High-rigidity active thermal management bracket for space laser terminal CPA and its fabrication method

Abstract

This invention discloses a high-rigidity active thermal management bracket for space laser terminal CPA and its fabrication method. The bracket is integrally formed from aluminum alloy powder and includes: a solid connection area, located at the installation interface between the bracket and the external system, which is a solid block without a lattice structure; a main load-bearing lattice area, filled with body-centered cubic lattice, connected to the solid connection area and located on the main force transmission path of the bracket; and a thermal deformation matching lattice area, filled with concave negative Poisson's ratio hexagonal lattice, located in the non-main load-bearing area of ​​the bracket and configured to manage the thermal deformation of the bracket. This invention, through a partitioned lattice design, simultaneously meets the high rigidity requirements of the launch phase and the thermal deformation matching requirements of the on-orbit phase. Using Al-Mg-Sc series aluminum alloy material, and through hot isostatic pressing and T6 heat treatment processes, it achieves excellent performance in terms of high rigidity, lightweight, and controllable thermal deformation.

Description

Technical Field

[0001] This invention relates to the field of spacecraft optomechanical structure design technology, and in particular to a high-rigidity active thermal management bracket for space laser terminal CPA and its fabrication method. Background Technology

[0002] The support structure of the coarse pointing mechanism (CPA) for a space laser terminal is the core load-bearing and positioning structure of the optomechanical system. Its performance directly determines the stability and accuracy of the optical path during the emission phase and under complex thermal conditions in orbit. The core requirements for this type of support are: (1) Extremely high specific stiffness (resisting deformation caused by static and dynamic loads); (2) Extremely low thermal deformation (matching the thermal expansion of the telescope mounting interface).

[0003] The current mainstream solution is to manufacture the support using aluminum-based silicon carbide (SiC / Al) composite materials. SiC / Al has extremely high specific stiffness and an adjustable low coefficient of thermal expansion (CTE), which can achieve good thermal deformation matching with telescopes made of the same material. However, this material has fatal drawbacks, such as extremely difficult processing, extremely long processing time, and extremely high cost, which seriously restricts the product development progress and cost control.

[0004] If aluminum alloys, which have better processing performance and lower cost, are used instead, two unavoidable technical problems will be encountered: (1) Insufficient stiffness: The elastic modulus of aluminum alloy (70GPa) is much lower than that of SiC / Al (145GPa), resulting in greater deformation under the same load, which makes it difficult to meet the stability requirements of the optical platform. (2) Thermal mismatch: The coefficient of thermal expansion of aluminum alloy (CTE ≈ 23-24 × 10) -6 The temperature (°C) is much higher than that of SiC / Al or silicon carbide (SiC) materials commonly used in telescopes (CTE ≈ 4-10 × 10⁻⁶). -6 Temperature fluctuations in orbit (°C) will generate enormous thermal stress, causing structural warping, optical path deviation, and ultimately system failure.

[0005] Therefore, there is an urgent need in this field for an innovative design that can overcome the performance limitations of the material itself, enabling aluminum alloy components to exhibit both high stiffness and low thermal expansion characteristics similar to SiC / Al on a macroscopic scale. Summary of the Invention

[0006] The technical problem solved by this invention is to overcome the shortcomings of the prior art and provide a high-rigidity active thermal management bracket for space laser terminal CPA. Under the premise of using low-cost aluminum alloy, the bracket achieves the same specific stiffness as aluminum-based silicon carbide and thermal deformation behavior that matches the telescope mounting surface, thus resolving the contradiction between cost, cycle and performance of space laser terminal CPA bracket.

[0007] The technical solution of this invention is: a high-rigidity active thermal management bracket for space laser terminal CPA, integrally molded from aluminum alloy powder, comprising: The solid connection area, located at the installation interface area where the bracket connects to the external system, is a solid block without a dot matrix structure. The main load-bearing lattice area is filled with an enhanced lattice structure, connected to the solid connection area, and located on the main force transmission path of the support. The thermal deformation matching lattice region, filled with thermal deformation compensation lattice structures, is located in the non-main load-bearing area of ​​the support and is configured to manage the thermal deformation of the support.

[0008] Furthermore, the bracket has a U-shaped structure, and the solid connection area includes: The U-shaped structure has a mounting boss at the top of each of the two upper arms for connecting the telescope; The bottom of the U-shaped structure has a mounting boss for connecting the orientation motor.

[0009] Furthermore, the enhanced lattice structure adopts a body-centered cubic lattice, and its lattice parameters are optimized to maximize the first-order natural frequency of the support and constrain the support mass to not exceed a preset value; the thermal deformation compensation lattice structure adopts a concave negative Poisson's ratio hexagonal lattice, and its lattice parameters are optimized to make the equivalent thermal expansion coefficient in the optical axis direction as close as possible to the telescope mounting surface material.

[0010] Furthermore, the body-centered cubic lattice has a unit cell size of 10-20 mm, a beam diameter of 0.8-1.5 mm, and a relative density of 30%-50%.

[0011] Furthermore, the concave negative Poisson's ratio hexagonal lattice has a unit cell size of 10~20mm, a beam diameter of 0.8~1.5mm, a tilt angle of 30~60°, and an equivalent thermal expansion coefficient ≤15.0×10⁻⁶ in the optical axis direction. -6 / °C.

[0012] Furthermore, the first-order natural frequency of the bracket is greater than 500Hz, the mass is less than 2.0kg, and the thermal deformation difference between the bracket and the telescope mounting surface is less than 0.0002m under ±50°C conditions.

[0013] Furthermore, the composition of the aluminum alloy powder satisfies the following: Mg: 4.0-4.9wt%, Sc: 0.6-0.8wt%, Zr: 0.3-0.5wt%, Mn: 0.4-0.6wt%, with the balance being Al.

[0014] Furthermore, the aluminum alloy powder has a particle size distribution of 20-63 μm.

[0015] This invention also relates to a method for fabricating a high-rigidity active thermal management bracket for a space laser terminal CPA, comprising: (1) Using the variable density method, the layout of the solid connection area, main load-bearing lattice area and thermal deformation matching lattice area of ​​the support is determined through topology optimization; (2) Partition filling of enhanced lattice and thermal deformation compensation lattice, and optimization of lattice parameters respectively; (3) Aluminum alloy powder is used to integrally form the bracket through laser powder bed melting technology; (4) Post-processing of the molded parts, including hot isostatic pressing and heat treatment; (5) Perform fine machining on the installation interface of the solid connection area.

[0016] Furthermore, the temperature is 480±10°C, the pressure is 1000±50 bar, and the holding time is 1.5~3 hours; the heat treatment adopts the T6 heat treatment regime, specifically: 325±10°C, holding for 3~4 hours followed by water quenching, 160±10°C, aging for 8 hours followed by air cooling.

[0017] The advantages of this invention compared to the prior art are: (1) Performance breakthrough: Through multi-scale collaborative design strategy, topology optimization is carried out at the macro scale to determine the optimal force transmission path, and hybrid lattice structure is designed at the micro scale to achieve separate control and integration of stiffness and thermal expansion. Metal additive manufacturing technology is used for integrated molding, so that the aluminum alloy macroscopic performance has both high stiffness and low CTE, and the comprehensive performance is close to or even surpasses the traditional SiC / Al support in some areas.

[0018] (2) Cost and cycle advantages: material costs are reduced by more than 80%, and the manufacturing cycle is shortened from several months to several weeks.

[0019] (3) High reliability: Integrated molding avoids connection and assembly errors, and the transition zone design eliminates stress concentration problems caused by sudden performance changes.

[0020] (4) Excellent thermal management: The high thermal conductivity of aluminum alloy (~150W / m•K) combined with the huge surface area of ​​the lattice structure greatly promotes the thermal balance inside the support and avoids excessive temperature gradient caused by uneven on-orbit radiation.

[0021] (5) Significant lightweight effect: Through the lattice structure design, the mass is reduced by more than 50% compared with the solid structure, while the specific stiffness is increased by more than 3 times. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall structure and hybrid dot matrix partitioning design of the support of the present invention; Figure 2This is a schematic diagram of the reinforced lattice structure for filling the main load-bearing lattice region of the present invention; Figure 3 This is a schematic diagram of the thermal deformation compensation lattice structure for filling the thermal deformation matching lattice region of the present invention. Detailed Implementation

[0023] To better understand the technical solution of the present invention, the specific embodiments of the present invention are described below.

[0024] The high-rigidity active thermal management bracket for space laser terminal CPA proposed in this invention is integrally molded from aluminum alloy powder and includes: The solid connection area, located at the installation interface area where the bracket connects to the external system, is a solid block without a dot matrix structure. The main load-bearing lattice area is filled with an enhanced lattice structure, connected to the solid connection area, and located on the main force transmission path of the support. The thermal deformation matching lattice region, filled with thermal deformation compensation lattice structures, is located in the non-main load-bearing area of ​​the support and is configured to manage the thermal deformation of the support.

[0025] In one specific implementation, taking a space laser communication terminal CPA bracket as an example, such as... Figure 1 As shown, the support structure is U-shaped, with an envelope of 300mm in length (X-axis), 100mm in width (Y-axis), and 200mm in height (Z-axis, optical axis direction). Each of the two upper arms of the U-shape has an 80mm circular mounting boss (for connecting the telescope), and the bottom center has a 120mm circular mounting boss (for connecting the azimuth motor). The operating conditions of the support are as follows: Static condition: Simulates the overload during rocket launch. An acceleration of 10g in the Z-axis is applied to the bottom mounting surface, and corresponding reaction forces are applied to the two upper mounting surfaces.

[0026] Dynamic operating conditions: Simulate random vibration of the launch section. Apply random vibration power spectral density (PSD) curves of 10-2000Hz as specified in GJB 150.16A-2009 standard to three mounting surfaces.

[0027] Thermal conditions: Simulate temperature changes during on-orbit operation. Define the entire structure to experience a uniform temperature field change from -50°C to +50°C, and evaluate its thermal deformation.

[0028] Specifically, the structural design of the high-rigidity active thermal management bracket is as follows: (1) Topology optimization and partitioning design With the objective function of minimizing overall flexibility (i.e. maximizing stiffness) and the constraint that the mass volume does not exceed 30% of the design space, and the design variable being element density, topology optimization using the variable density method is performed using the OptiStruct solver.

[0029] After optimization calculations, a material density distribution cloud map was obtained. Regions with a density ≥ 0.55 were identified as the main force transmission paths. These paths are primarily responsible for transmitting loads and are sensitive to stiffness, thus designated as main load-bearing lattice region 2. Regions with a density < 0.55 contribute less to stiffness and mainly serve as connections and supports, but are crucial for weight reduction and thermal deformation control, thus designated as thermal deformation matching lattice region 3. The mounting interface area connecting to external systems (telescope, azimuth motor) was directly set as solid connection area 1 (non-design area), with its width set to 4 times the diameter of the mounting screw (M4), i.e., 16mm, to ensure connection reliability.

[0030] (2) Lattice filling and multi-scale optimization (2.1) Design of the main load-bearing lattice area The primary load-bearing lattice region 2 is responsible for bearing and transmitting the main vibration loads during the launch phase. Its design goal is to provide maximum dynamic stiffness (i.e., high natural frequency and high modulus) with minimal mass. The reinforced lattice structure filling the primary load-bearing lattice region is designed as a body-centered cubic lattice, such as... Figure 2 As shown, it achieves balanced and excellent stiffness and strength performance in multiple directions, making it particularly suitable for aerospace structures subjected to complex vibration loads.

[0031] Parametric modeling: The main load-bearing lattice region 2, determined by topology optimization, is used as the filling domain and imported into a body-centered cubic lattice unit cell. The initial unit cell size is set to 15 mm, and the beam diameter is 1.2 mm. Through functional gradient design, a smooth transition is achieved between the lattice structure and the solid connection region, avoiding stress concentration.

[0032] Parameter optimization: With the goal of maximizing the overall first-order natural frequency and the constraint of not exceeding 1.5 kg, the parameters of the lattice were optimized. The relative density of the region was finally determined to be 35%. Finite element analysis showed that its equivalent elastic modulus could reach 25 GPa (approximately 35% of that of dense aluminum alloy), but the mass was reduced by 65%.

[0033] (2.2) Design of thermal deformation matching lattice region The thermal deformation matching lattice region is responsible for actively managing thermal deformation, and its equivalent thermal expansion coefficient is designed to match the material of the telescope mounting interface. Specifically, a concave negative Poisson's ratio hexagonal lattice is used, whose unique "inner expansion and outer contraction" deformation mechanism allows it to "contract" in a specific direction (Z direction in this embodiment) when heated, thereby offsetting the thermal expansion effect of the material itself and achieving an ultra-low or even negative thermal expansion coefficient.

[0034] Parametric modeling: The thermal deformation matching lattice region is filled with concave negative Poisson's ratio hexagonal lattice unit cells. The initial unit cell size is set to 12 mm, the beam diameter to 0.8 mm, and the tilt angle to 45°.

[0035] Parameter optimization: Thermal-structural coupled finite element analysis was performed to make the Z-axis equivalent CTE as close as possible to the telescope mounting surface material (SiC / Al, CTE = 13 × 10⁻⁶). -6 With a target of / °C, for example, a thermal displacement difference ΔZ < 0.0002m in the Z direction, the tilt angle of the lattice was fine-tuned (finally set at 45.5°) and the beam diameter. Ultimately, the equivalent CTE in the Z direction of this region was precisely controlled to 12.5 × 10⁻⁶ m. -6 / °C, achieving excellent thermal matching characteristics.

[0036] (3) Additive manufacturing Material Preparation: Scalmalloy® spherical powder was selected. Its chemical composition met the following requirements: Mg: 4.0-4.9 wt%, Sc: 0.6-0.8 wt%, Zr: 0.3-0.5 wt%, Mn: 0.4-0.6 wt%, with the balance being Al. The powder particle size distribution was 20-63 μm. The addition of Sc and Zr elements can form fine Al3(Sc,Zr) precipitates during the L-PBF process, greatly refining the grain size and improving the material's strength and toughness.

[0037] Printing process: Laser power: 370W; Scanning speed: 1300mm / s; Layer thickness: 30μm.

[0038] Printing process: Import the final design .stl file into the device and add the necessary support structures (mainly focusing on the areas where the solid connection zone contacts the substrate). The entire component is printed in one go.

[0039] (4) Post-processing Wire cutting: After printing, the components are separated from the substrate by wire electrical discharge machining.

[0040] Hot Isostatic Pressing (HIP): The component is placed in a hot isostatic pressing apparatus. The processing parameters are: temperature 480°C (±10°C), pressure 1000 bar (±50 bar), and holding at temperature and pressure for 2 hours. This process effectively closes internal micropores and incomplete fusion defects, increasing the density of the part to over 99.99% and significantly improving fatigue performance.

[0041] Heat treatment: The T6 heat treatment regime is adopted, specifically as follows: Solution treatment: The parts are kept at 325°C in air for 4 hours to allow the alloying elements to fully dissolve into the aluminum matrix.

[0042] Quenching: The parts are quickly removed from the furnace and immersed in a room temperature water bath for water quenching to obtain a supersaturated solid solution.

[0043] Aging: Place the parts in an oven at 160°C for 8 hours and then air cool. This process promotes the precipitation of fine Al3(Sc,Zr) nanophases, enabling the material to reach its maximum strength (yield strength can reach over 500 MPa).

[0044] Surface treatment: Sandblasting (using 100-mesh glass beads) is used to remove surface powder and some supporting structures.

[0045] (5) Precision machining Using a five-axis CNC milling machine, the three mounting interfaces were milled based on the finished mounting surface itself. The flatness of the mounting surfaces was ensured to be better than 0.01 mm, the surface roughness Ra < 0.8 μm, and the hole position accuracy to H7 grade. Finally, the remaining support structure was carefully removed by hand tools, and the lattice areas were lightly polished to remove burrs.

[0046] The following results were obtained by conducting comprehensive performance tests on the final product of this embodiment: Geometric dimensions: All critical dimensions are inspected using a coordinate measuring machine, and the tolerances are within ±0.1mm.

[0047] Mass: The final mass was measured to be 1.55 kg using a precision electronic balance.

[0048] Mechanical properties: Modal testing: The first natural frequency of the sinusoidal sweep display bracket is 525 Hz.

[0049] Thermal performance testing: The support and the simulation block (made of SiC / Al) were bolted together and placed in a high and low temperature test chamber. Three cycles were performed from -50°C to +50°C. A laser interferometer was used to monitor the relative displacement of the mounting surfaces in the Z direction in real time. Test results show that the maximum thermal deformation difference is only 0.0001m throughout the entire temperature range.

[0050] The above test results fully demonstrate that the lattice support successfully prepared by this invention has excellent comprehensive performance and fully meets the application requirements of space laser terminal CPA.

[0051] It is understood that this invention has been described through embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of this invention. Furthermore, under the teachings of this invention, these features and embodiments can be modified to adapt to specific circumstances without departing from the spirit and scope of this invention. Therefore, this invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are protected by this invention.

[0052] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A high-rigidity active thermal management bracket for space laser terminal CPA, characterized in that, It is made of aluminum alloy powder in one piece, including: Solid connection area (1), located in the installation interface area where the bracket connects to the external system, is set as a solid block without a dot matrix structure; The main load-bearing lattice area (2) is located on the main force transmission path extending from the solid connection area (1) and is filled with an enhanced lattice structure; The thermal deformation matching lattice area (3), located in the non-main load-bearing area of ​​the support, is filled with a thermal deformation compensation lattice structure and is configured to manage the thermal deformation of the support.

2. The high-rigidity active thermal management bracket for space laser terminal CPA according to claim 1, characterized in that: The bracket has a U-shaped structure, and the solid connection area (1) includes: Mounting bosses are provided at the top of the two upper arms of the U-shaped structure for connecting the telescope; A mounting boss is provided at the bottom of the U-shaped structure for connecting the orientation motor.

3. The high-rigidity active thermal management bracket for space laser terminal CPA according to claim 1 or 2, characterized in that: The enhanced lattice structure adopts a body-centered cubic lattice, and its lattice parameters are optimized and determined with the target of maximizing the first-order natural frequency of the support and the constraint that the mass of the support does not exceed a preset value. The thermal deformation compensation lattice structure adopts a concave negative Poisson's ratio hexagonal lattice, and its lattice parameters are optimized and determined with the goal of matching the equivalent thermal expansion coefficient in the optical axis direction with the material of the telescope mounting surface.

4. The high-rigidity active thermal management bracket for space laser terminal CPA according to claim 3, characterized in that: The body-centered cubic lattice has a unit cell size of 10-20 mm, a beam diameter of 0.8-1.5 mm, and a relative density of 30%-50%.

5. The high-rigidity active thermal management bracket for space laser terminal CPA according to claim 3, characterized in that: The concave negative Poisson's ratio hexagonal lattice has a unit cell size of 10-20 mm, a beam diameter of 0.8-1.5 mm, a tilt angle of 30-60°, and an equivalent thermal expansion coefficient ≤15.0×10⁻⁶ along the optical axis. -6 / °C.

6. The high-rigidity active thermal management bracket for space laser terminal CPA according to claim 3, characterized in that: The bracket has a first-order natural frequency greater than 500Hz, a mass less than 2.0kg, and a thermal deformation difference of less than 0.0002m with the telescope mounting surface under ±50°C conditions.

7. The high-rigidity active thermal management bracket for space laser terminal CPA according to claim 1, characterized in that: The aluminum alloy powder has the following composition: Mg: 4.0-4.9wt%, Sc: 0.6-0.8wt%, Zr: 0.3-0.5wt%, Mn: 0.4-0.6wt%, with the balance being Al.

8. The high-rigidity active thermal management bracket for space laser terminal CPA according to claim 7, characterized in that: The aluminum alloy powder has a particle size distribution of 20-63 μm.

9. A method for fabricating a high-rigidity active thermal management bracket for a space laser terminal CPA as described in claim 1, characterized in that, include: (1) Using the variable density method, the layout of the solid connection area (1), the main load-bearing lattice area (2) and the thermal deformation matching lattice area (3) of the support is determined through topology optimization; (2) Partition filling of enhanced lattice and thermal deformation compensation lattice, and optimization of lattice parameters respectively; (3) Aluminum alloy powder is used to integrally form the bracket through laser powder bed melting technology; (4) Post-processing of the molded parts, including hot isostatic pressing and heat treatment; (5) The installation interface of the solid connection area (1) is finely processed.

10. The preparation method according to claim 9, characterized in that: The parameters for the hot isostatic pressing treatment are: temperature 480±10°C, pressure 1000±50 bar, and holding temperature and pressure for 1.5~3 hours; the heat treatment adopts the T6 heat treatment regime, specifically: 325±10°C, holding temperature for 3~4 hours followed by water quenching, 160±10°C, aging for 8 hours followed by air cooling.

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