench 2020R2 software. The mesh adopts a tetrahedral mesh with a mesh size of 1 mm. The mathematical model is as follows:

[0147] Min c(ρ,U)=f T U

[0148]

[0149]

[0150]

[0151] ρ∈(0,1)

[0152] Among them, c is the compliance function unit body strain energy of the design target, ρ is the relative density of the calculation unit, U is the relative displacement matrix of the calculation unit, f is the external force load borne by each calculation unit, K is the overall stiffness matrix of the calculation unit, is the equivalent static load pressure, e i is the computing unit; V o is the unit volume, V ρ To optimize the unit volume after calculation, x is the target volume fraction, K i represents the stiffness of the computational unit, N is the number of computational units in the design domain, ρ i is the relative density of the calculation unit, ρ min is the minimum relative density of all computational units in the design domain; p is the penalty factor;

[0153] (S3.1.2) The unit body target volume x is set to a range of 70% to 90%, that is, a weight reduction range of 10% to 30%; in this embodiment, the material stiffness is 31 GPa, the p value is 3, and the target volume fraction x is set to 70%.

[0154] (S3.1.3) When performing topology optimization calculations, the stress boundary conditions are set as:

[0155]

[0156] in, is the equivalent static load pressure, is the area of ​​the brake disc S The transient pressure at .

[0157] According to TB / T 2980-2104 industry standard for brake discs for rolling stock, the brake pad area is 400cm 2 , the maximum thrust is 30kN, and the braking pressure on the friction surface of the brake disc can be obtained by calculation The direction is perpendicular to the friction surface.

[0158] (S3.2) Fig.13 The topology optimization reconstruction process of the unit body is carried out. The optimization goal is to minimize the maximum strain energy. The optimized unit body model is established with volume and displacement as constraints. The optimized unit body model is reconstructed using SolidWorks 2019 software. The optimized unit body is double "Y" shaped. The main change is that the regular hexagonal prisms at the upper and lower ends of the "I" shape are changed to a combination of regular hexagonal pyramids and regular hexagonal prisms. The regular hexagonal pyramid is located between the regular hexagonal prism and the cylinder; the cylinder in the middle remains unchanged, the height of the regular hexagonal prism becomes 5mm, and the height of the regular hexagonal pyramid is 18mm. The results are as follows: Fig.13 As shown;

[0159] (S3.3) A fillet with a radius of 6 mm was applied between the heat dissipation rib and the regular hexagonal pyramid of the double "Y"-shaped unit, i.e., at position 11-1, and shape optimization was performed. The results are as follows: Fig.13 As shown;

[0160] Static analysis was performed using Ansys Workbench 2020R2 software. It was found that the stress distribution of the unit model was improved after topology optimization, and the weight reduction target within the design domain was obtained. The strength results are shown in Table 8.

[0161] Table 8 Comparison of equivalent stress and volume before and after optimization of unit body model

[0162]

[0163] Step S4, integrating the optimized unit structure into a lightweight brake disc model;

[0164] (S4.1) According to the equivalent integral principle, the optimized unit body model is reorganized, and 9 connectors in the non-design domain are evenly added on the inner circumference. The results are as follows: Fig.14 The figure below shows a lightweight high-speed rail brake disc model. Figure 2 The main change from the traditional cast brake disc is the inner surface, which is no longer a smooth plane, but a concave and convex surface following the distribution of the heat dissipation ribs. The inner and outer circumferential surfaces also become serrated circumferential surfaces as the inner surface changes;

[0165] The lightweight brake disc was subjected to equivalent friction heat analysis using Ansys Workbench 2020R2 software. The initial braking speed was 350 km / h, the braking time was 60 s, and the acceleration was 1.6 m / s. 2 , the mass is 60t, the heat flux input to the friction surface of the brake disc and the convection radiation coefficient of the lightweight brake disc are as follows Figure 8 As shown, after thermal analysis, the heat dissipation performance of the lightweight brake disc model is shown in Table 9, which is similar to the heat dissipation performance of the traditional casting brake disc model;

[0166] (S4.2) The volume comparison between the lightweight brake disc model and the traditional casting brake disc model is shown in Table 3. After calculation, the lightweight brake disc model has a volume of 77% of the volume of the traditional casting brake disc model due to the addition of a connecting buckle in the non-design domain, achieving a 28% weight reduction.

[0167] Table 9 Brake disc model heat dissipation performance and volume comparison

[0168]

[0169] Step 5, preparing a lightweight high-speed rail brake disc by selective laser melting, including the following steps:

[0170] (S5.1) The particle size distribution of the 24CrNiMoY alloy steel powder used is 4-116μm, and the average powder particle size is 37μm. Figure 8 Figure 2 shows the particle size distribution of 24CrNiMoY alloy steel powder.

[0171] (S5.2) The lightweight brake disc model is imported into Magics 23.1, supports are added to the lightweight model and processing allowances are reserved, and then the processed lightweight brake disc model is sliced, and the slice layer thickness is 0.05 mm.

[0172] (S5.3) The brake disc model after slicing is imported into the rapid prototyping manufacturing system AFS-M260, and the selective laser melting 24CrNiMoY alloy steel forming is started. During the selective laser melting preparation, a 260mm×260mm×20mm 316L substrate is used, and the pressure in the forming chamber is ensured to be 10MPa and the oxygen content is less than 2000ppm.

[0173] (S5.4) When laser melting preparation is selected, the process parameters used are: laser power of 310 W, scanning speed of 1 m / s, scanning spacing of 0.09 mm, layer thickness of 0.05 mm, and substrate preheating temperature of 80°C.

[0174] (S5.5) After the printing is completed, the lightweight brake disc sample is cut off by wire cutting parallel to the substrate, and then the upper and lower working surfaces of the brake disc sample are ground by a grinder until the surface roughness Ra is less than 2.0. Fig.15 shown.

[0175] (S5.6) The friction performance test was carried out using an MM-1000Ⅱ friction machine. The initial braking speed was 5000r / min and the braking pressure was 1.5Mpa. After 50 friction and wear tests, it was found that the wear of the lightweight front brake disc sample was 0.45g, while the wear of the lightweight rear brake disc sample was 0.46g. Therefore, the lightweight brake disc sample has good wear resistance.

[0176] The embodiments described above are merely descriptions of preferred implementation modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing a lightweight high-speed railway brake disc by selective laser melting deposition, characterized in that: The method comprises the following steps: S1. Select a high-speed rail brake disc model; S2, perform equivalent differentiation on the brake disc model and disassemble it into multiple unit structures; S3. Perform topology optimization calculation and shape optimization on the unit structure; S4, integrating the optimized unit structure equivalently into a lightweight brake disc model; S5. Preparing a lightweight high-speed rail brake disc by selective laser melting according to a lightweight brake disc model; The high-speed rail brake disc model is composed of a friction surface, an inner surface, heat dissipation ribs, a connecting buckle and inner and outer circumferential surfaces; The step S2 specifically includes: selecting the friction surface and the heat dissipation rib part of the brake disc model as the design domain for design, distributing the brake disc model according to the heat dissipation ribs, and using the equivalent differential method to equally divide the friction surface to obtain a plurality of "I"-shaped unit body structures, wherein the unit body structure is composed of a cylinder and regular hexagonal prisms coaxially symmetrically connected at both ends of the cylinder; The step S3 specifically includes: (S3.1) performing topology optimization calculation on the extracted unit cell structure using a solid isotropic material penalty model to remove the non-load-bearing part of the unit cell structure; (S3.2) The optimized unit structure is a double "Y" shape, and the main change is that the regular hexagonal prisms at the upper and lower ends of the "I" shape are changed into a combination of regular hexagonal pyramids and regular hexagonal prisms; (S3.3) Add fillets between the heat dissipation ribs and the regular hexagonal pyramid of the double "Y"-shaped unit structure to optimize the shape; The step (S3.1) specifically includes: (S3.1.1) The mathematical model of the solid isotropic material penalty model used in topology optimization calculations is as follows: Let c(ρ,U)=f T HE ρ∈(0,1) Among them, c is the compliance function unit body strain energy of the design target, ρ is the relative density of the calculation unit, U is the relative displacement matrix of the calculation unit, F is the external force load borne by each calculation unit, K is the overall stiffness matrix of the calculation unit, is the equivalent static load pressure, e i is the computing unit; V o is the unit volume, V ρ To optimize the unit volume after calculation, x is the target volume fraction, K i represents the stiffness of the computational unit, N is the number of computational units in the design domain, ρ i is the relative density of the calculation unit, ρ min is the minimum relative density of all computational units in the design domain; p is the penalty factor; (S3.1.2) Setting the unit target volume x range to 70% to 90%, i.e., the weight reduction range to 10% to 30%; (S3.1.3) When performing topology optimization calculations, the stress boundary conditions are set as: in, is the equivalent static load pressure, is the area of ​​the brake disc S The transient pressure at .

2. The method for preparing a lightweight high-speed railway brake disc by selective laser melting deposition according to claim 1, characterized in that: The step S4 specifically includes: (S4.1) The optimized unit cell structure is integrated and combined using the equivalent integration method, and 9 connecting buckles in the non-design domain are evenly added on the inner circumference to form a new lightweight brake disc model; (S4.2) The weight reduction range is smaller than the preset range of the unit structure, and the result is 8% to 28%.

3. The method for preparing a lightweight high-speed railway brake disc by selective laser melting deposition according to claim 2, characterized in that: In the step (S4.1), the lightweight brake disc model includes upper and lower friction surfaces, inner and outer circumferential surfaces, heat dissipation ribs and an inner surface, wherein the inner surface is no longer a smooth plane, but becomes a concave-convex surface structure following the distribution of the heat dissipation ribs, and the inner and outer circumferential surfaces also become circumferential surfaces with a serrated structure as the inner surface changes.

4. The method for preparing a lightweight high-speed railway brake disc by selective laser melting deposition according to claim 1, characterized in that: In step S5, the powder used is 24CrNiMoY alloy steel powder, the particle size distribution of which is 4-116 μm, and the average powder particle size is 37 μm; the process parameters of laser melting are: laser power is 310 W, scanning speed is 1 m / s, scanning spacing is 0.09 mm, layer thickness is 0.05 mm, and substrate preheating temperature is 80°C.

Images