【作者】 杨雯；

【导师】 吴林志； 熊健；

【作者基本信息】 哈尔滨工业大学 ， 工程力学， 2020， 博士

【摘要】 对于高超声速飞行器和可重复使用运载火箭来说,隔热、承载、维型一体化的热防护结构是保证飞行器安全飞行的重要系统。为了提高飞行器的机动性,实现大推重比和长航程,热防护结构的轻量化设计变得尤为重要;而围绕新型轻量化结构涉及的诸多热、力学问题有待进一步研究。沙漏型点阵因其优异的芯杆抗弯曲性能、面板局部抗屈曲性能和抗爆炸冲击等力学性能,成为近年来的研究热点,其内部空腔为结构多功能化、集成化提供了发展空间。基于此,本文研究了沙漏型点阵的平压性能、剪切性能和传热特性,加筋沙漏型点阵的面外压缩、面内压缩和热变形行为,以及以加筋沙漏型点阵为承载骨架的多功能结构的承载性能和热性能,为设计新型多功能一体化结构提供了参考。提出了一种拓扑强化和材料强化相结合的方法制备铝合金点阵结构,解决了薄面板点阵结构制备的瓶颈问题。推导了适合铝合金沙漏型点阵结构力学性能的理论预报公式,开展了三种不同相对密度、两种热处理状态的面外压缩实验和面内剪切实验。结果表明:强化处理可以有效提高铝合金沙漏型点阵结构的力学性能,与焊后件相比,芯子相对密度为1.72%、2.92%和4.59%的点阵结构的平压强度和剪切强度分别提升了1.1～2.06倍和0.81～1.3倍。通过有限元模拟和理论预报研究了恒定温度载荷条件下,沙漏型点阵结构的等效热导率,并与其它几种典型轻质结构进行对比。研究了芯杆厚度t_c、芯杆倾角ω和芯子高度h对结构抗热变形能力的影响。研究发现:沙漏型点阵结构抵抗热变形的能力明显优于其他几种构型,而加筋处理可以明显提升结构抵抗热变形的能力。设计并制备了三种相对密度的加筋沙漏型点阵结构,研究了该结构在压缩载荷作用下的力学行为和吸能特性。研究了非均匀升温条件下,芯杆倾角ω、芯杆厚度t_c及加筋条厚度t_g对加筋沙漏型点阵结构的热变形的影响。最后,建立了多层加筋沙漏型点阵结构的力学和热学等效模型,推导了该结构的芯子相对密度、弹性模量以及不同方向上的等效热导率。研究表明:加筋沙漏型点阵的压缩峰值分别是沙漏型点阵结构和金字塔型点阵结构的1.14倍和5.3倍。随着芯杆倾角、芯杆厚度、加筋条厚度的增加,结构的热变形减小,Y方向上对变形的抵抗能力倍最大。基于加筋沙漏型点阵结构的基本力学性能研究和传热性能研究,以飞行器典型部件-燃料储箱为研究对象,进行多功能一体化设计。为减少输入热流,满足多层温控,对结构进行分层设计。根据服役环境要求,研究管路尺寸及管路间距等因素对传热性能影响,评估结构的热控性能;通过仿真分析研究在力学载荷和热载荷条件下结构的强度、变形及热性能。研究发现:方管比圆管有利于结构的传热;对于多功能结构达到使用上限温度(140℃)所需对流换热系数来说,管路内径尺寸对其影响明显,而管路外径对其影响甚小;管路间距不超70mm时,可以将结构温差控制在10℃内,约为传统多功能结构温差的1/4。更多还原

【Abstract】 For hypersonic vehicles and reusable launch vehicles,the heat protection structure integrating heat insulation,bearing and dimension maintenance is an important system to ensure safe flight of an aircraft.To improve the maneuverability and achieve a large thrust-weight ratio and long voyage range of the vehicles,design of lightweight structures with thermal protection is particularly important,while many thermal and mechanical properties related to the novel lightweight structures need to be further explored.Due to the superior bending performance of hourglass lattice truss,panel buckling resistance and blast resistance,hourglass lattice truss sandwich structures have become one of the recent research hotpots gradually.The internal cavity in the structure opens the development space for the multifunctionalization and integration of the structure.In this thesis,the out-of-plane compression,in-plane shear,heat transfer and thermal deformation of hourglass truss-lattice sandwich panels are explored.At the same time,the mechanical and thermal properties of the multifunctional structure with grid-hourglass truss-lattice sandwich structure as its supporting framework are also studied.This multifunctional structure provides a guidance for the design of new multifunctional integrated structure.The main contents of the thesis are as follows:A novel method for manufacturing the lattice truss sandwich structures made from aluminum alloy was developed through a combination of topologicalreinforcement and material-strengthening.The method could overcome the bottleneck problem in fabricating aluminum alloy thin panel lattice structure.Making use of wire electrical discharge machining(WEDM)and vacuum brazing method,three dimensional aluminum alloy hourglass truss-lattice sandwich structures were fabricated under two heat treatments.The theoretical formulas were derived for predicting the out-of-plane compression and in-plane shear strength of the lattice truss sandwich structures.The out-of-plane compression and shear properties of the lattice truss sandwich structures under three different relative densities and two heat treatments were experimentally investigated,and the results were well agreement with those from theoretical prediction,which verified the theoretical prediction model.The study particularly showed that the strengthening treatment can effectively improve the mechanical properties of the aluminum alloy hourglass lattice structure.Compared to the as-brazed hourglass truss-lattice sandwich structures,the out-ofplane compressive strength and in-plane shear strength of the age-hardened ones with relative densities of 1.72%,2.92% and 4.59% were increased by 1.1～2.06 times and0.81～1.3 times,respectively.The heat transfer performance of hourglass lattice sandwich structure under constrant temperature loading was studied,while a series of theoretical formulas were also derived,which included the equivalent heat conductivity outside the surface and the equivalent heat conductivity inside the surface.The equivalent thermal conductivity of the hourglass lattice-truss sandwich structure was analyzed by finite element simulation and theory prediction,and the results were compared with that from typical sandwich structures.The effects of the truss thickness,the inclination angle of truss and the thickness of the core on the thermal deformation resistance of the hourglass lattice-truss sandwich structure were studied.Compared to the pyramid truss lattice sandwich structure and grid-pyramid truss-lattice sandwich structure,hourglass lattice-truss sandwich structure shows better thermal deformation resistance.In addition,the thermal deformation resistance of the grid-stiffened lattice-truss sandwich structure can be significantly improved.The grid-hourglass lattice sandwich structures with three relative densities were designed and prepared,and their mechical behavior and energy absorption characteristics under compression loading were studied.The effect of the inclination angle,thickness of lattice truss and grid-stiffener on the thermal deformation performance of hourglass lattice-truss sandwich structure under the condition of nonuniform temperature rise were also studied.The mechanical and thermal equivalent models of multi-layer grid-hourglass lattice sandwich structure were built.The formulas for core relative density,elasticity modulus,and equivalent thermal conductivity in different directions were derived,and the finite element calculation of equivalent thermal conductivity was carried out.The result shows that the gridhourglass lattice sandwich structure has the best out-of-plane compressive strength among the three structures.Meanwhile,its peak load of in-plane compression is 1.14 times and 5.3 times than that of the hourglass lattice truss sandwich structure and the pyramid lattice truss sandwich structure,respectively.With the increase of the truss inclination angle,the thickness of the lattice core and the thickness of the stiffened bar of the grid-hourglass truss lattice core,the thermal deformation of this sandwich structure decreases.The strongest resistance to thermal deformation of grid-hourglass lattice-truss sandwich structure is in Y direction.Based on the basic mechanical properties and heat transfer properties of the gridhourglass lattice sandwich structure,a multi-functional integrated design was conducted for the fuel storage tank,a typical component in an aircraft.To meet the needs of multi-layer temperature control for reducing input heat flow,the layered conceptual design of the structure was introduced.According to the requirements of service environment,the influence of the shape,size and spacing of the pipe on heat transfer performance were studied,and the thermal control performance of multifunctional structure was evaluated.The mechanical strength,deformation and thermal properties of the multi-functional structure under mechanical and thermal loads were studied by simulation analysis.The convection heat transfer coefficient meeting the upper limit temperature(140℃)of the aluminum alloy structure is closely related to the inner diameter of the pipe,while the outer diameter of the pipe has little influence on it.When the distance between pipelines is below 70 mm,the temperature difference of the multi-functional structure could be controlled to be less than 10℃,which is close to 1/4 of the temperature difference in traditional structures.更多还原